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SOME CONSTITUENTS OF THE POISON IVY PLANT (RHUS TOXICODENDRON)

DISSERTATION

SUBMITTED TO THE BOARD OF UNIVERSITY STUDIES OF THE JOHNS HOPKINS
UNIVERSITY IN CONFORMITY WITH THE REQUIREMENTS FOR THE DEGREE OF DOCTOR
OF PHILOSOPHY

BY WILLIAM ANDERSON SYME

1906

1906
THE SUN JOB PRINTING OFFICE
BALTIMORE

Transcriber's Note: Underscores around words indicates italics while an
underscore and curly brackets in an equation indicates a subscript.




CONTENTS.


Acknowledgments                                                 4

Literature                                                      5

Introduction                                                    7

Work of Khittel                                                11

Work of Maisch                                                 12

Work of Pfaff                                                  13

Experimental                                                   14

  Gallic Acid                                                  18

  Fisetin                                                      20

  Rhamnose                                                     23

  The Poison                                                   28

  Potassium Permanganate as a Remedy for Rhus Poisoning        35

Summary                                                        37

Biography                                                      38




ACKNOWLEDGMENTS.


The author desires to avail himself of this opportunity to tender his
thanks to those under whose guidance he has worked while a student at
the Johns Hopkins University, namely to Professors Remsen, Morse, Jones,
and Andrews, and to Doctors Acree and Tingle for instruction in lecture
room and laboratory.

He is especially indebted to Dr. S. F. Acree, at whose suggestion this
research work was undertaken, for counsel and assistance in its
prosecution.

He would also thank Messrs. Parke, Davis and Co., of Detroit, Mich., for
the preparation of the crude material used in this investigation, and
the U. S. Department of Agriculture, Washington, D. C., for electrotypes
of figures 17, 18, and 19 in Bulletin No. 20, Division of Botany.




LITERATURE.


Acides Gummiques, Garros (Dissertation) 1895.

American Chemical Journal.

American Journal of the Medical Sciences.

American Journal of Pharmacy.

Annalen der Chemie und der Pharmacie (Liebig).

Annales de Chimie et de Physique.

Berichte der deutschen chemischen Gesellschaft.

Biochemie der Pflanzen (Czapek) 1905.

Brooklyn Medical Journal.

Bulletin de la Société Chimique.

Bulletins 20 and 26 U. S. Department of Agriculture, Division of Botany.

Chemie der Zuckerarten, Von Lippmann, 1904.

Chemiker-Zeitung.

Comptes rendus.

Industries of Japan, J. J. Rein.

Journal of the Chemical Society.

Journal of Experimental Medicine.

Les Sucres, Maquenne, 1900.

Manual of Botany, 6th Edition, Gray.

Medical and Surgical Reporter.

New York Medical Record.

Proceedings of the American Pharmaceutical Association.

Treatise on Chemistry, Roscoe and Schorlemmer.

Über Mategerbstoff, Reuchlin (Dissertation) 1904.




SOME CONSTITUENTS OF THE POISON IVY PLANT.

(RHUS TOXICODENDRON)




INTRODUCTION.


Plants belonging to the natural order Anacardiaciæ (Cashew family or
Sumach family) are found in all the temperate climates of the world and
quite frequently in semi-tropical climates. Many of these plants play
important parts in economic botany, yielding dye-stuffs, tanning
material, wax, varnish, and drugs. Several species are poisonous. At
least three poisonous species of the genus _Rhus_ are found in the
United States. These three are all common and well-known plants, but
confusion frequently arises concerning them on account of the different
names by which they are known in different localities. For example,
poison ivy (_Rhus toxicodendron_ or _Rhus radicans_) probably the best
known poisonous plant in America, being found in all the States except
those in the extreme West, is often confounded with and popularly called
"poison oak." The true poison oak is the _Rhus diversiloba_ of the
Western States.[1] The third and most poisonous species of this plant is
_Rhus venenata_ or _Rhus vernix_; it is the _Rhus vernicifera_ of Japan,
from which Japanese lac is obtained. It is popularly known in the United
States as "poison sumach," "poison dogwood" and "poison elder." It grows
in swamps from Canada to Florida.

As the poison ivy is by far the most common of these plants in the
Eastern States, a brief description of it is given here:[2] A shrub
climbing by rootlets over rocks, etc., or ascending trees, or sometimes
low and erect; leaflets 3, rhombic-ovate, mostly pointed, and rather
downy beneath, variously notched, sinuate, or cut-lobed; high climbing
plants (_R. radicans_) having usually more entire leaves. It is found in
thickets, low grounds, etc. Greenish flowers appear in June.

[Illustration: Fig. 1.--Poison ivy (_Rhus radicans_ or _Rhus
toxicodendron_). _a_, spray showing aerial rootlets and leaves; _b_,
fruit--both one-fourth natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of
Agriculture.)]

[Illustration: Fig. 2.--Poison oak (_Rhus diversiloba_) showing leaves,
flowers, and fruit, one-third natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of
Agriculture.)]

In the general description of the order Anacardiaciæ, Gray[3] says:
"Juice or exhalations often poisonous." Whether it is contact with some
part of the plant, or with the exhalation from the plant, that causes
the well-known skin eruption has been a topic for discussion ever since
its source was known. On account of its intangible nature there has been
more speculation than experimental evidence bearing on this question,
although a few investigations have been made with the object of
isolating the poison. It is most generally believed that the exhalations
are poisonous. Dr. J. H. Hunt[4] states that the exhalations have been
collected in a jar and found to be capable of inflaming and blistering
the skin of an arm plunged into it.

[Illustration: Fig. 3--Poison sumach (_Rhus vernix_), showing leaves,
fruit, and leaf-scars, one-fourth natural size.

(Chesnut, Bulletin No. 20, Division of Botany, U. S. Department of
Agriculture.)]

Prof. J. J. Rein,[5] in his treatise on Lacquer Work, describes the
poison of the Japanese lac tree, _Rhus vernicifera_, as being volatile,
as do also the Japanese chemist Yoshida[6] and the French chemist
Bertrand.[7] Recent work by Prof. A. B. Stevens,[8] however, seems to
show that this poison is not volatile, and is similar to, if not
identical with that obtained by Pfaff[9] from _Rhus toxicodendron_ and
_Rhus venenata_.

Not many cases of internal poisoning by _Rhus toxicodendron_ are on
record in medical literature. Two cases of poisoning from eating the
fruit of this plant have been described.[10] The subjects of these cases
were two children who had eaten nearly a pint of the fruit. The symptoms
are described in detail, being in general, similar to those of
alkaloidal poisoning. Warm water was given to promote emesis; afterwards
large quantities of carbonate of soda were given in solution under the
belief that it was an antidote to the poison. Otherwise they were
treated on general principles. Both children recovered.

Another case of internal poisoning is the following:[11] Three children
drank an infusion of the root of poison ivy thinking it was sassafras
tea. The first of these cases was diagnosed as measles, but on the
appearance of similar symptoms in the sisters of the first patient, the
cause of the trouble was found. All recovered.

Dr. Pfaff[12] explains the few fatal cases that have followed Rhus
poisoning on the assumption that enough of the poison was absorbed
through the skin to cause renal complications in persons having chronic
kidney trouble. He showed that the poison, when given internally,
produces a marked effect on the kidneys, causing nephritis and fatty
degeneration of this organ.

The irritating action of poison ivy has been attributed at different
times to the "exhalation," to a volatile alkaloid, to a volatile acid,
and to a non-volatile oil. Pfaff,[13] who made the most recent
investigation of this poison, obtained from the plant a non-volatile oil
having the same action on the skin as the plant itself. He found this
oil in all parts of the plant and concluded that it was the active
principle, and that one could be poisoned only by actual contact with
some part of the plant. He assumed minute quantities of pollen dust to
be in the air to account for the cases of "action at a distance" so
frequently quoted. Pfaff says: "In my opinion, it is more than doubtful
if ever a case of ivy poisoning has occurred without direct contact with
the plant or with some article that has been in contact with the plant.
The long latent period of the eruption in some cases may obviously
render mistakes extremely easy as to the occasion when contact with the
plant really occurred." Granting, however, that the active principle is
practically non-volatile when isolated from the plant, we cannot say
positively that it is not volatile in the juices of the plant, or under
the influence of vital forces. It is quite conceivable that the water
transpired by the leaves of the plant may carry with it a quantity of
the poison sufficient to produce the dermatitis on a person very
susceptible to its action. It is also conceivable that a volatile poison
manufactured by a living plant could become non-volatile by changes in
it consequent upon the death of the plant.

Up to the present time, only three important chemical investigations of
the active principle of _Rhus toxicodendron_ have appeared in medical
and chemical literature, these being the researches of Dr. J. Khittel,
J. M. Maisch, a pharmacist, and Dr. Franz Pfaff, of the Harvard
University Medical School, to whose work reference has been frequently
made. The chemical work of these investigators and their conclusions are
given here in some detail for the sake of completeness.

FOOTNOTES:

[1] Chesnut. Bull. No. 20, U. S. Dept. of Agr., Div. of Botany.

[2] Man. of Bot., p. 119.

[3] Man. of Bot., p. 119.

[4] Brook. Med. Jour., June, 1897.

[5] Rein, The Ind. of Jap., p. 338, et seq.

[6] H. Yoshida on Urushi Lacquer, Jour. Chem. Soc., 1883, p. 472.

[7] Ann. de Chem. et de Phys., Series VII, Vol. 12, p. 125, 1897.

[8] Amer. Jour. Pharm. 78, p. 53, Feb., 1906.

[9] An account of Pfaff's work will be found in another part of this
paper.

[10] Amer. Jour. Med. Sci. 51 (1866), p. 560.

[11] Med. and Surg. Rep. 17, Nov., 1867.

[12] Jour. Exp. Med. 2 (1897), p. 181.

[13] Ibid.




KHITTEL'S INVESTIGATION.


The first attempt to find the poisonous constituent of this plant was
made by Khittel in 1857. His work was published in _Wittstein's
Vierteljahrresschrift für praktische Pharmacie_, VII, 348-359.[14]
Khittel obtained 37-1/2 ounces of fresh leaves of poison ivy from the
botanical garden in Munich, dried them, and got a residue of 9-1/2
ounces which he analyzed. Not detecting anything to which the poisonous
qualities of the plant could be attributed, he made another series of
experiments which, as he thought, showed that a volatile alkaloid is the
poisonous constituent. It was obtained by the following process: "3
ounces of the powdered leaves were infused with hot distilled water,
after three days strained, expressed, the liquid evaporated to 3 ounces,
and with the addition of potassa, carefully distilled to one-half. The
clear, colorless distillate had an alkaline reaction, and an odor
resembling henbane or hemlock. It was saturated with sulphuric acid,
evaporated, and treated with a mixture of equal quantities of alcohol
and ether which left sulphate of ammonia behind, the solution was
evaporated spontaneously, distilled with potassa, the alkaline
distillate neutralized with hydrochloric acid, and a precipitate could
now be obtained with chloride of platinum. Want of material prevented
further experiments."

The editor of the _American Journal of Pharmacy_ inserts the following
note: "It would have been more satisfactory if the author had given some
physiological evidence of the poisonous nature of the alkaloid
substance obtained. It is quite interesting to hear that the hitherto
intangible venom of this plant has at last been detected."

FOOTNOTES:

[14] A free translation of this paper is given in Amer. Jour. Pharm. for
1858, p. 542.




WORK OF MAISCH.[15]


The next investigation of this plant was made by Maisch in 1864. He
criticizes Khittel's experiments as follows: "It is well known that the
_exhalations_ of _Rhus toxicodendron_ exert a poisonous influence on the
human body; the poisonous principle must, therefore, be volatile and, at
the same time, be naturally in such a loose state of combination as to
be continually eliminated and separated with the usual products of
vegetable exhalations. It is natural to suppose that during the process
of drying, the greatest portion of the poisonous principle should be
lost. The loss must be still greater if the dried leaves are powdered, a
hot infusion prepared from them, and this infusion evaporated down to
the original weight of the dried leaves. It is obvious that Dr. Khittel
could not have selected a better method for obtaining the least possible
quantity of the poisonous principle, if, indeed, it could be obtained by
this process at all."

Maisch then worked up 8-3/4 ounces of the leaves of the plant in a way
to get the alkaloid, making some improvements on Khittel's method, but
failed to find it. Believing that the poison was a volatile acid, he
enclosed some fresh leaves of the plant in a tin box with several test
papers. The blue litmus paper became red showing the presence of an
acid. He concluded from this experiment that the exhalations of the
leaves contained a volatile organic acid which he thought was the
poisonous substance. To determine this point, he prepared the acid in
larger quantity by macerating the leaves with water, expressing and
distilling the expressed juice. He was poisoned in doing this work
although he had not been affected by handling the living plant and had
considered himself immune. He obtained an acid which investigation
showed to be somewhat like formic acid, more like acetic acid, but
having some reactions different from both. "Taking all the reactions
together, it is unquestionably a new organic acid for which I propose
the name of _Toxicodendric Acid_," writes Maisch. He further says: "That
it is the principle to which poison oak owes its effects on the human
system was proved to my entire satisfaction by the copious eruption and
formation of numerous vesicles on the back of my hand, on the fingers,
wrists, and bare arms while I was distilling and operating with it.
Several persons coming into the room while I was engaged with it were
more or less poisoned by the vapours diffused in the room; and I even
transferred the poisonous effects to some persons, merely by shaking
hands with them.

"The diluted acid, as obtained by me, and stronger solutions of its
salts, were applied to several persons, and eruptions were produced in
several instances, probably by the former, though not always, which was
most likely owing to the dilute state of the acid. Whenever this was
boiled, I always felt the same itching sensation in the face, and on the
bare arms, which I experience on continual exposure of my hands to the
juice of the plant."

Toxicodendric acid was thought to be the active principle from the time
of Maisch's work until the investigation by Pfaff in 1895.

FOOTNOTES:

[15] Proc. Amer. Pharm. Assn. 1865, p. 166, and Amer. Jour. Pharm. 1866,
p. 4.




PFAFF'S WORK.


By far the most valuable work on _Rhus toxicodendron_ is that of Pfaff.
From a clinical study of Rhus poisoning, Pfaff came to the conclusion
that the poison must be a non-volatile skin irritant. The more volatile
the irritant, the quicker is its action on the skin. Formic acid acts
very quickly; acetic acid, less volatile than formic, acts more slowly,
but still much more quickly than poison ivy, the latent period of which
is usually from two to five days. Pfaff thought that the volatile acid
obtained by Maisch might have contained some of the poisonous principle
as an impurity, but that it would not produce the dermatitis if prepared
in a pure state. He therefore prepared a quantity of the acid by
distilling the finely divided fresh plant with steam. The yield was
increased by acidulating the mixture with sulphuric acid before the
distillation. The acid distillate so obtained was freed from a
non-poisonous oily substance by shaking the solution with ether. Barium
and sodium salts were made by neutralizing the acid, and were purified
by crystallization. Analysis showed them to be salts of acetic acid, and
they gave the characteristic tests for this acid. The toxicodendric acid
of Maisch was thus shown to be acetic acid, and was therefore not the
poisonous principle of the plant.

Pfaff obtained the active principle by the following process: The plant
was extracted with alcohol, the alcohol was distilled off, and the
residue was taken up in ether. The ether solution was washed with water
and dilute sodium carbonate solution, and the ether was evaporated. An
oily, black, poisonous substance partly soluble in alcohol was obtained.
To get the active principle in a pure state, this residue was extracted
with alcohol and filtered and the filtrate was precipitated fractionally
by lead acetate. The final precipitates consisted of the lead compound
of the poison in a pure state. On decomposing the lead compounds with
ammonium sulphide, shaking out with ether, and letting the ether
evaporate spontaneously, a non-volatile oil was obtained which gave the
characteristic skin eruptions. The pure lead compounds made in different
preparations were analyzed and assigned the formula C_{21}H_{30}O_{4}Pb.
The oil itself was not analyzed. Pfaff proposed the name _Toxicodendrol_
for the oil. He found that it was not volatile, was decomposed by heat,
was soluble in alcohol, ether, chloroform, benzene, etc., but insoluble
in water. Its effects upon the human skin were studied in many
experiments upon himself and others. It was shown that an exceedingly
minute quantity of the poison will produce the dermatitis, even 1/1000
milligram applied in olive oil being active. The oil was given
internally to rabbits, its effects being most marked on the kidneys.

The oil obtained by Pfaff from _Rhus venenata_ seemed to be identical
with that from _Rhus toxicodendron_.




EXPERIMENTAL.


The writer's investigation was undertaken with the object of attempting
to throw more light on the chemical nature of the poisonous substance
found in _Rhus toxicodendron_. Soon after commencing work, however, it
became apparent that the poison could be more intelligently studied if
the substances associated with it in the plant were first identified;
the scope of the work was therefore extended to an investigation of the
other constituents of the plant, and it was hoped that a knowledge of
the properties of these constituents would suggest a more economical way
of getting the poison than the method of fractional precipitation.

The crude material for this work was prepared by Messrs. Parke, Davis &
Co., of Detroit, Mich., according to special instructions submitted to
them: 67-1/2 pounds of fresh leaves and flowers of poison ivy were
collected near Detroit and carefully inspected by a competent botanist.
This material was thoroughly macerated and put into ten-liter bottles
with ether. The mass was thoroughly shaken, water being added to make it
more mobile. The ether was then separated off and the extraction was
repeated three times in the same way to insure complete removal of the
toxicodendrol. The ether extracts were combined, thoroughly dried with
anhydrous sodium sulphate, and the ether was distilled off, the
temperature being kept below 40° C. during the entire distillation. The
residue after the removal of the ether was a thick, black, tar-like
mass, weighing 3 pounds 11 ounces. In extracting the plant, about
twenty-four gallons of ether were used. It is a significant fact in
regard to the volatility of the poison that during the process of
preparing this material none of the employees engaged in the work were
in any way affected, since proper precautions were taken and the
utensils were handled with rubber gloves.

The crude ether extract, which will be designated as the "original
material," was shipped to Baltimore in August and was kept in a cool
place until November when the investigation was begun. When the bottle
was opened, there seemed to be an escape of a vapor, and a nauseating
odor suggesting crushed green leaves pervaded the atmosphere. Some days
later, irregular red patches appeared on the face though a mask of
cotton cloth was worn during the work, and the hands were protected by
rubber gloves.

Assuming from Pfaff's work that this original material contained the
non-volatile oil toxicodendrol, the first experiment was to try to
distil it out under diminished pressure. For this purpose, an Anschütze
distilling bulb containing ten grams of the tar was connected with a
vacuum pump. After a pressure of 2 mm. had been established the bulb was
gradually heated in a bath of Wood's metal. Nothing distilled over. The
material began to carbonize at a temperature of 140° to 150°.

It was then thought that perhaps the oil could be converted into an
ester which might be more volatile and could be distilled out. 20 grams
of the original material were dissolved in 100 cc. of absolute alcohol
containing 3 grains of hydrochloric acid gas, and the mixture was heated
10 hours on a water-bath under a return condenser. After the heating,
the mixture had a delightful ethereal odor. The flask was corked and
left standing several weeks while other work was in progress. The ester
solution was then put in a vacuum desiccator over sulphuric acid and the
alcohol evaporated. A black, tarry, solid mass was left having the ester
odor. It was extracted with warm water and filtered from insoluble tar.
The filtrate had a green color and the ethereal odor. It was shaken out
with ether; the ether layer had a blood-red color while the water layer
was deep green. The extraction with ether was continued until the water
layer was no longer green. The combined ether extracts were evaporated
in a desiccator without heat. A black tar-like solid was left very much
like the original material, but it had the ester odor. It was partly
soluble in water and readily soluble in alcohol. The alcoholic solution
was tested on the skin and found to be not poisonous. The ester, or
mixture of esters, was not investigated further in this connection, but
was later shown to give the reactions for gallic acid and methyl
furfurol. These reactions will be referred to in connection with other
experiments.

After a few other preliminary experiments, it became evident that the
original material was a complex mixture of substances and that it would
have to be fractionated by some means and the fractions studied
separately.

A portion of the original substance was treated with 50 per cent.
alcohol and was found to be partly soluble in this medium. The solution
was filtered from insoluble tar. A portion of the yellow filtrate gave a
reddish yellow precipitate with lead acetate. The alcoholic solution was
distilled in an Anschütze flask under diminished pressure; a yellow
liquid condensed in the arm of the flask while most of the alcohol was
collected in a bottle connected with the arm. The yellow liquid was acid
to litmus. Water was added, the solution was shaken out with ether and
the ether was evaporated. When the small residue was completely dry, it
was a yellow solid soluble in dilute alcohol and acid to litmus. The
substance was not volatile enough to justify the use of this method for
getting it.

Chlorophyll could not be removed from the original substance because the
solvents for chlorophyll such as alcohol, ether, fats, petroleum, and
carbon bisulphide dissolve large quantities of the mixture.

A precipitate obtained by adding lead acetate to a filtered solution of
the original substance in 50 per cent. alcohol was suspended in water,
decomposed by hydrogen sulphide, shaken out with ether and the ether
evaporated. The residue appeared at first to be a yellow oil, but on
complete evaporation of the ether in a desiccator, a yellow solid was
obtained--apparently the same as that obtained by vacuum distillation.

A solution of the original material in 50 per cent. alcohol was filtered
through bone-black and the filtrate was colorless. Examination showed
that everything had been removed by the bone-black and the filtrate was
apparently pure alcohol and water.

In precipitating an alcoholic solution of the crude material with a
solution of lead acetate, it was noticed that at least two kinds of
precipitates were formed. The part that went down first was darker in
color than that thrown down later. Pfaff used the last fractions in
obtaining his oil and stated that these precipitates consisted of the
lead compound of the oil in a pure state. It was found by experiment
that the darker part was soluble in ether while the lighter part was
not. This indicated that the darker part consisted of tarry matter which
was brought down mechanically or separated out when the alcoholic
solution was diluted by the lead acetate solution, or was perhaps a lead
compound soluble in ether. To test this point an experiment was made as
follows: Some of the crude material was thoroughly extracted with 50 per
cent. alcohol. The tar insoluble in 50 per cent. alcohol was then
treated with 95 per cent. alcohol; most of it dissolved; the solution
was filtered and lead acetate in 50 per cent. alcohol was added. A
greenish colored precipitate was formed which was filtered off and found
to be completely soluble in ether and soluble to a considerable extent
in strong alcohol. These experiments suggested that the light colored
lead compound which was thought to contain the poison could be purified
by extraction with ether in a Soxhlet apparatus more conveniently than
by the tedious process of fractional precipitation. Further preliminary
experiments showed that 50 per cent. alcohol extracted from the original
material all of the substance or substances which gave the light colored
precipitate and dissolved only a small amount of the tar.

Two hundred and eighty-eight grams of the crude material were then
extracted several times with 50 per cent. alcohol and filtered; the
insoluble tar was washed and saved for examination. To the filtrate was
added an excess of a solution of lead acetate in 50 per cent. alcohol.
The large precipitate, which will be designated as "precipitate A," was
filtered and drained by suction in a Büchner funnel. The alcoholic
"filtrate A" was saved. Precipitate A was extracted with ether in
Soxhlet extractors until the ether came over practically colorless, the
operation being interrupted from time to time to stir up the precipitate
in the thimble. The green colored ether solution was saved for future
examination. The lead precipitate, after extraction with ether and
drying, weighed about 116 grams. A portion of this lead compound was
decomposed by hydrogen sulphide in a mixture of water and ether which
was well shaken during the operation. The ether was separated, filtered,
and evaporated under diminished pressure without heat, and there
remained a yellow oily looking residue having a pleasant odor. When the
ether and water were completely removed in a vacuum desiccator, a hard,
brittle, yellow resin weighing about 16 grams was obtained. It was
soluble in alcohol, had a strong acid reaction and was free from
nitrogen[16] and sulphur. The nitrogen tests were made by the Lassaign
and soda lime methods,[17] and the sulphur test was made with sodium
nitroprusside after fusing the residue with sodium. The main portion of
the lead compound was decomposed under alcohol by hydrogen sulphide,
filtered, and the alcoholic filtrate evaporated in vacuo. The same
yellow acid resin was obtained. Experiments continuing through several
weeks were made in applying solutions of this resin to rats, rabbits and
guinea pigs. Finding it to be without effect upon these animals it was
tried on the writer and found to be not poisonous.[18] In the meantime
the resin was being studied in the laboratory.


GALLIC ACID.

An alcoholic solution of the resin was just neutralized with potassium
hydroxide. During the titration, the solution rapidly became dark brown.
After neutralization it was shaken with ether; the water solution
remained brown while the ether layer was nearly colorless and contained
practically no dissolved substance. A portion of the water solution of
the potassium salt on being acidified with sulphuric acid and standing
over night, deposited a slight precipitate. The solution of the
potassium salt gave a heavy precipitate with lead acetate somewhat
similar to the original lead precipitate A, and also slight precipitates
with salts of zinc, mercury, copper, and silver (with reduction). It
gave a bluish-black color with impure ferrous sulphate and a dark color
with ferric chloride. It reduced ammoniacal silver nitrate and Fehling
solution. These experiments indicated the presence of a tannin compound.
An alcoholic solution of the resin gave the same color reactions with
iron salts as did the potassium salt. To determine which one of the
tannin compounds was present was a matter of some difficulty since the
di- and tri-hydroxybenzoic acids have in general the same color
reactions. The presence of other plant substances in the solution also
interferes with the color tests, and finally, a substance which gives a
blue color with iron salts and one giving a green color may be found
together in the same plant.[19] Further tests with a solution of the
resin in dilute alcohol, and with a water solution of the acid
precipitated by adding sulphuric acid to a solution of the resin in
potassium hydroxide, led to the conclusion that the acid is gallic acid.
These tests were the following:

(1) Boiling with an excess of potassium hydroxide gave a black substance
(tauromelanic acid).

(2) The acid was not precipitated by gelatin.

(3) On addition of potassium cyanide a transitory red color appeared
which reappeared on shaking with air.

Gallic acid is distinguished from tannic acid by tests (2) and (3). At
later stages in the work the potassium, barium, and sodium salts of
gallic acid were obtained, and finally the pure acid was made by
decomposing the sodium salt with sulphuric acid and crystallizing from
water. A portion of the acid so obtained was further purified by
dissolving in absolute alcohol and pouring into absolute ether.[20] The
melting point behavior of the acid corresponds with that of gallic acid;
it melted with decomposition at about 230°. For further identification,
some of the acid was converted into an ester by the following process:
it was dissolved in 80 per cent. alcohol, hydrochloric acid gas was
passed in, and the solution was heated an hour on the water bath. It was
then evaporated to a small bulk, neutralized with barium carbonate and
extracted with ether. The ether, on evaporation, left the ester which
was crystallized from water and dried in a desiccator over sulphuric
acid. The anhydrous ester agreed in melting point (156° to 159°) and
other properties with the ester of gallic acid described by Grimaux.[21]
For the sake of comparison, an ester was made from gallic acid obtained
from another source and the two agreed in properties. A mixture of the
two esters melted within the limits given for the ester of gallic acid.

While the tests leading to the identification of gallic acid were being
made, another series of experiments was in progress. Eleven and one-half
grams of the resin obtained from lead precipitate A by decomposition
with hydrogen sulphide were treated with 0.1 n. potassium hydroxide
added from a burette until the acid was exactly neutralized. All went
into solution. On shaking with ether, some of the potassium salt
separated out and was saved for examination. The solution became brown
on exposure to air and got darker as the work proceeded. The acid in
solution as a potassium salt was precipitated out in four fractions by
adding for each fraction one-fourth the amount of 0.1 n. sulphuric acid
required to neutralize the potassium hydroxide used. The precipitates
were filtered off and examined. The first was small in amount, gummy and
hard to filter. The solution was shaken with ether after each
precipitate had been filtered off. The succeeding precipitates were in
better condition, but were not pure. All appeared to be impure gallic
acid which had become brown by absorption of oxygen. They were saved,
however, to be tested for poison. After the last fraction had separated,
the filtrate was shaken several times with ether and saved for further
examination, which will be described under "Rhamnose." This filtrate is
designated as B.

At this stage of the work a portion of the resin obtained from lead
precipitate A was tested and found to be not poisonous as already
mentioned. By this test, all the substances contained in the lead
precipitate A after its extraction with ether in the Soxhlet apparatus,
were eliminated from the possible poisonous substances. The poison must
therefore have been extracted by the ether.

A fresh portion of the original poisonous material was treated with 50
per cent. alcohol and filtered from insoluble tar. The filtrate was
precipitated in six fractions by lead acetate. The last fractions were
lighter in color and apparently much purer than the first. The sixth
lead precipitate was decomposed by hydrogen sulphide, the light-yellow
water solution was tested and found to be not poisonous. It gave the
characteristic reactions for gallic acid. The poison, if precipitated at
all by lead acetate, must have gone down in one of the preceding
fractions. Later experiments showed that it is brought down partly
mechanically and partly as a lead compound in the first precipitates.


FISETIN.

Having identified gallic acid, and not finding any other phenol
derivative in the lead precipitate, some of the original material was
extracted with hot water to remove gallic acid and filtered from tar
while hot. The filtrate had a deep yellow color. On cooling over night,
an olive green precipitate separated out which was dried and found to be
a light powder. It was practically insoluble in cold water, soluble
with great difficulty in boiling water from which it separated in yellow
flakes, slightly soluble in ether and in acetic acid, but readily
soluble in alcohol. The solutions were not acid to litmus, gave a dark
color with ferric chloride, an orange-red precipitate with lead acetate
which was easily soluble in acetic acid, and an orange-yellow
precipitate with stannous chloride. These properties and reactions
indicated that the substance was the dye-stuff fisetin and that it
occurs in the free state in this plant though it is usually found as a
glucoside of fisetin combined with tannic acid. A compound of this kind
was found in _Rhus cotinus_ and named "fustin-tannide" by Schmid[22]. He
showed that the fustin-tannide could be decomposed by acetic acid into
tannic acid and a glucoside, fustin C_{46}H_{42}O_{21}. Fustin, on
heating with dilute sulphuric acid, gave fisetin and a sugar supposed to
be rhamnose. Fisetin was also found as a glucoside compound in _Rhus
rhodanthema_ by Perkin.[23]

The yellow substance which separated from the boiling water solution was
further purified by dissolving in a small quantity of hot alcohol and
adding hot water. On cooling, the yellow substance separated out in a
flocculent condition. Examined under the microscope, the flakes appeared
to be made up of masses of fine crystals.

An alcoholic solution of the substance gave a black color with ammonia
which became red on addition of more ammonia. Concentrated acids
intensified the yellow color of the alcoholic solution. Fehling solution
and ammoniacal silver nitrate were reduced by it. Potassium hydroxide
added to an alcoholic solution gave at first a deep red color
accompanied by a green fluorescence which disappeared, leaving a yellow
liquid. With an excess of caustic potash, the red color returned and was
permanent. These reactions are characteristic for fisetin.[24]

Furthermore, fisetin should give protocatechuic acid and phloroglucinol
by fusion with caustic potash under proper conditions.[25] The
experiment was carried out as follows: 2 grams of fisetin were gently
heated in a nickel crucible with 6 grams of caustic potash dissolved in
6 cc. water. An inflammable gas, apparently hydrogen, was evolved during
the fusion. The pasty mass was dissolved in water, acidified with
sulphuric acid, and filtered. The filtrate was shaken out with ether
containing one-fourth its volume of alcohol. The ether was evaporated
and the residue was extracted with warm water and filtered. Lead acetate
was added to the filtrate to precipitate protocatechuic acid, while
phloroglucinol remained in the filtrate from this precipitate. The lead
precipitate was suspended in water, decomposed by hydrogen sulphide,
filtered, and evaporated to obtain protocatechuic acid. That the
substance obtained was protocatechuic acid was shown by the following
characteristic tests:

(1) It gave a greenish brown color with ferric chloride; on addition of
one drop of a dilute solution of sodium carbonate, the color became dark
blue; on adding more sodium carbonate the color became red.

(2) A violet color was obtained when a solution of the acid was treated
with a drop of sodium carbonate solution and then with a drop of ferrous
sulphate.

(3) It reduced ammoniacal silver nitrate.

(4) It did not reduce Fehling solution.

The filtrate supposed to contain phloroglucinol was treated with
hydrogen sulphide to remove lead, filtered, and shaken with ether. The
residue left on evaporating the ether was taken up in water. This
solution gave the following reactions characteristic for phloroglucinol:

(1) It reduced both silver nitrate and Fehling solution.

(2) It colored pine wood moistened with hydrochloric acid red.

(3) It gave a red color with vanillin and hydrochloric acid, and

(4) A deeper red color with oil of cloves and hydrochloric acid,
becoming purple on standing.

(5) It gave a violet color with ferric chloride.

The substance is then, without doubt, fisetin. The formula[26] of
fisetin is supposed to be C_{15}H_{10}O_{6}.


RHAMNOSE.

It was stated above that Schmid obtained a sugar solution by the
decomposition of a fisetin-glucoside from _Rhus cotinus_, and Perkin
obtained the same from a glucoside in _Rhus rhodanthema_. These
investigators thought that the sugar was isodulcite or rhamnose, but
they did not isolate it on account of the small quantities of material
at their disposal. Moreover, the sugar is very hard to crystallize in
the presence of other soluble substances and is not found in large
quantity in plants. Maquenne[27] could obtain only 15 to 20 gm. of
rhamnose by working up 1 kilogram of the berries of _Rhamnus
infectorius_. Assuming that the free fisetin found in poison ivy leaves
had its origin in the decomposition of a fisetin-glucoside by natural
processes, it was reasonable to suppose that the sugar would also be
found in the free state, although, according to Roscoe and
Schorlemmer:[28] "Isodulcite does not occur in the free state in nature,
but is found as a peculiar ethereal salt belonging to the class of
glucosides. On boiling with dilute sulphuric acid, this splits up into
isodulcite and other bodies...." The more recent works on the sugars and
on plant chemistry[29] mention the occurrence of rhamnose only in the
glucoside form, with one possible exception. The exception referred to
is the occurrence of a free sugar, supposed to be rhamnose, in a certain
palm-wine.[30] Czapek says:[31] "The well-known methyl pentoses do not
occur in the free state in plant organisms so far as we know."

Since rhamnose forms a lead compound, the sugar, if present, should be
found in the first lead precipitate, A, and also in filtrate A in case
it is not completely precipitated in the presence of acetic acid and
alcohol.

The filtrate A (about two liters) was examined first. It had a light
yellow color, contained an excess of lead acetate, and was acid from the
acetic acid liberated in the precipitation of the lead compound A.[32]
This filtrate was evaporated to dryness under diminished pressure to
remove alcohol, water, and acetic acid. The clear distillate had a
peculiar odor suggesting both tea and amyl formate. It was saved for
examination and was found to be not poisonous. The residue in the dish
after evaporation was a tough reddish brown, gummy mass which could be
drawn out into fine threads. It had a pleasant sweet odor. It was
extracted several times with hot water, each portion being filtered. A
brownish yellow powder remained undissolved and was saved. The combined
filtrates deposited more of the yellow solid on standing. This powder
will be referred to later as "P." The filtered liquid was freed from
lead by hydrogen sulphide. The solution then had a lemon yellow color, a
sweet odor and was acid from acetic acid. On concentrating the solution
by evaporation and making a small portion of it alkaline with sodium
hydroxide, the yellow color came out very intense[33]. The alkaline
solution reduced Fehling solution and ammoniacal silver nitrate,
indicating the presence of a sugar. Another portion of the solution gave
a slight precipitate with phenyl hydrazine in the cold. The remainder of
the solution was evaporated to dryness, extracted with water, filtered,
and again evaporated. A dark sticky syrup was left which was only partly
soluble in water. This was treated with water, filtered, and the
filtrate was evaporated, the water being replaced from time to time to
remove acetic acid. Finally the liquid gave the following tests for
rhamnose, besides those already mentioned:

(1) With alpha-naphthol[34] and sulphuric acid, a purple violet
color.

(2) With thymol[35] and sulphuric acid, a red color.

(3) With resorcinol[36] and sulphuric acid, red color.

(4) With orcinol[37] and hydrochloric acid, red color.

(5) With ammonium picrate and sodium picrate, yellowish red color.

(6) With phloroglucinol and hydrochloric acid, red color.

(7) It decolorized an alkaline solution of potassium ferricyanide.

(8) It gave a white precipitate with lead acetate.

The filtrate B (p. 20) from which gallic acid was precipitated by
sulphuric acid in four fractions was saved to examine for sugar. To
remove gallic acid completely, and other vegetable matter, it was shaken
out several times with ether, and was kept at a low temperature with
salt and ice for a long time. It was left standing for several weeks,
during which time more brown matter separated out and was filtered off.
The filtrate was evaporated to a small bulk, cooled, and filtered from
crystals of potassium sulphate. The filtrate was evaporated to dryness,
the residue taken up in water and filtered through bone-black. Addition
of alcohol caused complete precipitation of potassium sulphate. The
solution then gave the above mentioned characteristic tests for
rhamnose.

All attempts to get the osazone of the sugar by the method of
Fischer[38] failed, probably on account of the small quantity of the
sugar present. The plant, it will be remembered, was originally
extracted with ether in which rhamnose is practically insoluble. The
above described tests, however, can leave no doubt as to the identity of
the sugar.

Additional evidence that the sugar is rhamnose was obtained by a method
described by Maquenne[39] as follows:

     "The production of methyl furfurol in the dehydration of
     isodulcite furnishes a very simple means of characterizing
     this sugar in mixtures which contain it; it is sufficient,
     for example, to distil 50 gm. of quercitron wood with as
     much sulphuric acid and about 150 gm. of water, then to
     rectify the liquid obtained in order to get several drops of
     the crude furfurol, which on addition of alcohol and
     concentrated sulphuric acid gives immediately the green
     coloration characteristic of methyl furfurol. This procedure
     is applicable to extracts as well as to entire plants, and
     has the advantage that it does not require the separation of
     isodulcite, the crystallization of which is often very slow
     and at times impossible when it is mixed with other very
     soluble substances."

The experiment was tried with the crude ether extract of the plant
according to the directions of Maquenne, and the green color with
alcohol and sulphuric acid was obtained from the thicker oily portion of
the distillate. This test can be made with hydrochloric acid[40] as well
as with sulphuric. Therefore the color test was tried with the ester
mixture prepared in one of the early experiments by boiling the original
plant material with hydrochloric acid and alcohol. Methyl furfurol was
found here also, this method indeed giving better results than that of
Maquenne.

The presence of free rhamnose has thus been shown in the original
material, in the first precipitate by lead acetate, and in the filtrate
from this precipitate. Experiments to be described under "The Poison"
showed that the ether extract from the Soxhlet apparatus contained a
substance which yielded rhamnose when hydrolyzed by dilute sulphuric
acid.

The presence of free gallic acid, fisetin, and rhamnose in the plant can
be readily explained by a series of assumptions for which there is a
considerable amount of experimental evidence. There is reason to believe
that tannin-like bodies are formed at the expense of chlorophyll,[41]
that complex tannin bodies can be broken down by acetic acid (also found
in _Rhus toxicodendron_) into a tannic acid and a glucoside (for
example, the "fustin-tannide" mentioned above yields tannic acid and
fisetin-glucoside); and finally that the glucoside can be hydrolyzed by
acids or enzymes giving, in the sumach plants, fisetin and rhamnose.

Nitrogenous ferments which can effect the hydrolysis of glucosides and
give rise to sugars are frequently found in plants, for example, emulsin
in almonds, myrosin in mustard, and erythrozym in madder. Acree and
Hinkins[42] found that diastase, pancreatin, and a number of other
enzymes cause hydrolysis of triacetyl glucose with the formation of
glucose and acetic acid. Stevens[43] obtained a nitrogenous oxidizing
enzyme from _Rhus vernicifera_. The close relationship between the
poisonous species of _Rhus_ would lead us to suppose that the same
soluble ferment exists in poison ivy, though it was not detected in the
original material used in these experiments, probably because the plant
was extracted with ether in which the enzyme is insoluble. The existence
of such a soluble ferment would explain the presence of free sugar and
free fisetin.


EVIDENCE OF THE PRESENCE OF A FATTY ACID IN FILTRATE A.

The brown substance P, obtained from filtrate A by evaporation and
extracting the residue with hot water, was suspended in warm water and
dilute sulphuric was added. A white precipitate was formed and a strong
fatty acid odor was developed. After the mixture had been heated for
some hours on the water bath a small portion was made alkaline and it
reduced Fehling solution. The main solution was filtered and the
precipitate supposed to be a fatty acid was saved. The filtrate was
neutralized with barium carbonate, filtered, evaporated, freed from
caramel, and the solution then gave the tests mentioned above for
rhamnose.

A portion of the precipitate supposed to be a fatty acid was ignited in
a porcelain spoon. It fused, carbonized, and burned. The remainder was
heated with alcoholic potash and reprecipitated with hydrochloric acid.
The precipitate was washed and heated with alcohol. Part of it
dissolved. The insoluble part was found to be a lead compound. On
boiling it with hydrochloric acid and cooling, lead chloride
crystallized out. This was confirmed by dissolving the lead chloride in
hot water and precipitating as lead sulphide. These experiments were not
carried farther on account of the small quantity of material, but they
show that the gummy substance obtained from filtrate A contained
rhamnose (either as a lead compound of free sugar or as a lead compound
of a rhamnoside), and also, most probably, the lead compound of an
organic acid.[44]


THE FRAGRANT DISTILLATE.

Several times in the course of this work, extracts of the original plant
material in alcohol and in water were distilled under diminished
pressure for the purpose of concentrating the solutions. The distillate,
in every case, had an ethereal odor suggesting amyl formate in very
dilute solution, but was more fragrant. The distillate from a water
extract was examined. It was a clear liquid, a little darker than pure
water, was not poisonous, was neutral to litmus paper, gave no color
with ferric chloride, reduced ammoniacal silver nitrate, but not Fehling
solution, and gave a faint red color with dilute ammonium hydroxide and
with sodium carbonate.

A small quantity of a finely divided black precipitate separated out
from the water distillate on standing.

The substance with the fragrant odor was extracted by shaking the
distillate with ether and letting the ether evaporate spontaneously. A
very small quantity of a yellow solid was deposited on the sides of the
dish. This substance had a strong and persistent odor, so sweet as to be
almost nauseating. Not enough was obtained for examination or analysis.
This fragrant residue was difficultly soluble in water and the solution
reduced silver nitrate in ammonia. A steam distillate of the original
plant material had the same fragrant odor as the distillate from a water
extract.


THE POISON.

288 grams of the original poisonous material were extracted with 50 per
cent. alcohol, and this alcoholic solution was precipitated with lead
acetate in the manner already described (p. 17). The lead precipitate so
obtained was extracted with ether in Soxhlet extractors and after the
extraction was found by test to be free from poison. Therefore the
poison, if precipitated by the lead acetate, must have been extracted by
the ether. This ether solution had a dark green color, and was acid from
acetic acid brought down in the lead precipitate. The ether was
evaporated in a vacuum desiccator without heat and there remained a
small quantity of an acid mixture of water and a soft tar; the watery
part was colored green, showing that the tar was soluble to some extent
in dilute acetic acid. The mixture had the peculiar odor of the original
material. A small drop of the green watery part was applied to the
wrist, allowed to remain a few minutes and was then removed by absorbent
paper, but the spot was not washed. Itching and reddening of the skin
commenced within twenty-four hours. At the end of forty-eight hours,
there was a well developed case of poisoning. How this was cured will be
described in another place.

A small portion of the poisonous mixture was dissolved in alcohol, and
this solution was divided into three parts. The first part was treated
with ferric chloride, but it gave no color reaction. Another portion of
the alcoholic solution was diluted with water. It became turbid. The
third portion gave a dirty-green precipitate with lead acetate, which
seemed to come down more readily when the solution was diluted with
water. The main portion of the poisonous mixture was then dissolved in
95 per cent. alcohol and lead acetate in 50 per cent. alcohol was added.
The precipitate was filtered, washed, and decomposed by hydrogen
sulphide in a mixture of water and ether. The ether solution was
filtered and evaporated. The residue was a tar which, on standing in a
desiccator for some time, became dry enough to break into sticky lumps.
An alcoholic solution of this substance gave a dark color with ferric
chloride and a light colored precipitate with lead acetate.

To get more of the poisonous tar for study, 233 grams of original
material were extracted with 95 per cent. alcohol. Strong alcohol was
used in order to dissolve as much of the tar as possible. The solution
had a dark greenish color, but was somewhat yellow in thin layers. The
undissolved tar was filtered off and extracted twice again in the same
way. The tar left after the third extraction was only slightly soluble
in alcohol, and its solution was not poisonous. The three filtrates from
these three extractions were precipitated separately by lead acetate in
50 per cent. alcohol. The first precipitate was largest, darkest in
color, and carried down more tarry matter. The second was light green,
and the third was quite small, black, and was not a lead compound at
all, but some of the tar which separated out on diluting the strong
alcohol with the weaker grade containing lead acetate. It was soluble in
ether and less soluble in alcohol. The alcoholic solution of this third
lot gave no precipitate with hydrogen sulphide. The first and second
lead precipitates were filtered by suction and washed with water. They
were kept a day or two in a desiccator over sulphuric acid, but did not
become completely dry. The weight of these two moist precipitates
together was 172 grams. They were combined and extracted with ether in
Soxhlet extractors which were kept in operation during work hours for
three days.

In the meantime the alcoholic filtrates from these lead precipitates
were combined and concentrated on the water bath by distilling off two
liters of alcohol. The alcohol obtained had the peculiar odor of the
original material, but was not poisonous.

After a long extraction of the lead precipitate in the Soxhlet
extractors, the green ether solutions were combined and washed by
shaking them with water to remove lead acetate and acetic acid in case
any should have been held in the lead precipitate. The ether was
distilled off at a low temperature and there remained a soft tar, a
portion of which was not completely soluble in 95 per cent. alcohol. The
alcoholic solution had a greenish yellow color and was poisonous. The
tar was also partly soluble in acetic acid, and this solution was found
to contain lead. Thinking that the lead acetate had not been completely
washed out, the main part of the tar was dissolved in ether and shaken
with water. The wash water continued to give a test for lead as long as
the washing was continued. This indicated probably the hydrolysis of an
unstable lead compound. Hydrogen sulphide was passed into the ether
solution mixed with water to remove the lead. Lead sulphide was filtered
off, and the ether was evaporated. A small portion of the tar residue in
alcoholic solution gave a color reaction with ferric chloride. As this
may have been due to traces of lead gallate dissolved in the extraction
with ether and afterwards decomposed by hydrogen sulphide, the main
portion of the tar was redissolved in ether and shaken with water until
it no longer reacted with ferric chloride. The ether was then evaporated
and a soft, black, poisonous tar or gum of uniform consistency was left
which was shown by tests to be free from gallic acid and lead. These
experiments showed that some of the poison was precipitated as a lead
compound soluble in ether and some was brought down mechanically in the
free state. To see if the extraction with ether in the Soxhlet apparatus
was complete, the residue in the thimbles was decomposed by hydrogen
sulphide and shaken with ether. The dark colored ether solution was
freed from gallic acid by shaking with water and dilute sodium carbonate
solution, and was evaporated. A small quantity of tar was obtained which
was added to the main portion.

A solution of the poisonous tar in 95 per cent. alcohol did not reduce
Fehling solution and did not give a precipitate with lead acetate except
the separation of a small quantity of tar, which was not a lead
compound. The lead compound of the poison was apparently soluble in 95
per cent. alcohol as well as in ether, for it would not precipitate in
this medium, although it was found in the original precipitate by lead
acetate. The alcoholic solution of the tar became turbid on diluting
with water.

In order to see if the poison is volatile with vapor of acetic acid,
since this acid is found in the plant and it is thought by some that the
poison is volatile, a portion of the tar was distilled under diminished
pressure with acetic acid. It was soluble to some extent in the acid.
The temperature did not go higher than 55° during the distillation. A
tube containing cotton wet with sweet oil was placed between the
receiver and the water suction so that the uncondensed vapors would have
to pass through the cotton. This cotton was rubbed on the skin and was
not poisonous. The yellow distillate collected in the receiver was also
tested and was not poisonous.


HYDROLYSIS OF THE POISON.

About 5 grams of the poisonous tar free from gallic acid and sugar was
dissolved in alcohol, and dilute (2 per cent.) sulphuric acid was added.
Some of the tar separated out on diluting the alcohol with the acid. The
mixture was heated on a water bath during work hours for four days. A
purple and green fluorescent solution was formed, though much tar was
left apparently unchanged. The alcohol was evaporated off and the
solution was filtered from tar. The fluorescent filtrate was shaken
with ether, by which the green substance was removed, leaving the
solution purple. The ether left, on evaporation, a small quantity of a
green substance having a pleasant ester odor. It was not further
examined. A portion of the purple solution was exactly neutralized with
sodium carbonate. This solution gave a blue-black color with ferric
chloride which became red on addition of another drop of sodium
carbonate, indicating gallic acid. It also reduced Fehling solution.

Another portion of the purple solution was made alkaline with sodium
carbonate. A reddish-brown flocculent precipitate was formed and was
filtered off. The filtrate did not give any color with ferric chloride,
but it reduced Fehling solution. It also gave the test for rhamnose with
alpha-naphthol.

The main portion of the purple solution was made alkaline with sodium
carbonate; the precipitate was filtered off and dissolved in acetic
acid. This solution was yellow and gave a reaction with ferric chloride
similar to that of gallic acid. The filtrate from the precipitate by
sodium carbonate was concentrated by evaporation until sodium sulphate
began to crystallize out. Alcohol was added to precipitate the sodium
sulphate completely, the mixture was heated and filtered. The alcoholic
filtrate was concentrated to a syrup which reduced Fehling solution and
gave the characteristic tests for rhamnose already described. By this
hydrolysis, the tar was split up into rhamnose and some form of gallic
acid which could be precipitated by sodium carbonate. This compound,
whose acetic acid solution was yellow, probably contained fisetin also.
The reason for this last statement will appear from the following
experiment:


DECOMPOSITION OF THE POISON WITH ACETIC ACID.

A portion of the poisonous tar was heated in an open dish with strong
acetic acid. The tar seemed to be decomposed to some extent, giving a
yellow substance. Acetic acid was added from time to time as it
evaporated. After several evaporations, water was added, the mixture was
heated to boiling and filtered. This filtrate No. 1 will be mentioned
later. The residue in the dish consisted of undecomposed tar and an
olive-green flaky substance. This substance was heated with a fresh
portion of glacial acetic acid. Water was added, and the mixture was
boiled and filtered. The filtrate had a deep yellow color suggesting
fisetin. It was shaken out with ethyl acetate which became colored
yellow. A portion of the ethyl acetate solution gave an orange red
precipitate with lead acetate showing the presence of fisetin. The ethyl
acetate was removed from the remainder of the solution by evaporation
and the yellow residue was taken up in alcohol. This alcoholic solution
gave the characteristic reactions for fisetin with stannous chloride,
with potassium hydroxide, with ferric chloride and with Fehling
solution.

Filtrate No. 1 obtained by heating the poisonous tar with acetic acid
and hot water as described above was investigated as follows: A portion
of it gave a reddish colored precipitate with sodium carbonate as in the
case when the tar was hydrolyzed with sulphuric acid. The remainder was
nearly neutralized with sodium carbonate and lead acetate was added in
excess to remove gallic acid. The excess of lead was removed by
sulphuric acid, and the sulphuric acid was removed by barium carbonate.
The solution on evaporation reduced Fehling solution to some extent, but
a white precipitate was also formed.

In this experiment, gallic acid and fisetin and probably sugar were
formed by decomposition of the poisonous gum with acetic acid, the acid
found in the plant by Pfaff. The presence of free gallic acid, fisetin
and rhamnose in the plant can therefore be explained by the natural
hydrolysis of a complex gum or tar or a constituent thereof. The
poisonous property is lost in the general rearrangement which takes
place during hydrolysis.

The poisonous tar was not hydrolyzed by boiling with a dilute solution
of sodium carbonate.

It was found, as has been stated elsewhere, that the lead compound of
the poison could not be precipitated in 95 per cent. alcohol. Further
experiments, however, showed that on extracting the poisonous gum with
50 per cent. alcohol, a portion of it dissolved, and this solution gave
a precipitate with lead acetate which was a true lead compound. The
remainder of the purified tar (about 10 gm.) was treated with 50 per
cent. alcohol and filtered. Very little dissolved in alcohol of this
strength, but on addition of lead acetate in 50 per cent. alcohol to the
solution, a light colored precipitate was formed, which became dark on
standing. It was filtered off, washed free from lead acetate, decomposed
by hydrogen sulphide, and shaken out with ether. The ether left, on
evaporation, a yellow resinous substance having a faint odor like
garlic. By drying in a desiccator, a small quantity of a solid yellow
resin was obtained which was completely soluble in alcohol. A very small
drop of this solution applied to the skin on the end of a glass rod
which had been drawn out to a point caused an eruption in about
thirty-six hours. Following the nomenclature used by Maisch and Pfaff,
this substance will be designated as _Toxicodendrin_, the ending "in"
indicating its glucoside nature.

The filtrate from the lead precipitate just described was freed from the
excess of lead acetate by hydrogen sulphide, was tested for poison, and
was found to be poisonous, showing that the precipitation by lead
acetate was not complete even in 50 per cent. alcohol. On spontaneous
evaporation of the solution, a yellow, sweet smelling resin was left.

A portion of the alcoholic solution of the toxicodendrin gave a dark
coloration with ferric chloride, did not reduce Fehling solution and was
slightly acid to litmus.

To see whether the toxicodendrin could be hydrolyzed, the remainder was
dissolved in alcohol and dilute sulphuric acid was added. A fine, white
precipitate was formed at once which rose to the surface on standing as
a light flocculent substance. The mixture was heated for several days on
a water bath, filtered from unhydrolyzed resin and the filtrate was
neutralized and concentrated in the way already described. The solution
obtained reduced Fehling solution. Not enough was obtained for further
sugar tests, but all the hydrolysis experiments point to the conclusion
that the poisonous substance is a rhamnoside, and is the source of the
sugar in the plant.

The reaction with ferric chloride observed whenever a lead compound of
the poison is decomposed by hydrogen sulphide may be explained by the
formation of traces of gallic acid or fisetin through the action of the
weak acids present.

The supply of purified poisonous tar having been exhausted in the
preceding experiments, further study of the active principle is
postponed until more can be prepared. It is highly desirable to
investigate the white precipitate formed by addition of sulphuric acid
to an alcoholic solution of the toxicodendrin.


OXIDATION OF THE PURIFIED TAR WITH NITRIC ACID.

When the purified poisonous material (p. 32) was extracted with 50 per
cent. alcohol, only a small quantity was dissolved as was stated above.
The insoluble residue was treated with fuming nitric acid. Violent
reaction took place at once with copious evolution of red fumes and
heat. When the reaction was over, a sticky red gummy mass was left which
was slightly soluble in cold water and readily soluble in warm alcohol.
The water extract was yellow, and the alcoholic solution was red. That
the water extract contained picric acid was shown by the following
experiments:

     (1) A portion was gently warmed with a few drops of a strong
     solution of potassium cyanide and two drops of sodium
     hydroxide. The red color of potassium isopurpurate was
     formed.

     (2) A portion of the water solution was heated with glucose
     and a few drops of sodium hydroxide. The deep red color of
     picraminic acid was produced.

     (3) A few drops of an ammoniacal solution of copper sulphate
     was added to the water extract. A yellow-green precipitate
     was formed.

     (4) The water extract dyed silk, but did not dye cotton
     cloth.


DISTILLATION OF THE TAR WITH SODA LIME.

About 25 gm. of the tar left after extracting the original material with
hot water was dissolved in ether and poured into a glass retort
containing soda lime. The ether was distilled out, leaving the tar
intimately mixed with the soda lime. The retort was then gradually
heated. Vapors and liquid were given off, both of which turned red
litmus blue and had a strong odor like tobacco smoke. No odor of ammonia
was detected.[45] At the high temperature of the triple burner, a
semi-solid, red, greasy substance collected in and closed the condenser
tube. This substance had the same powerful odor as the liquid portion of
the distillate. The clear, watery portion of the distillate was
separated from the thicker parts, and was found to contain pyrrol and
pyridine derivatives by the following characteristic tests:

     (1) Wood moistened with hydrochloric acid was turned red by
     it.

     (2) Colorless fumes were formed when brought near
     hydrochloric acid; mixed with hydrochloric acid, a red
     insoluble substance was formed.

     (3) It precipitated the hydroxides of iron, gave a light
     blue precipitate with copper sulphate, and a white
     precipitate with mercuric chloride.

The greasy, semi-solid mass was extracted with 10 per cent. hydrochloric
acid and filtered. On addition of a solution of mercuric chloride to the
red filtrate, a brown flocculent precipitate was formed. It was filtered
off and distilled with caustic soda, but the distillate did not contain
pyridine.


POTASSIUM PERMANGANATE AS A REMEDY FOR RHUS POISONING.[46]

In the early stages of this work some experiments were made to see if
potassium permanganate could be used to purify the lead precipitate by
oxidizing the tar brought down in precipitation. It was found that the
permanganate attacked the lead precipitate as well as the other organic
matter in the vessel. This fact and the well-known value of permanganate
in treating skin diseases, its use as an antidote for some kinds of
alkaloid poisoning,[47] as an antidote given to cattle poisoned by
plants,[48] and as an antidote for snake bites,[49] suggested its use as
a remedy for Rhus poisoning. Maisch[50] mentioned that he had used it
with success, but it never came into general use, probably on account of
its staining the skin and clothing. In carrying out this work abundant
opportunities for testing its value as a remedy for the dermatitis
caused by poison ivy were afforded by many cases of accidental and
intentional poisoning. The best example of the latter was obtained with
the ether solution from the extraction of the lead precipitate in the
Soxhlet apparatus (page 28). After removing the ether, a small drop of
the residue was applied to the wrist as described. An itching red spot
about the size of a dime was noticed in thirty-six hours, and it
steadily increased in size. Nearly two days after the application of the
poison, a dilute solution of potassium permanganate containing a little
caustic potash was rubbed into the spot until the pimples were
destroyed. A little black spot was left wherever there had been a
pimple, showing that the permanganate had been reduced to oxide in the
skin. The place was washed and nothing more was thought of it until the
morning following, when it was noticed that the wrist had commenced to
swell during the night, and the characteristic watery secretion was
running from the poisoned spot. More permanganate solution was applied
without potash and the wrist was bandaged, thinking that this would
prevent the spreading of the eruption, but it really facilitated
spreading by becoming saturated with the poisonous fluid and keeping it
in contact with a larger surface of skin. In the meantime the swelling
and inflammation had extended nearly to the elbow. The arm now had the
appearance of having been bitten by a snake. To reduce the swelling it
was immersed in hot water. This seemed to bring out the eruption very
quickly and the blisters were treated with permanganate as fast as they
appeared. The swelling was reduced, but returned during the night. On
the evening following, the forearm was immersed in a bowl of hot
permanganate solution containing a little caustic potash. The solution
was kept as hot as could be borne for about half an hour. After this
bath, the poison was completely oxidized, for the swelling was reduced
and did not return, nor was there any fresh eruption. What appeared to
be a severe case of poisoning was thus cured very quickly. The use of
hot water not only reduces the swelling, but also helps to destroy the
poison. The action of permanganate is also more rapid at high
temperatures.

The oxidizing power of permanganate, as is well known, is greater in
acid solution than in alkaline, five atoms of oxygen being available in
the former and three in the latter, according to these equations:

    2 KMnO_{4} + 3 H_{2}SO_{4} = K_{2}SO_{4} + 2 MnSO_{4} + 3 H_{2}O + 5 O.
    2 KMnO_{4} + H_{2}O = 2 MnO_{2} + 2 KOH + 3 O.

Permanganate was used as a remedy in some cases mixed with dilute
sulphuric acid, and in others, with zinc sulphate; also with lime water.
It was found to be satisfactory whether used alone or with any of the
substances mentioned, provided it was well rubbed into the skin. The
concentration of the solution used was varied according to the location
and condition of the eruption. Where the skin was thin or already
broken, dilute solutions (one per cent.) were used. In one case, the
eruption appeared in the palm of the hand where the skin was so thick
that it was necessary to open it before the remedies could reach the
poison. The difficulty of getting the remedy in contact with the poison
in the skin is the reason why the eruption is hard to cure.

The remedy most commonly used for this eruption is an alcoholic solution
of lead acetate. This remedy is unsatisfactory for the reason that its
action consists in depositing an unstable lead compound of the poison in
the skin where the conditions of moisture and temperature are favorable
for its decomposition, liberating the poison with all its irritant
properties. Moreover, alcoholic preparations should not be used because
the alcohol dissolves the poison and, on evaporation, leaves it spread
over a larger surface like a varnish. Potassium permanganate, however,
oxidizes the poison completely. The only objection to the use of
permanganate of which the writer is aware is that it stains the skin.
The stain can be removed by vigorous scrubbing with soap, or it will
wear off gradually in a few days. It can be removed at once by certain
acids, but these should not be used by persons not familiar with their
action.

With the knowledge of the facts mentioned, many solutions were tested
for poison by applying them to the skin, and when an eruption appeared,
it was cured quickly and permanently by rubbing in a permanganate
solution, usually mixed with dilute sulphuric acid.

FOOTNOTES:

[16] Nitrogen was found very readily by the soda lime test in the tar
left after extracting the original material with 50 per cent. alcohol,
but was not found by the Lassaign test.

[17] Stevens. Amer. Jour. Pharm. 77, 255, June, 1905.

[18] Whenever it is stated in this paper that a solution was poisonous
or not poisonous, the test was made by the writer upon himself.

[19] Liebig's Annalen, CXI, p. 215.

[20] Über Mategerbstoff, p. 20.

[21] Bull. Soc. Chim. (II), Vol. 2, 95 (1864).

[22] Berichte 19, 1735 (1886).

[23] Jour. Chem. Soc. 71, 1194 (1897).

[24] Berichte 19, 1740.

[25] Ibid. 1747; Annalen, 112, 97.

[26] Biochem. Pflan. II, 521.

[27] Ann. de Chim. et de Phys., 6th Series, XXII, 76 (1891).

[28] Treatise on Chem., Vol. III, Pt. III, 492.

[29] Les Sucres; Chem. der Zuck.; Biochem. der Pflan.

[30] Chem. Zeit. 23, Rep. 177.

[31] Loc. cit. 1, 209.

[32] On standing several weeks, a small quantity of tar separated out on
the walls of the vessel, also a brown precipitate which was filtered
off, suspended in water, and hydrogen sulphide was being passed in when
an accident occurred and it was lost.

[33] "By warming with alkalies or barium hydroxide, rhamnose is colored
yellow." Chem. der Zuck. I, 177.

[34] Ibid. 188.

[35] Ibid.

[36] Rayman, Sur L'Isodulcite, _Bull. Soc. Chim._ 47, 668 (1887).

[37] Acides Gummiques.

[38] Berichte XX, pp. 1089, 1091, 1188, 2566.

[39] Ann. de Chim. et de Phys. (6) XXII, 93 (1891).

[40] Biochem. der Pflan. I, 210.

[41] Comptes rendus CXV, 892.

[42] Amer. Chem. Jour. 28, 370.

[43] Amer. Jour. Pharm. 77, 255 (June, 1905); 78, 53 (Feb., 1906).

[44] A wax obtained from _Rhus succedanea_ was shown by Stahmer to
contain palmitic acid and glycerol in the form of glycerol palmitate.
_Annalen_ 43, 343, (1842).

[45] See Amer. Jour. Pharm. 77, 256.

[46] This section is added in the hope that it may be of use to others
who are subject to this form of poisoning.

[47] Moor, N. Y. Med. Rec. 45 (1894), 200.

[48] Bull. No. 26, U. S. Dept. Agr., Div. of Bot. 47.

[49] Lacerda, Comptes rendus 93 (1881) 466-469.

[50] Amer. Jour. Med. Sci. 52 (1866), 285.




SUMMARY.


Leaves and flowers of the poison ivy plant were extracted with ether and
the ether was removed by evaporation. In the residue, the following
substances were found and studied: gallic acid, fisetin, the sugar
rhamnose, and a poisonous tar, gum, or wax.

The lead compound of the poison was soluble in ether; this fact gave a
means of separating the poisonous substance from the non-poisonous
matter in one operation.

The poison was not volatile with vapor of acetic acid, or with vapor of
alcohol.

The poisonous tar or wax was decomposed by acids and yielded gallic
acid, fisetin, and rhamnose, showing the probable source of these
compounds in the plant, and indicating that the poison is a complex
substance of a glucoside nature.

It was found that a portion of the poisonous substance could be
precipitated by lead acetate from a solution of the purified tar in 50
per cent. alcohol.

All cases of poisoning developed on the writer were easily cured with
potassium permanganate.

The following method is suggested for obtaining the poisonous substance
from the plant: Extract the plant with alcohol, filter, and precipitate
at once with lead acetate. Wash the precipitate, dry, and extract with
ether in Soxhlet extractors (loosely filled). Combine the ether
extracts, mix with water, and pass in hydrogen sulphide. Separate the
water and the ether solution, and filter the latter. Wash the ether
solution thoroughly by shaking with water, and then evaporate at a low
temperature.




BIOGRAPHY.


William Anderson Syme, the author of this dissertation, was born in
Raleigh, N. C., on July 11, 1879. He was prepared for college at the
Raleigh Male Academy, entered the North Carolina College of Agriculture
and Mechanic Arts in 1896, and was graduated in 1899 with the degree B.
S. He was an Instructor in Chemistry at the same College from January
1st, 1900, until June, 1903, when he received the degree M. S. for
graduate work. In October following, he entered Johns Hopkins University
as a graduate student in Chemistry, and was awarded one of the North
Carolina Scholarships. His minor subjects are Physical Chemistry and
Biology.