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NITRO-EXPLOSIVES

[Illustration: DANGER BUILDING SHOWING PROTECTING MOUNDS. (_See page 6._)]

NITRO-EXPLOSIVES

A PRACTICAL TREATISE

CONCERNING THE

_PROPERTIES, MANUFACTURE, AND ANALYSIS OF NITRATED SUBSTANCES, INCLUDING
THE FULMINATES, SMOKELESS POWDERS, AND CELLULOID_

BY

P. GERALD SANFORD, F.I.C., F.C.S.

_Public Analyst to the Borough of Penzance; late Consulting Chemist to the
Cotton Powder Company Limited; and formerly Resident Chemist at the
Stowmarket Works of the New Explosives Company Limited, and the Hayle
Works of the National Explosive Company Limited_

~Second Edition, Revised and Enlarged~


PREFACE.


In compiling the following treatise, my aim has been to give a brief but
thoroughly practical account of the properties, manufacture, and methods
of analysis of the various nitro-explosives now so largely used for mining
and blasting purposes and as propulsive agents; and it is believed that
the account given of the manufacture of nitro-glycerine and of the
gelatine dynamites will be found more complete than in any similar work
yet published in this country.

For many of the facts and figures contained in the chapter on Smokeless
Powders I am indebted to (amongst others) the late Mr J.D. Dougall and
Messrs A.C. Ponsonby and H.M. Chapman, F.C.S.; and for details with regard
to Roburite to Messrs H.A. Krohn and W.J. Orsman, F.I.C. To these
gentlemen my cordial thanks are due. Among the authorities which have been
consulted in the general preparation of the work may be mentioned the
_Journals_ of the Chemical Society, the Society of Chemical Industry, the
United States Naval Institute, and the Royal Artillery Institution. I have
also referred to several volumes of the periodical publication _Arms and
Explosives;_ to various papers by Sir Frederick Abel, Bart., F.R.S., and
General Wardell, R.A., on Gun-Cotton; to "Modern Artillery," by Capt.
Lloyd, R.N., and A.G. Hadcock, R.A.; to the late Colonel Cundill's
"Dictionary of Explosives"; as well as to the works of Messrs Eissler,
Berthelot, and others.

The illustrations have been prepared chiefly from my own drawings. A few,
however, have been taken (by permission) from the pages of _Arms and
Explosives_, or from other sources which are acknowledged in the text.

P.G.S.

THE LABORATORY,

20 CULLUM STREET, E.C.

_May 1896._



PREFACE TO THE SECOND EDITION.


In the preparation of the Second Edition of this work, I have chiefly made
use of the current technical journals, especially of the _Journal of the
Society of Chemical Industry_. The source of my information has in every
case been acknowledged.

I am also indebted to several manufacturers of explosives for information
respecting their special products--among others the New Explosives Company
Ltd.; Messrs Curtis's and Harvey Ltd.; The Schultze Gunpowder Company
Ltd.; and Mr W.D. Borland, F.I.C., of the E.C. Powder Company Ltd.

To my friend Mr A. Stanley Fox, F.C.S., of Faversham, my best thanks are
also due for his help in many departments, and his kindness in pointing
out several references.

The chapter on Smokeless Powders has been considerably enlarged and (as
far as possible) brought up to date; but it has not always been possible
to give the process of manufacture or even the composition, as these
details have not, in several cases, been made public.

P. GERALD SANFORD.

LONDON, _June 1906._




TABLE OF CONTENTS.

CHAPTER I.--INTRODUCTION.

The Nitro-Explosives--Substances that have been Nitrated--The Danger Area--
Systems of Professors Lodge, Zenger, and Melsens for the Protection of
Buildings from Lightning, &c.

CHAPTER II.--NITRO-GLYCERINE.

Properties of Nitro-Glycerine--Manufacture--Nitration--Separation--Washing
and Filtering--Drying, Storing, &c.--The Waste Acids--Their Treatment--
Nitric Acid Plants

CHAPTER III.--NITRO-CELLULOSE, &C.

Cellulose Properties--Discovery of Gun-Cotton--Properties of Gun-Cotton--
Varieties of Soluble and Insoluble Gun-Cottons--Manufacture of Gun-Cotton--
Dipping and SteepingWhirling Out the Acid--Washing, Boiling, Pulping,
Compressing--The Waltham Abbey Process--Le Bouchet Process--Granulation of
Gun-Cotton--Collodion-Cotton--Manufacture--Acid Mixture Used--Cotton Used,
&c.--Nitrated Gun-Cotton--Tonite--Dangers in Manufacture of Gun-Cotton--
Trench's Fire-Extinguishing Compound--Uses of Collodion-Cotton--Celluloid--
Manufacture, &c.--Nitro-Starch, Nitro-Jute, and Nitro-Mannite

CHAPTER IV.--DYNAMITE.

Kieselguhr Dynamite--Classification of Dynamites--Properties and
Efficiency of Ordinary Dynamite--Other forms of Dynamite--Gelatine and
Gelatine Dynamites, Suitable Gun-Cotton for, and Treatment of--Other
Materials Used--Composition of Gelignite--Blasting Gelatine--Gelatine
Dynamite--Absorbing Materials--Wood Pulp--Potassium Nitrate, &c.--
Manufacture, &c.--Apparatus Used--The Properties of the Gelatine Compounds

CHAPTER V.--NITRO-BENZOL, ROBURITE, BELLITE, PICRIC ACID, &c.

Explosives derived from Benzene--Toluene and Nitro-Benzene--Di- and
Tri-nitro-Benzene--Roburite: Properties and Manufacture--Bellite:
Properties, &c.--Securite--Tonite No. 3.--Nitro-Toluene--
Nitro-Naphthalene--Ammonite--Sprengel's Explosives--Picric Acid--
Picrates--Picric Powders--Melinite--Abel's Mixture--Brugère's Powders--
The Fulminates--Composition, Formula, Preparation, Danger of, &c.--
Detonators: Sizes, Composition, Manufacture--Fuses, &c.

THE FULMINATES.

Composition, Formula, Preparation, Danger of, &c.--Detonators: Sizes,
Composition, Manufacture--Fuses, &c.

CHAPTER VI.--SMOKELESS POWDERS IN GENERAL.

Cordite--Axite--Ballistite--U.S. Naval Powder--Schultze's E.C. Powder--
Indurite--Vielle Poudre--Walsrode and Cooppal Powders--Amberite--
Troisdorf--B.N. Powder--Wetterin--Normal Powder--Maximite--Picric Acid
Powders, &c. &c.

CHAPTER VII.--ANALYSIS OF EXPLOSIVES.

Kieselguhr Dynamite--Gelatine Compounds--Tonite--Cordite--Vaseline--
Acetone--Scheme for Analysis of Explosives--Nitro-Cotton--Solubility Test--
Non-Nitrated Cotton--Alkalinity--Ash and Inorganic Matter--Determination
of Nitrogen--Lungé, Champion and Pellet's, Schultze-Tieman, and Kjeldahl's
Methods--Celluloid--Picric Acid and Picrates--Resinous and Tarry Matters--
Sulphuric Acid and Hydrochloric Acid and Oxalic Acid--Nitric Acid--
Inorganic Impurities--General Impurities and Adulterations--Potassium
Picrate, &c.--Picrates of the Alkaloids--Analysis of Glycerine--Residue--
Silver Test--Nitration--Total Acid Equivalent--Neutrality--Free Fatty
Acids--Combined Fatty Acids--Impurities--Oleic Acid--Sodium Chloride--
Determination of Glycerine--Waste Acids--Sodium Nitrate--Mercury
Fulminate--Cap Composition--Table for Correction of Volumes of Gases, for
Temperature and Pressure

CHAPTER VIII.--FIRING POINT OF EXPLOSIVES, HEAT TESTS, &C.

Horsley's Apparatus--Table of Firing Points--The Government Heat Test
Apparatus, &c., for Dynamites, Nitro-Glycerine, Nitro-Cotton, and
Smokeless Powders--Guttmann's Heat Test--Liquefaction and Exudation Tests--
Page's Regulator for Heat Test Apparatus--Specific Gravities of
Explosives--Will's Test for Nitro-Cellulose--Table of Temperature of
Detonation, Sensitiveness, &c.

CHAPTER IX.--THE DETERMINATION OF THE RELATIVE STRENGTH OF EXPLOSIVES.

Effectiveness of an Explosive--High and Low Explosives--Theoretical
Efficiency--M.M. Roux and Sarrau's Results--Abel and Noble's--Nobel's
Ballistic Test--The Mortar--Pressure or Crusher Gauge--Calculation Volume
of Gas Evolved, &c.--Lead Cylinders--The Foot-Pounds Machine--Noble's
Pressure Gauge--Lieut. Walke's Results--Calculation of Pressure Developed
by Dynamite and Gun-Cotton--McNab's and Ristori's Results of Heat
Developed by the Explosion of Various Explosives--Composition of some of
the Explosives in Common Use for Blasting, &c.

INDEX



LIST OF ILLUSTRATIONS.

FRONTISPIECE--Danger Building showing Protecting Mounds.
 1. Section of Nitro-Glycerine Conduit
 2. Melsens System of Lightning Conductors
 3. French System
 4_a_ & 4_b_. English Government System
 5. Upper Portion of Nitrator for Nitro-Glycerine
 6. Small Nitrator
 7. Nathan's Nitrator
 8. Nitro-Glycerine Separator
 9. Nitro-Glycerine Filtering Apparatus
10. Cotton-Waste Drier
11. Dipping Tank
12. Cooling Pits
13. Steeping Pot for Gun-Cotton
14. Hydro-Extractor or Centrifugal Drier
15_a_ & 15_b_. Gun-Cotton Beater
16_a_. Poacher for Pulping Gun-Cotton
16_b_. Plan of same
16_c_. Another form of Poacher
17 & 18. Compressed Gun-Cotton
19. Hydraulic Press
20. Thomson's Apparatus--Elevation
21. Elevation Plan
22. Trench's Safety Cartridge
23. Vessel used in Nitrating Paper
24. Cage ditto--White & Schupphaus' Apparatus
25.  Do.                do.            do.
26 & 27. Nitrating Pot for Celluloid
28 & 29. Plunge Tank in Plan and Section
30. Messrs Werner, Pfleiderer & Perkins' Mixing Machine
31. M. 'Roberts' Mixing Machine for Blasting Gelatine
32. Plan of same
33. Cartridge Machine for Gelatines
34. Cartridge fitted with Fuse and Detonator
35. Gun-Cotton Primer
36. Electric Firing Apparatus
37. Metal Drum for Winding Cordite
38. Ten-Stranding
39. Curve showing relation between Pressures of Cordite and Black Powder,
      by Professor Vivian Lewes
40. Marshall's Apparatus for Moisture in Cordite
41. Lungé's Nitrometer
42. Modified   do.
43. Horn's Nitrometer
44. Schultze-Tieman Apparatus for Determination of Nitrogen in Gun-Cotton
45. Decomposition Flask for Schultze-Tieman Method
46. Abel's Heat Test Apparatus
47. Apparatus for Separation of Nitro-Glycerine from Dynamite
48. Test Tube arranged for Heat Test
49. Page's Regulator
50.       Do.  showing Bye-Pass and Cut-off Arrangement
51. Will's Apparatus
52 & 53. Curves obtained
54. Dynamite Mortar
55. Quinan's Pressure Gauge
56. Steel Punch and Lead Cylinder for Use with Pressure Gauge
57. Micrometer Calipers for Measuring Thickness of Lead Cylinders
58. Section of Lead Cylinders before and after Explosion
59. Noble's Pressure Gauge
60. Crusher Gauge




NITRO-EXPLOSIVES.


CHAPTER I.

_INTRODUCTORY._

The Nitro-Explosives--Substances that have been Nitrated--The Danger Area--
Systems of Professors Lodge, Zenger, and Melsens for the Protection of
Buildings from Lightning, &c.


The manufacture of the various nitro-explosives has made great advances
during late years, and the various forms of nitro-compounds are gradually
replacing the older forms of explosives, both for blasting purposes and
also for propulsive agents, under the form of smokeless powders. The
nitro-explosives belong to the so-called High Explosives, and may be
defined as any chemical compound possessed of explosive properties, or
capable of combining with metals to form an explosive compound, which is
produced by the chemical action of nitric acid, either alone or mixed with
sulphuric acid, upon any carbonaceous substance, whether such compound is
mechanically mixed with other substances or not.[A]

[Footnote A: Definition given in Order of Council, No. 1, Explosives Act,
1875.]

The number of compounds and mixtures included under this definition is
very large, and they are of very different chemical composition. Among the
substances that have been nitrated are:--Cellulose, under various forms,
e.g., cotton, lignin, &c.; glycerine, benzene, starch, jute, sugar,
phenol, wood, straw, and even such substances as treacle and horse-dung.
Some of these are not made upon the large scale, others are but little
used. Those of most importance are nitro-glycerine and nitro-cellulose.
The former enters into the composition of all dynamites, and several
smokeless powders; and the second includes gun-cotton, collodion-cotton,
nitrated wood, and the majority of the smokeless powders, which consist
generally of nitro-cotton, nitro-lignin, nitro-jute, &c. &c., together
with metallic nitrates, or nitro-glycerine.

The nitro-explosives consist generally of some organic substance in which
the NO_{2} group, known as nitryl, has been substituted in place of
hydrogen.

Thus in glycerine,

          |OH
C_{3}H_{5}|OH,
          |OH

which is a tri-hydric alcohol, and which occurs very widely distributed as
the alcoholic or basic constituent of fats, the hydrogen atoms are
replaced by the NO_{2} group, to form the highly explosive compound,
nitro-glycerine. If one atom only is thus displaced, the mono-nitrate is
formed thus,

          |ONO_{2}
C_{3}H_{5}|OH;
          |OH

and if the three atoms are displaced, C_{3}H_{5}(ONO_{2})_{3}, or the tri-
nitrate, is formed, which is commercial nitro-glycerine.

Another class, the nitro-celluloses, are formed from cellulose,
C_{6}H_{10}O_{5}, which forms the groundwork of all vegetable tissues.
Cellulose has some of the properties of the alcohols, and forms ethereal
salts when treated with nitric and sulphuric acids. The hexa-nitrate, or
gun-cotton, has the formula, C_{12}H_{14}O_{4}(ONO_{2})_{6}; and
collodion-cotton, pyroxylin, &c., form the lower nitrates, i.e., the
tetra- and penta-nitrates. These last are soluble in various solvents,
such as ether-alcohol and nitro-glycerine, in which the hexa-nitrate is
insoluble. They all dissolve, however, in acetone and acetic ether.

The solution of the soluble varieties in ether-alcohol is known as
collodion, which finds many applications in the arts. The hydrocarbon
benzene, C_{6}H_{6}, prepared from the light oil obtained from coal-tar,
when nitrated forms nitro-benzenes, such as mono-nitro-benzene,
C_{6}H_{5}NO_{2}, and di-nitro-benzene, C_{6}H_{4}(NO_{2})_{2}, in which
one and two atoms are replaced by the NO_{2} group. The latter of these
compounds is used as an explosive, and enters into the composition of such
well-known explosives as roburite, &c. The presence of nitro groups in a
substance increases the difficulty of further nitration, and in any case
not more than three nitro groups can be introduced into an aromatic
compound, or the phenols. All aromatic compounds with the general formula,
C_{6}H_{4}X_{2}, give, however, three series. They are called ortho, meta,
or para compounds, depending upon the position of NO_{2} groups
introduced.

Certain regularities have been observed in the formation of nitro-
compounds. If, for example, a substance contains alkyl or hydroxyl groups,
large quantities of the para compound are obtained, and very little of the
ortho. The substitution takes place, however, almost entirely in the meta
position, if a nitro, carboxyl, or aldehyde group be present. Ordinary
phenol, C_{6}H_{5}.OH, gives para- and ortho-nitro-phenol; toluene gives
para- and ortho-nitro-toluene; but nitro-benzene forms meta-di-nitro-
benzene and benzoic acid, meta-nitro-benzoic acid.[A]

[Footnote A: "Organic Chemistry," Prof. Hjelt. Translated by J.B. Tingle,
Ph.D.]

If the graphic formula of benzene be represented thus (No. 1), then the
positions 1 and 2 represent the ortho, 1 and 3 the meta, and 1 and 4 the
para compounds. When the body phenol, C_{6}H_{5}.OH, is nitrated, a
compound is formed known as tri-nitro-phenol, or picric acid,
C_{6}H_{2}(NO_{2})_{3}OH, which is used very extensively as an explosive,
both as picric acid and in the form of picrates. Another nitro body that
is used as an explosive is nitro-naphthalene, C_{10}H_{6}(NO_{2})_{2}, in
roburite, securite, and other explosives of this class. The hexa-nitro-
mannite, C_{6}H_{8}(ONO_{2})_{6}, is formed

[Illustration: No. 1]

[Illustration: META-DINITRO-BENZENE No.2]

by treating a substance known as mannite, C_{6}H_{8}(OH)_{6}, an alcohol
formed by the lactic acid fermentation of sugar and closely related to the
sugars, with nitric and sulphuric acids. It is a solid substance, and very
explosive; it contains 18.58 per cent. of nitrogen.

Nitro-starch has also been used for the manufacture of an explosive.
Muhlhauer has described (_Ding. Poly. Jour._, 73, 137-143) three nitric
ethers of starch, the tetra-nitro-starch, C_{12}H_{16}O_{6}(ONO_{2})_{4},
the penta- and hexa-nitro-starch. They are formed by acting upon potato
starch dried at 100° C. with a mixture of nitric and sulphuric acids at a
temperature of 20° to 25° C. Rice starch has also been used in its
production. Muhlhauer proposes to use this body as a smokeless powder, and
to nitrate it with the spent mixed acids from the manufacture of nitro-
glycerine. This substance contains from 10.96 to 11.09 per cent. of
nitrogen. It is a white substance, very stable and soluble even in cold
nitro-glycerine.

The explosive bodies formed by the nitration of jute have been studied by
Messrs Cross and Bevan. and also by Mühlhäuer. The former chemists give
jute the formula C_{12}H_{18}O_{9}, and believe that its conversion into a
nitro-compound takes place according to the equation--

C_{12}H_{18}O_{9} + 3HNO_{3} = 3H_{2}O + C_{12}H_{15}O_(6}(NO_{3})_{3}.

This is equivalent to a gain in weight of 44 per cent. for the tri-
nitrate, and 58 per cent. for the tetra-nitrate. The formation of the
tetra-nitrate appears to be the limit of nitration of jute fibre. Messrs
Cross and Bevan say, "In other words, if we represent the ligno-cellulose
molecule by a C_{12} formula, it will contain four hydroxyl (OH) groups,
or two less than cellulose similarly represented." It contains 11.5 per
cent. of nitrogen. The jute nitrates resemble those of cellulose, and are
in all essential points nitrates of ligno-cellulose.

Nitro-jute is used in the composition of the well-known Cooppal Smokeless
Powders. Cross and Bevan are of opinion that there is no very obvious
advantage in the use of lignified textile fibres as raw materials for
explosive nitrates, seeing that a number of raw materials containing
cellulose (chiefly as cotton) can be obtained at from £10 to £25 a ton,
and yield also 150 to 170 per cent. of explosive material when nitrated
(whereas jute only gives 154.4 per cent.), and are in many ways superior
to the products obtained from jute. Nitro-lignin, or nitrated wood, is,
however, largely used in the composition of a good many of the smokeless
powders, such as Schultze's, the Smokeless Powder Co.'s products, and
others.

~The Danger Area.~--That portion of the works that is devoted to the
actual manufacture or mixing of explosive material is generally designated
by the term "danger area," and the buildings erected upon it are spoken of
as "danger buildings." The best material of which to construct these
buildings is of wood, as in the event of an explosion they will offer less
resistance, and will cause much less danger than brick or stone buildings.
When an explosion of nitro-glycerine or dynamite occurs in one of these
buildings, the sides are generally blown out, and the roof is raised some
considerable height, and finally descends upon the blown-out sides. If, on
the other hand, the same explosion had occurred in a strong brick or stone
building, the walls of which would offer a much larger resistance, large
pieces of brickwork would probably have been thrown for a considerable
distance, and have caused serious damage to surrounding buildings.

It is also a very good plan to surround all danger buildings with mounds
of sand or earth, which should be covered with turf, and of such a height
as to be above the roof of the buildings that they are intended to protect
(see frontispiece).[A] These mounds are of great value in confining the
force of the explosion, and the sides of the buildings being thrown
against them are prevented from travelling any distance. In gunpowder
works it is not unusual to surround the danger buildings with trees or
dense underwood instead of mounds. This would be of no use in checking the
force of explosion of the high explosives, but has been found a very
useful precaution in the case of gunpowder.

[Footnote A: At the Baelen Factory, Belgium, the danger buildings are
erected on a novel plan. They are circular in ground plan and lighted
entirely from the roof by means of a patent glass having wire-netting in
it, and which it is claimed will not let a splinter fall, even if badly
cracked. The mounds are then erected right up against the walls of the
building, exceeding them in height by several metres. For this method of
construction it is claimed that the force exerted by an explosion will
expand itself in a vertical direction ("Report on Visits to Certain
Explosive Factories," H.M. Inspectors, 1905).]

In Great Britain it is necessary that all danger buildings should be a
specified distance apart; a license also must be obtained. The application
for a license must give a plan (drawn to scale) of the proposed factory or
magazine, and the site, its boundaries, and surroundings, and distance the
building will be from any other buildings or works, &c., also the
character, and construction of all the mounds, and nature of the processes
to be carried on in the factory or building.[A]

[Footnote A: Explosives Act, 38 Vict. ch. 17.]

[Illustration: FIG. 1.--SECTION OF NITRO-GLYCERINE CONDUIT. _a_, lid; _b_,
lead lining; _c_, cinders.]

The selection of a site for the danger area requires some attention. The
purpose for which it is required, that is, the kind of explosive that it
is intended to manufacture, must be taken into consideration. A perfectly
level piece of ground might probably be quite suitable for the purpose of
erecting a factory for the manufacture of gun-cotton or gunpowder, and
such materials, but would be more or less unsuitable for the manufacture
of nitro-glycerine, where a number of buildings are required to be upon
different levels, in order to allow of the flow of the liquid nitro-
glycerine from one building to another through a system of conduits. These
conduits (Fig. 1), which are generally made of wood and lined with lead,
the space between the woodwork and the lead lining, which is generally
some 4 or 5 inches, being filled with cinders, connect the various
buildings, and should slope gently from one to the other. It is also
desirable that, as far as possible, they should be protected by earth-work
banks, in the same way as the danger buildings themselves. They should
also be provided with covers, which should be whitewashed in hot weather.

A great deal of attention should be given to these conduits, and they
should be very frequently inspected. Whenever it is found that a portion
of the lead lining requires repairing, before cutting away the lead it
should be very carefully washed, for several feet on either side of the
portion that it is intended to remove, with a solution of caustic soda or
potash dissolved in methylated spirit and water, and afterwards with water
alone. This decomposes the nitro-glycerine forming glycerine and potassium
nitrate. It will be found that the mixed acids attack the lead rather
quickly, forming sulphate and nitrate of lead, but chiefly the former. It
is on this account that it has been proposed to use pipes made of
guttapercha, but the great drawback to their use is that in the case of
anything occurring inside the pipes, such as the freezing of the nitro-
glycerine in winter, it is more difficult to find it out, and the
condition of the inside cannot be seen, whereas in the case of wooden
conduits it is an easy matter to lift the lids along the whole length of
the conduit.

The buildings which require to be connected by conduits are of course
those concerned with the manufacture of nitro-glycerine. These buildings
are--(1) The nitrating house; (2) the separating house; (3) the filter
house; (4) the secondary separator; (5) the deposit of washings; (6) the
settling or precipitation house; and each of these buildings must be on a
level lower than the preceding one, in order that the nitro-glycerine or
acids may flow easily from one building to the next. These buildings are,
as far as possible, best placed together, and away from the other danger
buildings, such as the cartridge huts and dynamite mixing houses, but this
is not essential.

All danger buildings should be protected by a lightning conductor, or
covered with barbed wire, as suggested by Professor Sir Oliver J. Lodge,
F.R.S., Professors Zenger, of Prague, and Melsens, of Brussels, and
everything possible should be done to keep them as cool as possible in the
summer. With this object they should be made double, and the intervening
space filled with cinders. The roof also should be kept whitewashed, and
the windows painted over thinly with white paint. A thermometer should be
suspended in every house. It is very essential that the floors of all
these buildings should be washed every day before the work-people leave.
In case any nitro-glycerine is spilt upon the floors, after sponging it up
as far as possible, the floor should be washed with an alcoholic solution
of soda or potash to decompose the nitro-glycerine, which it does
according to the equation[A]--

C_{3}H_{5}(NO_{3})_{3} + 3KOH = C_{3}H_{8}O_{3} + 3KNO_{3}.

[Footnote A: See also Berthelot, _Comptes Rendus_, 1900, 131[12], 519-
521.]

Every one employed in the buildings should wear list or sewn leather
shoes, which of course must be worn in the buildings only. The various
houses should be connected by paths laid with cinders, or boarded with
planks, and any loose sand about the site of the works should be covered
over with turf or cinders, to prevent its blowing about and getting into
the buildings. It is also of importance that stand pipes should be placed
about the works with a good pressure of water, the necessary hose being
kept in certain known places where they can be at once got at in the case
of fire, such as the danger area laboratory, the foreman's office, &c. It
is also desirable that the above precautions against fire should be tested
once a week. With regard to the heating of the various buildings in the
winter, steam pipes only should be used, and should be brought from a
boiler-house outside the danger area, and should be covered with
kieselguhr or fossil meal and tarred canvas. These pipes may be supported
upon poles. A stove of some kind should be placed in the corner of each
building, but it must be entirely covered in with woodwork, and as small a
length of steam pipes should be within the building as possible.

In the case of a factory where nitro-glycerine and dynamite are
manufactured, it is necessary that the work-people should wear different
clothes upon the danger area than usual, as they are apt to become
impregnated with nitro-glycerine, and thus not very desirable or safe to
wear outside the works. It is also necessary that these clothes should not
contain any pockets, as this lessens the chance of matches or steel
implements being taken upon the danger area. Changing houses, one for the
men, and another for the girls, should also be provided. The tools used
upon the danger area should, whenever the building is in use, or contains
explosives, be made of phosphor bronze or brass, and brass nails or wooden
pegs should be used in the construction of all the buildings.

[Illustration: FIG. 2.--MELSENS SYSTEM OF LIGHTNING CONDUCTORS.]

~Lightning Conductors.~--The Explosive Substances Act, 38 Vict. ch. 17,
clause 10, says, "Every factory magazine and expense magazine in a
factory, and every danger building in a magazine, shall have attached
thereto a sufficient lightning conductor, unless by reason of the
construction by excavation or the position of such magazine or building,
or otherwise, the Secretary of State considers a conductor unnecessary,
and every danger building in a factory shall, if so required by the
Secretary of State, have attached thereto a sufficient lightning
conductor."

The exact form of lightning conductor most suitable for explosive works
and buildings has not yet been definitely settled. Lightning-rod engineers
favour what is known as the Melsens system, due to Professor Melsens, of
Brussels, and Professor Zenger, of Prague, but first suggested by the late
Professor Clerk-Maxwell. In a paper read before the British Association,
Clerk-Maxwell proposed to protect powder-magazines from the effects of
lightning by completely surrounding or encasing them with sheet metal, or
a cage of metallic conductors. There were, however, several objections to
his system as he left it.

Professor Melsens[A] has, while using the idea, made several important
alterations. He has multiplied the terminals, the conductors, and the
earth-connections. His terminals are very numerous, and assume the form of
an aigrette or brush with five or seven points, the central point being a
little higher than the rest, which form with it an angle of 45°. He
employs for the most part galvanised-iron wire. He places all metallic
bodies, if they are of any considerable size, in communication with the
conducting system in such a manner as to form closed metallic circuits.
His system is illustrated in Fig. 2, taken from _Arms and Explosives_.

[Footnote A: Belgian Academy of Science.]

This system is a near approximation to J.C. Maxwell's cage. The system was
really designed for the protection of powder-magazines or store buildings
placed in very exposed situations. Zenger's system is identical with that
of Melsens, and has been extensively tried by the Austrian military
authorities, and Colonel Hess has reported upon the absolute safety of the
system.

[Illustration: Fig. 3.--FRENCH SYSTEM OF LIGHTNING CONDUCTORS.]

The French system of protecting powder-magazines is shown in Fig. 3, where
there are no brush terminals or aigrettes. The French military authorities
also protect magazines by erecting two or more lightning-rods on poles of
sufficient height placed close to, but not touching, the walls of the
magazine. These conductors are joined below the foundations and earthed as
usual.

In the instructions issued by the Government, it is stated that the
lightning-rods placed upon powder-mills should be of such a height, and so
situated, that no danger is incurred in igniting the powder-dust in the
air by the lightning discharge at the pointed rod. In such a case a fork
or aigrette of five or more points should invariably be used in place of a
single point.

[Illustration: FIG. 4_a_.--GOVERNMENT SYSTEM OF LIGHTNING CONDUCTORS FOR
LARGE BUILDINGS.]

[Illustration: FIG. 4_b_.--GOVERNMENT SYSTEM OF LIGHTNING CONDUCTORS FOR
SMALL BUILDINGS.]

In Fig. 4 (_a_ and _b_) is shown the Government method for protecting
buildings in which explosives are made or stored. Multiple points or
aigrettes would be better. Lord Kelvin and Professor Melsens favour
points, and it is generally admitted that lightning does not strike
buildings at a single point, but rather in a sheet; hence, in such cases,
or in the event of the globular form being assumed by the lightning, the
aigrette will constitute a much more effective protection than a single
point. As to the spacing of conductors, they may, even on the most
important buildings, be spaced at intervals of 50 feet. There will then be
no point on the building more than 25 feet from the conductor. This
"25-feet rule" can be adhered to with advantage in all overground buildings
for explosives.

Underground magazines should, whenever possible, also be protected,
because, although less exposed than overground buildings, they frequently
contain explosives packed in metal cases, and hence would present a line
of smaller electrical resistance than the surrounding earth would offer to
the lightning. The conductor should be arranged on the same system as for
overground buildings, but be applied to the surface of the ground over the
magazines.

In all situations where several conductors are joined in one system, the
vertical conductors should be connected both at the top and near the
ground line. The angles and the prominent portions of a building being the
most liable to be struck, the conductors should be carried over and along
these projections, and therefore along the ridges of the roof. The
conductors should be connected to any outside metal on the roofs and
walls, and specially to the foot of rain-water pipes.

All the lightning conductors should be periodically tested, to see that
they are in working condition, at least every three months, according to
Mr Richard Anderson. The object of the test is to determine the resistance
of the earth-connection, and to localise any defective joints or parts in
the conductors. The best system of testing the conductors is to balance
the resistance of each of the earths against the remainder of the system,
from which the state of the earths may be inferred with sufficient
accuracy for all practical purposes.

Captain Bucknill, R.E., has designed an instrument to test resistance
which is based on the Post Office pattern resistance coil, and is capable
of testing to approximate accuracy up to 200 ohms, and to measure roughly
up to 2,000 ohms. Mr R. Anderson's apparatus is also very handy,
consisting of a case containing three Leclanché cells, and a galvanometer
with a "tangent" scale and certain standard resistances. Some useful
articles on the protection of buildings from lightning will be found in
_Arms and Explosives_, July, August, and September 1892, and by Mr
Anderson, Brit. Assoc., 1878-80.

~Nitro-Glycerine.~--One of the most powerful of modern explosive agents is
nitro-glycerine. It is the explosive contained in dynamite, and forms the
greater part of the various forms of blasting gelatines, such as gelatine
dynamite and gelignite, both of which substances consist of a mixture of
gun-cotton dissolved in nitro-glycerine, with the addition of varying
proportions of wood-pulp and saltpetre, the latter substances acting as
absorbing materials for the viscid gelatine. Nitro-glycerine is also
largely used in the manufacture of smokeless powders, such as cordite,
ballistite, and several others.

Nitro-glycerol, or glycerol tri-nitrate, was discovered by Sobrero in the
year 1847. In a letter written to M. Pelouse, he says, "when glycerol is
poured into a mixture of sulphuric acid of a specific gravity of 1.84, and
of nitric acid of a gravity of 1.5, which has been cooled by a freezing
mixture, that an oily liquid is formed." This liquid is nitro-glycerol, or
nitro-glycerine, which for some years found no important use in the arts,
until the year 1863, when Alfred Nobel first started a factory in
Stockholm for its manufacture upon a large scale; but on account of some
serious accidents taking place, its use did not become general.

It was not until Nobel conceived the idea (in 1866) of absorbing the
liquid in some absorbent earth, and thus forming the material that is now
known as dynamite, that the use of nitro-glycerine as an explosive became
general.

Among those who improved the manufacture of nitro-glycerine was Mowbray,
who, by using pure glycerine and nitric acid free from nitrous acid, made
very great advances in the manufacture. Mowbray was probably the first to
use compressed air for the purpose of keeping the liquids well agitated
during the process of nitration, which he conducted in earthenware pots,
each containing a charge of 17 lbs. of the mixed acids and 2 lbs. of
glycerol.

A few years later (1872), MM. Boutnny and Faucher, of Vonges,[A] proposed
to prepare nitro-glycerine by mixing the sulphuric acid with the
glycerine, thus forming a sulpho-glyceric acid, which was afterwards mixed
with a mixture of nitric and sulphuric acids. They claimed for this method
of procedure that the final temperature is much lower. The two mixtures
are mixed in the proportions--Glycerine, 100; nitric acid, 280; and
sulphuric acid, 600. They state that the rise of temperature upon mixing
is limited from 10° to 15° C.; but this method requires a period of
twenty-four hours to complete the nitration, which, considering the danger
of keeping the nitro-glycerine in contact with the mixed acids for so
long, probably more than compensates for the somewhat doubtful advantage
of being able to perform the nitration at such a low temperature. The
Boutnny process was in operation for some time at Pembrey Burrows in
Wales, but after a serious explosion the process was abandoned.

[Footnote A: _Comptes Rendus_, 75; and Desortiaux, "Traité sur la Poudre,"
684-686.]

Nitro-glycerine is now generally made by adding the glycerine to a mixture
of sulphuric and nitric acids. The sulphuric acid, however, takes no part
in the reaction, but is absolutely necessary to combine with the water
that is formed by the decomposition, and thus to keep up the strength of
the nitric acid, otherwise lower nitrates of glycerine would be formed
that are soluble in water, and which would be lost in the subsequent
process of washing to which the nitro-compound is subjected, in order to
remove the excess of acids, the retention of which in the nitro-glycerol
is very dangerous. Nitro-glycerol, which was formerly considered to be a
nitro-substitution compound of glycerol, was thought to be formed thus--

C_{3}H_{8}O_{3} + 3HNO_{3} = C{3}H_{5}(NO_{2})_{3}O_{3} + 3H_{2}O;

but more recent researches rather point to its being regarded as a nitric
ether of glycerol, or glycerine, and to its being formed thus--

C_{3}H_{8}O_{3} + 3 HNO_{3} = C{3}H_{5}(NO_{3})_{3} + 3H_{2}O.
             92                   227

                                                          |OH
The formula of glycerine is C_{3}H_{8}O_{8}, or C_{3}H_{5}|OH
                                                          |OH

                                                     |ONO_{2}
and that of the mono-nitrate of glycerine, C_{3}H_{5}|OH
                                                     |OH

                                                       |ONO_{2}
and of the tri-nitrate or (nitro-glycerine), C_{3}H_{5}|ONO_{2}
                                                       |ONO_{2}

that is, the three hydrogens of the semi-molecules of hydroxyl in the
glycerine have been replaced by the NO_{2} group.

In the manufacture upon the large scale, a mixture of three parts by
weight of nitric acid and five parts of sulphuric acid are used. From the
above equation it will be seen that every 1 lb. of glycerol should give
2.47 lbs. of nitro-glycerol ((227+1)/92 = 2.47), but in practice the yield
is only about 2 lbs. to 2.22, the loss being accounted for by the
unavoidable formation of some of the lower nitrate, which dissolves in
water, and is thus washed away, and partly perhaps to the presence of a
little water (or other non-nitrable matter) in the glycerine, but chiefly
to the former, which is due to the acids having become too weak.




CHAPTER II.

_MANUFACTURE OF NITRO-GLYCERINE._

Properties of Nitro-Glycerine--Manufacture of Nitro-Glycerine--Nitration--
The Nathan Nitrator--Separation--Filtering and Washing--The Waste Acids--
Treatment of the Waste Acid from the Manufacture of Nitro-Glycerine and
Gun-Cotton.


~Properties of Nitro-Glycerine.~--Nitro-glycerol is a heavy oily liquid of
specific gravity 1.6 at 15° C., and when quite pure is colourless. The
commercial product is a pale straw yellow, but varies much according to
the purity of the materials used in its manufacture. It is insoluble in
water, crystallises at 10.5° C., but different commercial samples behave
very differently in this respect, and minute impurities prevent or delay
crystallisation. Solid nitro-glycerol[A] melts at about 12° C., but
requires to be exposed to this temperature for some time before melting.
The specific gravity of the solid form is 1.735 at +10° C.; it contracts
one-twelfth of its volume in solidifying. Beckerheim[B] gives the specific
heat as 0.4248 between the temperatures of 9.5° and 9.8° C., and L. de
Bruyn gives the boiling point as above 200°.

[Footnote A: Di-nitro-mono chlorhydrin, when added to nitro-glycerine up
to 20 per cent., is said to prevent its freezing.]

[Footnote B: _Isb., Chem. Tech._, 22, 481-487. 1876.]

Nitro-glycerine has a sweet taste, and causes great depression and
vertigo. It is soluble in ether, chloroform, benzene, glacial acetic acid,
and nitro-benzene, in 1.75 part of methylated spirit, very nearly
insoluble in water, and practically insoluble in carbon bisulphide. Its
formula is C_{3}H_{5}(NO_{3})_{3}, and molecular weight 227. When pure, it
may be kept any length of time without decomposition. Berthelot kept a
sample for ten years, and Mr G. M'Roberts, of the Ardeer Factory, for nine
years, without their showing signs of decomposition; but if it should
contain the smallest trace of free acid, decomposition is certain to be
started before long. This will generally show itself by the formation of
little green spots in the gelatine compounds, or a green ring upon the
surface of liquid nitro-glycerine. Sunlight will often cause it to
explode; in fact, a bucket containing some water that had been used to
wash nitro-glycerine, and had been left standing in the sun, has in our
experience been known to explode with considerable force. Nitro-glycerine
when pure is quite stable at ordinary temperatures, and samples have been
kept for years without any trace of decomposition. It is very susceptible
to heat, and even when quite pure will not stand a temperature of 100° C.
for a longer period than a few hours, without undergoing decomposition. Up
to a temperature of 45° C., however, properly made and purified nitro-
glycerine will remain unchanged almost indefinitely. The percentage
composition of nitroglycerine is as follows:--

               Found.  Theory for C_{3}H_{5}(N0_{2})_{3}.

Carbon          15.62    15.86 per cent.
Hydrogen         2.40     2.20     "
Nitrogen        17.90    18.50     "
Oxygen           ...     63.44     "

The above analysis is by Beckerheim. Sauer and Adou give the nitrogen as
18.35 to 10.54 per cent. by Dumas' method; but I have never found any
difficulty in obtaining percentages as high as 18.46 by the use of Lunge's
nitrometer. The decomposition products by explosion are shown by the
following equation--

 2C_{3}H_{5}(NO_{3})_{3} = 6CO_{2} + 5H_{2}O + 6N + O;

that is, it contains an excess of 3.52 per cent. of oxygen above that
required for complete combustion; 100 grms. would be converted into--

Carbonic Acid (CO_{2}) 58.15 per cent.
Water                  19.83     "
Oxygen                  3.52 per cent.
Nitrogen               18.50     "

The volume of gases produced at 0° and 760 mm., calculated from the above,
is 714 litres per kilo, the water being taken as gaseous. Nitro-glycerine
is decomposed differently if it is ignited as dynamite (i.e., kieselguhr
dynamite), and if the gases are allowed to escape freely under a pressure
nearly equal to that of the atmosphere. Sarrau and Vieille obtained under
these conditions, for 100 volumes of gas--

NO     48.2 per cent.
CO     35.9     "
CO_{2} 12.7     "
H       1.6 per cent.
N       1.3     "
CH_{4}  0.3     "

These conditions are similar to those under which a mining charge, simply
ignited by the cap, burns away slowly under a low pressure (i.e., a miss
fire). In a recent communication, P.F. Chalon (_Engineering and Mining
Journal_, 1892) says, that in practice nitro-glycerine vapour, carbon
monoxide, and nitrous oxide, are also produced as the result of
detonation, but he attributes their formation to the use of a too feeble
detonator.

Nitro-glycerine explodes very violently by concussion. It may be burned in
an open vessel, but if heated above 250° C. it explodes. Professor C.E.
Munroe gives the firing point as 2O3°-2O5° C., and L. de Bruyn[A] states
its boiling point as 185°. He used the apparatus devised by Horsley. The
heat of formation of nitro-glycerine, as deduced from the heat of
combustion by M. Longuinine, is 432 calories for 1 grm.; and the heat of
combustion equals 1,576 cals. for 1 grm. In the case of nitro-glycerine
the heat of total combustion and the heat of complete decomposition are
interchangeable terms, since it contains an excess of oxygen. According to
Dr W.H. Perkin, F.R.S.,[B] the magnetic rotation of nitro-gylcerine is
5,407, and that of tri-methylene nitrate, 4.769 (diff. = .638). Dr Perkin
says: "Had nitro-glycerine contained its nitrogen in any other combination
with oxygen than as -O-NO_{2}, as it might if its constitution had been
represented as C_{3}H_{2}(NO_{2})_{3}(OH)_{3}, the rotation when compared
with propyl nitrate (4.085) would be abnormal."

[Footnote A: _Jour. Soc. Chem. Ind._, June 1896, p. 471.]

[Footnote B: _Jour. Chem. Soc._, W.H. Perkin, 1889, p. 726.]

The solubility of nitro-glycerine in various solvents has been
investigated by A.H. Elliot; his results may be summarised as follows:--

_______________________________________________________________________
                             |                      |
Solvent.                     |    Cold.             |       Warm.
_____________________________|______________________|__________________
                             |                      |
Water                        |   Insoluble          | Slightly soluble
Alcohol, absolute            |   Soluble            |    Soluble
   "     93%                 |      "               |       "
   "     80%                 |  Slowly soluble      |       "
   "     50%                 |   Insoluble          | Slightly soluble
Methyl alcohol               |   Soluble            |    Soluble
Amyl     "                   |      "               |       "
Ether, ethylic               |      "               |       "
  "    acetic                |      "               |       "
Chloroform                   |      "               |       "
Acetone                      |      "               |       "
Sulphuric acid (1.845)       |      "               |       "
Nitric acid (1.400)          |  Slowly soluble      |       "
Hydrochloric acid (1.200)    | Insoluble, decomposed| Slowly soluble
Acetic acid, glacial         |   Soluble            |    Soluble
Carbolic acid                |      "               |       "
Astral oil                   |   Insoluble          |    Insoluble
Olive   "                    |   Soluble            |    Soluble
Stearine oil                 |      "               |       "
Mineral jelly                |   Insoluble          |    Insoluble
Glycerine                    |      "               |       "
Benzene                      |   Soluble            |    Soluble
Nitro-benzene                |      "               |       "
Toluene                      |      "               |       "
Carbon bi-sulphide           |   Insoluble          | Slightly affected
Turpentine                   |      "               |    Soluble
Petroleum naphtha, 71°-76° B.|      "               |    Insoluble
Caustic soda (1:10 solution) | Insoluble.           |  Insoluble.
Borax, 5% solution           |      "               |       "
Ammonia (.980)               |      "               |       " slightly
                             |                      |    affected.
Ammonium sulph-hydrate       | Insoluble, sulphur   |  Decomposed.
                             |   separates          |
Iron sulphate solution       | Slightly affected    |  Affected.
Iron chloride (1.4 grm. Fe   | Slowly affected      |  Decomposed.
  to 10 c.c. N_{2}O)         |                      |
Tin chloride                 | Slightly affected    |  Affected.
_____________________________|______________________|__________________

Many attempts have been made to prepare nitro-glycerine explosives capable
of withstanding comparatively low temperatures without freezing, but no
satisfactory solution of the problem has been found. Among the substances
that have been proposed and used with more or less success, are nitro-
benzene, nitro-toluene, di-nitro-mono-chlorhydrine, solid nitro
derivatives of toluene,[A] are stated to lower the freezing point of
nitro-glycerine to -20°C. without altering its sensitiveness and
stability. The subject has been investigated by S. Nauckhoff,[B] who
states that nitroglycerine can be cooled to temperatures (-40° to -50° C.)
much below its true freezing point, without solidifying, by the addition
of various substances. When cooled by means of a mixture of solid carbon,
dioxide, and ether, it sets to a glassy mass, without any perceptible
crystallisation. The mass when warmed to 0°C. first rapidly liquefies and
then begins to crystallise. The true freezing point of pure nitro-
glycerine was found to be 12.3°C. The technical product, owing to the
presence of di-nitro-glycerine, freezes at 10.5° C. According to Raoult's
law, the lowering of the freezing point caused by _m_ grms. of a substance
with the molecular weight M, when dissolved in 100 grms. of the solvent,
is expressed by the formula: [Delta] = E(_m_/M), where E is a constant
characteristic for the solvent in question. The value of E for nitro-
glycerine was found to be 70.5 when calculated, according to Van't Hoff's
formula, from the melting point and the latent heat of fusion of the
substance. Determinations of the lowering of the freezing point of nitro-
glycerine by additions of benzene, nitro-benzene, di-nitro-benzene, tri-
nitro-benzene, p.-nitro-toluene, o.-nitro-toluene, di-nitro-toluene,
naphthalene, nitro-naphthalene, di-nitro-naphthalene, ethyl acetate, ethyl
nitrate, and methyl alcohol, gave results agreeing fairly well with
Raoult's formula, except in the case of methyl alcohol, for which the
calculated lowering of the freezing point was greater than that observed,
probably owing to the formation of complex molecules in the solution. The
results show that, in general, the capacity of a substance to lower the
freezing point of nitro-glycerine depends, not upon its freezing point, or
its chemical composition or constitution, but upon its molecular weight.
Nauckhoff states that a suitable substance for dissolving in nitro-
glycerine, in order to lower the freezing point of the latter, must have a
relatively low molecular weight, must not appreciably diminish the
explosive power and stability of the explosive, and must not be easily
volatile at relatively high atmospheric temperatures; it should, if
possible, be a solvent of nitro-cellulose, and in every case must not have
a prejudicial influence on the gelatinisation of the nitro-cellulose.

[Footnote A: Eng. Pat. 25,797, November 1904.]

[Footnote B: _Z. Angew. Chem._, 1905, 18, 11-22, 53-60.]

~Manufacture of Nitro-Glycerine.~--Nitro-glycerine is prepared upon the
manufacturing scale by gradually adding glycerine to a mixture of nitric
and sulphuric acids of great strength. The mixed acids are contained in a
lead vessel, which is kept cool by a stream of water continually passing
through worms in the interior of the nitrating vessel, and the glycerine
is gradually added in the form of a fine stream from above. The
manufacture can be divided into three distinct operations, viz.,
nitration, separation, and washing, and it will be well to describe these
operations in the above order.

~Nitration.~--The most essential condition of nitrating is the correct
composition and strength of the mixed acids. The best proportions have
been found to be three parts by weight of nitric acid of a specific
gravity 1.525 to 1.530, and containing as small a portion of the oxides of
nitrogen as possible, to five parts by weight of sulphuric acid of a
specific gravity of 1.840 at 15° C., and about 97 per cent. of mono-
hydrate. It is of the very greatest importance that the nitric acid should
be as strong as possible. Nothing under a gravity of 1.52 should ever be
used even to mix with stronger acid, and the nitration will be
proportional to the strength of the acid used, provided the sulphuric acid
is also strong enough. It is also of great importance that the oxides of
nitrogen should be low, and that they should be kept down to as low as 1
per cent., or even lower. It is also very desirable that the nitric acid
should contain as little chlorine as possible. The following is the
analysis of a sample of nitric acid, which gave very good results upon the
commercial scale:--Specific gravity, 1.525, N_{2}O_{4}, 1.03 per cent.;
nitric acid (HNO_{3}), 95.58 per cent.

The amount of real nitric acid (mono-hydrate) and the amount of nitric
peroxide present in any sample should always be determined before it is
used for nitrating purposes. The specific gravity is not a sufficient
guide to the strength of the acid, as an acid having a high gravity, due
to some 3 or 4 per cent of nitric oxides in solution, will give very poor
nitration results. A tenth normal solution of sodium hydroxide (NaOH),
with phenol-phthalein as indicator, will be found the most convenient
method of determining the total acid present. The following method will be
found to be very rapid and reliable:--Weigh a 100 c.c. flask, containing a
few cubic centimetres of distilled water, and then add from a pipette 1
c.c. of the nitric acid to be examined, and reweigh (this gives the weight
of acid taken). Now make up to 100 c.c. at 15° C.; shake well, and take
out 10 c.c. with a pipette; drain into a small Erlenmeyer flask, and add a
little of the phenol-phthalein solution, and titrate with the tenth normal
soda solution.

The nitric peroxide can be determined with a solution of potassium
permanganate of N/10 strength, thus: Take a small conical flask,
containing about 10 c.c. of water, and add from a burette 10 to 16 c.c. of
the permanganate solution; then add 2 c.c. of the acid to be tested, and
shake gently, and continue to add permanganate solution as long as it is
decolourised, and until a faint pink colour is permanent.

_Example._ N/10 permanganate 3.16 grms. per litre, 1 c.c. = O.0046 grm.
N_{2}O_{4}, 2 c.c. of sample of acid specific gravity 1.52 = 3.04 grms.
taken for analysis. Took 20 c.c. permanganate solution, O.0046 x 20 =.092
grm. N_{2}O_{4}, and (.092 x 100)/3.04 = 3.02 per cent. N_{2}O_{4}. The
specific gravity should be taken with an hydrometer that gives the
specific gravity directly, or, if preferred, the 2 c.c. of acid may be
weighed.

A very good method of rapidly determining the strength of the sulphuric
acid is as follows:--Weigh out in a small weighing bottle, as nearly as
possible, 2.45 grms. This is best done by running in 1.33 c.c. of the acid
(1.33 x 1.84 = 2.447). Wash into a large Erlenmeyer flask, carefully
washing out the bottle, and also the stopper, &c. Add a drop of phenol-
phthalein solution and titrate, with a half normal solution of sodium
hydrate (use a 100 c.c. burette). Then if 2.45 grms. exactly have been
taken, the readings on the burette will equal percentages of H_{2}SO_{4}
(mono-hydrate) if not, calculate thus:--2.444 grms. weighed, required 95.4
c.c. NaOH. Then--

2.444 : 95.4 :: 2.45 : _x_ = 95.64 per cent. H_{2}SO_{4}.

It has been proposed to free nitric acid from the oxides of nitrogen by
blowing compressed air through it, and thus driving the gases in solution
out. The acid was contained in a closed lead tank, from which the escaping
fumes were conducted into the chimney shaft, and on the bottom of which
was a lead pipe, bent in the form of a circle, and pierced with holes,
through which the compressed air was made to pass; but the process was not
found to be of a very satisfactory nature, and it is certainly better not
to allow the formation of these compounds in the manufacture of the acid
in the first instance. Another plan, however, is to heat the acid gently,
and thus drive out the nitrous gases. Both processes involve loss of
nitric acid.

Having obtained nitric and sulphuric acids as pure as possible, the next
operation is to mix them. This is best done by weighing the carboys in
which the acids are generally stored before the acids are drawn off into
them from the condensers, and keeping their weights constantly attached to
them by means of a label. It is then a simple matter to weigh off as many
carboys of acid as may be required for any number of mixings, and subtract
the weights of the carboys. The two acids should, after being weighed, be
poured into a tank and mixed, and subsequently allowed to flow into an
acid egg or montjus, to be afterwards forced up to the nitrating house in
the danger area. The montjus or acid egg is a strong cast-iron tank, of
either an egg shape, or a cylinder with a round end. If of the former
shape, it would lie on its side, and upon the surface of the ground, and
would have a manhole at one end, upon which a lid would be strongly bolted
down; but if of the latter shape, the lid, of course, is upon the top, and
the montjus itself is let into the ground. In either case, the principle
is the same. One pipe, made of stout lead, goes to the bottom, and another
just inside to convey the compressed air, the acids flowing away as the
pressure is put on, just as blowing down one tube of an ordinary wash-
bottle forces the water up the other tube to the jet. The pressure
necessarily will, of course, vary immensely, and will depend upon the
height to which the acid has to be raised and the distance to be
traversed.

The mixed acids having been forced up to the danger area, and to a level
higher than the position of the nitrating house, should, before being
used, be allowed to cool, and leaden tanks of sufficient capacity to hold
at least enough acid for four or five nitrations should be placed in a
wooden house upon a level at least 6 or 7 feet above the nitrating house.
In this house also should be a smaller lead tank, holding, when filled to
a certain mark, just enough of the mixed acids for one nitration. The
object of this tank is, that as soon as the man in charge knows that the
last nitration is finished, he refills this smaller tank (which contains
just enough of the mixed acids), and allows its contents to flow down into
the nitrating house and into the nitrator, ready for the next nitration.
The nitration is usually conducted in a vessel constructed of lead, some 4
feet wide at the bottom, and rather less at the top, and about 4 feet or
so high. The size, of course, depends upon the volume of the charge it is
intended to nitrate at one operation, but it is always better that the
tank should be only two-thirds full. A good charge is 16 cwt. of the mixed
acids, in the proportion of three to five; that is, 6 cwt. of nitric acid,
and 10 cwt. of sulphuric acid, and 247 lbs. of glycerine.

Upon reference to the equation showing the formation of nitro-glycerine,
it will be seen that for every 1 lb. of glycerine 2.47 lbs. of nitro-
glycerine should be furnished,[A] but in practice the yield is only a
little over 2 lbs., the loss being accounted for by the unavoidable
formation of some of the lower nitrate of glycerine (the mono-nitrate),
which afterward dissolves in the washing waters. The lead tank (Fig. 5) is
generally cased in woodwork, with a platform in front for the man in
charge of the nitrating to stand upon, and whence to work the various
taps. The top of the tank is closed in with a dome of lead, in which is a
small glass window, through which the progress of the nitrating operation
can be watched. From the top of this dome is a tube of lead which is
carried up through the roof of the building. It serves as a chimney to
carry off the acid fumes which are given off during the nitration. The
interior of this tank contains at least three concentric spirals of at
least 1-inch lead pipe, through which water can be made to flow during the
_whole_ operation of nitrating. Another lead pipe is carried through the
dome of the tank, as far as the bottom, where it is bent round in the form
of a circle. Through this pipe, which is pierced with small holes, about 1
inch apart, compressed air is forced at a pressure of about 60 lbs. in
order to keep the liquids in a state of constant agitation during the
whole period of nitration. There must also be a rather wide pipe, of say 2
inches internal diameter, carried through the dome of the tank, which will
serve to carry the mixed acid to be used in the operation into the tank.
There is still another pipe to go through the dome, viz., one to carry the
glycerine into the tank. This need not be a large bore pipe, as the
glycerine is generally added to the mixed acids in a thin stream (an
injector is often used).

[Footnote A: Thus if 92 lbs. glycerine give 227 lbs. nitro-glycerine,
(277 x 1)/92 = 2.47 lbs.]

[Illustration: FIG. 5.--TOP OF NITRATOR. _A_, Fume Pipe; _B_, Water Pipes
for Cooling; _C_, Acid Mixture Pipe; _E_, Compressed Air; _G_, Glycerine
Pipe and Funnel; _T_, Thermometer; _W_, Window.]

Before the apparatus is ready for use, it requires to have two
thermometers fixed, one long one to reach to the bottom of the tank, and
one short one just long enough to dip under the surface of the acids. When
the tank contains its charge, the former gives the temperature of the
bottom, and the latter of the top of the mixture. The glycerine should be
contained in a small cistern, fixed in some convenient spot upon the wall
of the nitrating house, and should have a pipe let in flush with the
bottom, and going through the dome of the nitrating apparatus. It must of
course be provided with a tap or stop-cock, which should be placed just
above the point where the pipe goes through the lead dome.

Some method of measuring the quantity of glycerine used must be adopted. A
gauge-tube graduated in inches is a very good plan, but it is essential
that the graduations should be clearly visible to the operator upon the
platform in front of the apparatus. A large tap made of earthenware (and
covered with lead) is fixed in the side of the nitrating tank just above
the bottom, to run off the charge after nitration. This should be so
arranged that the charge may be at option run down the conduit to the next
house or discharged into a drowning tank, which may sometimes be necessary
in cases of decomposition. The drowning tank is generally some 3 or 4
yards long and several feet deep, lined with cement, and placed close
outside the building.

The apparatus having received a charge of mixed acids, the water is
started running through the pipes coiled inside the tank, and a slight
pressure of compressed air is turned on,[A] to mix the acids up well
before starting. The nitration should not be commenced until the two
thermometers register a temperature of 18° C. The glycerine tap is then
partially opened, and the glycerine slowly admitted, and the compressed
air turned on full, until the contents of the apparatus are in a state of
very brisk agitation. A pressure of about 40 lbs. is about the minimum (if
247 lbs. of glycerine and 16 cwt. of acids are in the tank). If the
glycerine tube is fitted with an injector, it may be turned on almost at
once. The nitration will take about thirty minutes to complete, but the
compressed air and water should be kept on for an additional ten minutes
after this, to give time for all the glycerine to nitrate. The temperature
should be kept as low as possible (not above 18° C.).

[Footnote A: At the Halton Factory, Germany, cylinders of compressed
carbon dioxide are connected with the air pipes so that in the event of a
failure of the air supply the stirring can be continued with this gas if
necessary.]

The chief points to attend to during the progress of the nitration are--

1. The temperature registered by the two thermometers.

2. The colour of the nitrous fumes given off (as seen through the little
window in the dome of the apparatus).

3. The pressure of the compressed air as seen from a gauge fixed upon the
air pipe just before it enters the apparatus.

4. The gauge showing the quantity of glycerine used. The temperature, as
shown by either of the two thermometers, should not be at any time higher
than 25° C.

If it rises much above this point, the glycerine should be at once shut
off, and the pressure of air increased for some few minutes until the
temperature falls, and no more red fumes are given off.

The nitration being finished, the large earthenware tap at the bottom of
the tank is opened, and the charge allowed to flow away down the conduit
to the next building, i.e., to the separator.

The nitrating house is best built of wood, and should have a close-boarded
floor, which should be kept scrupulously clean, and free from grit and
sand. A wooden pail and a sponge should be kept in the house in order that
the workman may at once clean up any mess that may be made, and a small
broom should be handy, in order that any sand, &c., may be at once
removed. It is a good plan for the nitrator to keep a book in which he
records the time of starting each nitration, the temperature at starting
and at the finish, the time occupied, and the date and number of the
charge, as this enables the foreman of the danger area at any time to see
how many charges have been nitrated, and gives him other useful
information conducive to safe working. Edward Liebert has devised an
improvement in the treatment of nitro-glycerine. He adds ammonium sulphate
or ammonium nitrate to the mixed acids during the operation of nitrating,
which he claims destroys the nitrous acid formed according to the
equation--

(NH_{4})_{2}SO_{4} + 2HNO_{3} = H_{2}SO_{4} + 2N_{2} + 4H_{2}O.

I am not aware that this modification of the process of nitration is in
use at the present time.

The newly made charge of nitro-glycerine, upon leaving the nitrating
house, flows away down the conduit, either made of rubber pipes, or better
still, of woodwork, lined with lead and covered with lids made of wood (in
short lengths), in order that by lifting them at any point the condition
of the conduit can be examined, as this is of the greatest importance, and
the conduit requires to be frequently washed out and the sulphate of lead
removed. This sulphate always contains nitro-glycerine, and should
therefore be burnt in some spot far removed from any danger building or
magazine, as it frequently explodes with considerable violence.

[Illustration: FIG. 6.--SMALL NITRATOR. _N_, Tap for Discharging; _P_,
Water Pipes; _T_, Thermometer; _W_, Windows; _P'_, Glycerine Pipe.]

In works where the manufacture of nitro-glycerine is of secondary
importance, and some explosive containing only perhaps 10 per cent. of
nitroglycerine is manufactured, and where 50 or 100 lbs. of glycerine are
nitrated at one time, a very much smaller nitrating apparatus than the one
that has been already described will be probably all that is required. In
this case the form of apparatus shown in Fig. 6 will be found very
satisfactory. It should be made of stout lead (all lead used for tanks,
&c., must be "chemical lead"), and may be made to hold 50 or 100 lbs. as
found most convenient. This nitrator can very well be placed in the same
house as the separator; in fact, where such a small quantity of nitro-
glycerine is required, the whole series of operations, nitrating,
separation, and washing, &c., may very well be performed in the same
building. It will of course be necessary to place the nitrator on a higher
level than the separator, but this can easily be done by having platforms
of different heights, the nitration being performed upon the highest. The
construction of this nitrator is essentially the same as in the larger
one, the shape only being somewhat different. Two water coils will
probably be enough, and one thermometer. It will not be necessary to cover
this form in with woodwork.

~The Nathan Nitrator.~[A]--This nitrator is the patent of Lt. Col. F.L.
Nathan and Messrs J.M. Thomson and W. Rintoul of Waltham Abbey, and will
probably before long entirely supersede all the other forms of nitrator on
account of its efficiency and economy of working. With this nitrator it is
possible to obtain from 2.21 to 2.22 parts of nitro-glycerine from every 1
part of glycerine. The apparatus is so arranged that the nitration of the
glycerine, the separation of nitro-glycerine produced, as well as the
operation of "after-separation," are carried out in one vessel. The usual
nitrating vessel is provided with an acid inlet pipe at the bottom, and a
glass separation cylinder with a lateral exit or overflow pipe at the top.
This cylinder is covered by a glass hood or bell jar during nitration to
direct the escaping air and fumes into a fume pipe where the flow of the
latter may be assisted by an air injector. The lateral pipe in the
separation cylinder is in connection with a funnel leading to the prewash
tank. The drawing (Fig. 7) shows a vertical section of the apparatus; _a_
is the nitrating vessel of usual construction, having at the bottom an
acid inlet pipe with three branches, one leading to the de-nitrating
plant, _c_ leading to the drowning tank, and _d_, which extends upwards
and has two branches, _e_ leading to the nitrating acids tank, and _f_ to
the waste acid tank. On the sloped bottom of the nitrating vessel _a_ lies
a coil _g_ of perforated pipe for blowing air, and there are in the vessel
several coils _h_, three shown in the drawing, for circulation of cooling
water. At the top of the vessel there is a glass cylinder _i_, having a
lateral outlet _j_ directed into the funnel mouth of a pipe _k_ leading to
the prewash tank. Over the cylinder _i_ is a glass globe _l_, into which
opens a pipe _m_ for leading off fumes which may be promoted by a
compressed air jet from a pipe _r_ operating as an injector. Into an
opening of the glass dome _l_ is inserted a vessel _n_, which is connected
by a flexible pipe _p_ to the glycerine tank, and from the bottom of _n_,
which is perforated and covered with a disc perforated with holes
registering with those through the bottom, this disc being connected by a
stem with a knob _q_ by which it can be turned so as to throttle or cut
off passage of glycerine through the bottom. _s_ is a thermometer for
indicating the temperature of the contents of the vessel.

[Footnote A: Eng. Pat. 15,983, August 1901.]

[Illustration: FIG. 7.--NATHAN'S NITRATOR FOR NITRO-GLYCERINE. (_a_)
Nitrating Vessel; (_b_) to Separating Vessel; (_c_) to Drowning Tank;
(_e_) Nitrating Acids enter (_f_) to the Waste Acids; (_g_) Coils for
Compressed Air; (_h_) Pipes for Cooling Water; (_i_) Glass Cylinder; (_j_)
Outlet to _k_; (_k_) leading to Prewash Tank; (_l_) Glass Dome; (_m_) Pipe
to lead off for Escape of Fumes; (_n_) Vessel; (_p_) Pipe conveying
Glycerine; (_q_) Knob to turn off Glycerine; (_r_) Compressed Air Jet;
(_s_) Thermometer.]

In operating with this apparatus the nitrating acid is introduced into the
nitrating vessel by opening the cock of the pipe _e_. The glycerine is
then run in by introducing _n_ and opening the valve at its bottom, the
contents of the vessel being agitated by air blown through the
perforations of the pipe _g_. When the glycerine is all nitrated and the
temperature has slightly fallen, the circulation of the water through the
coils _h_ and the air-stirring are stopped, and the glycerine supply
vessel _n_ is removed. The nitro-glycerine as it separates from the acids
is raised by introducing by the pipe _f_ waste acid from a previous
charge, this displacing the nitro-glycerine upwards and causing it to flow
by the outlet, _j_ and pipe _k_ to the prewash tank. When nearly all the
nitro-glycerine has been separated in this manner the acids in the
apparatus may be run off by the pipe _b_ to an after separating vessel for
further settling, thus leaving the apparatus free for another nitration,
or the nitrating vessel itself may be used as an after separating bottle
displacing the nitro-glycerine with waste acid as it rises to the top, or
skimming off in the usual manner. When the separation of the nitro-
glycerine is complete the waste acid is run off and denitrated as usual, a
portion of it being reserved for the displacement of the nitro-glycerine
in a subsequent operation.

In a further patent (Eng. Pat. 3,020, 1903) the authors propose with the
object of preventing the formation and separation of nitro-glycerine in
the waste acids, after the nitro-glycerine initially formed in the
nitrating vessel has been separated and removed, to add a small quantity
of water to the waste acids; this is carried out as follows. A relatively
small quantity of water is added, and this prevents all further separation
of nitro-glycerine, and at the same time the strength of the waste acids
is so slightly reduced that their separation and re-concentration are not
affected. "After-separation" is thus done away with, and the nitro-
glycerine plant simplified and its output increased. After nitration
separation is commenced at a temperature such that when all the displacing
acid has been added, and the separation of the nitro-glycerine is
complete, the temperature of the contents of the nitrating vessel shall
not be lower than 15° C. A sufficient quantity of the displacing acid is
then run off through the waste-acid cock to allow of the remaining acids
being air-stirred without splashing over the top. A small quantity of
water, from 2 to 3 per cent. according to strength of acid; if waste
consists of sulphuric acid (monohydrate), 62 per cent.; nitric acid
(anhydrous), 33 per cent. and water 5 per cent.; temperature 15° C., then
2 per cent. of water is added; if waste acids contain less than 4 per
cent. of water of temperature lower than 15° C., from 3 to 5 per cent. of
water may have to be added. The water is added slowly through the
separator cylinder, and the contents of the nitrator air-stirred, but not
cooled, the temperature being allowed to rise slowly and regularly as the
water is added--usually about 3° C. for each per cent. of water added.
When air-agitation has been stopped, the acids are kept at rest for a
short time, in order to allow of any small quantity of initially formed
nitro-glycerine adhering to the coils and sides of the vessel rising to
the top. When this has been separated by displacement, the acids are ready
for denitration, or can be safely stored without further precaution.

~Separation.~--The nitro-glycerine, together with the mixed acids, flows
from the nitrating house to the separating house, which must be on a lower
level than the former. The separating house contains a large lead-lined
tank, closed in at the top with a wooden lid, into which a lead pipe of
large bore is fixed, and which is carried up through the roof of the
building, and acts as a chimney to carry off any fumes. A little glass
window should be fixed in this pipe in order that the colour of the
escaping fumes may be seen. The conduit conveying the nitro-glycerine
enters the building close under the roof, and discharges its contents into
the tank through the pipe G (Fig. 8). The tank is only about two-thirds
filled by the charge. There is in the side of the tank a small window of
thick plate glass, which enables the workman to see the level of the
charge, and also to observe the progress of the separation, which will
take from thirty minutes to one hour.

The tank should be in connection with a drowning tank, as the charge
sometimes gets very dangerous in this building. It must also be connected
by a conduit with the filter house, and also to the secondary separator by
another conduit. The tank should also be fitted with a compressed air
pipe, bent in the form of a loop. It should lie upon the bottom of the
vat. The object of this is to mix up the charge in case it should get too
hot through decomposition. A thermometer should of course be fixed in the
lid of the tank, and its bulb should reach down to the middle of the
nitro-glycerine (which rests upon the surface of the mixed acids, the
specific gravity of the nitro-glycerine being 1.6, and that of the waste
acids 1.7; the composition of the acids is now 11 per cent. HNO_{3}, 67
per cent. H_{2}SO_{4}, and 22 per cent. water), and the temperature
carefully watched.

[Illustration: FIG. 8.--SEPARATOR. _A_, Compressed Air Pipes; _G_, Nitro-
glycerine enters from Nitrator; _N_, Nitro-glycerine to _P_; _L_, Lantern
Window; _W_, Window in Side; _S_, Waste Acids to Secondary Separator; _T_,
Tap to remove last traces of Nitro-glycerine; _P_, Lead Washing Tank; _A_,
Compressed Air; _W_, Water Pipe; _N_, Nitro-glycerine from Separator.]

If nothing unusual occurs, and it has not been necessary to bring the
compressed air into use, and so disturb the process of separation, the
waste acids may be run away from beneath the nitro-glycerine, and allowed
to flow away to the secondary separator, where any further quantity of
nitro-glycerine that they contain separates out after resting for some
days. The nitro-glycerine itself is run into a smaller tank in the same
house, where it is washed three or four times with its own bulk of water,
containing about 3 lbs. of carbonate of soda to neutralise the remaining
acid. This smaller tank should contain a lead pipe, pierced and coiled
upon the bottom, through which compressed air may be passed, in order to
stir up the charge with the water and soda. After this preliminary
washing, the nitro-glycerine is drawn off into indiarubber buckets, and
poured down the conduit to the filter house. The wash waters may be sent
down a conduit to another building, in order to allow the small quantity
of nitro-glycerine that has been retained in the water as minute globules
to settle, if thought worth the trouble of saving. This, of course, will
depend upon the usual out-turn of nitro-glycerine in a day, and the
general scale of operations.

[Illustration: FIG. 9.--FILTERING AND WASHING PLANT. _W_, Lead Washing
Tank; _WP_, Water Pipe; _L_, Lid; _S_, Nitro-glycerine from Separator; _A,
B, C_, Filtering Tanks; _B2_, Indiarubber Bucket.]

~Filtering and Washing.~--The filter house (Fig. 9), which must of course
be again on a somewhat lower level than the separating house, must be a
considerably larger building than either the nitrating or separating
houses, as it is always necessary to be washing some five or six charges
at the same time. Upon the arrival of the nitro-glycerine at this house,
it first flows into a lead-lined wooden tank (W), containing a compressed
air pipe, just like the one in the small tank in the separating house.
This tank is half filled with water, and the compressed air is turned on
from half to a quarter of an hour after the introduction of the charge.
The water is then drawn off, and fresh water added. Four or five washings
are generally necessary. The nitro-glycerine is then run into the next
tank (A), the top of which is on a level with the bottom of the first one.
Across the top of this tank is stretched a frame of flannel, through which
the nitroglycerine has to filter. This removes any solid matters, such as
dirt or scum. Upon leaving this tank, it passes through a similar flannel
frame across another tank (B), and is finally drawn off by a tap in the
bottom of the tank into rubber buckets. The taps in these tanks are best
made of vulcanite.

At this stage, a sample should be taken to the laboratory and tested. If
the sample will not pass the tests, which is often the case, the charge
must be rewashed for one hour, or some other time, according to the
judgment of the chemist in charge. In the case of an obstinate charge, it
is of much more avail to wash a large number of times with small
quantities of water, and for a short time, than to use a lot of water and
wash for half an hour. Plenty of compressed air should be used, as the
compound nitric ethers which are formed are thus got rid of. As five or
six charges are often in this house at one time, it is necessary to have
as many tanks arranged in tiers, otherwise one or two refractory charges
would stop the nitrating house and the rest of the nitro-glycerine plant.
The chief causes of the washed material not passing the heat test are,
either that the acids were not clean, or they contained objectionable
impurities, or more frequently, the quality of the glycerine used. The
glycerine used for making nitro-glycerine should conform to the following
tests, some of which, however, are of greater importance than others. The
glycerine should--

1. Have minimum specific gravity at 15° C. of 1.261.

2. Should nitrify well.

3. Separation should be sharp within half an hour, without the separation
of flocculent matter, nor should any white flocculent matter (due to fatty
acids) be formed when the nitrated glycerine is thrown into water and
neutralised with carbonate of soda.

4. Should be free from lime and chlorine, and contain only traces of
arsenic, sulphuric acid, &c.

5. Should not leave more than 0.25 per cent. of inorganic and organic
residue together when evaporated in a platinum dish without ebullition
(about 160° C.) or partial decomposition.

6. Silver test fair.

7. The glycerine, when diluted one-half, should give no deposit or
separation of fatty acids when nitric peroxide gas is passed through it.
(Nos. 1, 2, 3, and 5 are the most essential.)

The white flocculent matter sometimes formed is a very great nuisance, and
any sample of glycerol which gives such a precipitate when tried in the
laboratory should at once be rejected, as it will give no end of trouble
in the separating house, and also in the filter house, and it will be very
difficult indeed to make the nitro-glycerine pass the heat test. The out-
turn of nitro-glycerine also will be very low. The trouble will show
itself chiefly in the separating operation. Very often 2 or 3 inches will
rise to the surface or hang about in the nitro-glycerine, and at the point
of contact between it and the mixed acids, and will afterwards be very
difficult to get rid of by filtration. The material appears to be partly
an emulsion of the glycerine, and partly due to fatty acids, and as there
appears to be no really satisfactory method of preventing its formation,
or of getting rid of it, the better plan is not to use any glycerine for
nitrating that has been found by experiment upon the laboratory scale to
give this objectionable matter. One of the most useful methods of testing
the glycerine, other than nitrating, is to dilute the sample one-half with
water, and then to pass a current of nitric peroxide gas through it, when
a flocculent precipitate of elaïdic acid (less soluble in glycerine than
the original oleic acid) will be formed. Nitrogen peroxide, N_{2}O_{4}, is
best obtained by heating dry lead nitrate (see Allen, "Commercial Organic
Analysis," vol. ii., 301).

When a sample of nitro-glycerine is brought to the laboratory from the
filter house, it should first be examined to see that it is not acid.[A] A
weak solution of Congo red or methyl orange may be used. If it appears to
be decidedly alkaline, it should be poured into a separating funnel, and
shaken with a little distilled water. This should be repeated, and the
washings (about 400 c.c.) run into a beaker, a drop of Congo red or methyl
orange added, and a drop or so of N/2 hydrochloric acid added, when it
should give, with two or three drops at most, a blue colour with the Congo
red, or pink with the methyl orange, &c. The object of this test is to
show that the nitro-glycerine is free from any excess of soda, i.e., that
the soda has been properly washed out, otherwise the heat test will show
the sample to be better than it is. The heat test must also be applied.

[Footnote A: A. Leroux, _Bul. Soc. Chim. de Bel._, xix., August 1905,
contends that experience does not warrant the assumption that free acid is
a source of danger in nitro-glycerine or nitro-cellulose; free alkali, he
states, promotes their decomposition.]

Upon leaving the filter house, where it has been washed and filtered, and
has satisfactorily passed the heat test, it is drawn off from the lowest
tank in indiarubber buckets, and poured down the conduit leading to the
precipitating house, where it is allowed to stand for a day, or sometimes
longer, in order to allow the little water it still contains to rise to
the surface. In order to accomplish this, it is sufficient to allow it to
stand in covered-in tanks of a conical form, and about 3 or 4 feet high.
In many works it is previously filtered through common salt, which of
course absorbs the last traces of water. It is then of a pale yellow
colour, and should be quite clear, and can be drawn off by means of a tap
(of vulcanite), fixed at the bottom of the tanks, into rubber buckets, and
is ready for use in the preparation of dynamite, or any of the various
forms of gelatine compounds, smokeless powders, &c., such as cordite,
ballistite, and many others.

Mikolajezak (_Chem. Zeit._, 1904, Rep. 174) states that he has prepared
mono- and di-nitro-glycerine, and believes that the latter compound will
form a valuable basis for explosives, as it is unfreezable. It is stated
to be an odourless, unfreezable oil, less sensitive to percussion,
friction, and increase of temperature, and to possess a greater solvent
power for collodion-cotton than ordinary nitro-glycerine. It can thus be
used for the preparation of explosives of high stability, which will
maintain their plastic nature even in winter. The di-nitro-glycerine is a
solvent for tri-nitro-glycerine, it can therefore be mixed with this
substance, in the various gelatine explosives in order to lower the
freezing point.

~The Waste Acids.~--The waste acids from the separating house, from which
the nitro-glycerine has been as completely separated as possible, are run
down the conduit to the secondary separator, in order to recover the last
traces of nitro-glycerine that they contain. The composition of the waste
acids is generally somewhat as follows:--Specific gravity, 1.7075 at 15°
C.; sulphuric acid, 67.2 per cent.; nitric acid, 11.05 per cent.; and
water, 21.7 per cent., with perhaps as much as 2 per cent. of nitric
oxide, and of course varying quantities of nitro-glycerine, which must be
separated, as it is impossible to run this liquid away (unless it can be
run into the sea) or to recover the acids by distillation as long as it
contains this substance. The mixture, therefore, is generally run into
large circular lead-lined tanks, covered in, and very much like the
nitrating apparatus in construction, that is, they contain worms coiled
round inside, to allow of water being run through to keep the mixture
cool, and a compressed air pipe, in order to agitate the mixture if
necessary. The top also should contain a window, in order to allow of the
interior being seen, and should have a leaden chimney to carry off the
fumes which may arise from decomposition. It is also useful to have a
glass tube of 3 or 4 inches in diameter substituted for about a foot of
the lead chimney, in order that the man on duty can at any time see the
colour of the fumes arising from the liquid. There should also be two
thermometers, one long one reaching to the bottom of the tank, and one to
just a few inches below the surface of the liquid.

The nitro-glycerine, of course, collects upon the surface, and can be
drawn off by a tap placed at a convenient height for the purpose. The
cover of the tank is generally conical, and is joined to a glass cylinder,
which is cemented to the top of this lead cover, and also to the lead
chimney. In this glass cylinder is a hole into which fits a ground glass
stopper, through which the nitro-glycerine can be drawn off. There will
probably never be more than an inch of nitro-glycerine at the most, and
seldom that. It should be taken to the filter house and treated along with
another charge. The acids themselves may either be run to waste, or better
treated by some denitration plant. This house probably requires more
attention than any other in the danger area, on account of the danger of
the decomposition of the small quantities of nitro-glycerine, which, as it
is mixed with such a large quantity of acids and water, is very apt to
become hot, and decomposition, which sets up in spots where a little
globule of nitro-glycerine is floating, surrounded by acids that gradually
get hot, gives off nitrous fumes, and perhaps explodes, and thus causes
the sudden explosion of the whole. The only way to prevent this is for the
workman in charge to look at the thermometers _frequently_, and at the
colour of the escaping fumes, and if he should notice a rise of
temperature or any appearance of red fumes, to turn on the water and air,
and stir up the mixture, when probably the temperature will suddenly fall,
and the fumes cease to come off.

The cause of explosions in this building is either the non-attention of
the workmen in charge, or the bursting of one of the water pipes, by which
means, of course, the water, finding its way into the acids, causes a
sudden rise of temperature. If the latter of these two causes should
occur, the water should at once be shut off and the air turned on full,
but if it is seen that an explosion is likely to occur, the tank should at
once be emptied by allowing its contents to run away into a drowning tank
placed close outside the house, which should be about 4 feet deep, and
some 16 feet long by 6 feet wide; in fact, large enough to hold a
considerable quantity of water. But this last course should only be
resorted to as a last extremity, as it is extremely troublesome to recover
the small quantity of nitro-glycerine from the bottom of this tank, which
is generally a bricked and cemented excavation some few yards from the
house.

It has been proposed to treat these waste acids, containing nitro-
glycerine, in Mr M. Prentice's nitric acid retort. In this case they would
be run into the retort, together with nitrate of soda, in a fine stream,
and the small quantity of nitro-glycerine, coming into contact with the
hot mixture already in the retort, would probably be at once decomposed.
This process, although not yet tried, promises to be a success. Several
processes have been used for the denitration of these acids.

~Treatment of the Waste Acid from the Manufacture of Nitro-Glycerine and
Gun-Cotton.~--The composition of these acids is as follows:--

                     Nitro-glycerine  and  Gun-cotton
                                Waste Acid.

Sulphuric acid     70 per cent.          78 per cent.
Nitric acid        10    "               12    "
Water              20    "               10    "

The waste acid from the manufacture of gun-cotton is generally used direct
for the manufacture of nitric acid, as it contains a fairly large amount
of sulphuric acid, and the small amount of nitro-cellulose which it also
generally contains decomposes gradually and without explosion in the
retort. Nitric acid may be first distilled off, the resulting sulphuric
acid being then added to the equivalent amount of nitrate of soda. Nitric
acid is then distilled over and condensed in the usual way. Very often,
however, the waste acid is added direct to the charge of nitrate without
previously eliminating the nitric acid. The treatment of the waste acid
from the manufacture of nitro-glycerine is somewhat different. The small
amount of nitro-glycerine in this acid must always be eliminated. This is
effected either by allowing the waste acid to stand for at least twenty-
four hours in a big vessel with a conical top, where all the nitro-
glycerine which will have separated to the surface is removed by skimming;
or, better still, the "watering down process" of Col. Nathan may be
employed. In Nathan's nitrator every existing trace of nitro-glycerine is
separated from the acids in a few hours after the nitration, and any
further formation of nitro-glycerine is prevented by adding about 2 per
cent. of water to the waste acids, which are kept agitated during the
addition. The waste acid, now free from nitro-glycerine, but which may
still contain organic matter, is denitrated by bringing it into contact
with a jet of steam. The waste acid is passed in a small stream down
through a tower of acid-resisting stoneware (volvic stone), which is
closely packed with earthenware, and at the bottom of which is the steam
jet. Decomposition proceeds as the acid meets the steam, nitric and
nitrous acids are disengaged and are passed out at the top of the tower
through a pipe to a series of condensers and towers, where the nitric acid
is collected. The nitrous acid may be converted into nitric acid by
introducing a hot compressed air jet into the gases before they pass into
the condensers. Weak sulphuric acid of sp. gr. 1.6 collects in a saucer in
which the tower stands, and is then passed through a cooling worm. The
weak sulphuric acid, now entirely free from nitric and nitrous acids, may
be concentrated to sp. gr. 1.842 and 96 per cent. H_{2}SO_{4} by any of
the well-known processes, e.g., Kessler, Webb, Benker, Delplace, &c., and
it may be used again in the manufacture of nitro-glycerine or gun-cotton.

Two points in the manufacture of nitro-glycerine are of the greatest
importance, viz., the purity of the glycerine used, and the strength and
purity of the acids used in the nitration. With regard to the first of
these, great care should be taken, and a complete analysis and thorough
examination, including a preliminary experimental nitration, should always
be instituted. As regards the second, the sulphuric acid should not only
be strong (96 per cent.), but as free from impurities as possible. With
the nitric acid, which is generally made at the explosive works where it
is used, care must be taken that it is as strong as possible (97 per cent.
and upwards). This can easily be obtained if the plant designed by Mr
Oscar Guttmann[A] is used. Having worked Mr Guttmann's plant for some
time, I can testify as to its value and efficiency.

[Footnote A: "The Manufacture of Nitric Acid," _Jour. Soc. Chem. Ind._,
March 1893.]

Another form of nitric acid plant, which promises to be of considerable
service to the manufacturer of nitric acid for the purpose of nitrating,
is the invention of the late Mr Manning Prentice, of Stowmarket. Through
the kindness of Mr Prentice, I visited his works to see the plant in
operation. It consists of a still, divided into compartments or chambers
in such a manner that the fluid may pass continuously from one to the
other. The nitric acid being continuously separated by distillation, the
contents of each division vary--the first containing the full proportion
of nitric acid, and each succeeding one less of the nitric acid, until
from the overflow of the last one the bisulphate of soda flows away
without any nitric acid. The nitrate of soda is placed in weighed
quantities in the hopper, whence it passes to the feeder. The feeder is a
miniature horizontal pug-mill, which receives the streams of sulphuric
acid and of nitrate, and after thoroughly mixing them, delivers them into
the still, where, under the influence of heat, they rapidly become a
homogeneous liquid, from which nitric acid continuously distils.

Mr Prentice says: "I may point out that while the ordinary process of
making nitric acid is one of fractional distillation by time, mine is
fractional distillation by space." "Instead of the operation being always
at the same point of space, but differing by the successive points of
time, I arrange for the differences to take place at different points of
space, and these differences exist at one and the same points of time." It
is possible with this plant to produce the full product of nitric acid of
a gravity of 1.500, or to obtain the acid of varying strengths from the
different still-heads. One of these stills, capable of producing about 4
tons of nitric acid per week, weighs less than 2 tons. It is claimed that
there is by their use a saving of more than two-thirds in fuel, and four-
fifths in condensing plant. Further particulars and illustrations will be
found in Mr Prentice's paper (_Journal of the Society of Chemical
Industry_, 1894, p. 323).




CHAPTER III.

_NITRO-CELLULOSE, &c._

Cellulose Properties--Discovery of Gun-Cotton--Properties of Gun-Cotton--
Varieties of Soluble and Insoluble Gun-Cottons--Manufacture of Gun-Cotton--
Dipping and Steeping--Whirling out the Acid--Washing--Boiling--Pulping--
Compressing--The Waltham Abbey Process--Le Bouchet Process--Granulation of
Gun-Cotton--Collodion-Cotton--Manufacture--Acid Mixture used--Cotton used,
&c.--Nitrated Gun-Cotton--Tonite--Dangers in Manufacture of Gun-Cotton--
Trench's Fire-Extinguishing Compound--Uses of Collodion-Cotton--Celluloid--
Manufacture, &c.--Nitro-Starch, Nitro-Jute, and Nitro-Mannite.


~The Nitro-Celluloses.~--The substance known as cellulose forms the
groundwork of vegetable tissues. The cellulose of the woody parts of
plants was at one time supposed to be a distinct body, and was called
lignine, but they are now regarded as identical. The formula of cellulose
is (C_{6}H_{10}O_{6})_{X}, and it is generally assumed that the molecular
formula must be represented by a multiple of the empirical formula,
C_{12}H_{20}O_{10} being often regarded as the minimum. The assumption is
based on the existence of a penta-nitrate and the insoluble and colloidal
nature of cellulose. Green (_Zeit. Farb. Text. Ind._, 1904, 3, 97)
considers these reasons insufficient, and prefers to employ the single
formula C_{6}H_{10}O_{5}. Cellulose can be extracted in the pure state,
from young and tender portions of plants by first crushing them, to
rupture the cells, and then extracting with dilute hydrochloric acid,
water, alcohol, and ether in succession, until none of these solvents
remove anything more. Fine paper or cotton wool yield very nearly pure
cellulose by similar treatment.

Cellulose is a colourless, transparent mass, absolutely insoluble in
water, alcohol, or ether. It is, however, soluble in a solution of
cuprammoniac solution, prepared from basic carbonate or hydrate of copper
and aqueous ammonia. The specific gravity of cellulose is 1.25 to 1.45.
According to Schulze, its elementary composition is expressed by the
percentage numbers:--

Carbon       44.0 per cent.  44.2 per cent.
Hydrogen      6.3    "        6.4    "
Oxygen       49.7    "       49.4    "

These numbers represent the composition of the ash free cellulose. Nearly
all forms of cellulose, however, contain a small proportion of mineral
matters, and the union of these with the organic portion of the fibre or
tissue is of such a nature that the ash left on ignition preserves the
form of the original. "It is only in the growing point of certain young
shoots that the cellulose tissue is free from mineral constituents"
(Hofmeister).

Cellulose is a very inert body. Cold concentrated sulphuric acid causes it
to swell up, and finally dissolves it, forming a viscous solution.
Hydrochloric acid has little or no action, but nitric acid has, and forms
a series of bodies known as nitrates or nitro-celluloses. Cellulose has
some of the properties of alcohols, among them the power of forming
ethereal salts with acids. When cellulose in any form, such as cotton, is
brought into contact with strong nitric acid at a low temperature, a
nitrate or nitro product, containing nitryl, or the NO_{2} group, is
produced. The more or less complete replacement of the hydroxylic hydrogen
by NO_{2} groups depends partly on the concentration of the nitric acid
used, partly on the duration of the action. If the most concentrated
nitric and sulphuric acids are employed, and the action allowed to proceed
for some considerable time, the highest nitrate, known as hexa-nitro-
cellulose or gun-cotton, C_{12}H_{14}O_{4}(O.NO_{2})_{6}, will be formed;
but with weaker acids, and a shorter exposure to their action, the tetra
and penta and lower nitrates will be formed.[A]

[Footnote A: The paper by Prof. Lunge, _Jour. Amer. Chem. Soc._, 1901,
23[8], 527-579, contains valuable information on this subject.]

Besides the nitrate, A. Luck[A] has proposed to use other esters of
cellulose, such as the acetate, benzoate, or butyrate. It is found that
cellulose acetate forms with nitro-glycerine a gelatinous body without
requiring the addition of a solvent. A sporting powder is proposed
composed of 75 parts of cellulose nitrate (13 per cent. N.) mixed with 13
parts of cellulose acetate.

[Footnote A: Eng. Pat. 24,662, 22nd November 1898.]

The discovery of gun-cotton is generally attributed to Schönbein (1846),
but Braconnot (in 1832) had previously nitrated starch, and six years
later Pelouse prepared nitro-cotton and various other nitro bodies, and
Dumas nitrated paper, but Schönbein was apparently the first chemist to
use a mixture of strong nitric and sulphuric acids. Many chemists, such as
Piobert in France, Morin in Russia, and Abel in England, studied the
subject; but it was in Austria, under the auspices of Baron Von Lenk, that
the greatest progress was made. Lenk used cotton in the form of yarn, made
up into hanks, which he first washed in a solution of potash, and then
with water, and after drying dipped them in the acids. The acid mixture
used consisted of 3 parts by weight of sulphuric to 1 part of nitric acid,
and were prepared some time before use. The cotton was dipped one skein at
a time, stirred for a few minutes, pressed out, steeped, and excess of
acid removed by washing with water, then with dilute potash, and finally
with water. Von Lenk's process was used in England at Faversham (Messrs
Hall's Works), but was given up on account of an explosion (1847).

Sir Frederick Abel, working at Stowmarket and Waltham Abbey, introduced
several very important improvements into the process, the chief among
these being pulping. Having traced the cause of its instability to the
presence of substances caused by the action of the nitric acid on the
resinous or fatty substances contained in the cotton fibre, he succeeded
in eliminating them, by boiling the nitro-cotton in water, and by a
thorough washing, after pulping the cotton in poachers.

Although gun-cottons are generally spoken of as nitro-celluloses, they are
more correctly described as cellulose nitrates, for unlike nitro bodies of
other series, they do not yield, or have not yet done so, amido bodies, on
reduction with nascent hydrogen.[A] The equation of the formation of
gun-cotton is as follows:--

2(C_{6}H_{10}O_{5}) + 6HNO_{3} = C_{12}H_{14}O_{4}(NO_{3})_{6} + 6OH_{2}.
    Cellulose.     Nitric Acid.      Gun-Cotton.                 Water.

The sulphuric acid used does not take part in the reaction, but its
presence is absolutely essential to combine with the water set free, and
thus to prevent the weakening of the nitric acid. The acid mixture used at
Waltham Abbey consists of 3 parts by weight of sulphuric acid of 1.84
specific gravity, and 1 part of nitric acid of 1.52 specific gravity. The
same mixture is also used at Stowmarket (the New Explosive Company's
Works). The use of weaker acids results in the formation of collodion-
cotton and the lower nitrates generally.

[Footnote A: "Cellulose," by Cross and Bevan, ed. by W.R. Hodgkinson, p.
9.]

The nitrate which goes under the name of gun-cotton is generally supposed
to be the hexa-nitrate, and to contain 14.14 per cent. of nitrogen; but a
higher percentage than 13.7 has not been obtained from any sample. It is
almost impossible (at any rate upon the manufacturing scale) to make pure
hexa-nitro-cellulose or gun-cotton; it is certain to contain several per
cents. of the soluble forms, i.e., lower nitrates. It often contains as
much as 15 or 16 per cent., and only from 13.07[A] to 13.6 per cent. of
nitrogen.

[Footnote A: Mr J.J. Sayers, in evidence before the court in the "Cordite
Case," says he found 15.2 and 16.1 per cent. soluble cotton, and 13.07 and
13.08 per cent. nitrogen in two samples of Waltham Abbey gun-cotton.]

A whole series of nitrates of cellulose are supposed to exist, the highest
member being the hexa-nitrate, and the lowest the mono-nitrate. Gun-cotton
was at one time regarded as the tri-nitrate, and collodion-cotton as the
di-nitrate and mono-nitrate, their respective formula being given as
follows:--

Mono-nitro-cellulose C_{6}H_{9}(NO_{2})O_{5}  =  6.763 per cent. nitrogen.
Di-nitro-cellulose   C_{6}H_{8}(NO_{2})_{2}O_{5} = 11.11   "        "
Tri-nitro-cellulose  C_{6}H_{7}(NO_{2})_{3}O_{5} = 14.14   "        "

But gun-cotton is now regarded as the hexa-nitrate, and collodion-cotton
as a mixture of all the other nitrates. In fact, chemists are now more
inclined to divide nitro-cellulose into the soluble and insoluble forms,
the reason being that it is quite easy to make a nitro-cellulose entirely
soluble in a mixture of ether-alcohol, and yet containing as high a
percentage of nitrogen as 12.6; whereas the di-nitrate[A] should
theoretically only contain 11.11 per cent. On the other hand, it is not
possible to make gun-cotton with a higher percentage of nitrogen than
about 13.7, even when it does not contain any nitro-cotton that is soluble
in ether-alcohol.[B] The fact is that it is not at present possible to
make a nitro-cellulose which shall be either entirely soluble or entirely
insoluble, or which will contain the theoretical content of nitrogen to
suit any of the above formulæ for the cellulose nitrates. Prof. G. Lunge
gives the following list of nitration products of cellulose:--

[Footnote A: The penta-nitrate C_{12}H_{15}O_{5}(NO_{3})_{5} = 12.75 per
cent. nitrogen.]

[Footnote B: In the Cordite Trial (1894) Sir F.A. Abel said, "Before 1888
there was a broad distinction between soluble and insoluble nitro-
cellulose, collodion-cotton being soluble (in ether-alcohol) and
gun-cotton insoluble." Sir H.E. Roscoe, "That he had been unable to make a
nitro-cotton with a higher nitrogen content than 13.7." And Professor G.
Lunge said, "Gun-cotton always contained soluble cotton, and _vice
versa_." These opinions were also generally confirmed by Sir E. Frankland,
Sir W. Crookes, Dr Armstrong, and others.]

Dodeca-nitro-cellulose C_{24}H_{28}O_{20}(NO_{2})_{12} = 14.16 per cent.
  nitrogen. (= old tri-nitro-cellulose)
Endeca-nitro-cellulose C_{24}H_{29}O_{20}(NO_{2})_{11} = 13.50 per cent.
  nitrogen.
Deca-nitro-cellulose   C_{24}H_{30}O_{20}(NO_{2})_{10} = 12.78 per cent.
  nitrogen.
Ennea-nitro-cellulose  C_{24}H_{31}O_{20}(NO_{2})_{9}  = 11.98 per cent.
  nitrogen.
Octo-nitro-cellulose   C_{24}H_{32}O_{20}(NO_{2})_{8} =  11.13 per cent.
  nitrogen. (= old di-nitro-cellulose)
Hepta-nitro-cellulose  C_{24}H_{33}O_{20}(NO_{2})_{7}  = 10.19 per cent.
  nitrogen.
Hexa-nitro-cellulose   C_{24}H_{34}O_{20}(NO_{2})_{6}  =  9.17 per cent.
  nitrogen.
Penta-nitro-cellulose  C_{24}H_{35}O_{20}(NO_{2})_{5}  =  8.04 per cent.
  nitrogen.
Tetra-nitro-cellulose  C_{24}H_{36}O_{20}(NO_{2})_{4}  =  6.77 per cent.
  nitrogen. (= old mono-nitro-cellulose)

It is not unlikely that a long series of nitrates exists. It is at any
rate certain that whatever strength of acids may be used, and whatever
temperature or other conditions may be present during the nitration, that
the product formed always consists of a mixture of the soluble and
insoluble nitro-cellulose.

Theoretically 100 parts of cotton by weight should produce 218.4 parts of
gun-cotton, but in practice the yield is a good deal less, both in the
case of gun-cotton or collodion-cotton. In speaking of soluble and
insoluble nitro-cellulose, it is their behaviour, when treated with a
solution consisting of 2 parts ether and 1 of alcohol, that is referred
to. There is, however, another very important difference, and that is
their different solubility in nitro-glycerine. The lower nitrates or
soluble form is soluble in nitro-glycerine under the influence of heat, a
temperature of about 50° C. being required. At lower temperatures the
dissolution is very imperfect indeed; and after the materials have been
left in contact for days, the threads of the cotton can still be
distinguished. The insoluble form or gun-cotton is entirely _insoluble_ in
nitro-glycerine. It can, however, be made to dissolve[A] by the aid of
acetone or acetic ether. Both or rather all the forms of nitro-cellulose
can be dissolved in acetone or acetic ether. They also dissolve in
concentrated sulphuric acid, and the penta-nitrate in nitric acid at about
80° or 90° C.

[Footnote A: Or rather to form a transparent jelly.]

The penta-nitrate may be obtained in a pure state by the following
process, devised by Eder:--The gun-cotton is dissolved in concentrated
nitric acid at 90° C., and reprecipitated by the addition of concentrated
sulphuric acid. After cooling to 0° C., and mixing with a larger volume of
water, the precipitated nitrate is washed with water, then with alcohol,
dissolved in ether-alcohol, and again precipitated with water, when it is
obtained pure. This nitrate is soluble in ether-alcohol, and slightly in
acetic acid, easily in acetone, acetic ether, and methyl-alcohol,
insoluble in alcohol. Strong potash (KOH) solution converts into the
di-nitrate C_{12}H_{18}O_{8}(NO_{3})_{2}. The hexa-nitrate is not soluble
in acetic acid or methyl-alcohol.

The lower nitrates known as the tetra- and tri-nitrates are formed
together when cellulose is treated with a mixture of weak acids, and
allowed to remain in contact with them for a very short time (twenty
minutes). They cannot be separated from one another, as they all dissolve
equally in ether-alcohol, acetic ether, acetic acid, methyl-alcohol,
acetone, amyl acetate, &c.

As far as the manufacture of explosive bodies is concerned, the two forms
of nitro-cellulose used and manufactured are gun-cotton or the hexa-
nitrate (once regarded as tri-nitro-cellulose), which is also known as
insoluble gun-cotton, and the soluble form of gun-cotton, which is also
known as collodion, and consists of a mixture of several of the lower
nitrates. It is probable that it chiefly consists, however, of the next
highest nitrate to gun-cotton, as the theoretical percentage of nitrogen
for this body,. the penta-nitrate, is 12.75 per cent., and analyses of
commercial collodion-cotton, entirely soluble in ether-alcohol, often give
as high a percentage as 12.6.

We shall only describe the manufacture of the two forms known as soluble
and insoluble, and shall refer to them under their better known names of
gun-cotton and collodion-cotton. The following would, however, be the
formulæ[A] and percentage of nitrogen of the complete series:--

Hexa-nitro-cellulose  C_{12}H_{14}O_{4}(NO_{3})_{6} 14.14 per cent.
  nitrogen.
Penta-nitro-cellulose C_{12}H_{15}O_{5}(NO_{3})_{5} 12.75 per cent.
  nitrogen.
Tetra-nitro-cellulose C_{12}H_{16}O_{6}(NO_{3})_{4} 11.11 per cent.
  nitrogen.
Tri-nitro-cellulose   C_{12}H_{17}O_{7}(NO_{3})_{3}  9.13 per cent.
  nitrogen.
Di-nitro-cellulose    C_{12}H_{18}O_{8}(NO_{3})_{2}  7.65 per cent.
  nitrogen.
Mono-nitrocellulose   C_{12}H_{19}O_{9}(NO_{3})      3.80 per cent.
  nitrogen.

[Footnote A: Berthelot takes C_{24}H_{40}O_{20} as the formula of
cellulose; and M. Vieille regards the highest nitrate as
(C_{24}H_{18}(NO_{3}H)_{11}O_{9}). _Compt. Rend._, 1882, p. 132.]

~Properties of Gun-Cotton.~--The absolute density of gun-cotton is 1.5.
When in lumps its apparent density is 0.1; if twisted into thread, 0.25;
when subjected, in the form of pulp, to hydraulic pressure, 1.0 to 1.4.
Gun-cotton preserves the appearance of the cotton from which it is made.
It is, however, harsher to the touch; it is only slightly hygroscopic (dry
gun-cotton absorbs 2 per cent. of moisture from the air). It possesses the
property of becoming electrified by friction. It is soluble in acetic
ether, amyl acetate, and acetone, insoluble in water, alcohol, ether,
ether-alcohol, methyl-alcohol, &c. It is very explosive, and is ignited by
contact with an ignited body, or by shock, or when it is raised to a
temperature of 172° C. It burns with a yellowish flame, almost without
smoke, and leaves little or no residue. The volume of the gases formed is
large, and consists of carbonic acid, carbonic oxide, nitrogen, and water
gas. Compressed gun-cotton when ignited often explodes when previously
heated to 100° C.

Gun-cotton kept at 80° to 100° C. decomposes slowly, and sunlight causes
it to undergo a slow decomposition. It can, however, be preserved for
years without undergoing any alteration. It is very susceptible to
explosions by influence. For instance, a torpedo, even placed at a long
distance, may explode a line of torpedoes charged with gun-cotton. The
velocity of the propagation of the explosion in metallic tubes filled with
pulverised gun-cotton has been found to be from 5,000 to 6,000 mms. per
second in tin tubes, and 4,000 in leaden tubes (Sebert).

Gun-cotton loosely exposed in the open air burns eight times as quickly as
powder (Piobert). A thin disc of gun-cotton may be fired into from a rifle
without explosion; but if the thickness of the disc be increased, an
explosion may occur. The effect of gun-cotton in mines is very nearly the
same as that of dynamite for equal weights. It requires, however, a
stronger detonator, and it gives rise to a larger quantity of carbonic
oxide gas. Gun-cotton should be neutral to litmus, and should stand the
Government heat test--temperature of 150° F. for fifteen minutes (see page
249). In the French Navy gun-cotton is submitted to a heat test of 65° C.
(= 149° F.) for eleven minutes. It should contain as small a percentage of
soluble nitro-cotton and of non-nitrated cotton as possible.

The products of perfectly detonated gun-cotton may be expressed by the
following equation:--

2C_{12}H_{14}O_{4}(NO_{3})_{6} = 18CO + 6CO_{2} + 14H_{2}O + 12N.

It does not therefore contain sufficient oxygen for the complete
combustion of its carbon. It is for this reason that when used for mining
purposes a nitrate is generally added to supply this defect (as, for
instance, in tonite). It tends also to prevent the evolution of the
poisonous gas, carbonic oxide. The success of the various gelatine
explosives is due to this fact, viz., that the nitro-glycerine has an
excess of oxygen, and the nitro-cotton too little, and thus the two
explosives help one another.

In practice the gases resulting from the explosion of gun-cotton are--
Carbonic oxide, 28.55; carbonic acid, 19.11; marsh gas (CH_{4}), 11.17;
nitric oxide, 8.83; nitrogen, 8.56; water vapour, 21.93 per cent. The late
Mr E.O. Brown, of Woolwich Arsenal, discovered that perfectly wet and
uninflammable compressed gun-cotton could be easily detonated by the
detonation of a priming charge of the dry material in contact with it.
This rendered the use of gun-cotton very much safer for use as a military
or mining explosive.

As a mining explosive, however, gun-cotton is now chiefly used under the
form of tonite, which is a mixture of half gun-cotton and half barium
nitrate. This material is sometimes spoken of as "nitrated gun-cotton."
The weight of gun-cotton required to produce an equal effect either in
heavy ordnance or in small arms is to the weight of gunpowder in the
proportion of 1 to 3, i.e., an equal weight of gun-cotton would produce
three times the effect of gunpowder. Its rapidity of combustion, however,
requires to be modified for use in firearms. Hence the lower nitrates are
generally used, or such compounds as nitro-lignose, nitrated wood, &c.,
are used.

The initial pressure produced by the explosion of gun-cotton is very
large, equal to 18,135 atmospheres, and 8,740 kilogrammes per square
centimetre for 1 kilo., the heat liberated being 1,075 calories (water
liquid), or 997.7 cals. (water gaseous), but the quantity of heat
liberated changes with the equation of decomposition. According to
Berthelot,[A] the heat of formation of collodion-cotton is 696 cals. for
1,053 grms., or 661 cals. for 1 kilo. The heat liberated in the total
combustion of gun-cotton by free oxygen at constant pressure is 2,633
cals. for 1,143 grms., or for 1 kilo. gun-cotton 2,302 cals. (water
liquid), or 2,177 cals. (water gaseous). The heat of decomposition of gun-
cotton in a closed vessel, found by experiment at a low density of charge
(0.023), amounts to 1,071 cals. for 1 kilo. of the substance, dry and free
from ash. To obtain the maximum effect of gun-cotton it must be used in a
compressed state, for the initial pressures are thereby increased. Wet
gun-cotton s much less sensitive to shock than dry. Paraffin also reduces
its liability to explode, so also does camphor.

[Footnote A: "Explosives and their Power," trans. by Hake and M'Nab.]

The substance known as celluloid, a variety of nitro-cellulose nearly
corresponding to the formula C_{24}H_{24}(NO_{3}H)_{8}O_{12}, to which
camphor and various inert substances are added, so as to render it
non-sensitive to shock, may be worked with tools, and turned in the lathe
in the same manner as ivory, instead of which material celluloid is now
largely used for such articles as knife handles, combs, &c. Celluloid is
very plastic when heated towards 150° C., and tends to become very
sensitive to shock, and in large quantities might become explosive during
a fire, owing to the general heating of the mass, and the consequent
evaporation of the camphor. When kept in the air bath at 135° C.,
celluloid decomposes quickly. In an experiment (made by M. Berthelot) in a
closed vessel at 135° C., and the density of the charge being 0.4, it
ended in exploding, developing a pressure of 3,000 kilos. A large package
of celluloid combs also exploded in the guard's van on one of the German
railways a few years ago. Although it is not an explosive under ordinary
circumstances, or even with a powerful detonator, considerable care should
be exercised in its manufacture.

~The Manufacture of Gun-Cotton.~--The method used for the manufacture of
gun-cotton is that of Abel (Spec. No. 1102, 20. 4. 65). It was worked out
chiefly at Stowmarket[A] and Waltham Abbey,[B] but has in the course of
time undergone several alterations. These modifications have taken place,
however, chiefly upon the Continent, and relate more to the apparatus and
machinery used than to any alteration in the process itself. The form of
cellulose used is cotton-waste,[C] which consists of the clippings and
waste material from cotton mills. After it has been cleaned and purified
from grease, oil, and other fatty substances by treatment with alkaline
solutions, it is carefully picked over, and every piece of coloured cotton
rag or string carefully removed. The next operation to which it is
submitted has for its object the opening up of the material. For this
purpose it is put through a carding machine, and afterwards through a
cutting machine, whereby it is reduced to a state suitable for its
subsequent treatment with acids, that is, it has been cut into short
lengths, and the fibres opened up and separated from one another.

[Footnote A: The New Explosive Co. Works.]

[Footnote B: Royal Gunpowder Factory.]

[Footnote C: Costs from £10 to £25 a ton. In his description of the
"Preparation of Cotton-waste for the Manufacture of Smokeless Powder," A.
Hertzog states that the German military authorities require a cotton which
when thrown into water sinks in two minutes; when nitrated, does not
disintegrate; when treated with ether, yields only 0.9 per cent. of fat;
and containing only traces of chlorine, lime, magnesia, iron, sulphuric
acid, and phosphoric acid. If the cotton is very greasy, it must be first
boiled with soda-lye under pressure, washed, bleached with chlorine,
washed, treated with sulphuric acid or HCl, again washed, centrifugated,
and dried; if very greasy indeed a preliminary treatment with lime-water
is desirable. See also "Inspection of Cotton-Waste for Use in the
Manufacture of Gun-cotton," by C.E. Munro, _Jour. Am. Chem. Soc._, 1895,
17, 783.]

~Drying the Cotton.~--This operation is performed in either of two ways.
The cotton may either be placed upon shelves in a drying house, through
which a current of hot air circulates, or dried in steam-jacketed
cylinders. It is very essential that the cotton should be as dry as
possible before dipping in the acids, especially if a wholly "insoluble"
nitro-cellulose is to be obtained. After drying it should not contain more
than 0.5 per cent. of moisture, and less than this if possible. The more
general method of drying the cotton is in steam-jacketed tubes, i.e.,
double cylinders of iron, some 5 feet long and 1-1/2 foot wide. The cotton
is placed in the central chamber (Fig. 10), while steam is made to
circulate in the surrounding jacket, and keeps the whole cylinder at a
high temperature (steam pipes may be coiled round the outside of an iron
tube, and will answer equally well). By means of a pipe which communicates
with a compressed air reservoir, a current of air enters at the bottom,
and finds its way up through the cotton, and helps to remove the moisture
that it contains. The raw cotton generally contains about 10 per cent. of
moisture and should be dried until it contains only 1/2 per cent. or less.
For this it will generally have to remain in the drying cylinder for about
five hours. At the end of that time a sample should be taken from the
_top_ of the cylinder, and dried in the water oven (100° C.[A]) for an
hour to an hour and a half, and re-weighed, and the moisture then
remaining in it calculated.

[Footnote A: It is dried at 180° C. at Waltham Abbey, in a specially
constructed drying chamber.]

[Illustration: FIG. 10.--COTTON DRIER.]

It is very convenient to have a large copper water oven, containing a lot
of small separate compartments, large enough to hold about a handful of
the cotton, and each compartment numbered, and corresponding to one of the
drying cylinders. The whole apparatus should be fixed against the wall of
the laboratory, and may be heated by bringing a small steam pipe from the
boiler-house. It is useful to have a series of copper trays, about 3
inches by 6 inches, numbered to correspond to the divisions in the steam
oven, and exactly fitting them. These trays can then be taken by a boy to
the drying cylinders, and a handful of the cotton from each placed in
them, and afterwards brought to the laboratory and weighed (a boy can do
this very well), placed in their respective divisions of the oven, and
left for one to one and a half hours, and re-weighed.

When the cotton is found to be dry the bottom of the drying cylinder is
removed, and the cotton pushed out from the top by means of a piece of
flat wood fixed on a broom-handle. It is then packed away in galvanised-
iron air-tight cases, and is ready for the next operation. At some works
the cotton is dried upon shelves in a drying house through which hot air
circulates, the shelves being of canvas or of brass wire netting. The hot
air must pass under the shelves and through the cotton, or the process
will be a very slow one.

~Dipping and Steeping.~--The dry cotton has now to be nitrated. This is
done by dipping it into a mixture of nitric and sulphuric acids. The acids
used must be strong, that is, the nitric acid must be at least of a
gravity of 1.53 to 1.52, and should contain as little nitric oxide as
possible. The sulphuric acid must have a specific gravity of 1.84 at 15°
C., and contain about 97 per cent. of the mono-hydrate (H_{2}SO_{4}). In
fact, the strongest acids obtainable should be used when the product
required is gun-cotton, i.e., the highest nitrate.

The sulphuric acid takes no part in the chemical reaction involved, but is
necessary in order to combine with the water that is liberated in the
reaction, and thus to maintain the strength of the nitric acid. The
reaction which takes place is the following:--

2(C_{6}H_{10}O_{5}) + 6HNO_{3} = C_{12}H_{14}(NO_{3})_{6} + 6 H_{2}O.
         324            378    =         594                  108.
        Cellulose.                    Gun-Cotton.

Theoretically,[A] therefore, 1 part of cellulose should form 1.8 part of
gun-cotton. Practically, however, this is never obtained, and 1.6 lb. from
1 lb. of cellulose is very good working. The mixture of acids used is
generally 1 to 3, or 25 per cent. nitric acid to 75 per cent. sulphuric
acid.

[Footnote A: (594 x 1)/324= 1.83.]

[Illustration: FIG. 11.--TANK FOR DIPPING COTTON.]

[Illustration: FIG. 12.--THE COOLING PITS.]

The dipping is done in cast-iron tanks (Fig. 11), a series of which is
arranged in a row, and cooled by a stream of cold water flowing round
them. The tanks hold about 12 gallons, and the cotton is dipped in
portions of 1 lb. at a time. It is thrown into the acids, and the workman
moves it about for about three minutes with an iron rabble. At the end of
that time he lifts it up on to an iron grating, just above the acids,
fixed at the back of the tank, where by means of a movable lever he gently
squeezes it, until it contains about ten times its weight of acids (the 1
lb. weighs 10 lbs.). It is then transferred to earthenware pots to steep.

[Illustration: FIG. 13.--COTTON STEEPING POT.]

~Steeping.~--The nitrated cotton, when withdrawn from the dipping tanks,
and still containing an excess of acids, is put into earthenware pots of
the shape shown in Figs. 12 and 13. The lid is put on, and the pots placed
in rows in large cooling pits, about a foot deep, through which a stream
of water is constantly flowing. These pits form the floor of the steeping
house. The cotton remains in these pots for a period of forty-eight hours,
and must be kept cool. Between 18° and 19° C. is the highest temperature
desirable, but the cooler the pots are kept the better. At the end of
forty-eight hours the chemical reaction is complete, and the cotton is or
should be wholly converted into nitro-cellulose; that is, there should be
no unnitrated cotton.

[Illustration: FIG. 14.--HYDRO-EXTRACTOR.]

~Whirling Out the Acid.~--The next operation is to remove the excess of
acid. This is done by placing the contents of two or three or more pots
into a centrifugal hydro-extractor (Fig. 14), making 1,000 to 1,500
revolutions per minute. The hydro-extractor consists of a machine with
both an inner cylinder and an outer one, both revolving in concert and
driving outwardly the liquid to the chamber, from which it runs away by a
discharge pipe. The wet cotton is placed around the inner cone. The
cotton, when dry, is removed, and at once thrown into a large tank of
water, and the waste acids are collected in a tank.[A]

[Footnote A: Care must be taken in hot weather that the gun-cotton does
not fire, as it does sometimes, directly the workman goes to remove it
after the machine is stopped. It occurs more often in damp weather. Dr
Schüpphaus, of Brooklyn, U.S.A., proposes to treat the waste acids from
the nitration of cellulose by adding to them sulphuric anhydride and
nitric acid. The sulphuric anhydride added converts the water liberated
from the cellulose into sulphuric acid.]

~Washing.~--The cotton has now to be carefully washed. This is done in a
large wooden tank filled with water. If, however, a river or canal runs
through the works, a series of wooden tanks, the sides and bottoms of
which are pierced with holes, so as to allow of the free circulation of
water, should be sunk into a wooden platform that overhangs the surface of
the river in such a way that the tanks are immersed in the water, and of
course always full. During the time that the cotton is in the water a
workman turns it over constantly with a wooden paddle. A stream of water,
in the form of a cascade, should be allowed to fall into these tanks. The
cotton may then be thrown on to this stream of water, which, falling some
height, at once carries the cotton beneath the surface of the water. This
proceeding is necessary because the cotton still retains a large excess of
strong acids, and when mixed with water gives rise to considerable heat,
especially if mixed slowly with water. After the cotton has been well
washed, it is again wrung out in a centrifugal machine, and afterwards
allowed to steep in water for some time.

[Illustration: FIG. 15_a_.--THE BEATER FOR GUN-COTTON.]

~Boiling.~--The washed cotton is put into large iron boilers with plenty
of water, and boiled for some time at 100° C. In some works lead-lined
tanks are used, into which a steam pipe is led. The soluble impurities of
unstable character, to which Sir F.A. Abel traced the liability of gun-
cotton to instability, are thereby removed. These impurities consist of
the products formed by the action of nitric acid on the fatty and resinous
substances contained in the cotton fibres. The water in the tanks should
be every now and again renewed, and after the first few boilings the water
should be tested with litmus paper until they are no longer found to be
acid.

[Illustration: FIG. 15_b_.--WHEEL OF BEATER.]

~Pulping.~--The idea of pulping is also due to Abel. By its means a very
much more uniform material is obtained. The process is carried out in an
apparatus known as a "Beater" or "Hollander" (Fig. 15, _a, b_). It
consists of a kind of wooden tank some 2 or 3 feet deep of an oblong
shape, in which a wheel carrying a series of knives is made to revolve,
the floor of the tank being sloped up so as to almost touch the revolving
wheels. This part of the floor, known as the "craw," is a solid piece of
oak, and a box of knives is fixed into it, against which the knives in the
revolving wheel are pressed. The beater is divided into two parts--the
working side, in which the cotton is cut and torn between the knife edges
in the revolving cylinder and those in the box; and the running side, into
which the cotton passes after passing under the cylinder. The wheel is
generally boxed in to prevent the cotton from being thrown out during its
revolution. The cotton is thus in constant motion, continually travelling
round, and passing between the knives in the revolving cylinder and those
in the box fixed in the wooden block beneath it. The beater is kept full
of water, and the cotton is gradually reduced to a condition of pulp. The
wheel revolves at the rate of 100 to 150 times a minute.

[Illustration: FIG. 16_a_.--POACHER FOR WASHING GUN-COTTON.]

[Illustration: FIG. 16_b_.--PLAN OF THE POACHER.]

[Illustration: FIG. 16_c_.--ANOTHER FORM OF POACHER.]

When the gun-cotton is judged to be sufficiently fine, the contents of the
beater are run into another very similar piece of machinery, known as the
"poacher" (Fig. 16, _a, b, c_), in which the gun-cotton is continuously
agitated together with a large quantity of water, which can be easily run
off and replaced as often as required. When the material is first run into
the poacher from the beater, the water with which it is then mixed is
first run away and clean water added. The paddle wheel is then set in
motion, and at intervals fresh water is added. There is a strainer at the
bottom of the poacher which enables the water to be drawn off without
disturbing the cotton pulp. After the gun-cotton has been in the poacher
for some time, a sample should be taken by holding a rather large mesh
sieve in the current for a minute or so. The pulp will thus partly pass
through and partly be caught upon the sieve, and an average sample will be
thus obtained. The sample is squeezed out by hand, bottled, and taken to
the laboratory to be tested by the heat test for purity. It first,
however, requires to be dried. This is best done by placing the sample
between coarse filter paper, and then putting it under a hand-screw press,
where it can be subjected to a tolerably severe pressure for about three
minutes. It is then rubbed up very finely with the hands, and placed upon
a paper tray, about 6 inches by 4-1/2 inches, which is then placed inside
a water oven upon a shelf of coarse wire gauze, the temperature of the
oven being kept as near as possible to 120° F. (49° C.), the gauze shelves
in the oven being kept about 3 inches apart. The sample is allowed to
remain at rest for fifteen minutes in the oven, the door of which is left
wide open. After the lapse of fifteen minutes the tray is removed and
exposed to the air of the laboratory (away from acid fumes) for two hours,
the sample being at some point within that time rubbed upon the tray with
the hand, in order to reduce it to a fine and uniform state of division.
Twenty grains (1.296 grm.) are used for the test. (See Heat Test, page
249.)

If the gun-cotton sample removed from the poacher stands the heat test
satisfactorily, the machine is stopped, and the water drained off. The
cotton is allowed some little time to drain, and is then dug out by means
of wooden spades, and is then ready for pressing. The poachers hold about
2,000 lbs. of material, and as this represents the products of many
hundred distinct nitrating operations, a very uniform mixture is obtained.
Two per cent. of carbonate of soda is sometimes added, but it is not
really necessary if the cotton has been properly washed.

~Compressing Gun-Cotton.~--The gun-cotton, in the state in which it is
removed from the poacher, contains from 28 to 30 per cent. of water. In
order to remove this, the cotton has to be compressed by hydraulic power.
The dry compressed gun-cotton is packed in boxes containing 2,500 lbs. of
dry material. In order to ascertain how much of the wet cotton must be put
into the press, it is necessary to determine the percentage of water. This
may be done by drying 2,000 grains upon a paper tray (previously dried at
100° C.) in the water oven at 100° C. for three hours, and re-weighing and
calculating the percentage of water. It is then easy to calculate how much
of the wet gun-cotton must be placed in the hopper of the press in order
to obtain a block of compressed cotton of the required weight. Various
forms of presses are used, and gun-cotton is sent out either as solid
blocks, compressed discs, or in the form of an almost dry powder, in zinc-
lined, air-tight cases. The discs are often soaked in water after
compression until they have absorbed 25 per cent. of moisture.

[Illustration: FIG. 17.--OLD METHOD. 100 PIECES.]

[Illustration: FIG. 18.--NEW METHOD. ONE SOLID BLOCK.]

At the New Explosives Company's Stowmarket Works large solid blocks of
gun-cotton are pressed up under a new process, whereby blocks of gun-
cotton, for use in submarine mines or in torpedo warheads, are produced.
Large charges of compressed gun-cotton have hitherto been built up from a
number of suitably shaped charges of small dimensions (Fig. 17), as it has
been impossible to compress large charges in a proper manner. The
formation of large-sized blocks of gun-cotton was the invention of Mr A.
Hollings. Prior to the introduction of this method, 8 or 9 lbs. had been
the limit of weight for a block. This process has been perfected at the
Stowmarket factory, where blocks varying from the armour-piercing shell
charge of a few ounces up to blocks of compressed gun-cotton mechanically
true, weighing 4 to 5 cwts. for torpedoes or submarine mines, are now
produced. At the same time the new process ensures a uniform density
throughout the block, and permits of any required density, from 1.4
downwards, being attained; it is also possible exactly to regulate the
percentage of moisture, and to ensure its uniform distribution. The
maximum percentage of moisture depends, of course, upon the density. By
the methods of compression gun-cotton blocks hitherto employed, blocks of
a greater thickness than 2 inches, or of a greater weight than 9 lbs.,
could not be made, but with the new process blocks of any shape, size,
thickness, or weight that is likely to be required can be made readily and
safely. The advantages which are claimed for the process may be enumerated
as follows:--(1.) There is no space wasted, as in the case with built-up
charges, through slightly imperfect contact between the individual blocks,
and thus either a heavier charge--i.e., about 15 per cent. more gun-
cotton--can be got into the same space, or less space will be occupied by
a charge of a given weight. (2.) The metallic cases for solid charges may
be much lighter than for those built-up, since with the former their
function is merely to prevent the loss of moisture from wet gun-cotton, or
to prevent the absorption of moisture by dry gun-cotton. They can thus be
made lighter, as the solid charge inside will prevent deformation during
transport. With built-up charges the case must be strong enough to prevent
damage, either to itself or to the charge it contains. For many uses a
metal case, however light, may be discarded, and one of a thin waterproof
material substituted. (3.) The uniform density of charges made by this
process is very favourable to the complete and effective detonation of the
entire mass, and to the presence of the uniform amount of moisture in
every part of the charge. (4.) Any required density, from the maximum
downwards, may be obtained with ease, and any required amount of moisture
left in the charge. These points are of great importance in cases where,
like torpedo charges, it is essential to have the centre of gravity of the
charge in a predetermined position both vertically and longitudinally, and
the charge so fixed in its containing case that the centre of gravity
cannot shift. The difficulty of ensuring this with a large torpedo charge
built up from a number of discs and segments is well known. Even with
plain cylindrical or prismatic charges a marked saving in the process of
production is effected by this new system. The charges being in one block
they are more easily handled for the usual periodical examination, and
they do not break or chafe at the edges, as in the case of discs and cubes
in built-up charges. A general view of the press is given in Fig. 19. The
gun-cotton in a container is placed on a cradle fixed at an angle to the
press. The mould is swivelled round, and the charge pushed into it with a
rammer, and it is then swivelled back into position. The mould is made up
of a number of wedge pieces which close circumferentially on the enclosed
mass, which is also subjected to end pressure. Holes are provided for the
escape of water.

[Illustration: FIG. 19.--A 4-CWT. BLOCK OF GUN-COTTON BEING TAKEN FROM
HYDRAULIC PRESS.]

~The Waltham Abbey Process.~--At the Royal Gunpowder Factory, Waltham
Abbey, the manufacture of gun-cotton has been carried out for many years.
The process used differs but little from that used at Stowmarket. The
cotton used is of a good quality, it is sorted and picked over to remove
foreign matters, &c., and is then cut up by a kind of guillotine into
2-inch lengths. It is then dried in the following manner. The cotton is
placed upon an endless band, which conducts it to the stove, or drying
closet, a chamber heated by means of hot air and steam traps to about
180° F.; it falls upon a second endless band, placed below the first; it
travels back again the whole length of the stove, and so on until
delivered into a receptacle at the bottom of the farther end, where it is
kept dry until required for use. The speed at which the cotton travels is
6 feet per minute, and as the length of the band travelled amounts to 126
feet, the operation of drying takes twenty-one minutes. One and a quarter
lb. are weighed out and placed in a tin box; a truck, fitted to receive a
number of these boxes, carries it along a tramway to a cool room, where it
is allowed to cool.

~Dipping.~--Mixed acids are used in the proportion of 1 to 3, specific
gravity nitric acid 1.52, and sulphuric acid 1.84. The dipping tank is
made of cast iron, and holds 220 lbs. of mixed acids, and is surrounded on
three sides by a water space in order to keep it cool. The mixed acids are
stored in iron tanks behind the dipping tanks, and are allowed to cool
before use. During the nitration, the temperature of the mixed acids is
kept at 70° F., and the cotton is dipped in quantities of 1-1/2 lb. at a
time. It is put into a tin shoot at the back of the dipping tank, and
raked into the acids by means of a rabble. It remains in the acids for
five or six minutes, and is then removed to a grating at the back, pressed
and removed. After each charge of cotton is removed from the tank, about
14 lbs. of fresh mixed acids are added, to replace amount removed by
charge. The charge now weighs, with the acids retained by it, 15 lbs.; it
is now placed in the pots, and left to steep for at least twenty-four
hours, the temperature being kept as low as possible, to prevent the
formation of soluble cotton, and also prevent firing. The proportion of
soluble formed is likely to be higher in hot weather than cold. The pots
must be covered to prevent the absorption of moisture from the air, or the
accidental entrance of water, which would cause decomposition, and
consequent fuming off, through the heat generated by the action of the
water upon the strong acids.

The excess of acids is now extracted by means of hydro-extractors, as at
Stowmarket. They are worked at 1,200 revolutions per minute, and whirled
for five minutes (10-1/2 lbs. of waste acids are removed from each charge
dipped). The charge is then washed in a very similar manner to that
previously described, and again wrung out in a centrifugal extractor
(1,200 revolutions per minute). The gun-cotton is now boiled by means of
steam in wooden tanks for eight hours; it is then again wrung out in the
extractors for three minutes, boiled for eight hours more, and again wrung
out; it is then sent to the beater and afterwards to the poacher. The
poachers hold 1,500 gals. each, or 18 cwt. of cotton. The cotton remains
six hours in the poachers. Before moulding, 500 gals. of water are run
into the poacher, and 500 gals. of lime water containing 9 lbs. of whiting
and 9 gals. of a caustic soda solution. This mixture is of such a strength
that it is calculated to leave in the finished gun-cotton from 1 to 2 per
cent. of alkaline matter.

By means of vacuum pressure, the pulp is now drawn off and up into the
stuff chest--a large cylindrical iron tank, sufficiently elevated on iron
standards to allow room for the small gauge tanks and moulding apparatus
below. It holds the contents of one poacher (18 cwt.), and is provided
with revolving arms to keep the pulp stirred up, so that it may be
uniformly suspended in water.

Recently a new process, invented by J.M. and W.T. Thomson (Eng. Pat. No.
8,278, 1903), has been introduced at the Waltham Abbey Factory. The object
of this invention is the removal of the acids of nitration from the
nitrated material after the action has been completed, and without the aid
of moving machinery, such as presses, rollers, centrifugals, and the like.
The invention consists in the manufacture of nitrated celluloses by
removing the acids from the nitrated cellulose directly by displacement
without the employment of either pressure or vacuum or mechanical
appliances of any kind, and at the same time securing the minimum dilution
of the acids. It was found that if water was carefully run on to the
surface of the acids in which the nitro-cellulose is immersed, and the
acids be slowly drawn off at the bottom of the vessel, the water displaces
the acid from the interstices of the nitro-cellulose without any
undesirable rise in temperature, and with very little dilution of the
acids. By this process almost the whole of the acid is recovered in a
condition suitable for concentration, and the amount of water required for
preliminary washing is very greatly reduced. The apparatus which is used
for the purpose consists of a cylindrical or rectangular vessel
constructed with a perforated false bottom and a cock at its lowest point
for running off the liquid. Means are also provided to enable the
displacing water to be run quietly on to the surface of the nitrating
acids.[A]

[Footnote A: In a further patent (Eng. Pat. 7,269, 1903, F.L. Natham),
J.M. Thomson and W.T. Thomson propose by use of alcohol to replace the
water, used in washing nitro-cellulose, and afterward to remove the
alcohol by pressing and centrifuging.]

The apparatus is shown in Fig. 2O, side elevation, and in Fig. 21 a plan
of the nitrating vessel and its accessories is given. In Fig. 20 is shown
in sectional elevation one of the trough devices for enabling liquids to
be added to those in the nitrating vessel without substantial disturbance.

[Illustration: FIG. 20.--SECTIONAL ELEVATION OF THOMSON'S APPARATUS, _a_,
Tank; _b_, False Bottom; _c_, Bottom; _c'_, Ribs; _d_, Draining Outlet;
_e_, Grid; _f_, Troughs, with Aprons _g_; _h_, Pipe, with Branches _h'_,
leading to Troughs, _f_; _k'_, Outlet Pipe of the Sulphuric Acid Tank _k_;
_l_, Water Supply Pipe; _m_, Pipe to supply of Nitrating Acids; _o_,
Perforations of Trough _f_; _p_, Cock to remove Acid.]

In carrying out this invention a rectangular lead-lined or earthenware
tank _a_ is employed, having a false bottom _b_, supported by ribs _c'_,
over the real bottom _c_, which slopes down to a draining outlet pipe _d_,
provided with a perforated grid or plate _e_, adapted to prevent choking
of the outlet. Suitably supported near the top of the vessel _a_ are
provided two troughs, _f_ having depending aprons _g_, a pipe _h_ has two
branches _h'_, leading to the troughs, _f_. This pipe _h_ is adapted to be
connected by a rubber pipe either to the outlet pipe _k'_ of the sulphuric
acid tank _k_ or the water supply pipe _l_. The nitrating acids are
supplied through the pipe _m_. A charge of mixed nitrating acids is
introduced into the vessel _a_ say up to the level _n_, and the dry
cellulose thrown into the acids in small quantities at a time, being
pushed under the surface in the usual way.

[Illustration: FIG. 21.--PLAN OF THOMSON'S APPARATUS, _a_, Tank; _b_,
False Bottom; _c'_, Ribs; _e_, Grid; _f_, Troughs; _g_, Aprons; _h_ and
_h'_, Pipes to Troughs _f_; _k_, Sulphuric Acid Tank; _m_, Pipe to
Nitrating Acids Tank; _o_, Perforations of Troughs; _p_, Cock to remove
Acid.]

A thin layer, say half an inch, of a suitable liquid, preferably sulphuric
acid, of a gravity not exceeding that of the waste acid to be produced, is
run carefully on the top of the acids by means of the troughs _f_, which
are perforated as shown at _o_, so that the sulphuric acid runs down the
aprons _g_, and floats on the nitrating acids. The whole is then allowed
to stand till nitration has been completed. Water is then supplied to the
troughs by way of the pipes _l_, _h_, and _h'_, and is allowed to float
very gently over the surface of the sulphuric acid, and when a sufficient
layer has been formed, the cock _p_ at the bottom of the apparatus is
opened, and the acid slowly drawn off, water being supplied to maintain
the level constant. It is found that the rate of displacement of the acids
is a factor which exerts a considerable influence on the properties of the
resulting nitro-cellulose, and affords a means of regulating the
temperature of displacement. A rate of displacement which has been found
suitable is about two inches in depth of the vessel per hour when treating
highly nitrated celluloses, but this rate may, in some cases, be
considerably increased. The flow of water at the top of the apparatus is
regulated so that a constant level is maintained. By this means the water
gradually and entirely displaces the acids from the interstices of the
nitro-cellulose, the line of separation between the acids and the water
being fairly sharply defined throughout. The flow of water is continued
until that issuing at the bottom is found to be free from all trace of
acid. The purification of the nitro-cellulose is then proceeded with as
usual, either in the same vessel or another.

In the process above described, the object of the introduction of a small
layer of sulphuric acid is mainly to prevent the fuming which would
otherwise take place, and is not essential, as it is found it can be
omitted without any deleterious effect. In order to use the mixed acids in
the most economical manner, the waste acid from a previous operation may
be used for a first nitration of the cellulose; being afterwards displaced
with fresh acids which carry the nitration to the required degree before
they are in turn displaced by water. The apparatus may be used merely for
the removal of the acid, in which case the nitration is carried out in
other vessels in the usual way, and the nitro-cellulose removed to the
displacement apparatus where it is just covered with waste acid, and the
displacement then proceeded with as above described. In some cases the
process is carried out in an ordinary nitrating centrifugal, using the
latter to effect preliminary drying after acid extraction. This gives a
great advantage over the usual method of working ordinary centrifugal
nitrating apparatus, because the acid being removed before the centrifugal
is run, practically all danger of firing therein disappears, and a greater
proportion of the waste acid is recovered.

In some cases the acids and water may be supplied by perforated pipes,
lying along the edges of the nitrating vessel, and these edges may, if
desired, be themselves made inclined, like the sides of the troughs _f_.
In the case of effecting nitration in centrifugals as above, the
displacing sulphuric acid and water may thus be supplied round the edges
of the machines, or removal troughs such as _f_ may be used. It will be
obvious that any inert liquid of suitable specific gravity may be used
instead of sulphuric acid, as a separation layer.

~Moulding.~--By means of the small measuring tank above referred to, the
gun-cotton pulp is drawn off from the stuff chest, and run into moulds of
the shapes and sizes required. Thence a large proportion of the water is
drawn off by means of tubes connected with the vacuum engine, the moulds
having bottoms of fine wire gauze, in order to prevent the pulp from
passing through. Hydraulic pressure of about 34 lbs. on the square inch is
then applied, which has the effect of compressing the pulp into a state in
which it has sufficient consistency to enable it to be handled with care,
and also expels a portion of the remaining water.

~Compressing.~--The moulded gun-cotton is now taken to the press house,
which is situated at some distance from the rest of the factory. Here the
moulds are subjected to powerful hydraulic pressure, from 5 to 6 tons per
square inch, and is compressed to one-third of its previous bulk. The
slabs or discs thus formed are kept under pressure for a short time, not
exceeding a minute and a half, to give the requisite density. It should,
when removed, be compact, and just sink in water, and should perceptibly
yield to the pressure of the fingers. There are perforations in the press
blocks, to allow of the escape of gases, if formed, by reason of
sufficient heat being generated. The men working the press are placed
under cover, behind strong rope mantlets having eye tubes which command a
view of the press.

~Packing.~--The finished slabs and discs are dipped into a solution of
soda and carbolic acid, and packed in special wood metal-lined cases. When
it is to be sent abroad, the metal lining, which is made of tinned copper,
is soldered down, but both the outer wooden and inner metal cases are
fitted with air-tight screw-plugs, so that when necessary water can be
added without unfastening the cases.

~Reworked gun-cotton~ does not make such good discs as new pulped gun-
cotton, probably because the fibrous tenacity of the gun-cotton has been
destroyed by the amount of pressure it has previously undergone, so that
when repulped it resembles fine dust, and a long time is required to press
it into any prescribed form. It is generally boiled for eight hours to
open up the fibre and remove alkali, then broken up by hand with wooden
mallets, pulped, and then used with fresh gun-cotton in the proportion of
1 to 5 parts.

~Manufacture at Le Bouchet.~--At Le Bouchet gun-cotton was made thus:--200
grms. of cotton were steeped for an hour in 2 litres of a mixture of 1
volume concentrated nitric and 2 volumes sulphuric acid. The cotton was
then removed and pressed, whereby 7/10ths of the waste acids was
recovered. After this it was washed for one to one and a half hours in
running water, strongly pressed again; allowed to lie for twenty-four
hours in wood-ash lye; then well washed in running water; pressed, and
finally dried on a wide linen sheet, through which was forced air heated
to 60° C. The average yield from 100 parts of cotton was 165 parts of gun-
cotton. The strong pressings of the gun-cotton, while still impregnated
with acids, caused subsequent washings to be difficult and laborious.

~Granulation of Gun-Cotton.~--Gun-cotton is often required in the
granulated form for use either alone or with some form of smokeless
powder. This is done under the patent of Sir Frederick Abel in the
following manner:--The gun-cotton from the poacher is placed in a
centrifugal machine, very similar to the hydro-extractors before
mentioned, and used for wringing out the acids. In this machine it loses
water until it only contains 33 per cent., and is at the same time reduced
to a more or less fibrous state. It is then taken to the granulating room,
where it is first passed through sieves or perforations, which break up
the mass into little pieces like shot. The material is then transferred to
a revolving drum made of wood or stout leather, which is kept constantly
revolving for some time. The material is occasionally sprinkled with
water. The drum in turning, of course, carries the granules partially
round with it, but the action of gravity causes them to descend constantly
to the lowest point, and thus to roll over one another continually. The
speed of the drum must not be too rapid. None of the granules must be
carried round by centrifugal force, but it must be fast enough to carry
them some little distance up the side of the drum. After removal from the
drum the granules are dried upon shelves in the drying house.

Gun-cotton is also dissolved in acetone or acetic ether until it has taken
the form of a jelly. It is then rolled into thin sheets, and when dry cut
up into little squares. In the manufacture of smokeless powders from
nitro-cellulose, nitro-lignine, &c., the various substances are mixed with
the gun-cotton or collodion-cotton before granulating.

~Collodion-Cotton.~--In the manufacture of collodion or soluble cotton the
finer qualities of cotton-waste are used and the acids used in the dipping
tanks are much weaker. The manufacture of collodion-cotton has become of
more importance than gun-cotton, by reason of its use for the manufacture
of the various forms of gelatine, such as gelatine dynamite, gelignite,
forcite, &c., and also on account of its extensive use in the manufacture
of many of the smokeless powders. It is also used for the manufacture of
"collodion," which is a solution of collodion-cotton in ether-alcohol; for
the preparation of celluloid, and many other purposes. It is less
explosive than gun-cotton, and consists of the lower nitrates of
cellulose. It is soluble in nitro-glycerine, and in a mixture of 2 parts
of ether and 1 of alcohol; also in acetone, acetic ether, and other
solvents. MM. Ménard and Domonte were the first to prepare a soluble gun-
cotton, and its investigation was carried on by Béchamp, who showed that
its properties and composition were different to those of gun-cotton.

~Manufacture.~--The cotton used is cotton-waste.[A] It is thought by some
that Egyptian cotton is preferable, and especially long fibre varieties.
The strength of the acids used is, however, of more importance than the
quality of the cotton. The percentage composition of the acid mixture
which gives the best results is as follows:--Nitric acid, 23 per cent.;
sulphuric acid, 66 per cent.; and water, 11 per cent; and has a specific
gravity of 1.712 (about). It can be made by mixing sulphuric acid of
specific gravity 1.84 with nitric acid of specific gravity 1.368 in the
proportions of 66 per cent. and 34 per cent. respectively. (The production
of the penta-nitro-cellulose is aimed at if the collodion-cotton is for
use as an explosive.) If the acids are much weaker than this, or potassium
nitrate and sulphuric acid is used, the lower nitrates will be formed. The
product, while being entirely soluble in ether-alcohol or nitro-glycerine,
will have a low nitrogen content, whereas a material with as high a
nitrogen as 12 or 12.6 is to be aimed at.

[Footnote A: Raw cotton is often used.]

The cotton should not be allowed to remain in the dipping tanks for more
than five minutes, and the acid mixture should be kept at a temperature of
28° C. or thereabouts; and the cotton should be removed after a few
minutes, and should not be pressed out, as in the case of gun-cotton, but
at once transferred to the pots and allowed to steep for forty-eight
hours. (Some prefer twenty-four hours, but there is more chance in this
case of the product containing non-nitrated cellulose.) When the nitration
is complete, the collodion-cotton is removed from the pots, and treated in
exactly the same manner as described under gun-cotton. The produce should
be entirely soluble in ether-alcohol and nitro-glycerine, and contain as
near 12.7 per cent. of nitrogen as possible. The theoretical nitrogen is
for the penta-nitro-cellulose 12.75 per cent. This will, however, seldom
if ever be obtained. The following are some of the results I have obtained
from different samples:--

                   Nitrogen.
               (1.)  (2.)  (3.)
German make   11.64  11.48 11.49 per cent.
Stowmarket    12.57  12.60 11.22    "
Walsrode      11.61  12.07 11.99    "
Faversham     12.14  11.70 11.60    "

and the following was the analysis of a sample (No. 1) of German-made
collodion-cotton, which made very good blasting gelatine:--

                                          _
Soluble cotton (collodion) 99.118 per cent.| Nitrogen = 11.64 per cent.
Gun-cotton                  0.642   "     _|
Non-nitrated cotton         0.240   "
Total ash                   0.25    "

It should contain as little non-nitrated or unconverted cotton and as
little gun-cotton as possible, as they are both insoluble in nitro-
glycerol. The quality and composition of any sample of collodion-cotton
can be quickly inferred by determining the percentage of nitrogen by means
of the nitrometer and the use of the solubility test.[A] A high nitrogen
content coupled with a high solubility is the end to be aimed at; a high
nitrogen with a low solubility shows the presence of gun-cotton, and a low
nitrogen, together with a low solubility, the presence of unnitrated
cotton. Where complete solubility is essential and the percentage of
nitrogen less important, Dr Lunge recommends nitration with a mixture of
equal parts of sulphuric and nitric acids containing from 19 to 20 per
cent. of water.

[Footnote A: See Analysis of Explosives.]

Mr T.R. France claims to have invented some improvements in the
manufacture of soluble nitro-cellulose. His object has been to produce an
article as uniform as possible. His explanation of the imperfect action of
the acids is that, however uniform the mixed acids may be in strength and
proportions, and however carefully the operations of nitrating, &c., may
be conducted, there are variable elements found in different samples of
cotton. The cotton fibre has for its protection a glazed surface. It is
tubular and cellular in structure, and contains a natural semi-fluid
substance composed of oil or gum, which varies in nature according to the
nature of the soil upon which the cotton is grown. The tubes of the fibre
seem to be open at one end only when the fibre is of normal length. When,
therefore, the cotton is subjected to the action of the mixed acids, the
line of least resistance seems to be taken by them, viz., the insides of
the tubes constituting the fibre of the cotton, into which they are taken
by capillary attraction, and are subject to change as they progress, and
to the increased resistance from the oil or gum, &c., in their progress,
and therefore to modified action, the result of which is slower and slower
action, or chemical change. He also thinks it is possible that the power
of capillary attraction is balanced in the tubes by air contained therein,
after a little, sufficiently so to prevent the acids from taking full
effect. To get over this, Mr France uses his cotton in a fine state,
almost dust, in fact, and then nitrates in the usual mixture of acids at
40° to 90° F., the excess of acids being removed by pressure. He says he
does not find it necessary to wash this fine cotton dust in an alkaline
solution previous to nitration. His mixed acids consist of 8 parts HNO_{3}
= 42° B., and 12 parts H_{2}SO_{4} = 66° B., and he stirs in the dipping
tank for fifteen minutes, the temperature being 50° F. to 100° F., the
temperature preferred being 75° F.

~"Nitrated" Gun-Cotton.~--The nitrates that are or have been mixed with
gun-cotton in order to supply oxygen are potassium nitrate, ammonium
nitrate, and barium nitrate (tonite). The total combustion of gun-cotton
by potassium nitrate corresponds to the equation:--

10[C_{24}H_{18}(NO_{3}H)_{11}O_{9}] + 82KNO_{3} = 199CO_{2} +
41K_{2}CO_{3} + 145H_{2}O + 96N_{2},

or 828 grms. of nitrate for 1,143 grms. of gun-cotton, or 42 per cent.
nitrate and 58 per cent. gun-cotton. The explosive made at Faversham by
the Cotton Powder Company, and known as tonite No. 1, consists of very
nearly half gun-cotton and half barium nitrate. The relations by weight of
total combustion would be 51.6 of gun-cotton to 48.4 of barium nitrate.
The average composition of tonite I have found by analysis to be 51 per
cent. gun-cotton to 49 per cent. barium nitrate. The heat liberated is
practically the same as for an equivalent weight of KNO_{3}; but the
barium nitrate mixture weighs 2,223 grms. instead of 1,971 grms., or
one-eighth more. The advantage in mixing a nitrate with gun-cotton is that
it supplies oxygen, and by converting all the carbon into carbonic acid,
prevents the formation of the poisonous gas carbonic oxide (CO). The
nitrates of potassium and barium are also used admixed with nitro-
cellulose in several of the sporting smokeless powders.

~The Manufacture of Tonite.~--The explosive tonite was patented by Messrs
Trench, Faure, and Mackie, and is manufactured at Faversham and Melling at
the works of the Cotton Powder Company, and at San Francisco by the Tonite
Powder Company. It consists of finely divided and macerated gun-cotton
incorporated with finely ground nitrate of barium which has been carefully
recrystallised. It is made by acting upon carbonate of barium[A] with
nitric acid. The wet and perfectly purified, finely pulped gun-cotton is
intimately mixed up between edge runners with about the same weight of
nitrate, and the mixing and grinding continued until the whole has become
an intimately mixed paste. This paste is then compressed into cartridges,
formed with a recess at one end for the purpose of inserting the
detonator. The whole is then covered with paraffined paper.

[Footnote A: Witherite, BaCO_{3} + 2HNO_{3} = Ba(NO_{3})_{2} + CO_{2} +
H_{2}O.]

The tonite No. 2 consisted of gun-cotton, nitrates of potash and soda,
charcoal and sulphur. Tonite No. 3[A] is composed as follows:--Gun-cotton,
19 per cent.; di-nitro-benzol, 13 per cent.; and barium nitrate, 68 per
cent. or similar proportions. It is a yellowish colour, and being slower
in its explosive action, is better adapted for blasting soft rock.

[Footnote A: Tonite No. 1 was patented by Messrs Trench, Faure, and
Mackie, and tonite Nos. 2 and 3 by Trench alone.]

Tonite is extensively used in torpedoes and for submarine blasting, also
for quarries, &c. Large quantities were used in the construction of the
Manchester Ship Canal. Among its advantages are, that the English railways
will take tonite on the same footing as gunpowder; it is a very dense
material; if wetted it can easily be dried in the sun; it very readily
explodes by the use of a proper detonator; while it burns very slowly and
without the least danger; the cartridges being waterproofed, it can be
employed in wet bore holes, and it can be tamped with water; and finally,
as it contains sufficient oxygen to oxidise the carbon, no carbonic oxide
(CO) gas is formed, i.e., its detonation is perfect. It is a very safe
explosive to use, being little susceptible to either blows or friction.

Not long ago, a committee, composed of Prof. P. Bedson, Drs Drummond and
Hume, Mr T. Bell, one of H.M. Inspectors of Coal Mines, and others, in
considering the problem whether the fumes produced by the combustion of
tonite were injurious to health, carried out a series of experiments in
coal mines for this purpose. The air at the "intake" was analysed, also
the air of the "return," and the smoky air in the vicinity of the shot
holes. The cartridge was surrounded by the flame-extinguishing mixture,
and packed in a brown paper bag. During the first experiment nineteen
shots were fired (= 6.29 lbs. tonite). The "return" air showed only a
trace of carbonic oxide gas (CO). At the second experiment thirteen shots
were fired (= 4.40 lbs. tonite), and analysis of the air of the "return"
showed that CO was present in traces only, whilst the fumes contained only
1.9 to 4.8 parts per 10,000.

~Dangers in connection with the Manufacture of Guncotton, &c.~--Of all the
nitro compounds, the least dangerous to manufacture are gun-cotton and
collodion-cotton. The fact that the Stowmarket Factory is within five
minutes' walk of the town shows how safe the manufacture of this explosive
is regarded. With the exception of the nitration and the compression into
blocks or discs, the whole process is worked with a large excess of water,
and the probability of an explosion is thus reduced to a minimum. Among
the precautions that should, however, be taken, are--first, the careful
extraction of the resinous and soluble substances from the cotton before
nitration, as it was shown many years ago by Sir F.A. Abel that the
instability of the gun-cotton first manufactured in England and Austria
was chiefly due to these compounds. They are generally removed by boiling
the cotton in a soda solution.

The actual nitration of cotton is not a dangerous operation, but the
operations of wringing in the hydro-extractors, and washing the nitro-
cotton after it leaves the first centrifugal machine, are somewhat so.
Great care should be taken that the wrung-out nitro-cotton at once comes
in contact with a large excess of water, i.e., is at once immersed
entirely in the water, since at this stage it is especially liable to
decomposition, which, once started, is very difficult to stop. The warmer
the mixture and the less water it contains, the more liable it is to
decomposition; hence it is that on warm and damp days the centrifugal
machines are most likely to fire. The commencement of decomposition may be
at once detected by the evolution of red fumes. Directly the gun-cotton is
immersed in the large quantity of water in the beater and poacher it is
safe.

In order that the final product may be stable and have good keeping
qualities, it is necessary that it should be washed completely free from
acid. The treatment in the beater and poacher, by causing the material to
assume the state of a fine pulp, in contact with a large quantity of
water, does a good deal to get rid of the free acid, but the boiling
process is absolutely necessary. It has been proposed to neutralise the
free acid with a dilute solution of ammonia; and Dr C.O. Weber has
published some experiments bearing upon this treatment. He found that
after treatment with ammonia, pyroxyline assumed a slightly yellowish
tinge, which was a sure sign of alkalinity. It was then removed from the
water, and roughly dried between folds of filter paper, and afterwards
dried in an oven at 70° C. After three hours, however, an explosion took
place, which entirely destroyed the strong copper oven in which the nitro-
cotton (about one oz.) had been drying. The explosion was in some respects
remarkable. The pyroxyline was the di-nitro-cellulose (or possibly the
penta-nitro?), and the temperature was below the igniting point of this
material (40° C. would have been a better temperature). Dr Weber
determined the ignition point of his di-nitro-cellulose, and found it to
be 194° to 198° C., and he is therefore of opinion that the explosion was
due to the treatment of the partially washed material with ammonia. A
certain quantity of ammonium nitrate was probably formed, and subsequently
dried upon the nitro-cellulose, in a state of very fine subdivision. The
faintest trace of acid would then be sufficient to bring about the
explosive ignition of the ammonium nitrate.

The drying of gun-cotton or collodion-cotton is also a somewhat dangerous
operation. A temperature of 40° C. (104° F.) should not be exceeded, and
thermometers should be placed in the nitro-cotton, and the temperature
frequently observed. An electric alarm thermometer is also a useful
adjunct to the cotton drying house. Great care must also be taken that
there are no exposed hot-water pipes or stoves in the drying house, as the
fine gun-cotton dust produced by the turning or moving of the material
upon the shelves would settle upon such pipes or stoves, and becoming hot,
would be very sensitive to the least friction. The floor also should be
covered with linoleum or indiarubber. When hot currents of air are made to
pass over the surface of gun-cotton, the gun-cotton becomes electrified.
It is important, therefore, to provide some means to carry it away. Mr
W.F. Reid, F.I.C., was the first to use metal frames, carriers, and
sieves, upon which is secured the cloth holding the gun-cotton, and to
earth them.

The compression of gun-cotton into blocks, discs, &c., is also attended
with considerable risk. Mr O. Guttmann, in an interesting paper upon "The
Dangers in the Manufacture of Explosives" (_Jour. Soc. Chem. Ind._, No. 3,
vol. xi., 1892), says: "The compression of gun-cotton into cartridges
requires far more care than that of gunpowder, as this is done in a warm
state, and gun-cotton even when cold, is more sensitive than gunpowder.
When coming out of the centrifugal machines, the gun-cotton should always
pass first through a sieve, in order to detect nails or matches which may
by chance have got into it. What has been said as to gunpowder presses
applies still more to those for gun-cotton, although the latter are always
hydraulic presses. Generally the pistons fit the mould perfectly, that is
to say, they make aspiration like the piston of a pump. But there is no
metal as yet known which for any length of time will stand the constant
friction of compression, and after some time the mould will be wider in
that part where the greatest compression takes place. The best metal for
this purpose has proved to be a special steel made by Krupp, but this also
is only relatively better; for pistons I prefer hard cast iron. If the
position of the moulds and pistons is not exactly the same in all cases,
what the Germans call 'Ecken' (English 'binding') will take place, viz.,
the mould will stand obliquely to the piston, and a dangerous friction
will result." "Of course, it is necessary to protect the man working the
hydraulic valves during compression. At Waltham Abbey they have a curtain
made of ship's hawsers, which is at the same time elastic and resistant."
Mr Guttmann has found that a partition wall 12 inches thick, made of
2-inch planks, and filled with ground cinders, gives very effective
protection. A door in this partition enables the workman to get to the
press, and a conical tube penetrates the wall, enabling the man to see the
whole work from a safe standpoint. The roof, or one side of the building,
should be of glass, so as to give the explosion a direction.

~Trench's Fire-extinguishing Compound~ is manufactured by the Cotton
Powder Company at Faversham, and is the invention of Mr George Trench,
F.C.S., the manager of the Company. The object of the invention is to
surround the cartridges of tonite, when used in coal mines, with a fire-
extinguishing compound. If a charge of tonite, dynamite, or gelatine
dynamite is put inside a few ounces of this mixture, and then fired, not
the least trace of flame can be observed, and experiments appear to show
that there is no flame at all. The compound consists of sawdust
impregnated with a mixture of alum and chlorides of sodium and ammonia.
Fig. 22 shows the manner of placing the tonite cartridge in the paper bag,
and surrounding it with the fire-extinguishing compound, _aa_. The
attachment of the fuse and detonator is also shown.

[Illustration: FIG. 22.--TRENCH'S FIRE-EXTINGUISHING CARTRIDGE.]

The following report (taken from the _Faversham News_, 22nd Oct. 1887) of
experiments conducted in the presence of several scientific and mining men
will show its value:--"A large wrought-iron tank, of 45 cubic feet
capacity, had been sunk level with the ground in the middle of the yard;
to this tank the gas had been laid on, for a purpose that will be
explained later on. The charges were fired by means of electricity, a
small dynamo firing machine being placed from 30 to 40 yards away from the
'mine.'" Operations were commenced by the top of the tank being covered
over and plastered down in order to make it air-tight; then a sufficient
quantity of coal gas was placed in it to make it highly inflammable and
explosive, the quantity being ascertained by a meter which had been fixed
specially for the purpose. Whilst the gas was being injected the cartridge
was prepared.

The first experiment was to try whether a small charge of tonite--fired
without the patent extinguisher--would ignite the gas. The gas having been
turned on, a miner's lamp was placed in the "tank," but this was
extinguished before the full quantity of gas had gone through the meter.
However, the gas being in, the charge of 1-1/4 oz. tonite was placed in
the "mine," the detonator was connected by means of long wires to the
dynamo machine, and the word was given to "fire." With a tremendous
report, and a flash of fire, the covering of the mine flew in all
directions, clearly showing that the gas had exploded. The next cartridge
(a similar charge) was prepared with the patent compound. First of all a
brown paper case of about 2 inches diameter was taken, and one of the
tonite cartridges was placed in the centre of it, the intervening space
between the charge and-the case being packed with the "fire-extinguishing
compound." The mine having had another supply of gas injected, the
protected cartridge was placed inside and fired. The result was
astonishing, the explosion not being nearly so loud, whilst there was not
the least flash of fire. "Protected" and "unprotected" charges were fired
at intervals, gas being turned into the tank on each occasion. Charges of
tonite varying from 1 to 6 oz. were also used with the compound. The
report was trifling, whilst no flash could be seen.

~Uses of Collodion-Cotton.~--The collodion or soluble gun-cotton is used
for a variety of purposes. The chief use is, however, for the manufacture
of the various explosive gelatine compounds, of which blasting gelatine is
the type. It is also very extensively used in the manufacture of smokeless
powders, both military and sporting--in fact, very few of them do not
contain it. In some, however, nitro-lignose or nitrated wood is used
instead. This, however, is chemically the same thing, viz., nitro-
cellulose, the cellulose being derived from the wood fibre. It is more
used in this connection than the higher nitrate gun-cotton. Another use to
which it has been applied very extensively, of recent years, is in the
manufacture of "celluloid." It is used in photography for the preparation
of the films on the sensitised plates, and many other purposes. Dissolved
in a solution of two parts ether and one of alcohol, it forms the solution
known as collodion, used for a variety of purposes, such as a varnish, as
a paint for signals; in surgery, for uniting the edges of wounds.

Quite lately, Mr Alfred Nobel, the well-known inventor of dynamite, has
patented the use of nitro-cellulose, hydro- or oxy-cellulose, as an
artificial substitute for indiarubber. For this purpose it is dissolved in
a suitable non-volatile or slightly volatile "solvent," such as nitro-
naphthalene, di-nitro-benzene, nitro-toluene, or its homologues; products
are obtained varying from a gelatinous consistency to the hardness of
ebonite. The proportions will vary from about 20 per cent. of nitro-
cellulose in the finished product, forming a soft rubber, to 50 per cent.
nitrating celluloid, and the "solvent" chosen will depend on the use to
which the rubber substitute is to be put, the liquids giving a more
elastic substance, whilst mixtures of solids and liquids may be employed
when the product is to be used at high temperatures. By means of rollers
steam heated, the incorporation may be accomplished without the aid of a
volatile liquid, or the nitro-cellulose may be employed wet, the water
being removed after "solution."

It is advisable to use the cellulose nitrated only just enough to render
it suitable, in order to reduce the inflammability of the finished
product. Mr W. Allen, M.P., of Gateshead, proposed to use celluloid for
cartridge cases, and thus to lighten ammunition, and prevent jambing, for
the case will be resolved into gases along with the powder. Extractors
will also be done away with.

~Celluloid~ is an intimate mechanical mixture of pyroxyline (gun-cotton or
collodion-cotton) with camphor, first made by Hyatt, of Newark, U.S.A.,
and obtained by adding the pyroxyline to melted camphor, or by strongly
compressing the two substances together, or by dissolving the constituents
in an appropriate solvent, e.g., alcohol or ether, and evaporating to
dryness. A combination of the two latter methods, i.e., partial solution,
with pressure, is now usually adapted. The pyroxyline employed is
generally the tetra- and penta-nitrated cellulose, the hexa-nitrate
(gun-cotton) being but seldom used on account of its explosive properties.

Care is taken to prevent the formation of the hexa-nitrate by immersing
the cellulose in only moderately strong nitric acid, or in a warm mixture
of nitric and sulphuric acids. The paper, either in small pieces or in
sheets, is immersed for about twenty-five minutes in a mixture of 2 parts
of nitric acid and 5 parts of sulphuric acid, at a temperature of about
30° C., after which the nitrated cellulose is thoroughly washed with water
to remove the last traces of free acid, pressed, and whilst still moist,
mixed with the camphor.

In the process of Trebouillet and De Besancele, the cellulose, which may
be in the form of paper, cotton, or linen, is twice nitrated--first in the
acid mixture employed in a previous operation; and secondly, in a fresh
mixture of 3 parts sulphuric acid of 1.83 specific gravity, and 2 parts
concentrated nitric acid containing nitrous acid. After each nitration the
mass is subjected to pressure, and is then carefully washed with water, to
which, at the last, a small quantity of ammonia or caustic soda is added
to remove the final traces of acid. The impregnation of the pyroxyline
with the camphor is effected in a variety of ways.

The usual proportion of the constituents is 2 parts pyroxyline and 1 part
camphor. In Trebouillet and De Besancele's process, 100 parts of
pyroxyline are intimately mixed with from 40 to 50 parts camphor, and
moulded together by strong pressure in a hot press, and afterwards dried
by exposure to air, desiccated by calcium chloride or sulphuric acid. The
usual method is, however, to dissolve the camphor in the least possible
quantity of alcohol, and sprinkle the solution over the dry pyroxyline,
which is then covered with a second layer of pyroxyline, and the whole
again treated with the camphor solution, the addition of pyroxyline and
camphor solution being repeated alternately until the requisite amount of
celluloid mixture is obtained.

The mass, which sinks together in transparent lumps, is worked for about
an hour between cold iron rollers, and then for the same period between
rollers which can be gently heated by steam. The layer of celluloid
surrounding the rollers is then cut away and again pressed, the resulting
cake, which is now about 1 cm. thick, being cut into plates of about 70
cm. long and 30 cm. broad. These are placed one above the other, and
strongly pressed together by hydraulic pressure at a temperature of about
70° for twenty-four hours. The thick cakes are once more cut into plates
of the desired thickness, and placed in a chamber heated from 30° to 40°
for eight to fourteen days, whereby they become thoroughly dry, and are
readily made into various articles either by being moulded while warm
under pressure, cut, or turned. Occasionally other liquids, e.g., ether
and wood spirit, are used in place of alcohol as solvents for the camphor.

Celluloid readily colours, and can be marbled for manufacturing purposes,
&c. It is highly inflammable and not explosive even under pressure, and
may be worked under the hammer or between rollers without risk. It softens
in boiling water, and may be moulded or pressed. Its specific gravity
varies slightly with its composition and with the degree of pressure it
has received. It is usually 1.35. It appears to be merely a mixture of its
components, since by treatment with appropriate solvents the camphor may
be readily extracted, and on heating the pyroxyline burns away while the
camphor volatilises.

The manufacture of pyroxyline for the purpose of making celluloid has very
much increased during recent years, and with this increase of production
improved methods of manufacture have been invented. A series of
interesting papers upon the manufacture of pyroxyline has been published
by Mr Walter D. Field, of New York, in the _Journal of the American
Chemical Society_[A] from which the following particulars are taken:--

[Footnote A: Vol. xv., No. 3, 1893; Vol. xvi., No. 7, 1894; Vol. xvi., No.
8, 1894. Figs. 19, 20, 21, 22, and 23 are taken from Mr Field's paper.]

~Selection of the Fibre.~--Cotton fibre, wood fibre, and flax fibre in the
form of raw cotton, scoured cotton, paper, and rags are most generally
used, and give the best results. As the fibres differ greatly in their
structure, they require different methods of nitrating. The cotton fibre
is a flattened hollow ribbon or collapsed cylindrical tube, twisted a
number of times, and closed at one end to form a point. The central canal
is large, and runs nearly to the apex of the fibre. Its side walls are
membraneous, and are readily penetrated by the mixed acids, and
consequently the highest nitration results. In the flax fibre the walls
are comparatively thick, the central canal small; hence it is to be
presumed that the nitration must proceed more slowly than in the case of
cotton. The New Zealand flax gives the most perfectly soluble nitrates of
any of the flaxes. Cotton gives a glutinous collodion, and calico a fluid
collodion. One of the largest manufacturers of pyroxyline in the States
uses the "Memphis Star" brand of cotton. This is an upland cotton, and its
fibres are very soft, moist, and elastic. Its colour is light creamy
white, and is retained after nitration. The staple is short, and the twist
inferior to other grades, the straight ribbon-like filaments being quite
numerous. This cotton is used carded, but not scoured. This brand of
cotton contains a large quantity of half and three-quarter ripe fibre,
which is extremely thin and transparent, distributed throughout the bulk
of the cotton (Monie., Cotton Fibre, 67). Mr Field says, "This is a
significant fact when it is known that from this cotton an extremely
soluble pyroxyline can be produced."

Pyroxyline of an inferior grade as regards colour only can be produced
from the cotton wastes of the trade. They must be scoured before they are
fit for nitrating. Paper made from the pulps of sulphite and sulphate
processes is capable of yielding a very soluble pyroxyline. It can be
nitrated at high temperatures and still yield good results. Tissue paper
made from flax fibre is also used after being cut into squares.

Mowbray (U.S.P., No. 443, 105, 3rd December 1890) says that a pure cotton
tissue paper less than 1/500 inch in thickness, thin as it is, takes on a
glutinous or colloid surface, and thus requires some thirty minutes to
enable the nitration to take place. With a thicker paper only the surface
would be nitrated. He therefore uses a fibre that has been saturated with
a solution of nitrate of soda, and afterwards dried slowly, claiming that
the salt crystallises in the fibre, or enters by the action termed osmose,
and opens up the fibre to the action of the acid. This process would only
be useful when the cotton is to be nitrated at a low temperature. At a
high temperature it would be unnecessary.

Dietz and Wayne (U.S.P., No. 133, 969) use ramie, rheca, or China grass
for producing a soluble pyroxyline. That made from ramie is always of
uniform strength and solubility, and requires a smaller quantity of
solvent to dissolve it than that made from cotton. Mr Field's experience,
however, is entirely contrary to this statement. Such is the influence of
the physical form of the fibre on the process of nitration, that when flax
fibre and cotton fibre are nitrated with acid mixtures of exactly the same
strength, and at the same temperature, the solution of the first is
glutinous or thick, and the second fluid or thin. By simply nitrating at a
higher temperature than the cotton, the flax will yield a pyroxyline
giving an equally fluid collodion.

The presence of chlorine in the fibre must be carefully avoided, as such a
fibre will yield an acid product which cannot be washed neutral. The fibre
must be dry before nitration; and this is best done, according to Mr
Field, by using the form of drier used in drying wool.

~Nitration of the Fibre.~--Mixed cotton and flax fibre in the form of
paper, from 2/1000 to 3/1000 inch thick, and cut into 1-inch squares, is
nitrated by the Celluloid Manufacturing Company, and the same paper, left
in long strips, 1 inch wide, is used for nitration by the Xylonite
Manufacturing Company, of North Adams, Mass. (U.S.A.).

The Celluloid Company introduce the cut paper into the mixed acids by
means of a hollow, rapidly revolving tube, flared at the lower end, and
immersed in the mixed acids. The centrifugal force of the revolving tube
throws the paper towards the sides of the vessel, leaving the centre of
the vessel ready for fresh paper.

The Xylonite Company simply cut the paper into long strips, and introduce
it into the mixed acids by means of forks. The arrangement used by this
Company for holding the mixed acids is a cylindrical vessel divided into a
number of sections, the whole revolving like a turntable, thus allowing
the workman to nitrate successively each lot of paper at a given point.
This Company did not remove the acid from the paper after its immersion,
but plunged it immediately into the water, thus losing a large proportion
of the waste acid. The Celluloid Company, by using the paper in smaller
pieces, and more paper to a pound of acid, and wringing the mixed acid
from the paper before immersion in water, had a better process of
nitration.

Other manufacturers use earthenware vessels, and glass or steel rods,
hooked at one end, having small pieces of rubber hose pulled over the
other end to prevent the hand from slipping. The form of vessel in general
use is that given in Fig. 23. It is large enough to nitrate 1 lb. of
cotton at a time. The hook at one end of the rod enables the workman to
pull the pyroxyline apart, and thus ensures saturation of the fibre. In
the winter the room in which the nitrating is done must be kept at a
temperature of about 70° F. in order to secure equality in the batches.

[Illustration: FIG. 23.--VESSEL FOR NITRATING COTTON OR PAPER.]

The nitrating apparatus of White and Schupphaus (U.S.P., No. 418, 237, 89)
Mr Field considers to be both novel and excellent. The cage (Fig. 24),
with its central perforated cylinder (Fig. 25), is intended to ensure the
rapid and perfect saturation of the tissue paper used for nitrating. The
patentees say that no stirring is required with their apparatus. This,
says Mr Field, might be true when paper is used, or even cotton, when the
temperature of nitration is from 30° to 35° C., but would not be true if
the temperature were raised to 50° to 55° C. The process is as follows:--
The paper is nitrated in the cage (Fig. 25), the bottom of which is formed
by the flanged plate C, fastened to the bottom of the internal cylinder B.
After nitration the cage is carried to a wringer, which forms the basket,
and the acids removed. Finally, the cage is taken to a plunge tank, where
the paper is removed from the cage by simply pulling out the central
perforated cylinder B. Fig. 26 shows the nitrating pot, with its automatic
cover. The plunge tank is shown in plan and section in Figs. 28 and 29.
This apparatus is suitable for the nitration of cotton fibre in bulk at
high or low temperatures. Other methods that have been patented are
Mowbray's (U.S.P., No. 434, 287), in which it is proposed to nitrate paper
in continuous lengths, and Hyatt's (U.S.P., No. 210, 611).

[Illustration: FIG. 24.--CENTRAL PERFORATED CYLINDER.]

[Illustration: FIG. 25.--THE CAGE. WHITE AND SCHUPPHAUS' NITRATING
APPARATUS.]

[Illustration: FIG. 26.--CELLULOID NITRATING POT.]

[Illustration: FIG. 27.--ANOTHER VIEW.]

[Illustration: FIGS. 28, 29.--PLUNGE TANK, IN PLAN AND SECTION.]

~The Acid Mixture.~--Various formulæ have been published for producing
soluble nitro-cellulose. In many instances, although the observations were
correct for the single experiment, a dozen experiments would have produced
a dozen different products. The composition of the acids used depends upon
the substance to be nitrated, and the temperature at which the nitration
will be worked. Practically there are three formulæ in general use--the
one used by the celluloid manufacturers; another in which the cotton is
nitrated at high temperatures; and a third in which the temperature of the
immersion is low, and the time of nitration about six hours. Of the three,
the best method is the last one, or the one in which the cotton is
immersed at a low temperature, and then the reaction allowed to proceed in
pots holding from 5 to 10 lbs. of cotton. The formula used by the
celluloid manufacturers for the production of the low form of nitrated
product which they use is:--

Sulphuric acid   66 parts by weight.
Nitric acid      17   "        "
Water            17   "        "

Temperature of immersion, 30° C. Time, twenty to thirty minutes.

The cellulose is used in the form of tissue paper 2/1000 inch thick, 1 lb.
to 100 of acid mixture. The nitro-cellulose produced by this formula is
very insoluble in the compound ethers and other solvents of pyroxyline,
and is seemingly only converted or gelatinised by the action of the
solvent. The next formula produces a mixture of tetra-and penta-nitro-
celluloses hardly soluble in methyl-alcohol (free from acetone), but very
soluble in anhydrous compound ethers, ketones, and aldehydes:--

Nitric acid, sp. gr. 1.435      8 lbs.
Sulphuric acid, sp. gr. 1.83   15-3/4 lbs.
Cotton                         14 oz.

Temperature of nitration, 60° C. Time of immersion, forty-five minutes.

The 60° of temperature is developed by mixing the acids together. The
cotton is allowed to remain in the acid until it feels "short" to the rod.

The following table, due to Mr W.D. Field, shows very plainly the great
variation in the time of the immersion and the temperature by seemingly
very slight causes. It extends over fourteen working days, during which
time it rained four days. The formula used is that given above, except
that the specific gravity of the nitric acid is somewhat lower. The
product obtained differs only from that produced by using nitric acid of
specific gravity 1.43 in being soluble in methyl-alcohol. From 30 to 35
lbs. of pyroxyline were produced in each of the fourteen days.

A careful examination of this table will prove very instructive. The
increase in yield varies from 31 per cent. to nothing, and the loss runs
as high as 10 per cent., yet care was taken to make the product uniform in
quality. On the days it rained there was a loss, with the exception of the
fourth day, when there was neither a loss nor a gain. On the days it was
partly clear, as just before or after rain, the table shows a loss in
product. We can explain this fact by reason of the moisture-absorbing
qualities of the cotton. On the rainy days it would absorb the moisture
from the air until, when immersed in the acids, they were weakened, and
the fibre dissolved more or less in weakened acid, producing what is known
as "burning" in the batch. It will also be noticed that on days which show
a loss, the time of the immersion was correspondingly short, as on the
a loss, the time of the immersion was correspondingly short, as on the
tenth, twelfth, and seventh days.

 ______________________________________________________________________
|                |                     |                               |
|                |  Specific Gravity.  |               Time.           |
|                |_____________________|_______________________________|
|                |            |        |      |        |      |        |
|                |H_{2}S0_{4}.|HNO_{3}.|Hours.|Minutes.|Hours.|Minutes.|
|________________|____________|________|______|________|______|________|
|                |            |        |      |        |      |        |
| 1. Clear       |   1.838    | 1.4249 |  ... |   20   |  4   |   ...  |
| 2.   "         |   1.837    | 1.4249 |  ... |   20   |  2   |   ...  |
| 3. Cloudy      |   1.837    | 1.4226 |  ... |   45   |  2   |   ...  |
| 4. Rain        |   1.837    | 1.420  |  ... |   20   |  1   |   20   |
| 5. Clear       |   1.8377   | 1.42   |  1   |   15   |  2   |   ...  |
| 6. Rainy       |   1.8391   | 1.422  |  ... |   35   |  1   |   40   |
| 7. Cloudy      |   1.835    | 1.4226 |  ... |   20   |  ... |   35   |
| 8. Clear       |   1.835    | 1.422  |  ... |   35   |  1   |   10   |
| 9. Partly Clear|   1.824    | 1.4271 |  ... |   20   |  1   |   ...  |
|10.     "       |   1.83     | 1.4271 |  ... |   10   |  ... |   25   |
|11. Cloudy      |   1.832    | 1.425  |  ... |   10   |  ... |   50   |
|12. Rainy       |   1.822    | 1.425  |  ... |   10   |  ... |   20   |
|13. Partly CLear|   1.8378   | 1.4257 |  ... |   60   |  1   |   40   |
|14. Cloudy      |   1.837    | 1.4257 |  1   |   56   |  4   |   40   |
|________________|____________|________|______|________|______|________|
|                |               |                   |
|                |Temp., Deg. C. |    Percentage     |
|                |_______________|___________________|
|                |       |       |           |       |
|                | From  |  To   | Increase. | Loss. |
|________________|_______|_______|___________|_______|
|                |       |       |           |       |
| 1. Clear       |  57°  |  62°  |    31     |  ...  |
| 2.   "         |  60°  |  62°  |    18     |  ...  |
| 3. Cloudy      |  60°  |  62°  |     7     |  ...  |
| 4. Rain        |  60°  |  63°  |     0     |   0   |
| 5. Clear       |  58°  |  62°  |    15     |  ...  |
| 6. Rainy       |  58°  |  62°  |    ...    |   2   |
| 7. Cloudy      |  62°  |  65°  |    ...    |  10   |
| 8. Clear       |  60°  |  62°  |     5     |  ...  |
| 9. Partly Clear|  50°  |  60°  |    ...    |   3   |
|10.     "       |  58°  |  60°  |    ...    |  10   |
|11. Cloudy      |  58°  |  60°  |     8     |  ...  |
|12. Rainy       |  58°  |  60°  |    ...    |  10   |
|13. Partly CLear|  50°  |  58°  |    20     |  ...  |
|14. Cloudy      |  50°  |  60°  |    16     |  ...  |
|________________|_______|_______|___________|_______|

The lesson this table teaches is, that it is almost impossible to nitrate
cellulose in small quantities, and get uniform results, when the nitration
is carried on at high temperatures. As regards the solubility of
pyroxyline, Parks found that nitro-benzene, aniline, glacial acetic acid,
and camphor, dissolved in the more volatile solvents methyl-alcohol and
alcohol-ether, were much the best solvents for producing a plastic, as
they are less volatile, and develop greater solvent action under the
influence of heat. Nitro-benzene gives a solution that is granular; it
seems to merely convert the pyroxyline, and not to dissolve it; but on the
addition of alcohol, a solution is at once obtained, and the granular
appearance disappears, and the solution becomes homogeneous. The acid
mixture and the method of nitrating have much to do with the action of the
various solvents, so also has the presence of water.

Dr Schupphaus found that propyl and isobutyl alcohols with camphor were
active solvents, and the ketones, palmitone, and stearone in alcohol
solution, also alpha- and beta-naphthol, with alcohol and anthraquinone
(diphenylene diketone) in alcoholic solution, and also iso-valeric
aldehyde and its derivatives, amyliden-dimethyl and amyliden-diethyl
ethers.

August Sayer (U.S.P., No. 470,451) finds diethyl-ketone, dibutyl-ketone,
di-pentyl-ketone, and the mixed ketones,[A] methyl-ethyl, methyl-propyl,
methyl-butyl, methyl-amyl, and ethyl-butyl ketones are active solvents of
pyroxyline; and Paget finds that although methyl-amyl oxide is a solvent,
that ethyl-amyl oxide is not.

[Footnote A: Ketones are derived from the fatty acids by the substitution
of the hydroxyl of the latter by a monad positive radical. They thus
resemble aldehydes in constitution. The best-known ketone is acetone
CH_{3}CO.CH_{3}. Mixed ketones are obtained by distilling together salts
of two different fatty acids. Thus potassic butyrate and potassic acetate
form propyl-methyl-ketone--

C(C_{2}H_{5})H_{2}
|
CO.CH_{3}]

The solvents of pyroxyline can be divided into general classes--First,
those which are solvents without the aid of heat or solution in alcohol;
second, those that are solvents when dissolved in alcohol. These solvents
are those which also develop a solvent action when heated to their melting
point in combination with pyroxyline.

Mr W.D. Field groups the solvents of pyroxyline into classes thus: Two of
the monohydric alcohols; compound ethers of the fatty acids with
monohydric alcohols, aldehydes; simple and mixed ketones of the fatty acid
series. These four classes include the greater number of the solvents of
pyroxyline. Those not included are as follows:--Amyl-nitrate and nitrite,
methylene-di-methyl ether, ethidene-diethyl ether, amyl-chloracetate,
nitro-benzene and di-nitro-benzene, coumarin, camphor, glacial acetic
acid, and mono-, di-, and tri-acetin.

Richard Hale uses the following solvent:--Amyl-acetate, 4 volumes;
petroleum naphtha, 4 volumes; methyl-alcohol, 2 volumes; pyroxyline, 4 to
5 ounces to the gallon of solvent. Hale used petroleum naphtha to hasten
the drying qualities of the varnish, so that it would set on the article
to be varnished before it had a chance to run off. It is, however, the
non-hygroscopic character of the solvent that makes the varnish
successful. This formula is very largely used for the production of
pyroxyline varnish, which is used for varnishing pens, pencils, &c., also
brass-work and silver-ware.

The body known as oxy-cellulose[A] is formed by the action of nitric acid
upon cellulose when boiled with it. The quantity formed is about 30 per
cent. of cellulose acted upon. When washed free from acid, it gelatinises.
It is then soluble in dilute alkalies, and can be reprecipitated from
solution by alcohol, acids, or saline solutions. Messrs Cross and Bevan
assign to it the formula C_{18}H_{26}O_{16}. It dissolves in concentrated
sulphuric acid, and with nitric acid forms a nitro body of the formula
C_{18}H_{23}O_{16}3(NO_{2}), which is prepared as follows:--The gelatinous
oxy-cellulose is washed with strong nitric acid until free from water, and
is then diffused through a mixture of equal volumes of strong sulphuric
and nitric acids, in which it quickly dissolves. The solution, after
standing for about an hour, is poured in a fine stream into a large volume
of water, by which the "nitro" body is precipitated as a white flocculent
mass. The product, after drying at 110° C., was found upon analysis to
contain 6.48 per cent. nitrogen.

[Footnote A: "On the Oxidation of Cellulose," by C.F. Cross and E.J.
Bevan, _Jour. Chem. Soc._, 1883, p. 22.]

MISCELLANEOUS NITRO-EXPLOSIVES.

~Nitro-Starch.~--It is only recently that, by means of the process
introduced by the "Actiengesellschaft Dynamit Nobel," it has been possible
to make this explosive upon the manufacturing scale. Nitro-starch has been
known since 1883, when Braconnot discovered it, and called it xyloidine.
Its formula is C_{6}H_{8}O_{3}(NO_{3})_{2}, but Dr Otto Mühlhäusen has
lately succeeded in preparing higher nitrated compounds, viz.:--

(_a._) C_{6}H_{7-1/2}O_{2-1/2}(NO_{3})_{2-1/2}.

(_b._) C_{6}H_{7}O_{4}(NO_{3})_{3}.

Or doubling the molecule of starch:--

                                                          Nitrogen.
  i.  Tetra-nitro-starch   C_{12}H_{16}O_{6}(ONO_{2})_{4} 11.11 per cent.
 ii.  Penta-nitro-starch   C_{12}H_{15}O_{5}(ONO_{2})_{5} 12.75    "
iii.  Hexa-nitro-starch    C_{12}H_{14}O_{4}(ONO_{2})_{6} 14.14    "

He regards them as true ethers (esters) of nitric acid. Thus on treatment
with sulphuric acid, these compounds yield NO_{3}H, the residue O.NO_{2}
thus appearing to be replaced by the sulphuric acid residue. On treatment
with a solution of ferrous chloride, nitric oxide and "soluble" starch are
regenerated. On shaking with sulphuric acid over mercury, all the nitrogen
is split off as NO.

Tetra-nitro-starch is prepared upon the large scale as follows:--A
quantity of potato-starch is taken and exposed in some suitable
desiccating apparatus at a temperature of 100° C. until all the moisture
which it contains is completely driven off. It is then reduced to a fine
powder by grinding, and dissolved in nitric acid of specific gravity
1.501. The vessel in which this solution is accomplished is made of lead,
and must be provided with two jackets, cooled by means of water. It should
further be fitted with a screw-agitator, in order to keep the nitric acid
circulating freely. The charge of starch is introduced through an opening
in the cover of this digesting vessel, and the proportions of acid to
starch are 10 kilogrammes of starch to 100 kilos. of acid. The temperature
is kept within the limits 20° to 25° C. When the solution of the starch is
complete, the liquid is conducted into a precipitating apparatus, which is
also provided with a cooling jacket, for the purpose of regulating the
temperature. The bottom of this vessel is double and perforated, and here
is placed a layer of gun-cotton to act as a filter. This vessel is filled
with spent nitro-sulphuric acid obtained as a waste product from the
nitro-glycerine manufactory, and the solution of starch in nitric acid is
sprayed into it through an injector worked by compressed air, whereby the
nitro-starch is thrown down in the form of a fine-grained powdery
precipitate.

In order to precipitate 100 kilos. of the acid solution of starch, it is
necessary to employ 500 kilos. of spent nitro-sulphuric acid. As it is
precipitated the nitro-starch collects on the gun-cotton filter, and the
acid liquor is run off through a tap placed beneath the perforated double
bottom of the vessel, and of course below the filter pad. The precipitated
starch is further cleansed from acid by repeated washings and by pressure,
until all trace of acidity has been eliminated, and the substance exhibits
a neutral reaction. The next step is to treat the nitro-starch with a 5
per cent. solution of soda, in contact with which it is allowed to stand
for at least twenty-four hours. The product is then ground up until a sort
of "milk" or emulsion is obtained, and lastly treated with a solution of
aniline, so that when pressed into cake, it contains about 33 per cent. of
water, and 1 per cent. of aniline.

Dr Mühlhäusen, working on these lines in the laboratory, prepared nitro-
starch which contained 10.96 and 11.09 per cent. of nitrogen. When in the
state of powder it is snow-white in colour; it becomes electrified when
rubbed; it is very stable, and soluble even in the cold in nitro-
glycerine. He has also prepared a tetra-nitro-starch containing 10.58 and
10.50 per cent. of nitrogen, by pouring water into a solution of starch in
nitric acid which had stood for several days. The substance thus produced
in the laboratory had all the properties of that prepared by the other
process.

The production of penta-nitro-starch is effected by adding 20 grms. of
rice-starch--previously dried at a temperature of 100°C., in order to
eliminate all moisture--to a mixture of 100 grms. of nitric acid, specific
gravity 1.501, and 300 grms. of sulphuric acid, specific gravity 1.8 (some
tetra-nitro-starch is also formed at the same time). After standing in
contact with these mixed acids for one hour the starch has undergone a
change, and the mass may now be discharged into a large quantity of water,
and then washed, first with water, and finally with an aqueous solution of
soda. The yield in Dr Mühlhäusen's experiments was 147.5 per cent.

The substance thus formed is now heated with ether-alcohol, the ether is
distilled off, and the penta-nitro-starch appears as a precipitate, whilst
the tetra-nitro-starch, which is formed simultaneously, remains in
solution in the alcohol. As obtained by this process, it contained 12.76
and 12.98 per cent. nitrogen, whilst the soluble tetra-nitro-starch
contained 10.45 per cent.

Hexa-nitro-starch is the product chiefly formed when 40 grms. of dry
starch are treated with 400 grms. of nitric acid, specific gravity 1.501,
and allowed to stand in contact for twenty-four hours; 200 grms. of this
mixture are then poured into 600 c.c. of sulphuric acid of 66° B. The
result of this manipulation is a white precipitate, which contains
13.52-13.23 and 13.22 per cent. nitrogen; and consists, therefore, of a
mixture of penta- and hexa-nitro-starch.

The experiments undertaken with these substances demonstrated that those
prepared by precipitating the nitro-starch with strong sulphuric acid were
less stable in character or properties than those which were precipitated
by water or weak sulphuric acid. Dr Mühlhäusen is of opinion that possibly
in the former case a sulpho-group may be formed, which in small quantity
may occasion this instability.

The following table shows the behaviour of these substances prepared in
different ways and under various conditions:--

 __________________________________________________________________
|                     |                                            |
|                     |                  SAMPLES.                  |
|                     |____________________________________________|
|                     |        |        |        |        |        |
|                     |   A.   |   B.   |   C.   |   D.   |   E.   |
| Ignition-point      |175° C. |170° C. |152° C. |121° C. |155° C. |
| Stability           |Stable  |Stable  |Unstable|Unstable|Unstable|
| Per cent. of N.     | 11.02  | 10.54  | 12.87  | 12.59  | 13.52  |
| 96 per cent. alcohol|  Sol.  |  Sol.  | Insol. | Insol. | Insol. |
| Ether               | Insol. | Insol. | Insol. | Insol. | Insol. |
| Ether-alcohol       |  Sol.  |  Sol.  |  Sol.  |  Sol.  |  Sol.  |
| Acetic Ether        |  Sol.  |  Sol.  |  Sol.  |  Sol.  |  Sol.  |
|_____________________|________|________|________|________|________|

These samples were prepared as follows:--

A. From 1 part nitric acid and 2 parts sulphuric acid (containing 70 per
   cent. H_{2}O).
B. From 1 part nitric acid and water.
C. From 1 part nitric and 3 parts H_{2}SO_{4} (con.).
D. From 1 part nitric and 3.5 parts con. H_{2}SO_{4}.
E. From 1 part nitric and 3 parts con. H_{2}SO_{4}.

Dr Mühlhäusen is of opinion that these compounds may be turned to
practical account in the production of good smokeless powder. He
recommends the following proportions and method. Six grms. of nitro-jute
and 2 grms. of nitro-starch are mixed together, and moistened with acetic
ether. These ingredients are then worked together into a uniform mass, and
dried at a temperature ranging between the limits 50° to 60° C. He has
himself prepared such a smokeless powder, which proved to contain 11.54
per cent. of nitrogen, and was very stable. Further details of Dr
Mühlhäusen's work upon nitro-starch can be found in _Dingler's
Polytechnisches Journal_, paper "Die höhren Salpetersäureäther der
Stärke," 1892, Band 284, s. 137-143, and a Bibliography up to 1892 in
_Arms and Explosives_, December 1892.

M. Berthelot gives the heat of formation of nitro-starch as 812 cals. for
1 grm., and the heat of total combustion as equal to 706.5 cals. for 207
grms., or for 1 grm. 3,413 cals. The heat of decomposition could only be
calculated if the products of decomposition were given, but they have not
as yet been studied, and the quantity of oxygen contained in the compound
is far from being sufficient for its complete combustion. Berthelot and
Vieille found the average velocities for nitro-starch powder, density of
charge about 1.2, in a tin tube 4 mm. external diameter, to be, in two
experiments, 5,222 m. and 5,674 m. In a tin tube 5.5 mm. external
diameter, the velocity was 5,815 m., and in lead tube 5,006 m. (density
1.1 to 1.2). The starch powder is hygroscopic, and is insoluble in water
and alcohol. When dry it is very explosive, and takes fire at about 350°
F. Mr Alfred Nobel has taken out a patent (Eng. Pat. No. 6,560, 88) for
the use of nitro-starch. His invention relates to the treatment of nitro-
starch and nitro-dextrine, for the purpose of producing an explosive
powder, to be used in place of gunpowder. He incorporates these materials
with nitro-cellulose, and dissolves the whole in acetone, which is
afterwards distilled off. A perfect incorporation of the ingredients is
thus brought about.

~Nitro-Jute.~--It is obtained by treating jute with nitric acid. Its
properties have been studied by Messrs Cross and Bevan (_Jour. Chem.
Soc._, 1889, 199), and by Mühlhäusen. The latter used for its nitration an
acid mixture composed of equal parts of nitric and sulphuric acids, which
was allowed to act upon the jute for some time. He found that with long
exposure, i.e., from three to four hours in the acids, there was a
disintegrating of the fibre-bundles, and the nitration was attended by
secondary decomposition and conversion into products soluble in the acid
mixture. Cross and Bevan's work upon this subject leads them to conclude
that the highest yield of nitrate is represented by an increase of weight
of 51 per cent. They give jute the empirical formula C_{12}H_{18}O_{9} (C
= 47 per cent. H = 6 per cent., and O = 47 per cent.), and believe its
conversion into a nitro compound to take place thus:--

C_{12}H_{18}O + 3HNO_{3} = C_{12}H_{15}O_{6}(NO_{3})_{3} + 3H_{2}O.

This is equivalent to a gain in weight of 44 per cent. for the tri-
nitrate, and of 58 per cent. for the tetra-nitrate. The formation of the
tetra-nitrate appears to be the limit of nitration of jute-fibre. In other
words, if we represent the ligno-cellulose molecule by a C_{12} formula,
it will contain four hydroxyl (OH) groups, or two less than cellulose
similarly represented. The following are their nitration results:--

Acids used.--I. HNO_{3} sp. gr. 1.43, and H_{2}SO_{4} = 1.84 equal parts.
            II. 1 vol. HNO_{3}(1.5), 1 vol. H_{2}SO_{4}(1.84).
           III. 1 vol. HNO_{3}(1.5), 75 vols. H_{2}SO_{4}(1.84).

I. = 144.4; II. = 153.3; III. = 154.4 grms.; 100 grms. of fibre being used
in all three cases.

Duration of exposure, thirty minutes at 18° C.

The nitrogen was determined in the products, and equalled 10.5 per cent.
Theory for C_{12}H_{15}O_{6}(NO_{3})_{3} = 9.5 per cent. and for
C_{12}H_{15}O_{6}(NO_{3})_{4} = 11.5 per cent. These nitrates resemble
those of cellulose, and are in all essential points nitrates of ligno-
cellulose.

Mühlhäusen obtained a much lower yield, and probably, as pointed out by
Cross and Bevan, a secondary decomposition took place, and his products,
therefore, probably approximate to the derivatives of cellulose rather
than to those of ligno-cellulose, the more oxidisable, non-cellulose, or
lignone constituents having been decomposed. In fact, he regards his
product as cellulose penta-nitrate (C_{12}H_{16}O_{5}(ONO_{2})_{5}). The
_Chemiker Zeitung_, xxi., p. 163, contains a further paper by Mühlhäusen
on the explosive nitro-jute. After purifying the jute-fibre by boiling it
with a 1 per cent. solution of sodium carbonate, and washing with water,
he treated 1 part of the purified jute with 15 parts of nitro-sulphuric
acid, and obtained the following results with different proportions of
nitric to sulphuric acids:--

                                             Yield  Ignition Nitrogen.
                                           per cent.  Point.
Experiment  I.-- 1. HNO_{3}  1. H_{2}SO_{4}  129.5   170° C.   11.96%
    "      II.       "       2.    "         132.2   167° C.   12.15%
    "     III.       "       3.    "         135.8   169° C.   11.91%

An experiment made with fine carded jute and the same mixture of acids as
in No. II. gave 145.4 per cent. nitro-jute, which ignited at 192° C., and
contained 12 per cent. nitrogen. This explosive is not at present
manufactured upon the large scale, and Messrs Cross and Bevan are of
opinion that there is no very obvious advantage in the use of lignified
textile fibre as raw materials for explosive nitrates, seeing that a large
number of raw materials containing cellulose (chiefly as cotton) can be
obtained at a cheaper rate, and yield also 150 to 170 per cent. of
explosive material when nitrated, and are in many ways superior to the
products obtained hitherto from jute.

~Nitro-mannite~ is formed by the action of nitric acid on mannite, a
hex-acid alcohol closely related to sugar. It occurs abundantly in manna,
which is the partly dried sap of the manna-ash (_Fraxinus ornus_). It is
formed in the lactic acid fermentation of sugar, and by the action of
nascent hydrogen on glucose and cellulose, or on invert sugar. Its formula
is C_{6}H_{8}(OH)_{6} and that of nitro-mannite C_{6}H_{8}(NO_{3})_{6}.
Mannite crystallises in needles or rhombic prisms, which are soluble in
water and alcohol, and have a sweet taste. Nitro-mannite forms white
needle-shaped crystals, insoluble in water, but soluble in ether or
alcohol. When rapidly heated, they ignite at about 374° F., and explode at
about 590° F. It is more susceptible to friction and percussion than
nitro-glycerine, and unless pure it is liable to spontaneous
decomposition. It is considered as the nitric ether of the hexatomic
alcohol mannite. It is formed by the action of a mixture of nitric and
sulphuric acids upon mannite--

C_{6}H_{8}(OH)_{6} + 6HNO_{3} = C_{6}H_{8}(NO_{3})_{6} + 6H_{2}O.

Its products of explosion are as shown in the following equation:--

C_{6}H_{8}(OH)_{6} = 6CO_{2} + 4H_{2}O + 3N_{2} + O_{2}.

Its percentage composition is as follows:--Carbon, 15.9 per cent.;
hydrogen, 1.8 per cent.; nitrogen, 18.6 per cent.; and oxygen, 63.7 per
cent. Its melting point is 112 to 113° C., and it solidifies at 93°. When
carefully prepared and purified by recrystallisation from alcohol, and
kept protected from sunlight, it can be kept for several years without
alteration.

Nitro-mannite is more dangerous than nitro-glycerine, as it is more
sensitive to shock. It is intermediate in its shattering properties
between nitro-glycerine and fulminate of mercury. It explodes by the shock
of copper on iron or copper, and even of porcelain on porcelain, provided
the latter shock be violent. Its heat of formation from its elements is
+156.1 calories. It is not manufactured upon the commercial scale.

Besides the nitro compounds already described, there are many others, but
they are of little importance, and are none of them made upon the large
scale. Among such substances are _nitro-coal_, which is made by the action
of nitric acid on coal; _nitro-colle_, a product which results from the
action of nitric acid on isinglass or gelatine, soaked in water. It is
then treated with the usual acids.

Another method is to place strong glue in cold water until it has absorbed
the maximum amount of the latter. The mixture is solidified by the
addition of nitric acid, nitrated in the usual way, and well washed.
Abel's _Glyoxiline_ is only nitrated gun-cotton impregnated with nitro-
glycerine. Nitro-lignine is only nitro-cellulose made from wood instead of
cotton; and nitro-straw is also only nitro-cellulose. The explosive known
as _Keil's Explosive_ contains nitro-glucose. Nitro-molasses, which is a
liquid product, has also been proposed, and nitro-saccharose, the product
obtained by the nitration of sugar. It is a white, sandy, explosive
substance, soluble in alcohol and ether. When made from cane sugar, it
does not crystallise; but if made from milk sugar, it does. It has been
used in percussion caps, being stronger and quicker than nitro-glycerine.
It is, however, very sensitive and very hygroscopic, and very prone to
decomposition. Nitro-tar, made from crude tar-oil, by nitration with
nitric acid of a specific gravity of 1.53 to 1.54. Nitro-toluol is used,
mixed with nitro-glycerine. This list, however, does not exhaust the
various substances that have been nitrated and proposed as explosives.
Even such unlikely substances as horse dung have been experimented with.
None of them are very much used, and very few of them are made upon the
manufacturing scale.




CHAPTER IV.

_DYNAMITE AND GELATINES._

Kieselguhr Dynamite--Classification of Dynamites--Properties and
Efficiency of Ordinary Dynamite--Other Forms of Dynamite--Gelatine and
Gelatine Dynamites, Suitable Gun-Cotton for, and Treatment of--Other
Materials used--Composition of Gelignite--Blasting Gelatine--Gelatine
Dynamite--Absorbing Materials--Wood Pulp--Potassium Nitrate, &c.--
Manufacture and Apparatus used, and Properties of Gelatine Dynamites--
Cordite--Composition and Manufacture.


~Dynamite.~--Dynamite consists of nitro-glycerine either absorbed by some
porous material, or mixed with some other substance or substances which
are either explosives or merely inert materials. Among the porous
substances used is kieselguhr, a silicious earth which consists chiefly of
the skeletons of various species of diatoms. This earth occurs in beds
chiefly in Hanover, Sweden, and Scotland. The best quality for the purpose
of manufacturing dynamite is that which contains the largest quantity of
the long tubular _bacillariæ_, and less of the round and lancet-shaped
forms, such as _pleurosigmata_ and _diclyochæ_, as the tube-shaped diatoms
absorb the nitro-glycerine better, and it becomes packed into the centre
of the silicious skeleton of the diatoms, the skeleton acting as a kind of
tamping, and increasing the intensity of the explosion.

Dynamites are classified by the late Colonel Cundill, R.A., in his
"Dictionary of Explosives" as follows:--

1. Dynamites with an inert base, acting merely as an absorbent.

2. Dynamites with an active base, i.e., an explosive base. No. 2 may be
again divided into three minor classes, which contain as base--

(_a._) Charcoal.

(_b._) Gunpowder or other nitrate, or chlorate mixture.

(_c._) Gun-cotton or other nitro compound (nitro-benzol, &c.).

The first of these, viz., charcoal, was one of the first absorbents for
nitro-glycerine ever used; the second is represented by the well-known
Atlas powder; and the last includes the well-known and largely used
gelatine compounds, viz., gelignite and gelatine dynamite, and also tonite
No. 3, &c.

In the year 1867 Nobel produced dynamite by absorbing the nitro-glycerine
in an inert substance, forming a plastic mass. In his patent he says:
"This invention relates to the use of nitro-glycerine in an altered
condition, which renders it far more practical and safe for use. The
altered condition of the nitro-glycerine is effected by causing it to be
absorbed in porous unexplosive substances, such as charcoal, silica,
paper, or similar materials, whereby it is converted into a powder, which
I call dynamite, or Nobel's safety powder. By the absorption of the nitro-
glycerine in some porous substance it acquires the property of being in a
high degree insensible to shocks, and it can also be burned over a fire
without exploding."

Ordinary dynamite consists of a mixture of 75 per cent. of nitro-glycerine
and 25 per cent. of kieselguhr. The guhr as imported (Messrs A. Haake &
Co. are the chief importers) contains from 20 to 30 per cent. of water and
organic matter. The water may be very easily estimated by drying a weighed
quantity in a platinum crucible at 100° C. for some time and re-weighing,
and the organic matter by igniting the residue strongly over a Bunsen
burner. Before the guhr can be used for making dynamite it must be
calcined, in order not only to get rid of moisture, but also the organic
matter.

A good guhr should absorb four times its weight of nitro-glycerine, and
should then form a comparatively dry mixture. It should be pale pink, red
brown, or white. The pink is generally preferred, and it should be as free
as possible from grit of all kinds, quartz particles, &c., and should have
a smooth feeling when rubbed between the finger and thumb, and should show
a large quantity of diatoms when viewed under the microscope. The
following was the analysis of a dried sample of kieselguhr:--Silica,
94.30; magnesia, 2.10; oxide of iron and alumina, 1.3; organic matter,
0.40; moisture, 1.90 per cent.

The guhr is generally dried in a reverberatory muffle furnace. It is
spread out on the bottom to the thickness of 3 or 4 inches, and should
every now and then be turned over and raked about with an iron rabble or
hoe. The temperature should be sufficiently high to make the guhr red hot,
or the organic matter will not be burnt off. The time occupied in
calcining will depend of course upon the quality of the guhr being
operated upon. Those containing a high percentage of water and organic
matter will of course take longer than those that do not. A sample of the
calcined guhr should not contain more than 0.5 per cent. of moisture and
organic matter together.

After the guhr is dry it requires to be sifted and crushed. The crushing
is done by passing it between iron rollers fixed at the bottom of a cone
or hopper, and revolving at a moderate speed. Beneath the rollers a fine
sieve should be placed, through which the guhr must be made to pass.

The kieselguhr having been dried, crushed, and sifted, should be packed
away in bags, and care should be taken that it does not again absorb
moisture, as if it contains anything above about five-tenths per cent. of
water it will cause the dynamite made with it to exude. The guhr thus
prepared is taken up to the danger area, and mixed with nitro-glycerine.
The nitro-glycerine used should be quite free from water, and clear, and
should have been standing for a day or two in the precipitating house. The
guhr and nitro-glycerine are mixed in lead tanks (about 1-1/2 foot deep,
and 2 to 3 feet long), in the proportions of 75 of the nitro-glycerine to
25 of the guhr, unless the guhr is found to be too absorbent, which will
cause the dynamite to be too dry and to crumble. In this case a small
quantity of barium sulphate, say about 1 per cent., should be added to the
guhr. This will lessen its absorbing powers, or a highly absorptive sample
of guhr may be mixed with one of less absorptive power, in the proportions
found by experiment to be the best suited to make a fairly moist dynamite,
but one that will not exude.

The mixing itself is generally performed in a separate house. In a series
of lead-lined tanks the guhr is weighed, placed in a tank, and the nitro-
glycerine poured on to it. The nitro-glycerine may be weighed out in
indiarubber buckets. The whole is then mixed by hand, and well rubbed
between the hands, and afterwards passed through a sieve. At this stage
the dynamite should be dry and powdery, and of a uniform colour.

It is now ready to be made up into cartridges, and should be taken over to
the cartridge huts. These are small buildings surrounded with mounds, and
contain a single cartridge machine. Each hut requires three girls--one to
work the press, and two to wrap up the cartridges. The cartridge press
consists of a short cylinder of the diameter of the cartridge that it is
intended to make. Into this cylinder a piston, pointed with ivory or
lignum vitæ wood, works up and down from a spring worked by a lever. Round
the upper edge of the cylinder is fastened a canvas bag, into which the
powdery dynamite is placed by means of a wooden scoop, and the descending
piston forces the dynamite down the cylinder and out of the open end,
where the compressed dynamite can be broken off at convenient lengths. The
whole machine should be made of gun-metal, and should be upright against
the wall of the building. The two girls, who sit at tables placed on each
side of the press, wrap the cartridges in parchment paper. From these huts
the cartridges are collected by boys every ten minutes or a quarter of an
hour, and taken to the packing room, where they are packed in 5-lb.
cardboard boxes, which are then further packed in deal boxes lined with
indiarubber, and fastened down air tight. The wooden lids are then nailed
down with brass or zinc nails, and a label pasted on the outside giving
the weight and description of the contents. The boxes should then be
removed to the magazines. It is well to take a certain number of
cartridges from the packing house at different times during the day, say
three or four samples, and to test them by the heat test. A sample cut
from a cartridge, about 1 inch long, should be placed under a glass shade,
together with water (a large desiccator, in fact), and left for some days.
A good dynamite should not, under these conditions, show any signs of
exudation, even after weeks.[A]

[Footnote A: For analysis of dynamite, see chapter on "Analysis," and
author's article in _Chem. News_, 23rd September 1892.]

~Properties of Kieselguhr Dynamite.~--One cubic foot of dynamite weighs 76
lbs. 4 oz. The specific gravity of 75 per cent. dynamite is, however,
1.50. It is a red or grey colour, and rather greasy to the touch. It is
much less sensitive to shock than nitro-glycerine, but explodes
occasionally with the shock of a rifle bullet, or when struck. The
addition of a few per cent. of camphor will considerably diminish its
explosive qualities to such an extent that it can be made non-explosive
except to a very strong fulminate detonator. The direct contact of water
disintegrates dynamite, separating the nitro-glycerine, hence great
caution is necessary in using it in wet places. It freezes at about 40°
Fahr. (4° C.), and remains frozen at temperatures considerably exceeding
that point. When frozen, it is comparatively useless as an explosive
agent, and must be thawed with care. This is best done by placing the
cartridges in a warming pan, which consists of a tin can, with double
sides and bottom, into which hot water (130° Fahr.) can be poured. The
dynamite will require to be left in for some considerable time before it
becomes soft. On no account must it be placed on a hot stove or near a
fire, as many serious accidents have occurred in this way.

Frozen dynamite is a hard mass, with altered properties, and requires 1.5
grm. of fulminate instead of 0.5 grm. to explode it. Thawing may also
cause exudation of the nitro-glycerine, which is much more sensitive to
shock, and if accidentally struck with an iron tool, may explode. It is a
dangerous thing to cut a frozen cartridge with a knife. Ramming is even
more dangerous; in fact it is not only dangerous, but wasteful, to use
dynamite when in a frozen state.

Dynamite explodes at a temperature of 360° Fahr., and is very sensitive to
friction when hot. In hot countries it should never be exposed to the rays
of the sun. It should, however, not be kept in a damp or moist place, as
this is liable to cause exudation. Sunlight, if direct, can cause a slow
decomposition, as with all nitro and nitric compounds. Electric sparks
ignite, without exploding it, at least when operating in the open air.

Dynamite, when made with neutral nitro-glycerine, appears to keep
indefinitely. Sodium or calcium carbonate to the extent of 1 per cent. is
often added to dynamite to ensure its being neutral. If it has commenced
to undergo change, however, it rapidly becomes acid, and sometimes
explodes spontaneously, especially if contained in resisting envelopes.
Nevertheless, neutral and well-made dynamite has been kept for years in a
magazine without loss of its explosive force. If water is brought into
contact with it, the nitro-glycerine is gradually displaced from the
silica (guhr). This action tends to render all wet dynamite dangerous.

It has been observed that a dynamite made with wood sawdust can be
moistened and then dried without marked alteration, and from 15 to 20 per
cent. of water may be added to cellulose dynamite without depriving it of
the power of exploding by strong detonator (this is similar to wet
gun-cotton). It is, however, rendered much less sensitive to shock. With
regard to the power of No. 1 dynamite, experiments made in lead cylinders
give the relative value of No. 1 dynamite, 1.0; blasting gelatine, 1.4;
and nitro-glycerine, 1.4. The heat liberated by the sudden explosion of
dynamite is the same as its heat of combustion,[A] and proportionate to
the weight of nitro-glycerine contained in the mixture. The gases formed
are carbonic acid, water, nitrogen, and oxygen.

[Footnote A: Berthelot, "Explosives and their Power."]

The "explosive wave" (of Berthelot) for dynamite is about 5,000 metres per
second. At this rate the explosion of a cartridge a foot long would only
occupy 1/24000 part of a second, while a ton of dynamite cartridges about
7/8 diameter, laid end to end, and measuring one mile in length, would be
exploded in one-quarter of a second by detonating a cartridge at either
end.[A] Mr C. Napier Hake, F.I.C., the Inspector of Explosives for the
Victorian Government, in his paper, "Notes on Explosives," says: "The
theoretical efficiency of an explosive cannot in practice be realised in
useful work for several reasons, as for instance in blasting rock--

"1. Incomplete combustion.

"2. Compression and chemical changes induced in surrounding material.

"3. Energy expended in cracking and heating of the material which is not
displaced.

"4. The escape of gas through the blast-hole and the fissures caused by
the explosion.

"The useful work consists partly in displacing the shattered masses. The
proportion of useful work obtainable has been variously estimated at from
14 to 33 per cent. of the theoretical maximum potential."

[Footnote A: C.N. Hake, "Notes on Explosives," _Jour. Soc. Chem. Ind._,
1889.]

Among the various forms of dynamite that are manufactured is carbo-
dynamite, the invention of Messrs Walter F. Reid and W.D. Borland. The
base is nitro-glycerine, and the absorbent is carbon in the form of burnt
cork. It is as cheap as ordinary dynamite, and has greater explosive
force, seeing that 90 per cent. of the mixture is pure nitro-glycerine,
and the absorbent itself is highly combustible. It is also claimed that if
this dynamite becomes wet, no exudation takes place.

Atlas powder is a dynamite, chiefly manufactured in America at the Repanno
Chemical Works, Philadelphia. It is a composition of nitro-glycerine,
wood-pulp, nitrate of soda, and carbonate of magnesia. This was the
explosive used in the outrages committed in London, by the so-called
"dynamiters." Different varieties contain from 20 to 75 per cent. of
nitro-glycerine.

The Rhenish dynamite, considerably used in the mines of Cornwall, is
composed of 70 parts of a solution of 2 to 3 per cent. of naphthalene in
nitro-glycerine, 3 parts of chalk, 7 parts of sulphate of barium, and 20
of kieselguhr.

Kieselguhr dynamites are being largely given up in favour of gelatine
explosives. The late Colonel Cundill, in his "Dictionary of Explosives,"
gives a list of about 125 kinds of dynamites. Many of these, however, are
not manufactured. Among the best known after the ordinary No. 1 dynamite
are forcite, ammonia dynamite, litho-fracteur, rendock, Atlas powder,
giant powder, and the various explosive gelatines. They all contain nitro-
glycerine, mixed with a variety of other substances, such as absorbent
earths, wood-pulp, nitro-cotton, carbon in some form or other, nitro-
benzol, paraffin, sulphur, nitrates, or chlorates, &c. &c.

~Blasting Gelatine and Gelatine Dynamite.~--The gelatine explosives
chiefly in use are known under the names of blasting gelatine, gelatine
dynamite, and gelignite. They all consist of the variety of nitro-
cellulose known as collodion-cotton, i.e., a mixture of the penta- and
tetra-nitrates dissolved in nitro-glycerine, and made up with various
proportions of wood-pulp, and some nitrate, or other material of a similar
nature. As the gun-cotton contains too little oxygen for complete
combustion, and the nitro-glycerine an excess, a mixture of the two
substances is very beneficial.

Blasting gelatine consists of collodion-cotton and nitro-glycerine without
any other substance, and was patented by Mr Alfred Nobel in 1875. It is a
clear, semi-transparent, jelly-like substance, of a specific gravity of
1.5 to 1.55, slightly elastic, resembling indiarubber, and generally
consists of 92 per cent. to 93 per cent. of nitro-glycerine, and 7 to 8
per cent. of nitro-cotton. The cotton from which it is made should be of
good quality. The following is the analysis of a sample of nitro-cellulose
which made very good gelatine:-

Soluble cotton          99.118 per cent.
Gun-cotton               0.642      "
Non-nitrated cotton      0.240      "
Nitrogen                11.64       "
Total ash                0.25       "

The soluble cotton, which is a mixture of the tetra- and penta-nitrates,
is soluble in ether-alcohol, and also in nitro-glycerine, and many other
solvents, whereas the hexa-nitrate (gun-cotton),
C_{12}H_{14}O_{4}(ONO_{2})_{6}, is not soluble in the above liquids,
although it is soluble in acetone or acetic ether. It is very essential,
therefore, that the nitro-cotton used in the manufacture of the gelatine
explosives should be as free as possible from gun-cotton, otherwise little
lumps of undissolved nitro-cotton will be left in the finished gelatine.
The non-nitrated or unconverted cotton should also be very low, in fact
considerably under 1/2 per cent.

The nitro-cotton and the nitro-glycerine used should always be tested
before use by the heat test, because if they do not separately stand this
test, it cannot be expected that the gelatine made from them will do so.
It often occurs, however, that although both the ingredients stand this
test separately before being mixed, that after the process of manufacture
one or other or both fail to do so.

The nitro-cotton most suitable for gelatine making is that which has been
finely pulped. If it is not already fine enough, it must be passed through
a fine brass wire sieve. It will be found that it requires to be rubbed
through by hand, and will not go through at all if in the least degree
damp. It is better, therefore, to dry it first. The percentage of nitrogen
in the nitrated cotton should be over 11 per cent. It should be as free as
possible from sand or grit, and should give but little ash upon ignition,
not more than 0.25 per cent. The cotton, which is generally packed wet in
zinc-lined wooden boxes, will require to be dried, as it is very essential
indeed that none of the materials used in the manufacture of gelatine
should contain more than the slightest trace of water. If they do, the
gelatine subsequently made from them will most certainly exude, and become
dangerous and comparatively valueless. It will also be much more difficult
to make the nitro-cotton dissolve in the nitro-glycerine if either
contains water.

In order to find out how long any sample of cotton requires to be dried, a
sample should be taken from the centre of several boxes, well mixed, and
about 1,000 grms. spread out on a paper tray, weighed, and the whole then
placed in the water oven at 100° C., and dried for an hour or so, and
again weighed, and the percentage of moisture calculated from the loss in
weight. This will be a guide to the time that the cotton will probably
require to be in the drying house. Samples generally contain from 20 to 30
per cent. of water. After drying for a period of forty-eight hours, a
sample should be again dried in the oven at 100° C., and the moisture
determined, and so on at intervals until the bulk of the cotton is found
to be dry, i.e., to contain from 0.25 to 0.5 per cent. of moisture. It is
then ready to be sifted. During the process of removing to the sifting
house and the sifting itself, the cotton should be exposed to the air as
little as possible, as dry nitro-cotton absorbs as much as 2 per cent. of
moisture from the air at ordinary temperatures and average dryness.

The drying house usually consists of a wooden building, the inside of
which is fitted with shelves, or rather framework to contain drawers, made
of wood, with brass or copper wire netting bottoms. A current of hot air
is made to pass through the shelves and over the surface of the cotton,
which is spread out upon them to the depth of about 2 inches. This current
of air can be obtained in any way that may be found convenient, such as by
means of a fan or Root's blower, the air being passed over hot bricks, or
hot-water pipes before entering the building. The cotton should also be
occasionally turned over by hand in order that a fresh surface may be
continually exposed to the action of the hot air. The building itself may
be heated by means of hot-water pipes, but on no account should any of the
pipes be exposed. They should all be most carefully covered over with
wood-work, because when the dry nitro-cotton is moved, as in turning it
over, very fine particles get into the air, and gradually settling on the
pipes, window ledges, &c., may become very hot, when the slightest
friction might cause explosion. It is on this account that this house
should be very carefully swept out every day. It is also very desirable
that the floor of this house should be covered with oilcloth or linoleum,
as being soft, it lessens the friction.

List shoes should always be worn in this building, and a thermometer hung
up somewhere about the centre of the house, and one should also be kept in
one of the trays to give the temperature of the cotton, especially the
bottom of the trays. The one nearest to the hot air inlet should be
selected. If the temperature of the house is kept at about 40° C. it will
be quite high enough. The building must of course be properly ventilated,
and it will be found very useful to have the walls made double, and the
intervening space filled with cinders, and the roof covered with felt, as
this helps to prevent the loss of heat through radiation, and to preserve
a uniform temperature, which is very desirable.

The dry cotton thus obtained, if not already fine enough, should be sifted
through a brass sieve, and packed away ready for use in zinc air-tight
cases, or in indiarubber bags. The various gelatine compounds, gelignite,
gelatine dynamite, and blasting gelatine, are manufactured in exactly the
same way. The forms known as gelatine dynamite differ from blasting
gelatine in containing certain proportions of wood-pulp and potassium
nitrate, &c. The following are analyses of some typical samples of the
three compounds:--

                              Gelatine       Blasting
                  Gelignite.  Dynamite.      Gelatine.

Nitro-glycerine    60.514      71.128     92.94 per cent.
Nitro-cellulose     4.888       7.632      7.06    "
Wood-pulp           7.178       4.259       ...    "
Potassium nitrate  27.420      16.720       ...    "
Water                ...        0.261       ...    "

The gelignite and gelatine dynamites consist, therefore, of blasting
gelatine, thickened up with a mixture of absorbing materials. Although the
blasting gelatine is weight for weight more powerful, it is more difficult
to make than either of the other two compounds, it being somewhat
difficult to make it stand the exudation and melting tests. The higher
percentage of nitro-cotton, too, makes it expensive.

When the dry nitro-cotton, which has been carefully weighed out in the
proportions necessary either for blasting gelatine or any of the other
gelatine explosives, is brought to the gelatine making house, it is placed
in a lead-lined trough, and the necessary quantity of pure dry nitro-
glycerine poured upon it. The whole is then well stirred up, and kept at a
temperature of from 40° to 45° C. It should not be allowed to go much
above 40° C.; but higher temperatures may be used if the nitro-cotton is
very obstinate,[A] and will not dissolve. Great caution must, however, be
observed in this case. The mixture should be constantly worked about by
the workman with a wooden paddle for at least half an hour. At a
temperature of 40° to 45° the nitro-glycerine acts upon the nitro-cotton
and forms a jelly. Without heat the gelatinisation is very imperfect
indeed, and at temperatures under 40° C. takes place very slowly.

[Footnote A: Generally due to the nitro-cotton being damp.]

[Illustration: FIG. 30.--WERNER, PFLEIDERER, & PERKINS' MIXING MACHINE.]

The limit of temperature is 50° C. or thereabouts. Beyond this the jelly
should never be allowed to go, and to 50° only under exceptional
circumstances.

The tank in which the jelly is made is double-lined, in order to allow of
the passage of hot water between its inner and outer linings. A series of
such tanks are generally built in a wooden framework, and the double
linings are made to communicate, so that the hot water can flow from one
to the other consecutively. The temperature of the water should be about
60° C. if it is intended to gelatinise at 45° C., and about 80° if at
50° C.; but this point must, of course, be found by experiment for the
particular plant used. An arrangement should be made to enable the workman
to at once cut off the supply of hot water and pass cold water through the
tanks in case the explosive becomes too hot.

[Illustration: FIG. 31.--MR M'ROBERTS' MIXER FOR GELATINE EXPLOSIVES.]

The best way to keep the temperature of the water constant is to have a
large tank of water raised upon a platform, some 5 or 6 feet high, outside
the building, which is automatically supplied with water, and into which
steam is turned. A thermometer stuck through a piece of cork and floated
upon the surface of the tank will give the means of regulating the
temperature.

When the jelly in the tanks has become semi-transparent and the cotton has
entirely dissolved, the mixture should be transferred to the mixing
machine. The mixing machines are specially designed for this work, and are
built in iron, with steel or bronze kneading- and mixing-blades, according
to requirements.

A suitable machine for the purpose is that known as the Nito-Universal
Incorporator, shown in Fig. 30, which has been specially constructed by
Messrs Werner, Pfleiderer, & Perkins, Ltd., after many years' experience
in the mixing of explosive materials, and is now almost exclusively
adopted in both Government and private factories. Mr George M'Roberts'[A]
mixing machine, however, which is shown in Fig. 31, is still used in some
factories for dynamite jelly.

[Footnote A: See _Jour. Soc. Chem. Ind._, 1890, 267.]

If it is intended to make gelignite, or gelatine dynamite, it is at this
point that the proper proportions of wood-pulp[A] and potassium nitrate
should be added, and the whole well mixed for at least half an hour, until
the various ingredients are thoroughly incorporated.

[Footnote A: Most of the wood-pulp used in England is obtained from
pine-trees, but poplar, lime, birch, and beech wood are also used. It is
chiefly imported as wood-pulp. The pulp is prepared as follows:--The bark
and roots are first removed, and the logs then sawn into boards, from
which the knots are removed. The pieces of wood are afterwards put through
a machine which breaks them up into small pieces about an inch long, which
are then crushed between rollers. These fragments are finally boiled with
a solution of sodium bisulphite, under a pressure of about 90 lbs. per
square inch, the duration of the boiling being from ten to twelve hours.
Sulphurous acid has also been used. Pine-wood yields about 45 per cent.
and birch about 40 per cent. of pulp when treated by this process. The
pulp is afterwards bleached and washed, &c.

                 Birch.  Beech.  Lime.   Pine.   Poplar.
Cellulose        55.52   45.47   53.09   56.99   62.77 per cent.
Resin             1.14    0.41    3.93    0.97    1.37    "
Aqueous extract   2.65    2.47    3.56    1.26    2.88    "
Water            12.48   12.57   10.10   13.87   12.10    "
Lignine          28.21   39.14   29.32   26.91   20.88    "]

The following analysis of woods is by Dr H. Müller:--These mixing machines
can either be turned by hand, or a shaft can be brought into the house and
the machine worked by means of a belt at twenty to thirty revolutions per
minute. The bearings should be kept constantly greased and examined, and
the explosive mixture carefully excluded. When the gelatine mixture has
been thoroughly incorporated, and neither particles of nitrate or wood
meal can be detected in the mass, it should be transferred to wooden boxes
and carried away to the cartridge-making machines to be worked up into
cartridges.

[Illustration: FIG. 32.--PLAN OF THE BOX CONTAINING THE EXPLOSIVE, IN
M'ROBERTS' MACHINE.]

The application of heat in the manufacture of the jelly from collodion-
cotton and nitro-glycerine is absolutely necessary, unless some other
solvent is used besides the nitro-glycerine, such as acetone, acetic
ether, methyl, or ethyl-alcohol. (They are all too expensive, with the
exception of acetone and methyl-alcohol, for use upon the large scale.)
These liquids not only dissolve the nitro-cellulose in the cold, but
render the resulting gelatine compound less sensitive to concussion, and
reduce its quickness of explosion (as in cordite). They also lower the
temperature at which the nitro-glycerine becomes congealed, i.e., they
lower the freezing point[A] of the resulting gelatine.

[Footnote A: It has been proposed to mix dynamite with amyl alcohol for
this purpose. Di-nitro-mono-chlorhydrine has also been proposed.]

The finished gelatine paste, upon entering the cartridge huts, is at once
transferred to the cartridge-making machine, which is very like an
ordinary sausage-making machine[A] (Fig. 33). The whole thing must be made
of gun-metal or brass, and it consists of a conical case containing a
shaft and screw. The revolutions of the shaft cause the thread of the
screw to push forward the gelatine introduced by the hopper on the top to
the nozzle, the apex of the cone-shaped case, from whence the gelatine
issues as a continuous rope. The nozzle is of course of a diameter
according to the size of cartridge required.

[Footnote A: G. M'Roberts, _Jour. Soc. Chem. Ind._, 31st March 1890, p.
266.]

[Illustration: FIG. 33.--CARTRIDGE-MAKING MACHINE FOR GELATINE
EXPLOSIVES.]

The issuing gelatine can of course be cut off at any length. This is best
done with a piece of hard wood planed down to a cutting edge, i.e.,
wedge-shaped. Mr Trench has devised a kind of brass frame, into which the
gelatine issuing from the nozzle of the cartridge machine is forced,
finding its way along a series of grooves. When the frame is full, a
wooden frame, which is hinged to one end of the bottom frame, and fitted
with a series of brass knives, is shut down, thereby cutting the gelatine
up into lengths of about 4 inches.

It is essential that the cartridge machines should have no metallic
contacts inside. The bearing for the screw shaft must be fixed outside the
cone containing the gelatine. One of these machines can convert from 5 to
10 cwt. of gelatine into cartridges per diem, depending upon the diameter
of the cartridges made.

After being cut up into lengths of about 3 inches, the gelatine is rolled
up in cartridge paper. Waterproof paper is generally used. The cartridges
are then packed away in cardboard boxes, which are again packed in deal
boxes lined with indiarubber, and screwed down air tight, brass screws or
zinc or brass nails being used for the purpose. These boxes are sent to
the magazines. Before the boxes are fastened down a cartridge or so should
be removed and tested by the heat test, the liquefaction test, and the
test for liability to exudation. (Appendix, p. 6, Explosives Act, 1875.) A
cartridge also should be stored in the magazine in case of any subsequent
dispute after the bulk of the material has left the factory.

The object of the liquefaction test is to ensure that the gelatine shall
be able to withstand a fairly high temperature (such as it might encounter
in a ship's hold) without melting or running together. The test is carried
out as follows:--A cylinder of the gelatine dynamite is cut from the
cartridge of a length equal to its diameter. The edges must be sharp. This
cylinder is to be placed on end on a flat surface (such as paper), and
secured by a pin through the centre, and exposed for 144 consecutive hours
to a temperature of 85° to 90° F., and during such time the cylinder
should not diminish in height by more than one-fourth of an inch, and the
cut edges should remain sharp. There should also be no stain of
nitroglycerine upon the paper.

The exudation test consists in freezing and thawing the gelatine three
times in succession. Under these conditions there should be no exudation
of nitro-glycerine. All the materials used in the manufacture of gelatine
explosives should be subjected to analytical examination before use, as
success largely depends upon the purity of the raw materials. The
wood-pulp, for instance, must be examined for acidity.

~Properties of the Gelatine Compounds.~--Blasting gelatine is generally
composed of 93 to 95 parts nitro-glycerine, and 5 to 7 parts of nitro-
cellulose, but the relative proportions of explosive base and nitro-
glycerine, &c., in the various forms of the gelatine explosives do not
always correspond to those necessary for total combustion, either because
an incomplete combustion gives rise to a greater volume of gas, or because
the rapidity of decomposition and the law of expansion varies according to
the relative proportions and the conditions of application. The various
additions to blasting gelatine generally have the effect of lowering the
strength by reducing the amount of nitro-glycerine, but this is sometimes
done in order to change a shattering agent into a propulsive force. If
this process be carried too far, we of course lose the advantages due to
the presence of nitro-glycerine. There is therefore a limit to these
additions.[A]

[Footnote A: Mica is said to increase the rapidity of explosion when mixed
with gelatine.]

The homogeneousness and stability of the mixture are of the highest
importance. It is highly essential that the nitro-glycerine should be
completely absorbed by the substances with which it is mixed, and that it
should not subsequently exude when subjected to heat or damp. It is also
important that there should be no excess of nitro-glycerine, as this may
diminish instead of augment the strength, owing to a difference in the
mode of the propagation of the explosive wave in the liquid, and in the
mixture. Nitro-glycerine at its freezing point has a tendency to separate
from its absorbing material, in fact to exude. When frozen, too, it
requires a more powerful detonation to explode it, but it is less
sensitive to shock. The specific gravity of blasting gelatine is 1.5
(i.e., nearly equal to that of nitro-glycerol); that of gun-cotton (dry)
is 1.0.

Blasting gelatine burns in the air when unconfined without explosion, at
least in small quantities and when not previously heated, but it is rather
uncertain in this respect. It can be kept at a moderately high temperature
(70° C.) without decomposition. At higher temperatures the nitro-glycerine
will partially evaporate. When slowly heated, it explodes at 204° C. If,
however, it contains as much as 10 per cent. of camphor, it burns without
exploding. According to Berthelot,[A] gelatine composed of 91.6 per cent.
nitro-glycerine and 8.4 per cent. of nitro-cellulose, which are the
proportions corresponding to total combustion, produces by explosion
177CO_{2}+ 143H_{2}O + 8N_{2}.

[Footnote A: Berthelot, "Explosives and their Powers."]

He takes C_{24}H_{22}(NO_{3}H)_{9}O_{11} as the formula of the nitro-
cellulose, and 51C_{3}H_{2}(NO_{3}H)_{3} + C_{24}H_{22}(NO_{3}H)_{9}O_{11}
as the formula of the gelatine itself, its equivalent weight being 12,360
grms. The heat liberated by its explosion is equal to 19,381 calories, or
for 1 kilo. 1,535 calories. Volume of gases reduced temperature equals
8,950 litres. The relative value[A] of blasting gelatine to nitro-
glycerine is as 1.4 to 1.45, kieselguhr dynamite being taken as 1.0.

[Footnote A: Roux and Sarran.]




CHAPTER V.

_NITRO-BENZOL, ROBURITE, BELLITE, PICRIC ACID, &c._

Explosives derived from Benzene--Toluene and Nitro-Benzene--Di- and
Tri-nitro-Benzene--Roburite: Properties and Manufacture--Bellite:
Properties, &c.--Securite--Tonite No. 3.--Nitro-Toluene--
Nitro-Naphthalene--Ammonite--Sprengel's Explosives--Picric Acid--
Picrates--Picric Powders--Melinite--Abel's Mixture--Brugère's Powders--
The Fulminates--Composition, Formula, Preparation, Danger of, &c.--
Detonators: Sizes, Composition, Manufacture--Fuses, &c.


~The Explosives derived from Benzene.~--There is a large class of
explosives made from the nitrated hydro-carbons--benzene, C_{6}H_{6};
toluene, C_{7}H_{8}; naphthalene, C_{10}H_{8}; and also from phenol (or
carbolic acid), C_{6}H_{5}OH. The benzene hydro-carbons are generally
colourless liquids, insoluble in water, but soluble in alcohol and ether.
They generally distil without decomposition. They burn with a smoky flame,
and have an ethereal odour. They are easily nitrated and sulphurated;
mono, di, and tri derivatives are readily prepared, according to the
strength of the acids used. It is only the H-atoms of the benzene nucleus
which enter into reaction.

Benzene was discovered by Faraday in 1825, and detected in coal-tar by
Hofmann in 1845. It can be obtained from that portion of coal-tar which
boils at 80° to 85° by fractionating or freezing.[A] The ordinary benzene
of commerce contains thiophene (C_{4}H_{4}S), from which it may be freed
by shaking with sulphuric acid. Its boiling point is 79° C.; specific
gravity at 0° equals 0.9. It burns with a luminous smoky flame, and is a
good solvent for fats, resins, sulphur, phosphorus, &c. Toluene was
discovered in 1837, and is prepared from coal-tar. It boils at 110° C.,
and is still liquid at 28° C.

[Footnote A: It may be prepared chemically pure by distilling a mixture of
benzoic acid and lime.]

The mono-, chloro-, bromo-, and iodo-benzenes are colourless liquids of
peculiar odour. Di-chloro-, di-bromo-benzenes, tri- and hexa-chloro- and
bromo-benzenes, are also known; and mono-chloro-, C_{6}H_{4}Cl(CH_{3}),
and bromo-toluenes, together with di derivatives in the ortho, meta, and
para modifications. The nitro-benzenes and toluenes are used as
explosives. The following summary is taken from Dr A. Bernthsen's "Organic
Chemistry":--

                             SUMMARY.
 ____________________________________________________________________
|                                                                    |
| C_{6}H_{5}(N0_{2}) Nitro-benzene. Liq. B.Pt. 206° C.               |
|                                                                    |
| C_{6}H_{4}(NO_{2})_{2} Ortho-, meta-, and para- di-nitro-benzenes. |
| Solid. M.P. 118°, 90°, and 172° C.                                 |
|                                                                    |
| C_{6}H_{3}(NO_{3})_{3} S.-Tri-nitro-benzene. Solid. M.P. 121° C.   |
|____________________________________________________________________|
|                                                                    |
| C_{6}H_{4}(CH_{3})NO_{2} Ortho-, meta-, and para- nitro-toluenes.  |
| B.P. 218°, 230°, and 234° C, Para compound solid.                  |
|____________________________________________________________________|
|                                                                    |
| C_{6}H_{3}(CH_{3})_{2}NO_{2} Nitro-xylene. Liquid.                 |
|____________________________________________________________________|
|                                                                    |
| C_{6}H_{2}(CH_{3})_{3}NO_{2} Nitro-mesitylene. Solid.              |
|____________________________________________________________________|
|                                                                    |
| C_{6}H_{3}(CH_{3})(NO_{2})_{2} Di-nitro-toluenes.                  |
|____________________________________________________________________|
|                                                                    |
| C_{6}H_{4}Cl(NO_{2}) Nitro-chloro-benzenes.                        |
|                                                                    |
| C_{6}Br_{4}(NO_{2})_{2} Tetra-bromo-di-nitrobenzene.               |
|____________________________________________________________________|

The nitro compounds are mostly pale yellow liquids, which distil
unchanged, and volatilise with water vapour, or colourless or pale yellow
needles or prisms. Some of them, however, are of an intense yellow colour.
Many of them explode upon being heated. They are heavier than water, and
insoluble in it, but mostly soluble in alcohol, ether, and glacial acetic
acid.

Nitro-benzene, C_{6}H_{5}(NO_{2}), was discovered in 1834 by Mitscherlich.
It is a yellow liquid, with a melting point of +3° C. It has an intense
odour of bitter almonds. It solidifies in the cold. In di-nitro-benzene,
the two nitro groups may be in the meta, ortho, or para position, the meta
position being the most general (see fig., page 4). By recrystallising
from alcohol, pure meta-di-nitro-benzene may be obtained in long
colourless needles. The ortho compound crystallises in tables, and the
para in needles. They are both colourless. When toluene is nitrated, the
para and ortho are chiefly formed, and a very little of the meta compound.

~Nitro Compounds of Benzene and Toluene.~--The preparation of the nitro
derivatives of the hydrocarbons of the benzene series is very simple. It
is only necessary to bring the hydrocarbon into contact with strong nitric
acid, when the reaction takes place, and one or more of the hydrogen atoms
of the hydrocarbon are replaced by the nitryl group (NO_{2}). Thus by the
action of nitric acid on benzene (or benzol), mono-nitro-benzene is
formed:--

C_{6}H_{6} + HNO_{3} = C_{6}H_{5}.NO_{2} +H_{2}O.
                       Mono-nitro-benzene.

By the action of another molecule of nitric acid, the di-nitro-benzene is
formed:--

C_{6}H_{5}.NO_{2} + HNO_{3} = C_{6}H_{4}(NO_{2})_{2} + H_{2}O.
                               Di-nitro-benzene.

These nitro bodies are not acids, nor are they ethereal salts of nitrous
acid, as nitro-glycerine is of glycerine. They are regarded as formed from
nitric acid by the replacement of hydroxyl by benzene radicals.

~Mono-nitro Benzene~ is made by treating benzene with concentrated nitric
acid, or a mixture of nitric and sulphuric acids. The latter, as in the
case of the nitration of glycerine, takes no part in the reaction, but
only prevents the dilution of the nitric acid by the water formed in the
reaction. Small quantities may be made thus:--Take 150 c.c. of H_{2}SO_{4}
and 75 c.c. HNO_{3}, or 1 part nitric to 2 parts sulphuric acid, and put
in a beaker standing in cold water; then add 15 to 20 c.c. of benzene,
drop by drop, waiting between each addition for the completion of the
reaction, and shake well during the operation. When finished, pour
contents of beaker into about a litre of cold water; the nitro-benzol will
sink to the bottom. Decant the water, and wash the nitro-benzol two or
three times in a separating funnel with water. Finally, dry the product by
adding a little granulated calcium chloride, and allowing to stand for
some little time, it may then be distilled. Nitro-benzene is a heavy oily
liquid which boils at 205° C., has a specific gravity of 1.2, and an odour
like that of oil of bitter almonds. In the arts it is chiefly used in the
preparation of aniline.

~Di-nitro Benzene~ is a product of the further action of nitric acid on
benzene or nitro-benzene. It crystallises in long fine needles or thin
rhombic plates, and melts at 89.9° C. It can be made thus:--The acid
mixture used consists of equal parts of nitric and sulphuric acids, say 50
c.c. of each, and without cooling add very slowly 10 c.c. of benzene from
a pipette. After the action is over, boil the mixture for a short time,
then pour into about half a litre of water, filter off the crystals thus
produced, press between layers of filter paper, and crystallise from
alcohol. Di-nitro-benzene, or meta-di-nitro-benzene, as it is sometimes
called, enters into the composition of several explosives, such as tonite
No. 3, roburite, securite, bellite.

Nitro-benzene is manufactured upon the large scale as follows:--Along a
bench a row of glass flasks, containing 1 gallon each (1 to 2 lbs.
benzene), are placed, and the acids added in small portions at a time, the
workmen commencing with the first, and adding a small quantity to each in
turn, until the nitration was complete. This process was a dangerous one,
and is now obsolete. The first nitro-benzene made commercially in England,
by Messrs Simpson, Maule, and Nicholson, of Kennington, in 1856, was by
this process. Now, however, vertical iron cylinders, made of cast-iron,
are used for the nitrating operation. They are about 4 feet in diameter
and 4 feet deep, and a series are generally arranged in a row, at a
convenient height from the ground, beneath a line of shafting. Each
cylinder is covered with a cast-iron lid having a raised rim all round. A
central orifice gives passage to a vertical shaft, and two or more other
conveniently arranged openings allow the benzene and the mixed acids to
flow in. Each of these openings is surrounded with a deep rim, so that the
whole top of the cylinder can be flooded with water some inches in depth,
without any of it running into the interior of the nitrator. The lid
overhangs the cylinder somewhat, and in the outer rim a number of shot-
holes or tubes allow the water to flow down all over the outside of the
cylinder into a shallow cast-iron dish, in which it stands. By means of a
good supply of cold water, the top, sides, and bottom of the whole
apparatus is thus cooled and continually flooded. The agitator consists of
cast-iron arms keyed to a vertical shaft, with fixed arms or dash-plates
secured to the sides of the cylinder. The shaft has a mitre wheel keyed on
the top, which works into a corresponding wheel on the horizontal shafting
running along the top of the converters. This latter is secured to a
clutch; and there is a feather on the shaft, so that any one of the
converters can if necessary be put either in or out of gear. This
arrangement is necessary, as riggers or belts of leather, cotton, or
indiarubber will not stand the atmosphere of the nitro-benzole house.
Above and close to each nitrator stands its acid store tank, of iron or
stoneware.

The building in which the nitration is carried out should consist of one
story, have a light roof, walls of hard brick, and a concrete floor of 9
to 12 inches thick, and covered with pitch, to protect its surface from
the action of the acids. The floor should be inclined to a drain, to save
any nitro-benzol spilt. Fire hydrants should be placed at convenient
places, and it should be possible to at once fill the building with steam.
A 2-inch pipe, with a cock outside the building, is advisable. The
building should also be as far as possible isolated.

The acids are mixed beforehand, and allowed to cool before use. The nitric
acid used has a specific gravity of 1.388, and should be as free as
possible from the lower oxides of nitrogen. The sulphuric acid has a
specific gravity of 1.845, and contains from 95 to 96 per cent. of mono-
hydrate. A good mixture is 100 parts of nitric to 140 parts of sulphuric
acid, and 78 parts of benzene; or 128 parts HNO_{3}, 179 of H_{2}SO_{4},
and 100 of benzene (C_{6}H_{6}). The benzene having been introduced into
the cylinder, the water is turned on and the apparatus cooled, the
agitators are set running, and the acid cock turned on so as to allow it
to flow in a very thin stream into the nitrator.

Should it be necessary to check the machinery even for a moment, the
stream of acid must be stopped and the agitation continued for some time,
as the action proceeds with such vigour that if the benzene being nitrated
comes to rest and acid continues to flow, local heating occurs, and the
mixture may inflame. Accidents from this cause have been not infrequent.
The operation requires between eight to ten hours, agitation and cooling
being kept up all the time. When all the acid is added the water is shut
off, and the temperature allowed to rise a little, to about 100° C. When
it ceases to rise the agitators are thrown out of gear, and the mixture
allowed some hours to cool and settle. The acid is then drawn off, and the
nitro-benzene is well washed with water, and sometimes distilled with wet
steam, to recover a little unconverted benzene and a trace of paraffin
(about .5 per cent. together). At many English works, 100 to 200 gallons,
or 800 to 1,760 lbs., are nitrated at a time, and toluene is often used
instead of benzene, especially if the nitro-benzene is for use as essence
of myrbane. The waste acids, specific gravity 1.6 to 1.7, contain a little
nitro-benzene in solution and some oxalic acid. They are concentrated in
cast-iron pots and used over again.

~Di-nitro Benzene~ is obtained by treating a charge of the hydrocarbon
benzene with double the quantity of mixed acids in two operations, or
rather in two stages, the second lot of acid being run in directly after
the first. The cooling water is then shut off, and the temperature allowed
to rise rapidly, or nitro-benzene already manufactured is taken and again
nitrated with acids. A large quantity of acid fumes come off, and some of
the nitro- and di-nitro-benzol produced comes off at the high temperature
which is attained, and a good condensing apparatus of stoneware must be
used to prevent loss. The product is separated from the acids, washed with
cold water and then with hot. It is slightly soluble in water, so that the
washing waters must be kept and used over again. Finally it is allowed to
settle, and run while still warm into iron trays, in which it solidifies
in masses 2 or 4 inches thick. It should not contain any nitro-benzol, nor
soil a piece of paper when laid on it, should be well crystallised, fairly
hard, and almost odourless. The chief product is meta-di-nitro-benzene,
melting point 89.8, but ortho-di-nitro-benzene, melting point 118°, and
para-di-nitro, melting point 172°, are also produced. The melting point of
the commercial product is between 85° to 87° C.

Di-nitro-toluene is made in a similar manner. The tri-nitro-benzene can
only be made by using a very large excess of the mixed acids. Nitro-
benzene, when reduced with iron, zinc, or tin, and hydrochloric acids,
forms aniline.

~Roburite.~--This explosive is the invention of a German chemist, Dr Carl
Roth (English patent 267A, 1887), and is now manufactured in England, at
Gathurst, near Wigan. It consists of two component parts, non-explosive in
themselves (Sprengel's principle), but which, when mixed, form a powerful
explosive. The two substances are ammonium nitrate and chlorinated
di-nitro-benzol. Nitro-naphthalene is also used. Nitrate of soda and
sulphate of ammonium are allowed to be mixed with it. The advantages
claimed for the introduction of chlorine into the nitro compound are that
chlorine exerts a loosening effect upon the NO_{2} groups, and enables the
compound to burn more rapidly than when the nitro groups alone are present.

The formula of chloro-di-nitro-benzol is C_{6}H_{3}Cl(NO_{2})_{2}. The
theoretical percentage of nitrogen, therefore, is 13.82, and of chlorine
17.53. Dr Roth states that, from experiments he has made, the dynamic
effect is considerably increased by the introduction of chlorine into the
nitro compound. Roburite burns quickly, and is not sensitive to shock; it
must be used dry; it cannot be made to explode by concussion, pressure,
friction, fire, or lightning; it does not freeze; it does not give off
deleterious fumes, and it is to all intents and purposes flameless; and
when properly tamped and fired by electricity, can be safely used in fiery
mines, neither fine dust nor gases being ignited by it. The action is
rending and not pulverising. Compared to gunpowder, it is more powerful in
a ratio ranging from 2-1/2 to 4 to 1, according to the substance acted
upon. It is largely used in blasting, pit sinking, quarrying, &c., but
especially in coal mining. According to Dr Roth, the following is the
equation of its decomposition:--

C_{6}H_{3}Cl(NO_{2})_{2} + 9HN_{4}NO_{3} = 6CO_{2} + 20N + HCl.

In appearance roburite is a brownish yellow powder, with the
characteristic smell of nitro-benzol. Its specific gravity is 1.40. The
Company's statement that the fumes of roburite were harmless having been
questioned by the miners of the Garswood Coal and Iron Works Colliery, a
scientific committee was appointed by the management and the men jointly
for the purpose of settling the question. The members of this committee
were Dr N. Hannah, Dr D.J. Mouncey, and Professor H.B. Dixon, F.R.S., of
Owens College. After a protracted investigation, a long and technical
report was issued, completely vindicating the innocuousness of roburite
when properly used. In the words of _The Iron and Coal Trades' Review_
(May 24, 1889), "The verdict, though not on every point in favour of the
use in all circumstances of roburite in coal mines, is yet of so
pronounced a character in its favour as an explosive that it is impossible
to resist the conclusion that the claims put forward on its behalf rest on
solid grounds."

Roburite was also one of the explosives investigated by the committee
appointed in September 1889 by the Durham Coalowners' and Miners'
Associations, for the purpose of determining whether the fumes produced by
certain explosives are injurious to health. Both owners and workmen were
represented on the committee, which elected Mr T. Bell, H.M. Inspector of
Mines, as its chairman, with Professor P.P. Bedson and Drs Drummond and
Hume as professional advisers. The problem considered was whether the
fumes produced by the combustion of certain explosives, one of which was
roburite, were injurious to health. The trial comprised the chemical
analysis of the air at the "intake," and of the vitiated air during the
firing of the shots at the "return," and also of the smoky air in the
vicinity of the shot-holes. Five pounds and a half of roburite were used
in twenty-three shots. It had been asserted that the fumes from this
explosive contained carbon-monoxide, CO, but no trace of this gas could be
discovered after the explosion. On another occasion, however, when 4.7
lbs. of roburite were exploded in twenty-three shots, the air at the
"return" showed traces of CO gas to the extent of .042 to .019 per cent.
The medical report which Drs Hume and Drummond presented to the committee
shows that they investigated every case of suspected illness produced by
exposure to fumes, and they could find no evidence of acute illness being
caused. They say, "No case of acute illness has, throughout the inquiry,
been brought to our knowledge, and we are led to the conclusion that such
cases have not occurred."

~Manufacture.~--As now made, roburite is a mixture of ammonium nitrate and
chlorinated di-nitro-benzol. The nitrate of ammonia is first dried and
ground, and then heated in a closed steam-jacketed vessel to a temperature
of 80° C., and the melted organic compound is added, and the whole stirred
until an intimate mixture is obtained. On cooling, the yellow powder is
ready for use, and is stored in straight canisters or made up into
cartridges. Owing to the deliquescent nature of the nitrate of ammonia,
the finished explosive must be kept out of contact with the air, and for
this reason the cartridges are waterproofed by dipping them in melted wax.
Roburite is made in Germany, at Witten, Westphalia; and also at the
English Company's extensive works at Gathurst, near Wigan, which have been
at work now for some eighteen years, having started in 1888. These works
are of considerable extent, covering 30 acres of ground, and are equal to
an output of 10 tons a day. A canal runs through the centre, separating
the chemical from the explosive portions of the works, and the Lancashire
and Yorkshire Railway runs up to the doors. Besides sending large
quantities of roburite itself abroad, the Company also export to the
various colonies the two components, as manufactured in the chemical
works, and which separately are quite non-explosive, and which, having
arrived at their destination, can be easily mixed in the proper
proportions.

Among the special advantages claimed for roburite are:--First, that it is
impossible to explode a cartridge by percussion, fire, or electric sparks.
If a cartridge or layer be struck with a heavy hammer, the portion struck
is decomposed, owing to the large amount of heat developed by the blow.
The remaining explosive is not in the least affected, and no detonation
whatever takes place. If roburite be mixed with gunpowder, and the
gunpowder fired, the explosion simply scatters the roburite without
affecting it in the least. In fact, the only way to explode roburite is to
detonate it by means of a cap of fulminate, containing at least 1 gramme
of fulminate of mercury. Secondly, its great safety for use in coal mines.
Roburite has the great advantage of exploding by detonation at a very low
temperature, indeed so low that a very slight amount of tamping is
required when fired in the most explosive mixture of air and coal gas
possible, and not at all in a mixture of air and coal dust--a condition in
which the use of gunpowder is highly dangerous.

Mr W.J. Orsman, F.I.C., in a paper read at the University College,
Nottingham, in 1893, gives the temperature of detonation of roburite as
below 2,100° C., and of ammonium nitrate as 1,130° C., whereas that of
blasting gelatine is as much as 3,220° C. With regard to the composition
of the fumes formed by the explosion of roburite, Mr Orsman says: "With
certain safety explosives--roburite, for instance--an excess of the
oxidising material is added, namely, nitrate of ammonia; but in this case
the excess of oxygen here causes a diminution of temperature, as the
nitrate of ammonia on being decomposed absorbs heat. This excess of oxygen
effectually prevents the formation of carbon monoxide (CO) and the oxides
of nitrogen."

The following table (A), also from Mr Orsman's paper, gives the
composition of five prominent explosives, and shows the composition of the
gases formed on explosion. The gases were collected after detonating 10
grms. of each in a closed strong steel cylinder, having an internal
diameter of 5 inches.

With respect to the influence of ammonium nitrate in lowering the
temperature of explosion of the various substances to which it is added,
it was found by a French Commission that, when dry and finely powdered,
ammonium nitrate succeeds in depreciating the heat of decomposition
without reducing the power of the explosive below a useful limit. The
following table (B) shows the composition of the explosives examined, and
the temperatures which accompanied their explosion.

                                    A
 ______________________________________________________________________
|                                   |       |                          |
|                                   |       |   Composition of Gases.  |
|                                   |Volume |__________________________|
|          Explosive.               |of Gas |       |     |      |     |
|                                   |formed.|CO_{2}.| CO. |CH_{4}|  N. |
|                                   |       |       |     | &H.  |     |
|___________________________________|_______|_______|_____|______|_____|
|                                   |       |       |     |      |     |
|                                   |       |  Per  | Per | Per  | Per |
|                                   |  c.c. | cent. |cent.|cent. |cent.|
|Gunpowder--                        |       |       |     |      |     |
|  Nitre                   75 parts |       |       |     |      |     |
|  Sulphur                 10  ''   | 2,214 |  51.3 |  3.5|  3.5 | 41.7|
|  Charcoal                15  ''   |       |       |     |      |     |
|Gelignite--                        |       |       |     |      |     |
|  Nitro-glycerine       56.5 parts |       |       |     |      |     |
|  Nitro-cotton           3.5  ''   | 4,980 |  25   |  7  |  ... | 67  |
|  Wood-meal              8.0  ''   |       |       |     |      |     |
|  KNO_{3}               32.0  ''   |       |       |     |      |     |
|Tonite--                           |       |       |     |      |     |
|  Nitro-Cotton                     | 3,750 |  30   |  8  |  ... | 62  |
|  Barium nitrate                   |       |       |     |      |     |
|Roburite--                         |       |       |     |      |     |
|  Ammonium nitrate,       86 parts |       |       |     |      |     |
|  Di-nitro-chloro-benzol  14  ''   | 4,780 |  32   | ... |  ... | 68  |
|Carbonite                          |       |       |     |      |     |
|  Nitro-glycerine         25 parts |       |       |     |      |     |
|  Wood-meal               40  ''   | 2,100 |  19   | 15  | 26   | ... |
|  Potas. nitrate          34  ''   |       |       |     |      |     |
|___________________________________|_______|_______|_____|______|_____|

                                    B
 ____________________________________________________________________
|                          |             |             |             |
|                          |   Original  | Percentage  |    Final    |
|        Explosive.        | Temperature |NH_{4}.NO_{3}| Temperature |
|                          |Co-efficient.|   added.    |Co-efficient.|
|__________________________|_____________|_____________|_____________|
|                          |             |             |             |
|Nitro-glycerine           |    3,200    |      ...    |     ...     |
|Blasting gelatine         |             |             |             |
|  (8 per cent. gun-cotton)|    3,090    |      88     |    1,493    |
|Dynamite                  |             |             |             |
|     (25 per cent. silica)|    2,940    |      80     |    1,468    |
|                          |             |             |             |
|Gun-cotton, 1             |    2,650    |      ...    |     ...     |
|                          |    2,060    |      90.5   |    1,450    |
|                          |             |             |             |
|Ammonium nitrate          |    1,130    |      ...    |     ...     |
|__________________________|_____________|_____________|_____________|

~Bellite~ is the patent of Mr Carl Lamm, Managing Director of the Rötebro
Explosive Company, of Stockholm, and is licensed for manufacture in
England. It consists of a mixture of nitrate of ammonia with di- or
tri-nitro-benzol, it has a specific gravity of 1.2 to 1.4 in its granulated
state, and 1 litre weighs 800 to 875 grms. Heated in an open vessel,
bellite loses its consistency at 90° C., but does not commence to separate
before a temperature of 200° C. is reached, when it evaporates without
exploding. If heated suddenly, it burns with a sooty flame, somewhat like
tar, but if the source of heat is removed, it will cease burning, and
assume a caramel-like structure. It absorbs very little moisture from the
air after it has been pressed, and if the operation has been performed
while the explosive is hot, the subsequent increase of weight is only 2
per cent. When subjected to the most powerful blow with a steel hammer
upon an iron plate, it neither explodes nor ignites. A rifle bullet fired
into it at 50 yards' distance will not explode it. Granulated bellite
explodes fully by the aid of fulminating mercury. Fifteen grms. of bellite
fired by means of fulminate, projected a shot from an ordinary mortar,
weighing 90 lbs., a distance of 75 yards, 15 grms. of gunpowder, under the
same conditions, throwing it only 12 yards. A weight of 7-1/2 lbs. falling
145 centimetres failed to explode 1 grm. of bellite.

Various experiments and trials have been made with this explosive by
Professor P.T. Cleve, M.P.F. Chalon, C.N. Hake, and by a committee of
officers of the Swedish Royal Artillery. It is claimed that it is a very
powerful and extremely safe explosive; that it cannot be made to explode
by friction, shock, or pressure, nor by electricity, fire, lightning, &c.,
and that it is specially adapted for use in coal mines, &c.; that it can
only be exploded by means of a fulminate detonator, and is perfectly safe
to handle and manufacture; that it does not freeze, can be used as a
filling for shells, and lastly, can be cheaply manufactured.

~Securite~ consists of 26 parts of meta-di-nitro-benzol and 74 parts of
ammonium nitrate. It is a yellow powder, with an odour of nitro-benzol. It
was licensed in 1886. It sometimes contains tri-nitro-benzol, and
tri-nitro-naphthalene. The equation of its combustion is given as

C_{6}H_{4}(NO_{2})_{2} + 10(NH_{4}NO_{3}) = 6CO_{2} + 22H_{2}O + 11N_{2}

and, like bellite and roburite, it is claimed to be perfectly safe to use
in the presence of fire damp and coal dust.[A] The variety known as
Flameless Securite consists of a mixture of nitrate and oxalate of ammonia
and di-nitro-benzol.

[Footnote A: See paper by S.B. Coxon, _North of Eng. Inst. Mining and
Mech. Eng._, 11, 2, 87.]

~Kinetite.~--A few years ago an explosive called "Kinetite"[A] was
introduced, but is not manufactured in England. It was the patent of
Messrs Petry and Fallenstein, and consisted of nitro-benzol, thickened or
gelatinised by the addition of some collodion-cotton, incorporated with
finely ground chlorate of potash and precipitated sulphide of antimony. An
analysis gave the following percentages:--

Nitro-benzol, 19.4 per cent.
Chlorate of potash, 76.9 per cent.
Sulphide of antimony nitro-cotton, 3.7 per cent.

[Footnote A: V. Watson Smith, _Jour. Soc. Chem. Ind._, January 1887.]

It requires a very high temperature to ignite it, and cannot, under
ordinary circumstances, when unconfined, be exploded by the application of
heat. It is little affected by immersion in water, unless prolonged, when
the chlorate dissolves out, leaving a practical inexplosive residue.[A] It
was found to be very sensitive to combined friction and percussion, and to
be readily ignited by a glancing blow of wood upon wood. It was also
deficient in chemical stability, and has been known to ignite
spontaneously both in the laboratory and in a magazine. It is an orange-
coloured plastic mass, and smells of nitro-benzol.

[Footnote A: Col. Cundill, R.A., "Dict. of Explosives," says: "If,
however, it be exposed to moist and dry air alternately, the chlorate
crystallises out on the surfaces, and renders the explosive very
sensitive."]

~Tonite No. 3~ contains 10 to 14 per cent. of nitro-benzol (see Tonite).
Trench's Flameless Explosive contains 10 per cent. of di-nitro-benzol,
together with 85 per cent. of nitrate of ammonia, and 5 per cent. of a
mixture of alum, and the chlorides of sodium and ammonia.

~Tri-nitro-Toluene.~--Toluene, C_{7}H_{8}, now chiefly obtained from coal-
tar, was formerly obtained by the dry distillation of tolu-balsam. It may
be regarded as methyl-benzene, or benzene in which one hydrogen is
replaced by methyl (CH_{3}), thus (C_{6}H_{5}CH_{3}), or as phenyl-
methane, or methane in which one hydrogen atom is replaced by the radical
phenyl (C_{6}H_{5}), thus (CH_{3}C_{6}H_{5}). Toluene is a colourless
liquid, boiling at 110° C., has a specific gravity of .8824 at 0° C., and
an aromatic odour. Tri-nitro-toluene is formed by the action of nitric
acid on toluene. According to Häussermann, it is more advantageous to
start with the ortho-para-di-nitro-toluene, which is prepared by allowing
a mixture of 75 parts of 91 to 92 per cent. nitric acid and 150 parts of
95 to 96 per cent. sulphuric acid to run in a thin stream into 100 parts
of para-nitro-toluene, while the latter is kept at a temperature between
60° to 65° C., and continually stirred. When the acid has all been run in,
this mixture is heated for half an hour to 80° C., and allowed to stand
till cold. The excess of nitric acid is then removed. The residue after
this treatment is a homogeneous crystalline mass of ortho-para-di-nitro-
toluene, of which the solidifying point is 69.5° C. To convert this mass
into tri-nitro derivative, it is dissolved by gently heating it with four
times its weight of sulphuric acid (95 to 96 per cent.), and it is then
mixed with 1-1/2 times its weight of nitric acid (90 to 92 per cent.), the
mixture being kept cool. Afterwards it is digested at 90° to 95° C., with
occasional stirring, until the evolution of gas ceases. This takes place
in about four or five hours.

The operation is now stopped, the product allowed to cool, and the excess
of nitric acid separated from it. The residue is then washed with hot
water and very dilute soda solution, and allowed to solidify without
purification. The solidifying point is 70° C., and the mass is then white,
with a radiating crystalline structure. Bright sparkling crystals, melting
at 81.5° C. may, however, be obtained by recrystallisation from hot
alcohol. The yield is from 100 parts di-nitro-toluene, 150 parts of the
tri-nitro derivative. Häussermann states also that 1:2:4:6 tri-nitro-
toluene can be obtained from ordinary commercial di-nitro-toluene melting
at 60° to 64° C.; but when this is used, greater precautions must be
exercised, for the reactions are more violent. Moreover, 10 per cent. more
nitric acid is required, and the yield is 10 per cent. less. He also draws
attention to the slight solubility of tri-nitro-toluene in hot water, and
to the fact that it is decomposed by dilute alkalies and alkaline
carbonates--facts which must be borne in mind in washing the substance.
This material is neither difficult nor dangerous to make. It behaves as a
very stable substance when exposed to the air under varying conditions of
temperature (-10° to +50° C.) for several months. It cannot be exploded by
flame, nor by heating it in an open vessel. It is only slightly decomposed
by strong percussion on an anvil. A fulminate detonator produces the best
explosive effect with tri-nitro-toluene. It can be used in conjunction
with ammonium nitrate, but such admixture weakens the explosive power; but
even then it is stated to be stronger than an equivalent mixture of
di-nitro-benzene and ammonium nitrate. Mowbray patented a mixture of 3
parts nitro-toluol to 7 of nitro-glycerine, also in the proportions of 1 to
3, which he states to be a very safe explosive.

~Faversham Powder.~--One of the explosives on the permitted list (coal
mines) is extensively used, and is manufactured by the Cotton Powder Co.
Ltd. at Faversham. It is composed of tri-nitro-toluol 11 parts, ammonium
nitrate 93 parts, and moisture 1 part. This explosive must be used only
when contained in a case of an alloy of lead, tin, zinc, and antimony
thoroughly waterproof; it must be used only with a detonator or electric
detonator of not less strength than that known as No. 6.

~Nitro-Naphthalene.~--Nitro-naphthalene is formed by the action of nitric
acid on naphthalene (C_{10}H_{8}). Its formula is C_{10}H_{7}NO_{2}, and
it forms yellow needles, melting at 61° C.; and of di-nitro-naphthalene
(C_{10}H_{6}(NO_{2})_{2}), melting point 216° C. There are also tri-nitro
and tetra-nitro and [alpha] and [beta] derivatives of nitro-naphthalene.
It is the di-nitro-naphthalene that is chiefly used in explosives. It is
contained in roburite, securite, romit, Volney's powder, &c. Fehven has
patented an explosive consisting of 10 parts of nitro-naphthalene mixed
with the crude ingredients of gunpowder as follows:--Nitro-naphthalene, 10
parts; saltpetre, 75 parts; charcoal, 12.5 parts; and sulphur, 12.5 parts.
He states that he obtains a mono-nitro-naphthalene, containing a small
proportion of di-nitro-naphthalene, by digesting 1 part of naphthalene,
with or without heat, in 4 parts of nitric acid (specific gravity 1.40)
for five days.

Quite lately a patent has been taken out for a mixture of nitro-
naphthalene or di-nitro-benzene with ammonium nitrate, and consists in
using a solvent for one or other or both of the ingredients, effected in a
wet state, and then evaporating off the solvent, care being taken not to
melt the hydrocarbon. In this way a more intimate mixture is ensured
between the particles of the components, and the explosive thus prepared
can be fired by a small detonator, viz., by 0.54 grms. of fulminate.
Favier's explosive also contains mono-nitro-naphthalene (8.5 parts),
together with 91.5 parts of nitrate of ammonia. This explosive is made in
England by the Miners' Safety Explosive Co. A variety of roburite contains
chloro-nitro-naphthalene. Romit consists of 100 parts ammonium nitrate and
7 parts potassium chlorate mixed with a solution of 1 part nitro-
naphthalene and 2 parts rectified paraffin oil.

~Ammonite.~--This explosive was originally made at Vilvorde in Belgium,
under the title of the Favier Explosive, consisting of a compressed hollow
cylinder composed of 91.5 per cent. of nitrate of ammonia, and 8.5 per
cent. of mono-nitro-naphthalene filled inside with loose powder of the
same composition. The cartridges were wrapped in paper saturated with
paraffin-wax, and afterwards dipped in hot paraffin to secure their being
water-tight. The Miners' Safety Explosives Co., when making this explosive
at their factory at Stanford-le-Hope, Essex, abandoned after a short trial
the above composition, and substituted di-nitro-naphthalene 11.5 per cent.
for the mono-nitro-naphthalene, and used thin lead envelopes filled with
loose powder slightly pressed in, in place of the compressed cylinders
containing loose powder. The process of manufacture is shortly as
follows:--132-3/4 lbs. of thoroughly dried nitrate of ammonium is placed
in a mill pan, heated at the bottom with live steam, and ground for about
twenty minutes until it becomes so dry that a slight dust follows the
rollers; then 17-1/2 lbs. of thoroughly dry di-nitro-naphthalene is added,
and the grinding continued for about ten minutes. Cold water is then
circulated through the bottom of the pan until the material appears of a
lightish colour and falls to powder. (While the pan is hot the whole mass
looks slightly plastic and of a darker colour than when cold.) A slide in
the bottom of the pan is then withdrawn, the whole mass working out until
the pan is empty; it is now removed to the sifting machine, brushed
through a wire sieve of about 12 holes to the inch, and is then ready for
filling into cartridges. The hard core is returned from the sifting
machine and turned into one of the pans a few minutes before the charge is
withdrawn.

The ammonite is filled into the metallic cartridges by means of an
archimedian screw working through a brass tube, pushing off the cartridges
as the explosive is fed into them against a slight back pressure; a cover
is screwed on, and they then go to the dipping room, where they are dipped
in hot wax to seal the ends; they are then packed in boxes of 5 lbs. each
and are ready for delivery. The di-nitro-naphthalene is made at the
factory. Mono-nitro-naphthalene is first made as follows:--12 parts of
commercial nitrate of soda are ground to a fine powder, and further ground
with the addition of 15 parts of refined naphthalene until thoroughly
incorporated; it is then placed in an earthenware pan, and 30 parts of
sulphuric acid of 66° B. added, 2 parts at a time, during forty-eight
hours (the rate of adding H_{2}SO_{4} depends on the condition of the
charge, and keeping it in a fluid state), with frequent agitation, day and
night, during the first three or four days, afterwards three or four times
a day. In all fourteen days are occupied in the nitration process. It is
then strained through an earthenware strainer, washed with warm water,
drained, and dried. For the purpose of producing this material in a
granulated condition, which is found more convenient for drying, and
further nitrification, it is placed in a tub, and live steam passed
through, until brought up to the boiling point (the tub should be about
half full), cold water is then run in whilst violently agitating the
contents until the naphthalene solidifies; it can then be easily drained
and dried. For the further treatment to make di-nitro-naphthalene, 18
parts of nitro-naphthalene are placed in an earthenware pan, together with
39 parts of sulphuric acid of 66° B., then 15 parts of nitric acid of 40°
B. are added, in small quantities at a time, stirring the mixture
continually. This adding of nitric acid is controlled by the fuming, which
should be kept down as much as possible. The operation takes ten to twelve
days, when 100 times the above quantities, taken in kilogrammes, are
taken. At the end of the nitration the di-nitro-naphthalene is removed to
earthenware strainers, allowed to drain, washed with hot water and soda
until all acid is removed, washed with water and dried. The di-nitro-
naphthalene gives some trouble in washing, as some acid is held in the
crystals which is liable to make its appearance when crushed. To avoid
this it should be ground and washed with carbonate of soda before drying;
an excess of carbonate of soda should not, however, be used.

~Electronite.~--This is a high explosive designed to afford safety in coal
getting. This important end has been attained by using such ingredients,
and so proportioning them, as will ensure on detonation a degree of heat
insufficient under the conditions of a "blown-out" shot, to ignite fire
damp or coal dust. It is of the nitrate of ammonium class of permitted
explosives. It contains about 75 per cent. of nitrate of ammonium, with
the addition of nitrate of barium, wood meal, and starch. The gases
resulting from detonation are chiefly water in the gaseous form, nitrogen,
and a little carbon dioxide. It is granulated with the object of
preventing missfires from ramming, to which nitrate of ammonium explosives
are somewhat susceptible. This explosive underwent some exhaustive
experiments at the experimental station near Wigan in 1895, when 8 oz. or
12 oz. charges were fired unstemmed into an admixture of coal dust and 10
per cent. of gas, without any ignition taking place. It is manufactured by
Messrs Curtis's & Harvey Ltd. at their factory, Tonbridge, Kent.

~Sprengel's Explosives.~--This is a large class of explosives. The
essential principle of them all is the admixture of an oxidising with a
combustible agent at the time of, or just before, being required for use,
the constituents of the mixture being very often non-explosive bodies.
This type of explosive is due to the late Dr Herman Sprengel, F.R.S.
Following up the idea that an explosion is a sudden combustion, he
submitted a variety of mixtures of oxidising and combustible agents to the
violent shock of a detonator of fulminate. These mixtures were made in
such proportions that the mutual oxidation or de-oxidation should be
theoretically complete. Among them are the following:--

1. One chemical equivalent of nitro-benzene to equivalents of nitric acid.

2. Five equivalents of picric acid to 13 equivalents of nitric acid.

3. Eighty-seven equivalents of nitro-naphthalene to 413 equivalents of
nitric acid.

4. Porous cakes, or lumps of chlorate of potash, exploded violently with
bisulphide of carbon, nitro-benzol, carbonic acid, sulphur, benzene, and
mixtures of these substances.

No. 1 covers the explosive known as _Hellhoffite_, and No. 2 is really
oxonite, and No. 4 resembles rack-a-rock, an explosive invented by Mr S.R.
Divine, and consisting of a mixture of chlorate of potash and nitro-
benzol. Roburite, bellite, and securite should perhaps be regarded as
belonging to the Sprengel class of explosives, otherwise this class is not
manufactured or used in England. The principal members are known as
_Hellhoffite_, consisting of a mixture of nitro-petroleum or nitro-tar
oils and nitric acid, or of meta-di-nitro-benzol and nitric acid;
_Oxonite_, consisting of picric and nitric acids; and _Panclastite_, a
name given to various mixtures, proposed by M. Turpin, such as liquid
nitric peroxide, with bisulphide of carbon, benzol, petroleum, ether, or
mineral oils.

~Picric Acid, Tri-nitro-Phenol, or Carbazotic Acid.~--Picric acid, or a
tri-nitro-phenol (C_{6}H_{2}(NO_{2})_{3}OH)[2:4:6], is produced by the
action of nitric acid on many organic substances, such as phenol, indigo,
wool, aniline, resins, &c. At one time a yellow gum from Botany Bay
(_Xanthorrhoea hastilis_) was chiefly used. One part of phenol (carbolic
acid), C_{6}H_{5}OH, is added to 3 parts of strong fuming nitric acid,
slightly warmed, and when the violence of the reaction has subsided,
boiled till nitrous fumes are no longer evolved. The resinous mass thus
produced is boiled with water, the resulting picric acid is converted into
a sodium salt by a solution of sodium carbonate, which throws down sodium
picrate in crystals.

Phenol-sulphuric acid is now, however, more generally used, and the
apparatus employed for producing it closely resembles that used in making
nitro-benzol. It is also made commercially by melting carbolic acid, and
mixing it with strong sulphuric acid, then diluting the "sulpho-
carbolic"[A] acid with water, and afterwards running it slowly into a
stone tank containing nitric acid. This is allowed to cool, where the
crude picric acid crystallises out, and the acid liquid (which contains
practically no picric acid, but only sulphuric acid, with some nitric
acid) being poured down the drains. The crude picric acid is then
dissolved in water by the aid of steam, and allowed to cool when most of
the picric acid recrystallises. The mother liquor is transferred to a tank
and treated with sulphuric acid, when a further crop of picric acid
crystals is obtained. The crystals of picric acid are further purified by
recrystallisation, drained, and dried at 100° F. on glazed earthenware
trays by the aid of steam. It can also be obtained by the action of nitric
acid on ortho-nitro-phenol, para-nitro-phenol, and di-nitro-phenol (2:4
and 2:6), but not from meta-nitro-phenol, a fact which indicates its
constitution.[B]

[Footnote A: O. and p. phenolsulphonic acids.

C_{3}H_{4}(OH).SO_{3}H + 3HNO_{3} = C_{6}H_{2}(NO_{2})_{3}OH + H_{2}SO_{4}
+ 2H_{2}O.                             (Picric acid).]

[Footnote B: Carey Lea, _Amer. Jour. Sci._, (ii.), xxxii. 180.]

Picric acid crystallises in yellow shining prisms or laminæ having an
intensely bitter taste, and is poisonous. It melts at 122.5° C., sublimes
when cautiously heated, dissolves sparingly in cold water, more easily in
hot water, still more in alcohol. It stains the skin an intense yellow
colour, and is used as a dye for wool and silk. It is a strong acid,
forming well crystallised yellow salts, which detonate violently when
heated, some of them also by percussion. The potassium salt,
C_{6}H_{2}(NO_{2})_{3}OK, crystallises in long needles very slightly
soluble in water. The sodium, ammonium, and barium salts are, however,
easily soluble in water. Picric acid, when heated, burns with a luminous
and smoky flame, and may be burnt away in large quantity without
explosion; but the mere contact of certain metallic oxides, with picric
acid, in the presence of heat, develops powerful explosives, which are
capable of acting as detonators to an indefinite amount of the acid, wet
or dry, which is within reach of their detonative influence. The formula
of picric acid is

C_{6}H_{2}|(NO_{2})_{3}
          |OH.

which shows its formation from phenol (C_{6}H_{5}OH.), three hydrogen
atoms being displaced by the NO_{2} group. The equation of its formation
from phenol is as follows:--

C_{6}H_{5}.OH + 3HNO_{3} = C_{6}H_{2}(NO_{2})_{3}OH + 3H_{2}O.

According to Berthelot, its heat of formation from its elements equals
49.1 calories, and its heat of total combustion by free oxygen is equal to
+618.4 cals. It hardly contains more than half the oxygen necessary for
its complete combustion.

2C_{6}H_{2}(NO_{2})_{3}OH + O_{10} = 12CO_{2} + 3H_{2} + 3N_{2}.

The percentage composition of picric acid is--Nitrogen, 18.34; oxygen,
49.22; hydrogen, 1.00; and carbon, 31.44, equal to 60.26 per cent. of
NO_{2}. The products of decomposition are carbonic acid, carbonic oxide,
carbon, hydrogen, and nitrogen, and the heat liberated, according to
Berthelot, would be 130.6 cals., or 570 cals. per kilogramme. The reduced
volume of the gases would be 190 litres per equivalent, or 829 litres per
kilogramme. To obtain a total combustion of picric acid it is necessary
to mix with it an oxidising agent, such as a nitrate, chlorate, &c. It has
been proposed to mix picric acid (10 parts) with sodium nitrate (10 parts)
and potassium bichromate (8.3 parts). These proportions would furnish a
third of oxygen in excess of the necessary proportion.

Picric acid was not considered to be an explosive, properly so called, for
a long time after its discovery, but the disastrous accident which
occurred at Manchester (_vide_ Gov. Rep. No. LXXXI., by Colonel (now Sir
V.D.) Majendie, C.B.), and some experiments made by Dr Duprè and Colonel
Majendie to ascertain the cause of the accident, conclusively proved that
this view was wrong. The experiments of Berthelot (_Bull. de la Soc. Chim.
de Paris_, xlix., p. 456) on the explosive decomposition of picric acid
are also deserving of attention in this connection. If a small quantity of
picric acid be heated in a moderate fire, in a crucible, or even in an
open test tube, it will melt (at 120° C. commercial acid), then give off
vapours which catch fire upon contact with air, and burn with a sooty
flame, without exploding. If the burning liquid be poured out upon a cold
slab, it will soon go out. A small quantity carefully heated in a tube,
closed at one end, can even be completely volatilised without apparent
decomposition. It is thus obvious that picric acid is much less explosive
than the nitric ethers, such as nitro-glycerol and nitro-cellulose, and
very considerably less explosive than the nitrogen compounds and
fulminates.

It would, however, be quite erroneous to assume that picric acid cannot
explode when simply heated. On the contrary, Berthelot has proved that
this is not the case. If a glass tube be heated to redness, and a minute
quantity of picric acid crystals be then thrown in, it will explode with a
curious characteristic noise. If the quantity be increased so that the
temperature of the tube is materially reduced, no explosion will take
place at once, but the substance will volatilise and then explode, though
with much less violence than before, in the upper part of the tube.
Finally, if the amount of picric acid be still further increased under
these conditions, it will undergo partial decomposition and volatilise,
but will not even deflagrate. Nitro-benzene, di-nitrobenzene, and mono-,
di-, and tri-nitro-naphthalenes behave similarly.

The manner in which picric acid will decompose is thus dependent upon the
initial temperature of the decomposition, and if the surrounding material
absorb heat as fast as it is produced by the decomposition, there will be
no explosion and no deflagration. If, however, the absorption is not
sufficient to prevent deflagration, this may so increase the temperature
of the surrounding materials that the deflagration will then end in
explosion. Thus, if an explosion were started in an isolated spot, it
would extend throughout the mass, and give rise to a general explosion.

In the manufacture of picric acid the first obvious and most necessary
precaution is to isolate the substance from other chemicals with which it
might accidentally come into contact. If pure materials only are used, the
manufacture presents no danger. The finished material, however, must be
carefully kept from contact with nitrates, chlorates, or oxides. If only a
little bit of lime or plaster become accidentally mixed with it, it may
become highly dangerous. A local explosion may occur which might have the
effect of causing the explosion of the whole mass. Picric acid can be
fired by a detonator, 5-grain fulminate, and M. Turpin patented the use of
picric acid, unmixed with any other substance, in 1885. The detonation of
a small quantity of dry picric acid is sufficient to detonate a much
larger quantity containing as much as 17 per cent. of water.

It is chiefly due to French chemists (and to Dr Sprengel) that picric acid
has come to the front as an explosive. Melinite,[A] a substance used by
the French Government for filling shells, was due to M. Turpin, and is
supposed to be little else than fused picric acid mixed with gun-cotton
dissolved in some solvent (acetone or ether-alcohol). Sir F.A. Abel has
also proposed to use picric acid, mixed with nitrate of potash (3 parts)
and picrate of ammonia (2 parts) as a filling for shells. This substance
requires a violent blow and strong confinement to explode it. I am not
aware, however, that it has ever been officially adopted in this country.
Messrs Désignolles and Brugère have introduced military powders,
consisting of mixtures of potassium and ammonium picrates with nitrate of
potassium. M. Désignolles introduced three kinds of picrate powders,
composed as follows:--

 ___________________________________________________________________
|                   |               |                   |           |
|                   | For Torpedoes |      For Guns.    | For Small |
|                   | and Shells.   | Ordinary.  Heavy. |   Arms.   |
|___________________|_______________|___________________|___________|
|                   |               |           |       |           |
| Picrate of Potash | 55-50         | 16.4- 9.6 |  9    | 28.6-22.9 |
| Saltpetre         | 45-50         | 74.4-79.7 | 80    | 65.0-69.4 |
| Charcoal          | ...           |  9.2-10.7 | 11    |  6.4- 7.7 |
|___________________|_______________|___________|_______|___________|

They were made much like ordinary gunpowder, 6 to 14 per cent. of moisture
being added when being milled. The advantages claimed over gunpowder are
greater strength, and consequently greater ballistic or disruptive effect,
comparative absence of smoke, and freedom from injurious action on the
bores of guns, owing to the absence of sulphur. Brugère's powder is
composed of ammonium picrate and nitre, the proportions being 54 per cent.
picrate of ammonia and 46 per cent. potassic nitrate. It is stable, safe
to manufacture and handle, but expensive. It gives good results in the
Chassepôt rifle, very little smoke, and its residue is small, and consists
of carbonate of potash. It is stated that 2.6 grms. used in a rifle gave
an effect equal to 5.5 grms. of ordinary gunpowder.

[Footnote A: The British Lydite and the Japanese Shimose are said to be
identical with Melinite.]

Turpin has patented various mixtures of picric acid, with gum-arabic,
oils, fats, collodion jelly, &c. When the last-named substance is diluted
in the proportion of from 3 to 5 per cent. in a mixture of ether and
alcohol, he states that the blocks of picric acid moulded with it will
explode in a closed chamber with a priming of from 1 to 3 grammes of
fulminate. He also casts picric acid into projectiles, the cast acid
having a density of about 1.6. In this state it resists the shock produced
by the firing of a cannon, when contained in a projectile, having an
initial velocity of 600 metres. It is made in the following way:--The acid
is fused in a vessel provided with a false bottom, heated to 130° to 145°
C. by a current of steam under pressure, or simply by the circulation
under the false bottom of a liquid, such as oil, chloride of zinc,
glycerine, &c., heated to the same temperature. The melted picric acid is
run into moulds of a form corresponding to that of the blocks required, or
it may be run into projectiles, which should be heated to a temperature of
about 100° C., in order to prevent too rapid solidification.

When cresylic acid (or cresol, C_{6}H_{4}(CH_{3})OH.) is acted upon by
nitric acid it produces a series of nitro compounds very similar to those
formed by nitric acids on phenol, such as sodium di-nitro-cresylate, known
in the arts as victoria yellow. Naphthol, a phenol-like body obtained from
naphthalene, under the same conditions, produces sodium di-nitro-
naphthalic acid, C_{10}H_{6}(NO_{2})_{2}O. The explosive known as
"roburite" contains chloro-nitro-naphthalene, and romit, a Swedish
explosive, nitro-naphthalene.

~Tri-nitro-cresol~, C_{7}H_{4}(NO_{2})_{3}OH.--A body very similar to tri-
nitro-phenol, crystallises in yellow needles, slightly soluble in cold
water, rather more so in boiling water, alcohol, and ether. It melts at
about 100° C. In France it is known as "Cresilite," and mixed with
melinite, is used for charging shells. By neutralising a boiling saturated
solution of tri-nitro-cresol with ammonia, a double salt of ammonium and
nitro-cresol crystallises out upon cooling, which is similar to ammonium
picrate. This salt is known as "Ecrasite," and has been used in Austria
for charging shells. It is a bright yellow solid, greasy to the touch,
melts at 100° C., is unaffected by moisture, heat, or cold, ignites when
brought into contact with an incandescent body or open flame, burning
harmlessly away unless strongly confined, and is insensitive to friction
or concussion. It is claimed to possess double the strength of dynamite,
and requires a special detonator (not less than 2 grms. of fulminate) to
provoke its full force. Notwithstanding the excellent properties
attributed to this explosive, Lieut. W. Walke ("Lectures on Explosives,"
p. 181) says, "Several imperfectly explained and unexpected explosions
have occurred in loading shells with this substance, and have prevented
its general adoption up to the present time."

~The Fulminates.~--The fulminates are salts of fulminic acid,
C_{2}N_{2}O_{2}H_{2}. Their constitution is not very well understood. Dr
E. Divers, F.R.S., and Mr Kawakita (_Chem. Soc. Jour._, 1884, pp. 13-19),
give the formulæ of mercury and silver fulminates as

    OC = N         AgOC = N
  /  |     \          |    \
Hg   |      O  and    |     O
  \  |     /          |    /
    -C = N          AgC = N

whereas Dr H.E. Armstrong, F.R.S., would prefer to write the formula of
fulminic acid

ON.C.OH.
   |
   C(N.OH),

and A.F. Holleman (_Berichte_, v. xxvi., p. 1403), assigns to mercury
fulminate the formula

   C:N.O
Hg |   |
   C:N.O,

and R. Schol (_Ber._, v. xxiii., p. 3505),

 C:NO
||    Hg.
 C:NO

They are very generally regarded as iso-nitroso compounds.

The principal compound of fulminic acid is the mercury salt commonly known
as fulminating mercury. It is prepared by dissolving mercury in nitric
acid, and then adding alcohol to the solution, 1 part of mercury and 12
parts of nitric acid of specific gravity 1.36, and 5-1/2 parts of 90 per
cent. alcohol being used. As soon as the mixture is in violent reaction, 6
parts more of alcohol are added slowly to moderate the action. At first
the mixture blackens from the separation of mercury, but this soon
vanishes, and is succeeded by crystalline flocks of mercury fulminate
which fall to the bottom of the vessel. During the reaction, large
quantities of volatile oxidation products of alcohol, such as aldehyde,
ethylic nitrate, &c., are evolved from the boiling liquid, whilst others,
such as glycollic acid, remain in solution. The mercury fulminate is then
crystallised from hot water. It forms white silky, delicate needles, which
are with difficulty soluble in cold water. In the dry state it is
extremely explosive, detonating on heating, or by friction or percussion,
as also on contact with concentrated sulphuric acid. The reaction that
takes place upon its decomposition is as follows:--

C_{2}N_{2}O_{2}Hg = Hg + 2CO + N_{2}
(284)

According to this equation 1 grm. of the fulminate should yield 235.8 c.c.
(= 66.96 litres for 284 grms.). Berthelot and Vicille have obtained a
yield of 234.2 c.c., equal to 66.7 litres for one equivalent 284 grms.

Dry fulminate explodes violently when struck, compressed, or touched with
sulphuric acid, or as an incandescent body. If heated slowly, it explodes
at 152° C., or if heated rapidly, at 187° C. It is often used mixed with
potassium chlorate in detonators. The reaction which takes place in this
case is 3C_{2}N_{2}O_{2}Hg + 2KClO_{3} = 3Hg + 6CO_{2} + 3N_{2} + 2KCl.

On adding copper or zinc to a hot saturated solution of the salt,
fulminate of copper or zinc is formed. The copper salt forms highly
explosive green crystals. There is also a double fulminate of copper of
ammonia, and of copper and potassium. Silver fulminite,
C_{2}N_{2}O_{2}Ag_{2}, is prepared in a similar manner to the mercury
salt. It separates in fine white needles, which dissolve in 36 parts of
boiling water, and are with difficulty soluble in cold water. At above
100° C., or on the weakest blow, it explodes with fearful violence. Even
when covered with water it is more sensitive than the mercury salt. It
forms a very sensitive double salt with ammonia and several other metals.
With hydrogen it forms the acid fulminate of silver. It is used in
crackers and bon-bons, and other toy fireworks, in minute quantities. Gay
Lussac found it to be composed as follows:--Carbon, 7.92 per cent.;
nitrogen, 9.24 per cent.; silver, 72.19 per cent.; oxygen, 10.65 per
cent.; and he assigned to it the formula, C_{2}N_{2}Ag_{2}O_{2}. Laurent
and Gerhardt give it the formula, C_{2}N(NO_{2})Ag_{2}, and thus suppose
it to contain nitryl, NO_{2}.

On adding potassium chloride to a boiling solution of argentic fulminate,
as long as a precipitate of argentic chloride forms, there is obtained on
evaporation brilliant white plates, of a very explosive nature, of
potassic argentic fulminate, C(NO_{2})KAg.CN, from whose aqueous solution
nitric acid precipitates a white powder of hydric argentic fulminate,
C(NO_{2})HAg.CN. All attempts to prepare fulminic acid, or nitro-aceto-
nitrile, C(NO_{2})H_{2}CN, from the fulminates have failed. There is a
fulminate of gold, which is a violently explosive buff precipitate, formed
when ammonia is added to ter-chloride of gold, and fulminate of platinum,
a black precipitate formed by the addition of ammonia to a solution of
oxide platinum, in dilute sulphuric acid.

Fulminating silver is a compound obtained by the action of ammonia on
oxide of silver. It is a very violent explosive. Pure mercury fulminate
may be kept an indefinite length of time. Water does not affect it. It
explodes at 187° C., and on contact with an ignited body. It is very
sensitive to shock and friction, even that of wood upon wood. It is used
for discharging bullets in saloon rifles. Its inflammation is so sudden
that it scatters black powder on which it is placed without igniting it,
but it is sufficient to place it in an envelope, however weak, for
ignition to take place, and the more resisting the envelope the more
violent is the shock, a circumstance that plays an important part in caps
and detonators. The presence of 30 per cent. of water prevents
decomposition, 10 per cent. prevents explosion. This is, however, only
true for small quantities, and does not apply to silver fulminate, which
explodes under water by friction. Moist fulminates slowly decompose on
contact with the oxidisable metals. The (reduced) volume of gases obtained
from 1 kilo. is according to Berthelot, 235.6 litres. The equation of its
decomposition is C_{2}HgN_{2}O_{2} = 2CO + N_{2} + Hg.

Fulminate of mercury is manufactured upon the large scale by two methods.
One of these, commonly known as the German method, is conducted as
follows:--One part of mercury is dissolved in 12 parts of nitric acid of a
specific gravity of 1.375, and to this solution 16.5 parts of absolute
alcohol are added by degrees, and heat is then slowly applied to the
mixture until the dense fumes first formed have disappeared, and when the
action has become more violent some more alcohol is added, equal in volume
to that which has already been added. This is added very gradually. The
product obtained, which is mercury fulminate, is 112 per cent. of the
mercury employed. Another method is to dissolve 10 parts of mercury in 100
parts of nitric acid of a gravity of 1.4, and when the solution has
reached a temperature of 54° C, to pour it slowly through a glass funnel
into 83 parts of alcohol. When the effervescence ceases, it is filtered
through paper filters, washed, and dried over hot water, at a temperature
not exceeding 100° C. The fulminate is then carefully packed in paper
boxes, or in corked bottles. The product obtained by this process is 130
per cent. of the mercury taken. This process is the safest, and at the
same time the cheapest. Fulminate should be kept, if possible, in a damp
state. Commercial fulminate is often adulterated with chlorate of potash.

~Detonators~, or caps, are metallic capsules, usually of copper, and
resemble very long percussion caps. The explosive is pure fulminate of
mercury, or a mixture of that substance with nitrate or chlorate of
potash, gun-powder, or sulphur. The following is a common cap mixture:--
100 parts of fulminate of mercury and 50 parts of potassium nitrate, or
100 parts of fulminate and 60 parts of meal powder. Silver fulminate is
also sometimes used in caps. There are eight sizes made, which vary in
dimensions and in amount of explosive contained. They are further
distinguished as singles, doubles, trebles, &c., according to their
number. Colonel Cundill, R.A. ("Dict. of Explosives"), gives the following
list:--

No. 1 contains 300 grms. of explosive per 1000.
 "  2     "    400   "    "     "      "    "
 "  3     "    540   "    "     "      "    "
 "  4     "    650   "    "     "      "    "
 "  5     "    800   "    "     "      "    "
 "  6     "  1,000   "    "     "      "    "
 "  7     "  1,500   "    "     "      "    "
 "  8     "  2,000   "    "     "      "    "

Trebles are generally used for ordinary dynamite, 5, 6, or 7 for
gun-cotton, blasting gelatine, roburite, &c.

In the British service percussion caps, fuses, &c., are formed of 6 parts
by weight of fulminate of mercury, 6 of chlorate of potash, and 4 of
sulphide of antimony; time fuses of 4 parts of fulminate, 6 of potassium
chlorate, 4 of sulphide of antimony, the mixture being damped with a
varnish consisting of 645 grains of shellac dissolved in a pint of
methylated spirit. Abel's fuse (No. 1) consists of a mixture of sulphide
of copper, phosphide of copper, chlorate of potash, and No. 2 of a mixture
of gun-cotton and gun-powder. They are detonated by means of a platinum
wire heated to redness by means of an electric current. Bain's fuse
mixture is a mixture of subphosphide of copper, sulphide of antimony, and
chlorate of potash.

In the manufacture of percussion caps and detonators the copper blanks are
cut from copper strips and stamped to the required shape. The blanks are
then placed in a gun-metal plate, with the concave side uppermost--a tool
composed of a plate of gun-metal, in which are inserted a number of copper
points, each of the same length, and so spaced apart as to exactly fit
each point into a cap when inverted over a plate containing the blanks.
The points are dipped into a vessel containing the cap composition, which
has been previously moistened with methylated spirit. It is then removed
and placed over the blanks, and a slight blow serves to deposit a small
portion of the cap mixture into each cap. A similar tool is then dipped
into shellac varnish, removed and placed over the caps, when a drop of
varnish from each of the copper points falls into the caps, which are then
allowed to dry. This is a very safe and efficacious method of working.

At the works of the Cotton-Powder Company Limited, at Faversham, the
fulminate is mixed wet with a very finely ground mixture of gun-cotton and
chlorate of potash, in about the proportions of 6 parts fulminate, 1 part
gun-cotton, and 1 part chlorate. The water in which the fulminate is
usually stored is first drained off, and replaced by displacement by
methyl-alcohol. While the fulminate is moist with alcohol, the gun-cotton
and chlorate mixture is added, and well mixed with it. This mixture is
then distributed in the detonators standing in a frame, and each detonator
is put separately into a machine for the purpose of pressing the paste
into the detonator shell.

At the eleventh annual meeting of the representatives of the Bavarian
chemical industries at Regensburg, attention was drawn to the unhealthy
nature of the process of charging percussion caps. Numerous miniature
explosions occur, and the air becomes laden with mercurial vapours, which
exercise a deleterious influence upon the health of the operatives. There
is equally just cause for apprehension in respect to the poisonous gases
which are evolved during the solution of mercury in nitric acid, and
especially during the subsequent treatment with alcohol. Many methods have
been proposed for dealing with the waste products arising during the
manufacture and manipulation of fulminate of mercury, but according to
Kæmmerer, only one of comparatively recent introduction appears to be at
all satisfactory. It is based upon the fact that mercuric fulminate, when
heated with a large volume of water under high pressure, splits up into
metallic mercury and non-explosive mercurial compounds of unknown
composition.

In mixing the various ingredients with mercury fulminate to form cap
mixtures, they should not be too dry; in fact, they are generally more or
less wet, and mixed in small quantities at a time, in a special house, the
floors of which are covered with carpet, and the tables with felt. Felt
shoes are also worn by the workpeople employed. All the tools and
apparatus used must be kept very clean; for granulating, hair sieves are
used, and the granulated mixture is afterwards dried on light frames, with
canvas trays the bottoms of which are covered with thin paper, and the
frames fitted with indiarubber cushions, to reduce any jars they may
receive. The windows of the building should be painted white to keep out
the rays of the sun.

Mr H. Maxim, of New York, has lately patented a composition for detonators
for use with high explosives, which can also be thrown from ordnance in
considerable quantities with safety. The composition is prepared as
follows:--Nitro-glycerine is thickened with pyroxyline to the consistency
of raw rubber. This is done by employing about 75 to 85 per cent. of
nitro-glycerine, and 15 to 25 per cent. of pyroxyline, according to the
stiffness or elasticity of the compound desired. Some solvent that
dissolves the nitro-cotton is also used. The product thus formed is a kind
of blasting gelatine, and should be in a pasty condition, in order that it
may be mixed with fulminate of mercury. The solvent used is acetone, and
the quantity of fulminate is between 75 to 85 per cent. of the entire
compound. If desired, the compound can be made less sensitive to shocks by
giving it a spongy consistency by agitating it with air while it is still
in a syrupy condition. The nitro-glycerine, especially in this latter
case, may be omitted. In some cases, when it is desirable to add a
deterring medium, nitro-benzene or some suitable gum is added.

[Illustration: FIG. 34. METHOD OF PREPARING THE CHARGE.]

The method of preparing a blasting charge is as follows:--A piece of
Bickford fuse of the required length is cut clean and is inserted into a
detonator until it reaches the fulminate. The upper portion of the
detonator is then squeezed round the fuse with a pair of nippers. The
object of this is not only to secure that the full power of the detonator
may be developed, but also to fix the fuse in the cap (Fig. 34). When the
detonator, &c., is to be used under water, or in a damp situation, grease
or tallow should be placed round the junction of the cap with the fuse, in
order to make a water-tight joint. A cartridge is then opened and a hole
made in its upper end, and the detonator pushed in nearly up to the top.
Gun-cotton or tonite cartridges generally have a hole already made in the
end of the charge. Small charges of dry gun-cotton, known as primers, are
generally used to explode wet gun-cotton. The detonators (which are often
fired by electrical means) are placed inside these primers (Fig. 35).

[Illustration: FIG. 35. PRIMER.]

One of the forms of electric exploders used is shown in Fig. 36. This
apparatus is made by Messrs John Davis & Son, and is simply a small hand
dynamo, capable of producing a current of electricity of high tension.
This firm are also makers of various forms of low tension exploders. A
charge having been prepared, as in Fig. 34, insert into the bore-hole one
or more cartridges as judged necessary, and squeeze each one down
separately with a _wooden_ rammer, so as to leave no space round the
charge, and above this insert the cartridge containing the fuse and
detonator. Now fill up the rest of the bore-hole with sand, gravel, water,
or other tamping. With gelatine dynamites a firm tamping may be used, but
with ordinary dynamite loose sand is better. The charge is now ready for
firing.

[Illustration: FIG. 36.--ELECTRIC EXPLODER.]




CHAPTER VI.

_SMOKELESS POWDERS._

Smokeless Powder in General--Cordite--Axite--Ballistite--U.S. Naval
Powder--Schultze's E.G. Powder--Indurite--Vielle Poudre--Rifleite--
Cannonite--Walsrode--Cooppal Powders--Amberite--Troisdorf--Maximite--
Picric Acid Powders, &c., &c.


The progress made in recent years in the manufacture of smokeless powders
has been very great. With a few exceptions, nearly all these powders are
nitro compounds, and chiefly consist of some form of nitro-cellulose,
either in the form of nitro-cotton or nitro-lignine; or else contain, in
addition to the above, nitro-glycerine, with very often some such
substance as camphor, which is used to reduce the sensitiveness of the
explosive. Other nitro bodies that are used, or have been proposed, are
nitro-starch, nitro-jute, nitrated paper, nitro-benzene, di-nitro-benzene,
mixed with a large number of other chemical substances, such as nitrates,
chlorates, &c. And lastly, there are the picrate powders, consisting of
picric acid, either alone or mixed with other substances.

The various smokeless powders may be roughly divided into military and
sporting powders. But this classification is very rough; because although
some of the better known purely military powders are not suited for use in
sporting guns, nearly all the manufacturers of sporting powders also
manufacture a special variety of their particular explosive, fitted for
use in modern rifles or machine guns, and occasionally, it is claimed, for
big guns also.

Of the purely military powders, the best known are cordite, ballistite,
and the French B.N. powder, the German smokeless (which contains nitro-
glycerine and nitro-cotton); and among the general powders, two varieties
of which are manufactured either for rifles or sporting guns, Schultze's,
the E.C. Powders, Walsrode powder, cannonite, Cooppal powder, amberite,
&c., &c.

~Cordite~, the smokeless powder adopted by the British Government, is the
patent of the late Sir F.A. Abel and Sir James Dewar, and is somewhat
similar to blasting gelatine. It is chiefly manufactured at the Royal
Gunpowder Factory at Waltham Abbey, but also at two or three private
factories, including those of the National Explosives Company Limited, the
New Explosives Company Limited, the Cotton-Powder Company Limited, Messrs
Kynock's, &c. As first manufactured it consisted of gun-cotton 37 per
cent., nitro-glycerine 58 per cent., and vaseline 5 per cent., but the
modified cordite now made consists of 65 per cent. gun-cotton, 30 per
cent. of nitro-glycerine, and 5 per cent. of vaseline. The gun-cotton used
is composed chiefly of the hexa-nitrate,[A] which is not soluble in nitro-
glycerine. It is therefore necessary to use some solvent such as acetone,
in order to form the jelly with nitro-glycerine. The process of
manufacture of cordite is very similar, as far as the chemical part of the
process is concerned, to that of blasting gelatine, with the exception
that some solvent for the gun-cotton, other than nitro-glycerine has to be
used. Both the nitro-glycerine and the gun-cotton employed must be as dry
as possible, and the latter should not contain more than .6 per cent. of
mineral matter and not more than 10 per cent. of soluble nitro-cellulose,
and a nitrogen content of not less than 12.5 per cent. The dry gun-cotton
(about 1 per cent. of moisture) is placed in an incorporating tank, which
consists of a brass-lined box, some of the acetone is added, and the
machine (Fig. 29), is started; after some time the rest of the acetone is
added (20 per cent. in all) and the paste kneaded for three and a half
hours. At the end of this time the Vaseline is added, and the kneading
continued for a further three and a half hours. The kneading machine (Fig.
29) consists of a trough, composed of two halves of a cylinder, in each of
which is a shaft which carries a revolving blade. These blades revolve in
opposite directions, and one makes about half the number of revolutions of
the other. As the blades very nearly touch the bottom of the trough, any
material brought into the machine is divided into two parts, kneaded
against the bottom, then pushed along the blade, turned over, and
completely mixed. During kneading the acetone gradually penetrates the
mixture, and dissolves both the nitro-cellulose and nitro-glycerine, and a
uniform dough is obtained which gradually assumes a buff colour. During
kneading the mass becomes heated, and therefore cold water is passed
through the jacket of the machine to prevent heating the mixture above the
normal temperature, and consequent evaporation of the acetone. The top of
the machine is closed in with a glass door, in order to prevent as far as
possible the evaporation of the solvent. When the various ingredients are
formed into a homogeneous mass, the mixture is taken to the press house,
where in the form of a plastic mass it is placed in cylindrical moulds.
The mould is inserted in a specially designed press, and the cordite paste
forced through a die with one or more holes. The paste is pressed out by
hydraulic pressure, and the long cord is wound on a metal drum (Fig. 38),
or cut into lengths; in either case the cordite is now sent to the drying
houses, and dried at a temperature of about 100° F. from three to fourteen
days, the time varying with the size. This operation drives off the
acetone, and any moisture the cordite may still contain, and its diameter
decreases somewhat. In case of the finer cordite, such as the rifle
cordite, the next operation is blending. This process consists in mounting
ten of the metal drums on a reeling machine similar to those used for
yarns, and winding the ten cords on to one drum. This operation is known
as "ten-stranding." Furthermore, six "ten-stranded" reels are afterwards
wound upon one, and the "sixty-stranded" reel is then ready to be sent
away, This is done in order to obtain a uniform blending of the material.
With cordite of a larger diameter, the cord is cut into lengths of 12
inches. Every lot of cordite from each manufacturer has a consecutive
number, numbers representing the size and one or more initial letters to
identify the manufacturer. These regulations do not apply to the Royal
Gunpowder Factory, Waltham Abbey. The finished cordite resembles a cord of
gutta-percha, and its colour varies from light to dark brown. It should
not look black or shrivelled, and should always possess sufficient
elasticity to return to its original form after slight bending. Cordite is
practically smokeless. On explosion a very thin vapour is produced, which
is dissipated rapidly. This smokelessness can be understood from the fact
that the products of combustion are nearly all non-condensible gases, and
contain no solid products of combustion which would cause smoke. For the
same muzzle velocity a smaller charge of cordite than gunpowder is
required owing to the greater amount of gas produced. Cordite is very slow
in burning compared to gunpowder. For firing blank cartridges cordite
chips containing no vaseline is used. The rate at which cordite explodes
depends in a measure upon the diameter of the cords, and the pressure
developed upon its mechanical state. The sizes of cordite used are given
by Colonel Barker, R.A., as follows:--

For the .303 rifle               .0375 inch diameter.
   "    12 Pr. B.L. gun          .05        "
   "        "                    .075       "
   "    4.7-inch Q.F. gun        .100       "
   "    6-inch Q.F. gun          .300       "
   "    heavy guns               .40 to .50 "

For rifles the cordite is used in bundles of sixty strands, in field-guns
in lengths of 11 to 12 inches, and the thicker cordite is cut up into
14-inch lengths. Colonel Barker says that the effect of heat upon cordite
is not greater as regards its shooting qualities than upon black powder,
and in speaking of the effect that cordite has upon the guns in which it is
used (R.A. Inst.) said that they had at Waltham Abbey a 4.7-inch Q.F. gun
that had fired 40 rounds of black powder, and 249 rounds of cordite (58
per cent. nitro-glycerine) and was still in excellent condition, and
showed very little sign of action, and also a 12-lb. B.L. gun that had
been much used and was in no wise injured.

[Footnote A: The gun-cotton used contains 12 per cent. of soluble
gun-cotton, and a nitrogen content of not less than 12.8 to 13.1 per cent.]

[Illustration: Fig. 37 Scale, 1 inch = 1 foot. Single Strand Reel.]

[Illustration: FIG. 38.--"TEN-STRANDING."]

In some experiments made by Captain Sir A. Noble,[A] with the old cordite
containing 58 per cent. nitro-glycerine, a charge of 5 lbs. 10 oz. of
cordite of 0.2 inch diameter was fired. The mean chamber crusher gauge
pressure was 13.3 tons per square inch (maximum 13.6, minimum 12.9), or a
mean of 2,027 atmospheres (max. 2,070, min. 1,970). The muzzle velocity
was 2,146 foot seconds, and the muzzle energy 1,437 foot tons. A gramme of
cordite generated 700 c.c. of permanent gases at 0° C. and 760 mm.
pressure. The quantity of heat developed was 1,260 gramme units. In the
case of cordite, as also with ballistite, a considerable quantity of
aqueous vapour has to be added to the permanent gases formed. A similar
trial, in which 12 lbs. of ordinary pebble powder was used, gave a
pressure of 15.9 tons per square inch, or a mean of 2,424 atmospheres. It
gave a 45-lb. projectile a mean muzzle velocity of 1,839 foot seconds,
thus developing a muzzle energy of 1,055 foot tons. A gramme of this
powder at 0° C. and 760 mm. generates 280 c.c. of permanent gases, and
develops 720 grm. units of heat.

[Footnote A: _Proc. Roy. Soc._, vol. lii., No. 315.]

In a series of experiments conducted by the War Office Chemical Committee
on Explosives in 1891, it was conclusively shown that considerable
quantities of cordite may be burnt away without explosion. A number of
wooden cases, containing 500 to 600 lbs. each of cordite, were placed upon
a large bonfire of wood, and burned for over a quarter of an hour without
explosion. At Woolwich in 1892 a brown paper packet containing ten cordite
cartridges was fired into with a rifle (.303) loaded with cordite, without
the explosion of a single one of them, which shows its insensibility to
shock.

With respect to the action of cordite upon guns, Sir A. Noble points out
that the erosion caused is of a totally different kind to that of black
powder. The surface of the barrel in the case of cordite appears to be
washed away smoothly by the gases, and not pitted and eaten into as with
black powder. The erosion also extends over a shorter length of surface,
and in small arms it is said to be no greater than in the case of black
powder. Sir A. Noble says in this connection: "It is almost unnecessary to
explain that freedom from rapid erosion is of very high importance in view
of the rapid deterioration of the bores of large guns when fired with
charges developing very high energies. As might perhaps be anticipated
from the higher heat of ballistite, its erosive power is slightly greater
than that of cordite, while the erosive power of cordite is again slightly
greater than that of brown prismatic. Amide powder, on the other hand,
possesses the peculiarity of eroding very much less than any other powder
with which I have experimented, its erosive power being only one-fourth of
that of the other powders enumerated."

TABLE GIVING SOME OF SIR. A. NOBLE'S EXPERIMENTS.
 ________________________________________________________________________
|                                                                        |
|                          VELOCITIES OBTAINED.                          |
|________________________________________________________________________|
|                            |          |          |          |          |
|                            | In a 40  | In a 50  | In a 75  | In a 100 |
|                            | Cal. Gun.| Cal. Gun.| Cal. Gun.| Cal. Gun.|
|____________________________|__________|__________|__________|__________|
|                            |          |          |          |          |
|                            |Foot Secs.|Foot Secs.|Foot Sees.|Foot Secs.|
|                            |          |          |          |          |
|With cordite 0.4 in. diam.  |   2,794  |   2,940  |   3,166  |   3,286  |
|  "     "    0.3      "     |   2,469  |   2,619  |   2,811  |   2,905  |
|  " ballistite 0.3 in. cubes|   2,416  |   2,537  |   2,713  |   2,806  |
|  " French B.N. for         |          |          |          |          |
|        6-inch guns         |   2,249  |   2,360  |   2,536  |   2,616  |
|  " prismatic amide         |   2,218  |   2,342  |   2,511  |   2,574  |
|                            |          |          |          |          |
|____________________________|__________|__________|__________|__________|
|                                                                        |
|                  ENERGIES REPRESENTED BY ABOVE VELOCITIES.             |
|________________________________________________________________________|
|                            |          |          |          |          |
|                            |Foot Tons.|Foot Tons.|Foot Tons.|Foot Tons.|
|                            |          |          |          |          |
|  Cordite 0.4 inch          |   5,413  |   5,994  |   6,950  |   7,478  |
|  Ballistite 0.3 inch cubes |   4,227  |   4,754  |   5,479  |   5,852  |
|  French B.N.               |   4,047  |   4,463  |   5,104  |   5,460  |
|  Prismatic amide           |   3,507  |   3,862  |   4.460  |   4,745  |
|____________________________|__________|__________|__________|__________|

And again, in speaking of his own experiments, he says: "One 4.7-inch gun
has fired 1,219 rounds, and another 953, all with full charges of cordite,
while a 6-inch gun has fired 588 rounds with full charges, of which 355
were cordite. In the whole of these guns, so far as I can judge, the
erosion is certainly not greater than with ordinary powder, and differs
from it remarkably in appearance. With ordinary powder a gun, when much
eroded, is deeply furrowed (these furrows having a great tendency to
develop into cracks), and presents much the appearance in miniature of a
very roughly ploughed field. With cordite, on the contrary, the surface
appears to be pretty smoothly swept away, while the length of the surface
eroded is considerably less."

[Illustration: FIG. 39.--COMPARATIVE PRESSURE CURVES OF CORDITE AND BLACK
POWDER. _a_, Charge, 48 lbs. powder; _b_, charge, 13 lbs. 4 oz. cordite;
_c_, charge, 13 lbs. 4 oz. powder. Weight of projectile, 100 lbs. in
6-inch gun. M.V. Cordite = 1960 feet seconds.]

The pressures given by cordite compared with those given by black powder
in the 6-inch gun will be seen upon reference to Fig. 39, which is taken
from Professor V.B. Lewes's paper, read before the Society of Arts; and
due to Dr W. Anderson, F.R.S., the Director-General of Ordnance Factories.

It has been found that the erosive effect is in direct proportion to the
nitro-glycerine present. The cordite M.D., which contains only 30 per
cent. nitro-glycerine, gives only about half the erosive effect of the old
service cordite. With regard to the heating effect of cordite and cordite
M.D. on a rifle, Mr T.W. Jones made some experiments. He fired fifty
rounds of .303 cartridges in fifteen minutes in the service rifle. Cordite
raised the temperature of the rifle 270° F., and cordite M.D. 160° F.
only.

With regard to the effect of heat upon cordite, there is some difference
of opinion. Dr W. Anderson, F.R.S., says that there is no doubt that the
effect of heat upon cordite is greater than upon black powder. At a
temperature of 110° F. the cordite used in the 4.7-inch gun is
considerably affected as regards pressure.

Colonel Barker, R.A., in reply to a question raised by Colonel Trench,
R.A. (at the Royal Artillery Institution), concerning the shooting
qualities of cordite heated to a temperature of 110° F., said: "Heating
cordite and firing it hot undoubtedly does disturb its shooting qualities,
but as far as we can see, not much more than gunpowder. I fear that we
must always expect abnormal results with heated propellants, either
gunpowder or cordite; and when fired hot, the increase in pressure and
velocities will depend upon the heat above the normal or average
temperature at which firing takes place." Colonel Barker also, in
referring to experiments that had been made in foreign climates, said:
"Climatic trials have been carried out all over the world, and they have
so far proved eminently satisfactory. The Arctic cold of the winter in
Canada, with the temperature below zero, and the tropical sun of India,
have as yet failed to shake the stability of the composition, or
abnormally injure its shooting qualities." Dr Anderson is of opinion that
cordite should not be stored in naval magazines near to the boilers.
Professor Vivian B. Lewes, in his recent Cantor Lectures before the
Society of Arts, suggests that the magazines of warships should be water-
jacketed, and maintained at a temperature that does not rise above 100° F.

~Axite.~--This powder is manufactured by Messrs Kynock Limited, at their
works at Witton, Birmingham. The main constituents of cordite are retained
although the proportions are altered; ingredients are added which impart
properties not possessed by cordite, and the methods of its manufacture
have been modified. The form has also been altered. Axite is made in the
form of a ribbon, the cross section being similar in shape to a double-
headed rail. It is claimed for this powder, that it does not corrode the
barrel in the way cordite does, that with equal pressure it gives greatly
increased velocity, and therefore flatter trajectory. That the effect of
temperature on the pressure and velocity with axite is only half that with
cordite. That the maximum flame temperature of axite is considerably less
than that of cordite, and the erosive effect is therefore considerably
less. That the deposit left in the barrel after firing axite cartridges
reduces the friction between the bullet and the barrel. It is therefore
practicable to use axite cartridges giving higher velocities than can be
employed with cordite, as with such velocities the latter would nickel the
barrel by excessive friction. It is also claimed that the accuracy is
greatly increased. The following results have been obtained with this
same time, and under the same conditions:--

~Axite~ Cartridges with 200-grain bullets.
  Velocity     2,726 F.S.
  Pressure     20.95 tons.

~Axite~ Cartridges with 215-grain bullets.
  Velocity     2,498 F.S.
  Pressure     19.24 tons.

~Axite~ Service Cartridges.
  Velocity     2,179 F.S.
  Pressure     15.76 tons.

~Cordite~ Service Cartridges.
  Velocity     2,010 F.S.
  Pressure     15.67 tons.

Five rounds from the Service axite and Service cordite were placed in an
oven and heated to a temperature of 110° F. for one hour, and were then
fired for pressure. The following results were obtained:--

                           ~Axite.~                  ~Cordite.~
  Before heating     15.76 tons per sq. in.    15.67 tons per sq. in.
  After    "         16.73   "       "         17.21   "       "
                     _____                     _____

        Increase       .97 = 6.1%               1.54 = 9.8%

Average Velocities--
  Before heating     2,150 F.S.                2,030 F.S.
  After    "         2,180  "                  2,090  "
                     _____                     _____

        Increase        30 F.S. = 1-1/2%          60.0 F.S. = 3%

In order to show the accuracy given by axite, seven rounds were fired from
a machine rest at a target fixed at 100 yards from a rifle. Six of the
seven shots could be covered by a penny piece, the other being just
outside. In order to ascertain the relative heat imparted to a rifle by
the explosion of axite and cordite, ten rounds each of axite and cordite
cartridges were fired from a .303 rifle, at intervals of ten seconds, the
temperature of the rifle barrel being taken before and after each series:--

THE RISE IN TEMPERATURE OF THE RIFLE BARREL

With axite was                   71° F.
With cordite was                 89° F.
Difference in favour of axite    18° F. = 20.2%

The lubricating action of axite is shown by the fact that a series of
cordite cartridges fired from a .303 rifle in the ordinary way, followed
by a second series, the barrel being lubricated between each shot by
firing an axite cartridge alternately with the cordite cartridge. The mean
velocity of the first series of cordite cartridges was 1,974 ft. per
second; the mean velocity of the second series was 2,071 ft. per second;
the increased velocity due to the lubricating effect of axite therefore
was 97 ft. per second. This powder, it is evident, has very many very
excellent qualities, and considerable advantages over cordite. It is
understood that axite is at present under the consideration of the British
Government for use as the Service powder.

~Ballistite.~--Nobel's powder, known as ballistite, originally consisted
of a camphorated blasting gelatine, and was made of 10 parts of camphor in
100 parts of nitro-glycerine, to which 200 parts of benzol were then
added, and 50 parts of nitro-cotton (soluble) were then steeped in this
mixture, which was then heated to evaporate off the benzol, and the
resulting compound afterwards passed between steam-heated rollers, and
formed into sheets, which were then finally cut up into small squares or
other shapes as convenient. The camphor contained in this substance was,
however, found to be a disadvantage, and its use discontinued. The
composition is now 50 per cent. of soluble nitro-cotton and 50 per cent.
of nitro-glycerine. As nitro-glycerine will not dissolve its own weight of
nitro-cotton (even the soluble variety), benzol is used as a solvent, but
is afterwards removed from the finished product, just as the acetone is
removed from cordite. About 1 per cent. of diphenylamine is added for the
purpose of increasing its stability.

The colour of ballistite is a darkish brown. It burns in layers when
ignited, and emits sparks. The size of the cubes into which it is cut is a
0.2-inch cube. Its density is 1.6. It is also, by means of a special
machine, prepared in the form of sheets, after being mixed in a wooden
trough fitted with double zinc plates, and subjected to the heating
process by means of hot-water pipes. It is passed between hot rollers, and
rolled into sheets, which are afterwards put through a cutting machine and
granulated. Sir A. Nobel's experiments[A] with this powder gave the
following results:--The charge used was 5 lbs. 8 oz., the size of the
cubes being 0.2 inch. The mean crusher-gauge pressure was 14.3 tons per
square inch (maximum, 2,210; minimum, 2,142), and average pressure 2,180
atmospheres. The muzzle velocity was 2,140 foot seconds, and the muzzle
energy 1,429 foot tons. A gramme of ballistite generates 615 c.c. of
permanent gases, and gives rise to 1,365 grm. units of heat. Ballistite is
manufactured at Ardeer in Scotland, at Chilworth in Surrey, and also in
Italy, under the name of Filite, which is in the form of cords instead of
cubes. The ballistite made in Germany contained more nitro-cellulose, and
the finished powder was coated with graphite. Its use has been
discontinued as the Service powder in Germany, but it is still the Service
powder in Italy.

[Footnote A: _Proc. Roy. Soc._, vol. lii., p. 315.]

~U.S. Naval Smokeless Powder.~--This powder is manufactured at the U.S.
Naval Torpedo Station for use in guns of all calibres in the U.S. Navy. It
is a nitro-cellulose powder, a mixture of insoluble and soluble nitro-
cellulose together with the nitrates of barium and potassium, and a small
percentage of calcium carbonate. The proportions in the case of the powder
for the 6-inch rapid-fire gun are as follows:--Mixed nitro-cellulose
(soluble and insoluble) 80 parts, barium nitrate 15 parts, potassium
nitrate 4 parts, and calcium carbonate 1 part. The percentage of nitrogen
contained in the insoluble nitro-cellulose must be 13.30±0.15, and in the
soluble 11.60±0.15, and the mean nitration strength of the mixture must be
12.75 per cent. of nitrogen. The solvent used in making the powder is a
mixture of ether (sp. gr. 0.720) 2 parts, and alcohol (95 per cent. by
volume) 1 part. The process of manufacture is briefly as follows:[A]--The
soluble and insoluble nitro-cellulose are dried separately at a
temperature from 38° to 41° C., until they do not contain more than 0.1
per cent. of moisture. The calcium carbonate is also finely pulverised and
dried, and is added to the mixed nitro-celluloses after they have been
sifted through a 16-mesh sieve. The nitrates are next weighed out and
dissolved in hot water, and to this solution is added the mixture of
nitro-celluloses and calcium carbonate with constant stirring until the
entire mass becomes a homogeneous paste. This pasty mass is next spread
upon trays and re-dried at a temperature between 38° and 48° C., and when
thoroughly dry it is transferred to the kneading machine. The ether-
alcohol mixture is now added, and the process of kneading begun. It has
been found by experiment that the amount of solvent required to secure
thorough incorporation is about 500 c.c. to each 500 grms. of dried paste.
To prevent loss of solvent due to evaporation, the kneading machine is
made vapour light. The mixing or kneading is continued until the resulting
greyish-yellow paste is absolutely homogeneous so far as can be detected
by the eye, which requires from three to four hours. The paste is next
treated in a preliminary press (known as the block press and is actuated
by hydraulic power), where it is pressed into a cylindrical mass of
uniform density and of such dimensions as to fit it for the final or
powder press. The cylindrical masses from the block press are transferred
to the final press, whence they are forced out of a die under a pressure
of about 500 lbs. per square inch. As it emerges from the final press the
powder is in the form of a ribbon or sheet, the width and thickness of
which is determined by the dimensions of the powder chamber of the gun in
which the powder is to be used. On the inner surface of the die are ribs
extending in the direction of the powder as it emerges from the press, the
object of these ribs being to score the sheets or ribbons in the direction
of their length, so that the powder will yield uniformly to the pressure
of the gases generated in the gun during the combustion of the charge. The
ribbon or sheet is next cut into pieces of a width and length
corresponding to the chamber of the gun for which it is intended, the
general rule being that the thickness of the grain (when perfectly dry)
shall be fifteen one-thousandths (.015) of the calibre of the gun, and the
length equal to the length to fit the powder chamber. Thus, in case of the
6-inch rapid-fire gun the thickness of the grain (or sheet) is 0.09 of an
inch and the length 32 inches. The sheets are next thoroughly dried, first
between sheets of porous blotting-paper under moderate pressure and at a
temperature between 15° C. and 21.5° C. for three days, and then exposed
to free circulation of the air at about 21.5° C. for seven days, and
finally subjected for a week or longer to a temperature not exceeding 38°
C. until they cease to lose weight.

[Footnote A: Lieut. W. Walke, "Lectures on Explosives," p. 330.]

The sheets, when thoroughly dried, are of a uniform yellowish-grey colour,
and of the characteristic colloidal consistency; they possess a perfectly
smooth surface, and are free from internal blisters or cracks. The
temperature of ignition of the finished powder should not be below 172°
C., and when subjected to the heat or stability test, it is required to
resist exposure to a temperature of 71° C. for thirty minutes without
causing discoloration of the test paper.

~W.A. Powder.~--This powder is made by the American Smokeless Powder
Company, and it was proposed for use in the United States Army and Navy.
It is made in several grades according to the ballistic conditions
required. It consists of insoluble gun-cotton and nitro-glycerine,
together with metallic nitrates and an organic substance used as a
deterrent or regulator. The details of its manufacture are very similar to
those of cordite, with the exception that the nitro-glycerine is dissolved
in a portion of the acetone, before it is added to the gun-cotton. The
powder is pressed into solid threads, or tubular cords or cylinders,
according to the calibre of the gun in which the powder is to be used. As
the threads emerge from the press they are received upon a canvas belt,
which passes over steam-heated pipes, and deposited in wire baskets. The
larger cords or cylinders are cut into the proper lengths and exposed upon
trays in the drying-house. The powder for small arms is granulated by
cutting the threads into short cylinders, which are subsequently tumbled,
dusted, and, if not perfectly dry, again placed upon trays in the drying-
house. Before being sent away from the factory, from five to ten lots of
500 lbs. each are mixed in a blending machine, in order to obtain greater
uniformity. The colour of the W.A. powder is very light grey, the grains
are very uniform in size, dry and hard. The powder for larger guns is of a
yellowish colour, almost translucent, and almost as hard as vulcanite. The
powder is said to be unaffected by atmospheric or climatic conditions, to
be stable, and to have given excellent ballistic results; it is not
sensitive to the impact of bullets, and when ignited burns quietly, unless
strongly confined.

Turning now to the smokeless powders, in which the chief ingredient is
nitro-cellulose in some form (either gun-cotton or nitro-lignine, &c.),
one of the first of these was Prentice's gun-cotton, which consisted of
nitrated paper 15 parts, mixed with 85 parts of unconverted cellulose. It
was rolled into a cylinder. Another was Punshon's gun-cotton powder, which
consisted of gun-cotton soaked in a solution of sugar, and then mixed with
a nitrate, such as sodium or potassium nitrate. Barium nitrate was
afterwards used, and the material was granulated, and consisted of
nitrated gun-cotton.

The explosive known as tonite, made at Faversham, was at first intended
for use as a gunpowder, but is now only used for blasting.

~The Schultze Powder.~--One of the earliest of the successful powders
introduced into this country was Schultze's powder, the invention of
Colonel Schultze, of the Prussian Artillery, and is now manufactured by
the Schultze Gunpowder Company Limited, of London. The composition of this
powder, as given in the "Dictionary of Explosives" by the late Colonel
Cundall, is as follows:--

Soluble nitro-lignine       14.83 per cent.
Insoluble       "           23.36    "
Lignine (unconverted)       13.14    "
Nitrates of K and Ba        32.35    "
Paraffin                     3.65    "
Matters soluble in alcohol   0.11    "
Moisture                     2.56    "

This powder was the first to solve the difficulty of making a smokeless,
or nearly smokeless powder which could be used with safety and success in
small arms. Previously, gun-cotton had been tried in various forms, and in
nearly every instance disaster to the weapon had followed, owing to the
difficulty of taming the combustion to a safe degree. But about 1866
Colonel Schultze produced, as the result of experiments, a nitrated wood
fibre which gave great promise of being more pliable and more easily
regulated in its burning than gun-cotton, and this was at once introduced
into England, and the Schultze Gunpowder Company Limited was formed to
commence its manufacture, which it did in the year 1868. During the years
from its first appearance, Schultze gunpowder has passed through various
modifications. It was first made in a small cubical grain formed by
cutting the actual fibre of timber transversely, and then breaking this
veneer into cubes. Later on improvements were introduced, and the wood
fibre so produced was crushed to a fine degree, and then reformed into
small irregular grains. Again, an advance was made in the form of the wood
fibre used, the fibre being broken down by the action of chemicals under
high temperature, and so producing an extremely pure form of woody fibre.
The next improvement was to render the grains of the powder practically
waterproof and less affected by the atmospheric influences of moisture and
dryness, and the last improvement to the process was that of hardening the
grains by means of a solvent of nitro-lignine, so as to do away with the
dust that was often formed from the rubbing of the grains during transit.

Minor modifications have from time to time also been made, in order to
meet the gradual alteration which has taken place during this long period
in the manufacture of sporting guns and cartridge cases to be used with
this powder, but through all its evolution this Company has adhered to the
first idea of using woody fibre in preference to cotton as the basis of
their smokeless powder, as experience has confirmed the original opinion
that a powder can be thus made less sensitive to occasional differences in
loading, and more satisfactory all round than when made from the cotton
base. The powder has always been regulated so that bulk for bulk it
occupies the same measure as the best black powder, and as regards its
weight, just one half of that of black.

The process of manufacture of this powder is briefly as follows:--

Wood of clean growth is treated by the well-known sulphite process for
producing pure woody fibre, which is very carefully purified, and this,
after drying, is steeped in a mixture of nitric and sulphuric acids, to
render it a nitro-compound and the explosive base of the powder. This
nitro compound is carefully purified until it stands the very high purity
requirements of the Home Office, and is then ground with oxygen-bearing
salts, &c., and the whole is formed into little irregular-shaped grains of
the desired size, which grains are dried and hardened by steeping in a
suitable solvent for the nitro compound, and after finally drying,
sifting, &c., the powder is stored in magazines for several months before
it is issued. When issued, a very large blend is made of many tons weight,
which ensures absolute uniformity in the material.

There is in England a standard load adopted by every one for testing a
sporting powder; this charge is 42 grains of powder and 1-1/8 oz. No. 6
shot--this shot fired from a 12-bore gun, patterns being taken at 40
yards, the velocity at any required distance.

The standard muzzle velocity of Schultze gunpowder is 1,220 feet per
second.

The mean 40 yards ditto is 875 feet per second.

The mean 20 yards ditto is 1,050 feet per second.

The internal pressure not to exceed 3.5 tons.

This Company also manufactures a new form of powder, known as Imperial
Schultze. It is a powder somewhat lighter in gravity; 33 grains occupies
the bulk charge, as compared with the 42 grains of the old. It follows in
its composition much the lines of the older powder, but it is quite free
from smoke, and leaves no residue whatever.

~The E.G. Powder.~--This is one of the oldest of the nitro powders. It was
invented by Reid and Johnson in 1882. It is now manufactured by the E.G.
Powder Company Limited, at their factory near Dartford, Kent, and in
America by the Anglo-American E.G. Powder Company, at New Jersey. The
basis of this powder is a fine form of cellulose, derived from cotton,
carefully purified, and freed from all foreign substances, and carefully
nitrated. Its manufacture is somewhat as follows:--Pure nitro-cotton, in
the form of a fine powder, is rotated in a drum, sprinkled with water, and
the drum rotated until the nitro-cotton has taken the form of grains. The
grains are then dried and moistened with ether-alcohol, whereby the
moisture is gelatinised, and afterwards coloured with aurine, which gives
them an orange colour. They are then dried and put through a sieve, in
order to separate the grains which may have stuck together during the
gelatinising process.

Since its introduction soon after 1881, E.G. powder has undergone
considerable modifications, and is now a distinctly different product from
a practical point of view. It is now and has been since 1897 what is known
as a 33-grain powder, that is to say, the old standard charge of 3 drams
by measure for a 12-bore gun weighs 33 grains, as compared with 42 grains
for the original E.G. and other nitro powders. This improvement was
effected by a reduction of the barium nitrate and the use of nitro-
cellulose of a higher degree of nitration, and also more gelatinisation in
manufacture. The granules are very hard, and resist moisture to an extent
hitherto unattainable by any "bulk" powder.

Irregularities of pressure in loading have also a minimum effect by reason
of the hardness of the grains. The colouring matter used is aurine, and
the small quantity of nitrate used is the barium salt. The powder is
standardised for pressure velocity with Boulengé chronograph,[A] pattern
and gravimetric density by elaborate daily tests, and is continually
subjected to severe trials for stability under various conditions of
storage, the result being that it may be kept for what in practice amount
to indefinite periods of time, either in cartridges or in bulk without any
alteration being feared. The E.C. powders are used in sporting guns. No. 1
and No. 2 E.C. are not at present manufactured, E.C. No. 3 having taken
their place entirely. Since 1890 these powders have been manufactured
under the Borland-Johnson patents, these improved powders being for some
time known as the J.B. powders. The E.C. No. 1 was superseded by the E.C.
No. 2, made under the Borland-Johnson patents, and this in its turn by the
E.C. No. 3 (in 1897).

[Footnote A: Invented in 1869 by Major Le Boulengé, Belgian Artillery. It
is intended to record the mean velocity between any two points, and from
its simplicity and accuracy is largely employed. Other forms have been
invented by Capt. Bréger, French Artillerie de la Marine, and Capt.
Holden, R.A.]

~Indurite~ is the invention of Professor C.E. Munroe, of the U.S. Naval
Torpedo Station. It is made from insoluble nitro-cotton, treated in a
particular manner by steam, and mixed with nitro-benzene. The _Dupont_
powder is very similar to _Indurite_. M.E. Leonard, of the United States,
invented a powder consisting of 75 parts of nitro-glycerine, 25 parts of
gun-cotton, 5 parts of lycopodium powder, and 4 parts of urea crystals
dissolved in acetone. The French smokeless powder, Vielle poudre (poudre
B), used in the Lebel rifle, is a mixture of nitro-cellulose and tannin,
mixed with barium and potassium nitrates. It gives a very feeble report,
and very little bluish smoke. The Nobel Company is said to be perfecting a
smokeless powder in which the chief ingredients are nitro-amido- and tri-
nitro-benzene. C.O. Lundholm has patented (U.S. Pat, 701,591, 1901) a
smokeless powder containing nitro-glycerine 30, nitro-cellulose 60, diamyl
phthalate 10 (or diamyl phthalate 5, and mineral jelly 5). The diamyl
phthalate is added, with or without the mineral jelly to nitro-glycerine
and nitro-cellulose.

~Walsrode Powder.~--The smokeless powder known as Walsrode powder consists
of absolutely pure gelatinised nitro-cellulose, grained by a chemical not
a mechanical process, consequently the grains do not need facing with
gelatine to prevent their breaking up, as is the case with many nitro
powders. For this same reason, as well as from the method of getting rid
of the solvent used, the Walsrode has no tendency whatever to absorb
moisture. In fact, it can lie in water for several days, and when taken
out and dried again at a moderate temperature will be found as good as
before. Nor is it influenced by heat, whether dry or damp, and it can be
stored for years without being in the least affected. It is claimed also
that it heats the barrels of guns much less than black powder, and does
not injure them.

The standard charge is 30 grains, and it is claimed that with this charge
Walsrode powder will prove second to none. A large cap is necessary, as
the grains of this powder are very hard, and require a large flame to
properly ignite them. In loading cartridges for sporting purposes, an
extra felt wad is required to compensate for the small space occupied by
the charge; but for military use the powder can be left quite loose. The
gas pressure of this powder is low (in several military rifles only one-
half that of other nitros), and the recoil consequently small; and it is
claimed that with the slight increase of the charge (from 29 to 30 grs.)
both penetration and initial velocity will be largely increased, whilst
the gas pressure and recoil will not be greater.

This powder was used at Bisley, at the National Rifle Association's
Meeting, with satisfactory results. It is made by the Walsrode Smokeless
and Waterproof Gunpowder Company. The nitro-cotton is gelatinised by means
of acetic ether, and the skin produced retards burning. The nitro-cotton
is mixed with acetic ether, and when the gelatinisation has taken place,
the plastic mass is forced through holes in a metal plate into strips,
which are then cut up into pieces the size of grains. The M.H. Walsrode
powder is a leaflet powder, light in colour, about 40 grains of which give
a muzzle velocity of 1,350 feet and a pressure of 3 tons. It is, like the
other Walsrode powders, waterproof and heat-proof.

~Cooppal Powder~ is manufactured by Messrs Cooppal & Co. at their
extensive powder works in Belgium. It consists of nitro-jute or nitro-
cotton, with or without nitrates, treated with a solvent to form a
gelatinised mass. There are a great many varieties of this powder. One
kind is in the form of little squares; another, for use in Hotchkiss guns,
is formed into 3-millimetre cubes, and is black. Other varieties are
coloured with aniline dyes of different colours.

~Amberite~ is a nitro-cellulose powder of the 42-grain type of sporting
gunpowders, and is manufactured by Messrs Curtis's & Harvey Limited, at
their Smokeless Powder Factory, Tonbridge, Kent. It consists of a mixture
of nitro-cellulose, paraffin, barium, nitrate, and some other ingredients.
It is claimed for this powder that it combines hard shooting with safety,
great penetration, and moderate strain on the gun. It is hard and tough in
grain, and may be loaded like black powder, and subjected to hard friction
without breaking into powder, that it is smokeless, and leaves no residue
in the gun. The charge for 12 bores is 42 grains by weight, and 1-1/8 oz.
or 1-1/16 oz. shot. The powders known as cannonite[A] and ruby powder,
also manufactured by Messrs Curtis's & Harvey Limited, are analogous
products having the same general characteristics.

[Footnote A: For further details of cannonite, see First Edition, p. 181.]

~Smokeless Diamond~, also manufactured by the above mentioned firm, is a
nitro-cellulose powder of the 33-grain type of sporting gunpowders. It was
invented by Mr H.M. Chapman. The manufacture of Smokeless Diamond, as
carried out at Tonbridge, is shortly as follows:--The gun-cotton, which is
the chief ingredient of this powder, is first stoved, then mixed with
certain compounds which act as moderators, and after the solvents are
added, is worked up into a homogeneous plastic condition. It then
undergoes the processes of granulation, sifting, dusting, drying, and
glazing. In order to ensure uniformity several batches are blended
together, and stored for some time before being issued for use.

It is claimed for this powder that it is quick of ignition, the quickness
being probably due to the peculiar structure of the grains which, when
looked at under the microscope, have the appearance of coke. The charge
for a 12 bore is 33 grains and 1-1/16 oz. shot, which gives a velocity of
1,050 feet per second, and a pressure of 3 tons per square inch.

~Greiner's Powder~ consists of nitro-cellulose, nitro-benzol, graphite,
and lampblack.

~B.N. Powder.~--This powder is of a light grey or drab colour, perfectly
opaque, and rough to the touch. It consists of a mixture, nitro-cellulose
and the nitrates of barium and potassium. Its composition is as follows:--

Insoluble nitro-cellulose   29.13 parts
Soluble nitro-cellulose     41.31   "
Barium nitrate              19.00   "
Potassium nitrate            7.97   "
Sodium carbonate             2.03   "
Volatile matter              1.43   "

This powder is a modification of the Poudre B., or Vieille's powder
invented for use in the Lebel rifle, and which consisted of a mixture of
the nitro-celluloses with paraffin.

~Von Foster's Powder~ contains nothing but pure gelatinised nitro-
cellulose, together with a small quantity of carbonate of lime.

The German ~Troisdorf Powder~ is a mixture of gelatinised nitro-cellulose,
with or without nitrates.

~Maximite~ is the invention of Mr Hudson Maxim, and is a nitro-compound,
the base being gun-cotton. The exact composition and method of manufacture
are, however, kept secret. It is made by the Columbia Powder Manufacturing
Company, of New York, and in two forms--one for use as a smokeless rifle
powder, and the other for blasting purposes.

~Wetteren Powder.~--This powder was manufactured at the Royal Gunpowder
Factory at Wetteren, and used in the Belgian service. Originally it was a
mixture of nitro-glycerine and nitro-cellulose, with amyl acetate as
solvent. Its composition has, however, been altered from time to time. One
variety consists chiefly of nitro-cellulose, with amyl acetate as solvent.
It is of a dark brown colour, and of the consistency of indiarubber. It is
rolled into sheets and finally granulated.

~Henrite~ is a nitro-cellulose powder.

~Normal Powder.~--The Swedish powder known as "Normal" Smokeless Powder,
and manufactured by the Swedish Powder Manufacturing Company, of
Landskrona, Sweden, and used for some years past in the Swiss Army, is
made in four forms. For field guns of 8.4 calibre, it is used in the form
of cylindrical grains of a yellow colour, of a diameter of .8 to .9 mm.
and density of .790--about 840 grains of it go to one gun. For rifles, it
is used in the form of grey squares, density .750, and 1 grm. equals about
1,014 grains. One hundred rounds of this powder, fired in eighteen
minutes, raised the temperature of the gun barrel 284° F. A nitro-
glycerine powder, fired under the same conditions, gave a temperature of
464° F.

This powder is said to keep well--a sample kept 3-1/2 years gave as good
results as when first made--is easy to make, very stable, ignites easily,
not very sensitive to shock or friction, is very light, &c. Eight hundred
rounds fired from a heavy gun produced no injury to the interior of the
weapon. Samples kept for eleven months in the moist atmosphere of a
cellar, when fired gave a muzzle velocity of 1,450 ft. secs. and pressure
of 1,312 atmospheres, and the moisture was found to have risen from 1.2 to
1.6 per cent. After twenty-three months in the damp it contained 2 per
cent. moisture, gave a muzzle velocity of 1,478 ft. sees., and pressure of
1,356 atmospheres. In a 7.5 millimetre rifle, 13.8 grm. bullet, and charge
of 2 grms., it gives a muzzle velocity of 2,035 ft. secs. and a pressure
of 2,200 atmospheres. In the 8.4 cm. field-gun, with charge of 600 grms.,
and projectile of 6.7 kilogrammes, muzzle velocity was equal to 1,640 ft.
secs. and pressure 1,750. A sample of the powder for use in the .303 M.
rifle, lately analysed by the author, gave the following result:--

Gun-cotton                96.21 per cent.
Soluble cotton             1.80     "
Non-nitrated cotton       trace.
Resin and other matters    1.99     "
                        _______

                         100.00

The various forms of powder invented and manufactured by Mr C.F. Hengst
are chiefly composed of nitrated straw that has been finely pulped. The
straw is treated first with acids and afterwards with alkalies, and the
result is a firm fibrous substance which is granulated. It is claimed that
this powder is entirely smokeless and flameless, that it does not foul the
gun nor heat the barrel, and is at the same time 150 per cent. stronger
than black powder.

The German "Troisdorf" powder consists of nitro-cellulose that has been
gelatinised together with a nitrate. Kolf's powder is also gelatinised
with nitro-cellulose. The powders invented by Mr E.J. Ryves contain nitro-
glycerine, nitro-cotton, castor-oil, paper-pulp, and carbonate of
magnesia. Maxim powder contains both soluble and insoluble nitro-
cellulose, nitro-glycerine, and carbonate of soda. The smokeless powder
made by the "Dynamite Actiengesellschaft Nobel" consists of nitro-starch
70 to 99 parts, and of di- or tri-nitro-benzene 1 to 30 parts.

An American wood powder, known as Bracket's Sporting Powder, consists of
soluble and insoluble nitro-lignine, mixed with charred lignine, humus,
and nitrate of soda. Mr F.H. Snyder, of New York, is the inventor of a
shell powder known as the "Snyder Explosive," consisting of 94 per cent.
nitro-glycerine, 6 per cent. of soluble nitro-cotton, and camphor, which
is said to be safe in use. Experiments were made with it in a 6-inch
rifled gun, fired at a target 220 yards away, composed of twelve 1-inch
steel plates welded together, and backed with 12-inch and 14-inch oak
beams, and weighing 20 tons. The shots entirely destroyed it. The charge
of explosive used was 10 lbs. in each shell.

~Comparative Tests of Black and Nitro Powders, from "American Field."~--
The results given in table below were obtained at the German Shooting
Association's grounds at Coepenick, Berlin. Penetration was calculated by
placing frames, each holding five cards of 1 millimetre in thickness
(equals .03937 inch), and 3 inches apart, in a bee-line, at distances of
20 inches. Velocity, pattern, and penetration were taken at 40 yards from
the muzzle of a 12-gauge choke-bore double-barrel gun. Gas pressure was
taken by a special apparatus. All shells were loaded with 1-1/8 oz. of No.
3 shot, equal to 120 pellets, and the number given below represents the
average number in the 30-inch pattern. The number of sheets passed through
gives the average penetration. One atmosphere equals pressure equal to 1
kilogramme (2.2 lbs.) on the square centimetre, hence 1,000 atmospheres
equal 2,200 lbs. on the square centimetre. The E.C., Schultze, and
Walsrode powders were loaded in Elcy's special shells, 2-1/2 inches long.
The averages were taken from a large number of shots, and the same series
of shots fired under precisely the same conditions.

 _______________________________________________________________________
|                  |            |           |            |              |
|                  |    Gas     |           |            |              |
|                  | Pressure.  | Velocity. |  Pattern.  | Penetration. |
|__________________|____________|___________|____________|______________|
|                  |            |           |            |              |
|                  |Atmospheres.|  Metres.  |            |   Sheets.    |
|                  |            |           |            |              |
|Fine-grained black|            |           |            |              |
|powder, standard  |            |           |            |              |
|charge            |   514.2    |   280     | 78.6 = 66% |    19.O      |
|                  |            |           |            |              |
|Coarse-grained    |            |           |            |              |
|black powder,     |            |           |            |              |
|standard charge   |   473.4    |   281.4   | 78.2 = 65% |    19.4      |
|                  |            |           |            |              |
|Schultze powder,  |            |           |            |              |
|42 grains         |   921.0    |   290.0   | 64.2 = 54% |    20.2      |
|                  |            |           |            |              |
|Schultze powder,  |            |           |            |              |
|45 grains         |  1052.8    |   305.8   | 52.2 = 42% |    20.6      |
|                  |            |           |            |              |
|E.G. smokeless,   |            |           |            |              |
|42 grains         |   920.2    |   298.4   | 81.4 = 67% |    18.8      |
|                  |            |           |            |              |
|Walsrode,         |            |           |            |              |
|29 grains         |   586.4    |   280.6   | 83.0 = 69% |    19.0      |
|__________________|____________|___________|____________|______________|

Barometer, 760 mm. Thermometer, 30° C. Hydrometer = 65. Wind, S.W.

~Picric Powders.~--The chief of these is _Melinite_, the composition of
which is not known with certainty. It is believed to be melted picric acid
together with gun-cotton dissolved in acetone or ether-alcohol. Walke
gives the following proportions--30 parts of tri-nitro-cellulose dissolved
in 45 parts of ether-alcohol (2 to 1), and 70 parts of fused and
pulverised picric acid. The ether-alcohol mixture is allowed to evaporate
spontaneously, and the resulting cake granulated. The French claim,
however, that the original invention has been so modified and perfected
that the melinite of to-day cannot be recognised in the earlier product.
Melinite has a yellow colour, is almost without crystalline appearance,
and when ignited by a flame or heated wire, it burns with a reddish-yellow
flame, giving off copious volumes of black smoke. Melinite as at present
used is said to be a perfectly safe explosive, both as regards
manufacture, handling, and storage.

_Lyddite_,[A] the picric acid explosive used in the British service, is
supposed to be identical with the original melinite, but its composition
has not been made public.

[Footnote A: Schimose, the Japanese powder, is stated to be identical with
Lyddite and Melinite (_Chem. Centr._, 1906, 1, 1196).]

Picrates are more often used than picric acid itself in powders. One of
the best known is _Brugère's Powder_, which is a mixture of 54 parts of
picrate of ammonia and 45 parts of saltpetre. It is stable and safe to
manufacture. It has been used in the Chassepôt rifle with good results,
gives little smoke, and a small residue only of carbonate of potash.

The next in importance is _Designolle's Powder_, made at Bouchon,
consisting of picrate of potash, saltpetre, and charcoal. It was made in
three varieties, viz., for rifles, big guns, and torpedoes and shells.
These powders are made much in the same way as gunpowder. The advantages
claimed for them over gunpowder are, greater strength, comparative absence
of smoke, and freedom from injurious action on the bores of guns.

_Emmensite_ is the invention of Dr Stephen Emmens, of the United States.
The Emmens "crystals" are produced by treating picric acid with fuming
nitric acid of specific gravity of 1.52. The acid dissolves with the
evolution of red fumes. The liquid, when cooled, deposits crystals, stated
to be different to picric acid, and lustrous flakes. These flakes, when
heated in water, separate into two new bodies. One of these enters into
solution and forms crystals unlike the first, while the other body remains
undissolved. The acid crystals are used mixed with a nitrate.

Emmensite has been subjected to experiment by the direction of the U.S.
Secretary for War, and found satisfactory. A sample of Emmensite, in the
form of a coarse powder, was first tried in a pistol, and proved superior
in propelling power to ordinary gunpowder. When tested against explosive
gelatine, it did very good work in shattering iron plates. It is claimed
for this explosive that it enjoys the distinction of being the only high
explosive which may be used both for firearms and blasting. This view is
supported by the trials made by the American War Office authorities, and
shows Emmensite to be a useful explosive both for blasting and as a
smokeless powder. Its explosive power, as tested, is 283 tons per square
inch, and its specific gravity is 1.8.

Abel proposed to use picric acid for filling shells. His _Picric Powder_
consisted of 3 parts of saltpetre, and 2 of picrate of ammonia.
_Victorite_ consists of chlorate of potash, picric acid, and olive oil,
and with occasionally some charcoal. It has the form of a coarse yellowish
grey powder, and leaves an oily stain on paper, and it is very sensitive
to friction and percussion. The composition is as follows:--KClO_{3} = 80
parts; picric acid, 110 parts; saltpetre, 10 parts; charcoal, 5 parts. It
is not manufactured in England. _Tschiner's Powder_ is very similar to
Victorite in composition, but contains resin. A list of the chief picric
powders will be found in the late Colonel J.P. Cundill, R.A.'s "Dictionary
of Explosives."




CHAPTER VII.

_ANALYSIS OF EXPLOSIVES._

Kieselguhr Dynamite--Gelatine Compounds--Tonite--Cordite--Vaseline--
Acetone--Scheme for Analysis of Explosives--Nitro-Cotton--Solubility Test--
Non-Nitrated Cotton--Alkalinity--Ash and Inorganic Matter--Determination
of Nitrogen--Lungé, Champion and Pellet's, Schultze-Tieman, and Kjeldahl's
Methods--Celluloid--Picric Acid and Picrates--Resinous and Tarry Matters--
Sulphuric Acid and Hydrochloric Acid and Oxalic Acid--Nitric Acid--
Inorganic Impurities--General Impurities and Adulterations--Potassium
Picrate, &c.--Picrates of the Alkaloids--Analysis of Glycerine--Residue--
Silver Test--Nitration--Total Acid Equivalent--Neutrality--Free Fatty
Acids--Combined Fatty Acids--Impurities--Oleic Acid--Sodium Chloride--
Determination of Glycerine--Waste Acids--Sodium Nitrate--Mercury
Fulminate--Cap Composition--Table for Correction of Volumes of Gases, for
Temperature and Pressure


~Kieselguhr Dynamite.~--The material generally consists of 75 per cent. of
nitro-glycerine and 25 per cent. of the infusorial earth kieselguhr. The
analysis is very simple, and may be conducted as follows:--Weigh out about
10 grms. of the substance, and place over calcium chloride in a desiccator
for some six to eight days, and then re-weigh. The loss of weight gives
the moisture. This will generally be very small, probably never more than
1 per cent., and usually less.

Mr James O. Handy, in order to save time, proposes to dry dynamite in the
following manner. He places 1 grm. of the material in a porcelain crucible
1 inch in diameter. The crucible is then supported at the bottom of an
extra wide-mouthed bottle of about 600 c.c. capacity. Air, which has been
dried by bubbling through strong sulphuric acid, is now drawn over the
surface of the sample for three hours by means of an ordinary aspirator.
The air should pass approximately at the rate of 10 c.c. per second. The
tube by which the dry air enters the bottle extends to within 1 inch of
the crucible containing the dynamite. An empty safety bottle is connected
with the inlet, and another with the outlet of the wide-mouthed bottle.
The first guards against the mechanical carrying over by the air current
of sulphuric acid from the acid bottle into the sample, whilst the second
prevents spasmodic outbursts of water from the exhaust from reaching the
sample. The method also gave satisfactory results with nitro-glycerine.
The dry substance may now be wrapped in filter paper, the whole weighed,
and the nitro-glycerine extracted in the Soxhlet apparatus with ether. The
ether should be distilled over at least twenty-four times.

I have found, however, that much quicker, and quite as accurate, results
may be obtained by leaving the dynamite in contact with ether in a small
Erlenmeyer flask for twenty-four hours--leaving it overnight is better--
and decanting, and again allowing the substance to remain in contact with
a little fresh ether for an hour, and finally filtering through a weighed
filter, drying at 100° C., and weighing. This gives the weight of the
kieselguhr. The nitro-glycerine must be obtained by difference, as it is
quite useless to evaporate down the ethereal solution to obtain it, as it
is itself volatile to a very considerable extent at the temperature of
evaporation of the ether, and the result, therefore, will always be much
too low. The dry guhr can, of course, be examined, either qualitatively or
quantitatively, for other mineral salts, such as carbonate of soda, &c. An
actual analysis of dynamite No. 1 made by the author at Hayle gave--
Moisture, 0.92 per cent.; kieselguhr, 26.15 per cent.; and nitro-
glycerine, 72.93 per cent., the last being obtained by difference.

~Nitro-Glycerine.~--It is sometimes desired to test an explosive substance
for nitro-glycerine. If an oily liquid is oozing from the substance, soak
a drop of it in filter paper. If it is nitro-glycerine it will make a
greasy spot. If the paper is now placed upon an iron anvil, and struck
with an iron hammer, it will explode with a sharp report, if lighted it
burns with a yellowish to greenish flame, emitting a crackling sound, and
placed upon an iron plate and heated from beneath, it explodes sharply.

If a few drops of nitro-glycerine are placed in a test tube, and shaken up
with methyl-alcohol (previously tested with distilled water, to see that
it produces no turbidity), and filtered, on the addition of distilled
water, the solution will become milky, and the nitro-glycerine will
separate out, and finally collect at the bottom of the tube.

If to a solution of a trace of nitro-glycerine in methyl-alcohol, a few
drops of a solution, composed of 1 volume of aniline, and 40 volumes
sulphuric acid (1.84) be added, a deep purple colour will be produced.
This colour changes to green upon the addition of water. If it is
necessary to determine the nitro-glycerine quantitatively in an explosive,
the scheme on page 213 may be followed. Ether is the best solvent to use.
Nitrogen should be determined in the nitrometer.

~Gelatine Compounds.~--The simplest of these compounds is, of course,
blasting gelatine, as it consists of nothing but nitro-cotton and nitro-
glycerine, the nitro-cellulose being dissolved in the glycerine to form a
clear jelly, the usual proportions being about 92 per cent. of nitro-
glycerine to 8 per cent. nitro-cotton, but the cotton is found as high as
10 per cent. in some gelatines. Gelatine dynamite and gelignite are
blasting gelatines, with varying proportions of wood-pulp and saltpetre
(KNO_{3}) mixed with a thin blasting gelatine. The method of analysis is
as follows:--Weigh out 10 grms. of the substance, previously cut up into
small pieces with a platinum spatula, and place over calcium chloride in a
desiccator for some days. Reweigh. The loss equals moisture. This is
generally very small. Or Handy's method may be used. The dried sample is
then transferred to a small thistle-headed funnel which has been cut off
from its stem, and the opening plugged with a little glass wool, and round
the top rim of which a piece of fine platinum wire has been fastened, in
order that it may afterwards be easily removed from the Soxhlet tube. The
weight of this funnel and the glass wool must be accurately known. It is
then transferred to the Soxhlet tube and exhausted with ether, which
dissolves out the nitro-glycerine. The weighed residue must afterwards be
treated in a flask with ether-alcohol to dissolve out the nitro-cotton.

But the more expeditious method, and one quite as accurate, is to transfer
the dried gelatine to a conical Erlenmeyer flask of about 500 c.c.
capacity, and add 250 c.c. of a mixture of ether-alcohol (2 ether to 1
alcohol), and allow to stand overnight. Sometimes a further addition of
ether-alcohol is necessary. It is always better to add another 300 c.c.,
and leave for twenty minutes or so after the solution has been filtered
off. The undissolved portion, which consists of wood-pulp, potassium
nitrate, and other salts, is filtered off through a linen or paper filter,
dried and weighed.

~Solution.~--The ether-alcohol solution contains the nitro-cotton and the
nitro-glycerine in solution.[A] To this solution add excess of chloroform
(about 100 c.c. will be required), when the nitro-cellulose will be
precipitated in a gelatinous form. This should be filtered off through a
linen filter, and allowed to drain. It is useless to attempt to use a
filter pump, as it generally causes it to set solid. The precipitated
cotton should then be redissolved in ether-alcohol, and again precipitated
with chloroform (20 c.c. of ether-alcohol should be used). This precaution
is absolutely necessary, if the substance has been treated with ether-
alcohol at first instead of ether only, otherwise the results will be much
too high, owing to the gelatinous precipitate retaining very considerable
quantities of nitro-glycerine. The precipitate is then allowed to drain as
completely as possible, and finally allowed to dry in the air bath at 40°
C., until it is easily detached from the linen filter by the aid of a
spatula, and is then transferred to a weighed watch-glass, replaced in the
oven, and dried at 40° C. until constant in weight. The weight found,
calculated upon the 10 grms. taken, gives the percentage of nitro-
cellulose.

[Footnote A: If the substance has been treated with ether alone in the
Soxhlet, the nitro-glycerine will of course be dissolved out first, and
the ether-alcohol solution will only contain the nitro-cellulose.]

~The Residue~ left after treating the gelatine with ether-alcohol is, in
the case of blasting gelatine, very small, and will probably consist of
nothing but carbonate of soda. It should be dried at 100° C. and weighed,
but in the case of either gelignite or gelatine dynamite this residue
should be transferred to a beaker and boiled with distilled water, and the
water decanted some eight or ten times, and the residue finally
transferred to a tarred filter and washed for some time with hot water.
The residue left upon the filter is wood-pulp. This is dried at 100° C.
until constant, and weighed. The solution and washings from the wood are
evaporated down in a platinum dish, and dried at 100° C. It will consist
of the potassium nitrate, and any other mineral salts, such as carbonate
of soda, which should always be tested for by adding a few drops of nitric
acid and a little water to the residue, and again evaporating to dryness
and re-weighing. From the difference in weight the soda can be calculated,
sodium nitrate having been formed. Thus--

Na_{2}CO_{3} + 2HNO_{3} = 2NaNO_{3} + CO_{2} + H_{2}O.

Mol. wt. = 106 = 170

(170 - 106 = 64) and _x_ = (106 x _d_)/64

where _x_ equals grms. of sodium carbonate in residue, and _d_ equals the
difference in weight of residue, before and after treatment with nitric
acid.

The nitro-glycerine is best found by difference, but if desired the
solutions from the precipitation of the nitro-cellulose may be evaporated
down upon the water bath at 30° to 40° C., and finally dried over CaCl_{2}
until no smell of ether or chloroform can be detected, and the nitro-
glycerine weighed. It will, however, always be much too low. An actual
analysis of a sample of gelatine dynamite gave the following result:--

Nitrocellulose (collodion)    3.819 per cent.
Nitro-glycerine              66.691    "
Wood-pulp                    16.290    "
KNO_{3}                      12.890    "
Na_{2}CO_{3}                 _Nil._
Water                         0.340    "

This sample was probably intended to contain 30 per cent. of absorbing
material to 70 per cent. of explosive substances. Many dynamites contain
other substances than the above, such as paraffin, resin, sulphur, wood,
coal-dust, charcoal, also mineral salts, such as carbonate of magnesia,
chlorate of potash, &c. In these cases the above-described methods must of
course be considerably modified. Paraffin, resin, and most of the sulphur
will be found in the ether solution if present. The solution should be
evaporated (and in this case the explosive should in the first case be
treated with ether only, and not ether-alcohol), and the residue weighed,
and then treated on the water bath with a solution of caustic soda. The
resin goes into solution, and is separated by decantation from the
residue, and precipitated by hydrochloric acid, and collected on a tarred
filter (dried at 100° C.), and dried at 100° C. and weighed. The nitro-
glycerine residue is treated with strong alcohol, decanted, and the
residue of paraffin and sulphur washed with alcohol, dried, and weighed.

To separate the paraffin from the sulphur the residue is heated with a
solution of ammonium sulphide. After cooling the paraffin collects as a
crust upon the surface of the liquid, and by pricking a small hole through
it with a glass rod the liquid underneath can be poured off, and the
paraffin then washed with water, dried, and weighed. Sulphur is found by
difference. Mr F.W. Smith (_Jour. Amer. Chem. Soc._, 1901, 23 [8],
585-589) determines the sulphur in dynamite gelatine as follows:--About 2
grms. are warmed in a 100 c.c. silver crucible on the water bath with an
alcoholic solution of sodium hydroxide, and where the nitro-glycerine is
decomposed, the liquid is evaporated to dryness. The residue is fused with
40 grms. of KOH and 5 grms. of potassium nitrate, the mass dissolved in
dilute acetic acid and filtered, and the sulphates precipitated in the
usual way. If camphor is present, it can be extracted with bisulphide of
carbon after the material has been treated with ether-alcohol. In that
case the sulphur, paraffin, and resin will also be dissolved. The camphor
being easily volatile, can be separated by evaporation. Let the weight of
the extract, freed from ether-alcohol before treatment with bisulphide of
carbon, equal A, and the weight of extract after treatment with CS_{2} and
evaporation of the same equal B; and weight of the residue which is left
after evaporation of the CS_{2} and the camphor in solution equal C, the
percentage of camphor will be A - B - C. The residue C may contain traces
of nitro-glycerine, resin, or sulphur.

Camphor may be separated from nitro-glycerine by means of CS_{2}. If the
solution of camphor in nitro-glycerine be shaken with CS_{2}, the camphor
and a little of the nitro-glycerine will dissolve. The bisulphide solution
is decanted, or poured into a separating funnel and separated from the
nitro-glycerine. The two solutions are then heated on the water bath to
20° C. and then to 60° C., and afterwards in a vacuum over CaCl_{2} until
the CS_{2} has evaporated from them. The camphor evaporates, and leaves
the small quantity of nitro-glycerine which had been dissolved with it.
The other portion is the nitro-glycerine, now free from CS_{2}. The two
are weighed and their weights added together, and equals the nitro-
glycerine present. There is a loss of nitro-glycerine, it being partly
evaporated along with the CS_{2}. Captain Hess has shown that it is equal
to about 1.25 per cent. This quantity should therefore be added to that
found by analysis. Morton Liebschutz, in a paper in the _Moniteur
Scientifique_ for January 1893, very rightly observes that the variety of
dynamites manufactured is very great, all of them having a special
composition which, good or bad, is sometimes of so complicated a nature
that the determination of their elements is difficult.

The determination of nitro-glycerine in simple dynamite No. 1 is easy; but
not so when the dynamite contains substances soluble in ether, such as
sulphur, resin, paraffin, and naphthalene. After detailing at length the
methods he employs, he concludes with the observation that the knowledge
of the use of acetic acid--in which nitro-glycerine dissolves--for the
determination of nitro-glycerine may be serviceable. Mr F.W. Smith[A]
gives the following indirect method of determining nitro-glycerine in
gelatine dynamite, &c. About 15 grms. of the sample are extracted with
chloroform in a Soxhlet apparatus, and the loss in weight determined. In a
second portion the moisture is determined. A third portion of about 2
grms. is macerated with ether in a small beaker, the ethereal extract
filtered, and the process of extraction repeated three or four times. The
united filtrates are allowed to evaporate spontaneously, and the residue
warmed gently on the water bath with 5 c.c. of ammonium sulphide solution,
and 10 c.c. of alcohol until the nitro-glycerine is decomposed, after
which about 250 c.c. of water and sufficient hydrochloric acid to render
the liquid strongly acid, are added, and the liquid filtered. The
precipitate is washed free from acid, and then washed through the filter
with strong alcohol and chloroform into a weighed platinum dish, which is
dried to constant weight at 50° C. The contents of the dish are now
transferred to a silver crucible, and the sulphur determined. This amount
of sulphur, deducted from the weight of the contents of the platinum dish,
gives the quantity of substances soluble in chloroform with the exception
of the nitro-glycerine, moisture, and sulphur. The amount of the former
substances _plus_ the moisture and sulphur, deducted from the total loss
on extraction with chloroform, gives the quantity of nitro-glycerine.
Nitro-benzene may be detected, according to J. Marpurgo, in the following
manner:--In a porcelain basin are placed two drops of liquid phenol, three
drops of water, and a fragment of potash as large as a pea. The mixture is
boiled, and the aqueous solution to be tested then added. On prolonged
boiling nitro-benzene produces at the edge of the liquid a crimson ring,
which on the addition of a solution of bleaching powder turns emerald-
green. And nitro-glycerine in ether solution, by placing a few drops of
the suspected solution, together with a drop or two of aniline, upon a
watch-glass, evaporating off the ether, and then adding a drop of
concentrated sulphuric acid to the residue, when, if nitro-glycerine is
present, the H_{2}SO_{4} will strike a crimson colour, due to the action
of the aniline sulphate upon the nitric acid liberated from the nitro-
glycerine.

[Footnote A: "Notes on the Analysis of Explosives," _Jour. Amer. Chem.
Soc._, 1901, 23 [8], 585-589.]

~Tonite.~--The analysis of this explosive is a comparatively easy matter,
and can be performed as follows:--Weigh out 10 grms., or a smaller
quantity, and boil with water in a beaker, decanting the liquid four or
five times, and filter. The aqueous solution will contain the nitrate of
barium. Then put the residue on the filter, and wash two or three times
with boiling water. Evaporate the filtrate to dryness in a platinum dish.
Dry and weigh. This equals the Ba(NO_{3})_{2}. If the sample is tonite No.
3, and contains di-nitro-benzol, treat first with ether to dissolve out
this substance. Filter into a dish, and evaporate off the ether, and weigh
the di-nitro-benzol, and afterwards treat residue with water as before.
The residue is dried and weighed, and equals the gun-cotton present. It
should then be treated with a solution of ether-alcohol in a conical
flask, allowed to stand some three hours, then filtered through a weighed
filter paper, dried at 40° C., and weighed. This will give the gun-cotton,
and the difference between this last weight and the previous one will give
the collodion-cotton. A portion of the residue containing both the gun-
cotton and the soluble cotton can be tested in the nitrometer, and the
nitrogen determined.

~Cordite.~--This explosive consists of gun-cotton (with a little
collodion-cotton in it as impurity), nitro-glycerine, and vaseline--the
proportions being given as 30 per cent. nitro-glycerine, 65 per cent. gun-
cotton, and 5 per cent. vaseline. Its analysis is performed by a
modification of the method given for gelatines. Five grms. may be
dissolved in ether-alcohol in a conical flask, allowed to stand all night,
and then filtered through a linen filter. The residue is washed with a
little ether, pressed, and dried at 40° C., and weighed. It equals the
gun-cotton. The solution contains the nitro-glycerine, soluble cotton, and
vaseline. The cotton is precipitated with chloroform, filtered off, dried,
and weighed. The two ether-alcohol solutions are mixed, and carefully
evaporated down in a platinum dish upon the water bath at a low
temperature. The residue is afterwards treated with strong 80 per cent.
acetic acid, which dissolves out any nitro-glycerine left in it. The
nitro-glycerine is then obtained by difference, or the method suggested to
me privately by Mr W.J. Williams may be used. The residue obtained by
evaporation of the ether-alcohol solution, after weighing, is treated with
alcoholic potash to decompose the nitro-glycerine, water is added and the
alcohol evaporated off. Some ether is then added, and the mixture shaken,
and the ether separated and evaporated, and the residue weighed as
vaseline.

The moisture should, however, be determined by the method devised by Mr
Arthur Marshall, F.I.C., of the Royal Gunpowder Works, Waltham Abbey,
which is carried out as follows:--The cordite or other explosive is
prepared in the manner laid down for the Abel heat test, that is t say, it
is ground in a small mill, and that portion is selected which passes
through a sieve having holes of the size of No. 8 wire gauge, but not
through one with holes No. 14 wire gauge.

[Illustration: FIG. 40.--MARSHALL'S APPARATUS FOR MOISTURE IN CORDITE.]

The form of apparatus used is shown in Fig. 40. It consists of an
aluminium dish A, having the dimensions shown, and the glass cone B
weighing not more than 30 grms. Five grms. of the cordite are weighed into
the aluminium dish A. This is covered with the cone B, and the whole is
accurately weighed, and is then placed upon a metal plate heated by steam
from a water bath. It is left upon the bath until all the moisture has
been driven off, then it is allowed to cool for about half-an-hour in a
desiccator and is weighed. The loss in weight gives accurately the
moisture of the sample. For cordite of the original composition, one
hour's heating is sufficient to entirely drive off the moisture; for
modified cordite containing 65 per cent. of gun-cotton, two hours is
enough, provided that there be not more than 1.3 per cent. of moisture
present.

If the proportion of nitro-glycerine be higher, a longer heating is
necessary. The aluminium dish must not be shallower than shown in the
figure, for if the distance between the substance and the edge of the
glass cone be less than half an inch, some nitro-glycerine will be lost.
Again, the sample must not be ground finer than stated, else some of the
moisture will be lost in the grinding and sieving operations, and the
result will be too low. In order to be able to drive off all the moisture
in the times mentioned, it is essential that the glass cone shall not fit
too closely on the aluminium dish, consequently the horizontal ledge round
the top of the dish should be bent, so as to render it slightly untrue,
and leave a clearance of about 0.02 inch in some places. If these few
simple precautions be taken, the method will be found to be very accurate.
Duplicate determinations do not differ more than 0.01 per cent.[A]

[Footnote A: "Determination of Moisture in Nitro-glycerine Explosives," by
A. Marshall, _Jour. Soc. Chem. Ind._, Feb. 29, 1904, p. 154.]

~The Vaseline~ (C_{16}H_{34}), or petroleum jelly, used has a flash-point
of 400° F. It must not contain more than 0.2 per cent. volatile matter
when heated for 12 hours on the water bath, and should have a specific
gravity of 0.87 at 100° F., and a melting point of 86° F. It is obtained
during the distillation of petroleum, and consists mainly of the portions
distilling above 200° C. It boils at about 278° C.

~Acetone~ (CH_{3}CO.CH_{3}), or dimethyl ketone, is formed when iso-propyl
alcohol is oxidised with potassium bichromate and sulphuric. It is also
produced in considerable quantities during the dry distillation of wood,
and many other organic compounds. Crude wood spirit, which has been freed
from acetic acid, consists in the main of a mixture of acetone and methyl-
alcohol. The two substances may be roughly separated by the addition of
calcium chloride, which combines with the methyl-alcohol. On subsequent
distillation crude acetone passes over, and may be purified by conversion
into the bisulphite compound.

Acetone is usually prepared, however, by the dry distillation of crude
calcium or barium acetate.

(CH_{3}.COO)_{2}Ca = CH_{3}.CO.CH_{3} + CaCO_{3}.

The distillate is fractionated, and the portion, boiling between 50° and
60° C., mixed with strong solution of sodium bisulphite. The crystalline
cake of acetone sodium bisulphite, which separates on standing, is well
pressed, to free it from impurities, decomposed by distillation with
dilute sodium carbonate, and the aqueous distillate of pure acetone
dehydrated over calcium chloride. Acetone is a colourless, mobile liquid
of sp. gr. .792 at 20° C., it boils at 56.5° C., has a peculiar, pleasant,
ethereal odour, and is mixible with water, alcohol, and ether in all
proportions.

The acetone used in the manufacture of cordite should conform to the
following specification:--

SPECIFICATION FOR ACETONE.

1. The acetone to be not more than 0.802 specific gravity at 60° F. When
mixed with distilled water it must show no turbidity, and must leave no
residue on evaporation at 212° F. On distillation, four-fifths by volume
of the quantity taken must distil over at a temperature not exceeding 138°
F. The residual matter left after this distillation must not contain,
besides acetone, any ingredient that is not a bye-product incidental to
the manufacture of acetone.

2. One c.c. of 0.10 per cent. solution in distilled water of pure
permanganate of potash, added to 100 c.c. of the acetone, must retain its
distinctive colour for not less than 30 minutes. This test should be made
at a temperature of 60° F.

3. The acetone tested by the following method must not show more than
0.005 per cent. of acid, calculated to acetic acid:--

To 50 c.c. of the sample diluted with 50 c.c. of distilled water, with 2
c.c. of phenol-phthalein solution (1 gramme to 1,000 c.c. of 50 per cent.
alcohol) added as an indicator, add from a burette N/100 sodium hydrate
solution (1 c.c. 0.0006 gramme acetic acid), and calculate to acetic acid
in the usual manner.

The water used for the dilution of the acetone must be carefully tested
for acidity, and the pipettes used for measuring should not be blown out,
as it would be possible thus to neutralise nearly 2 c.c. of the soda
solution.

The presence of water in a sample of acetone may be detected by Schweitzer
and Lungwitz's method (_Chem. Zeit._, 1895, xix., p. 1384), which consists
in shaking together equal volumes of acetone and petroleum ether (boiling
point, 40° to 60° C.), when if present a separation of the liquid in
layers will take place.

~Estimation of Acetone.~--Kebler (_Jour. Amer. Chem. Soc._, 1897, 19, 316-
320) has improved Squibb's modification of Robineau and Rollins' method.
The following solutions are required:--

(1.) A 6 per cent. solution of hydrochloric acid.

(2.) A decinormal solution of sodium thiosulphate.

(3.) Alkaline potassium iodide solution prepared by dissolving 250 grms.
of potassium iodide in water, made up to a litre; dissolving 257 grms. of
sodium hydroxide (by alcohol) in water, likewise made up to a litre. After
allowing the latter to stand, 800 c.c. of the clear solution are added to
the litre of KI.

(4.) Sodium hypochlorite solution: 100 grms. of bleaching powder (35 per
cent.) are mixed with 400 c.c. of water: to this is added a hot solution
of 120 grms. of crystallised sodium carbonate in 400 c.c. of water. After
cooling, the clear liquid is decanted, the remainder filtered, and the
filtrate made up to a litre; to each litre is added 25 c.c. of sodium
hydroxide solution (sp. gr. 1.29).

(5.) An aqueous solution of the acetone, containing 1 or 2 per cent. of
acetone.

(6.) Bicarbonated starch solution prepared by treating 0.125 grm. of
starch with 5 c.c. of cold water, then adding 20 c.c. of boiling water,
boiling a few minutes, cooling, and adding 2 grms. of sodium bicarbonate.

To 20 c.c. of the potassium iodide solution are added 10 c.c. of the
diluted aqueous acetone, an excess of the sodium hypochlorite solution is
then run in from a burette and well shaken for a minute. The mixture is
then acidified with the hydrochloric acid solution, and while agitated, an
excess of sodium thiosulphate solution is added, the mixture being
afterwards allowed to stand a few minutes. The starch indicator is then
added, and the excess of thiosulphate re-titrated. The relation of the
sodium hypochlorite solution to the sodium thiosulphate being known, the
percentage of acetone can be readily calculated.[A]

[Footnote A: See "The Testing of Acetone," Conroy, _Jour. Soc. Chem.
Ind._, 31st March 1900, vol. xix.]

Dr S.J.M. Auld has recently (_Jour. Chem. Soc._, Feb. 15, 1906, vol. xxv.)
worked out a volumetric method for the estimation of acetone, depending on
the formation of bromoform, and its subsequent hydrolysis with alcoholic
potash. The hydrolysis is probably expressed thus--

3CHBr_{3} + 9KOH + C_{2}H_{5}OH = 3CO + C_{2}H_{4} + 9KBr + 7H_{2}O

as it has been shown by Hermann and Long that exactly 3 volumes of carbon
monoxide to 1 of ethylene are evolved. The residual potassium bromide is
estimated by means of standard silver nitrate solution. Bromoform is
specially suitable for this purpose for several reasons. It is very
readily formed by the action of bromine and potash on acetone, and
although very volatile in steam, it is not liable to loss due to its own
evaporation. Further, its high molecular weight and large percentage of
bromine conduce to accurate results, 58 grms. of acetone being responsible
for the formation of 357 grms. of KBr. The method of carrying out the
analysis is as follows:--

A known quantity of the solution to be tested, containing acetone to the
extent of 0.1 to 0.2 grm., is pipetted into a 500 c.c. round-bottom flask,
diluted with a little water, and mixed with 20 to 30 c.c. of a 10 per
cent. solution of caustic potash. The flask is connected with a long
reflex condenser, and is also fitted with a dropping funnel containing a
solution of bromine in potassium bromide (200 grms. of Br and 250 grms. of
KBr to 1 litre of water). The bromine solution is allowed to flow into the
mixture until it has acquired a faint yellow tinge, the flask and its
contents being then heated on the water bath at about 70° C. for half-an-
hour. Bromine solution is added drop by drop until the slight coloration
is permanent, excess of bromine being got rid of by boiling for a minute
or two with a little more caustic potash. The mixture is then distilled
until the distillate is free from bromoform, halogen being tested for in
the usual manner. Water is added to the contents of the flask if
necessary. It may be here observed that no acetone can be detected in the
distillate by means of the mercuric oxide test, and free bromine is also
absent. The condenser having been washed out with a little alcohol, in
order to remove any traces of bromoform which may have collected, the
distillate and washings are mixed with 50 c.c. of alcohol and sufficient
solid caustic potash to make an approximately 10 per cent. solution. The
mixture is then heated on the water bath under a reflux condenser until
the bromoform is completely decomposed. This generally occupies about
three-quarters of an hour. The liquid is allowed to cool, evaporated to
smaller bulk if necessary, and exactly neutralised with dilute nitric
acid. It is then diluted with water to 500 c.c., and an aliquot part
titrated with N/10 silver nitrate solution, using potassium chromate as
indicator; 240 parts of bromine correspond to 58 parts of acetone. The
complete analysis can be performed in one and a half to two hours. It is
imperative that the bromine used should be pure, as crude bromine
frequently contains bromoform. The method is suitable for the estimation
of acetone in wood-spirit, the spirit being diluted to 10 times its
volume, and 5 c.c. of this solution employed for the determination. For
example--

(1.) Three c.c. of a solution containing 9.61 per cent. acetone gave
1.7850 grm. KBr. Acetone found = 9.66 per cent.

(2.) Ten c.c. of a solution containing 0.96 per cent. acetone gave 0.5847
grm. KBr. Acetone found = 0.95 per cent.

~Nitro-Cotton.~--The first thing upon opening a case of wet cotton, or in
receiving a sample from the "poacher," that requires to be determined is
the percentage of water that it contains. It is best done by weighing out
about 1,000 grms. upon a paper tray, which has been previously dried in
the oven at 100° C. for some time, and become constant in weight. The
trayful of cotton is then placed in a water oven, kept at 100° C., and
dried as long as it loses water. The loss gives the percentage of water.
It varies from 20 to 30 per cent. as a rule in "wet" cotton.

OUTLINE SCHEME FOR THE ANALYSIS OF NITRO-EXPLOSIVES
 _______________________________________________________________________
|                                                                       |
| Exhaust dried substance with Anhydrous Ether in Soxhlet's Fat         |
| Extraction Apparatus.                                                 |
|_______________________________________________________________________|
|                                                                       |
| _Solution_--Divide into two parts ~A.~ and ~B.~                       |
|_______________________________________________________________________|
|                                                                       |
| ~A.~                                                                  |
|                                                                       |
| Allow ether to evaporate spontaneously. Dry residue in vacuo over     |
| H_{2}SO_{4} and weigh. Equals nitro-glycerine, resin, camphor, and    |
| paraffin.                                                             |
|                                                                       |
| The nitro-glycerine in this residue may be decomposed by heating      |
| with a solution of alcoholic potash. Water may then be added, and the |
| alcohol evaporated off on the water bath. From  this solution the     |
| resin may be  precipitated by HCl, filtered off, dried, and weighed.  |
| Solution  containing the paraffin is treated with AmS solution and    |
| heated.  On cooling the paraffin separates, and may be separated.     |
| Residue  may be shaken with CS_{2} to remove  camphor.                |
|_______________________________________________________________________|
|                                                                       |
| ~B.~                                                                  |
|                                                                       |
| Add phenol-phthalein and titrate with alcoholic potash, 1 c.c. normal |
| KHO = .330 grm. _resin_, and add considerably more KHO. Evaporate,    |
| dissolve residue in water, shake with ether, and separate.            |
|_______________________________________________________________________|
|                                                                       |
| _Ethereal Solution_ evaporated leaves paraffin.                       |
|_______________________________________________________________________|
|                                                                       |
| _Aqueous Solution_--                                                  |
| Add bromide, acidify with HCl, separate any resin and precipitate,    |
| filtrate with BaCl_{2} BaSO_{4} x .1373 = Sulphur.                    |
|_______________________________________________________________________|
|                                                                       |
| _Residue_--                                                           |
| Dry, weigh, and exhaust with water preferably in Soxhlet.             |
|_______________________________________________________________________|
|                      |                                                |
| _Solution_--         | _Residue_--                                    |
| Contains metallic    | Dry, weigh, and agitate an aliquot part with   |
| nitrates, chlorates, | with H_{2}SO_{4} and Hg in nitrometer. If      |
| soluble carbonates,  | nitro-cellulose is present, treat remainder of |
| the sum of which     | residue with ether-alcohol.                    |
| (except AmCO_{3})    |________________________________________________|
| can be determined by |                                                |
| evaporating down at  | _Solution_--                                   |
| 100° C. to dryness   | Evaporate and weigh. Residue consists of       |
| and weighing.        | soluble nitro-cellulose.                       |
| Nitrates can be      |________________________________________________|
| determined by        |                                                |
|                      | _Residue_--                                    |
|                      | Dry and weigh and determine hexa-nitro-        |
|                      | cellulose in nitrometer, if present. Exhaust   |
|                      | remainder with acetic ether.                   |
|                      |________________________________________________|
|                      |                      |                         |
|                      | _Solution_--         | _Residue_--             |
|                      | Hexa-nitro-cellulose | Dry and weigh, ignite   |
|                      | (Gun cotton).        | and reweigh. Loss =     |
|                      |                      | _Cellulose_.            |
|                      |                      |_________________________|
|                      |                      |                         |
|                      |                      | Residue consists of     |
|                      |                      | sawdust, charcoal,      |
|                      |                      | coal, chalk, guhr,      |
|                      |                      | or mineral matter, &c.  |
|______________________|______________________|_________________________|

NOTE.--Camphor is found by difference. Sulphur is only partially soluble
in ether. It is better, therefore, to extract some of the original
substance with water, and treat residue with alcoholic KHO. Add bromide,
acidify, and precipitate as BaSO.

~The Solubility Test.~--The object of this test is to ascertain, in the
case of gun-cotton, the percentage of soluble (penta and lower nitrates)
cotton that it contains, or in the case of soluble cotton, the quantity of
gun-cotton. The method of procedure is as follows:--Five grms. of the
sample which has been previously dried at 100° C., and afterwards exposed
to the air for two hours, is transferred to a conical flask, and 250 c.c.
ether-alcohol added (2 ether to 1 alcohol). The flask is then corked and
allowed to digest, with repeated shaking, for two or three hours. The
whole is then transferred to a linen filter, and when the solution has
passed through the filter, is washed with a little ether, and pressed in a
hand-screw press between folds of filter paper. The sample is then
returned to the flask, and the previous treatment repeated, but it will be
sufficient for it to digest for one hour the second time. The filter is
then again pressed first gently by hand, then in the press, and afterwards
opened up and the ether allowed to evaporate. The gun-cotton is then
removed from the filter and transferred to a watch-glass, and dried in the
water oven at 100° C. When dry it is exposed to the air for two hours and
weighed. It equals the amount of gun-cotton and unconverted cotton in the
5 grms. The unconverted cotton must be determined in a separate 5 grms.
and deducted.

The method of determining the soluble cotton now used in the Government
laboratories is as follows:--Fifty grains of the nitro-cotton are
dissolved in 150 c.c. of ether-alcohol, and allowed to stand, with
frequent shakings, in a 200 c.c. stoppered measure for six hours; 75 c.c.
of the clear solution are then drawn off by the aid of a pipette and
evaporated in a dish on the water bath, and finally in the water oven at
120° F. (49° C.), until constant in weight. The weight found equals the
quantity of soluble cotton in the 75 c.c., which, multiplied by 4, equals
the percentage, thus: Suppose that 2.30 grains was the weight found, then

(2.3 x 150)/75 = 4.6 in 50 = 9.20 per cent.

A method for the determination of soluble nitro-cellulose in gun-cotton
and smokeless powder has been published by K.B. Quinan (_Jour. Amer. Chem.
Soc._, 23 [4], 258). In this method about 1 grm. of the finely divided dry
sample to be analysed is placed in an aluminium cup 1.9 inch in diameter
and 4-1/8 inch deep. It is then covered and well stirred with 50 c.c. of
alcohol, 100 c.c. of ether are then added, and the mixture is stirred for
several minutes. After removing the stirrer, the cup is lightly covered
with an aluminium lid, and is then placed in the steel cup of a
centrifugal machine, which is gradually got up to a speed of 2,000
revolutions per minute, the total centrifugal force at the position
occupied by the cups (which become horizontal when in rapid rotation) is
about 450 lbs. They are rotated at the full speed for ten to twelve
minutes, and the machine is then gradually stopped. By this time the whole
of the insoluble matter will be at the bottom of the cup, and the
supernatant solution will be clear. It is drawn off to within a quarter of
an inch of the bottom (without disturbing the sediment), with the aid of a
pipette.

Care must be taken that the solution thus withdrawn is perfectly clear.
About 10 to 15 c.c. of colloid solution and a film of insoluble matter
remain at the bottom of the cup; these are stirred up well, the stirrer is
rinsed with ether-alcohol, about 50 c.c. of fresh ether-alcohol are added;
the mixture is again treated in the centrifugal apparatus for about eight
minutes; the whole washing process is then repeated until all soluble
matter has been removed. This may require about seven or eight (or for
samples with much insoluble matter ten or twelve or more) washings, but as
the extraction proceeds, the period of rotation may be somewhat reduced.
After extraction is completed, the insoluble matter is transferred to a
Gooch crucible with the usual asbestos pad, dried at 100° C., and weighed.
The residue may, if wished, be dried and weighed in the aluminium cup, but
then it cannot be ignited. The whole time for an analysis exclusive of
that required for drying, is from one to two hours--average time, 1-1/4
hour. The results are satisfactory both as to accuracy and rapidity.
Acetone-soluble nitro-cellulose may be determined by the same method.

~The Unconverted or Non-nitrated Cotton.~--However well the cotton has
been nitrated, it is almost certain to contain a small quantity of non-
nitrated or unconverted cotton. This can be determined thus:--Five grms.
of the sample are boiled with a saturated solution of sodium sulphide, and
then allowed to stand for forty-eight hours, and afterwards filtered or
decanted, and again boiled with fresh solutions of sulphide, and again
filtered, washed first with dilute HCl and then with water, dried, and
weighed. The residue is the cellulose that was not nitrated, plus ash, &c.
It should be ignited, and the weight of the ash deducted from the previous
weight.

Acetone, and acetic-ether (ethyl-acetate) may also be used as solvents for
the nitro-cellulose. Another process is to boil the gun-cotton, &c., in a
solution of sodium stannate made by adding caustic soda to a solution of
stannous chloride, until the precipitate first formed is just
re-dissolved. This solution dissolves the cellulose nitrates, but does not
affect the cellulose. Dr Lungé found the following process more
satisfactory in the case of the more highly nitrated products:--The
reagent is an alcoholic solution of sodium-ethylate prepared by dissolving
2 to 3 grms. of sodium in 100 c.c. of 95 per cent. alcohol, and mixing the
filtered solution with 100 c.c. of acetone. It has no effect upon
cellulose, but decomposes nitro-cellulose with the formation of a reddish
brown compound, which is soluble in water. In the determination, 5 grms.
of gun-cotton are heated to 40° or 50° C. on the water bath with 150 c.c.
of the reagent, the liquid being shaken at intervals for twenty to thirty
minutes; or the mixture may be allowed to stand for a few hours at the
ordinary temperature. The brown-red solution is decanted from the
undissolved residue, and the latter washed with alcohol and with water, by
decantation, and then on the filter with hot water, to which a little
hydrochloric acid is added for the final washings. For ordinary work this
cellulose is dried immediately and weighed, but in exact determinations it
is washed with alcohol, again treated with 50 c.c. of the reagent, and
separated and washed as before. The cellulose thus obtained, gives no
trace of gas in the nitrometer, and duplicate determinations agree within
0.1 to 0.2 per cent. when the weight of unchanged cellulose amounts to
about 0.2 grm. Gun-cotton, which is completely soluble in acetone,
contains only traces of cellulose, and when as much as 0.85 per cent. is
present it does not dissolve entirely. This method is not applicable to
the determination of cellulose in lower nitrated products, and Dr Lungé
attributes this to the fact that these being prepared with less
concentrated acid invariably contain oxy-cellulose.

~Alkalinity.~--Five grms. of the air-dried and very finely divided sample
are taken from the centre of the slabs or discs, and digested with about
20 c.c. of N/2 hydrochloric acid, and diluted with water to about 250
c.c., and shaken for about fifteen minutes. The liquid is then decanted,
and washed with water until the washings no longer give an acid reaction.
The solution, together with the washings, are titrated with N/4 sodium
carbonate, using litmus as indicator.

~Ash and Inorganic Matter.~--This is best determined by mixing 2 or 3
grms. of the nitro-cotton in a platinum crucible with shavings of
paraffin, heating sufficiently to melt the paraffin, and then allowing the
contents of the crucible to catch fire and burn away quietly. The
temperature is then raised, and the carbonaceous residue incinerated,
cooled, weighed, &c., and the percentage of ash calculated. Schjerning
proceeds in the following way:--He takes 5 grms. of the nitro-cotton in a
large platinum crucible, he then moistens it with a mixture of alcohol and
ether, in which paraffin has been dissolved to saturation, and filtered
and mixed with one-fourth of its volume of water. Some fragments of solid
paraffin are then added, and the ether set on fire. Whilst this is in
progress the crucible is kept in an oblique position, and is rotated so
that the gun-cotton may absorb the paraffin uniformly. The partially
charred residue is now rubbed down with a rounded glass rod, and the
crucible is covered and heated for from fifteen to twenty minutes over the
blow-pipe, the lid being occasionally removed. The residue is soon
converted into ash, which is weighed, and then washed out into a porcelain
basin and treated with hydrochloric acid heated to 90° C. The oxide of
iron, alumina, lime, and magnesia are thus dissolved, and the silica
remains as insoluble residue. The rest of the analysis is conducted
according to the well-known methods of separation. The percentage of ash
as a whole is generally all that is required.

~Examination of Nitrated Celluloses with Polarised Light.~--Dr G. Lungé
(_Jour. Amer. Chem. Soc._, 1901, 23 [8], 527) has formed the following
conclusions:--The most highly nitrated products appear blue in polarised
light, but those containing between 13.9 and 13.0 per cent. of nitrogen
cannot be distinguished from each other by polarisation. As the percentage
of nitrogen rises, the blue colour becomes less intense, and here and
there grey fibres can be observed, though not in proportion to the
increase in the nitrogen. Below 12.4 per cent. of nitrogen, the fibres
show a grey lustre, which usually appears yellow when the top light is cut
off. Below 10 per cent. of nitrogen, the structure is invariably partially
destroyed and no certain observations possible. It is only possible to
distinguish with certainty, firstly any unchanged cellulose by its
flashing up in variegated (rainbow) colours; and secondly, highly nitrated
products (from 12.75 per cent. N upwards), by their flashing up less
strongly in blue colours. The purple transition stage in the fibres
containing over 11.28 per cent. of N (Chardonnet) was not observed by Dr
Lungé.

~Determination of Nitrogen by Lungé Nitrometer.~--The determination of the
percentage of nitrogen in a sample of gun-cotton or collodion is perhaps
of more value, and affords a better idea of its purity and composition,
than any of the foregoing methods of examination, and taken in conjunction
with the solubility test, it will generally give the analyst a very fair
idea of the composition of his sample. If we regard gun-cotton as the
hexa-nitro-cellulose, the theoretical amount of nitrogen required for the
formula is 14.14 per cent., and in the same way for collodion-cotton,
which consists of the lower nitrates, chiefly, however, of the penta-
nitrate, the theoretical nitrogen is 12.75 per cent., so that if in a
sample of nitro-cotton the nitrogen falls much lower than 14 per cent., it
probably contains considerable quantities of the lower nitrates, and
perhaps some non-nitrated cellulose as well (C_{6}H_{10}O_{5})_{x}, which
of course would also lower the percentage of nitrogen.

The most expeditious method of determining the nitrogen in these nitro
bodies is by the use of Lungé's nitrometer (Fig. 41), and the best way of
working the process is as follows:--Weigh out with the greatest care 0.6
grm. of the previously dried substance in a small weighing bottle of about
15 c.c. capacity, and carefully add 10 c.c. of concentrated sulphuric acid
from a pipette, and allow to stand until all the cotton is dissolved. The
nitrometer should be of a capacity 150 to 200 c.c., and should contain a
bulb of 100 c.c. capacity at the top, and should be fitted with a Greiner
and Friederich's three-way tap. When the nitro-cotton has entirely
dissolved to a clear solution, raise the pressure tube of the nitrometer
so as to bring the mercury in the measuring tube close up to the tap. Open
the tap in order to allow of the escape of any air bubbles, and clean the
surface of the mercury and the inside of the cup with a small piece of
filter paper. Now close the tap, and pour the solution of the nitro-cotton
into the cup. Rinse out the bottle with 15 c.c. of sulphuric acid,
contained in a pipette, pouring a little of the acid over the stopper of
the weighing bottle in case some of the solution may be on it. Now lower
the pressure tube a little, just enough to cause the solution to flow into
the bulb of the measuring tube, when the tap is slightly opened. When the
solution has run in almost to the end, turn off the tap, wash down the
sides of the bottle, and add to the cup of the nitrometer; allow it to
flow in as before, and then wash down the sides of the cup with 10 c.c. of
sulphuric acid, adding little by little, and allowing each portion added
to flow into the bulb of the nitrometer before adding the next portion.
Great care is necessary to prevent air bubbles obtaining admission, and if
the pressure tube is lowered too far, the acid will run with a rush and
carry air along with it.

[Illustration: FIG. 41.--ORDINARY FORM OF LUNGÉ NITROMETER.]

The solution being all in the measuring tube, the pressure tube is again
slightly raised, and the tube containing the nitro-cotton solution shaken
for ten minutes with considerable violence. It is then replaced in the
clamp, and the pressure relieved by lowering the pressure tube, and the
whole apparatus allowed to stand for twenty minutes, in order to allow the
gas evolved to assume the temperature of the room. A thermometer should be
hung up close to the bulb of the measuring tube. At the end of the twenty
minutes, the levels of the mercury in the pressure and measuring tubes are
equalised, and the final adjustment obtained by slightly opening the tap
on the measuring tube (very slightly), after first adding a little
sulphuric acid to the cup, and observing whether the acid runs in or moves
up. This must be done with very great care. When accurately adjusted, it
should move neither way. Now read off the volume of the NO gas in cubic
centimetres from the measuring tube. Read also the thermometer suspended
near the bulb, and take the height of the barometer in millimetres. The
calculation is very simple.

EXAMPLE--COLLODION-COTTON.

0.6[A] grm. taken. Reading on measuring tube = 114.6 c.c. NO. Barometer--
758 mm. Temperature--15° C.

[Footnote A: 0.5 grm. is enough in the case of gun-cotton.]

Since 1 c.c. NO = 0.6272 milligramme N, and correcting for temperature and
pressure by the formula

760 x (1 + _d_^{2}) (_d_ = .003665), for temperature 15° = 801.78,[A]

then

(114.6 x 100 x 750 x .6272)/(801.7 x. 6) = 11.22 per cent. nitrogen.

[Footnote A: See Table, page 244.]

The nitrogen in nitro-glycerine may of course be determined by the
nitrometer, but in this case it is better to take a much smaller quantity
of the substance. From 0.1 to 0.2 grm. is quite sufficient. This will give
from 30 to 60 c.c. of gas, and therefore a measuring tube without a 100
c.c. bulb must be used.

EXAMPLE.

0.1048 grm. nitroglycerine taken gave 32.5 c.c. NO. Barometer, 761 mm.
Temperature, 15° C.

Therefore,

(3.25 x 100 x 761 x .6272)/(801.78 x.1048) = 18.46 per cent. N. Theory =
18.50 per cent.

Professor Lungé has devised another form of nitrometer (Fig. 42), very
useful in the nitrogen determination in explosives. It consists of a
measuring tube, which is widened out in the middle to a bulb, and is
graduated above and below into 1/10 c.c. The capacity of the whole
apparatus is 130 c.c.; that of each portion of the tube being 30 c.c., and
of the bulb 70 c.c. The upper portion of the graduated tube serves to
measure small volumes of gas, whilst larger volumes are read off on the
lower part.

[Illustration: FIG. 42. FIG. 43. SOME NEW FORMS OF NITROMETER.]

F.M. Horn (_Zeitschrift für angewandte Chemie_, 1892, p. 358) has devised
a form of nitrometer (Fig. 43) which he has found especially useful in the
examination of smokeless powders. The tap H is provided with a wide bore
through which a weighed quantity of the powder is dropped bodily into the
bulb K. From 4 to 5 c.c. of sulphuric acid which has been heated to 30° C.
are then added through the funnel T, the tap H being immediately closed.
When the powder has dissolved--a process which may be hastened by warming
the bulb very carefully--the thick solution is drawn into the nitrometer
tube N, and the bulb rinsed several times with fresh acid, after which
operation the analysis is proceeded with in the usual way.

Dr Lungé's method of using a separate nitrometer in which to measure the
NO gas evolved to the one in which the reaction has taken place, the gas
being transferred from the one to the other by joining them by means of
indiarubber tubing, and then driving the gas over by raising the pressure
tube of the one containing the gas, the taps being open, I have found to
be a great improvement.

1 c.c. NO gas at 0° and 760 mm.
Equals 0.6272 milligrammes (N) nitrogen.
  "    1.343       "        nitric oxide.
  "    2.820       "       (HNO_{3}) nitric acid.
  "    3.805       "       (NaNO_{3}) sodium nitrate.
  "    4.523       "       (KNO_{3}) potassium nitrate.

~Champion and Pellet's Method.~--This method is now very little used. It
is based upon the fact that when nitro-cellulose is boiled with ferrous
chloride and hydrochloric acid, all the nitrogen is disengaged as nitric
oxide (NO). It is performed as follows:--A vacuum is made in a flask,
fitted with a funnel tube, with a glass stopper on the tube; a delivery
tube that can also be closed, and which dips under a solution of caustic
soda contained in a trough, and the end placed under a graduated tube,
also full of caustic soda. From 0.12 to 0.16 grm. cotton dissolved in 5 to
6 c.c. of sulphuric acid is allowed to flow into the flask, which contains
the ferrous chloride and hydrochloric acid, and in which a vacuum has been
formed by boiling, and then closing the taps. The solution is then heated,
the taps on the delivery tube opened, and the end placed under the
collecting tube, and the NO evolved collected. The NO gas is not evolved
until the solution has become somewhat concentrated. Eder substituted a
solution of ferrous sulphate in HCl for ferrous chloride. Care must be
taken that the flask used is strong enough to stand the pressure, or it
will burst.

The same chemists (_Compt. Rendus_, lxxxiii. 707) also devised the
following method for determining the NO_{2} in nitro-glycerine:--A known
quantity of a solution of ferrous sulphate of previously ascertained
reducing power is placed in a flask, acidified with hydrochloric acid, and
its surface covered with a layer of petroleum oil. About .5 grm. of the
nitro-glycerine is then introduced, and the flask heated on the water
bath. When the sample is completely decomposed, the liquid is heated to
boiling to remove nitric oxide, and the excess of ferrous sulphate
ascertained by titration with standard permanganate; 56 of iron (Fe)
oxidised by the sample correspond to 23 of NO_{2} in the sample of
nitro-glycerine.

~The Schultze-Tieman Method~ for determining nitrogen in nitro-explosives,
especially nitro-cellulose and nitro-glycerine.--The figure (No. 44) shows
the general arrangement of the apparatus. I am indebted for the following
description of the method of working it to my friend, Mr William Bate, of
Hayle. To fill the apparatus with the soda solution, the gas burette is
put on the indiarubber stopper of basin W, and firmly clamped down. Then
the taps A and C are opened, and B closed. When the burette is filled with
soda solution half-way up the funnel Y, A and C are closed, and B opened.
The arrows show the inlet and outlet for the cooling water that is kept
running through the water jacket round the nitrometer tube. To collect the
gas, raise the nitrometer off the rubber stopper, and place the gas tube
from the decomposition apparatus in the glass dish W and under the opening
of the nitrometer.

[Illustration: Fig. 44. SCHULTZE-TIEMAN APPARATUS.]

For the estimation of nitrogen in nitro-cellulose take .5 to .65 grm., and
place in the decomposition flask _f_ (Fig. 45), washing in with about 25
c.c. of water by alternately opening clips D and E. The air in the flask
is driven out by boiling, whilst the air is shut off by the tube _i_
dipping into the basin W, which is filled with the soda lye, and tube K is
placed in the test tube R, which contains a few c.c. of water. As soon as
all the air is completely driven out, clips D and E are closed, and the
gas jet is taken away. (This flask must be a strong one, or it will
burst.) Into test tube R, 25 c.c. of concentrated solution of
protochloride of iron and 10 to 15 c.c. concentrated hydrochloric acid are
poured, which are sucked up into the developing flask _f_ by opening clip
E, air being carefully kept from entering. The clip E is now closed, and
tube _i_ is put underneath the burette, and the development of NO gas is
commenced by heating the contents of the flask _f_. When the pressure of
the gas in the flask has become greater than the pressure of the
atmosphere, the connecting tube begins to swell at _i_, whereupon clip D
is opened, and the boiling continued with frequent shaking of the bulb,
until no more nitrous gas bubbles rise up into the soda lye, the
distilling over of the HCl causes a crackling noise, the clip D is closed,
and E opened. The burette is again put hermetically on the indiarubber
stopper in basin W, and the apparatus is left to cool until the water
discharged through P shows the same temperature as the water flowing
through (into the cooling jacket) Z. If the level of the soda solution in
the tube X is now put on exactly the same level as that in the burette by
lowering or elevating the tube X as required, the volume of NO obtained in
c.c. can be read off within 1/10 c.c., and the percentage of nitrogen
calculated by the usual formula.

[Illustration: FIG. 45.--Decomposition Flask for Schultze-Tieman Method.]

The solution of protochloride of iron is obtained by dissolving iron
nails, &c., in concentrated HCl, the iron being in excess. When the
development of hydrogen ceases, it is necessary to filter warm through a
paper filter, and acidify filtrate with a few drops of HCl. The soda
solution used has a sp. gr. of 1.210 to 1.260; equals 25° to 30° B. The
nitro-cellulose is dried in quantities of 2 grms. at 70° C. during eight
to ten hours, and then three hours in an exiccator over H_{2}SO_{4}. The
results obtained with this apparatus are very accurate. The reaction is
founded upon that of MM. Champion and Pellet's method.

~The Kjeldahl Method of Determining Nitrogen.~--This method, which has
been so largely used by analysts for the determination of nitrogen in
organic bodies, more especially perhaps in manures, was proposed by J.
Kjeldahl,[A] of the Carlsberg Laboratory of Copenhagen. It was afterwards
modified by Jodlbauer, of Munich,[B] and applied to the analysis of nitro-
explosives by M. Chenel, of the Laboratoire Centrale des Poudres, whose
method of procedure is as follows:--0.5 grm. of the finely powdered
substance is digested in the cold with a solution of 1.2 grm. of phenol
and 0.4 grm. phosphoric anhydride in 30 c.c. of sulphuric acid. The
mixture is kept well shaken until the solution is complete. From 3 to 4
grms. of zinc-dust is then cautiously and gradually added, the temperature
of the mass being kept down until complete reduction has been effected.
Finally, 0.7 grm. of mercury is added, and the process continued in the
usual way, according to Kjeldahl; that is, the liquid is distilled until
all the ammonia has passed over, and is absorbed in the standard acid. The
distillate is then titrated with standard ammonia.

[Footnote A: J. Kjeldahl, _Zeitschrift Anal. Chem._, 1883, xxii., p. 366.]

[Footnote B: Jodlbauer, _Chemisches Centralblatt_, 1886, pp. 434-484. See
also _Arms and Explosives_, 1893, p. 87.]

The NO_{2} group is at the moment of solution fixed upon the phenol with
the production of mono-nitro-phenol, which is afterwards reduced by the
action of the zinc-dust into the amido derivative. During the subsequent
combustion, the nitrogen of the amido-phenol becomes fixed in the state of
ammonia. M. Chenel is perfectly satisfied with the results obtained, but
he points out that the success of the operation depends upon the complete
conversion of the phenol into the mono-nitro derivatives. This takes place
whenever the organic compound forms a _clear solution_ in the cold
sulphuric acid mixture. Substances like collodion or gun-cotton must be
very finely divided for successful treatment. The following table shows
some of the results obtained by M. Chenel:--

 ______________________________________________
|                       |                      |
|                       |   Total Nitrogen.    |
| Substances Analysed.  |______________________|
|                       |             |        |
|                       | Calculated. | Found. |
|                       |_____________|________|
|                       |             |        |
| Saltpetre (KNO_{3})   |    13.86    |  13.91 |
|                       |             |  13.82 |
|                       |             |  13.73 |
|                       |             |  13.96 |
| Ammonium nitrate      |    35.00    |  35.31 |
|                       |             |  34.90 |
|                       |             |  34.96 |
| Barium nitrate        |    10.72    |  10.67 |
|                       |             |  10.62 |
| Nitro-glycerol        |    18.50    |  18.45 |
| Di-nitro-benzol[A]    |    16.67    |  16.78 |
|                       |             |  16.57 |
| Para-nitro-phenol     |    10.07    |  10.03 |
| Picric acid[A]        |    18.34    |  18.42 |
|                       |             |  18.43 |
| Ammonium picrate      |    22.76    |  22.63 |
|                       |             |  22.67 |
| Di-nitro-ortho-cresol |    14.14    |  14.10 |
|                       |             |  13.98 |
| Tri-nitro-meta-cresol |    17.28    |  17.57 |
|                       |             |  17.27 |
|_______________________|_____________|________|

[Footnote A: Dr. Bernard Dyer obtained 18.39 per cent. for picric acid and
16.54 per cent. for di-nitro-benzol.--_Jour. Chem. Soc._, Aug. 1895.]

When Chenel endeavoured to apply Jodlbauer's modification of Kjeldahl's
process to the examination of the tri- and tetra-nitrated naphthalenes, he
found that good results were not obtainable, because these compounds do
not dissolve completely in the cold sulphuric acid. It may, however, be
used if they are previously converted into the naphthylamines, according
to the plan proposed by D'Aguiar and Lautemann (_Bull. Soc. Chim._, vol.
iii., new series, p. 256). This is rapidly effected as follows:--Twelve
grms. of iodine are gradually added to a solution of 2 grms. of phosphorus
in about 15 or 20 c.c. of bisulphide of carbon, this solution being
contained in a flask of 250 c.c. capacity. The flask and its contents are
heated on the water bath at 100° C. with constant attention, until the
last traces of the carbon bisulphide have distilled away. It is then
cooled, and the iodide of phosphorus is detached from the sides of the
flask by shaking, but not expelled. The next step is to add about 0.5 to
0.6 grm. of the substance that is to be analysed, after which 8 grms. of
water are introduced, and the flask is agitated gently two or three times.
As soon as the reaction becomes lively, the contents of the flask are well
shaken. It is usually finished about one minute after the addition of the
water. The flask is now cooled, and 25 c.c. of sulphuric acid, together
with 0.7 grm. of mercury, are gradually added; hydriodic acid (HI) forms,
and the temperature of the flask must be raised sufficiently to expel it.
The remaining part of the operation is as in the ordinary Kjeldahl
process.

M. Chenel has found this process the best for the analysis of the nitro-
naphthalenes, and for impervious substances like collodion or gun-cotton.
Personally, I have never been able to obtain satisfactory results with
this process in the analysis of nitro-cellulose, and I am of opinion that
the process does not possess any advantage over the nitrometer method, at
any rate for the analysis of gun-cotton.

Table giving the Percentages of Nitrogen and Oxide of Nitrogen in Various
Substances used in or as Explosives:

     Name                      FORMULÆ                 NITROGEN   NO_{2}
                                                       per cent. per cent.

Nitroglycerine           C_{3}H_{5}(ONO_{2})_{3}          18.50  =  60.70
Hexa-nitro-cellulose     C_{12}H_{14}O_{4}(ONO_{2})_{6}   14.14  =  46.42
Penta-nitro-cellulose    C_{6}H_{8}O_{5}(ONO_{2})_{5}     11.11  =  36.50
Nitro-benzene            C_{6}H_{5}NO_{2}                 11.38  =  37.39
Di-nitro-benzene         C_{6}H_{4}(NO_{2})_{2}           16.67  =  54.77
Tri-nitro-benzene        C_{6}H_{3}(NO_{2})_{3}           19.24  =  63.22
Nitro-toluene            C_{7}H_{7}NO_{2}                 10.21  =  33.49
Nitro-naphthalene        C_{10}H_{7}NO_{2}                 8.09  =  26.53
Di-nitro-naphthalene     C_{10}H_{6}(NO_{2})_{2}          12.84  =  42.12
Nitro-mannite            C_{6}H_{7}(NO_{3})_{6}           23.59  =  77.37
Nitro-starch             C_{6}H_{8}O_{4}(HNO_{3})          6.76  =  22.18
Picric acid
  (Tri-nitro-phenol)     C_{6}H_{2}OH(NO_{2})_{3}         18.34  =  60.15
Chloro-nitro-benzene     C_{6}H_{3}Cl(NO_{2})_{2}         13.82  =  45.43
Ammonium nitrate         NH_{4}NO_{3}                     35.00  =
Sodium nitrate           NaNO_{3}                         16.47  =
Potassium nitrate        KNO_{3}                          13.86  =
Nitric acid              HNO_{3}                          22.22  =
Barium nitrate           Ba(NO_{3})_{2}                   10.72  =

~Analysis of Celluloid.~--The finely divided celluloid is well stirred, by
means of a platinum wire, with concentrated sulphuric acid in the cup of a
Lungé nitrometer, and when dissolved the nitrogen determined in the
solution in the usual way. To prevent interference from camphor, the
following treatment is suggested by H. Zaunschirm (_Chem. Zeit._, xiv.,
905). Dissolve a weighed quantity of the celluloid in a mixture of ether-
alcohol, mixed with a weighed quantity of washed and ignited asbestos, or
pumice-stone, dry, and disintegrate the mass, and afterwards extract the
camphor with chloroform, dry, and weigh: then extract with absolute
methyl-alcohol, evaporate, weigh, and examine the nitro-cellulose in the
nitrometer.

~Picric Acid and Picrates.~--Picric acid is soluble in hot water, and to
the extent of 1 part in 100 in cold water, also in ether, chloroform,
glycerine, 10 per cent. soda solution, alcohol, amylic alcohol, carbon
bisulphide, benzene, and petroleum. If a solution of picric acid be boiled
with a strong solution of potassium cyanide, a deep red liquid is
produced, owing to the formation of potassium iso-purpurate, which
crystallises in small reddish-brown plates with a beetle-green lustre.
This, by reaction with ammonium chloride, gives ammonium iso-purpurate
(NH_{4}C_{8}H_{4}N_{5}O_{6}), or artificial murexide, which dies silk and
wool a beautiful red colour. On adding barium chloride to either of the
above salts, a vermilion-red precipitate was formed, consisting of barium
iso-purpurate. With ammonio-sulphate of copper, solutions of picric acid
give a bright green precipitate. Mr A.H. Allen gives the following methods
for the assay of commercial picric acid, in his "Commercial Organic
Analysis":--

~Resinous and Tarry matters~ are not unfrequently present. They are left
insoluble on dissolving the sample in boiling water. The separation is
more perfect if the hot solution be exactly neutralised by caustic soda.

~Sulphuric Acid, Hydrochloric Acid, and Oxalic Acid~, and their salts are
detected by adding to the filtered aqueous solution of the sample
solutions of the picrates of barium, silver, and calcium. These salts are
readily made by boiling picric acid with the carbonates of the respective
metals and filtering: other soluble salts of these methods may be
substituted for the picrates, but they are less satisfactory.

~Nitric Acid~ may be detected by the red fumes evolved on warming the
sample with copper turnings.

~Inorganic Impurities and Picrates of Potash and Sodium~, &c., leave
residues on cautious ignition.

~General Impurities and Adulterations~ may be detected and determined by
shaking 1 grm. of the sample of acid in a graduated tube with 25 c.c. of
ether, the pure acid dissolves, while any oxalic acid, nitrates, picrates,
boric acid, alum, sugar, &c., will be left insoluble, and after removal of
the ethereal liquid, may be readily identified and determined. For the
detection and determination of water and of oxalic acid, 50 c.c. of warm
benzene may be advantageously substituted for ether. Sugar may be
separated from the other impurities by treating the residue insoluble in
ether or benzene with rectified spirit, in which sugar and boric acid
alone will dissolve. If boric acid be present, the alcoholic solution will
burn with a green flame. Mono- and di-nitrophenic acids lower the melting
point (122° C). Their calcium salts are less soluble than the picrate, and
may be approximately separated from it by fractional crystallisation, or
by precipitating the hot saturated solution of the sample with excess of
lime water. Picric acid may be determined by extracting the acidulated
aqueous solution by agitation with ether or benzene, and subsequently
removing and evaporating off the solvent. It may also be precipitated as
the potassium salt.

~Potassium Picrate~ [KC_{6}H_{2}(NO_{2})_{3}O]. When a strong solution of
picric acid is neutralised by carbonate of potash, this salt is thrown
down in yellow crystalline needles, which require 260 parts of cold or 14
parts of hot water for their solution. In alcohol it is much less soluble.

~Ammonium Picrate~ is more soluble in water than the above, and sodium
picrate is readily soluble in water, but nearly insoluble in solution of
sodium carbonate.

~Picrates of the Alkaloids.~--Picric acid forms insoluble salts with many
of the alkaloids, and picric acid may be determined in the following
manner:--To the solution of picric acid, or a picrate, add a solution of
sulphate of cinchonine acidulated with H_{2}SO_{4}. The precipitated
picrate of cinchonine [C_{20}H_{24}N_{2}O(C_{6}H_{2}N_{3}O_{7})_{2}] is
washed with cold water, rinsed off the filter into a porcelain crucible or
dish, the water evaporated on the water bath, and the residual salt
weighed. Its weight, multiplied by .6123, gives the quantity of picric
acid in the sample taken.

~Analysis of Glycerine.~[A] Glycerine that is to be used for the
manufacture of nitro-glycerine should have a minimum specific gravity of
1.261 at 15° C. This can be determined, either by the aid of a Sartorius
specific gravity balance, or by using an ordinary specific gravity bottle.
One of 10 or 25 c.c. capacity is very convenient.

[Footnote A: See also Sulman and Berry, _Analyst_, xi., 12-34, and Allen's
"Commercial Organic Analysis," vol. ii., part i.]

~Residue~[A] left upon evaporation should not be more than 0.25 per cent.
To determine this, take 25 grms. of the glycerine, and evaporate it at a
temperature of about 160° C. in a platinum basin, and finish in an air
bath. Weigh until constant weight is obtained. Afterwards incinerate over
a bunsen burner, and weigh the ash.

[Footnote A: Organic matter up to .6 per cent. is not always prejudicial
to the nitrating quantities of a glycerine.]

~Silver Test.~ A portion of the sample of glycerine to be tested should be
put in a small weighing bottle, and a quarter of its bulk of N/10 silver
nitrate solution added to it, then shake it, and place in a dark cupboard
for fifteen minutes. It must be pronounced bad if it becomes black or dark
brown within that time (acrolein, formic, and butyric acids).

The German official test for glycerine for pharmaceutical purposes is much
more stringent, 1 c.c. of glycerine heated to boiling with 1 c.c. of
ammonia solution and three drops of silver nitrate solution must give
neither colour or precipitate within five minutes.

~Nitration.~ Fifty grms. of the glycerine are poured from a beaker into a
mixture of concentrated nitric acid (specific gravity 1.53) and sulphuric
acid (1.84), mixed in the proportions of 3 HNO_{3} to 5 H_{2}SO_{4} (about
400 c.c. of mixed acids). The mixed acids should be put into a rather
large beaker, and held in the right hand in a basin of water, and the
glycerine slowly poured into them from a smaller one held in the left. A
constant rotatory motion should be given to the beaker in which the
nitration is performed. When all the glycerine has been added, and the
mixture has been shaken for a few minutes longer, it is poured into a
separator, and allowed to stand for some time. It should, if the glycerine
is a good one, have separated from the mixed acids in ten minutes, and the
line of demarcation between the nitro-glycerine and the acid should be
clear and sharp, neither should there be any white flocculent matter
suspended in the liquid. The excess of acids is now drawn off, and the
nitro-glycerine shaken once or twice with a warm solution of carbonate of
soda, and afterwards with water alone. The nitro-glycerine is then drawn
off into a weighed beaker, the surface dried with a piece of filter paper,
and weighed; 100 parts of a good glycerine should yield about 230 of
nitro-glycerine. A quicker method is to take only 10 c.c. of the
glycerine, of which the specific gravity is already known, nitrate as
before, and pour into a burette, read off the volume of nitro-glycerine in
c.c. and multiply them by 1.6 (the specific gravity of nitro-glycerine),
thus: 10 grms. gave 14.5 c.c. nitro-glycerine, and 14.5 x 1.6 = 23.2
grms., therefore 100 would give 232 grms. nitro-glycerine. The points to
be noted in the nitration of a sample of glycerine are: the separation
should be sharp, and within half an hour or less, and there should be no
white flocculent matter formed, especially when the carbonate of soda
solution is added.

~Total Acid Equivalent.~ Mr G.E. Barton (_Jour. Amer. Chem. Soc._, 1895)
proposes to determine thus: 100 c.c. of glycerine are diluted to 300 c.c.
in a beaker, a few drops of a 1 per cent. solution of phenolphthalein and
10 c.c. of normal caustic soda solution are added; after boiling, the
liquid is titrated with normal hydrochloric acid (fatty acids are thus
indicated and roughly determined).

~Neutrality.~ The same chemist determines the neutrality of glycerine
thus: 50 c.c. of glycerine mixed with 100 c.c. of water and a few drops of
alcoholic phenolphthalein[A] are titrated with hydrochloric acid or sodium
hydroxide; not more than 0.3 c.c. normal hydrochloric acid or normal soda
solution should be required to render the sample neutral; raw glycerines
contain from .5 to 1.0 per cent. of sodium carbonate.

[Footnote A: Sulman and Berry prefer litmus as indicator.]

~Determination of Free Fatty Acids.~ A weighed quantity of the glycerine
is shaken up with some neutral ether in a separating funnel, the glycerine
allowed to settle, drawn off, and the ether washed with three separate
lots of water. The water must have been recently boiled, and be quite free
from CO_{2}. All the free fatty acid is now in the ether, and no other
soluble acid. A drop of phenolphthalein is now added, a little water, and
the acidity determined by titration with deci-normal baryta solution, and
the baryta solution taken calculated as oleic acid.

~Combined Fatty Acid.~ About 30 grms. of the glycerine are placed in a
flask, and to it is added about half a grm. of caustic soda in solution.
The mixture is heated for ten minutes at 150° C. After cooling some pure
ether is added to it, and enough dilute H_{2}SO_{4} to render it
distinctly acid. It is well shaken. All the fatty acids go into the ether.
The aqueous solution is then removed, and the ether well washed to remove
all H_{2}SO_{4}. After the addition of phenolphthalein the acid is
titrated, and the amount used calculated into oleic acid. From this total
amount of fatty acids the free fatty acid is deducted, and the quantity of
combined fatty acids thus obtained.

~Impurities.~ The following impurities may be found in bad samples of
glycerine:--Lead, arsenic, lime, chlorine, sulphuric acid, thio-sulphates,
sulphides, cyanogen compounds, organic acids (especially oleic acid and
fatty acids[A]), rosin products, and other organic bodies. It is also said
to be adulterated with sugar and glucose dextrine. Traces of sulphuric
acid and arsenic may be allowed, also very small traces indeed of lime and
chlorine.

[Footnote A: These substances often cause trouble in nitrating, white
flocculent matter being formed during the process of washing.]

The organic acids, formic and butyric acids may be detected by heating a
sample of the glycerine in a test tube with alcohol and sulphuric acid,
when, if present, compound ethers, such as ethylic formate and butyrate,
the former smelling like peaches and the latter of pine-apple, will be
formed.

~Oleic Acid~, if present in large quantity, will come down upon diluting
the sample with water, but smaller quantities may be detected by passing a
current of nitrogen peroxide, N_{2}O_{4} (obtained by heating lead
nitrate), through the diluted sample, when a white flocculent precipitate
of elaidic acid, which is less soluble than oleic acid, will be thrown
down. By agitating glycerol with chloroform, fatty acids, rosin oil, and
some other impurities are dissolved, while certain others form a turbid
layer between the chloroform and the supernatant liquid. On separating the
chloroform and evaporating it to dryness, a residue is obtained which may
be further examined.

~Sodium Chloride~ can be determined in 100 c.c. of the glycerine by adding
a little water, neutralised with sodium carbonate, and then titrated with
a deci-normal solution of silver nitrate, using potassium chromate as
indicator.

~Organic Impurities~ of various kinds occur in crude glycerine, and are
mostly objectionable. Their sum may be determined with fair accuracy by
Sulman and Berry's method: 50 grms. of the sample are diluted with twice
its measure of water, carefully neutralised with acetic acid, and warmed
to expel carbonic acid; when cold, a solution of basic lead acetate is
added in slight but distinct excess, and the mixture well agitated. The
formation of an abundant precipitate, which rapidly subsides, is an
indication of considerable impurity in the sample. To ascertain its
amount, the precipitate is first washed by decantation, and then collected
on a tared, or preferably a double counter-poised filter, where it is
further washed, dried at 100° to 105° C., and weighed. The precipitate and
filter paper are then ignited separately in porcelain, at a low red heat,
the residues moistened with a few drops of nitric acid and reignited; the
weight of the lead oxide deducted from that of the original precipitate
gives the weight of the organic matter precipitated by the lead. Raw
glycerines contain from 0.5 to 1.0 per cent.

~Albuminous Matters.~ An approximate determination of the albuminous
matters may be made by precipitating with basic lead acetate as already
described, and determining the nitrogen by the Kjeldahl method; the
nitrogen multiplied by 6.25 gives the amount of albuminous matter in the
precipitate.

~The Determination of Glycerine.~ The acetin method of Benedikt and Canton
depends upon the conversion of glycerine into triacetin, and the
saponification of the latter, and reduces the estimation of glycerine to
an acidmetric method. About 1.5 grm. of crude glycerine is heated to
boiling with 7 grms. of acetic anhydride, and 3 to 4 grms. of anhydrous
sodium acetate, under an upright condenser for one and a half hours. After
cooling, 50 c.c. of water are added, and the mixture heated until all the
triacetin has dissolved. The liquid is then filtered into a large flask,
the residue on the filter is well washed with water, the filtrate quite
cooled, phenolphthalein is added and the fluid exactly neutralised with a
dilute (2 to 3 per cent.) solution of alkali. Twenty-five c.c. of a 10 per
cent. caustic soda solution, which must be accurately standardised upon
normal acid, are then pipetted into the liquid, which is heated to boiling
for ten minutes to saponify the triacetin, and the excess of alkali is
then titrated back with normal acid. One c.c. of normal acid corresponds
to .03067 grm. of glycerine.

~Precautions.~--The heating must be done with a reflux condenser, the
triacetin being somewhat volatile. The sodium acetate used must be quite
anhydrous, or the conversion of the glycerine to triacetyl is imperfect.
Triacetin in contact with water gradually decomposes. After acetylation is
complete, therefore, the operations must be conducted as rapidly as
possible. It is necessary to neutralise the free acetic acid very
cautiously, and with rapid agitation, so that the alkali may not be
locally in excess.

~The Lead Oxide Method.~--Two grms. of sample are mixed with about 40
grms. of pure litharge, and heated in an air bath to 130° C. until the
weight becomes constant, care being taken that the litharge is free from
such lead compounds and other substances as might injuriously affect the
results, and that the heating of the mixture takes place in an air bath
free from carbonic acid. The increase in weight in the litharge, minus the
weight of substance not volatilisable from 2 grms. of glycerine at 160°
C., multiplied by the factor 1.243, is taken as the weight of glycerine in
the 2 grms. of sample. The glycerine must be fairly pure, and free from
resinous substances and SO_{3}, to give good results by this process.

~Analysis of the "Waste Acids" from the Manufacture of Nitro-Glycerine or
Gun-Cotton.~ Determine the specific gravity by the specific gravity bottle
or hydrometer, and the oxides of nitrogen by the permanganate method
described under nitro-glycerine. Now determine the total acidity of the
mixture by means of a tenth normal solution of sodium hydrate, and
calculate it as nitric acid (HNO_{3}), then determine the nitric acid by
means of Lungé nitrometer, and subtract percentage found from total
acidity, and calculate the difference into sulphuric acid, thus:--

Total acidity equals 97.46 per cent.--11.07 per cent. HNO_{3} = 86.39 per
cent., then (86.39 x 49)/63 = 67.20 per cent. H_{2}SO_{4}.

Then analysis of sample will be:--

                                  _
Sulphuric acid   = 67.20 per cent. |
Nitric acid      = 11.07    "      |- Specific gravity = 1.7075.
Water            = 12.73    "     _|

This method is accurate enough for general use in the nitric acid factory.
The acid mixture may be taken by volume for determining nitric oxide in
nitrometer. Two c.c. is a convenient quantity in the above case, then 2 x
1.7075 (specific gravity) = 3.414 grms. taken, gave 145 c.c. NO (barometer
= 748 mm, and temperature = 15°C.) equals 134.9 c.c. (corr.) and as 1 c.c.
NO = .0282 grm. HNO_{3} 135 x .0282 = .378 grm. = 11.07 per cent. nitric
acid.

~Sodium Nitrate.~ Determine moisture and chlorine by the usual methods,
and the total, NaNO_{3}, by means of nitrometer--0.45 grm. is a very
convenient quantity to work on (gives about 123 c.c. gas); grind very
fine, and dissolve in a very little hot water in the cup of the
nitrometer; use about 15 c.c. concentrated H_{2}SO_{4}. One cubic cent. of
NO equals .003805 grm. of NaNO_{3}. The insoluble matter, both organic and
inorganic, should also be determined, also sulphate of soda and lime
tested for.

~Analysis of Mercury Fulminate (Divers and Kawakita's Method).~--A weighed
quantity of mercury fulminate is added to excess, but measured quantity of
fuming hydrochloric acid contained in a retort connected with a receiver
holding water. After heating for some time, the contents of the retort and
receiver are mixed and diluted, and the mercury is precipitated by
hydrogen sulphide. By warming and exposure to the air in open vessels the
hydrogen sulphide is for the most part dissipated. The solution is then
titrated with potassium hydroxide (KOH), as well as another quantity of
hydrochloric acid, equal to that used with the fulminate. As the mercury
chloride is reconverted into hydrochloric acid by the hydrogen sulphide,
and as the hydroxylamine does not neutralise to litmus the hydrochloric
acid combined with it, there is an equal amount of hydrochloric acid free
or available in the two solutions. Any excess of acid in the one which has
received the fulminate will therefore be due to the formic acid generated
from the fulminate. Dr. Divers and M. Kawakita, working by this method,
have obtained 31.31 per cent. formic acid, instead of 32.40 required by
theory. (_Jour. Chem. Soc._, p. 17, 1884.)

Divers and Kawakita proceed thus: 2.351 grms. dissolved, as already
described, in HCl, and afterwards diluted, gave mercury sulphide equal to
70.40 per cent. mercury. The same solution, after removal of mercury,
titrated by iodine for hydroxylamine, gave nitrogen equal to 9.85 per
cent., and when evaporated with hydroxyl ammonium chloride equal to 9.55
per cent. A solution of 2.6665 grms. fulminate in HCl of known amount,
after removal of mercury by hydrogen sulphide, gave by titration with
potassium hydrate, formic acid equal to 8.17 per cent. of carbon.
Collecting and comparing with calculation from formula we get--

            Calc.    I.    II.    III.

Mercury     70.42  70.40   ...    ...
Nitrogen     9.86   9.85   9.55   ...
Carbon       8.45   ...    ...    8.17
Oxygen      11.27   ...    ...    ...
          _______

           100.00

~The Analysis of Cap Composition.~--Messrs F.W. Jones and F.A. Willcox
(_Chem. News_, Dec. 11, 1896) have proposed the following process for the
analysis of this substance:--Cap composition usually consists of the
ingredients--potassium chlorate, antimony sulphide, and mercury fulminate,
and to estimate these substances in the presence of each other by ordinary
analytical methods is a difficult process. Since the separation of
antimony sulphide and mercury fulminate in the presence of potassium
chlorate necessitates the treatment of the mixture with hydrochloric acid,
and this produces an evolution of hydrogen sulphide from the sulphide, and
a consequent precipitation of sulphur; and potassium chlorate cannot be
separated from the other ingredients by treatment with water, owing to the
appreciable solubility of mercury fulminate in cold water.

In the course of some experiments on the solubility of mercury fulminate
Messrs Jones and Willcox observed that this body was readily soluble in
acetone and other ethereal solvents when they were saturated with ammonia
gas, and that chlorate of potash and sulphide of antimony were insoluble
in pure acetone saturated with ammonia; these observations at once
afforded a simple method of separating the three ingredients of cap
composition. By employing this solution of acetone and ammonia an analysis
can be made in a comparatively short time, and yields results of
sufficient accuracy for all technical purposes. The following are the
details of the process:--

A tared filter paper is placed in a funnel to the neck of which has been
fitted a piece of rubber tubing provided with a clip. The paper is
moistened with a solution of acetone and ammonia, the cap composition is
weighed off directly on to the filter paper and is then covered with the
solution of acetone and ammonia and allowed to stand thirty-four hours. It
is then washed repeatedly with the same solution until the washings give
no coloration with ammonium sulphide, and afterwards washed with acetone
until washings give no residue on evaporation dried and weighed. The paper
is again put in the funnel and washed with water until free from potassium
chlorate, dried and weighed.

If _c_ = weight of composition taken,
   _d_ =   "    " filter paper,
   _a_ =   "    after first extraction,
   _b_ =   "     "    second extraction,
   then _c+d-a_   = weight of fulminate,
        _c+d-a-b_ =  "     " KClO_{3},
        _b-d_     =  "     " sulphide of antimony.

The composition should be finely ground in an agate mortar.

The results of the analysis by this method of two mixtures of known
composition are given below--

 ________________________________________________________________________
|                    |                         |                         |
|                    |            A            |            B            |
|                    |                         |                         |
|                    | Percentage | Percentage | Percentage | Percentage |
|                    |   Taken.   |   Found.   |   Taken.   |   Found.   |
|____________________|____________|____________|____________|____________|
|                    |            |            |            |            |
| Antimony Sulphide  |   36.47    |   36.25    |   37.34    |   37.22    |
| Potassium Chlorate |   33.25    |   33.71    |   46.03    |   46.43    |
| Mercury Fulminate  |   30.27    |   30.02    |   16.61    |   16.34    |
|____________________|____________|____________|____________|____________|

Dr. H.W. Brownsdon's (_Jour. Soc. Chem. Ind._, xxiv., April 1905) process
is as follows:--The cap composition is removed by squeezing the cap with
pliers, while held over a porcelain basin of about 200 c.c. capacity, and
removing the loosened foil and broken composition by means of a pointed
wooden chip. Composition adhering to the shell or foil is loosened by
alcohol, and washed into the dish by means of alcohol in a small wash
bottle. The shell and foil are put to one side and subsequently weighed
when dry. The composition in the dish is broken down quite fine with a
flat-headed glass rod, and the alcohol evaporated on the water bath till
the residue is moist, but not quite dry, 25 c.c. of water are then added,
and the composition well stirred from the bottom. After the addition of
0.5 grm. of pure sodium, thiosulphate, the contents of the dish, is well
stirred for two and a half minutes. One drop of methyl orange is then
added, and the solution titrated with N/20 sulphuric acid, which has been
standardised against weighings of 0.05-0.1 grm. fulminate to which 25 c.c.
of water is added in a porcelain dish, then 0.5 grm. of thiosulphate, and
after stirring for two and a half minutes, titrated with N/20 sulphuric
acid. The small amount of antimony sulphide present does not interfere
with the recognition of the end point. After titration, the solution is
filtered through a small 5-1/2 cm. filter paper, which retains the
antimony sulphide. The filter paper containing the Sb_{2}S_{3} is well
washed and then transferred to a large 6 by 1 test tube. Five c.c. of
strong hydrochloric acid are added, and the contents of the tube boiled
gently for a few seconds until the sulphide is dissolved and all the
H_{2}S driven off or decomposed: 2-3 c.c. of a saturated solution of
tartaric acid are added, and the contents of the tube washed into a 250
c.c. Erlenmeyer flask. The solution is then nearly neutralised with sodium
carbonate, excess of bi-carbonate added, and after the addition of some
starch solution titrated with N/20 iodine solution. This method for small
quantities of stibnite is both quick and accurate, the error being about
±0.0003 grm. Sb_{2}S_{3} at the outside.

The tendency of this method is to give slightly low figures for the
fulminate, but since these are uniform within a negligible error, it does
not affect the value of the results as a criterion of uniformity. The
following test results were obtained by Dr Brownsdon:--

 ____________________________________________________________
|                    |                   |                   |
|  Fulminate Taken.  |  Fulminate Found. |      Error.       |
|        Grm.        |       Grm.        |       Grm.        |
|                    |                   |                   |
|       0.0086       |      0.0083       |     -0.0003       |
|       0.0082       |      0.0081       |     -0.0001       |
|       0.0074       |      0.0071       |     -0.0003       |
|       0.0068       |      0.0066       |     -0.0002       |
|____________________|___________________|___________________|
|                    |                   |                   |
|  Stibnite Taken.   |Sb_{2}S_{3}, Found.|      Error.       |
|        Grm.        |       Grm.        |       Grm.        |
|                    |                   |                   |
|       0.0085       |      0.0084       |     -0.0001       |
|       0.0098       |      0.0099       |     +0.0001       |
|       0.0160       |      0.0157       |     -0.0003       |
|       0.0099       |      0.0100       |     +0.0001       |
|____________________|___________________|___________________|

TABLE FOR CORRECTION OF VOLUMES OF GASES FOR TEMPERATURE, GIVING THE
DIVISOR FOR THE FORMULA.

V_{1} = V x B/(760 x (1 + dt)) (d = 0.003665) 1 + dt from 0° to 30° C.

___________________________________________________________
     |             |     |             |     |
 t.  | 760x(1+dt). | t.  | 760x(1+dt). | t.  | 760x(1+dt).
_____|_____________|_____|_____________|_____|_____________
     |             |     |             |     |
 °C. |             | °C. |             | °C. |
 0.0 |  750.000    | 1.7 |  764.7352   | 3.4 |  769.4704
  .1 |  760.2785   |  .8 |  765.0137   |  .5 |  769.7489
  .2 |  760.5571   |  .9 |  765.2923   |  .6 |  770.0274
  .3 |  760.8356   | 2.0 |  765.5708   |  .7 |  770.3060
  .4 |  761.1142   |  .1 |  765.8493   |  .8 |  770.5845
  .5 |  761.3927   |  .2 |  766.1279   |  .9 |  770.8631
  .6 |  761.6712   |  .3 |  766.4064   | 4.0 |  771.1416
  .7 |  761.9498   |  .4 |  766.6850   |  .1 |  771.4201
  .8 |  762.2283   |  .5 |  766.9635   |  .2 |  771.6987
  .9 |  762.5069   |  .6 |  767.2420   |  .3 |  771.9772
 1.0 |  762.7854   |  .7 |  767.5206   |  .4 |  772.2558
  .1 |  763.0639   |  .8 |  767.7991   |  .5 |  772.5343
  .2 |  763.3425   |  .9 |  768.0777   |  .6 |  772.8128
  .3 |  763.6210   | 3.0 |  768.3562   |  .7 |  773.0914
  .4 |  763.8996   |  .1 |  768.6347   |  .8 |  773.3699
  .5 |  764.1781   |  .2 |  768.9133   |  .9 |  773.6485
  .6 |  764.4566   |  .3 |  769.1918   | 5.0 |  773.9270
_____|_____________|_____|_____________|_____|_____________
___________________________________________________________
     |             |     |             |     |
 t.  | 760x(1+dt). | t.  | 760x(1+dt). | t.  | 760x(1+dt).
_____|_____________|_____|_____________|_____|_____________
     |             |     |             |     |
 °C. |             | °C. |             | °C. |
 5.1 |  774.2055   |  .9 |  787.5755   |  .7 |  800.9454
  .2 |  774.4841   |10.0 |  787.8540   |  .8 |  801.2239
  .3 |  774.7626   |  .1 |  788.1325   |  .9 |  801.5025
  .4 |  775.0412   |  .2 |  788.4111   |15.0 |  801.7810
  .5 |  775.3197   |  .3 |  788.6896   |  .1 |  802.0595
  .6 |  775.5982   |  .4 |  788.9682   |  .2 |  802.3381
  .7 |  775.8768   |  .5 |  789.2467   |  .3 |  802.6166
  .8 |  776.1553   |  .6 |  789.5252   |  .4 |  802.8952
  .9 |  776.4339   |  .7 |  789.8038   |  .5 |  803.1737
 6.0 |  776.7124   |  .8 |  790.0823   |  .6 |  803.4522
  .1 |  776.9909   |  .9 |  790.3609   |  .7 |  803.7308
  .2 |  777.2695   |11.0 |  790.6394   |  .8 |  804.0093
  .3 |  777.5480   |  .1 |  790.9179   |  .9 |  804.2879
  .4 |  777.8266   |  .2 |  791.1965   |16.0 |  804.5664
  .5 |  778.1051   |  .3 |  791.4750   |  .1 |  804.8449
  .6 |  778.3836   |  .4 |  791.7536   |  .2 |  805.1235
  .7 |  778.6622   |  .5 |  792.0321   |  .3 |  805.4020
  .8 |  778.9407   |  .6 |  792.3106   |  .4 |  805.6806
  .9 |  779.2193   |  .7 |  792.5892   |  .5 |  805.9591
 7.0 |  779.4978   |  .8 |  792.8677   |  .6 |  806.2376
  .1 |  779.7763   |  .9 |  793.1463   |  .7 |  806.5162
  .2 |  780.0549   |12.0 |  793.4248   |  .8 |  806.7947
  .3 |  780.3334   |  .1 |  793.7033   |  .9 |  807.0733
  .4 |  780.6120   |  .2 |  793.9819   |17.0 |  807.3518
  .5 |  780.8905   |  .3 |  794.2604   |  .1 |  807.6303
  .6 |  781.1690   |  .4 |  794.5390   |  .2 |  807.9089
  .7 |  781.4476   |  .5 |  794.8175   |  .3 |  808.1874
  .8 |  781.7261   |  .6 |  795.0960   |  .4 |  808.4660
  .9 |  782.0047   |  .7 |  795.3746   |  .5 |  808.7445
 8.0 |  782.2832   |  .8 |  795.6531   |  .6 |  809.0230
  .1 |  782.5617   |  .9 |  795.9317   |  .7 |  809.3016
  .2 |  782.8403   |13.0 |  796.2102   |  .8 |  809.5801
  .3 |  783.1188   |  .1 |  796.4887   |  .9 |  809.8587
  .4 |  783.3974   |  .2 |  796.7673   |18.0 |  810.1372
  .5 |  783.6959   |  .3 |  797.0458   |  .1 |  810.4175
  .6 |  783.9544   |  .4 |  797.3244   |  .2 |  810.6943
  .7 |  784.2330   |  .5 |  797.6029   |  .3 |  810.9728
  .8 |  784.5115   |  .6 |  797.8814   |  .4 |  811.2514
  .9 |  784.7901   |  .7 |  798.1600   |  .5 |  811.5299
 9.0 |  785.0686   |  .8 |  798.4385   |  .6 |  811.8084
  .1 |  785.3471   |  .9 |  798.7171   |  .7 |  812.0870
  .2 |  785.6257   |14.0 |  798.9956   |  .8 |  812.3655
  .3 |  785.9042   |  .1 |  799.2741   |  .9 |  812.6441
  .4 |  786.1828   |  .2 |  799.5527   |19.0 |  812.9226
  .5 |  786.4613   |  .3 |  799.8312   |  .1 |  813.2011
  .6 |  786.7398   |  .4 |  800.1098   |  .2 |  813.4797
  .7 |  787.0184   |  .5 |  800.3883   |  .3 |  813.7582
  .8 |  787.2969   |  .6 |  800.6668   |  .4 |  814.0368
_____|_____________|_____|_____________|_____|_____________
___________________________________________________________
     |             |     |             |     |
 t.  | 760x(1+dt). | t.  | 760x(1+dt). | t.  | 760x(1+dt).
_____|_____________|_____|_____________|_____|_____________
     |             |     |             |     |
 °C. |             | °C. |             | °C. |
19.5 |  814.3153   |23.0 |   824.0642  |  .5 |   833.8131
  .6 |  814.5938   |  .1 |   824.3427  |  .6 |   834.0916
  .7 |  814.8724   |  .2 |   824.6213  |  .7 |   834.3702
  .8 |  815.1500   |  .3 |   824.8998  |  .8 |   834.6487
  .9 |  815.4925   |  .4 |   825.1784  |  .9 |   834.9273
20.0 |  815.7080   |  .5 |   825.4569  |27.0 |   835.2058
  .1 |  815.9865   |  .6 |   825.7354  |  .1 |   835.4843
  .2 |  816.2651   |  .7 |   826.0140  |  .2 |   835.7629
  .3 |  816.5436   |  .8 |   826.2925  |  .3 |   836.0414
  .4 |  816.8222   |  .9 |   826.5711  |  .4 |   836.3200
  .5 |  817.1007   |24.0 |   826.8496  |  .5 |   836.5985
  .6 |  817.3792   |  .1 |   827.1281  |  .6 |   836.8770
  .7 |  817.6578   |  .2 |   827.4067  |  .7 |   837.1556
  .8 |  817.9363   |  .3 |   827.6852  |  .8 |   837.4341
  .9 |  818.2149   |  .4 |   827.9638  |  .9 |   837.7127
21.0 |  818.4934   |  .5 |   828.2423  |28.0 |   837.9912
  .1 |  818.7719   |  .6 |   828.5208  |  .1 |   838.2697
  .2 |  819.0505   |  .7 |   828.7994  |  .2 |   838.5483
  .3 |  819.3290   |  .8 |   829.0779  |  .3 |   838.8268
  .4 |  819.6076   |  .9 |   829.3565  |  .4 |   839.1054
  .5 |  819.8861   |25.0 |   829.6350  |  .5 |   839.3839
  .6 |  820.1646   |  .1 |   829.9135  |  .6 |   839.6624
  .7 |  820.4432   |  .2 |   830.1921  |  .7 |   839.9410
  .8 |  820.7217   |  .3 |   830.4706  |  .8 |   840.2195
  .9 |  821.0003   |  .4 |   830.7492  |  .9 |   840.4981
22.0 |  821.2788   |  .5 |   831.0277  |29.0 |   840.7766
  .1 |  821.5573   |  .6 |   831.3062  |  .1 |   841.0551
  .2 |  821.8859   |  .7 |   831.5848  |  .2 |   841.3337
  .3 |  822.1144   |  .8 |   831.8633  |  .3 |   841.6122
  .4 |  822.3930   |  .9 |   832.1419  |  .4 |   841.8908
  .5 |  822.6715   |26.0 |   832.4204  |  .5 |   842.1693
  .6 |  822.9500   |  .1 |   832.6989  |  .6 |   842.4478
  .7 |  823.2286   |  .2 |   832.9775  |  .7 |   842.7264
  .8 |  823.5071   |  .3 |   833.2560  |  .8 |   843.0049
  .9 |  823.7857   |  .4 |   833.5346  |  .9 |   843.2835
     |             |     |             |30.0 |   843.5620
_____|_____________|_____|_____________|_____|_____________




CHAPTER VIII.

_FIRING POINT OF EXPLOSIVES, HEAT TESTS, &c._

Horsley's Apparatus--Table of Firing points--The Government Heat-Test
Apparatus for Dynamites--Nitro-Glycerine, Nitro-Cotton, and Smokeless
Powders--Liquefaction and Exudation Tests--Page's Regulator for Heat-Test
Apparatus--Specific Gravities of Explosives--Table of Temperature of
Detonation, Sensitiveness, &c.


~The Firing Point of Explosives.~--The firing point of an explosive may be
determined as follows:--A copper dish, about 3 inches deep, and 6 or more
wide, and fitted with a lid, also of copper, is required. The lid contains
several small holes, into each of which is soldered a thick copper tube
about 5 mm. in diameter, and 3 inches long, with a rather larger one in
the centre in which to place a thermometer. The dish is filled with Rose's
metal, or paraffin, according to the probable temperature required. The
firing point is then taken thus:--After putting a little piece of asbestos
felt at the bottom of the centre tube, the thermometer is inserted, and a
small quantity of the explosive to be tested is placed in the other holes;
the lid is then placed on the dish containing the melted paraffin or
metal, in such a way that the copper tubes dip below the surface of the
liquid; the temperature of the bath is now raised until the explosive
fires, and the temperature noted. The initial temperature should also be
noted.

THE FIRING POINT OF VARIOUS EXPLOSIVES (by C. E. Munroe).
(Horsley's Apparatus used.)

_____________________________________________________________________
                                                          |
                                                          |   °C.
Nitro-glycerine, 5 years old (a single drop taken)        | 203-205
Gun-cotton (compressed military cotton, sp. gr. 1.5)      | 192-201
Air-dried gun-cotton, stored for 4 years                  | 179-187
Ditto, stored for 1 year                                  | 187-189
Air-dried collodion-cotton, long  staple "Red Island      |
  cotton," 3 years old                                    | 186-191
Air-dried collodion, 3 years old, stored wet              | 197-199
Hydro-nitro-cellulose                                     | 201-213
Kieselguhr dynamite, No. 1                                | 197-200
Explosive gelatine                                        | 203-209
Mercury fulminate                                         | 175-181
Gunpowder (shell)                                         | 278-287
Hill's picric powder (shells) Been in store 10 years.     | 273-283
Ditto (musket)                Composed of--               | 282-290
                              Ammonium picrate    42.18 % |
                              Potassium picrate   53.79 " |
                              Charcoal (alder)     3.85 " |
                                                 ________ |
                                                          |
                                                  99.82   |
Forcite, No. 1                                            | 187-200
Atlas powder (75% NG)                                     | 175-185
Emmensite, No. 1              Sample had been stored in   | 167-184
                              magazine for some months in |
                              a wooden box.               |
   "       No. 2      Stored in tin case.                 | 165-177
   "       No. 5        "            "                    | 205-217
__________________________________________________________|__________
                                  |         |
                                  |   °C.   |
Powder used in Chassepôt rifle    |   191   |  By Leygue & Champion.
French gunpowder                  |   295   |      "          "
Rifle powder (picrate)            |   358   |      "          "
Cannon                            |   380   |      "          "
__________________________________|_________|________________________

Horsley's apparatus consists of an iron stand with a ring support, holding
a hemispherical iron vessel or bath in which solid paraffin is put. Above
this is another movable support, from which a thermometer is suspended,
and so adjusted that its bulb is immersed in the material contained in the
iron vessel. A thin copper cartridge-case, 5/8 inch in diameter and
1-15/16 inch long, is suspended over the bath by means of a triangle, so
that the end of the case is just 1 inch below the surface of the molten
material. On beginning the experiment of determining the firing point of
any explosive, the material in the bath is heated to just above the
melting point; the thermometer is inserted in it, and a minute quantity of
the explosive is placed in the bottom of the cartridge-case. The initial
temperature is noted, and then the cartridge-case containing the explosive
is inserted in the bath. The temperature is quickly raised until the
contents of the cartridge-case flash off or explode, when the temperature
is noted as the _firing point_.

[Illustration: FIG. 46.--HEAT TEST APPARATUS.]

Professor C.E. Munroe, of the U.S. Torpedo Station, has determined the
firing point of several explosives by means of this apparatus.

~The Government Heat Test (Explosives Act, 1875): Apparatus required.~--A
water bath, consisting of a spherical copper vessel _(a)_, Fig. 46, of
about 8 inches diameter, and with an aperture of about 5 inches; the bath
is filled with water to within a quarter of an inch of the edge. It has a
loose cover of sheet copper about 6 inches in diameter _(b)_ and rests on
a tripod stand about 14 inches high _(c)_, which is covered with coarse
wire gauze _(e)_, and is surrounded with a screen of thin sheet copper
_(d)_. Within the latter is placed an argand burner _(f)_ with glass
chimney. The cover _(b)_ has four holes arranged, as seen in Fig. II., No.
4 to contain a Page's[A] or Scheibler's regulator, No. 3 the thermometer,
Nos. 1 and 2 the test tubes containing the explosive to be tested. Around
the holes 1 and 2 on the under side of the cover are soldered three pieces
of brass wire with points slightly converging (Fig. III.); these act as
springs, and allow the test tubes to be easily placed in position and
removed.

[Footnote A: See _Chem. Soc. Jour._, 1876, i. 24. F.J.M. Page.]

~Test Tubes~, from 5-1/4 to 5-1/2 inches long, and of such a diameter that
they will hold from 20 to 22 cubic centimetres of water when filled to a
height of 5 inches; rather thick glass is preferable. Indiarubber
stoppers, fitting the test tubes, and carrying an arrangement for holding
the test papers, viz., a narrow glass tube passing through the centre of
the stopper, and terminating in a platinum wire hook. A glass rod drawn
out and the end turned up to form a hook is better.

~The Thermometer~ should have a range from 30° to 212° F., or from 1° to
100° C. A minute clock is useful.

~Test Paper.~--The test paper is prepared as follows:--45 grains (2.9
grms.) of white maize starch (corn flour), previously washed with cold
water, are added to 8-1/2 oz. of water. The mixture is stirred, heated to
boiling, and kept gently boiling for ten minutes; 15 grains (1 grm.) of
pure potassium iodide (previously recrystallised from alcohol, absolutely
necessary) are dissolved in 8-1/2 oz. of distilled water. The two
solutions are thoroughly mixed and allowed to get cold. Strips or sheets
of white English filter paper, previously washed with water and re-dried,
are dipped into the solution thus prepared, and allowed to remain in it
for not less than ten seconds; they are then allowed to drain and dry in a
place free from laboratory fumes and dust. The upper and lower margins of
the strips or sheets are cut off, and the paper is preserved in well-
stoppered or corked bottles, and in the dark. The dimensions of the pieces
of test paper used are about 4/10 inch by 8/10 inch (10 mm. by 20 mm.).[A]

[Footnote A: When the paper is freshly prepared, and as long as it remains
in good condition, a drop of diluted acetic acid put on the paper with a
glass rod produces no coloration. In process of time it will become
brownish, when treated with the acid, especially if it has been exposed to
sunlight. It is then not fit for use.]

In Germany zinc-iodide starch paper is used, which is considered to be
more sensitive than potassium iodide.

~Standard Tint Paper.~--A solution of caramel in water is made of such
concentration that when diluted one hundred times (10 c.c. made up to 1
litre) the tint of this diluted solution equals the tint produced by the
Nessler test in 100 c.c. water containing .000075 grm. of ammonia, or
.00023505 grm. AmCl. With this caramel solution lines are drawn on strips
of white filter paper (previously well washed with distilled water, to
remove traces of bleaching matter, and dried) by means of a quill pen.
When the marks thus produced are dry, the paper is cut into pieces of the
same size as the test paper previously described, in such a way that each
piece has a brown line across it near the middle of its length, and only
such strips are preserved in which the brown line has a breadth varying
from 1\2 mm. to 1 mm. (1/50 of an inch to 1/25 of an inch).

~Testing Dynamite, Blasting Gelatine, and Gelatine Dynamite.~--Nitro-
glycerine preparations, from which the nitro-glycerine can be extracted in
the manner described below, must satisfy the following test, otherwise
they will not be considered as manufactured with "thoroughly purified
nitro-glycerine," viz., fifteen minutes at 160° F. (72° C.).

~Apparatus required.~--A funnel 2 inches across (_d_), a cylindrical
measure divided into grains (_e_), Fig. 47.

~Mode of Operation.~--About 300 (19.4 grms.) to 400 grains (26 grms.) of
dynamite (_b_), finely divided, are placed in the funnel, which is loosely
plugged by freshly ignited asbestos (_a_). The surface is smoothed by
means of a flat-headed glass rod or stopper, and some clean washed and
dried kieselguhr (_c_) is spread over it to the depth of about 1/8 inch.
Water is then poured on from a wash bottle, and when the first portion has
been soaked up more is added; this is repeated until sufficient nitro-
glycerine has collected in the graduated measure (_e_). If any water
should have passed through, it must be removed from the nitro-glycerine by
filter paper, or the nitro-glycerine may be filtered.

[Illustration: FIG. 47.--APPARATUS FOR SEPARATING THE NlTRO-GLYCERINE FROM
DYNAMITE.]

[Illustration: FIG. 48.--TEST TUBE ARRANGED FOR HEAT TEST.]

~Application of Test.~--The thermometer is fixed so as to be inserted
through the lid of the water bath into the water, which is maintained at
160° F. (72° C.), to a depth of 2-3/4 inches. Fifty grains (= 3.29 grms.)
of nitro-glycerine to be tested are weighed into the test tube, in such a
way as not to soil the sides of the tube (use a pipette). A test paper is
fixed on the hook of the glass rod, so that when inserted into the tube it
will be in a vertical position. A sufficient amount of a mixture of half
distilled water and half glycerine, to moisten the upper half of the
paper, is now applied to the upper edge of the test paper by means of a
glass rod or camel's hair pencil; the cork carrying the rod and paper is
fixed into the test tube, and the position of the paper adjusted so that
its lower edge is about half way down the tube; the latter is then
inserted through one of the holes in the cover to such a depth that the
lower margin of the moistened part of the paper is about 5/8 inch above
the surface cover. The test is complete when the faint brown line, which
after a time makes its appearance at the line of boundary between the dry
and moist part of the paper, equals in tint the brown line of the standard
tint paper.

~Blasting Gelatine, Gelatine Dynamite, Gelignite, &c.~--Fifty grains (=
3.29 grms.) of blasting gelatine are intimately mixed with 100 grains (=
6.5 grms.) of French chalk. This is done by carefully working the two
materials together with a wooden pestle in a wooden mortar. The mixture is
then gradually introduced into the test tube, with the aid of gentle
tapping upon the table between the introduction of successive portions of
the mixture into the tube, so that when the tube contains all the mixture
it shall be filled to the extent of 1-3/4 inch of its height. The test
paper is then inserted as above described for nitro-glycerine. The sample
tested must stand a temperature of 160° F. for a period of ten minutes
before producing a discoloration of the test paper corresponding in tint
to the standard paper.

_N.B._--Non-gelatinised nitro-glycerine preparations, from which the
nitro-glycerine cannot be expelled by water, are tested without any
previous separation of the ingredients, the temperature being as above
160° F., and the time being seven minutes.

~Gun-Cotton, Schultze Gunpowder, E.C. Powder, &c.: A. Compressed Gun-
Cotton.~--Sufficient material to serve for two or more tests is removed
from the centre of the cartridge by gentle scraping, and if necessary,
further reduced by rubbing between the fingers. The fine powder thus
produced is spread out in a thin layer upon a paper tray 6 inches by 4-1/2
inches, which is then placed inside a water oven, kept as nearly as
possible at 120° F. (49° C.). The wire gauze shelves of the oven should be
about 3 inches apart. The sample is allowed to remain at rest for fifteen
minutes in the oven, the door of which is left wide open. After the lapse
of fifteen minutes the tray is removed and exposed to the air of the room
for two hours, the sample being at some point within that time rubbed upon
the tray with the hand, in order to reduce it to a fine and uniform state
of division.

The heat test is performed as before, except that the temperature of the
bath is kept at 170° F. (66° C.), and regulator set to maintain that
temperature. Twenty grains (1.296 grm.) are used, placed in the test tube,
gently pressed down until it occupies a space of as nearly as possible
1-5/10 inch in the test tube of dimensions previously specified. The fine
cotton adhering to the sides of the tube can be removed by a clean cloth
or silk handkerchief. The paper is moistened by touching the upper edge
with a drop of the 50 per cent. glycerine solution, the tube inserted in
the bath to a depth of 2-1/2 inches, measured from the cover, the
regulator and thermometer being inserted to the same depth. The test paper
is to be kept near the top of the test tube, but clear of the cork, until
the tube has been immersed for about five minutes. A ring of moisture will
about this time be deposited upon the sides of the test tube, a little
above the cover of the bath. The glass rod must then be lowered until the
lower margin of the moistened part of the paper is on a level with the
bottom of the ring of moisture in the tube. The paper is now closely
watched, The test is complete when a very faint brown coloration makes its
appearance at the line of boundary between the dry and moist parts of the
paper. It must stand the test for not less than ten minutes at 170° F.
(The time is reckoned from the first insertion of the tube in the bath
until the appearance of a discoloration of the test paper.)

~B. Schultze Powder, E.C. Powder, Collodion-Cotton, &c.~--The sample is
dried in the oven as above for fifteen minutes, and exposed for two hours
to the air. The test as above for compressed gun-cotton is then applied.

~C. Cordite~ must stand a temperature of 180° F. for fifteen minutes. The
sample is prepared as follows:--Pieces half an inch long are cut from one
end of every stick selected for the test: in the case of the thicker
cordites, each piece so cut is further subdivided into about four
portions. These cut pieces are then passed once through the mill, the
first portion of material which passes through being rejected on account
of the possible presence of foreign matter from the mill. The ground
material is put on the top sieve of the nest of sieves, and sifted. That
portion which has passed through the top sieve and been stopped by the
second is taken for the test. If the mill is properly set, the greater
portion of the ground material will be of the proper size. If the volatile
matter in the explosive exceeds 0.5 per cent., the sifted material should
be dried at a temperature not exceeding 140° F, until the proportion does
not exceed 0.5 per cent. After each sample has been ground, the mill must
be taken to pieces and carefully cleaned. The sieves used consist of a
nest of two sieves with holes drilled in sheet copper. The holes in the
top sieve have a diameter = 14 B.W.G., those in the second = 21 B.W.G.

If too hard for the mill, the cordite may be softened by exposure to the
vapour of acetone,[A] or reduced, to the necessary degree of subdivision
by means of a sharp moderately-coarse rasp. Should it have become too soft
in the acetone vapour for the mill, it should be cut up into small pieces,
which may be brought to any desired degree of hardness by simple exposure
to air. Explosives which consist partly of gelatinised collodion-cotton,
and partly of ungelatinised gun-cotton, are best reduced to powder by a
rasp, or softened by exposure to mixed ether and alcohol vapour at a
temperature of 40° F. to 100° F.

[Footnote A: Mr W. Cullen _(Jour. Soc. Chem. Ind._, Jan. 31, 1901) says:--
"Undoubtedly the advent of the horny smokeless powders of modern times has
made it a little difficult to give the test the same scope as it had when
first introduced." As a rule a simple explanation can be found for every
apparently abnormal result, and in the accidental retention of a portion
of the solvent used in the manufacture, will frequently be found an
explanation of the trouble experienced.]

~Ballistite.~--In the case of ballistite the treatment is the same, except
that when it is in a very finely granulated condition it need not be cut
up.

~Guttmann's Heat Test.~--This test was proposed by Mr Oscar Guttmann in a
paper read before the Society of Chemical Industry (vol. xvi., 1897), in
the place of the potassium iodide starch paper used in the Abel test. The
filter paper used is wetted with a solution of diphenylamine[A] in
sulphuric acid. The solution is prepared as follows:--Take 0.100 grm. of
diphenylamine crystals, put them in a wide-necked flask with a ground
stopper, add 50 c.c. of dilute sulphuric acid (10 c.c. of concentrated
sulphuric acid to 40 c.c. of water), and put the flask in a water bath at
between 50° and 55° C. At this temperature the diphenylamine will melt,
and at once dissolve in the sulphuric acid, when the flask should be taken
out, well shaken, and allowed to cool. After cooling, add 50 c.c. of
Price's double distilled glycerine, shake well, and keep the solution in a
dark place. The test has to be applied in the following way:--The
explosives that have to be tested are finely subdivided, gun-cotton,
nitro-glycerine, dynamite, blasting gelatine, &c., in the same way as at
present directed by the Home Office regulations. Smokeless powders are all
to be ground in a bell-shaped coffee mill as finely as possible, and
sifted as hitherto. 1.5 grm. of the explosive (from the second sieve in
the case of smokeless powder) is to be weighed off and put into a test
tube as hitherto used. Strips of well-washed filter paper, 25 mm. wide,
are to be hung on a hooked glass rod as usual. A drop of the diphenylamine
solution is taken up by means of a clean glass rod, and the upper corners
of the filter paper are touched with it, so that when the two drops run
together about a quarter of the filter paper is moist. This is then put
into the test tube, and this again into the water bath, which has been
heated to 70° C. The heat test reaction should not show in a shorter time
than fifteen minutes. It will begin by the moist part of the paper
acquiring a greenish yellow colour, and from this moment the paper should
be carefully watched. After one or two minutes a dark blue mark will
suddenly appear on the dividing line between the wet and dry part of the
filter paper, and this is the point that should be taken.

[Footnote A: Dr G. Spica (_Rivista_, Aug. 1897) proposes to use
hydrochloride of meta-phenylenediamine.]

~Exudation and Liquefaction Test for Blasting Gelatine, Gelatine Dynamite,
&c.~--A cylinder of blasting gelatine, &c., is to be cut from the
cartridge to be tested, the length of the cylinder to be equal to its
diameter, and the ends being cut flat. The cylinder is to be placed on end
on a flat surface without any wrapper, and secured by a pin passing
vertically through its centre. In this condition the cylinder is to be
exposed for 144 consecutive hours (six days and nights) to a temperature
ranging from 85° to 90° F. (inclusive), and during such exposure the
cylinder shall not diminish in height by more than one-fourth of its
original height, and the upper cut surface shall retain its flatness and
the sharpness of its edge.

~Exudation Test.~--There shall be no separation from the general mass of
the blasting gelatine or gelatine dynamite of a substance of less
consistency than the bulk of the remaining portion of the material under
any conditions of storage, transport, or use, or when the material is
subjected three times in succession to alternate freezing and thawing, or
when subjected to the liquefaction test before described.

~Picric Acid.~--The material shall contain not more than 0.3 part of
mineral or non-combustible matter in 100 parts by weight of the material
dried at 160° F. It should not contain more than a minute trace of lead.
One hundred parts of the dry material shall not contain more than 0.3 part
of total (free and combined) sulphuric acid, of which not more than 0.1
part shall be free sulphuric acid. Its melting point should be between
248° and 253° F.

~Ammonite, Bellite, Roburite, and Explosives of similar Composition.~--
These are required to stand the same heat test as compressed
nitro-cellulose, gun-cotton, &c.

~Chlorate Mixtures.~--The material must not be too sensitive, and must
show no tendency to increase in sensitiveness in keeping. It must contain
nothing liable to reduce the chlorate. Chlorides calculated as potassium
chloride must not exceed 0.25 per cent. The material must contain no free
acid, or substance liable to produce free acid. Explosives of this class
containing nitro-compounds will be subject to the heat test.

~Page's Regulator.~--The most convenient gas regulator to use in
connection with the heat-test apparatus is the one invented by Prof.
F.J.M. Page, B.Sc.[A] (Fig. 49). It is not affected by variations of the
barometric pressure, and is simple and easy to fit up. It consists of a
thermometer with an elongated glass bulb 5/8 inch diameter and 3 inches
long. The stem of the thermometer is 5 inches long and 1/8 inch to 3/16
inch internal diameter. One and a half inch from the top of the stem is
fused in at right angles a piece of glass tube, 1 inch long, of the same
diameter as the stem, so as to form a T. A piece of glass tube (A), about
7/16 inch external diameter and 1-1/2 inch long, is fitted at one end with
a short, sound cork (C, Fig. 50). Through the centre of this cork a hole
is bored, so that the stem of the thermometer just fits into it. The other
end of this glass tube is closed by a tightly fitting cork, preferably of
indiarubber (I), which is pierced by a fine bradawl through the centre.
Into the hole thus made is forced a piece of fine glass tube (B) 3 inches
long, and small enough to fit loosely inside the stem of the thermometer.

[Footnote A: _Chemical Soc. Jour._, 1876, i. 24.]

The thermometer is filled by pouring in mercury through a small funnel
until the level of the mercury (when the thermometer is at the desired
temperature) is about 1-1/2 inch below the T. The piece of glass tube A,
closed at its upper extremity by the cork I, through which the fine glass
tube B passes into the stem of the thermometer, is now filled by means of
the perforated cork at its lower extremity on the stem of the thermometer.
The gas supply tube is attached to the top of the tube A, the burner to
the T, so that the gas passes in at the top, down the fine tube B, rises
in the space between B and the inside wall of the stem of the thermometer,
and escapes by the T. The regulator is set for any given temperature by
pushing the cork C, and consequently the tubes A and B, which are firmly
attached to it, up or down the stem of the thermometer, until the
regulator just cuts off the gas at the desired temperature.

[Illustration: FIG. 49.--PAGE'S REGULATOR.]

[Illustration: FIG. 50.--PAGE'S GAS REGULATOR, SHOWING BYE-PASS AND
CUT-OFF ARRANGEMENT.]

As soon as the temperature falls, the mercury contracts, and thus opens
the end of the tube B. The gas is thus turned on, and the temperature
rises until the regulator again cuts off the gas. In order to prevent the
possible extinction of the flame by the regulator, the brass tube which
carries the gas to the regulator is connected with the tube which brings
the gas from the regulator to the burner by a small brass tap (Fig. 2).
This tap forms an adjustable bye-pass, and thus a small flame can be kept
burning, even though the regulator be completely shut off. It is obvious
that the quantity of gas supplied through the bye-pass must always be less
than that required to maintain the desired temperature. This regulator,
placed in a beaker of water on a tripod, will maintain the temperature of
the water during four or five hours within 0.2° C., and an air bath during
six weeks within 0.5° C.

To sum up briefly the method of using the regulator:--Being filled with
mercury to about 1\2 inch below the T, attach the gas supply as in diagram
(Fig. 2), the brass tap being open, and the tube B unclosed by the
mercury. Allow the gas to completely expel the air in the apparatus. Push
down the tube A so that the end of B is well under the surface of the
mercury. Turn off the tap of the bye-pass until the smallest bead of flame
is visible. Raise A and B, and allow the temperature to rise until the
desired point is attained. Then push the tubes A and B slowly down until
the flame is just shut off. The regulator will then keep the temperature
at that point.

~Will's Test for Nitro-Cellulose.~--The principle of Dr W. Will's test[A]
may be briefly described as follows:--The regularity with which nitro-
cellulose decomposes under conditions admitting of the removal of the
products of decomposition immediately following their formation is a
measure of its stability. As decomposing agent a sufficiently high
temperature (135° C.) is employed, the explosive being kept in a
constantly changing atmosphere of carbon dioxide, heated to the same
temperature: the oxides of nitrogen which result are swept over red-hot
copper, and are then reduced to nitrogen, and finally, the rates of
evolution of nitrogen are measured and compared. Dr Will considers that
the best definition and test of a stable nitro-cellulose is that it should
give off at a high temperature equal quantities of nitrogen in equal
times. For the purposes of manufacture, it is specially important that the
material should be purified to its limit, i.e., the point at which further
washing produces no further change in its speed of decomposition measured
in the manner described.

[Footnote A: W. Will, _Mitt. a. d. Centrallstelle f. Wissench. Techn.
Untersuchungen Nuo-Babelsberg Berlin_, 1902 [2], 5-24.]

The sample of gun-cotton (2.5 grms.) is packed into the decomposition tube
15 mm. wide and 10 cm. high, and heated by an oil bath to a constant
temperature, the oxides so produced are forced over ignited copper, where
they are reduced, and the nitrogen retained in the measuring tubes. Care
must be taken that the acid decomposition products do not condense in any
portion of the apparatus. The air in the whole apparatus is first
displaced by a stream of carbon dioxide issuing from a carbon dioxide
generator, or gas-holder, and passing through scrubbers, and this stream
of gas is maintained throughout the whole of the experiment, the gas being
absorbed at the end of the system by strong solution of caustic potash. To
guard against the danger of explosions, which occasionally occur, the
decomposition tube and oil bath are surrounded by a large casing with
walls composed of iron plate and strong glass.

Dr Will's apparatus has been modified by Dr Robertson,[A] of the Royal
Gunpowder Factory, Waltham Abbey. The form of the apparatus used by him is
shown in Fig. 51.

~CO_{2} Holders.~--Although objection has been taken to the use of
compressed CO_{2} in steel cylinders on account of the alleged large and
variable amount of air present, it has, nevertheless, been found possible
to obtain this gas with as little as 0.02 per cent. of air. Frequent
estimations of the air present in the CO_{2} of a cylinder show that even
with the commercial article, after the bulk of the CO_{2} has been
removed, the residual gas contains only a very small amount of air, which
decreases in a gradual and perfectly regular manner. For example, one
cylinder which gave 0.03 per cent. of air by volume, after three months'
constant use gave 0.02 per cent. The advantage of using CO_{2} from this
source is obvious when compared with the difficulty of evolving a stream
of gas of constant composition from a Kipps or Finkener apparatus. A
micrometer screw, in addition to the main valve of the CO_{2} cylinder, is
useful for governing the rate of flow. A blank experiment should be made
to ascertain the amount of air in the CO_{2} and the correction made in
the readings afterwards.

[Footnote A: _Jour. Soc. Chem. Ind._, June 30, 1902, p. 819.]

[Illustration: Fig 51.--Will's Apparatus for Testing Nitro-cellulose]

~Measurement of Pressure and Rate of Flow.~--Great attention is paid to
the measurement of the rate of flow of gas, which is arrived at by
counting with a stop-watch the number of bubbles of gas per minute in a
small sulphuric acid wash bottle. A mercury manometer is introduced here,
and is useful for detecting a leak in the apparatus. The rate of flow that
gives the most satisfactory results is 1,000 c.c. per hour. If too rapid
it does not become sufficiently preheated in the glass spiral, and if too
slow there is a more rapid decomposition of the nitro-cellulose by the
oxides of nitrogen which are not removed.

~Decomposition Tube.~--This is of the form and dimensions given by Dr Will
(15 mm. wide and 10 cm. high), the preheating worm being of the thinnest
hydrometer stem tubing. The ground-in exit tube is kept in position by a
small screw clamp with trunnion bearings.

~Bath.~--To permit of two experiments being carried on simultaneously, the
bath is adapted for two decomposition tubes, and is on the principle of
Lothar Meyer's air bath, that is, the bath proper filled with a high-
flashing hydrocarbon oil, and fitted with a lid perforated with two
circular holes for the spiral tubes, is surrounded by an asbestos-covered
envelope, in the interior of which circulate the products of combustion of
numerous small gas jets. The stirrer, agitated by a water motor, or,
better still, a hot-air engine, has a series of helical blades curved to
give a thorough mixing to the oil. Great uniformity and constancy of
temperature are thus obtained. The bath is fitted also with a temperature
regulator and thermometer.

~Reduction Tube~--This is of copper, and consists of two parts, the outer
tube and an inner reaching to nearly the bottom of the former. Into the
inner tube fits a spiral of reduced copper gauze, and into the annular
space between the tubes is fitted a tightly packed reduced copper spiral.
At the bottom the inlet tube dips into a layer of copper oxide asbestos,
on the top of which is a layer of reduced copper asbestos. Through the
indiarubber cork passes a glass tube, which leads the CO_{2} and nitrogen
out of the reduction tube. As the portion of the tube containing the
spirals is heated to redness, water jackets are provided on both inner and
outer tubes to protect the indiarubber cork.

~Nitrogen Measuring Apparatus.~--The measuring tube with zigzag
arrangement is used, having been found very economical in potash. It is
most convenient to take readings by counterbalancing the column of potash
solution and reading off the volume of gas at atmospheric pressure. For
this purpose the tap immediately in front of the measuring tube is
momentarily closed, this having been proved to be without ill effect on
the progress of the test. In all experiments done by this test the air
correction is subtracted from each reading, and the remainder brought to
milligrams of nitrogen with the usual corrections. As objection has
frequently been taken to the test on the ground of difficulty in
interpreting the results obtained, Dr Robertson made a series of
experiments for the purpose of standardising the test, and at the same
time of arriving at the condition under which it could be applied in the
most sensitive and efficient manner. A variety of nitro-celluloses having
been tested, there were chosen as typical, of stable and unstable
products, service gun-cotton on the one hand, and an experimental gun-
cotton, Z, on the other. The first point brought out by these experiments
was the striking uniformity of service gun-cotton, first in regard to the
rectilinear nature of the curve of evolution of nitrogen, and secondly in
regard to the small range within which a large number of results is
included, 15 samples lying between 6.6 and 8.7 mgms. of nitrogen evolved
in four hours. In the case of service gun-cotton, little difference in the
rate of evolution of nitrogen evolved is obtained on altering the rate of
passage of CO_{2} gas through the wide range of 500 c.c. per hour to 2,500
c.c. per hour. With Z gun-cotton (see Fig. 52), however, the case is very
different. Operating at a rate of 1,000 c.c. of CO_{2} per hour, a curve
of nitrogen evolution is obtained, which is bent and forms a good
representation of the inherent instability of the material as proved to
exist from other considerations. Operating at the rate of 1,500 c.c. per
hour, as recommended by Dr Will, the evolution of nitrogen is represented
by a straight line, steeper, however, than that of service gun-cotton. The
rate of passage of CO_{2} was therefore chosen at 1,000 c.c. per hour, or
two-thirds of the rate of Dr Will, and this rate, besides possessing the
advantage claimed of rendering diagnostic the manner of nitrogen evolution
in Z gun-cotton, has in other cases been useful in bringing out
relationships, which the higher rate would have entirely masked.

[Illustration: Fig. 52.--Dr. Robertson's results.]

[Illustration: Fig. 53.--Service Guncotton for Cordite made at a Private
Factory.]

Readings are taken thirty minutes from the time the nitro-cellulose is
heated, and are taken at intervals of fifteen minutes for about four
hours; fresh caustic potash is added every thirty minutes or so. It is
convenient to plot the results in curves. The curves given in Fig. 53 are
from gun-cotton manufacturers in England at a private factory. The rate of
evolution of nitrogen is as follows:--

In 1 hour.  In 2 hours.  In 3 hours.  In 4 hours.
   N.          N.           N.      N. in milligrammes.
  1.25        2.55         4.5           5.75
  1.5         3.25         5.25          6.75
These results are very satisfactory, the gun-cotton was of a very good
quality. Several hours are necessary to remove all the air from the
apparatus. Dr Will stated fifteen minutes in his original paper, but this
has not been found sufficient. It has not been satisfactorily proved that
Will's test can be applied to gelatinised nitro-cellulose powders. It is
convenient to plot the results in curves; the nitrogen is generally given
in cubic centimetres or in milligrammes, and readings taken every fifteen
minutes. The steepness of the curve is a measure of the stability of the
nitro-cellulose which is being examined. The steeper the curve the more
nitrogen is evolved per unit of time, and the less stable the nitro-
cellulose. In the case of unstable nitro-celluloses heated under the
conditions described, the separation of nitrogen is much greater at first
than at a later period. If the nitro-cellulose be very unstable,
explosions are produced. If the separation of nitrogen is uniform during
the prolonged heating, then the nitro-cellulose may be regarded as
"normal." If it be desired to determine the absolute amount of nitrogen
separated from a nitro-cellulose, the following conditions must be
observed:--(1.) Accurate weighing of the nitro-cellulose; (2.)
Determination of the amount of air in the CO_{2}, and deduction of this
from the volume of gas obtained; (3.) Reduction of the volume of the gas
to the volume at 0° C. and 760 mm. pressure.[A]

[Footnote A: See also _Jour. Soc. Chem. Ind._, Dec. 1902, pages 1545-1555,
on the "Stability of Nitro-cellulose" and "Examination of Nitro-
cellulose," Dr Will.]

~Bergrnann and Junk~[A] describe a test for nitro-cellulose that has been
in use in the Prussian testing station for some years. The apparatus
consists of a closed copper bath provided with a condenser and 10
countersunk tubes of 20 cm. length. By boiling amyl-alcohol in the bath,
the tubes can be kept at a constant temperature of 132° C. The explosive
to be tested is placed in a glass tube 35 cm. long and 2 cm. wide, having
a ground neck into which an absorption bulb is fitted. The whole apparatus
is surrounded by a shield, in case of explosion. In carrying out the test,
2 grms. of the explosive are placed in the glass tube and well pressed
down. The absorption bulb is half filled with water, and fitted into the
ground neck of the glass tube, which is then placed in one of the tubes in
the bath previously brought to the boiling point (132° C.). The evolved
oxides of nitrogen are absorbed in the water in the bulb, and at the end
of two hours the tubes are removed from the bath, and on cooling, the
water from the bulb flows back and wets the explosive. The contents of the
tube are filtered and washed, the filtrate is oxidised with permanganate,
and the nitrogen determined as nitric oxide by the Schultze-Tieman method.
The authors conclude that a stable gun-cotton does not evolve more than
2.5 c.c. of nitric oxide per grm. on being heated to 132° C. for two
hours, and a stable collodion-cotton not more than 2 c.c. under the same
conditions. The percentage of moisture in the sample to be tested should
be kept as low as possible. A sample of nitro-cellulose containing 1.97%
of moisture gave an evolution of 2.6 c.c. per grm., while the same sample
with 3.4% moisture gave an evolution of over 50 c.c. per grm. Sodium
carbonate added to an unstable nitro-cellulose diminishes the rate of
decomposition, but if sodium carbonate be intimately mixed with a stable
nitro-cellulose the rate of decomposition will be increased. Calcium
carbonate and mercury chloride have no influence. If an unstable nitro-
cellulose be extracted with alcohol a stable compound is produced. The
percentage solubility of a nitro-cellulose in ether-alcohol rises on
heating to 132° C. A sample which before heating had a solubility of 4.7%
had its solubility increased to 82.5% after six hours' heating.

[Footnote A: _Jour. Soc. Chem. Ind._, xxiii., Oct. 15, 1904, p. 953.]

Mr A.P. Sy (_Jour. Amer. Chem. Soc._, 1903) describes a new stability test
for nitro-cellulose which he terms "The Elastic Limit of Powder Resistance
to Heat." The test consists in heating the powder on a watch glass in an
oven to a temperature of 115° C., after eight hours the watch glass and
powder are weighed and the process repeated daily for six days or less. He
claims that the powder is tested in its natural state, all the products of
decomposition are taken into account, whilst in the old tests only the
acid products are shown, and in the Will test only nitrogen, that it
affords an indication of the effect of small quantities of added
substances or foreign matters on the stability and that it is simple, and
not subject to the variations of the old tests.

Obermüller (_Jour. Soc. Chem. Ind._, April 15, 1905) considers Bergmann
and Junk's test is too complicated and occupies too much time; he proposes
to heat gun-cotton to 140° C. _in vacuo_, and to measure continuously by
means of a mercury manometer the pressure exerted by the evolved gases,
the latter being maintained at constant volume; the rate at which the
pressure increases is a measure of the rate of decomposition of the nitro-
cellulose.

SPECIFIC GRAVITIES OF EXPLOSIVES,  &C.

Nitro-glycerine                 1.6
Gun-cotton (dry)                1.06
    "      (25 per cent. water) 1.32
Dynamite No. 1                  1.62
Blasting gelatine               1.54
Gelatine dynamite               1.55
Ballistite                      1.6
Forcite                         1.51
Tonite                          1.28
Roburite                        1.40
Bellite                         1.2-1.4
Carbo-dynamite                  1.5
Turpin's cast picric acid       1.6
Nitro-mannite                   1.6
Nitro-starch                    1.5
Emmensite                       1.8
Mono-nitro-benzene              1.2
Meta-di-nitro-benzene           1.575 at 18° C.
Ortho-di-nitro-benzene          1.590     "
Para-di-nitro-benzene           1.625     "
British gunpowder, E.X.E.       1.80
   "        "      S.B.C.       1.85
Cannonite (powder)              1.60
Celluloid                       1.35
Cellulose                       1.45
Ammonium nitrate                1.707
Mercury fulminate               4.42

TABLE OF THE TEMPERATURE OF DETONATION.

Blasting gelatine         3220°
Nitro-glycerine           3170°
Dynamite                  2940°
Gun-cotton                2650°
Tonite                    2648°
Picric acid               2620°
Roburite                  2100°
Ammonia nitrate           1130°

RELATIVE SENSITIVENESS TO DETONATION (by Professor C.E. Munroe, U.S. Naval
Torpedo Station).

__________________________________________________________________________
                          |
                          |  Maximum   |
                          |  Distance  |
                          |  at which  |
                          | Detonation |
                          |  occurred. |
                          |     CM.    |
                          |            |
Gun-cotton                |     10     | Nitro-glycerine 86.5 nitro-cotton
                          |            | 9.5, camphor 4 per cent.
Explosive gelatine        |     20     | NH_{4}NO_{3} 5 parts,
(camphorated)             |            | C_{6}H_{4}(N0_{3})_{2} 1 part.
Judson powder, R.R.P.     |     25     |
Emmensite (No. 259)       |     30     |
Rack-a-rock               |     32     | KClO_{3} 79 parts,
                          |            | C_{6}H_{5}(NO)_{2} 21 parts.
Bellite                   |     50     |
Forcite No. 1             |     61     |
Kieselguhr dynamite No. 1 |     64     | 75 per cent. nitro-gycerine.
Atlas powder No. 1        |     74     |
__________________________|____________|_________________________



CHAPTER IX.

_DETERMINATION OF THE RELATIVE STRENGTH OF EXPLOSIVES._

Effectiveness of an Explosive--High and Low Explosives--Theoretical
Efficiency--MM. Roux and Sarrau's Results--Abel and Noble's--Nobel's
Ballistic Test--The Mortar, Pressure, or Crusher Gauge--Lead Cylinders--
The Foot-Pounds Machine--Noble's Pressure Gauge--Lieutenant Walke's
Results--Calculation of Pressure Developed by Dynamite and Gun-Cotton--
Macnab's and Ristori's Results of Heat Developed by the Explosion of
Various Explosives--Composition of some of the Explosives in Common Use
for Blasting, &c.


~The Determination of the Relative Strength of Explosives.~--Explosives
may be roughly divided into two divisions, viz., those which when exploded
produce a shattering force, and those which produce a propulsive force.
Explosives of the first class are generally known as the high explosives,
and consist for the most part of nitro compounds, or mixtures of nitro
compounds with other substances. Any explosive whose detonation is very
rapid is a high explosive, but the term has chiefly been applied to the
nitro-explosives.

The effectiveness of an explosive depends upon the volume and temperature
of the gases formed, and upon the rapidity of the explosion. In the high
explosives the chemical transformation is very rapid, hence they exert a
crushing of shattering effect. Gunpowder, on the other hand, is a low
explosive, and produces a propelling or heaving effect.

The maximum work that an explosive is capable of producing is
proportionate to the amount of heat disengaged during its chemical
transformation. This may be expressed in kilogrammetres by the formula
425Q, where Q is the number of units of heat evolved. The theoretical
efficiency of an explosive cannot, however, be expected in practice for
many reasons.

In the case of blasting rock, for instance:[A]--1. Incomplete combustion
of the explosive. 2. Compression and chemical changes induced in the
surrounding material operated on. 3. Energy expended in the cracking and
heating of the material which is not displaced. 4. The escape of gas
through the blast-hole, and the fissures caused by the explosion. The
proportion of useful work has been estimated to be from 14 to 33 per cent.
of the theoretical maximum potential.

[Footnote A: C.N. Hake, Government Inspector of Explosives, Victoria,
_Jour. Soc. Chem. Ind._, 1889.]

For the purposes of comparison, manufacturers generally rely more upon the
practical than the theoretical efficiency of an explosive. These, however,
stand in the same relation to one another, as the following table of
Messrs Roux and Sarrau will show:--

MECHANICAL EQUIVALENT OF EXPLOSIVES.

                                                Theoretical Work  Relative
                                                    in Kilos.      Value.

Blasting powder (62 per cent. KNO_{3})               242,335        1.0
Dynamite (75 per cent. nitro-glycerine)              548,250        2.26
Blasting gelatine (92 per cent. nitro-glycerine)     766,813        3.16
Nitro-glycerine                                      794,563        3.28

Experiments made in lead cylinders give--
  Dynamite                                                          1.0
  Blasting gelatine                                                 1.4
  Nitro-glycerine                                                   1.4

Sir Frederick Abel and Captain W.H. Noble, R.A., have shown that the
maximum pressure exerted by gunpowder is equal to 486 foot-tons per lb. of
powder, or that when 1 kilo, of the powder gases occupy the volume of 1
litre, the pressure is equal to 6,400 atmospheres; and Berthelot has
calculated that every gramme of nitro-glycerine exploded gives 1,320 units
of heat. MM. Roux and Sarrau, of the Depôt Centrales des Poudres, Paris,
by means of calorimetric determinations, have shown that the following
units of heat are produced by the detonation of--

Nitro-glycerine  1,784 heat units.
Gun-cotton       1,123      "
Potassic picrate   840      "

which, multiplied by the mechanical equivalent  per unit, gives--

Nitro-glycerine    778 metre tons per kilogramme.
Gun-cotton         489       "            "
Picrate of potash  366       "            "

~Nobel's Ballistic Test.~--Alfred Nobel was the first to make use of the
mortar test to measure the (ballistic) power of explosives. The use of the
mortar for measuring the relative power of explosives does not give very
accurate results, but at the same time the information obtained is of
considerable value from a practical point of view. The mortar consists of
a solid cylinder of cast iron, one end of which has been bored to a depth
of 9 inches, the diameter of the bore being 4 inches. At the bottom of the
bore-hole is a steel disc 3 inches thick, in which another hole has been
bored 3 inches by 2 inches. The mortar (Fig. 54) itself is fitted with
trunnions, and firmly fixed in a very solid wooden carriage, which is
securely bolted down to the ground. The shot used should weigh 28 lbs.,
and be turned accurately to fit the bore of the mortar. Down its centre is
a hole through which the fuse is put.

The following is the method of making an experiment:--A piece of hard wood
is turned in the lathe to exactly fit the hole in the steel disc at the
bottom of the bore. This wooden cylinder itself contains a small cavity
into which the explosive is put. Ten grms. is a very convenient quantity.
Before placing in the mortar, a hole may be made in the explosive by means
of a piece of glass rod of such a size that the detonator to be used will
just fit into it. After placing the wooden cylinder containing the
explosive in the cavity at the bottom of the bore, the shot, slightly
oiled, is allowed to fall gently down on to it. A piece of fuse about a
foot long, and fitted with a detonator, is now pushed through the hole in
the centre of the shot until the detonator is embedded in the explosive.
The fuse is now lighted, and the distance to which the shot is thrown is
carefully measured. The range should be marked out with pegs into yards
and fractions of yards, especially at the end opposite to the mortar. The
mortar should be inclined at an angle of 45°. In experimenting with this
apparatus, the force and direction of the wind will be found to have
considerable influence.

[Illustration: FIG. 54.--MORTAR FOR MEASURING THE BALLISTIC POWER OF
EXPLOSIVES. _A_, Shot; _B_, Steel Disc; _C_, Section of Mortar (Cast
Iron); _D_, Wooden Plug holding Explosive (_E_); _F_, Fuse.]

Mr T. Johnson made some ballistic tests. He used a steel mortar and a shot
weighing 29 Ibs., and he adopted the plan of measuring the distance to
which a given charge, 5 grms., would throw the shot. He obtained the
following results:--

                                                           Range in Feet.

Blasting gelatine (90 per cent. nitro-glycerine and nitro-cellulose)  392
Ammonite (60 per cent. Am(NO_{3}) and 10 per cent. nitro-naphthalene) 310
Gelignite (60 per cent. nitro-gelatine and gun-cotton)                306
Roburite (AmNO_{3} and chloro-nitro-benzol)                           294
No. 1 dynamite (75 per cent. nitro-gelatine)                          264
Stonite (68 per cent. nitro-gelatine and 32 per cent. wood-meal)      253
Gun-cotton                                                            234
Tonite (gun-cotton and nitrates)                                      223
Carbonite (25 per cent. nitro-gelatine, 40 per cent. wood-meal,
  and 30 per cent. nitrates)                                          198
Securite (KNO_{3} and nitro-benzol)                                   183
Gunpowder                                                             143

~Calculation of the Volume of Gas Evolved in an Explosive Reaction.~--The
volume of gas evolved in an explosive reaction may be calculated, but only
when they are simple and stable products, such calculations being made at
0° and 760 mm. Let it be required, for example, to determine the volume of
gas evolved by 1 gram-molecule of nitro-glycerine. The explosive reaction
of nitro-glycerine may be represented by the equation.

C_{3}H_{5}O_{3}(NO_{2})_{3} = 3CO_{2} + 2-1/2H_{2}O + 1-1/2N_{2} + 1/4O_{2}
By weight       227         =  132    +   45        +   42       +    8
By volume         2         =    3    +    2-1/2    +    1-1/2   +    1/4

The weights of the several products of the above reactions are calculated
by multiplying their specific gravities by the weight of 1 litre of
hydrogen at 0° C. and 760 mm. (0.0896 grm). Thus,

One litre of CO_{2} = 22 x .0896 = 1.9712 grm.
     "       H_{2}O =  9 x    "  = 0.8064  "
     "       N_{2}  = 14 x    "  = 1.2544  "
     "       O_{2}  = 16 x    "  = 1.4336  "

The volume of permanent gases at 0° and 760 mm. is constant, and assuming
the gramme as the unit of mass, is found to be 22.32 litres. Thus:--

Volume of 44 of CO_{2}, at 0° and 760 mm. =  44/1.9712 = 22.32 litres.
          18 "  H_{2}O        "      "    =  18/0.8044 = 22.32    "
          28 "  N_{2}         "      "    =  28/1.2544 = 22.32    "
          32 "  O_{2}         "      "    =  32/1.4366 = 22.32    "

Therefore

132 grms. of CO_{2} at 0° C and 760 mm. = 22.32 x 3     =  66.96 litres.
 45    "     H_{2}O       "      "      = 22.32 x 2-1/2 =  55.80   "
 42    "     N_{2}        "      "      = 22.32 x 1-1/2 =  33.48   "
  8    "     O_{2}        "      "      = 22.32 x 1/4   =   5.58   "
                                                        ____________

                                                          161.82   "
Therefore 1 gram-molecule or 227 grms. of nitro-glycerine when exploded,
produces 161.82 litres of gas at 0° C and 760 mm.

To determine the volume of gas at the temperature of explosion, we simply
apply the law of Charles.[A] Thus--

V : V' :: T : T' or V' = VT'/T

in which V represents the original volume.
         V'       "       new volume.
         T        "       original temperature on the absolute scale.
         T'       "       new temperature of the same scale
In the present case T' = 6001°.

Therefore substituting, we have

V' = 161.82x6001/273 = 3557 litres

or at the temperature of explosion 1 gram-molecule of nitro-glycerine
produces 3,557 litres of permanent gas.

[Footnote A: According to the law of Charles, the volume of any gas varies
directly as its temperature on the absolute scale, provided the pressure
remains constant. Knowing the temperature on the centigrade scale, the
corresponding temperature on the absolute scale is obtained by adding 273
to the degrees centigrade.]

~Pressure or Crusher Gauge.~--There are many forms of this instrument. As
long ago as 1792 Count Rumford used a pressure gauge. The so-called
crusher gauge was, however, first used by Captain Sir Andrew Noble in his
researches on powder. Other forms are the Rodman[A] punch Uchatius
Eprouvette, and the crusher gauge of the English Commission on Explosives.
They are all based either upon the size of an indent made upon a copper
disc by a steel punch fitted to a piston, acted upon by the gases of the
explosive, or upon the crushing or flattening of copper or lead cylinders.

[Footnote A: Invented by General Rodman, United States Engineers.]

[Illustration: FIG. 55.--PRESSURE GAUGE.]

Berthelot uses a cylinder of copper, as also did the English Commission,
but in the simpler form of apparatus mostly used by manufacturers lead
cylinders are used. This form of apparatus (Fig. 55) consists of a base of
iron to which four uprights _a_ are fixed, set round the circumference of
a 4-inch circle; the lead plug rests upon the steel base let into the
solid iron block. A ring _c_ holds the uprights _d_ together at the top.
The piston _b_, which rests upon the lead plug, is a cylinder of tempered
steel 4 inches in diameter and 5 inches in length; it is turned away at
the sides to lighten it as much as possible. It should move freely between
the uprights _d_. In the top of this cylinder is a cavity to hold the
charge of explosive. The weight of this piston is 12-1/4 lbs. The shot _e_
is of tempered steel, and 4 inches in diameter and 10 inches in length,
and weighs 34-1/2 lbs. It is bored through its axis to receive a capped
fuse.

The instrument is used in the following manner:--A plug of lead 1 inch
long and 1 inch in diameter, and of a cylindrical form, is placed upon the
steel plate between the uprights _a_, the piston placed upon it, the
carefully weighed explosive placed in the cavity, and the shot lowered
gently upon the piston. A piece of fuse, with a detonator fixed at one
end, is then pushed through the hole in the shot until it reaches the
explosive contained in the cavity in the piston. The fuse is lighted. When
the charge is exploded, the shot is thrown out, and the lead cylinder is
more or less compressed. The lead plugs must be of a uniform density and
homogeneous structure, and should be cut from lead rods that have been
drawn, and not cast separately from small masses of metal.

[Illustration: FIG. 56.--_b_, STEEL PUNCH; _c_, LEAD CYLINDER FOR USE WITH
PRESSURE GAUGE.]

The strength of the explosive is proportional to the work performed in
reducing the height of the lead (or copper) plug, and to get an expression
for the work done it is necessary to find the number of foot-pounds (or
kilogrammetres) required to produce the different amounts of compression.
This is done by submitting exactly similar cylinders of lead to a crushing
under weights acting without initial velocity, and measuring the reduced
heights of the cylinders; from these results a table is constructed
establishing empirical relations between the reduced heights and the
corresponding weights; the cylinders are measured both before and after
insertion in the pressure gauge by means of an instrument known as the
micrometer calipers (Fig. 57).[A]

[Footnote A: An instrument called a "Foot-pounds Machine" has been
invented by Lieut. Quinan, U.S. Army. It consists of three boards,
connected so as to form a slide 16 feet high, in which a weight (the shot
of the pressure gauge) can fall freely. One of the boards is graduated
into feet and half feet. The horizontal board at the bottom, upon which
the others are nailed, rests upon a heavy post set deep in the ground,
upon which is placed the piston of the gauge, which in this case serves as
an anvil on which to place the lead cylinders. The shot is raised by means
of a pulley, fixed at the top of the structure, to any desired height, and
let go by releasing the clutch that holds it. The difference between the
original length and the reduced length gives the compression caused by the
blow of the shot in falling, and gives the value in foot-pounds required
to produce the different amounts of compression. (Vide _Jour. U.S. Naval
Inst._, 1892.)]

[Illustration: FIG. 57.--MICROMETER CALIPERS FOR MEASURING DIAMETER OF
LEAD CYLINDERS.]

~The Use of Lead Cylinders.~--The method of using lead cylinders to test
the strength of an explosive is a very simple affair, and is conducted as
follows:--A solid cast lead cylinder, of any convenient size, is bored
down the centre for some inches, generally until the bore-hole reaches to
about the centre of the block. The volume of this hole is then accurately
measured by pouring water into it from a graduated measure, and its
capacity in cubic centimetres noted. The bore-hole is then emptied and
dried, and a weighed quantity (say 10 grms.) of the explosive pressed well
down to the bottom of the hole. A hole is then made in the explosive (if
dynamite) with a piece of clean and rounded glass rod, large enough to
take the detonator. A piece of fuse, fitted with a detonator, is then
inserted into the explosive and lighted. After the explosion a large pear-
shaped cavity will be found to have been formed, the volume of which is
then measured in the same way as before.

The results thus obtained are only relative, but are of considerable value
for comparing dynamites among themselves (or gun-cottons). Experiments in
lead cylinders gave the relative values for nitro-glycerine 1.4, blasting
gelatine 1.4, and dynamite 1.0. (Fig. 58 shows sections of lead cylinders
before and after use.)

[Illustration: FIG. 58.--LEAD CYLINDERS BEFORE AND AFTER USE.]

Standard regulations for the preparation of lead cylinders may be found in
the _Chem. Zeit._, 1903, 27 [74], 898. They were drawn up by the Fifth
International Congress of App. Chem., Berlin. The cylinder of lead should
be 200 mm. in height and 200 mm. in diameter. In its axis is a bore-hole,
125 mm. deep and 25 mm. in diameter. The lead used must be pure and soft,
and the cylinder used in a series of tests must be cast from the same
melt. The temperature of the cylinders should be 15° to 20° throughout.
Ten grms. of explosive should be used and wrapped in tin-foil. A detonator
with a charge of 2 grms., to be fired electrically, is placed in the midst
of the explosive. The cartridge is placed in the bore-hole, and gently
pressed against the bottom, the firing wires being kept in central
position. The bore-hole is then filled with dry quartz sand, which must
pass through a sieve of 144 meshes to the sq. cm., the wires being .35 mm.
diameter. The sand is filled in evenly, any excess being levelled off. The
charge thus prepared is then fired electrically. The lead cylinder is then
inverted, and any residues removed with a brush. The number of c.c. of
water required to fill the cavity, in excess of the original volume of the
bore-hole, is a measure of the strength of the explosive. The results are
only comparable if made with the same class of explosive. A result is to
be the mean of at least three experiments. The accuracy of the method
depends on (_a_) the uniform temperature of the lead cylinder (15° to 20°
C. 7); (_b_) on the uniformity of the quartz sand; (_c_) on the uniformity
of the measurements.

[Illustration: FIG. 59.--NOBLE'S PRESSURE GAUGE.]

~Noble's Pressure Gauge.~--The original explosive vessels used by Captain
Sir A. Noble in his first experiments were practically exactly similar to
those that he now employs, which consists of a steel barrel A (Fig. 59),
open at both ends, which are closed by carefully fitted screw plugs,
furnished with steel gas checks to prevent any escape past the screw. The
action of the gas checks is exactly the same as the leathers used in
hydraulic presses. The pressure of the gas acting on both sides of the
annular space presses these sides firmly against the cylinder and against
the plug, and so effectually prevents any escape. In the firing plug F is
a conical hole closed by a cone fitting with great exactness, which, when
the vessel is prepared for firing, is covered with fine tissue paper to
act as an insulator. The two firing wires GG, one in the insulated cone,
the other in the firing plug, are connected by a very fine platinum wire
passing through a glass tube filled with meal powder. The wire becomes
red-hot when connection is made with a Leclanché battery, and the charge
which has previously been inserted into the vessel is fired. The crusher
plug is fitted with a crusher gauge H for determining the pressure of the
gases at the moment of explosion, and in addition there is frequently a
second crusher gauge apparatus screwed into the cylinder. When it is
desired to allow the gases to escape for examination, the screw J is
slightly withdrawn. The gases then pass into the passage I, and can be led
to suitable apparatus in which their volume can be measured, or in which
they can be sealed for subsequent chemical analysis.

The greatest care must be exercised in carrying out experiments with this
apparatus; it is particularly necessary to be sure that all the joints are
perfectly tight before exploding the charge. Should this not be the case,
the gases upon their generation will cut their way out, or completely blow
out the part improperly secured, in either case destroying the apparatus.
The effect produced upon the apparatus when the gas has escaped by cutting
a passage for itself is very curious. The surface of the metal where the
escape occurred presents the appearance of having been washed away in a
state of fusion by the rush of the highly heated products.

~The Pressure Gauge.~--The pressure is found by the use of a little
instrument known as the pressure gauge which consists of a small chamber
formed of steel, inside of which is a copper cylinder, and the entrance
being closed by a screw gland, in which a piston, having a definite
sectional area, works. There is a gas check E (Fig. 60) placed in the
gland, and over the piston, which prevents the admission of gas to the
chamber. When it is desired to find the pressure in the chamber of a gun,
one or more of these crushers are made up with or inserted at the extreme
rear end of the cartridge, in order to avoid their being blown out of the
gun when fired. This, however, often takes place, in which case the gauges
are usually found a few yards in front of the muzzle. The copper cylinders
which register the pressure are made 0.5 inch long from specially selected
copper, the diameters being regulated to give a sectional area of either
1/12 or 1/24 square inch.

[Illustration: FIG. 60.--CRUSHER GAUGE. _E_, GAS CHECK.]

Hollow copper cylinders are manufactured with reduced sectional areas for
measuring very small pressures. It has been found that these copper
cylinders are compressed to definite lengths for certain pressures with
remarkable uniformity. Thus a copper cylinder having a sectional area of
1/12 square inch, and originally 1/2 inch long, is crushed to a length of
0.42 inch by a pressure of 10 tons per square inch. By subsequently
applying a pressure of 12 tons per square inch the cylinder is reduced to
a length of 0.393 inch. Before using the cylinders, whether for
experimenting with closed vessels or with guns, it is advisable to first
crush them by a pressure a little under that expected in the experiment.
Captain Sir A. Noble used in his experiments a modification of Rodman's
gauge. (Ordnance Dept., U.S.A., 1861.)

~By Calculation.~--To calculate the pressure developed by the explosion of
dynamite in a bore-hole 3 centimetres in diameter, charged with 1
kilogramme of 75 per cent. dynamite, Messrs Vieille and Sarrau employ the
following formula:--

P = V_{o}(1 + Q/273._c_)/(V - _v_).

Where V_{o} = the volume (reduced to 0° and 760 mm.) of the gases produced
by a unit of weight of the explosive; Q the number of calories disengaged
by a unit of weight of the explosive; _c_ equals the specific heat at
constant volume of the gases; V the volume in cubic centimetres of a unit
of weight of the explosive; _v_ the volume occupied by the inert
materials of the explosive. The volume of gas produced by the explosion of
1 kilogramme of nitro-glycerine (at 0° and 760 mm.) is 467 litres.

V_{o} will therefore equal 0.75 x 467 = 350.25.

The specific heat _c_ is, according to Sarrau, .220 (_c_); and according
to Bunsen, 1 kilogramme of dynamite No. 1 disengages 1,290 (Q) calories.
The density of dynamite is equal to 1.5, therefore

V = 1/1.5 = .666.

If we take the volume of the kieselguhr as .1, we find from above formula
that

P = 350(1 + 1290/(273 x .222))/(.600 - .1) = 13,900 atmospheres,

which is equal to 14,317 kilogrammes per square centimetre. The pressure
developed by 1 kilogramme of pure nitro-glycerine equals 18,533
atmospheres, equals 19,151 kilogrammes. Applying this formula to gun-
cotton, and taking after Berthelot, Q = 1075, and after Vieille and
Sarrau, V_{o} = 671 litres, and _c_ as .2314, and the density of the
nitro-cellulose as 1.5, we have (V = O)

P = 671(1 + 1075/(273 x .2314))/.666 = 18,135 atmospheres.

To convert this into pressure of kilogrammes per square centimetre, it is
necessary to multiply it by the weight of a column of mercury 0.760 m.
high, and 1 square centimetre in section, which is equal to increasing it
by 1/30. It thus becomes

P^{k} = (1 + 1/30).

P^{k} = 18,135 x 1.033 = 18,733 kilogrammes.

The following tables, taken from Messrs William Macnab's and E. Ristori's
paper (_Proc. Roy. Soc._, 56, 8-19), "Researches on Modern Explosives,"
are very interesting. They record the results of a large number of
experiments made to determine the amount of heat evolved, and the quantity
and composition of the gases produced when certain explosives and various
smokeless powders were fired in a closed vessel from which the air had
been previously exhausted. The explosions were carried out in a
"calorimetric bomb" of Berthelot's pattern.[A]

[Footnote A: For description of "bomb," see "Explosives and their Power,"
Berthelot, trans. by Hake and Macnab, p. 150. (Murray.)]

Table Showing Quantity of Heat and Volume and Analysis of Gas Developed
per Gramme with Different Sporting and Military Smokeless Powders Now In
Use

______________________________________________________________________
                      |          |           |         |              |
 Name of Explosive.   | Calories | Permanent | Aqueous | Total Volume |
                      | per grm. |  Gases.   | Vapour. | of Gas at 0° |
                      |          |           |         |  and 760 mm. |
______________________|__________|___________|_________|______________|
                      |          |  cc/grm   | cc/grm  |    cc/grm    |
 E.C. powder, English |    800   |    420    |   154   |     574      |
 S.S. powder          |    799   |    584    |   150   |     734      |
 Troisdorf, German    |    943   |    700    |   195   |     895      |
 Rifleite, English    |    864   |    766    |   159   |     925      |
 B.N., French         |    833   |    738    |   168   |     906      |
 Cordite, English     |   1253   |    647    |   235   |     882      |
 Ballistite, German   |   1291   |    591    |   231   |     822      |
 Ballistite, Italian  |   1317   |    58l    |   245   |     826      |
   and Spanish        |          |           |         |              |
______________________|__________|___________|_________|______________|

The figures in column headed "Co-efficient of Potential Energy" serve as a
measure of comparison of the power of the explosives, and are the products
of the number of calories by the volume of gas, the last three figures
being suppressed in order to simplify the results.

The amounts of water found were calculated for comparison as volumes of
H_{2}O gas at 0° and 760 mm.

E.C. powder consists principally of nitro-cellulose mixed with barium
nitrate and a small proportion of camphor.

S.S. of nitro-lignine mixed with barium nitrate and nitro-benzene.

Troisdorf powder is gelatinised nitro-cellulose; rifleite gelatinised
nitro-cellulose and nitro-benzene.

Cordite contains 58 per cent. nitro-glycerine, 37 per cent. gun-cotton,
and 5 per cent. vaseline.

Ballistite (Italian) consists of equal parts nitro-cellulose and nitro-
glycerine, and 1/2 per cent. of aniline. The German contains a higher
percentage of nitro-cellulose.

TABLE SHOWING THE HEAT DEVELOPED BY EXPLOSIVES CONTAINING NITRO-GLYCERINE
AND NITRO-CELLULOSE IN DIFFERENT PROPORTIONS.

______________________________________________________________________
         Composition of Explosives.          |    Calories per cent.
_____________________________________________|________________________
Nitro-cellulose           |                  |
(N = 13.3 per cent.).     | Nitro-glycerine. |
                          |                  |
100 per cent. dry pulp    |      0           |           1061
100      "    gelatinised |      0           |            922
 90      "                |     10 per cent. |           1044
 80      "                |     20     "     |           1159
 70      "                |     30     "     |           1267
 60      "                |     40     "     |           1347
 50      "                |     50     "     |           1410
 40      "                |     60     "     |           1467
  0      "                |    100     "     |           1652
__________________________|__________________|________________________
                          |                  |
Nitro-cellulose           |                  |
(N=12.24 per cent.)       | Nitro-glycerine. |
                          |                  |
 80 per cent.             |     20 per cent. |           1062
 60       "               |     40     "     |           1288
 50       "               |     50     "     |           1349
 40       "               |     60     "     |           1405
                          |                  |
__________________________|__________________|________________________|
Nitro-cellulose           |                  |
(N = 13.3 per cent.).     | Nitro-glycerine. |       Vaseline.
                          |                  |
 55 per cent.             |     40 per cent. |    5 per cent.  1134
 35       "               |     60     "     |    5     "      1280
__________________________|__________________|________________________

TABLE OF RESULTS OBTAINED BY LIEUT. W. WALKE., OF THE ARTILLERY, U.S.A,
WITH QUINAN'S PRESSURE GAUGE.

Nitro-glycerine being taken as 100. (From _U.S. Naval Inst. Jour._)

__________________________________________________________________________
                         |             |           |
                         | Compression | Order of  |
   Name of Explosive.    |  of Lead    | Strength. |
                         |             |           |
                         |    Inch.    |           |
Explosive gelatine       |    0.585    |  106.17   |
Hellhoffite              |    0.585    |  106.17   |
Nitro-glycerine          |    0.551    |  100.00   | Standard, N.G.
Nobel's smokeless powder |    0.509    |   92.38   |
Nitro-glycerine          |    0.509    |   92.37   |
Gun-cotton               |    0.458    |   83.12   | U.S. naval torpedo
                         |             |           | gun-cotton
Gun-cotton               |    0.458    |   83.12   | Stowmarket.
Nitro-glycerine          |    0.451    |   81.85   | Vouges, N.G.
Gun-cotton               |    0.448    |   81.31   |
Dynamite No. 1           |    0.448    |   81.31   |
Dynamite de Traul        |    0.437    |   79.31   |
Emmensite                |    0.429    |   77.86   |
Amide powder             |    0.385    |   69.87   |
Oxonite                  |    0.383    |   69.51   |
Tonite                   |    0.376    |   68.24   | G.C. 52.5%, and
                         |             |           | Ba(NO_{3})_{2}, 47.5%
Bellite                  |    0.362    |   65.70   |
Rack-a-rock              |    0.340    |   61.71   |
Atlas powder             |    0.333    |   60.43   |
Ammonia dynamite         |    0.332    |   60.25   |
Volney's powder No. 1    |    0.322    |   58.44   | Nitrated naphthalene.
      "         No. 2    |    0.294    |   53.18   |    "         "
Melinite                 |    0.280    |   50.82   | Picric acid 70%, and
                         |             |           | sol. nitro-cotton 30%.
Silver fulminate         |    0.277    |   50.27   |
Mercury                  |    0.275    |   49.91   |
Mortar powder            |    0.155    |   28.13   |
_________________________|_____________|___________|______________________

~Composition of some of the Explosives in Common Use.~

~Ordinary Dynamite.~

Nitro-Glycerine 75 per cent.
Kieselguhr      25    "

~Amvis.~

Nitrate of Ammonia      90 per cent.
Chloro-di-nitro Benzene  5    "
Wood Pulp                5    "

~Ammonia Nitrate Powder.~

Nitrate of Ammonia 80 per cent.
Chlorate of Potash  5    "
Nitro-Glucose      10    "
Coal Tar            5    "

~Celtite.~

Nitro-Glycerine   56-59  parts.
Nitro-Cotton       2-3.5   "
KNO_{3}           17-21    "
Wood Meal          8-9     "
Ammonium Oxalate  11-13    "
Moisture         0.5-1.5   "

~Atlas Powders.~

Sodium Nitrate       2.0  per cent.
Nitro-Glycerine     75.0     "
Wood Pulp           21.0     "
Magnesium Carbonate  2.0     "

~Dauline.~

Nitro-Glycerine   50 per cent.
Sawdust           30    "
Nitrate of Potash 20    "

~Vulcan Powder.~

Nitro-Glycerine  30   per cent.
Nitrate of Soda  52.5    "
Sulphur           7.0    "
Charcoal         10.5    "

~Vigorite.~

Nitro-Glycerine  30 per cent.
Nitrate of Soda  60    "
Charcoal          5    "
Sawdust           5    "

~Rendrock.~

Nitrate of Potash  40 per cent.
Nitro-Glycerine    40    "
Wood Pulp          13    "
Paraffin or Pitch   7    "

~Ammonia Nitrate Powder.~

Ammonia Nitrate    80 per cent.
Potassium Chlorate  5    "
Nitro-Glucose      10    "
Coal Tar            5    "

~Hercules Powders.~

Nitro-Glycerine       75    to 40     per cent.
Sugar                  1    "  15.66     "
Chlorate of Potash     1.05 "   3.34     "
Nitrate of Potash      2.10 "  31.00     "
Carbonate of Magnesia 20.85 "  10.00     "

~Carbo-Dynamite.~

Nitro-Glycerine  90 per cent.
Charcoal         10    "

~Geloxite (Permitted List).~

Nitro-Glycerine   64-54 parts.
Nitro-Cotton       5-4    "
Nitrate of Potash 22-13   "
Ammonium Oxalate  15-12   "
Red Ochre          1-0    "
Wood Meal          7-4    "

The Wood Meal to contain not more than 15% and not less than 5% moisture.

~Giant Powder.~

Nitro-Glycerine  40 per cent.
Sodium Nitrate   40    "
Rosin             6    "
Sulphur           6    "
Guhr              8    "

~Dynamite de Trauzel.~

Nitro-Glycerine  75 parts.
Gun-Cotton       25   "
Charcoal          2   "

~Rhenish Dynamite.~

Solution of N.G. in Naphthalene  75 per cent.
Chalk, or Barium Sulphate         2    "
Kieselguhr                       23    "

~Ammonia Dynamite.~

Ammonia Nitrate  75 parts.
Paraffin          4   "
Charcoal          3   "
Nitro-Glycerine  18   "

~Blasting Gelatine.~

Nitro-Glycerine    93   per cent.
Nitro-Cotton     3 to 7    "

~Gelatine Dynamite.~

Nitro-Glycerine    71 per cent.
Nitro-Cotton        6    "
Wood Pulp           5    "
Potassium Nitrate  18    "

~Gelignite.~

Nitro-Glycerine  60 to 61 per cent.
Nitro-Cotton      4 "   5    "
Wood Pulp         9 "   7    "
Potassium Nitrate      27    "

~Forcite.~

Nitro-Glycerine   49   per cent.
Nitro-Cotton       1.0    "
Sulphur            1.5    "
Tar               10.0    "
Sodium Nitrate    38.0    "
Wood Pulp          5      "
 (The N.-G., &c., varies.)

~Tonite No. 1.~

Gun-Cotton     52-50 per cent.
Barium Nitrate 47-40    "

~Tonite No. 2.~

Contains Charcoal also.

~Tonite No. 3.~

Gun-Cotton      18   to 20  per cent.
Ba(NO_3)_2      70   "  67     "
Di-nitro-Benzol 11   "  13     "
Moisture         0.5 "   1     "

~Carbonite.~

Nitro-Glycerine   17.76 per cent.
Nitro-Benzene      1.70    "
Soda               0.42    "
KNO_3             34.22    "
Ba(NO_3)_2         9.71    "
Cellulose          1.55    "
Cane Sugar        34.27    "
Moisture           0.36    "
                ________

                  99.99

~Roburite.~

Ammonium Nitrate       86  per cent.
Chloro-di-nitro-Benzol 14     "

~Faversham Powder.~

Ammonium Nitrate                      85  per cent.
Di-nitro-Benzol                       10     "
Trench's Flame-extinguishing Compound  5     "

~Favierite No. 1.~

Ammonium Nitrate     88  per cent.
Di-nitro-Naphthalene 12     "

~Favierite No. 2.~

No. 1 Powder    90  per cent.
Ammon. Chloride 10     "

~Bellite.~

Ammonium Nitrate     5 parts.
Meta-di-nitro-Benzol 1   "

~Petrofacteur.~

Nitro-Benzene        10  per cent.
Chlorate of Potash   67     "
Nitrate of Potash    20     "
Sulphide of Antimony  3     "

~Securite.~

Mixtures of Meta-di-nitro-Benzol 26  per cent.
and Nitrate of Ammonia           74     "

~Rack-a-Rock.~

Potassium Chlorate 79 parts.
Mono-nitro-Benzene 21   "

~Oxonite.~

Nitric Acid (sp. gr. 1.5) 54 parts.
Picric Acid               46   "

~Emmensite.~

Emmens Acid      5 parts.
Ammonium Nitrate 5   "
Picric Acid      6   "

~Brugère Powder.~

Ammonium Picrate  54  per cent.
Nitrate of Potash 46     "

~Designolle's Torpedo Powders.~

Potassium Picrate 55 to 50  per cent.
Nitrate of Potash 45 "  50     "

~Stowite.~

Nitro-Glycerine    58   to 61 parts.
Nitro-Cotton        4.5 "   5   "
Potassium Nitrate  18   "  20   "
Wood Meal           6   "   7   "
Oxalate of Ammonia 11   "  15   "

The Wood Meal shall contain not more than 15% and not less than 5% by
weight of moisture. The explosive shall be used only when contained
in a non-water-proofed wrapper of parchment--No. 6 detonator.

~Faversham Powder.~

Nitrate of Ammonium 93 to 87
Tri-nitro-Toluol    11 "   9
Moisture             1 "  --

~Kynite.~

Nitro-Glycerine   24-26  parts.
Wood-Pulp        2.5-3.5   "
Starch          32.5-3.5   "
Barium Nitrate  31.5-34.5  "
CaCO_{3}           0-0.5   "
Moisture         3.0-6.0   "

Must be put up only in water-proof parchment paper, and No. 6 electric
detonator used.

~Rexite.~

Nitro-Glycerine    6.5-8.5  parts.
Ammonium Nitrate    64-68     "
Sodium Nitrate      13-16     "
Tri-nitro-Tolulene 6.5-8.5    "
Wood Meal            3-5      "
Moisture            .5-1.4    "

Must be contained in water-proof case (stout paper), water-proofed with
Resin and Cerasin--No. 6 detonator.

~Withnell Powder.~

Ammonium Nitrate         88-92 parts.
Tri-nitro-Toluene         4-6    "
Flour (dried at 100° C.)  4-6    "
Moisture                  0-15   "

Only to be used when contained in a linen paper cartridge, water-proofed
with Carnuba Wax, Parrafin--No. 7 detonator used.

~Phenix Powder.~

Nitro-Glycerine   28-31 parts.
Nitro-Cotton       0-1    "
Potassium Nitrate 30-34   "
Wood Meal         33-37   "
Moisture           2-6    "

~SMOKELESS  POWDERS.~

~Cordite.~

Nitro-Glycerine 58  per cent. +or- .75
Nitro-Cotton    37     "      +or- .65
Vaseline         5     "      +or- .25

~Cordite, M.D.~

Nitro-Glycerine 30  per cent. +or- 1
Nitro-Cotton    65     "      +or- 1
Vaseline         5     "      +or-  .25

Analysis of--
  By W. Mancab and A.E. Leighton.

~E.C. Powder.~

Nitro-Cotton      79.0  per cent.
Potassium Nitrate  4.5     "
Barium Nitrate     7.5     "
Camphor            4.1     "
Wood Meal          3.8     "
Volatile Matter    1.1     "

~Walarode Powder.~

Nitro-Cotton    98.6  per cent.
Volatile Matter  1.4     "

~Kynoch's Smokeless.~

Nitro-Cotton      52.1  per cent.
Di-nitro-Toluene  19.5     "
Potassium Nitrate  1.4     "
Barium Nitrate    22.2     "
Wood Meal          2.7     "
Ash                0.9     "
Volatile Matter    1.2     "

~Schultze.~

Nitro-Lingin       62.1  per cent.
Potassium Nitrate   1.8     "
Barium Nitrate     26.1     "
Vaseline            4.9     "
Starch              3.5     "
Volatile Matter     1.0     "

~Imperial Schultze.~

Nitro-Lignin    80.1  per cent.
Barium Nitrate  10.2     "
Vaseline         7.9     "
Volatile Matter  1.8     "

~Cannonite.~

Nitro-Cotton            86.4  per cent.
Barium Nitrate           5.7     "
Vaseline                 2.9     "
Lamp Black               1.3     "
Potassium Ferro-cyanide  2.4     "
Volatile Matter          1.3     "

~Amberite.~

Nitro-Cotton      71.0  per cent.
Potassium Nitrate  1.3     "
Barium Nitrate    18.6     "
Wood Meal          1.4     "
Vaseline           5.8     "

~Sporting Ballistite.~

Nitro-Glycerine  37.6  per cent
Nitro-Cotton     62.3     "
Volatile Matter   0.1     "

The following is a complete List of the Permitted Explosives as Defined in
the Schedules to the Explosives in Coal Mines Orders of the 20th December
1902, of the 24th December 1903, of the 5th September 1903, and 10th
December 1903:--

Albionite.
Ammonal.
Ammonite.
Amvis.
Aphosite.
Arkite.
Bellite No. 1.
Bellite No. 2.
Bobbinite.
Britonite.
Cambrite.
Carbonite.
Clydite.
Coronite.
Dahmenite A.
Dragonite.
Electronite.
Faversham Powder.
Fracturite.
Geloxite.
Haylite No. 1.
Kynite.
Negro Powder.
Nobel's Ardeer Powder.
Nobel Carbonite.
Normanite.
Pit-ite.
Roburite No. 3.
Saxonite.
Stow-ite.
Thunderite.
Victorite.
Virite.
West Falite No. 1.
West Falite No. 2.




INDEX.

Abel's, Sir Frederick, method of manufacturing gun-cotton, 57.

Abel's heat test, 249.

Acid mixture for nitrating nitro-glycerine, 23.

Air pressure in nitrator, 28.

Alkalinity in nitro-cellulose, 217.

Amberite, 189.

Ammonite, 149.

Analyses of collodion-cotton, 81.
  gelatine dynamites, 123.

Analysis of explosives, 197.
  acetone, 209.
  blasting gelatine, 199.
  cap composition, 241.
  cordite, 206.
  celluloid, 230.
  dynamite, 197.
  forcite, 202.
  fulminate, 240.
  glycerine, 233.
  gun-cotton, 212.
  nitric acid, 24.
  picric acid, 230.
  tonite, 205.
  waste acids, 239.

Armstrong on the constitution of the fulminates, 159.

Atlas powder, 119.

Auld on acetone, 211.

Axite, 176.



Ballistite, 179.

Beater or Hollander for pulping gun-cotton, 64.

Bedson, Prof., on roburite explosion gases, 140.

Bellite, 142.

Benzene, explosives derived from, 132.

Benzene, mono-nitro- and di-nitro-benzene, 134.

Bergmann and Junk on nitro-cellulose tests, 268.

Bernthsen summary of nitro-benzenes, 133.

Blasting gelatine, 119.

Blasting charge, preparation of, 166.

B.N. powder, 190.

Boiling-point of N.G., 19.

Boutnny's nitro-glycerine process, 15.

Brown on wet gun-cotton, 56.

Brugère's powder, 195.

Bucknill's resistance coil, 13.



Calculation of volume of gas evolved in an explosive reaction, 276.

Cannonite, 189.

Cellulose, 2, 47.

Celluloid manufacture, 91.
  analysis, 230.
  cartridges, 91.
  uses of, 90.
  Field's papers on, 93.
  fibre for, 94.
  nitration of fibre, &c., 95.
  formula of, 57.

Champion and Pellet's method of determining nitrogen, 223.

Chenel's modification of Kjeldahl's method, 227.

Collodion-cotton, 79.

Comparative tests of black and nitro-powders, 193.

Compressing gun-cotton, 77.

Composition of waste acids from nitro-glycerine, 43.

Composition of some common explosives, 290.

Conduits for nitro-glycerine, 7.

Cooppal powder, 5, 189.

Cordite manufacture, 169.
  analysis, 206.

Cresilite, 158.

Cross and Bevan on nitro-jute, 107.

Crusher gauge, 284.

Cundill, Colonel, classification of dynamites, 112.



Danger area, 5.

Dangers in the manufacture of gun-cotton, 85.

Decomposition of cellulose, 54.

Definition of explosives in Order of Council (Explosives Act), 1.

Determination of N_{2}O_{4} in nitric acid, 24.

Determination of strength of H_{2}SO_{4}, 25.

Determination of relative strength of explosives, 272.

Detonators, 163.

Di-nitro-toluene, 138.

Dipping cotton in manufacture of gun-cotton, 60.

Divers and Kawakita on the fulminates, 159.

Dixon, Prof. H.B., on roburite explosions, 139.

Drying house for gun-cotton, 122.

Dynamite, efficiency of, 118.
  frozen dynamite, 116.
  gelatine dynamite, 119.
  properties of kieselguhr dynamite, 116.
  Reid & Borland's carbo-dynamite, 119.
  Rhenish dynamite, 119.
  various kinds of, 119.



E.C. powder, 186.

Electronite, 151.

Emmensite, 195.

Equation of formation of nitro-glycerine, 16.

Equation of formation of nitro-cellulose, 50.

Exploders, electric, 167.

Explosion gases of dynamite, 19.
  nitro-glycerine, 18.
  gun-cotton, 55.
  roburite, 139.

Exudation test gelatines, 257.



Faversham powder, 147.

Favier's explosive, 149.

Field on celluloid, 93, 99.

Firing-point of explosives, 247.

Filite, 180.

Filtering nitre-glycerine, 37.

Flameless explosives, 89, 138, 144.

Formation of white matter in the nitration of N.G., 39.

Forcite, 119.

France, 82.

Free fatty acid in glycerine, 39, 235.

Freeing nitric acid from N_{2}O_{4}, 25.

Freezing-point of N.G., 21.

French Commission on Ammonium Nitrate, 142.

Fulminates constitution, 159.

Fulminate of mercury, 159, 240.

Fulminate of silver, 161.

Fuses, various kinds of, 166.



Gases formed by the decomposition of nitro-glycerine, 18.

Gelatine explosives, analysis of, 199.

Glycerine, analysis of, 233.
  formula of, 16.
  nitration of, 23.

Greiner's powder, 190.

Gun-cotton, analysis of, 212.
  boiling, 64.
  complete series of, 52, 54.
  compressing, moulding, and packing, 67, 77, 78.
  dipping and steeping the cotton, 60.
  drying the cotton, 58.
  granulation of, 79.
  manufacture of, 57.
  Abel's method, 57.
  Stowmarket, 57.
  Waltham Abbey, 71.
  products of decomposition of, 55.
  properties of, 54.
  pulping, 65.
  washing, 63.
  as a mining explosive, 56.

Guttmann's nitric acid plant, 45.

Guttmann's heat test, 256.



Handy's method for determining moisture in dynamite, 197.

Hannah, Dr N., on roburite explosion gases, 139.

Heat developed by explosives containing nitro-glycerine, &c., 288.

Heat test, Abel, 249.

Hellhoffite, 152.

Henrite powder, 191.

Hollander, 65.

Horsley's apparatus, 248.

Hydro-extractors for wringing out gun-cotton, 62.



Impurities in commercial glycerine, 39, 233.

Impurities in fulminate, 240.
  nitro-glycerine, 38.
  picric acid, 231.



Ketones as solvents for pyroxyline, 101.

Kieselguhr dynamite, 112.

Kinetite, 145.

Kjeldahl method of determining nitrogen, 227.



Le Bouchet, manufacture of gun-cotton at, 78.

Lead cylinders for testing strength of explosives, 281.

Lenk's improvements in gun-cotton manufacture, 49.

Lewes on the pressure of cordite, 175.

Leibert's treatment of nitro-glycerine, 30.

Lightning conductors for danger buildings, 10.

Liquefaction test for gelatine, 257.

Lodge on lightning conductors, 8.

Lowering of freezing-point of N.G., 21.

Lungé's nitrometer, 219.

Lydite, 156.



Manufacture of gun-cotton, 57.

Manufacture of nitro-glycerine, 17.
  cordite, 169.
  roburite, 140.
  fulminates, 162.
  tonite, 84.
  di-nitro-benzene, 138.
  nitro-starch, 103.
  celluloid, 91.

Majendie (Col. Sir V.D.), report on a picric acid explosion, 155.

Maximite, 191.

Maxim's detonator mixture, 165.

M'Robert's mixing machine, 126.

Mechanical equivalent of explosives, 273.

Melinite, 156.

Mono-nitro-glycerine, di-nitro-nitro-glycerine, 41.

Moulding gun-cotton, 77.

Mounds for protection of danger buildings, 6.

Mortar for ballistic tests, 275.

Mowbray on use of compressed air, 15.

Mühlhäusen on nitro-starch, 4, 5, 103.



Nathan's nitrator, 32.

Nitric peroxide in N.G., 24.

Nitration products of cellulose, 52, 54.

Nitro-glycerine, analysis of, 198.
  properties, 17.
  nitration, 23.
  separation, 35.
  washing, 37.
  uses of, 41.
  manufacture of, 17.

Nitro-benzene, properties and manufacture of, 132, 137.

Nitro-cellulose, 2, 47, 60, 212.

Nitro-jute, 5, 107.

Nitro-mannite, 4, 109.

Nitro-naphthalene, 148.

Nitro-starch, 4, 103.

Nitro-toluene, 132.

Nitrated gun-cotton, 83.

Nitrogen, determination of, Lungé method, 219.
  Champion and Pellet's, 223.
  Schultze-Tieman, 224.
  Kjeldahl-Chenel's, 227.
  percentages of in various explosives, 228.

Nitrometers, Lungé, Horn's, &c., 220, 222.

Nobel's ballistic test, 274.

Noble's pressure gauge, 282.
  experiments on cordite, 172.

Normal powder, 191.



Oleic acid in glycerine, 236.

Orsman on roburite, 142.

Oxonite, 152.

Oxy-cellulose, 102.



Packing gun-cotton, 78.
  dynamite, 116.

Page's regulator, 260.

Panclastite, 152.

Percentage composition of nitro-glycerine, 18.

Perkin on magnetic rotation of nitro-glycerine, 19.

Phenol, tri-nitro-phenol, 152.

Picric acid, 152, 231.
  powders, 157, 189.

Picrates, 154, 231.

Polarised light and nitro-cellulose, 218.

Position of the NO_{2} group in nitro-explosives, 2, 3, 16.

Prentice's nitric acid plant, 43.

Pressure gauge, 282.

Primers of gun-cotton, 166.

Properties of dynamite, 116.
  gelatine compounds, 130.

Pulping gun-cotton, 65.

Pyroxyline for celluloid, 96.
  solvents for, 101.



Quinan's foot-pound  machine, 280.



Raoult's law and N.G., 21.

Reworked gun-cotton, 78.

Rhenish dynamite, 119.

Roburite, properties and manufacture of, 138.
  Bedson's report on, 140.
  Orsman on gases produced by explosion of, 142.

Romit, 148.



Sarrau and Vieille, gases obtained from ignition of dynamite, 19.

Sayers, 50.

Scheme for analysis of explosives, 213.

Schultze's powder, 183.

Schultze-Tieman method of determining nitrogen, 224.

Securite, 144.

Separation of nitro-glycerine from mixed acids, 35.

Shimose, 156.

Silver test for glycerine, 233.

Smokeless powders, 168.

Smokeless diamond, 190.

Snyder's powder, 193.

Sobrero discovered nitro-glycerine, 14.

Sodium nitrate, analysis of, 239.

Soluble and insoluble nitro-cellulose, 51.

Solubility of nitro-glycerine, 20.

Solvents for soluble gun-cotton, 52, 101.

Solubility test for gun-cotton, 214.

Specific gravity of explosives, 270.

Sprengel's explosives, 151.

Stowmarket, manufacture of gun-cotton at, 57.

Sulphuric acid, determination of strength of, 24.

Sy on test for nitro-cellulose, 269.



Temperature of nitration of nitro-glycerine, 29.

Thomson's patents, 73.

Toluene, 146.

Tonite, 84, 146.
  analysis of, 205.
  fumes from, 85.

Treatment of waste acids, 43.

Trench's fire-extinguishing compound, 88.

Trebouillet and De Besancele on celluloid manufacture, 92.

Tri-nitro-cresol, 158.

Tri-nitro-toluene, 146.

Tri-nitro-phenol, 152.

Tri-nitro-glycerine, 2, 14.

Troisdorf powder, 191, 192.

Turpin's melinite, 156.



U.S. naval powder, 180.

Uses of celluloid, 91, 93, 102.

Uses of collodion-cotton, 90.



Vaseline, 208.

Vielle poudre, 190.

Volney's powder, 148.

Von Foster's powder, 191.



Walsrode powder, 188.

W.A. powder, 182.

Waltham Abbey, manufacture of gun-cotton at, 71.
  manufacture of cordite at, 169.

Walke's pressure gauge results, 289.

War Office experiments with cordite, 173.

Washing gun-cotton, 63.
  nitro-glycerine, 37.

Waste acids from nitro-glycerine, 41, 226.

Weltern powder, 191.

Werner & Pfleiderer's mixing machine, 124.

Whirling out the acids from gun-cotton, 62.

Will's test for nitre-cellulose, 261.

Wood pulp, 126.



Xylonite Company's process, 96.



Zenger's lightning conductors, 11.



_Printed at_ THE DARLEN PRESS, _Edinburgh_.