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    _A HISTORY OF THE SCIENCES_


    HISTORY
    OF
    CHEMISTRY


    BY
    SIR EDWARD THORPE,

    C.B., LL.D., F.R.S.

    AUTHOR OF “ESSAYS IN HISTORICAL CHEMISTRY,” “HUMPHRY DAVY:
    POET AND PHILOSOPHER,” “JOSEPH PRIESTLEY,” ETC., ETC.


    TWO VOLUMES


    I.

    From the Earliest Times to the Middle of the
    Nineteenth Century


    _WITH ILLUSTRATIONS_


    G. P. PUTNAM’S SONS
    NEW YORK AND LONDON
    The Knickerbocker Press
    1909




    COPYRIGHT, 1909, BY
    G. P. PUTNAM’S SONS


    This series is published in London by
    THE RATIONALIST PRESS ASSOCIATION, LIMITED




PUBLISHERS’ NOTE


A HISTORY OF THE SCIENCES has been planned to present for the
information of the general public a historic record of the great
divisions of science. Each volume is the work of a writer who is
accepted as an authority on his own subject-matter. The books are
not to be considered as primers, but present thoroughly digested
information on the relations borne by each great division of science
to the changes in human ideas and to the intellectual development
of mankind. The monographs explain how the principal scientific
discoveries have been arrived at and the names of the workers to whom
such discoveries are due.

The books will comprise each about 200 pages. Each volume will contain
from 12 to 16 illustrations, including portraits of the discoverers and
explanatory views and diagrams. Each volume contains also a concise but
comprehensive bibliography of the subject-matter. The following volumes
will be issued during the course of the autumn of 1909.


  =The History of Astronomy.=

    By GEORGE FORBES, M.A., F.R.S., M. Inst. C.E.; author of _The
      Transit of Venus_, etc.

  =The History of Chemistry: Vol. I. circa 2000 B.C. to 1850 A.D.
    Vol. II. 1850 A.D. to date.=

    By SIR EDWARD THORPE, C.B., LL.D., F.R.S., Director of the
      Government Laboratories, London; Professor-elect and Director
      of the Chemical Laboratories of the Imperial College of Science
      and Technology; author of _A Dictionary of Applied Chemistry_.

_To be followed by_:

  =The History of Geography.=

    By Dr. JOHN SCOTT KELTIE, F.R.G.S., F.S.S., F.S.A., Hon. Mem.
      Geographical Societies of Paris, Berlin, Rome, Brussels,
      Amsterdam, Geneva, etc.; author of _Report on Geographical
      Education_, _Applied Geography_.

  =The History of Geology.=

    By HORACE B. WOODWARD, F.R.S., F.G.S., Assistant-Director of
      Geological Survey of England and Wales; author of _The Geology
      of England and Wales_, etc.

  =The History of Anthropology.=

    By A. C. HADDON, M.A., Sc.D., F.R.S., Lecturer in Ethnology,
      Cambridge and London; author of _Study of Man_, _Magic and
      Fetishism_, etc.

  =The History of Old Testament Criticism.=

    By ARCHIBALD DUFF, Professor of Hebrew and Old Testament Theology
      in the United College, Bradford; author of _Theology and
      Ethics of the Hebrews_, _Modern Old Testament Theology_, etc.

  =The History of New Testament Criticism.=

    By F. C. CONYBEARE, M.A., late Fellow and Praelector of Univ.
      Coll., Oxford; Fellow of the British Academy; Doctor of
      Theology, _honoris causa_, of Giessen; Officer d’ Academie;
      author of _Old Armenian Texts of Revelation_, etc.


Further volumes are in plan on the following subjects:

  =Mathematics and Mechanics.=

  =Molecular Physics, Heat, Life, and Electricity.=

  =Human Physiology, Embryology, and Heredity.=

  =Acoustics, Harmonics, and the Physiology of Hearing, together with
    Optics Chromatics, and Physiology of Seeing.=

  =Psychology, Analytic, Comparative, and Experimental.=

  =Sociology and Economics.=

  =Ethics.=

  =Comparative Philology.=

  =Criticism, Historical Research, and Legends.=

  =Comparative Mythology and the Science of Religions.=

  =The Criticism of Ecclesiastical Institutions.=

  =Culture, Moral and Intellectual, as Reflected in Imaginative
    Literature and in the Fine Arts.=

  =Logic.=

  =Philosophy.=

  =Education.=




CONTENTS


  CHAPTER I                                                         PAGE

  THE CHEMISTRY OF THE ANCIENTS                                        1

    Egypt, the alleged birthplace of chemistry. Origin of the word
    “chemistry.” Chemical arts known to the ancients. Metallurgy
    of the ancients. Chemical products of the Chinese, Egyptians,
    Greeks, and Romans.


  CHAPTER II

  THE CHEMICAL PHILOSOPHY OF THE ANCIENTS                             19

    Ancient speculations as to the origin and nature of matter.
    Water the primal principle. Thales of Miletus. Persistency
    of his doctrine. Its influence on science. Theories of
    Anaximenes, Herakleitos, and Pherekides. Fire as the primal
    principle. The conception of four primal principles—fire,
    air, water, and earth. Deification of these by Empedocles.
    Plato and Aristotle. The doctrine of the four Elements.
    Influence of the Peripatetic Philosophy on science. Arabian
    science. Influence of the Moors in Spain. Atomic conceptions
    of Anaxagoras, Leukippos, and Demokritos. Germs of the atomic
    theory.


  CHAPTER III

  ALCHEMY                                                             28

    Influence of the Hellenic mind on the development of
    chemistry. Origin of the idea of the transmutation of
    metals. Philosophical foundation for the belief in alchemy.
    Alchemistic theory of the nature of metals. Origin of the
    conception of the Philosopher’s Stone. Geber. Association of
    alchemy with astrology. Rhazes. Avicenna. Chemical processes
    and substances known to the Arabian chemists. The Western
    Alchemists. Albertus Magnus. Roger Bacon. Raymond Lully.
    Arnoldus Villanovanus. Johannes de Rupecissa. George Ripley.
    Basil Valentine.


  CHAPTER IV

  THE PHILOSOPHER’S STONE                                             46

    Alchemy in the Middle Ages. Association of religion with
    alchemy by the Christian Church. Alleged nature of the
    Philosopher’s Stone. Its character described. Its power.
    The Universal Medicine. The Elixir of Youth. The Alkahest.
    Opponents of alchemy: Erastius, Conringius, and Kircher.
    “The Hermes of Germany”: Rudolph II. Christian princes who
    had dealings with alchemists. Fate of certain alchemists.
    Persistency of alchemy and hermetic societies. Lord Bacon on
    alchemy.


  CHAPTER V

  IATRO-CHEMISTRY                                                     57

    Theories of the iatro-chemists. Paracelsus. Doctrine of the
    _tria prima_. The Paracelsian harmonies. Libavius. Van
    Helmont. Sylvius. Willis. Services of iatro-chemistry
    to science. Influence of iatro-chemistry on technology.
    Agricola. Palissy. Glauber. Chemical products made known by
    the alchemists.


  CHAPTER VI

  “THE SCEPTICAL CHEMIST”: THE DAWN OF SCIENTIFIC CHEMISTRY           70

    The foundation of the Royal Society and other scientific
    academies. The appearance of “The Sceptical Chemist”: its
    attack on the doctrines of the Spagyrists. Boyle: his life
    and character. His services to learning. Kunkel. Becher.
    Mayow. Lemery. Homberg. Boerhaave. Stephen Hales.


  CHAPTER VII

  PHLOGISTONISM                                                       91

    Becher’s hypothesis of the _Terra Pinguis_. Its development
    into the theory of phlogiston. Stahl. Phlogiston, primarily
    a theory of combustion, becomes a theory of chemistry. Its
    general acceptance in Europe until the last quarter of the
    eighteenth century. Prominent phlogistians. Pott. Marggraf.
    Scheele: his discoveries. Duhamel. Macquer. Black: his
    essay on _Magnesia Alba_. Recognition of the individuality
    of carbon dioxide. Priestley: his life and character. His
    discoveries in pneumatic chemistry. His observations on
    the influence of vegetable life on the character of the
    atmosphere. Cavendish: his life and work. Discovery of
    composition of water. Influence of phlogistonism on the
    development of chemistry. Advances made during the period of
    phlogistonism.


  CHAPTER VIII

  LAVOISIER AND LA RÉVOLUTION CHIMIQUE                               109

    Downfall of phlogistonism. Lavoisier: his life and work. His
    death. _Le principe oxygine._ Principle of the conservation
    of matter. Chemistry a science of quantitative relations.
    Prominent anti-phlogistians. Berthollet. The _Statique
    Chimique_. Fourcroy. Vauquelin. Klaproth. Proust.


  CHAPTER IX

  THE ATOMIC THEORY                                                  123

    The atomic hypotheses of the ancients. Newton. Bergmann.
    Lavoisier. Richter. Stochiometry. John Dalton: sketch of his
    life and character. How he was led to his explanation of the
    laws of chemical combination. The _New System of Chemical
    Philosophy_. Reception of his theory by Davy and Wollaston.
    Berzelius: his life and work. His services to chemistry.
    First accurate series of atomic weight determinations.
    Avogadro. Prout’s hypothesis.


  CHAPTER X

  THE BEGINNINGS OF ELECTRO-CHEMISTRY                                140

    The Voltaic Pile. Electrolytic decomposition of water by
    Nicholson and Carlisle. Application of voltaic electricity
    to the decomposition of the alkalis by Davy. His life and
    work. Wollaston: his life and work. Electro-chemical system
    of Berzelius. Dualism. Berzelius reforms chemical notation
    and nomenclature. Gay Lussac: his life and work. Thénard: his
    life and work. Faraday and the law of definite electrolytic
    action.


  CHAPTER XI

  THE FOUNDATIONS OF ORGANIC CHEMISTRY                               154

    Nicolas Lemery divides chemistry into its two main branches
    of inorganic and organic chemistry. State of knowledge of
    products of organic origin during the early years of the
    nineteenth century. Animal chemistry. Doctrine of vital
    force. Wöhler’s synthesis of urea. Organic chemistry is the
    chemistry of the carbon compounds. Early attempts at organic
    analysis by Lavoisier, Berzelius, Gay Lussac, and Thénard.
    Liebig. Discovery of _isomerism_ and _allotropy_. Cyanogen.
    Theory of compound radicals. Etherin theory of Dumas and
    Boullay. Memoir of Liebig and Wöhler on oil of bitter
    almonds. Benzoyl theory. Investigation of alkarsin by Bunsen.
    Cacodyl. Discovery of zinc ethyl by Frankland.


  CHAPTER XII

  THE RISE OF PHYSICAL CHEMISTRY                                     170

    Relations of chemistry to physics. Relations of heat
    to chemical phenomena. Improvements in the mercurial
    thermometer. Newton. Shuckburgh. Brooke Taylor. Cavendish.
    Black. Discovery of latent heat by Black. Discovery of
    specific heat. Experiments of Lavoisier and Laplace. Law
    of Dulong and Petit: its value in determining atomic
    weights. Specific heat of compounds. Neumann. Discovery of
    isomorphism by Mitscherlich. Foreshadowing of the kinetic
    theory of gases. Discovery of the law of gaseous diffusion by
    Graham. Liquefaction of gases. Monge and Clouet. Northmore.
    Faraday. Value of a knowledge of weights of unit volumes of
    gases in determining their molecular weights. Methods of
    vapour-determination by Dumas and Gay Lussac. Dalton and
    Henry’s law of gaseous solubility. Work of Schröder and Kopp
    on volume relations of liquids and solids. Connection between
    the chemical nature of a liquid and its boiling-point.

  BIBLIOGRAPHY                                                       183

  INDEX                                                              187




HISTORY OF CHEMISTRY




CHAPTER I

THE CHEMISTRY OF THE ANCIENTS


Chemistry, as an art, was practised thousands of years before the
Christian era; as a science, it dates no further back than the middle
of the seventeenth century. The monumental records of Egypt and the
accounts left us by Herodotus and other writers show that the ancient
Egyptians, among the earliest nations of whom we have any records,
had a considerable knowledge of processes essentially chemical in
their nature. Their priests were adepts in certain chemical arts, and
chemical laboratories were occasionally attached to their temples, as
at Thebes, Memphis, and Heliopolis. It is to be supposed, too, that
in a cultured class, as the priesthood undoubtedly was, there would
be now and again curious and ingenious persons who would speculate on
the nature and causes of the phenomena which they observed. But there
is no certain evidence that the Egyptians ever pursued chemistry
in the spirit of science, or even in the manner in which they and
the Chaldæans followed, for example, astronomy or mathematics. The
operations of chemistry as performed by them were of the nature of
manufacturing processes, empirical in character and utilitarian in
result. It was comparatively late in the world’s history that men were
found willing to occupy themselves in chemical pursuits in order to
gain an insight into the nature of chemical change, and to learn the
causes and conditions of its action.

Although we have cited the ancient Egyptians as practising the chemical
arts, there is no proof that these arts actually originated with them.
China, India, Chaldæa have each in turn been regarded as the birthplace
of the various technical processes from which chemistry may be said to
have taken its rise. Nevertheless, it is mainly from Egyptian records,
or from writings avowedly based on information from Egyptian sources,
that such knowledge as we possess of the earliest chemical processes is
derived. It is significant that the word “chemistry” has its origin in
_chemi_, “the black land,” the ancient name for Egypt. The art itself
was constantly spoken of as the “Egyptian art.”

“The word _chemistry_,” says Boerhaave in the Prolegomena of his _New
Method of Chemistry_ (Shaw and Chambers’s translation, London, 1727),

  in _Greek_ should be wrote χημíα, and in _Latin_ and _English_
  _chemia_ and _chemistry_; not as usual, _chymia_ and _chymistry_.

  The first author in whom the word is found is _Plutarch_, who
  lived under the Emperors _Domitian_, _Nerva_, and _Trajan_. That
  philosopher, in his treatise of _Isis_ and _Osiris_, takes occasion
  to observe that _Egypt, in the sacred dialect of the country, was
  called by the same name as the_ black _of the eye_—viz., χημíα—by
  which he seems to intimate that the word _chemia_ in the _Egyptian_
  language signified black, and that the country, _Egypt_, might take
  its denomination from the _blackness_ of the soil.

  But [continues Boerhaave] the etymology and grammatical
  signification of the name is not so easily dispatched. The critics
  and antiquaries, among whom it has been a great subject of inquiry,
  will not let it pass without some further disquisition. Instead of
  _black_, some will have it originally denote _secret_, or _occult_;
  and hence derive it from the _Hebrew_ _chaman_, or _haman_—a
  _mystery_, whose radix is _cham_. And, accordingly, _Plutarch_
  observes that _Egypt_, in the same sacred dialect, is sometimes
  wrote in _Greek_ χαμíα—_chamia_; whence the word is easily deduced
  further from _Cham_, eldest son of Noah, by whom Egypt was first
  peopled after the deluge, and from whom, in the Scripture style,
  it is called the _land of Cham_, or _Chem_. Now, that _chaman_,
  or _haman_, properly signifies _secret_ appears from the same
  _Plutarch_, who, mentioning an ancient author named _Menethes
  Sibonita_, who had asserted that _Ammon_ and _Hammon_ were used
  to denote the god of _Egypt_, _Plutarch_ takes this occasion to
  observe that in the _Egyptian_ language anything secret or occult
  was called by the same name, ἅμμον—_Hammon_.... Lastly, the learned
  _Bochart_, keeping to the same sense of the word, chooses to derive
  it from the _Arabic_ _chema_, or _kema_—to _hide_; adding that
  there is an _Arabic_ book of secrets called by the same name _Kemi_.

From the whole of which Boerhaave gathers that chemistry was thus
originally denominated because it was considered of old as “not fit to
be divulged to the populace, but treasured up as a religious _secret_.”

If we are to credit Zozimus the Panopolite, who is said to have lived
about the beginning of the fifth century, there were sound reasons for
thus treasuring up chemistry as a religious secret, since, as it sprang
from the _pretium amoris_, its origin was not too reputable. “What the
divine writings relate is that the angels, enflamed with the desire
of women, instructed ’em in all the works and mysteries of nature.
For which indiscretion they were excluded heaven, as having taught
men things unfit for ’em to know.” And Scaliger asserts that “Hermes
testifies as much; and all our learning, both open and occult, confirms
the account.” But who Hermes was, adds that author, is hard to say, for
none of his writings has survived to our age, “that lately published in
Italy under the name of _Hermes Trismegistus_ being a manifest forgery.”

This legend of the “feministic” origin of chemistry is in reality much
older than the fifth century of our era, and is but a variant of that
which, according to Jewish writers, led to the expulsion of man from
Paradise. A similar myth was current among the Phœnicians, Persians,
Greeks, and Magi. We trace it in the legend of Sibylla, who demanded,
as the price of her favour to Phœbus, not only length of years,
but a knowledge of the divine _arcanum_. Some of the ecclesiastics
who elaborated these myths are particular in their accounts of the
mysteries thus imparted. They included the use of charms, a knowledge
of gold and silver and precious stones, the art of dyeing, of painting
the eyebrows, etc.—the kind of _arcana_, in fact, which women in all
ages were presumably most keen to know. It is, however, significant
that in all allusions to _chemia_, even after the translation of
the seat of the Roman Empire to Constantinople, it is implied that
a knowledge of it was a sacred mystery to be known only to the
priesthood, and jealously guarded by them. It was characteristic of
writers who had affixed an eternal stigma on Eve to make the sex in
general answerable for an illicit knowledge of “things unfit for men to
know.”

For, in reality, chemistry originated with men, and it was not so much
in the love of women as of wine that it took its rise.

The manufacture of _alcohol_ by processes of fermentation is probably
the oldest of the chemical arts. The word _wine_ means, in fact, a
_product of fermentation_. Mosaic history relates that Noah, soon
after he got to dry land, “planted a vineyard and drank of the wine,”
with results that would appear to show that the potency of wine
was not unfamiliar to him. Diodorus Siculus, who studied Egyptian
antiquities when Egypt was a Roman province, states that the ancient
Egyptians ascribed the origin of wine to Osiris. It was a sacrificial
offering even in the earliest times, as was bread. Wine seems to have
been prepared by the Chinese as far back as the time of the Emperor
Yü, _circa_ 2220 B.C. Beer was manufactured in Egypt in the time of
Senwosret III. (Sesostris) B.C. 1880.

The Egyptians were skilled in dyeing and in the manufacture of
leather, and in the production and working of metals and alloys. They
were familiar with the methods of tempering iron. They made glass,
artificial gems, and enamels. The oldest known enamel was found as an
amulet on the Egyptian Queen Aahotep (1700 B.C.), and glass beads were
made before the time of Thutmosis III. (1475 B.C.). The Jews knew of
gold, silver, copper, iron, lead, and tin. Indeed, it is through them
and the Phœnicians, who were among the earliest of traders, that Europe
was gradually made acquainted with many technical products of Eastern
origin.

The beginnings of the art of extracting and working of metals are
lost in the mists of antiquity; the chemistry of metals, indeed, has
been said to be almost coeval with mankind. Diodorus Siculus found
traditions in Egypt as to the first inventor of metallurgical processes
identical with that of the son of Lamech and Zillah, Tubal-cain, or
Tuval-cain, of the Hebrews—the Vulcan of the Romans.

_Gold_ was undoubtedly one of the earliest metals to be made use of by
men, as it probably was one of the first to be discovered. It occurs
free in nature, and is met with in many rocks and in the sands of
rivers. Its colour, lustre, and density would early attract attention
to it; and its malleability and ductility and the ease with which it
could be fashioned, together with its unalterability, would render it
valuable. Ethiopian and Nubian gold were known from the earliest times,
and quartz crushing and gold washing were practised by the Egyptians.
Representations of these processes have been found on Egyptian
tombs dating from 2500 B.C. Gold-wire was used by the Egyptians for
embroidery, and they practised plating, gilding, and inlaying as far
back as 2000 B.C.

_Silver_ also was employed by them, and appears, like gold, to have
been coined into money. It was originally known as “white gold.”
Some of the oldest coins in existence are alloys of silver and gold,
obtained probably by the fusion of naturally occurring argentiferous
gold, such as the pale gold of the Pactolus. Such an alloy was termed
_electrum_, from its resemblance in colour to amber.

_Copper_ is also found to a limited extent in the metallic state, but
probably the greater part of that used by the ancients was obtained
from its ores, which are comparatively abundant and readily smelted.
It was also used for coinage by the Egyptians, and was fashioned by
them into a variety of utensils and implements. The older writers drew
no clear distinction between copper, bronze, and brass, and the terms
designating them—_æs_ and χαλκός—are frequently employed; as by Pliny,
indiscriminately. The statement in Deut. viii. 9—“Out of whose hills
thou mayest dig brass”—obviously cannot mean an alloy of copper and
zinc, since this does not occur naturally.

Pure copper is too soft a metal to be used for swords and cutting
instruments, but copper ores frequently contain associated metals, as,
for example, tin, which would confer upon the copper the necessary
hardness to enable it to be fashioned into weapons. Such copper would
be of the character of bronze, and it was known to the early workers
that the nature of the metal was greatly modified by the selection
of ores from particular localities. It was comparatively late in the
metallurgical history of copper that bronze was produced by knowingly
adding tin to the metal.

Copper was largely used by the Romans, who obtained it from Cyprus; it
was known to them as _æs Cyprium_, and eventually _Cuprum_, whence we
obtain the chemical symbol Cu. What the Romans called _æs_ was found
also at Chalkis, in Eubœa, whence χαλκός, the Greek word for copper.

_Aurichalcum_, or golden copper—that is, brass—was well known to the
early workers in copper, and was made in Pliny’s time by heating
together copper, cadmia (calamine), and charcoal.

Bell metal was employed by the Assyrians, and bronze was cast by the
Egyptians for the manufacture of mirrors, vases, shields, etc., as far
back as 2000 B.C. Statuary bronze, largely used by the Romans, usually
contained more or less lead.

_Tin_, which was also known to the early Egyptians, would appear to
have been first obtained from the East Indies, and to have been known
under the Sanscrit name of _Kastîra_ (_Kâs_, to shine), whence we have
the Arabic word for tin, _Kàsdir_, and the Greek κασσίτερος, used by
Homer and Hesiod. Tin ores are found in Britain (Cornwall), and were
brought thence by the Phœnicians. The group of islands, including the
Scilly Islands and the larger island to the east (Britain), was known
to the Romans as the _Insulæ Cassiterides_.

Pliny states that the tin is found in grains in alluvial soil, from
which it is obtained by washing; but he gives no description of the
method of smelting. The Latin word for tin was _stannum_; it was also
known as _plumbum album_, in contradistinction to lead, which was
called _plumbum nigrum_. Tin was used by the Romans for covering the
inside of copper vessels, and was also occasionally employed in the
construction of mirrors.

_Lead_ was well known to the Egyptians. In Pliny’s time it was mainly
procured from Spain and from Britain (Derbyshire). Leaden pipes were
used by the Romans for the conveyance of water, and sheet lead was
employed by them for roofing purposes. The Romans were also aware of
alloys of lead and tin. _Argentarium_ was composed of equal parts of
lead and tin; _tertiarium_, used as a solder, consisted of two parts of
lead and one part of tin.

_Iron_, although now the most important of the common metals, was not
in general use until long after the discovery of gold, silver, and
copper. This was probably due to the fact that, although its ores
are relatively abundant and widely distributed, its extraction as a
metal demanded greater skill and more appliances than were possessed
by the earlier races. Metallic iron was, however, well known to the
Egyptians, who employed it in the manufacture of swords, knives,
axes, and stone-chisels, both as malleable iron and as steel. Steel
was also known to the Chinese as far back as 2220 B.C., and they were
acquainted with the methods of tempering it. The good quality of
Chinese steel caused it to be highly prized by Western nations. The
earliest people to smelt iron are supposed to have been the Chalybes, a
nation inhabiting the neighbourhood of the Black Sea; it is from them
that the ancient name for steel—_chalybs_—is derived, and also our word
“chalybeate.”

_Mercury_ has long been known, but there is no evidence that the
ancient Egyptians were aware of its existence, or it would probably
have been mentioned by Herodotus. It was familiar to Aristotle, and
its mode of manufacture from cinnabar is described by Theophrastus
(320 B.C.), who terms it “liquid silver.” Processes of amalgamation
were known to Pliny, who notes the readiness with which mercury
dissolves gold. Pliny appears to distinguish the native metal found
in Spain, which he terms _argentum vivum_ (quicksilver), from that
obtained by sublimation or distillation from cinnabar, which he calls
_hydrargyrum_, from which we get the chemical symbol for mercury Hg.

A considerable number of metallic compounds were known to the ancients,
and were employed by them as medicines and as pigments. The oxides
of copper, known as _flos æris_, and _scoria æris_, obtained by
heating copper bars to redness and exposing them to air, were used as
escharotics. Verdigris, or _ærugo_, was made by the same methods as
now. Blue vitriol, or _chalcantum_, is described by Pliny, who says
that the blue transparent crystals are formed on strings suspended in
its solution.

_Chrysocolla_, malachite, or copper carbonate, was used as a green
pigment. The blue κύανος of the Greeks, or _cœruleum_ of the Romans,
was obtained by fritting together alkali, sand, and oxide of copper.
_Botryitis_, _placitis_, _onychitis_, _ostracitis_, were varieties of
_cadmia_ or oxide of zinc, obtained by calcining calamine, and were
used in the treatment of ulcers, etc. _Molybdena_, which was the Latin
name for litharge, was employed externally as an astringent and in the
manufacture of plaster. The lead plaster employed by Roman surgeons was
practically identical in character and mode of preparation with that
in use to-day. _Cerussa_, or white lead, was made as now by exposing
sheets of lead to the fumes of vinegar. It was used in medicine,
as a pigment, and in the preparation of cosmetics. _Cerussa usta_
was probably red lead. Its present name of _minium_ was originally
applied to cinnabar, the red sulphide of mercury, which was frequently
adulterated with red lead.

_Cinnabar_, formerly obtained from Africa, and, by the Romans,
from Spain, was also used externally in medicine, and was a highly
prized pigment, whose value was known to the Chinese from very early
times. The black sulphide of antimony, the _stimmi_ and _stibium_ of
Dioscorides and Pliny, was employed by women in Asia, Greece, and
latterly in Western Europe, and is still so used in the East, for
blackening their eyelashes. Preparations of antimony were used in
medicine. _Realgar_, the scarlet sulphide of arsenic, the _sandarach_
of Aristotle, and the _arrenichon_ of Theophrastus, was employed as
a pigment, and also in medicine, both internally and externally. The
yellow sulphide of arsenic or _auri pigmentum_ (orpiment), was also
used for the same purposes.

A variety of yellow and red ochres, in addition to the pigments above
mentioned, were used by painters, such as _rubrica_, an iron ochre
of a dark red colour, and _sinopis_, or reddle, obtained from Egypt,
Lemnos, and the Balearic Isles. Oxides of manganese were used as brown
pigments. The white pigment, _paratonium_, was probably meerschaum.
_Melinum_ was a variety of chalk found in Samos. The ancients were well
acquainted with indigo and madder, and with the method of manufacturing
lakes, which was employed by Grecian artists.

The famous _purpurissum_ was chalk or clay stained by immersion in a
solution of Tyrian purple. _Atramentum_ was lamp-black: ivory-black
was used by Apelles, and was known as _elephantinum_. The ink of the
ancients consisted of lamp-black suspended in a solution of gum or
glue. The _atramentum indicum_, imported from the East, was identical
with China ink.

The ancients were well skilled in the art of dyeing, and even of
calico printing. The Tyrians produced their famous purple dye as far
back as 1500 B.C. It was obtained from shell-fish, mainly species of
Murex, inhabiting the Mediterranean. Tyrian purple has been shown to
be dibrom-indigo, and to have been produced by the action of air and
light upon the juices exuded from the shell-fish. The fine linen of the
Old Testament was probably cotton, for the production of which Egypt
was long celebrated. That the Egyptians were acquainted with the use of
mordants seems evident from the following passage from Pliny, quoted by
Thomson:—

  There exists in Egypt a wonderful method of dyeing. The white
  cloth is stained in various places, not with dye stuffs, but with
  substances which have the property of absorbing colours; these
  applications are not visible upon the cloth, but when they are
  dipped into a hot caldron of the dye they are drawn out an instant
  after dyed. The remarkable circumstance is that, though there be
  only one dye in the vat, yet different colours appear upon the
  cloth; nor can the colour be afterwards removed.

This passage accurately describes the process of madder dyeing on
cotton, whereby a variety of fast colours—reds, browns and purples—can
be obtained from the same vat by the employment of different mordants,
such as alumina, oxide of iron, or oxide of tin, etc.

Glass has been known from very early times. Representations of
glass-blowing were found on the monuments of Thebes and Beni Hassan,
and large quantities of glass were exported to Greece and Rome from
Egypt, mainly by Phœnicians. Aristophanes mentions it as _hyalos_, and
speaks of it as the beautiful transparent stone used for kindling fire.
The Egyptians made use of various metallic oxides in colouring glass.
The _hæmatinon_ of Pliny was a red glass coloured with cuprous oxide.
Cupric oxide was used to colour glass green; and ancient blue glass has
been found to contain cobalt. The costly _vasa murrhina_ of the Romans,
obtained from Egypt, probably consisted of fluorspar, identical with
the Blue John of the Derbyshire mines.

Stoneware has been made from time immemorial, and the Chinese have
manufactured porcelain from very remote periods. Bricks and tiles were
made by the Romans, and mortar and stucco were employed by the ancient
Egyptians.

Soap (_sapo_) is mentioned by Pliny, but its detergent properties were
apparently unknown to him. It appears to have been first made by the
Gauls, who prepared it from the ashes of the beech and the fat of
goats, and used it as a pomatum, as did the _jeunesse d’oreé_ of Rome.
Wood ashes, as well as natron, were, however, used by the ancients for
their cleansing properties.

Starch, acetic acid, sulphur, alumen or crude sulphate of alumina,
beeswax, camphor, bitumen, naphtha, asphalt, nitrum (carbonate of
soda), common salt, and lime, were all known to the Egyptians, and were
used by them for many of the purposes in which they are employed to-day.

It will be evident from this brief survey that the ancients possessed a
considerable acquaintance with many operations of technical chemistry;
but, although they must necessarily have accumulated a large amount
of knowledge, very little has come down to us concerning the mode
in which their processes were conducted, or as to the precautions
they employed to ensure uniform results. Their methods were probably
jealously guarded and handed down by successive members of the crafts
as precious secrets. The experienced masters of these crafts must
have met with many strange and perplexing phenomena in the course of
their operations, and a spirit of inquiry must thereby at times have
been awakened. But, under the conditions in which their industries
were prosecuted, the scientific spirit was not free to develop, for
science depends essentially upon free intercommunication of facts and
the spread of knowledge of natural phenomena. Moreover, the great
intellects of antiquity, for the most part, had little sympathy with
the operations of artisans, who, at least among the Greeks and Romans,
were, for the most part, slaves. Philosophers taught that industrial
work tended to lower the standard of thought. The priests, in most
ages, have looked more or less askance at attempts, on the part of the
laity, to inquire too closely into the causes of natural phenomena. The
investigation of nature in early times was impossible for religious
reasons. There was an outcry in Athens when the thunderbolts of Zeus
were ascribed to the collision of clouds. Anaxagoras, Diogenes of
Apollonia, Plato, Aristotle, Diagoras, and Protagoras were charged by
the priests with blasphemy and driven into exile. Prodikos, who deified
the natural forces, as did Empedokles the primal elements, was executed
for impiety. Sacerdotalism in Athens had no more sympathy with science
than had the Holy Congregation in Italy when it banned the writings of
Copernicus, Kepler, and Galileo, and sent Giordano Bruno to the stake.
The educated Greeks had no interest in observing or in explaining the
phenomena of technical processes. However prone they might be to
speculation, they had no inclination to experiment or to engage in the
patient accumulation of the knowledge of physical facts. “You Greeks,”
says Plato in one of his Dialogues, “are ever children, having no
knowledge of antiquity, nor antiquity of knowledge!” The influence of
a spurious Aristotelianism, which lasted through many centuries and
even beyond the time of Boyle, was wholly opposed to the true methods
of science, and it was only when philosophy had shaken itself free from
scholasticism that chemistry, as a science, was able to develop.




CHAPTER II

THE CHEMICAL PHILOSOPHY OF THE ANCIENTS


Speculations as to the origin and nature of matter, and as to the
conditions and forces which affect it, are to be found, more or less
imperfectly developed, in the oldest systems of philosophy of which
we have any record. These speculations are not based, in any real
sense, upon the systematic observation of natural phenomena. Still,
as they appealed to human reason, they must be held to be founded
upon experience, or at least not to be consciously inconsistent with
it: All the oldest cosmogonies regarded water as the fundamental
principle of things: from Okeanos sprang the gods—themselves deified
personifications of the “elements” or principles of which the world was
made.

In the course of time this doctrine of the origin and essential nature
of matter came to be more particularly associated with the name of
Thales of Miletus, who lived six centuries before our era, and who,
according to Tertullian, is to be regarded as the first of the race
of the natural philosophers—that is, the first of those who made it
their business to inquire after natural causes and phenomena. Thales
is known to have passed some years of his life in Egypt, and to have
been instructed in science by the priests of Thebes and Memphis; and it
is therefore possible that he may have been influenced by the Egyptian
teaching in the formulation of his cosmological theories.

It is significant of the tenacity with which the mind clings to
dogma and reveres authority that the teaching of Thales should have
survived through the space of twenty-four centuries. It can be shown
to have affected the course of chemical inquiry down to the close of
the eighteenth century. It influenced the experimental labours of
philosophers so diverse in character as Van Helmont, Boyle, Boerhaave,
Priestley, and Lavoisier—all of whom made attempts to prove or disprove
its adequacy. Van Helmont, indeed, was one of the most strenuous
supporters of the doctrine of Thales, and sought to establish it by
observations which, in the absence of all knowledge of the true nature
of air and water, seemed at the time irrefutable. Perhaps the one most
frequently cited is his observation on the growth of a plant which
apparently had no other form of sustenance than water. He describes how
he planted a willow weighing 5 lbs. in 200 lbs. of earth previously
dried in an oven. The plant was regularly watered, when at the end of
five years it was found to weigh 169 lbs. 3 oz., whereas the earth,
after redrying, had lost only 2 oz. in weight. Hence, 164 lbs. of
woody matter, leaves, roots, etc., had been produced seemingly from
water alone. More than a century had to elapse before any clue to the
true interpretation of Van Helmont’s experiment was gained. It was
first furnished by the observations of Ingenhousz and Priestley.

Although the idea of a primal “element” or common principle is to be
found in every old-world philosophical system, the ancient philosophers
were by no means in agreement as to its character. Anaximenes, who
lived _circa_ 500 B.C., taught that it was air, Herakleitos of Ephesus
that it was fire, and Pherekides that it was earth. The supposition
that a single primordial principle could be made to account for all
forms of matter and all the phenomena and manifestations of the
material world had its difficulties. Attempts to group qualities as
principles, and to construct from these principles the universe, were
indeed made even prior to the age of Thales. It was a comparatively
simple evolutionary step to regard these principles or “elements” as
mutually convertible. Anaximenes’ theory of the formation of rain was
an implicit admission of such convertibility. This philosopher taught
that rain came by the condensation of clouds, which in their turn
were formed by the condensation of air. Everything comes from air and
everything returns to air. That water might be converted by fire into
air was surmised from the earliest times. Such a supposition naturally
sprung from the circumstance that water was everywhere recognised to
disappear or to pass into the air under the influence of fire or solar
heat. The supposition had grown into a fixed belief in the Middle Ages.
Even Priestley, as late as the end of the eighteenth century, imagined
for a time that he had obtained proof of such a mutual conversion.
The possibility of the transmutation of water into earth was a belief
current through twenty centuries, and was only definitely and finally
disproved by Lavoisier in 1770. The conception of fire as the primal
principle has its germ in the fire- or sun-worship of the Chaldeans,
Scythians, Persians, Parsees, and Hindus, and it is not difficult to
trace, therefore, how heat came to be regarded either as antecedent
to, or as associated with, the other primal principles. Empedokles,
apparently, was the first whose name has come down to us to reintroduce
the definite conception of four primal elements—fire, air, water,
and earth. These he regarded as distinct, and incapable of being
transmuted, but as forming all varieties of matter by intermixture
in various proportions. These principles he deified, Zeus being the
personification of the element of fire, Here of air, Nestis of water,
and Aidoneous of earth.

The doctrine of the four elements was also adopted by Plato and
amplified by Aristotle, with whose name indeed it is commonly
associated. Aristotle, the greatest scientific thinker among the
Greeks, exercised an authority almost supreme in Europe during
nearly twenty centuries. His influence is to be traced throughout
the literature of chemistry long after the time of Boyle. It may be
detected even now. Probably few who write chemical memoirs to-day,
and who follow the time-honoured practice of prefacing their own
contributions to knowledge by a statement of what is already known
on the subject, are aware that in so doing they are obeying the
injunctions of Aristotle. His theory of the nature of matter is
contained in his treatise on _Generation and Destruction_. It mainly
differed from that of Empedokles in regarding the four “elements” as
mutually convertible. Each “element” or principle was regarded as being
possessed of two qualities, one of which was shared by another element
or principle.

Thus: Fire is hot and dry; air is hot and wet; water is cold and wet;
earth is cold and dry.

In each primal “element” one quality prevails. Fire is more hot than
dry; air is more wet than hot; water is more cold than wet; earth is
more dry than cold. The relative proportion and mutual working of
these qualities determined the specific character of the “element.”
Thus, if the dryness of fire is overcome by the moisture of water,
air is produced; if the heat of air is overcome by the coldness of
earth, water is formed; if the moisture of water is overcome by the
dryness of fire, earth results. Ancient chemical literature contains
many illustrations or diagrams symbolising the convertibility or mutual
relations of the four “elements.”

It has been frequently stated that the influence of the Peripatetic
philosophy has been inimical to the development of science. But, in
reality, the founder of that school, a descendant of Esculapius, and
undoubtedly one of the greatest and most enlightened thinkers of
antiquity, was an ideal man of science. This is abundantly evident
from such of his works as can be proved to be genuine. Much of what
is called Aristotelianism is entirely foreign to the spirit of the
teaching of Aristotle. The Aristotelians of the Middle Ages were
mainly dialecticians, and almost wholly concerned with the formulæ of
syllogistic inference, and without real sympathy with, or knowledge
of, his system. Much, too, that was attributed to him, and which was
venerated accordingly, is undoubtedly spurious. The fame of the Master
has consequently suffered at the hands of those who, calling themselves
Peripatetics, were in no proper sense followers of his method or
interpreters of his dogma. Aristotle affirmed that natural science
can only be founded upon a knowledge of facts, and facts can only be
ascertained through observation and experiment. He illustrates this
particularly by a reference to astronomy, “which,” he says, “is based
on the observation of astronomical phenomena, and it is the case with
every branch of science or art.” It is erroneous and unjust, therefore,
to suppose that Aristotle’s philosophy, as he taught it, is opposed to
the true methods of science.

A knowledge of Aristotle’s works was transferred by Byzantine writers
to Egypt; and, when that land was overrun by the Arabs in the seventh
century, they adopted his system, spreading it abroad wherever their
conquests extended. In the eighth century they carried it into Spain,
where it flourished throughout their occupation of that country.
From the ninth to the eleventh century the greater part of Europe
was in a state of barbarism. The Moslem caliphate in Spain, under
the beneficent rule of Jusuf and Jaküb, alone preserved science from
extinction. Cordova, Seville, Grenada, and Toledo were the chief seats
of learning in Western Europe; and it was mainly through “the perfect
and most glorious physicist,” the Moslem Ibn-Roshd—better known as
Averroes—(1126–1198), that Christian scholiasts like Roger Bacon
acquired their knowledge of the philosophical system of Aristotle,
and mainly through the Moslems Geber and Avicenna that they gained
acquaintance with the science of the East.

The conception that matter is made up of particles or _atoms_, and
that these particles are in a state of ceaseless motion, is to be met
with in Hindu and Phœnician philosophy. It was taught by Anaxagoras,
Leukippos, and Demokritos to the Greeks, and by Lucretius to the
Romans. Leukippos and Demokritos explained the creation of the world as
due solely to physical agencies without the intervention of a creative
intelligence. According to their theories, the atoms are variable, not
only in size, but in weight. The smallest atoms are also the lightest.
Atoms are impenetrable; no two atoms can simultaneously occupy the same
place. The collision of the atoms gives them an oscillatory movement,
which is communicated to adjacent atoms, and these, in their turn,
transmit it to the most distant ones. Anaxagoras taught that every
atom is a world in miniature, and that the living body is a congeries
of atoms derived from the aliments which sustain it. Plants are living
things, endowed like animals with respiratory functions, and, like
them, atomically constituted. This philosopher was so far in advance
of his age that his countrymen accused him of sacrilege, and he only
escaped death by flight. Further, the assumption that these atoms
exert mutual attractions and repulsions is probably as old as the
fundamental conception itself. At least, so far as can be traced, the
conceptions of atoms and atomic motion are indissolubly connected. This
is not the place to develop the subsequent history of the doctrine of
the atom, nor need we now concern ourselves with the old metaphysical
quibble of its divisibility or indivisibility. It may be, as Lucretius
said, that the original atom is very far down. It may be that the
physical atom is something which _is_ not divided, not something that
_cannot_ be divided. This theory, dimly perceived in the mists of
antiquity, has grown and strengthened with the ages, and in its modern
application to the facts of chemistry has acquired a precision and
harmony unimagined even by the poets and thinkers of old. We shall
see later how the whole course of the science has been controlled,
illumined, and vivified by it. It is not too much to say that the
chemistry of to-day is one vast elaboration of this primeval doctrine.




CHAPTER III

ALCHEMY


Although the intellectual tendencies of the Hellenic mind were hardly
calculated to favour the development of chemistry as a science, the
speculations of the Greeks concerning the essential nature of matter
and the mutual convertibility of the “elements” led incidentally to an
extension of the art of operative chemistry. This extension resulted
from attempts to realise what was the logical outcome of the teaching
of their philosophers—viz., the possibility of the transmutation of
metals. The idea of transmutation has its germ in the oldest systems
of philosophy. It was a plausible doctrine, not wholly unsupported by
the phenomena of the organic world; and it naturally commended itself
to men who were only too prone to adopt what their cupidity and love of
wealth predisposed them to believe.

It has been assumed that alchemy at no time in its history had the
slightest claim to a philosophical foundation, but that its professors
and adepts, even at the outset, consciously traded on the credulity and
greed of their dupes. Much may be urged against such a partial view.
The supposition is not consistent with history or with evolutional
tendencies. It may be, as Davy once said, that “analogy is the fruitful
parent of error;” but the idea that metals could be modified—could even
be changed one into the other—seemed to find support in innumerable
chemical phenomena well known but imperfectly understood. The fact that
alchemy—that is the profession of making gold from other metals—came to
be practised by rogues is no proof that it never had, and never could
have had, a philosophical basis.

The changes which substances experience under the influence of fire,
air, and water, or as the result of their action on each other, are
frequently so profound that even the most superficial of the early
observers of chemical processes could not fail to be impressed by
them. Many of these changes are, in fact, far more striking as regards
alteration in outward characters—such as colour, lustre, density,
etc.—than are the differences between individual metals; say, between
lead and tin, or between tin and silver, or between brass and gold.
That copper ores, by appropriate treatment with other ores, or that
copper itself by the addition of another metal, could be made to
furnish a metallic-looking substance having certain of the attributes
of gold was known to the earliest workers in metals. What is thought
to be the oldest chemical treatise in existence is a papyrus in the
possession of the University of Leyden. It consists of a number of
receipts for the working of metals and alloys, and describes methods
of imitating and falsifying the noble metals. It explains how, by
means of arsenic, a white colour may be given to certain metals, and
how, by the addition of cadmia, copper acquires the colour of gold.
The same papyrus describes a method of blackening metals by the use of
preparations of sulphur. The limited knowledge of chemical phenomena
and of chemical processes which these early workers necessarily
possessed, so far from precluding a belief in the possibility of
transmutation, actually encouraged it. As nothing was known of the
true nature of brass or of its exact relation to copper, it was not
unreasonable to suppose that, if this substance could be made to
acquire _some_ of the attributes of gold by a process essentially
chemical, processes of a like nature might cause it to acquire, if
not _all_, at least so many of them as to enable it to pass for gold
of greater or less fineness. To them, as to us, perfection was, in
technical practice, a question of degree: the very language of the
metallurgists of old was in this respect nowise different from that of
the metallurgists of to-day.

It is not necessary to suppose that these early attempts were
deliberately and consciously fraudulent, like those of coiners who
knowingly seek to make an alloy of lead and tin simulate silver. The
first alchemists sought in good faith to make something which should
be of the true nature and essence of gold as they conceived it to be.
In fact, the idea of transmutation had a rational foundation in a
theory of the intrinsic nature of metals which may be looked upon as a
development of the ancient beliefs concerning the essential nature of
all forms of matter.

Just as the Aristotelian “elements” were qualities which, according to
their degree, determined the nature of substances, so, in like manner,
the specific character of a metal depended upon the relative proportion
of its “sulphur” and “mercury.” These terms had no certain reference
to what we to-day understand by sulphur and mercury. They denoted
simply qualities. The essence or “element” of mercury conferred lustre,
malleability, ductility, and fusibility, or, speaking generally,
the properties which we connote as metallic; while to the essence
or “element” of sulphur was to be attributed the combustibility—or,
speaking generally, the alterability—of the metal by fire. By modifying
the relative proportion of these constituent elements, or by purifying
them from extraneous substances by the operations of chemistry, it
was conceived that the several metals could be changed one into the
other. To effect this purification it was necessary to add various
preparations known as “medicines,” chief among which was the _Great
Elixir_, or _Magisterium_, or the _Philosopher’s Stone_, by which the
final transformation into the noblest of the metals could alone be
achieved.

The Arabic words _kímyâ_ and _iksír_ were originally synonymous and
each was used to denote the agent by which the baser metals could
be transmuted into silver and gold. Ultimately the former term
became restricted to indicate the art of transmutation (alchemy),
whereas _iksír_, or _al-iksír_, continued to denote the medium by
which the transmutation was effected. By later writers the term
was used to indicate a liquid preparation—the _quintessence of the
philosophers_—whence we have the word _elixir_, which always means a
liquid.

The alchemistic theory of the compound nature and mutual relations of
the metals is usually ascribed to Geber; but, although he adopted it,
he distinctly states that it did not originate with him, but that he
found it in the writings of his predecessors.

The idea of the _stone_, the _philosophical powder_, the _grand
magisterium_, the _elixir_, the _tincture_, the _quintessence_—by
all of which terms the transmuting medium is known in the literature
of alchemy—is probably connected with another conception respecting
the origin of metals which can be traced to very early times and was
prevalent throughout the Middle Ages. It was supposed of old that
metals were _generated_ within the earth, as animals and plants were
generated on its surface, and that something akin to a seed, or semen,
was needed to initiate their formation. The great problem of alchemy
was to discover this fecundating substance, as upon it depended the
genesis of the perfect metal. This idea of the conception of metals
runs through the literature of alchemy. It explains many allusions and
much of the terminology of its writers. For example, the furnace in
which the alchemist makes his projection is constantly spoken of as the
_philosophical egg_.

It is impossible to say with certainty when and where the art of
alchemy originated. There is no evidence that it has the antiquity
which certain of its adepts claimed for it. Oleus Borrichius referred
it to the time of Tubal-cain. The earliest writers on alchemy were
probably Byzantine ecclesiastics, some of whom professed to ascribe
the art to Egypt, and eventually to the mythological deity Hermes,
whose association with chemistry in such terms as “the hermetic art,”
“hermetically sealed,” etc., is thus explained.

This much is established—that at some period prior to the tenth century
there arose a special class of operative chemists, for the most
part more learned in the knowledge of chemical phenomena in general,
and more skilled in chemical manipulation, than the craftsmen and
artisans engaged in the manufacture of technical products. They devoted
themselves to searching for methods whereby the common and baser metals
might be converted into silver and gold. The first known definition
of chemistry relates to the aim and operations of this special class.
It occurs in the lexicon of Suidas, a Greek writer of the eleventh
century, who defines chemistry, χημíα as the preparation of silver
and gold. Attempts at the artificial preparation of the noble metals
probably originated with the Arabians, who followed the Egyptians and
the Greeks in the cultivation of chemical pursuits.

Neither Hesiod nor Homer makes mention of the art of producing gold
from any other metal, or speaks of the universal medicine. Nor are
they referred to by Aristotle or by his pupil Theophrastus. Pliny
nowhere speaks of the philosopher’s stone, although he tells the
story of Caligula, who, tempted by his avarice, sought to make gold
from orpiment (_auripigmentum_) by distillation. “The result was that
he did indeed obtain both, and of the finest kind; but in so small
quantity, and with so much labour and apparatus, that, the profit not
countervailing the expense, he desisted.”

According to Boerhaave, the first author who mentions _al-chemia_
is Julius Firmicus Maternus, who lived under Constantine the Great,
and who, in his _Mathesis_, c. 15, speaking of the influences of the
heavenly bodies, affirms “that, if the moon be in the house of Saturn
when a child is born, he shall be skilled in alchemy.”

The first writer who mentions the possibility of transmuting metals
would appear to be a Greek divine called Æneas Garæus, who lived
towards the close of the fifth century, and who wrote a commentary on
Theophrastus. He was followed by Anastatius the Sinaite, Syncellus,
Stephanus, Olimpiodorus; and, says Boerhaave, “a crowd of no less
than fifty more, all Greeks, and most or all of them monks.” “The art
seemed now confined to the Greeks, and among them few wrote but the
religious, who from their great laziness and solitary way of life were
led into vain, enthusiastical speculations, to the great disservice and
adulteration of the art.... They all wrote in the natural style of the
Schoolmen, full of jargon, grimace, and obscurity.”

Experimental alchemy, as distinguished from industrial chemistry,
may, as already stated, be said to have originated with the
Arabians. At first, alchemy was regarded as a branch of the art of
healing, and its professors were invariably physicians who occupied
themselves with the preparation of chemical medicines. In fact, in
the beginning its true aim was regarded as that which Paracelsus and
the school of iatro-chemists subsequently defined it to be. Under
the rule of the Caliphs the study of chemistry made considerable
progress, and its literature was greatly augmented. The most notable
name in the history of chemistry during the eighth century was
=Abu-Moussah-Dschabir-Al-Sufi=—otherwise =Geber=—(born 702, died 765),
who is stated to have been either a native of Mesopotamia, or a Greek
and a Christian, who afterwards embraced Mahometanism, went to Asia,
and acquired a knowledge of Arabic. According to Leo Africanus, a Greek
who wrote of the antiquity of the Arabs, Geber’s book was originally
written in Greek and translated thence into Arabic, and he was not
known by the name Geber, which signifies a _great man_ or a _prince_,
till after this version. Latin translations of what purported to be his
works were first published in the early part of the sixteenth century,
and an English rendering appeared in 1678. According to this it would
seem that Geber regarded all the metals as compounds of “sulphur” and
“mercury,” the differences between them depending upon the relative
proportion and degree of purity of these constituents. He is said to
have distinguished them by the astrological names of the planets: thus
gold became _Sol_, silver _Luna_, copper _Venus_, iron _Mars_, tin
_Jupiter_, and lead _Saturn_. That an occult connection of the metals
with the stars existed was part of the creed of alchemy, and the
influence of that belief is still traceable in chemical, and especially
in pharmaceutical, literature; as, for example, in such terms as _Lunar
caustic_, _Martian preparations_, _Saturnine solutions_, _etc._

It has been held that the idea of a universal medicine had its origin
with Geber. But this may be due to a misreading of his words, which
in reality may have reference to the transmutation of metals. He
tells of a medicine which cures all lepers. But this may be nothing
but allegory. By _man_ is probably meant gold, and by _lepers_ the
other metals; and the medicine is the universal solvent or agent
which transmutes. Alchemistic literature is full of allegories of
this character. Berthelot has shown that in reality there were two
Gebers—one who is generally considered to be of Arab origin, and
another whose identity is not established, but who was probably a
Western European who appears to have lived about the year 1300.[1]

    [1] There is very little doubt that the work of “Phileletha,”
        which professed to be taken from an “Uhralten MS.”
        preserved in the Vatican Library, entitled _Geberi des
        Königes der Araber_, and published by Hieron. Philipp.
        Nitschel, Frankfurth and Leipzig, in 1710, is spurious.

Other notable names in the history of Arabian alchemy are =Rhazes=, or
=Abû Bakr Mohammed ibn Zakaráyá el-Rázi=, who lived _circa_ 925, and
=Avicenna=, or in Arabic =Abû Ali el-Hosein ibn-Abdallah ibn-Sina=,
born 980, died 1037. The former, a Persian, practised medicine at
Baghdad as a follower of Galen and Hippocrates. The latter, one of
the most eminent of Moslem physicians and a voluminous writer, was a
native of Bokhara. He is mainly known in the history of science by
his _Canon of Medicine_, in which he describes the composition and
preparation of remedies. He wrote at least one treatise on alchemy, but
others attributed to him are probably apocryphal. Of his _Philosophia
Orientalis_, mentioned by Roger Bacon and Averroes, no trace remains.

Although it is reasonably certain that the alchemists of the time
of Geber and of his successors had a considerable acquaintance with
manipulative chemistry, there were so many impudent literary forgeries
during the alchemical period that the precise extent of the knowledge
possessed by the early chemists must always remain uncertain.

A number of the ordinary chemical processes, such as distillation,
sublimation, calcination, filtration, appear to have been known to,
and to have been commonly practised by, the Arabian chemists; and many
saline substances, such as carbonate of soda, pearlash, sal-ammoniac,
alum, copperas, borax, silver nitrate, cinnabar, and corrosive
sublimate, were prepared by them. They seem to have known of certain
of the mineral acids, and were familiar with the solvent properties of
_aqua regia_.

An examination of the literature of alchemy serves to show how its
principles and tenets developed. The philosopher’s stone is first heard
of in the twelfth century. Prior to that period the greater number of
the Greek and Arabian writers contented themselves with affirming the
fact of transmutation, without indicating how it might be accomplished.
The universal medicine and the elixir of life were the products of a
later age; no mention of them is known before the thirteenth century.

Alchemy flourished vigorously during the Middle Ages, and lingered
on even until the early part of the nineteenth century. Its history
is simply a long chapter in the history of human credulity. For the
most part it is a record of self-deception, imposture, and fraud. It
produced an abundant literature, mainly the work of ecclesiastics,
between the seventh and fourteenth centuries; but as regards the
artificial preparation of the noble metals or the discovery of the
universal medicine or the elixir of life it was barren of result.

Although no clear line of demarcation is possible, it may be
convenient, in dealing with the personal history of alchemy, to divide
it into the two periods before and after Paracelsus, since under his
inspiration and example alchemy underwent a great development as
regards its professed objects. These eventually became so extravagant
that, wide as are the limits of human credulity, its pretensions
gradually brought it into disrepute, and it fell by the weight of its
own absurdities.

One of the most reputable of the early Western alchemists was =Albert
Groot=, or =Albertus Magnus=, born at Lauingen in 1193. He was a
Dominican monk, who became Bishop of Regensburg, but, resigning his
bishopric, retired to a convent at Cologne, where he devoted himself to
science until his death in 1282. He is credited with having written a
number of chemical tracts, for the most part in clear and intelligible
language, which is more than can be said of the greater portion of
alchemistical literature. He gives an account of the origin and main
properties of the chemical substances known in his time, and describes
the apparatus and processes used by chemists, such as the water-bath,
alembics, aludels, and cupels. He speaks of cream of tartar, alum and
caustic alkali, red lead, liver of sulphur and arsenic, green vitriol
and iron pyrites.

Contemporaneously with him was =Roger Bacon=, _Doctor Mirabilis_,
one of the most erudite men of his age, who was born near Ilchester
in Somerset in 1214, and, after studying at Oxford, became a friar,
occupied himself in philosophical pursuits, and wrote numerous tracts
on alchemy. He describes what was probably gunpowder, but there is
no certain proof that he invented it. In his _De Secretis Artis et
Naturæ_, written before 1249, he gives instructions for refining
saltpetre, and in an anagram which Colonel Hime, in his _Gunpowder and
Ammunition_, has interpreted, he states that a mixture “which will
produce a thundering noise and a bright flash” may be made by taking “7
parts of saltpetre, 5 of young hazel wood, and 5 of sulphur.” He died
in 1285.

=Raymund Lully=, a friend and scholar of Bacon, was born in Majorca
in 1225 (others say 1235), and was buried there in 1315. A member of
the Order of Minorites, he had a great reputation as an alchemist; and
a number of books on alchemy and chemical processes are ascribed to
him. He described modes of obtaining nitric acid and aqua regia, and
studied their action upon metals. He obtained alcohol by distillation,
and knew how to dehydrate it by the aid of carbonate of potash, which
he obtained by calcining cream of tartar. He prepared various tinctures
and essential oils, and a number of metallic compounds, such as red
and white precipitate. To him is usually ascribed the first idea of a
universal medicine.

There is some difficulty in believing that all that is ascribed
to Lully was actually the work of his age, for it would appear to
have been a common practice with the disciples and followers of a
notable scholar to usher in their performances under their master’s
name—a practice not unknown in later days. “So full are they of
the experiments and observations which occur in our later writers
that either the books must be suppositious, or the ancient chemists
must have been acquainted with a world of things which pass for the
discoveries of modern practice” (Boerhaave). The story is that Lully
plunged into the study of chemistry from the desire to cure a maiden of
a cancered breast, and that he was stoned to death in Africa, whither
he had journeyed as a missionary. It has been further alleged that
at one period of his life he made gold in the Tower of London by the
King’s order, and that he offered Edward III. a supply of six millions
to make war against the infidels. As Boerhaave drily remarks, “the
history of this eminent adept is very much imbroiled.”

=Arnoldus Villanovanus=, or =Arnaud de Villeneuve=, a Frenchman, is
said to have been born in 1240, and to have practised medicine in
Barcelona, where he incurred the enmity of the Church by reason of his
heretical opinions, and was obliged to leave Spain. He led a wandering
life, eventually settling in Sicily, under the protection of Frederick
II., and acquired a great reputation as a physician. Summoned thence by
Clement V., who lay sick at Avignon, he lost his life by shipwreck in
1313.

=Johannes de Rupecissa=, or =Jean de Raquetaillade=, a Franciscan friar
who lived from about the middle to the end of the fourteenth century,
wrote a number of treatises on alchemy, and described methods of making
calomel and corrosive sublimate. He was accused of the practice of
magic, and, by order of Innocent VI., was thrown into prison, where he
died. He was buried at Villefranche.

=George Ripley=, an Englishman, Canon of Bridlington, practised alchemy
during the second half of the fifteenth century. He spent some time
in Italy in the service of Innocent VIII. On his return to England he
became a Carmelite, and died in 1490. Like Bacon, he was charged with
magic. According to Mundanus, he followed alchemy with such success
that he was able to advance to the knights of St. John of Jerusalem
large amounts of gold for the defence of the Isle of Rhodes against the
Turks.

One of the most important names in connection with the history of
alchemy is that of =Basil Valentine=. Of his personal history nothing
is known. He was supposed to be a Benedictine monk who lived in Saxony
during the latter half of the fifteenth century; but there are grounds
for the belief that the numerous writings attributed to him are in
reality the work of various hands. The attempt made by Maximilian I. to
discover the identity of the author was unavailing, nor have subsequent
inquiries had any better result. The collection of books bearing his
name, first published in the beginning of the seventeenth century,
reveals quite a remarkable number of chemical facts up to that time not
generally known. The most important of these relate to antimony and its
preparations, such as butter of antimony, powder of algaroth, oxide
of antimony, etc. He seems to have known of arsenic, zinc, bismuth,
and manganese. He described a number of mercurial preparations, and
many of the salts of lead were known to him. He mentions fulminating
gold, and was aware that iron could be coated with copper by immersion
in a solution of blue vitriol. He knew of green vitriol and the
double chloride of iron and ammonium, and gave the modes of making
a considerable number of other metallic salts, such as the _sal
armoniacum_, which we now know as sal ammoniac. He also appears to have
prepared ether and the chloride and nitrate of ethyl.

There is reason to believe, as stated already, that many of the
published works ascribed to these learned men are the work of obscure
individuals who traded on their fame. What may with certainty be
credited to them serves to show that their theoretical opinions had
much in common. They all regarded the transmutation of metals and
the existence of the philosopher’s stone as facts which could not be
controverted. They followed Geber in assuming that all the metals were
essentially compound in their nature, and consisted of the essence or
“element” of mercury, united with different proportions of the essence
or “element” of sulphur.

The alchemists were the professional chemists of their time, and many
of them were practising physicians. Indeed, professional chemistry may
be said to have originated out of the practice of physic. As the number
of chemical products increased and their value in therapeutics became
more and more appreciated, there arose another school of alchemists,
whose energies were devoted, not to the transmutation of metals—which,
however plausible as a belief, seemed hopeless of achievement—but to
the more immediate practical benefits which it was recognised must
follow from the closer association of chemistry and medicine. This
school came to be known as the iatro-chemists. As their doctrines
exercised a great influence upon the development of chemistry, it
will be desirable to treat of them and their professors in a special
chapter.




CHAPTER IV

THE PHILOSOPHER’S STONE


During the fourteenth, fifteenth, and sixteenth centuries the cult of
alchemy attained to the dignity of a religion. Belief in transmutation
and in the virtues and powers of the philosopher’s stone, in the
universal medicine, the alkahest, and the elixir of life, formed its
articles of faith. The position it acquired was due to some extent to
the attitude towards it of the Romish Church. Many reputable bishops
and fathers were professed alchemists; and chemical laboratories, as
in the Egyptian temples, were to be found in monasteries throughout
Christendom. Pope John XXII., who had a laboratory in his palace
at Avignon, is the reputed author of a work, _Ars Transmutatoria_,
published in 1557. But to a still larger extent it was due to the fact
that alchemy appealed to some of the strongest of human motives—the
wish for health, the fear of death, and the love of wealth. It was a
cunningly devised system, which exploited the foibles and frailties of
human nature. The policy of the Church, however, it should be said, was
not consistently and uniformly favourable to alchemy. Its practices
occasionally came under the papal ban, although at times, to suit the
exigencies of Christian princes, the interdict was removed. Theosophy
and mysticism were first imported into alchemy, not by Arabs, but by
Christian workers. The intimate association of religion with alchemy
during the Middle Ages is obvious in the writings of Lully, Albertus
Magnus, Arnaud de Villeneuve, Basil Valentine, and other ecclesiastics.
Invocations to divine authority are freely scattered over their pages.
Even the lay alchemist professed to rule his life and conduct by the
example and precepts of the good Bishop of Regensburg. He was directed
to be patient, assiduous, and persevering; discreet and silent; to work
alone; to shun the favour of princes and nobles, and to ask the divine
blessing on each operation of trituration, sublimation, fixation,
calcination, solution, distillation, and coagulation.

Although alchemy, at least in its decadent days, lived for the most
part by its appeal to some of the lowest instincts of mankind, and is
only worth notice as a transient phase in the history of science, a
few details concerning the tenets and practices of its professors may
be of interest to the curious reader. And first as regards the nature
of the philosopher’s stone—the grand magistery, the quintessence.
Many alchemists professed to have seen and handled it. It is usually
described as a red powder. Lully mentions it under the name of
_Carbunculus_. Paracelsus says that it was like a ruby, transparent
and brittle as glass; Berigard de Pisa that it was of the colour of
a wild poppy, with the smell of heated sea salt; Van Helmont that it
was like saffron, with the lustre of glass. Helvetius describes it
as of the colour of sulphur. Lastly, an unknown writer, under the
pseudonym of “Kalid,” says that it may be of any colour—white, red,
yellow, sky-blue, or green. As the substance was wholly mythical, a
certain latitude of description may reasonably be expected. Some of
the alchemists were of opinion that the magistery was of two kinds—the
first, the _grand_ magistery, needed for the production of gold; the
second, the _small_ magistery, only capable of ennobling a metal as far
as the stage of silver. Then, as to the amounts required to effect a
transmutation, accounts are equally discrepant. Arnaud de Villeneuve
and Rupescissa assert that one part of the grand magistery will convert
a hundred parts of a base metal into gold; Roger Bacon, a hundred
thousand parts; Isaac of Holland, a million. Raymond Lully states that
philosopher’s stone is of such power that even the gold produced by
means of it will ennoble an infinitely large amount of a base metal.

It is hardly necessary to state that a preparation of such potency
is capable of effecting anything or everything; and accordingly, as
time went on, other attributes than that of transmutation came to be
associated with it. It may be, as Boerhaave surmises, that the idea of
a universal medicine had its origin in a too literal interpretation
of Geber’s allegory of the six lepers. Be this as it may, during the
fourteenth and fifteenth centuries the philosopher’s stone was gravely
prescribed as a means of preserving health and prolonging life. In
case of illness one grain was directed to be dissolved in a sufficient
quantity of good white wine, contained in a silver vessel, the draught
to be taken after midnight. Recovery would follow after an interval
depending upon the severity and age of the complaint. To keep in good
health, the dose was to be repeated at the beginning of spring and
autumn. “By this means,” says Daniel Zacharias, “one may enjoy perfect
health until the end of the days assigned to one.” Isaac of Holland
and Basil Valentine are equally explicit, but in their case it is
recommended that the dose should be taken once a month: thus life would
be prolonged “until the supreme hour fixed by the king of heaven.”
Other alchemists were not always so prudent in prophecy. Artephius gave
the limit of human life thus prolonged as a thousand years; Gualdo,
a Rosicrucian, was stated to have lived four hundred years. Raymond
Lully and Salomon Trismosin, we are told, renewed their youth by means
of it. The advanced age at which Noah begat children could only be
due, says Vincent de Beauvais, to his use of the philosopher’s stone.
Dickinson wrote a learned book to prove that the great age of the
patriarchs was owing to the same secret.

But not only were health and length of days the fortunate lot of him
who possessed the philosopher’s stone; increase of wisdom and virtue
equally followed from its use. As it ennobled metals, so it freed
the heart from evil. It made men as wise as Aristotle or Avicenna,
sweetened adversity, banished vain-glory, ambition, and vicious
desires. Adam received it at the hands of God, and it was given also to
Solomon, although the commentators were rather exercised to know why,
as he possessed the philosopher’s stone, he should have sent to Ophir
for gold.

It would serve no good purpose to attempt to describe the recipes
given by various alchemists to prepare this precious substance. With
an affectation at times of precision, they were purposely obscure, and
always enigmatical. As Boyle said of them, they could scarcely keep
themselves from being confuted except by keeping themselves from being
clearly understood. One example of their recipes must suffice: “To fix
quicksilver.—Of several things take 2, 3 and 3, 1; 1 to 3 is 4; 3, 2
and 1. Between 4 and 3 there is 1; 3 from 4 is 1; then 1 and 1, 3 and
4; 1 from 3 is 2. Between 2 and 3 there is 1, between 3 and 2 there is
1. 1, 1, 1, and 1, 2, 2 and 1, 1 and 1 to 2. Then 1 is 1. I have told
you all.” No wonder, after an equally luminous explication, a pupil
of Arnaud de Villeneuve should have exclaimed: “But, master, I do not
understand.” Upon which the master rejoined that he would be clearer
another time.

Nor is it necessary to dilate upon the other virtues which were
ascribed at various times to the philosophical powder, as, for
example, its power of making pearls and precious stones, or of its
use in preparing the _alkahest_, or universal solvent, invented by
Paracelsus. In their attempts to fathom the depths of human credulity
the alchemists at length over-reached themselves. The idea of a
universal solvent carried with it, as Kunkel pointed out, its own
refutation: if it dissolved everything, no vessel could contain it. And
yet, says Boerhaave, a whole library could be filled with writings by
the school of Paracelsus on the alkahest. From the latter end of the
sixteenth century repeated attempts were made to expose the pretensions
and demonstrate the absurdities of alchemy. Among its adversaries may
be cited Thomas Erastius, Hermann Conringius, and the Jesuit Kircher.
Many of their dupes, potentates and princes who were powerful enough
to exercise it, occasionally visited with their vengeance those who,
unmindful of the injunctions of Albert the Great, had traded too long
upon their credulity. The Emperor Rudolph II., who earned the title of
“The Hermes of Germany,” was a zealous cultivator of alchemy, and had a
well-equipped laboratory in his palace at Prague, to which every adept
was welcome. Ferdinand III. and Leopold I. were also patrons of the
hermetic art, as were Frederick I. and his successor, Frederick II.,
Kings of Prussia. Indeed, at one period nearly every Court in Europe
had its alchemist, with the privileges of the Court fool or the poet
laureate. The fraud and imposture to which the practice gave rise led
occasionally to the promulgation of stringent laws against it, and at
times the pursuit of operative chemistry became well-nigh impossible
in some countries. In the fifth year of the reign of Henry IV. (1404)
it was enacted that “None from henceforth shall use to multiply gold
or silver, or use the craft of multiplication; and if the same do he
shall incur the pain of felony.” According to Watson, the true reason
for passing this Act was not an apprehension that men should ruin their
fortunes by endeavouring to make gold, but a jealousy lest Government
should be above asking aid of the subject. At the same time, letters
patent were granted to several persons, permitting them to investigate
the universal medicine and perform the transmutation of metals.

Alphonse X., of Castille, the author of the _Key of Wisdom_, practised
alchemy. Henry VI., of England, and Edward IV. had dealings with
adepts. Even Elizabeth Tudor, who was a shrewd enough sovereign,
had the notorious Dr. Dee in her pay. Charles VII. and Charles IX.,
of France, Christian IV., of Denmark, and Charles XII., of Sweden,
sought to replenish their exhausted treasuries by the aid of the
philosopher’s stone. If princes eventually learned not to put their
trust in alchemists, alchemists learned equally to their cost not to
put their trust in princes. Duke Julius, of Brunswick, in 1575, burnt
a female alchemist, Marie Ziglerin, who had failed in her promise to
furnish him with a prescription for the making of gold. David Benther
killed himself to escape the fury of the Elector Augustus, of Saxony.
Bragadino was hanged at Munich in 1590 by the Elector of Bavaria.
Leonard Thurneysser, who gained an evil notoriety in his day as one of
the most unscrupulous of the followers of Paracelsus, and who amassed
considerable wealth by the sale of cosmetics and nostrums, was deprived
of his ill-gotten gains in 1584 by the Elector of Brandenburg, and
died in misery in the convent. Borri, a Milanese adventurer, who had
deceived Frederick III., of Denmark, was imprisoned for years by that
monarch, and died in captivity in 1695. William de Krohnemann was
hanged by the Margrave of Byreuth, who, with grim irony, caused the
inscription to be fixed to his gibbet: “I once knew how to fix mercury,
and now I am myself fixed.” Hector de Klettenberg was beheaded in 1720
by Augustus II., King of Poland.

All the followers of Hermes were not so wary or so candid as the
artist who declined an invitation to visit the Court of Rudolph II.,
saying: “If I am an adept, I have no need of the Emperor; if I am not,
the Emperor has no need of me.” Well might John Clytemius, Abbot of
Wiezenberg, write: “_Vanitas, fraus, dolus, sophisticatio, cupiditas,
falsitas, mendacium, stultitia, paupertas, desesperatio, fuga,
proscriptio et mendicitas, perdisæque sunt chemiæ_.”

Despite the attacks of Kunkel, Boerhaave, the elder Geoffroy, Klaproth,
and other chemists of influence and repute, alchemy died hard. It
found believers in England until near the close of the eighteenth
century, and was professed even by a Fellow of the Royal Society—Dr.
James Price, of Guildford, who, in chagrin at the exposure of his
pretensions, put an end to his existence in 1783. Hermetic societies
existed in Westphalia, at Königsberg, and at Carlsruhe down to the
first decade of the nineteenth century. M. Chevreul, who lived well
into that century, relates that he knew of several persons who were
convinced of the truth of alchemy, among them “generals, doctors,
magistrates, and ecclesiastics.” The strange medley of alchemy,
theosophy, thaumaturgy, and cabalisticism professed by Christian
Rosenkreuz is not without its adherents, even in this twentieth century.

If the baser metals have not been made to furnish gold, truth at least
has followed from the practice of error. This is the only transmutation
which the art of Hermes has succeeded in effecting. To err is human.
Although alchemy is not without its special interest as one of the
most remarkable aberrations in the history of science, some of its
practitioners, it must be admitted, deceived only themselves: if
misguided, they were at least honest, and pursued their calling in a
settled conviction of the soundness of their faith. Although they never
reached their goal—the discovery of the Philosopher’s Stone and the
Elixir of Life—their labours were not wholly vain, for many new and
unexpected facts came to light as the result of their assiduity.

“Credulity in arts and opinions,” wrote Lord Bacon in _De Augmentis
Scientiarum_,

  is likewise of two kinds—viz., when men give too much belief to
  arts themselves, or to certain authors in any art. The sciences
  that sway the imagination more than the reason are principally
  three—viz., astrology, natural magic, and alchemy.... Alchemy may
  be compared to the man who told his sons that he had left them
  gold, buried somewhere in his vineyard; while they by digging found
  no gold, but by turning up the mould about the roots of the vines
  procured a plentiful vintage. So the search and endeavours to make
  gold have brought many useful inventions of light.




CHAPTER V

IATRO-CHEMISTRY


The term “iatro-chemistry” denotes a particular phase in the history
of medicine and of chemistry. The iatro-chemists were a school of
physicians who sought to apply chemical principles to the elucidation
of vital phenomena. According to them, human illnesses result from
abnormal chemical processes within the body, and these could only be
counteracted by appropriate chemical remedies. Although this idea did
not originate with him, the chief exponent of this school is commonly
said to be Paracelsus.

A man of violent passions, coarse, drunken, arrogant, and unscrupulous,
=Philippus Aureolus Theophrastus Paracelsus Bombastus von Hohenheim=—to
give him his full name—would seem to have possessed none of the
attributes needed by the successful leader of an intellectual
revolution.

Born at Etzel in Switzerland in 1493, son of a physician, William
Bombast von Hohenheim, who combined the practice of astrology with
that of alchemy, Paracelsus, even as a youth, became a wanderer,
passing from province to province and cloister to cloister, living
by telling fortunes and practising sometimes as a quack and at other
times as an army surgeon, and gaining, as he tells us, much curious
information from old women, gipsies, conjurers, and chemists. If we may
trust his own account of himself, he had, before he was thirty-three,
wandered over the whole of Europe, and even into Africa and Asia,
everywhere performing miraculous cures and constantly getting into
trouble. In 1526 he secured the appointment of Professor of Physic in
the University of Basle, and signalised his occupancy of the chair
by a course of lectures—a farrago of confused German and barbarous
Latin—in which he assailed with extraordinary vigour and unexampled
coarseness the medical system of the school of Galen. Scandalised as
his professional brethren might be, Paracelsus expressed, intentionally
or unintentionally, the feeling of impatience with which the laity
viewed a system of therapeutics based only on tradition. In this revolt
against authority he initiated a movement which, whatever might have
been its influence on medicine, served eventually, under the guidance
of worthier men, to emancipate chemistry from the thraldom of alchemy.

Paracelsus did little more than initiate. Although his many tracts
show that he was familiar with nearly every chemical preparation of
his time, many of which he used in his practice, he added no new
substance to science. A man of great ability and extraordinary talent,
he squandered his powers in dissipation. His intemperate conduct soon
lost him his chair at Basle; and, after an ignoble quarrel with the
magistracy, he fled the town, and, resuming his wandering life, died,
under wretched circumstances, at Salzburg, in his forty-eighth year.

Space will not permit of any account of the philosophical opinions
of Paracelsus—of his mysticism, his theosophy, his pantheism, his
extraordinary doctrine of the Archæus and Tartarus, his association of
astrology with medicine. His chief merit lies in his insistence that
the true function of chemistry was not to make gold artificially, but
to prepare medicines and substances useful to the arts. He thereby made
chemistry indispensable to medicine, and thenceforward chemistry began
to be taught in the universities and in the schools as an essential
part of a medical education.

Paracelsus is usually regarded as a typical alchemist—the kind of
man made familiar to us by the paintings of Teniers, Van Ostade, and
Stein—a boorish, maudlin knave, who divided his time between the
pothouse and the kitchen in which he prepared his extracts, simples,
tinctures, and the other nostrums which he palmed off upon a credulous
world, as ignorant and superstitious as himself. There is much in the
personal history of Paracelsus that serves to justify such a view of
him. That he was in the main an impudent charlatan, ignorant, vain, and
pretentious, there can be little doubt. He had an astonishing audacity
and a boundless effrontery; and it was largely by the exercise of these
qualities that he secured such professional success as he enjoyed.

To judge from the number of the published works associated with his
name, he was an active and industrious writer. Considering that during
the greater part of his waking time he was more or less intoxicated, it
is difficult to conceive what opportunity he had for composing them.
Only one or two are known to be genuine. These, according to Operinus,
his publisher, he dictated; and from their incoherence and obscurity,
their mystical jargon, and misuse of terms, they read like the ravings
of one whom drunkenness had deprived of reason. Many of the tracts and
larger works appeared after his death—some of them years after; and
there is no certain proof that he was the actual author. Even if we
regard them as suppositious, the fact that they should be published
under his name is significant of the influence and notoriety which this
extraordinary man succeeded in achieving during his short and chequered
career.

The immediate followers of Paracelsus—among whom may be named
Thurneysser, Dorn, Severinus, Duchesne—distinguished themselves only
by the boldness with which they promulgated his doctrines, and the
unscrupulous use which they made of his methods. They were all zealous
anti-Galenists, who professed to believe that the sum and perfection
of human knowledge was to be found in the Cabala, and that the secrets
of magical medicine were contained in the Apocalypse. They adopted
pantheism in all its grossness: everything that exists eats, drinks,
and voids excrement; even minerals and liquids assimilate food, and
eliminate what they do not incorporate. Sylphs inhabit the air, nymphs
the water, pigmies the earth, and salamanders the fire. Thus even the
Aristotelian elements were animated. Mercury, sulphur, and salt were,
according to Paracelsus, the primal principles which entered into
the composition of all things, material and immaterial, visible and
invisible. The following so-called “harmonies” were essential articles
of faith with a Paracelsian:—

    Soul       Spirit     Body
    Mercury    Sulphur    Salt
    Water      Air        Earth

The laws of the Cabala were held to explain the functions of the body.
The sun rules the heart, the moon the brain, Jupiter the liver, Saturn
the spleen, Mercury the lungs, Mars the bile, Venus the kidneys.
Gold was a specific against diseases of the heart; the liquor of Luna
(solution of silver) cures diseases of the brain. “The remedies,” said
Paracelsus, “are subjected to the will of the stars, and directed by
them. You ought, therefore, to wait until heaven is favourable before
ordering a medicine.”

The Paracelsian physicians, for the most part, were a set of dangerous
fanatics, who, in their contempt for the principles of Hippocrates,
Galen, and Avicenna, and in their reckless use of powerful remedies,
many of them metallic poisons, wrought untold misery and mischief. The
inevitable reaction set in, and certain of the faculties, particularly
that of Paris, prohibited their licentiates, under severe penalties,
from using chemical remedies. It is not to be supposed, however, that
all iatro-chemists were unscrupulous charlatans. Some of them clearly
perceived the significance and true value of the movement which
Paracelsus may be credited with having originated.

=Andreas Libavius=, or Libau, originally a physician, born in Halle,
is best known by his _Alchymia_, published in 1595, which contains an
account of the main chemical facts known in his time, and is written
in clear and intelligible language, in strong contrast to the mystery
and obscurity of his predecessors. He was the discoverer of stannic
chloride, still known as the fuming liquor of Libavius, and described
a method of preparing oil of vitriol in principle identical with that
now made use of on a manufacturing scale. He died in 1616.

=John Baptist van Helmont=, a scion of a noble Brabant family, was
born in Brussels in 1577. After studying philosophy and theology at
the University of Louvain, he directed his attention to medicine, and
made himself familiar, in turn, with every system from Hippocrates to
Paracelsus. Having spent some time in travel, he settled on his estate
at Vilvorde, and occupied himself with laboratory pursuits until his
death in 1644.

Van Helmont was a scholarly, studious man, and a philosopher. A
theosophist and prone to mysticism, he had many of the mental
characteristics of Paracelsus, without his fanaticism and overweening
egotism. He narrowed the number of Aristotle’s elements down to one,
and, like Thales, considered water to be the true principle of all
things, supporting his theory by ingenious observations on the growth
of plants (see p. 20). He first employed the term _gas_, and was aware
of the existence of various æriform substances, anticipating Hales, who
has been styled the father of pneumatic chemistry, in the discovery of
many gaseous phenomena. He gave an accurate description of carbonic
acid gas, which he termed _gas sylvestre_, and showed that it is
produced from limestone and potashes in the fermentation of wine and
beer, and that it is formed in the body and in the earth. The doctrines
of the iatro-chemists were further spread by Sylvius in Holland, and by
Willis in England.

=Francis de le Boë Sylvius=, born at Hanau in 1614, became Professor
of Medicine in the University of Leyden, where he exercised great
influence as a teacher until his death in 1672. Medicine he treated
simply as a branch of applied chemistry, and the vital processes of
the animal body as purely chemical. He freed the theory of physic from
much of the mystical absurdity introduced into it by Paracelsus and
van Helmont, and by his practice brought chemical remedies once more
into vogue. He was aware of the distinction between venous and arterial
blood, and that the red colour of the latter was due to the influence
of air. Combustion and respiration he regarded as analogous phenomena.

=Thomas Willis= was born in Wiltshire in 1621, and while a student at
Christchurch bore arms in the Royalist army when Oxford was garrisoned
for Charles I. In 1660 he became Sedleian Professor of Natural
Philosophy, and ultimately settled in London as a physician. He died in
1675, and was buried in Westminster Abbey.

Willis imagined that all vital actions were due to different kinds of
fermentation, and that diseases were caused by abnormalities in the
fermentative process. Although a Paracelsian as regards his theory of
the constitution of matter, he followed Sylvius and his pupil Tachenius
in banishing mysticism from medicine. He was a skilful anatomist, and
gave the first accurate description of the brain and nerves.

Other notable iatro-chemists were Angelus Sala, Daniel Sennert, Turquet
de Mayerne (who became body physician to James I.), Oswald Croll,
Adrian van Mynsicht, and Thomas Lieber. Croll introduced the use of
potassium sulphate and succinic acid into medicine, and Van Mynsicht
that of tartar emetic. Various antimonial preparations had previously
been employed by chemical physicians since the time of Basil Valentine,
despite the ban of the Parliament of Paris on their use.

The chief service of iatro-chemistry to science consisted in its
influence in bringing chemistry within the range of professional study,
whereby a great extension in its pursuit was effected, with the result
that a largely increased number of substances was discovered. Moreover,
this wider experience of chemical processes familiarised workers with
chemical phenomena in general, and thereby contributed to lay the
foundations of a general theory of chemical action, which a succeeding
age strove to complete.

During the period of iatro-chemistry, which may be said to have
extended from the first quarter of the sixteenth century to the latter
half of the seventeenth, chemistry was advanced along practical
lines by the labours of many men, chief of whom were Agricola the
metallurgist, Palissy the potter, and Glauber the technologist. These
men were primarily experimental chemists, who took little or no part
in the fruitless polemics of the period, but followed their avocation
in the true spirit of investigators, and thereby enriched science with
many new and well-ascertained facts.

=George Agricola=, born at Glauchau in Saxony in 1494, was a
contemporary of Paracelsus. After studying medicine at Leipzig, he
devoted himself to metallurgy and mineralogy, first at Joachimsthal,
and published a number of works which were long deservedly regarded as
the leading treatises on these subjects.

In his _Libri_ XII. _de re Metallica_ he gives an account of what was
known in his time respecting the extraction, preparation, and testing
of ores. He describes the smelting of copper and the recovery of the
silver which might be associated with it. He also describes methods of
obtaining quicksilver, and of purifying it by treatment with salt and
vinegar. He gives a full description of the method of obtaining gold by
amalgamation, and of recovering the mercury by distillation. He gives
accounts of the smelting of lead, tin, iron, bismuth, and antimony,
and describes the manufacture of salt, nitre, alum, and green vitriol.

The whole work, which is of folio size, is illustrated by wood-cuts,
which give a faithful idea of the nature of the several operations, and
of the character of furnaces, trompes, bellows, and tools employed in
them. It is by far the most important technical work of the sixteenth
century, and it exercised great influence on the art of metallurgy.
The descriptions—at least as regards European processes—are evidently
the result of personal observation. Agricola visited the mines, and
faithfully noted the different methods of sorting and washing the
ores, the characters of which he accurately describes. His accounts
of the various smelting operations are so detailed that it is obvious
they must have been put together after personal inquiry. The study of
metallurgy, indeed, was the main object of his life; and he devoted to
its pursuit even the pension which had been settled on him by Maurice,
Elector of Saxony. He became Mayor of Chemnitz, died there in 1555, and
was buried at Zeitz.

=Bernard Palissy= lived throughout the greater portion of the sixteenth
century. Although not a professed chemist, nor a follower of any
particular school, he was an ardent self-taught experimentalist and a
keen and accurate observer, who greatly enriched ceramic art by his
discoveries.

=Johann Rudolf Glauber= was born at Karlstadt, in Bavaria, in 1604,
and after a restless life died in Amsterdam in his sixty-fourth year.
He published an encyclopædia of chemical processes, in which he
describes the preparation of a great variety of substances of technical
importance. The greater number of the pharmacopœias of the seventeenth
century are indebted to him for their descriptions of the mode of
manufacture of their official preparations. He discovered sodium
sulphate—his _sal mirabile_, still frequently named after him—and
introduced it into medicine.

During this period the common mineral acids—sulphuric, hydrochloric,
and nitric—became ordinary articles of commerce, and were used in the
manufacture of a number of useful products, chiefly inorganic salts.
A considerable number of metallic oxides were also in common use, and
were applied to a variety of purposes in the arts. The knowledge of
definite organic substances was much more limited. Acetic acid had long
been known, but was first obtained in a concentrated form during this
period by the distillation of verdigris. A number of other acetates
were also known, as well as certain tartrates—as, for example, salt of
sorrel, Rochelle or seignette salt, and tartar emetic. Succinic and
benzoic acid were introduced into medicine, and Tachenius discovered
one of the characteristic acids of fat and oil (stearic acid). Spirit
of wine was, of course, largely made and used in the preparation of
tinctures and essences. Ether, originally known as _oleum vitrioli
dulce verum_, was first discovered by Valerius Cordus; and a mixture of
it with alcohol, long known as Hoffmann’s drops, appears to have been
employed as a medicine by Paracelsus.




CHAPTER VI

“THE SCEPTICAL CHEMIST”: THE DAWN OF SCIENTIFIC CHEMISTRY.


The latter half of the seventeenth century was a remarkable period
in the history of the intellectual development of Europe. At that
time nearly every department of human knowledge seemed to have become
permeated by an eager spirit of scepticism, inquiry, and reform.
The foundation of the Royal Society of London for Improving Natural
Knowledge, the Accademia del Cimento of Florence, the Academie Royale
at Paris, the Berlin Academy, all within a few years of each other,
was significant of the times. Chemistry was no longer to be a sacred
mystery, to be known only to priests, and its secrets jealously
guarded by them. Science had chafed under the domination of the
schoolmen; it was now contemptuous of the dialectics of the Spagyrists.
Experimentarian philosophy became even fashionable; and the purely
deductive methods of the Peripatetics gradually gave place to the only
sound method of advancing natural knowledge. The supremacy of the
old philosophy may be said to have been first distinctly challenged
by Robert Boyle. The appearance in 1661 of his book, _The Sceptical
Chemist_, marks a turning-point in the history of chemistry. The
“Chemico-physical Doubts and Paradoxes” raised by Boyle “touching the
experiments whereby vulgar Spagyrists are wont to endeavour to evince
their Salt, Sulphur, and Mercury to be the true Principles of Things,”
eventually sealed the fate of the doctrine of the _tria prima_, and of
the tenets of the school of Paracelsus.

In this treatise Boyle sets out to prove that the number of the
peripatetic elements or principles hitherto assumed by chemists is, to
say the least, doubtful. The words “element” and “principle” are used
by him as equivalent terms, and signify those primitive and simple
bodies of which compounds may be said to be composed, and into which
these compounds are ultimately resolvable. He considered that the
matter of all bodies was originally divided into small particles of
different shapes and sizes, and that these particles might unite into
small “parcels,” not easily separable again; that a great variety of
compounds may arise from a few ingredients; that various substances are
obtainable from bodies by fire; that fire is not the true and genuine
analyser of bodies, since it does not separate the principles of a
body, but variously alters its nature; and that some things obtained
from a body by fire were not its proper or essential ingredients.
Three is not precisely and universally the number of the distinct
substances or elements into which all compound bodies are resolvable
by fire, inasmuch as some bodies afford more than three principles.
Earth and water are as much chemical principles as salt, sulphur, and
mercury. Even the limitation to five chemical principles is too narrow.
Such is proved to be the case by the mode in which bodies, animals
and vegetable, grow, and by the analysis of minerals and metals. The
chemical theory of “qualities” of the Spagyrists is narrow, defective,
and uncertain; supposes things not proved; is often superfluous, and
frequently contradicts the phenomena of nature. The “principles” found
in bodies cannot be the cause of their qualities, since contrary
qualities are ascribed to the same body. He concludes, therefore, that
the Paracelsian elements—their “salt,” “sulphur,” and “mercury”—are not
the first and most simple principles of bodies; but that these consist,
at most, of concretions of corpuscles or particles more simple than
they, and possessing the radical and universal properties of volume,
shape, and motion.

[Illustration: ROBERT BOYLE.

From a painting by F. Kerseboom in the possession of the Royal Society.]

=Robert Boyle=, fourteenth child and the seventh and youngest son of
Richard the “Great” Earl of Cork, and Lord High Chancellor of Ireland,
was born at Lismore in 1626. He was educated at Eton under Sir Henry
Wotton, and, after spending some years on the Continent, settled at
Stalbridge in Dorset, where he owned a manor. He became a member of
what was known as the Invisible College, a small association of men
interested in the new philosophy, who met at each other’s houses in
London, and occasionally at Gresham College, “to discourse and consider
of philosophical inquiries and such as related thereunto.” The meetings
were subsequently held in Oxford, and Boyle took up his residence there
in 1654. Here—in association with Wilkins; John Wallis and Seth Ward,
the two Savilian Professors of Geometry and Astronomy; Thomas Willis,
the physician, then student of Christ Church; Christopher Wren, then
Fellow of All Souls’ College; Goddard, Warden of Merton; and Ralph
Bathurst, Fellow of Trinity, and afterwards its President—they sought
to cultivate the new philosophy, “being satisfied that there was no
certain way of arriving at any competent knowledge unless they made a
variety of experiments upon natural bodies. In order to discover what
phenomena they would produce, they pursued that method by themselves
with great industry, and then communicated their discoveries to each
other.” The Invisible College eventually grew into the Royal Society,
which received its charter in 1663. Boyle removed to London in 1668,
and died there on December 31st, 1691, in the sixty-fifth year of his
age.

A man of integrity, modest, simple, and unassuming, Boyle was an
assiduous and true student of science, and practically the whole of
his life was given to its pursuit. His social position, his example,
the purity of his private life, and the fame of his discoveries made
his personal influence very considerable, to the great advantage of
science in this country. His experimental work was of a high order.
He introduced the air-pump into England, and his “pneumatical engine”
enabled him to discover many of the fundamental properties of a gas,
notably the relation of its volume to pressure. He also discovered
the dependence of the boiling point of a liquid upon atmospheric
pressure, explained the action of the syphon, the effect of the air
on the vibration of a pendulum and on the propagation of sound, and
made experiments on the nature of flame, and on the relation of air to
combustion and respiration. In his _History of Fluidity_ he seeks to
show that a body seems to be fluid by consisting of corpuscles touching
one another only in some parts of their surfaces; whence, by reason of
the numerous spaces between them, they easily glide along each other
till they meet with some resisting body to whose internal surface they
exquisitely accommodate themselves. He considers the requisites of
fluidity to be chiefly these: The smallness of the component particles,
their determinate figure, the vacant spaces between them, and the fact
of their being agitated variously and apart by their own innate motion
or by some thinner substance which tosses them about in its passage
through them. His published works contain many well-authenticated
chemical facts, which are commonly held to be the discovery of a
later time. He prepared acetone by the distillation of the acetates
of lead and lime; and he isolated methyl alcohol from the products of
the destructive distillation of wood. He was one of the earliest to
insist on the necessity of studying the forms of crystals. He saw in
their formation proof that the internal motions, configuration, and
position of the integral parts are all that is necessary to account for
alterations and diversities in outward character. Some of the stock
illustrations of our lecture-rooms were of his contrivance. Thus he
illustrated the expansive power of freezing water by bursting a plugged
gun-barrel filled with water by solidifying the water by means of a
mixture of snow and salt—a freezing mixture which he first introduced.

Boyle was the first to formulate our present conception of an element
in contradistinction to that of the Greeks and the schoolmen who
influenced the theories of the iatro-chemists. In the sense understood
by him, the Aristotelian elements were not true elements, nor were the
salt, sulphur, and mercury of the school of Paracelsus. He was also
the first to define the relation of an element to a compound, and to
draw the distinction we still make between compounds and mixtures. He
revived the atomic hypothesis, and explained chemical combination on
the basis of affinity. He contended that one of the main objects of
the chemist was to ascertain the nature of compounds; and thereby he
stimulated the application of analysis to chemistry. Boyle discovered a
number of qualitative reactions, and applied them to the detection of
substances, either free or in combination.

But Boyle’s greatest service to learning consisted in the new spirit
he introduced into chemistry. Henceforward chemistry was no longer
the mere helpmeet of medicine. She became an independent science, the
principles of which were to be ascertained by experiment; a science
to be studied with the object of discovering the laws regulating the
phenomena with which it is concerned—and hence elucidating truth for
truth’s sake. The old philosophy of the Greeks had, as we have seen,
become merged into the doctrine of the iatro-chemists; and this was now
to be purified from the theosophical mysticism with which Paracelsus
and his followers had enshrouded it. “The dialectical subtleties of
the schoolmen much more,” says Boyle, “declare the wit of him that
uses them than increase the knowledge or remove the doubts of sober
lovers of truth.... For in such speculative inquiries where the naked
knowledge of the truth is the thing principally aimed at, what does
he teach me worth thanks, that does not, if he can, make his notion
intelligible to me, but by mystical terms and ambiguous phrases darkens
what he should clear up, and makes me add the trouble of guessing at
the sense of what he equivocally expresses, to that of learning the
truth of what he seems to deliver.” The influence of the new spirit
thus infused into the science by Boyle is seen in the general style
of chemical literature at the end of the seventeenth century, when
compared with that of the close of the sixteenth. The mysticism and
obscurity of the alchemists were no longer tolerated.

Boyle was slender and tall, with a countenance pale and emaciated.
His constitution was delicate and his body feeble, and it was only
by strict attention to diet and regularity of exercise that he
accomplished what he did. Although he suffered occasionally from an
excessive lowness of spirits, there was nothing morose or ascetic
in his nature. He was never married, although, says his friend John
Evelyn, “few men were more facetious and agreeable in conversation with
the ladies whenever he happened to be engaged among them.”

Kindly, courteous, charitable; unaffected, and temperate in his
manner of life, Boyle enjoyed the respect and esteem of all his
contemporaries. It was said of him that he was never known to have
offended any person in his whole life by any part of his deportment.
He allowed himself a great deal of decent cheerfulness, and had about
him all the tenderness of good nature, as well as all the softness of
friendship. These gave him a large share of other men’s concerns, for
he had a quick sense of the miseries of mankind. Although a philosopher
in the broadest sense of that term, his peculiar and favourite study
was chemistry, “in which,” says Bishop Burnet, “he engaged with none
of those ravenous and ambitious designs that drew many into them. His
design was only to find out nature, to see into what principles things
might be resolved, and of what they were compounded.”

=John Kunkel=, born in 1630, was the son of an alchemist attached
to the Court of the Duke of Holstein. After serving his father for
some years, he obtained employment as chemist and pharmacist under
the Dukes Charles and Henry, of Lauenburg. He subsequently entered
the laboratory at Dresden of John George II., Elector of Saxony,
and, after teaching chemistry at the University of Wittenburg, then
famous as a medical school, he accepted an invitation to take charge
of the glass works and laboratory of the Elector of Brandenburg, at
Berlin. The laboratory was burnt down, and then Charles XI. of Sweden
called him to Stockholm and ennobled him as Baron von Lowenstiern. He
died in Stockholm in 1702. Kunkel’s chief work is his _Laboratorium
Chymicum_, published after his death. It was written in German. In
it Kunkel relates how he acquired possession of a knowledge of the
manufacture of Baldwin’s phosphorus, and of the phosphorus discovered
by Brand—perhaps the most important, as it certainly was one of the
most striking, of the chemical discoveries of the seventeenth century.
Kunkel did much to liberate chemical literature from the mysticism and
obscurity of alchemy. He was scornful of the theories of the adepts,
and contemptuous of their _tria prima_.

  I, old man that I am, who have been occupied with chemistry for
  sixty years, have never yet been able to discover their fixed
  sulphur, or how it enters into the composition of metals....
  Moreover, they are not agreed among themselves respecting the kind
  of sulphur. The sulphur of one is not the sulphur of the other. To
  that one may reply that each is at liberty to baptise his child as
  he likes. I agree: you may even, if you are so disposed, call an
  ass a cow; but you will never make anyone believe that your cow is
  an ass.

As to the alkahest he says:—

  There has been much discussion concerning this grand natural
  solvent. Some derive it from the Latin—_akali est_; others from the
  two German words _all geist_ (all gas); lastly, others say it is
  from _alles est_ (that’s all). As to myself, I do not believe in
  Van Helmont’s universal solvent. I call it by its true name—_alles
  Lügen heist_, or _alles Lügen ist_ (it is all a lie).

Kunkel discovered the secret of the manufacture of aventurine glass
and of ruby glass by means of the purple of Cassius—a product from
gold first obtained by a doctor of medicine of that name in Hamburg.
He made observations on fermentation and putrefaction—recognised that
alum was a double salt (_salduplicatum_); described the present method
of repairing pure silver, and of parting gold and silver by means
of sulphuric acid. He also described the mode of preparing a number
of essential oils, detected the presence of stearopten in oils, and
discovered nitrous ether.

=John Joachim Becher=, the son of a Lutheran minister, was born at
Speyer in 1635. Owing to the death of his father and the devastation
of the family property during the Thirty Years’ War, Becher had a
hard struggle with poverty during his youth, and led a restless,
wandering life. In 1666 he was Professor of Medicine in the University
of Mayence. Subsequently he went to Munich as head of the finest
laboratory in Europe, but, quarrelling with the Chancellor of the
Bavarian Court, betook himself to Vienna. After a short stay there, he
quitted Austria for Holland, and established himself in Haarlem. Here
he proposed to the States-General to extract gold from the sand-dunes;
but, the project failing, he left for England and visited the Cornish
mines. On the invitation of the Duke of Mecklenburg-Güstrow, he
returned to Germany. Shortly afterwards (in 1682) he died, in the
forty-seventh year of his age. Becher’s name is remembered mainly in
connection with his theory of combustion, which, as we shall see,
was subsequently developed by Stahl into the theory of Phlogiston—a
generalisation which dominated chemistry until near the close of the
eighteenth century.

=John Mayow=, born in Cornwall in 1645, was a practising physician,
whose name chiefly lives by virtue of his clear recognition of the
substance or principle in the air which is concerned in combustion,
the calcination of metals, respiration, and the conversion of venous
into arterial blood. This substance, which he found to be contained in
saltpetre, he called _spiritus igno-aëreus_ or _nitro aëreust_. Mayow
died at the age of thirty-four. Had he been able to follow up his
observations, he might have influenced very materially the development
of theoretical chemistry. As it was, he was practically overlooked by
his contemporaries, and the real significance of his work was not
appreciated until long afterwards.

=Nicolas Lemery=, also born in 1645, wrote a _Cours de Chimie_, one
of the best text-books of the time, which passed through as many as
thirteen editions, and was translated into English, German, Latin,
Italian, and Spanish.

In this book he strove, as he says, to express himself clearly, and to
avoid the obscurities which were to be found in the authors who had
preceded him.

  The fine imaginations of other philosophers concerning their
  physical principles may elevate the spirit by their grand ideas,
  but they prove nothing demonstratively. And, as chemistry is a
  science of observation, it can only be based on what is palpable
  and demonstrative.

Nicolas Lemery, who is not to be confounded with his son Louis, also a
chemist, made a considerable number of contributions to pharmaceutical
chemistry; and his _Pharmacopée Universelle_, _Dictionnaire Universel
des Drogues Simples_, and _Traité de l’Antimoine_ were standard works
in their day.

Lemery was at one time a Protestant, and on the revocation of the Edict
of Nantes fled to England; but, embracing Catholicism, he returned to
Paris, re-established his pharmacy, and was elected into the Academy in
1699. He died in 1715.

=William Homberg=, born in Batavia in 1652, was originally intended
for the profession of law, but, becoming attached to science, studied
botany and medicine in Padua, chemistry at Bologna and in London,
mechanics and optics at Rome, and anatomy at Leyden. In the course of
his travels he visited the mines of Germany, Hungary, Bohemia, and
Sweden. In 1682 he was invited to Paris by Colbert, and in 1691 was
made a member of the Academy and was placed by the Duke of Orleans in
charge of his laboratory—then one of the finest in Europe. Homberg
married the daughter of Dodart, the physician. She became an expert
_préparateur_, and was of great assistance to him in his experimental
inquiries. He first made known the existence of phosphorus in France,
discovered by Brand, of Hamburg, and he described the phosphorescent
salt associated with his name. He made important observations on the
saturation of alkalis by acids, and was aware that they combined in
different proportions. He was an industrious worker, and, with the
exception of Cassini, was the most active member of the Academy. He
died on September 24th, 1715.

Next to Boyle, perhaps the most active agent in emancipating chemistry
from the yoke of alchemy was Boerhaave, who, by his teaching as
Professor of Physic, raised the University of Leyden to the summit of
its fame.

=Hermann Boerhaave=, the son of a minister, was born near Leyden, in
1668. He occupied himself in turn with theology, classics, mathematics,
chemistry, and botany, when he turned to physic, and, after a course of
study at the University of Harderwyk, in Gelderland, began to practise.
In 1702 he was appointed to a lectureship, and eventually to the Chair
of Medicine, in the University of Leyden, of which he became Rector
in 1714. His reputation as a teacher spread throughout Europe, and
steadily increased until his death.

[Illustration: HERMANNUS BOERHAAVE

Medicinæ, Botanices, Chemiæ

& Collegii practici, in ACAD. LUGD. BAT.

PROFESSOR ORDINARIUS.

After a painting by T. Wandelaar]

Boerhaave was one of the most learned men of his age, and singularly
well cultured, not only in science but in history, poetry, and polite
literature. He conversed in English, French, and German, and read
Italian and Spanish with facility. “The Latin he spoke extempore in
lectures or conversation was so clear that, with his action, method,
and the aptness of his similes, he could level the most abstruse
points to the meanest capacities.”[2] He was fond of music, and a good
performer on several instruments, particularly the lute. He delighted
to welcome musicians to his house. His profession as a physician
brought him wealth, much of which he spent in horticulture; and the
garden of his country seat, nearly eight acres in extent, was enriched
with all the exotic trees he could procure and induce to flourish in
the climate of Holland.

    [2] Burton, _Life of Boerhaave_, p. 58 _et seq._

Boerhaave was of a robust frame and healthy constitution, early inured
to constant exercise and the inclemencies of weather. His stature was
rather tall, and his habit corpulent. He had a large head, short neck,
florid complexion, light brown curled hair (for he did not wear a wig),
an open countenance, and resembled Socrates in the flatness of his nose
and his natural urbanity. He died at Leyden on September 23rd, 1738, in
the seventieth year of his age.

As a chemist Boerhaave is chiefly known by his _Elementa Chemia_,
published in 1732—the most complete and most luminous chemical treatise
of its time, translations of which appeared in the chief European
languages. The work is divided into three main parts. The first is
concerned with the origin and progress of the art, and with the
personal history of its most distinguished cultivators. The second and
largest part deals with the attempt to form a system of chemistry based
on such observational matter as seemed well established. The third
consists of a collection of chemical processes relating to the analysis
or decomposition of bodies, grouped under the heads of “vegetables,”
“animals,” and “fossils”—the beginnings, in fact, of subdivision of the
science into organic and inorganic chemistry.

As regards his belief in alchemy, Boerhaave was an agnostic: he neither
affirmed nor denied the possibility of transmutation. In this respect
he resembled Newton and Boyle. Boyle, indeed, was singularly cautious
and reticent in his references to alchemistic matters. As was said of
him by Shaw, he was too wise to set any bounds to nature: he was not
prone to say that every strange thing must needs be impossible, for
he saw strange things every day, and was well aware that there are
powerful forces in the world of whose laws and modes of action he knew
nothing. With that wariness which was habitual to him, he was wont to
say that “those who had seen them might better believe them than those
who had not”; and he was modest enough to suppose that Paracelsus or
Helmont might conceivably know of agents of which he was ignorant.

Boerhaave unquestionably spent much time in the study of alchemical
works, particularly those of Paracelsus and Helmont, which he
repeatedly read. The _Philosophical Transactions_ of the Royal Society
contain the results of a laborious but fruitless investigation by
him on quicksilver, which he undertook in the hope of discovering
the seminal or engendering matter which, on the old theory of the
generation of metals, was supposed to be contained in mercury.
But although, as he relates, he tortured it by “conquassation,
trituration, digestion, and by distillation, either alone or
amalgamated with lead, tin, or gold, repeating this operation to 511
or even to 877 distillations,” the mercury appeared only “rather more
bright and liquid, without any other variation in its form or virtues,
and acquired very little, if any, increase of its specific gravity.”

=Stephen Hales= (1677–1761), an ingenious divine—he held the perpetual
curacy of Teddington, and lived practically the greater part of his
life there—distinguished as a physiologist and inventor, occupied
himself in chemical pursuits, and made a number of observations on the
production of gaseous substances. His results were communicated to the
Royal Society and subsequently republished, in a collected form, under
the title of _Statical Essays_. In these experiments he used methods
very similar in principle to those subsequently employed by Priestley.
It is evident from his description of his experiments that he must
have prepared a considerable number of gaseous substances—hydrogen,
carbonic acid, carbonic oxide, sulphur dioxide, marsh gas, etc.—but he
seems to have made no systematic attempt to study their properties,
as he considered that they were simply air, modified or “tinctured”
by the presence of substances which he regarded as more or less
fortuitous. Prior to the time of Black all forms of gaseous substance
were regarded as substantially identical—in fact, as being _air_,
as understood by the Ancients—a simple elementary substance. It was
Black’s study of carbonic acid which first clearly established that
there were essentially distinct varieties of gaseous matter.




CHAPTER VII

PHLOGISTONISM


Even before the appearance of _The Sceptical Chemist_ there was a
growing conviction that the old hypotheses as to the essential nature
of matter were inadequate and misleading. We have seen how the four
“elements” of the Peripatetics had become merged into the _tria
prima_—the “salt,” “sulphur,” and “mercury”—of the Paracelsians. As
the phenomena of chemical action became better known, the latter
iatro-chemists—or, rather, that section of them which recognised that
chemistry had wider aims than to minister merely to medicine—felt that
the conception of the _tria prima_, as understood by Paracelsus and
his followers, was incapable of being generalised into a theory of
chemistry. Becher, while clinging to the conception of three primordial
substances as making up all forms of matter, changed the qualities
hitherto associated with them. According to the new theory, all matter
was composed of a mercurial, a vitreous, and a combustible substance
or principle, in varying proportions, depending upon the nature of the
particular form of matter. When a body was burnt or a metal calcined,
the combustible substance—the _terra pinguis_ of Becher—escaped.

This attempt to connect the phenomena of combustion and calcination
with the general phenomena of chemistry was still further developed
by Stahl, and was eventually extended into a comprehensive theory of
chemistry, which was fairly satisfactory so long as no effort was made
to test its sufficiency by an appeal to the balance.

=George Ernest Stahl=, who developed Becher’s notion into the theory of
_phlogiston_ (φλογιοτός—burnt), and thereby created a generalisation
which first made chemistry a science, was born at Anspach in 1660,
became Professor of Medicine and Chemistry at Halle in 1693, physician
to the King of Prussia in 1716, and died in Berlin in 1734.

Stahl contributed little or nothing to practical chemistry; and no new
fact or discovery is associated with his name. His service to science
consists in the temporary success he achieved in grouping chemical
phenomena, and in explaining them consistently by a comprehensive
hypothesis.

The theory of phlogiston was originally broached as a theory of
combustion. According to this theory, bodies such as coal, charcoal,
wood, oil, fat, etc., burn because they contain a combustible
principle, which was assumed to be a material substance and uniform
in character. This substance was known as phlogiston. All combustible
bodies were to be regarded, therefore, as compounds, one of their
constituents being phlogiston: their different natures depended
partly upon the proportion of phlogiston they contain, and partly
upon the nature and amount of their other constituents. A body, when
burning, was parting with its phlogiston; and all the phenomena of
combustion—the flame, heat, and light—were caused by the violence
of the expulsion of that substance. Certain metals—as, for example,
zinc—could be caused to burn, and thereby to yield earthy substances,
sometimes white in colour, at other times variously coloured. These
earthy substances were called _calces_, from their general resemblance
to lime. Other metals, like lead and mercury, did not appear to burn;
but on heating them they gradually lost their metallic appearance, and
became converted into calces. This operation was known as calcination.
In the act of burning or of calcination phlogiston was expelled. Hence
metals were essentially compound: they consisted of phlogiston and a
calx, the nature of which determined the character of the metal. By
adding phlogiston to a calx the metal was regenerated. Thus, on heating
the calx of zinc or of lead with coal, or charcoal, or wood, metallic
zinc or lead was again formed. When a candle burns, its phlogiston
is transferred to the air; if burned in a limited supply of air,
combustion ceases, because the air becomes saturated with phlogiston.

Respiration is a kind of combustion whereby the temperature of the body
is maintained. It consists simply in the transference of the phlogiston
of the body to the air. If we attempt to breathe in a confined
space, the air becomes eventually saturated with the phlogiston, and
respiration stops. The various manifestations of chemical action, in
like manner, were attributed to this passing to and fro of phlogiston.
The colour of a substance is connected with the amount of phlogiston
it contains. Thus, when lead is heated, it yields a yellow substance
(litharge); when still further heated, it yields a red substance (red
lead). These differences in colour were supposed to depend upon the
varying amount of phlogiston expelled.

The doctrine of phlogiston was embraced by nearly all Stahl’s German
contemporaries, notably by Marggraf, Neumann, Eller, and Pott. It
spread into Sweden, and was accepted by Bergman and Scheele; into
France, where it was taught by Duhamel, Rouelle, and Macquer; and into
Great Britain, where its most influential supporters were Priestley and
Cavendish. It continued to be the orthodox faith until the last quarter
of the eighteenth century, when, after the discovery of oxygen, it was
overturned by Lavoisier.

During the sway of phlogiston chemistry made many notable advances—not
by its aid, but rather in spite of it. As a matter of fact, until
the time of Lavoisier few, if any, investigations were made with the
express intention of testing it, or of establishing its sufficiency.
When new phenomena were observed the attempt was no doubt made to
explain them by its aid, frequently with no satisfactory result.
Indeed, even in the time of Stahl, facts were known which it was
difficult or impossible to reconcile with his doctrine; but these
were either ignored, or their true import explained away. Although,
therefore, these advances were in no way connected with phlogiston,
it will be convenient to deal with the more important of them now,
inasmuch as they were made during the phlogistic period.

With the exception of Marggraf, Stahl’s German contemporaries
contributed few facts of first-rate importance to chemistry. =Pott=,
who was born at Halberstadt in 1692 and become Professor of Chemistry
in Berlin in 1737, is chiefly remembered by his work on porcelain,
the chemical nature and mode of origin of which he first elucidated.
=Marggraf=, born in Berlin in 1709, was one of the best analysts of his
age. He first clearly distinguished between lime and alumina, and was
one of the earliest to point out that the vegetable alkali (potash)
differed from the mineral alkali (soda). He also showed that gypsum,
heavy spar, and potassium sulphate were analogous in composition.
He clearly indicated the relation of phosphoric acid to phosphorus,
described a number of methods of preparing that acid, and explained the
origin of the phosphoric acid in urine.

Of the Swedish chemists of that period, the most notable was Scheele.

=Carl Wilhelm Scheele= was born in 1742 at Stralsund. When fourteen
years of age he was apprenticed to an apothecary at Gothenburg, and
began the study of experimental chemistry, which he continued to
prosecute as an apothecary at Malmö, Stockholm, Upsala, and eventually
at Köping on Lake Malar, where he died in 1786, in the forty-third year
of his age. During the comparatively short period of his scientific
activity Scheele made himself the greatest chemical discoverer of his
time.

[Illustration: CARL WILHELM SCHEELE.

From the statue by Börjeson at Stockholm.]

He first isolated chlorine, and determined the individuality of
manganese and baryta. He was an independent discoverer of oxygen,
ammonia, and hydrogen chloride. He discovered also hydrofluoric,
nitro-sulphonic, molybdic, tungstic, and arsenic, among the inorganic
acids; and lactic, gallic, pyrogallic, oxalic, citric, tartaric, malic,
mucic, and uric acids among the organic acids. He isolated glycerine
and milk-sugar; determined the nature of microcosmic salt, borax, and
Prussian blue, and prepared hydrocyanic acid. He demonstrated that
graphite is a form of carbon. He discovered the chemical nature of
sulphuretted hydrogen, arsenuretted hydrogen, and the green arsenical
pigment known by his name. He invented new processes for preparing
ether, powder of algaroth, phosphorus, calomel, and _magnesia alba_.
He first prepared ferrous ammonium sulphate, showed how iron may be
analytically separated from manganese; and described the method of
breaking up mineral silicates by fusion with alkaline carbonates.
Scheele’s contributions to chemical theory were slight and unimportant,
but as a discoverer he stands pre-eminent.

Of the French phlogistians we have space only to mention Duhamel and
Macquer.

=Henry Louis Duhamel du Monceau= was born at Paris in 1700. He was one
of the earliest to make experiments on ossification, and one of the
first to detect the difference between potash and soda.

=Peter Joseph Macquer= was born in 1718 at Paris. He investigated
the nature of Prussian blue (discovered by Diesbach, of Berlin, in
1710), worked on platinum, wrote one of the best text-books of his
time, published a dictionary of chemistry, and was an authority of the
chemistry of dyeing.

In addition to those already mentioned, the most notable names as
workers in chemistry in Great Britain during the eighteenth century are
Black, Priestley, and Cavendish.

=Joseph Black= was born in 1728 at Bordeaux, where his father was
engaged in the wine trade. A student of the University of Glasgow, he
became its Professor of Chemistry in 1756. In 1766 he was transferred
to the Chemical Chair of the University of Edinburgh, and died in 1799.
Black published only three papers, the most important of which is
entitled _Experiments upon Magnesia Alba, Quicklime, and Other Alkaline
Substances_. He proved that magnesia is a peculiar earth differing
in properties from lime. Lime is a pure earth, while limestone is
carbonate of lime. He showed that magnesia will also combine with
carbonic acid, and he explained that the difference between the mild
and caustic alkalis is that the former contain carbonic acid, whereas
the latter do not. He also explained how lime is able to convert the
mild alkalis into caustic alkalis. Simple and well known as these
facts are to-day, their discovery in 1755 excited great interest, and
marked an epoch in the history of chemistry. Black’s name is associated
with the discovery of latent and specific heat, and he made the first
determinations of the amount of heat required to convert ice into water.

[Illustration: JOSEPH PRIESTLEY.

From a mezzotint after Fuseli in the possession of the Royal Society.]

=Joseph Priestley=, the son of a clothdresser, was born in 1733 at
Fieldhead, near Leeds. When seven years of age, on the death of his
mother, he was taken charge of by his aunt, and was educated for
the Nonconformist ministry, eventually becoming a Unitarian. He was
first attracted to science by the study of electricity, of which he
compiled a history. At Leeds, where he had charge of the Mill Hill
congregation, he turned his attention to chemistry, mainly from the
circumstance that he lived near a brewery and had the opportunity
of procuring large quantities of carbonic acid, the properties of
which he carefully studied. He abandoned the ministry for a time to
become librarian and literary companion to Lord Shelburne, with whom
he remained seven years. During this time he industriously pursued
chemical inquiry, and discovered a large number of æriform bodies—viz.,
nitric oxide, hydrogen chloride, sulphur dioxide, silicon fluoride,
ammonia, nitrous oxide, and, most important of all from the point of
view of chemical theory, oxygen gas. Priestley’s work gave a remarkable
impetus to the study of pneumatic chemistry. It exercised great
influence on the extension of chemical science, and—in other hands
than his—on the development of chemical theory. The most important of
his contributions to science are contained in his _Experiments and
Observations on Different Kinds of Air_. This work not only gives an
account of the methods by which he isolated the gases he discovered,
but describes a great number of incidental observations, such as the
action of vegetation on respired air, showing that the green parts of
plants are able in sunlight to decompose carbonic acid and to restore
oxygen to the atmosphere. He was, in fact, one of the earliest to trace
the specific action of animals and plants on atmospheric air, and to
show how these specific actions maintained its purity and constancy of
composition. He initiated the art of eudiometry (gas analysis), and
was the first to establish that the air is not a simple substance,
as imagined by the ancients. Priestley is to be credited with the
invention of _soda-water_, which he prepared as a remedy for scurvy;
and his name is connected with the so-called _pneumatic trough_—a
simple enough piece of apparatus, but one which proved to be of the
greatest service to him in his inquiries.

After leaving Lord Shelburne, Priestley removed to Birmingham and
resumed his ministry. His religious and political opinions made him
obnoxious to the Church and State party; and during the riots of
1791 his house was wrecked, his books and apparatus destroyed, and
his life endangered. Eventually he emigrated to America, and settled
at Northumberland, where he died on February 6th, 1804, in the
seventy-first year of his age.

[Illustration: From a drawing by Alexander in the Print Room of the
British Museum.]

=Henry Cavendish= was born at Nice in 1731, and died in London in 1810.
He was a natural philosopher in the widest sense of that term, and
occupied himself in turn with nearly every branch of physical science.
He was a capable astronomer and an excellent mathematician, and he
was one of the earliest to work on the subject of specific heat, and
to improve the thermometer and the methods of making thermometric
observations. He also determined the mean density of the earth. He made
accurate observations on the properties of carbonic acid and hydrogen,
greatly improved the methods of eudiometry, and first established
the practical uniformity of the composition of atmospheric air. His
greatest discovery, however, was his determination of _the composition
of water_. He was the first to prove that water is not a simple or
elementary substance, as supposed by the ancients, but is a compound of
hydrogen and oxygen. In certain of his trials he found that the water
formed by the union of oxygen and hydrogen was acid to the taste; and
the search for the cause of this acidity led him to the discovery of
the _composition of nitric acid_. He was the first to make a fairly
accurate analysis of a natural water, and to explain what is known as
the _hardness of water_.

Phlogistonism may be said to have dominated chemistry during
three-fourths of the eighteenth century. Although radically false
as a conception and of little use in the true interpretation of
chemical phenomena, it cannot be said to have actually retarded the
pursuit of chemistry. Men went on working and accumulating chemical
facts uninspired and, for the most part, uninfluenced by it. Even
Priestley, perhaps one of the most conservative of the followers of
Stahl, regarded his dogma with a complacent tolerance; and as its
inconsistencies became apparent he was more than once on the point
of renouncing it. Of one thing he was quite convinced, and that was
that Stahl had greatly erred in his conception of the real nature of
phlogiston. Perhaps the most signal disservice which phlogiston did to
chemistry was to delay the general recognition of Boyle’s views of the
nature of the elements. The alchemists, it will be remembered, regarded
the metals as essentially compound. Boyle was disposed to believe that
they were simple. Becher and Stahl and their followers, until the last
quarter of the eighteenth century, also regarded them as compounds,
phlogiston being one of their constituents. On the other hand, what
we now know to be compounds—such as the calces, the acids, and water
itself—were held by the phlogistians to be simple substances.

The discovery, in 1774, of oxygen—the dephlogisticated air of
Priestley—and the recognition of the part it plays in the phenomena
which phlogiston was invoked to explain, mark the termination of one
era in chemical history and the beginning of another. Before entering
upon an account of the new era it is desirable to take stock of the
actual condition of chemical knowledge at the end of the phlogistic
period, and to show what advances had been made in pure and applied
chemistry during that time.

During the eighteenth century greater insight was gained into the
operations of the form of energy with which chemistry is mainly
concerned, and views concerning chemical affinity and its causes
began to assume more definite shape, chiefly owing to the labours of
Boerhaave, Bergman, Geoffroy, and Rouelle. It was clearly recognised
that the large group of substances comprised under the term “salts”
were compound, and made up of two contrasted and, in a sense,
antagonistic constituents, classed generically as acids and bases.

On the practical side chemistry made considerable progress. Analysis—a
term originally applied by Boyle—greatly advanced. It was, of course,
mainly qualitative; but, thanks to the labours of Boyle, Hoffmann,
Marggraf, Scheele, Bergman, Gahn, and Cronstedt, certain reactions
and reagents came to be systematically applied to the recognition of
chemical substances, and the precision with which these reagents were
used led to the detection of hitherto unknown elements. The beginnings
of a quantitative analysis were made even before the time of Boyle,
but its principles were greatly developed by him, and were further
extended by Homberg, Marggraf, and Bergman. Marggraf accurately
determined the amount of silver chloride formed by adding common salt
to a solution of a known weight of silver, and Bergman first pointed
out that estimations of substances might be conveniently made by
weighing them in the form of suitably prepared compounds, which, it
was implicitly assumed, were of uniform and constant composition. The
foundations of an accurate system of gaseous analysis were made by
Cavendish; and various forms of physical apparatus were applied to the
service of chemistry.

To the elements which were known prior to Boyle’s time, although not
recognised as such, there were added phosphorus (Brand, 1669), nitrogen
(Rutherford), chlorine (Scheele, 1774), manganese (Gahn, 1774), cobalt
(Brandt, 1742), nickel (Cronstedt, 1750), and platinum (Watson, 1750).
Baryta was discovered by Scheele, and strontia by Crawford. Phosphoric
acid was discovered by Boyle, and its true nature determined by
Marggraf; Cavendish first made known the composition of nitric acid.
As already stated, Scheele first isolated molybdic and tungstic acids
and determined the existence of a number of the organic acids (p. 75).
Other discoveries—such as the true nature of limestone and _magnesia
alba_ and their relations respectively to lime and magnesia by Black,
the many gaseous substances by Priestley, and the compound nature of
water by Cavendish—have already been referred to.

Technical chemistry also greatly developed during the eighteenth
century, thanks to the efforts of Gahn, Marggraf, Duhamel, Reaumur,
Macquer, Kunkel, and Hellot; and many important industrial
processes—such as the manufacture of sulphuric acid by Ward of
Richmond, and subsequently by Roebuck at Birmingham, and the Leblanc
process of conversion of common salt into alkali—had their origin
during this period.




CHAPTER VIII

LAVOISIER AND LA RÉVOLUTION CHIMIQUE


We have seen how chemistry made a new departure during the political
upheaval which occurred in this country about the middle of the
seventeenth century. It acquired a new impetus and took a fresh course
during the political cataclysm which overwhelmed France and alarmed
Europe towards the close of the eighteenth century. The instigator
and leader of this second revolution in chemistry was Lavoisier, one
of the most distinguished men of his age, and himself a victim of the
political fury of his own people.

=Antoine-Laurent Lavoisier= was born in Paris in 1743. At the Jardin
du Roi he came under the influence of Rouelle, one of the best
teachers of his time, who eventually shaped his career as a chemist.
In 1765 he sent to the Academy his first paper on gypsum, which is
noteworthy as giving for the first time the true explanation of the
“setting” of plaster of Paris, and the reason why overburnt gypsum
will not rehydrate. Three years later he became a member of the
_Ferme-général_—a company of financiers to whom the State conceded, for
a fixed annual sum, the right of collecting the indirect taxes of the
country. It was this connection that brought Lavoisier to the scaffold
during the revolution of 1794. Like Stahl, Lavoisier discovered no new
substance; but, also like Stahl, he created a new epoch by destroying
the philosophical system which Stahl had established.

It is commonly stated that the exception is a proof of the rule. The
history of science can show many instances whereby the rule has been
demolished by the exception. Little facts have killed big theories,
even as a pebble has slain a giant. During the reign of phlogiston
a few of such facts were not unknown—at least to some of the better
informed of Stahl’s followers.

Some of the alchemists had discovered that a metal gained, not lost,
weight by calcination. This was known as far back as the sixteenth
century. It had been pointed out by Cardan and by Libavius. Sulzbach
showed that such was the case with mercury. Boyle proved it in the case
of tin, and Rey in that of lead. Moreover, as knowledge increased it
became certain that Stahl’s original conception of the principle of
combustion as a ponderable substance—he imagined, with Becher, that it
was of the nature of an earth—was not tenable. The later phlogistians
were disposed to regard it as probably identical with hydrogen. But
even hydrogen has weight, and facts seemed to require that phlogiston,
if it existed at all, should be devoid of weight.

Towards the latter half of the eighteenth century clearer views
began to be held concerning the relations of atmospheric air to the
phenomena of combustion and of calcination; many half-forgotten facts
relating to these phenomena were recalled, and the inconsistencies
and insufficiency of phlogiston as a dogma became gradually manifest.
Three cardinal facts conspired to bring about its overthrow—the
isolation of oxygen by Priestley; the recognition by him of the nature
of atmospheric air, and of the fact that one of its constituents
is oxygen; and, lastly, the discovery by Cavendish that water is a
compound, and that its constituents are oxygen and hydrogen. The
significance of these facts was first clearly grasped by Lavoisier, and
to him is due the credit of their true interpretation. By reasoning
and experiment he proved conclusively that all ordinary phenomena of
burning are so many instances of the combination of the oxygen of the
air with the combustible substance; that calcination is a process of
combination of the oxygen in the air with the metal, which thereby
increases in weight by the amount of oxygen combined. Water—no longer a
simple substance—is formed by the union, weight for weight, of oxygen
and hydrogen. Lavoisier’s reasoning was so sound and his experimental
evidence so complete that his views gradually gained acceptance in
France. The phlogiston myth was thus exploded. Inspired by Lavoisier,
a small band of French chemists—Berthollet, Fourcroy, Guyton de
Morveau—thereupon set to work to remodel the system of chemistry
and to recast its nomenclature so as to eliminate all reference
to phlogiston. The very names “oxygen,” “hydrogen,” “nitrogen,”
corresponding respectively to the “dephlogisticated air,” “phlogiston,”
and “phlogisticated air” of Priestley, were coined by the new French
school. For a time _le principe oxygine_ was regarded by this school
in much the same relation as phlogiston was regarded by Stahl and his
followers. The one fetich was exchanged for the other. The combustible
principle—phlogiston—was renounced for the acidifying principle—oxygen.
The new chemistry for a time centred itself round oxygen, just as
the old chemistry had centred itself round phlogiston. The views of
the French school met with no immediate acceptance in Germany, the
home of phlogistonism, or in Sweden or England, possibly owing, to
some extent, to national prejudices. The spirit of revolution, even
although it might be an intellectual revolution, had not extended to
these countries. Priestley, Cavendish, and Scheele could not be induced
to accept the new doctrine. It was, however, accepted by Black, and
its principles taught by him in Edinburgh; and before the end of the
century it had practically supplanted phlogistonism in this country.
Some of those who, like Kirwan, had energetically opposed the new
theory ended by enthusiastically embracing it. Its introduction into
Germany was mainly due to the influence of Klaproth.

We further owe to Lavoisier the recognition of the principle which lies
at the basis of chemical science—the principle of the conservation of
matter. Lavoisier was not the first to introduce the use of the balance
into chemistry: quantitative chemistry did not actually originate with
him. Boyle, Black, and Cavendish, as a matter of fact, preceded him in
recognising the importance of studying the quantitative relations of
substances. Nevertheless, no one before him so clearly foreshadowed the
doctrine of the indestructibility of matter, and it was mainly through
his teaching that the balance came to be recognised as indispensable to
the pursuit of chemistry. Before his untimely death he had succeeded
in impressing upon the science the main features which at present
characterise it.

Lavoisier was one of the most distinguished men of his age, and his
merits as a philosopher were recognised throughout Europe. Indeed,
it is not too much to say that at the time of his death he was the
dominant figure in the chemical world of the eighteenth century.
In addition to his position as a member of the _Ferme-général_ he
was made by Turgot a commissioner of the _Régie des Poudres_; and
in this capacity he effected improvements in the manufacture and
refining of saltpetre, and greatly increased the ballistic properties
of gunpowder. He became Secretary of the Committee of Agriculture,
and drew up reports on the cultivation of flax, of the potato, and
on the liming of wheat; he prepared a scheme for the establishment
of experimental farms, and for the collection and distribution of
agricultural implements. He introduced the cultivation of the beet root
in the Blesois, and improved the breed of sheep by the importation of
rams and ewes from Spain. He was successively member of the Assembly
of the Orléanais, _Député suppléant_ of the States-General, and of
the Commune of Paris. In 1791 he was named Secretary and Treasurer of
the famous Commission of Weights and Measures, out of which grew the
international system, based theoretically on a natural unit, known as
the metric system, and now adopted by most civilised countries in the
world. He was not only the administrative officer of the Commission:
he contributed to the nomenclature of the system, and directed the
determination of the physical constants on which the measurements
rested, and especially the determination of the weight of the unit
volume of water on which the value of the standard of mass was based.
Lastly he was Treasurer of the French Academy until its suppression in
1793 by the Convention, which shortly afterwards ordered the arrest
of Lavoisier and others of the Fermiers-généraux—twenty-eight in all.
They were sentenced to be executed within twenty-four hours, and their
property confiscated. Coffinhal, who pronounced their doom, declared:
“_La republique n’a pas besoin de savants_.” Thus in the fifty-first
year of his age, perished the creator of modern chemistry—a victim to
the senseless, sanguinary fury of the “Friends of the People.” His
rectitude, his public services, the purity of his private life, the
splendour of his scientific achievements—all were unheeded. As Lagrange
said to Delambre: “It required but a moment to strike off this head; a
hundred years may not suffice to reproduce such another.”

[Illustration: LAVOISIER AND BERTHOLLET

in the Laboratory of the Sorbonne, Paris.]

Of the men who were associated with Lavoisier in the creation of what
was known at the period as the antiphlogistic chemistry, the most
eminent was Berthollet.

=Claude-Louis Berthollet= was born in Savoy in 1748, and, after a
medical education, became physician to the Duke of Orleans. Devoting
himself to chemistry, in 1781 he was made a member of the Academy,
and he became Government Commissary and Director of the Gobelins,
the chief tinctorial establishment of France. Although in the main
in agreement with Lavoisier, he never wholly subscribed to the idea
that all acids contained oxygen. He discovered the bleaching power of
chlorine, prepared potassium chlorate, and investigated prussic acid
and fulminating silver.

In his _Statique Chimique_, published in 1803, he combated the
partial and imperfect views of Bergman and Geoffroy with regard to
the operation of chemical affinity, and showed that the direction
of a chemical change is modified by the relative proportion of the
reacting substances and the physical conditions—temperature, pressure,
etc.—under which the change is effected. He was one of the first to
draw attention to a class of phenomena known as reversible reactions,
and gave a number of instances of their occurrence. Berthollet
pushed his conclusions so far that he was led to doubt that chemical
combination took place in fixed and definite proportions; and his views
gave rise to a memorable controversy between him and Proust, in which
the latter eventually triumphed.

Berthollet enjoyed a great reputation in his time, and played a
considerable part in the political history of his country. It was
largely to his zeal, sagacity, and skill in developing her internal
resources at a critical period when she was hemmed round by foreign
troops and her ports blockaded by British ships, that France was
saved from conquest. His life was more than once in jeopardy when
France was governed by a Committee of Public Safety; but his honesty,
sincerity, and courage even impressed Robespierre, and he escaped the
perils of the Great Terror. He was an intimate friend of Napoleon,
and accompanied him to Egypt as a member of the Institute. He died at
Arcueil in 1822.

Davy, who visited him at his country house in 1813, says of him:—

  Berthollet was a most amiable man; when the friend of Napoleon,
  even, always good, conciliatory, and modest, frank and candid.
  He had no airs, and many graces. In every way below La Place
  in intellectual powers, he appeared superior to him in moral
  qualities. Berthollet had no appearance of a man of genius; but one
  could not look on La Place’s physiognomy without being convinced
  that he was a very extraordinary man.

Other notable men of this period were Fourcroy, Vauquelin, Klaproth,
and Proust.

=Antoine-François Fourcroy=, the son of a pharmacist, was born at Paris
in 1755, and started his career as a dramatic author. On the advice
of Vicq d’Azir, the anatomist, he turned to medicine, and in 1784, by
the influence of Buffon, obtained the chair of Chemistry at the Jardin
du Roi, in succession to Macquer. He was an excellent teacher—clear,
orderly, and methodical. He had, indeed, a talent for oratory. This he
assiduously cultivated, and became one of the most popular lecturers of
his time in France. Ambitious and time-serving, he became embroiled in
the turbulent politics of the period, and, after a chequered career,
died, embittered and disappointed, in the fifty-fourth year of his
age. His chief services to science consisted in his works, _Système
des Connaissances Chimiques_ and _Philosophie Chimique_. These, no
less than his public lectures, did much to popularise the doctrines of
Lavoisier among his countrymen.

=Louis Nicolas Vauquelin=, the son of a Norman peasant, was born in
1763, and while a boy became assistant to an apothecary in Rouen. In
1780 he came to Paris, and entered Fourcroy’s laboratory. Much of the
experimental work published in Fourcroy’s name was actually done by
Vauquelin. He became a member of the Academy in 1791, Professor of
Chemistry at the Mining School, Assayer to the Mint, and subsequently
Professor of Chemistry at the Jardin des Plantes. On Fourcroy’s
death he was made Professor of Chemistry of the Medical Faculty of
Paris. Vauquelin was no theorist; he was, however, an excellent
practical chemist, and one of the best analysts of the period. He
made a large number of mineral analyses, more particularly for Hauy,
the crystallographer. He discovered the element _chromium_ in the
so-called red-lead ore (lead chromate) from Siberia. He also first made
known the existence of _glucinum_ in beryl. He described a method of
separating the platinum metals, and worked upon _iridium_ and _osmium_.
He investigated the _hyposulphites_, _cyanates_, and _malates_. He
discovered the presence of _benzoic acid_ in the urine of animals; with
Robiqet, he first isolated _asparagin_; with Buniva, _allantoic acid_;
and with Bouillon de la Grange, _camphoric acid_.

Vauquelin lived wholly for science, and had no other interests
than in his laboratory. He was pensioned in 1822, and died at his
birthplace—St. André d’Héberlot—in the sixty-sixth year of his age.

=Martin Heinrich Klaproth=, born in 1743 at Wernigerode, in the
Hartz, began life, like Vauquelin, as an apothecary’s apprentice at
Quedlinburg. Thence he went to Hanover, and ultimately to Berlin,
where he studied under Pott and Marggraf and entered the pharmacy of
Valentine Rose, father of Heinrich Rose, the distinguished chemist,
and Gustav Rose, the mineralogist. In 1788 he became a member of the
Berlin Academy, and, on the creation of the Berlin University in 1809,
was made Professor of Chemistry. As already stated, he was the first
chemist of eminence in Germany to adopt the antiphlogistic theory. He
was distinguished as an analyst. He discovered _tellurium_, analysed
_pitchblende_ and _uranit_, and first made known the existence of
_uranium_, _zirconium_, and _cerium_, which he termed “ochroita.” He
analysed _corundum_, and was an independent discoverer of _titanium_
and _glucinum_, termed by him _beryllium_. He made a large number of
analyses of minerals, such as leucite, chrysoberyl, hyacinth, granite,
olivin, wolfram, malachite, pyromorphite, etc. He continued actively at
work until his death, in the seventy-fourth year of his age.

Analytical chemistry is under great obligations to Klaproth. He
established a standard of accuracy never before approached; and much
of his analytical work, both as regards processes and results, is of
permanent value.

=Joseph Louis Proust=, the son of a pharmacist was born at Angers in
1761. He received his early training in chemistry from his father,
and, after studying under Rouelle in Paris, obtained an appointment
at the Salpetrière. Proust has the credit of being the first chemist
to make a balloon ascent—in a Montgolfier balloon with Pilatre de
Rozier. On the invitation of the King of Spain, he went to that
country to superintend certain chemical manufacturing processes. He
became Professor of Chemistry at the University of Salamanca, and
subsequently went to Madrid, where he was installed in a well-equipped
laboratory to enable him to examine the mineral riches of Spain. On
the breaking out of war his work was interrupted, and he was obliged
to leave Madrid. His laboratory was completely destroyed, and his
valuable collection of apparatus and specimens dissipated. Through the
good offices of Berthollet, Proust was offered a considerable sum of
money by Napoleon in order to induce him to turn his discovery of grape
sugar to practical account. Proust was, however, too broken in health
to undertake the work of a factory manager, and he retired to Mayence.
On the restoration of the Monarchy he was made a member of the French
Academy, his honorarium as an Academician being augmented by a pension
from Louis XVIII. He died in 1826, while on a visit to Angers, his
native place.

Proust is the discoverer of what is now styled “the law of constant
proportion,” which states that the same body is invariably composed
of the same elements, united in the same proportion. He was a skilful
analyst, and made numerous analyses of minerals; and he was one of the
earliest to undertake a systematic study of metallic salts of organic
acids.




CHAPTER IX

THE ATOMIC THEORY


The opening years of the nineteenth century were made memorable by the
promulgation of the atomic theory by John Dalton. The enunciation of
this theory, which affords a simple and adequate explanation of the
fundamental laws of chemical combination, marks an epoch in the history
of chemistry.

It may be desirable to trace, as briefly as possible, the successive
steps which led up to the generalisation which more than any other
has served to stamp chemistry as an exact science. That matter was
_discrete_—that is, that it was not continuous, but was composed of
ultimate particles—was, as already stated, imagined by the ancients,
and was part of the philosophy of Leukippus, Demokritus, and
Leucretius. But this supposition, although favoured by Newton and other
thinkers, had little or no scientific basis prior to the middle of the
eighteenth century. From that time onward a variety of chemical facts
gradually accumulated, many of which at the time of their discovery
had no obvious connection with pre-existing facts. It was reserved for
Dalton to point out how an extension and more precise definition of
the old doctrine would suffice to connect and explain them.

The first germ of an atomic theory based on chemical fact may be traced
in the observation of =Toburn Bergmann= (b. 1735, d. 1784), Professor
of Chemistry at Upsala, that neutral solutions of certain metals in
contact with other metals gave a precipitate without the neutrality of
the solution being disturbed, and without gas being evolved. One metal
had simply replaced the other in solution. Bergmann thus incidentally
discovered the fact of the chemical equivalence of metals. He was
of opinion, however, that the phenomenon meant a transference of
phlogiston from one metal to another, and that the process might be
made a mode of determining the relative amount of phlogiston in various
metals. Lavoisier extended Bergmann’s observations, and sought to show,
in effect, that the process afforded a means of determining the amounts
of the several metals which combined with one and the same quantity
of oxygen. But neither Bergmann nor Lavoisier really grasped the idea
of equivalence as we understand it to-day. It began to be appreciated
as the result of the work of =Jeremiah Benjamin Richter= (b. 1762,
d. 1807) and of =G. E. Fischer= on the mutual action of salts in
solutions, and on the determinations of the amounts of acid and bases
which respectively combine with one another. Methods of measurement of
the proportions in which substances combine were grouped by Richter
under the term _Stochiometry_.

However desirable it may be in the interests of history to indicate
the sequence of the surmises and facts which preceded the formulation
of the atomic theory, it is very doubtful whether Dalton was, to any
material extent, influenced by them. A self-educated man of lowly
origin, sturdily independent and highly original, he was accustomed
to rely upon his own faculty of observation and experiment for his
facts, and upon his own intellectual powers and mental energy for their
interpretation.

=John Dalton=, the son of a Quaker hand-loom weaver, was born at
Eaglesfield, in Cumberland, in 1766. While still a boy he took to
school-teaching, and acquired, in his leisure and by his own exertions,
a competent knowledge of mathematics and physical science. In 1793 he
was called to give instruction in mathematics, natural philosophy, and
chemistry at the Manchester New College, the Nonconformist academy—now
moved from Warrington—in which Priestley had formerly lectured. Here
he remained six years, leaving the college to take up an independent
position as a private tutor, so as to enable him the more freely to
pursue his scientific inquiries. In 1800 he became Secretary of the
Philosophical Society of Manchester, and remained connected, as an
official, with that institution until his death in 1844. The greater
number of his scientific communications were published by that society.
In the outset of his scientific career he was attracted to meteorology;
and it was probably its problems which led him in the first place to
experiment, and to speculate on the physical constitution of gases.
In the course of these observations he was led to the discovery
of the law of thermal expansion of gases, with which his name is
now generally associated. His speculations concerning the physical
constitution of gaseous substances, arising from the contemplation of
gaseous phenomena, led him to the conception that a gas is composed
of particles that repel one another with a force decreasing as the
distance of their centres from each other; and it is probable that in
this manner he familiarised himself with the idea of the existence of
atoms. His first insight into the laws of the chemical combination of
these atoms seems to have originated from his discovery that, when
two substances unite in different proportions, these proportions may
be expressed in simple multiples of whole numbers. Thus he found,
on examining the composition of marsh gas and of ethylene, both
hydrocarbons, that for the same weight of hydrogen there was twice the
amount of carbon in ethylene that there was in marsh gas. He then
examined the oxides of nitrogen, and found a similar regularity to
hold good in these compounds. Some time prior to the autumn of 1803
Dalton was led to the supposition that these regularities could be
satisfactorily explained by the assumption that matter is composed
of atoms having sizes and weights differing with each substance, but
of identical weight and size for any particular substance, and that
chemical combination consists in the approximation of these atoms. This
simple hypothesis explained all the facts then known. It explained the
constancy in the chemical composition of substances, which may be said
to have been established by Proust, and which is now formulated as the
Law of Constant Proportion—that the same body is invariably composed
of the same elements, united in the same proportion. It explained also
the fact discovered by Dalton that, when an element unites with another
in different proportions, the higher proportions are multiples of the
lowest—now formulated as the Law of Multiple Proportion. It further
explained the fact, which may be said to have been foreshadowed by
Richter, that when two bodies, A and B, separately combine with a third
body, C, the proportions of A and B which unite with C are measures or
multiples of the proportions in which A and B combine together. This
is known as the Law of Reciprocal Proportion.

[Illustration: JOHN DALTON.

From a painting by B. R. Faulkner in the possession of the Royal
Society]

Dalton’s theory was first made generally known by Thomas Thomson, in
the third edition of his _System of Chemistry_, published in 1807, and
was employed by Thomson in his paper on “The Oxalates of Strontium,”
published the same year in the _Philosophical Transactions_. The first
printed account by Dalton himself is contained in Part I. of his _New
System of Chemical Philosophy_, published in 1808, the substance of
which had been previously given in a course of lectures at the Royal
Institution, London, and subsequently repeated in Edinburgh and Glasgow.

The statement of his theory is contained in chapter iii. of this work,
under the heading “Of Chemical Synthesis,” and is accompanied by a
plate and explanation, of which a facsimile is given on pp. 130–1.

The facts upon which Dalton based his theory are incontrovertible; but
Dalton’s explanation of them was not universally accepted at the time
he gave it. Davy, who, of course, was familiar with the conception
of atoms as part of the Newtonian philosophy, objected to the term
“atomic weight” introduced by Dalton, and suggested the expression
“combining proportion”; and Wollaston, for similar reasons, proposed
the term “equivalent,” as denoting the constant quantity with which
bodies went in and out of combination. There is no doubt that the use
of these terms retarded the general acceptance of Dalton’s doctrine,
and, moreover, brought into the science a confusion which was not
finally dispelled, as we shall see, until during the second half of the
century.

[Illustration: ELEMENTS

_Simple_

_Binary_

_Ternary_

_Quaternary_

_Quinquenary_ & _Sextenary_

_Septenary_]

  The illustration on the preceding page contains the arbitrary marks
  or signs chosen to represent the several chemical elements or
  ultimate particles.

    Fig.
     1. Hydro. its rel. weight                                   1
     2. Azote                                                    5
     3. Carbone or charcoal                                      5
     4. Oxygen                                                   7
     5. Phosphorus                                               9
     6. Sulphur                                                 13
     7. Magnesia                                                20
     8. Lime                                                    23
     9. Soda                                                    28
    10. Potash                                                  42
    11. Strontites                                              46
    12. Barytes                                                 68
    13. Iron                                                    38
    14. Zinc                                                    56
    15. Copper                                                  56
    16. Lead                                                    95
    17. Silver                                                 100
    18. Platina                                                100
    19. Gold                                                   140
    20. Mercury                                                167
    21. An atom of water or steam, composed of 1 of
          oxygen and 1 of hydrogen, retained in physical
          contact by a strong affinity, and supposed
          to be surrounded by a common atmosphere
          of heat; its relative weight =                         8
    22. An atom of ammonia, composed of 1 of azote
          and 1 of hydrogen                                      6
    23. An atom of nitrous gas, composed of 1 of azote
          and 1 of oxygen                                       12
    24. An atom of olefiant gas, composed of 1 of carbone
          and 1 of hydrogen                                      6
    25. An atom of carbonic oxide composed of 1 of
          carbone and 1 of oxygen                               12
    26. An atom of nitrous oxide, 2 azote + 1 oxygen            17
    27. An atom of nitric acid, 1 azote + 2 oxygen              19
    28. An atom of carbonic acid, 1 carbone + 2
          oxygen                                                19
    29. An atom of carburetted hydrogen, 1 carbone
          + 2 hydrogen                                           7
    30. An atom of oxynitric acid, 1 azote + 3 oxygen           26
    31. An atom of sulphuric acid, 1 sulphur + 3 oxygen         34
    32. An atom of sulphuretted hydrogen, 1 sulphur
          + 3 hydrogen                                          16
    33. An atom of alcohol, 3 carbone + 1 hydrogen              16
    34. An atom of nitrous acid, 1 nitric acid + 1
          nitrous gas                                           31
    35. An atom of acetous acid, 2 carbone + 2 water            26
    36. An atom of nitrate of ammonia, 1 nitric acid
          + 1 ammonia + 1 water                                 33
    37. An atom of sugar, 1 alcohol + 1 carbonic acid           35

Dalton’s estimations of the relative weights of the atoms, or, to use
Davy’s phrase, the values of their combining proportions, were, as
might be expected, very rough approximations to the truth. This arose
partly from inadequate experimental data, and partly from uncertainty
as to the relative number of the constituent atoms which made up a
compound. Neither Dalton nor his immediate successors had any rational
or consistent method of determining the latter point. The view taken of
the composition of the compound decided what particular multiples or
sub-multiples of the values of the atomic weights of its constituents
were to be adopted. As Dalton, in many cases, had no real criterion to
guide him, he made the simplest possible assumptions; but these might
or might not be valid; and subsequent experience showed that in some
cases they were erroneous.

It was, however, generally recognised that these atomic weights,
combining proportions, or equivalents, as they were for a time
indifferently termed, were chemical constants of the highest
importance, both to the scientific chemist, who, apart from their
theoretic interest, had need of them in the course of quantitative
analysis, and to the manufacturing chemist, who required them for
the intelligent exercise of his operations; and accordingly a number
of chemists, very shortly after the promulgation of Dalton’s theory,
attempted to determine their values with all possible precision. Chief
among these was the Swedish chemist Berzelius, to whom science was
indebted for a series of estimations of atomic weights, which were long
regarded as models of quantitative accuracy, and stamped their author
as the greatest master of determinative chemistry of his age.

=Jöns Jakob Berzelius=, the son of a schoolmaster, was born near
Linköping, in East Gothland, Sweden, in 1779. Entering Upsala with
a view to the profession of medicine, he was attracted, under the
influence of Afzelius—or, rather, in spite of it—to the study of
chemistry, and, later, of voltaic electricity, then in its infancy.
While holding a number of minor appointments as a teacher of medicine,
pharmacy, physics, and chemistry, he was elected, in 1808, a member
of the Swedish Academy of Sciences, of which he became President in
1810. In 1818 he was made permanent Secretary of the Academy, and, by
means of a yearly subsidy, was enabled to devote himself wholly to
experimental science. He was ennobled in 1818, and on the occasion of
his marriage, in 1835, was created a baron of the Scandinavian kingdom.
He died in 1848.

Berzelius occupies a pre-eminent position in the history of chemistry,
and during a considerable portion of his lifetime exercised an almost
unassailable authority as a chemical philosopher. He is distinguished
as an experimenter, as a discoverer, as a critic and interpreter,
and as a lawgiver. His contributions to chemical knowledge range
over every department of the science. He shares with Davy the honour
of having established the fundamental laws of electro-chemistry.
His experimental work on the atomic weights of the elements—the
great work of his life—was of supreme importance at this particular
period of the development of chemistry: it served not only to give
precision to, and enhance the significance and value of, Dalton’s
generalisation, but it furnished chemists, for the first time, with
a set of constants, ascertained with the highest exactitude of which
operative chemistry was then capable, thereby contributing to the
expansion of quantitative analysis, and to a more exact knowledge of
the composition of substances. Berzelius, indeed, was an analyst of the
first rank—conscientious, patient, and painstaking; an ingenious and
skilful manipulator; inventive and resourceful. What determinative
chemistry owes to his labours, and not less to his example, is obvious
from even the most superficial examination of its literature during the
first third of the last century.

As a discoverer, Berzelius first made known the existence of _cerium_
(1803), of _selenium_ (1818), and of _thorium_ (1828); and he prepared
and investigated a large number of their combinations. He isolated
_silicon_ (1823), _zirconium_ (1824), _tantalum_ (1824), and studied
the compounds of _vanadium_, discovered by his countryman Sefström.
He largely extended our knowledge of groups of substances in which
sulphur replaces oxygen; investigated compounds of fluorine (1824),
platinum (1828), and tellurium (1831–1833), and made many analyses of
minerals, meteorites, and mineral-waters. He discovered _racemic acid_
and investigated the ferrocyanides. It was his investigation of racemic
acid—which has the same percentage composition as tartaric acid—that
first enabled him to grasp the conception of _isomerism_, a term which
we owe to him, and of _metamerism_ and _polymerism_. He was the first
to study the phenomena of contact-actions, which he comprehended under
the term _catalysis_.

[Illustration: JÖNS JAKOB BERZELIUS.

From a painting by J. G. Sandberg.]

As an author his literary activity was astonishing. His new system of
mineralogy marks an epoch in the history of that branch of science. His
text-book on chemistry was long the leading manual, and went through
many editions, being constantly revised by him. His annual reports on
the progress of physics and chemistry extended to twenty-seven volumes
and constitute a monument to his industry, thoroughness, perspicacity,
and critical ability.

Although holding no university appointment, and with a laboratory of
the most modest dimensions and character, Berzelius, exercised great
influence as a teacher. Some of the most notable chemists of the last
century, such as Heinrich and Gustav Rose, Dulong, Mitscherlich,
Wöhler, Chr. Gmelin, and Mosander, were among his pupils; and many of
them have testified to his stimulating power as an investigator of
nature, and to his merits as a worthy, genial man.

The reasonableness of Dalton’s conjecture received further support
from the discovery by Gay Lussac in 1808, that gases always combine
in simple proportions by volume, and that the volume of the gaseous
product formed, when measured under comparable conditions of
temperature and pressure, stands in a simple relation to the volumes
of the constituents. The law of pressure discovered by Boyle, that
of thermal expansion by Dalton, and of volumes by Gay Lussac (which,
it ought to be stated, was previously and independently made by
Dalton), are explained on the assumption that equal numbers of the
particles—either as simple particles or as compound particles—are
present in the same volume of the gas. This method of explanation was
first clearly stated by the Italian physicist =Avogadro= in 1811, but
its significance, as will be seen subsequently, was not appreciated
until half a century later.

As the values for the atomic weights gradually became more exact,
speculations arose as to the significance of the numerical relations
which were observed to exist among them. In 1815 =William Prout= threw
out the supposition that the atomic weights of the gaseous elements
are multiples by whole numbers of that of hydrogen. Extended into a
generalisation, this might be held to indicate that all kinds of matter
are so many forms of a primordial substance. Subsequent inquiry showed
that Prout’s “Law,” as it is sometimes called, was not tenable in its
original form. Certain elements, it was conclusively proved, had atomic
weights which were not whole numbers. Dumas subsequently modified the
law, after a redetermination of a large number of atomic weights,
by assuming that the substance common to the so-called elements had
a lower atomic weight than unity. Although there are a considerable
number of elements whose atomic weights, based upon the most
accurate determinations, are remarkably close to whole numbers, the
investigations of Stas and others afford no valid reason for believing
that Prout’s hypothesis, and the underlying supposition to which it has
been held to point, are justified by experimental evidence.




CHAPTER X

THE BEGINNINGS OF ELECTRO-CHEMISTRY


The first year of the nineteenth century is further memorable on
account of the invention of the voltaic pile, and by reason of its
application by =William Nicholson= and =Sir Anthony Carlisle= to the
electrolytic decomposition of water. This mode of resolving water into
its constituents made a great sensation at the time, mainly because
of the extraordinary method by which it was effected. It afforded an
independent and unlooked-for proof of the compound nature of water
by a method altogether differing in principle from that by which its
composition had been previously ascertained. The formation of water by
the combustion of hydrogen brought no conviction of its real nature
to a confirmed phlogistian like Priestley; and it is even doubtful
whether Cavendish ever fully realised the true significance of his
great discovery. But the fact that the quantitative results of the
analysis thus effected were identical with those of its synthesis, as
made by Cavendish and Lavoisier, admitted of only one interpretation.
This cardinal discovery may be said to have completed the downfall of
phlogiston.

The value of the voltaic pile as an analytical agent was nowhere more
quickly appreciated than in England. In the hands of Humphry Davy its
application to the analysis of the alkalis and alkaline earths led to
discoveries of the greatest magnitude.

=Humphry Davy= was born in Penzance in 1778. In the course of his
studies for the profession of medicine he was attracted to chemistry;
and he became chemical assistant to Dr. Beddoes, a former teacher of
chemistry at Oxford, but then living at Clifton, near Bristol. While
in the capacity of assistant and operator in Beddoes’s Pneumatical
Institute, Davy discovered the intoxicating properties of _nitrous
oxide_ (so called laughing gas), which brought him into prominence
and led to his engagement by the managers of the newly-created Royal
Institution in London as lecturer in chemistry in succession to
Garnett. He early began to experiment on galvanism, and soon succeeded
in developing the fundamental laws of electro-chemistry; and in 1807 he
effected the _decomposition of potash and soda_ by the application of
voltaic electricity—thereby establishing, what indeed had been surmised
previously, that the alkalis are compound substances. He subsequently
proved that this was also the case with the alkaline earths. Davy thus
added some five or six metallic elements to those already known.

These discoveries, perhaps the most brilliant of their time, afforded
additional evidence of the invalidity of Lavoisier’s assumption that
oxygen, as the name implies, was the “principle of acidity.” The
surmise, in fact, was already disproved by the case of water—a neutral
substance and devoid of all the recognised attributes of an acid. It
was still further disproved by the cases of potash and soda—strongly
alkaline compounds.

Additional evidence was adduced by Davy in demonstrating, in 1810,
that the so-called _oxymuriatic acid_, the _dephlogisticated
marine acid_ discovered by Scheele, contained no oxygen, but was
a simple, indivisible substance. For the old designation, which
connoted a compound body, he substituted the name _chlorine_, in
allusion to the characteristic colour of the element. In the course
of his investigation on this substance he discovered the _penta-
and trichloride of phosphorus_, _chlorophosphamide_ and _chlorine
peroxide_. He was also the discoverer of _telluretted hydrogen_ and an
independent discoverer of _nitrosulphonic acid_.

[Illustration: SIR HUMPHRY DAVY.

From a painting by Lawrence in the possession of the Royal Society.]

He worked on _iodine_ and the _iodates_, on the _diamond_, on the
so-called _fuming liquor of Cadet_, on _nitrogen chloride_, and on the
_pigments of the ancients_. Lastly, he invented the _miner’s safety
lamp_, with which his name will always be associated, effecting thereby
what was practically a revolution in coal-mining. He became President
of the Royal Society in 1820, and died at Geneva on May 29th, 1829, in
the fifty-first year of his age. Davy was a singularly gifted man, of
great mental vigour and imaginative power; quick, lively and ingenious;
an eloquent teacher and a daring and brilliant experimenter.

Another noteworthy name in the chemical history of this period is
Wollaston. =William Hyde Wollaston=, born at East Dereham, in Norfolk,
in 1766, was educated at Cambridge with a view to the profession of
medicine, but, failing to secure a practice, he devoted himself to
the pursuit of science, and especially to optics and chemistry. He
devised a method of _working platinum_, and was the first to make known
the existence of _palladium_ and _rhodium_. He was one of the most
ingenious and acute analysts of his time, and possessed remarkable
inventive powers. He investigated the nature of _urinary calculi_
and _chalk stones_. His paper on the _oxalates of potash_ was of
great service at the time as a demonstration of the law of multiple
proportions. He first drew attention to the existence in the solar
spectrum of what were subsequently termed the _Fraunhofer lines_; and
he invented the _reflecting goniometer_ and the _camera lucida_, and
a _slide rule_ for chemical calculations. He resembled Cavendish in
temperament and mental habitudes, and, like him, was distinguished
for the range and exactitude of his scientific knowledge, his habitual
caution, and his cold and reserved disposition. He died in 1828.

[Illustration: WILLIAM HYDE WOLLASTON.

From a painting by J. Jackson, R.A., in the possession of the Royal
Society.]

Almost immediately after the publication of Volta’s discovery attempts
were made—notably by Berzelius in Sweden and by Davy in England—to
prove that electrical and chemical phenomena are correlated and
mutually dependent. This assumption was more fully worked out by
Berzelius in 1812, and it served as the basis of a chemical system
which exercised considerable influence on chemical doctrine during the
first half of the nineteenth century.

Berzelius assumed that electric polarity was an attribute of all
atoms—that these were bipolar, in fact, but that in them either
positive or negative electricity predominated. Hence the elements
were capable of being divided into two classes—that is, positive or
negative, depending upon the excess of either charge. Which of the
electricities predominated might be ascertained by determining the
particular pole at which the element was separated on electrolysis.
Combinations of dissimilar elements—or, in other words, chemical
compounds—were also endowed with polarity. The chemical affinities of
elements and compounds were related to the excess of either kind of
electricity resident in them; and chemical combination resulted from,
and was a consequence of, the more or less perfect neutralisation
of the two kinds. From a study of the electrical deportment of the
elements Berzelius sought to arrange them in series, starting with
oxygen as the most electro-negative member.

These conceptions were employed by him as the basis of a method of
classification. The attempt is historically interesting as being the
first systematic endeavour to gain an insight into the constitution
of chemical compounds—that is, to determine the manner in which the
constituent atoms are grouped or arranged with respect to one another,
or, in other words, to distinguish between the empirical and the
rational composition of substances, which is the ultimate aim of modern
chemistry.

A necessary consequence of these views was that every compound was to
be considered as made up of two parts in electrically different states.
Thus baryta, consisted of a combination of the electro-positive barium,
combined with the electro-negative oxygen; it combined with sulphuric
oxide because the preponderating positive electricity it contained met
with the negative electricity which prevailed in the sulphuric oxide.
Generalising, it may be said that the basic oxides are invariably
the positive constituents of salts, whereas the acid oxides are the
negative constituents, as proved by the mode in which the two kinds of
oxides separated at the poles on electrolysis. Barium sulphate, then,
was to be regarded as made up of two entities—BaO and SO3—and hence was
to be called sulphate of baryta. Berzelius extended this conception
in order to explain the formation of double salts—such, for example,
as potash alum, which he regarded as a binary compound of positive
potassium sulphate and negative aluminium sulphate, each of which,
in its turn, could be resolved into an acidic and a basic oxide of
opposite electricities.

The dualistic notions of Berzelius led him to the construction of
a system of chemical nomenclature and notation which, in its main
features, has persisted to this day, and is universally current, with
certain modifications, in modern chemical literature. We owe to him
the grouping of the elements into metals and metalloids, and also our
present system of symbolic notation, whereby even complicated chemical
reactions may be expressed in a concise and intelligible manner.
Chemical symbols were used by the alchemists; but Berzelius first
suggested that a chemical symbol should not only represent the element
to which it refers, but also its relative atomic weight. Chemical
equations became quantitative as well as qualitative expressions of
the facts they denote. Such equations implicitly assumed that, to
use Davy’s words, chemistry had passed under the dominion of the
mathematical sciences. Professed mathematicians were, however, slow to
recognise that the phenomena of chemical action were capable of formal
mathematical treatment. Davy relates that on speaking to Laplace of
the atomic theory in chemistry, and expressing his belief that the
science would ultimately be referred to mathematical laws similar to
those he had so profoundly and successfully established with respect
to the mechanical properties of matter, the idea was treated in a tone
bordering on contempt.

Berzelius’s electro-chemical system, and the dualistic ideas associated
with it, were of considerable service when applied to the inorganic
branch of the science; but attempts to fit them to the facts of organic
chemistry, which began to accumulate rapidly after the first quarter of
the century, failed. Its inadequacy as a comprehensive generalisation
became more and more manifest, and it eventually fell. In fact, it may
be said to have received its death-blow by Davy’s discovery of the
elementary nature of chlorine, and by the recognition of the fact that
the acids do not necessarily contain oxygen. Davy and, later, Dulong
made it obvious that, if any one element was to be regarded as the
acidifying principle, it was hydrogen, and not oxygen; and, in a sense,
this view ultimately prevailed in the recognition of the acids as salts
of hydrogen.

In France the study of electro-chemistry was undertaken by Gay Lussac
and Thénard, largely owing to the action of the Emperor Napoleon,
who furnished the funds for the construction of a powerful galvanic
battery. The results were published, in 1811, under the title,
_Recherches Physico-Chimiques, faites sur la Pile_, etc. Gay Lussac,
whose name has already been mentioned as one of the discoverers of
the Law of Combination of Gases, played a considerable part in the
history of chemistry at this period. He was one of the earliest to
appreciate the importance of Dalton’s generalisation, and to point
out the significance of his own discovery in strengthening it. He was
probably led, in the first instance, to the recognition of the law of
gaseous combination by Berthollet’s work on the volumetric composition
of ammonia gas, and by his own discovery—made in 1805, in conjunction
with Humboldt, in the course of their analysis of atmospheric air—that
one volume of oxygen combined with exactly two volumes of hydrogen to
form water. The regularities thus indicated he found to be general: all
gases which are capable of chemical union combine in simple proportions
by volume, and the volume of the product, if a gas, always stands in
some simple relation to the volumes of the constituents.

=Joseph Louis Gay Lussac= was born in 1778, at Saint Leonard, studied
chemistry in Paris, and was associated in chemical inquiry with
Berthollet. As Eleve-Ingenieur in the École Nationale des Ponts et
des Chaussées he began the experimental work in physics and chemistry
upon which his fame rests. In 1804 he undertook, with Biot, a series
of balloon ascents for the purpose of investigating the physics and
chemistry of the upper regions of the atmosphere. In 1806 he became
Professor of Chemistry at the École Polytechnique, and in 1832
Professor at the Jardin des Plantes. He was one of the chief assayers
of the French Mint, and, as member of many commissions, exerted
considerable influence in official circles. He died in 1850.

Gay Lussac and Thénard were the first to devise a method of obtaining
potassium and sodium by a purely chemical process, whereby these
metals could be procured in far larger quantities than was at that
time possible by electrolytic means. They were thus enabled to make
use of the strong deoxidising power of these metals to effect a number
of reductions, notably that of boric oxide to _boron_. Gay Lussac and
Thénard were also the first to make known the existence of _boron
fluoride_. We further owe to Gay Lussac the discovery of _cyanogen_,
the first of the so-called compound radicals. He first prepared
ethyl iodide, investigated sulphovinic acid and grape sugar, studied
etherification and fermentation, etc. We are also indebted to him
for a method of determining vapour densities which proved of great
service in ascertaining the molecular weights of substances. He worked
on iodine and its compounds, discovered, with Welter, _thiosulphuric_
acid, and investigated fulminic acid in collaboration with Liebig.

Among his services to analytical chemistry were his method for the
analysis of gunpowder, his volumetric estimation of silver (wet silver
assay), chlorometric analysis, alkalimetry, etc. He devised the system
still in use in France for the estimation of alcohol in spirits of wine.

=Louis Jacques Thénard= was born in 1777 at Nogent-Sur-Seine, and was
a pupil of Vauquelin and of Berthollet. In 1797 he became _repétiteur_
at the Polytechnic School of Paris, and eventually its professor. He
subsequently occupied the chair of chemistry at the Collège de France,
and of the Faculty of Science of the University of Paris. He was
ennobled by Charles X. in 1824, and died at Paris in the eightieth year
of his age.

In addition to his work with Gay Lussac already mentioned, we owe
to Thénard the discovery of _hydrogen peroxide_ and _hydrogen
persulphide_. Together with Dulong he studied the catalytic action of
platinum on mixtures of oxygen and hydrogen. He investigated the fatty
acids, and worked on fermentation and on ether-formation; and he was
the first to isolate citric and malic acids. He also occupied himself
with the chemistry of bile, perspiration, albumen, the acids of urine
and milk, and with the theory of mordants.

In 1834 Faraday made known the important fact that on passing the same
galvanic current through a number of electrolytes—water, hydrochloric
acid, solutions of metallic chloride—these were decomposed in such
manner that definite amounts of hydrogen or metal were separated at the
negative pole, and corresponding amounts of oxygen or chlorine were
evolved at the positive pole. These observations were comprehended
by Faraday under his “law of definite electrolytic action.” The
electro-chemical equivalents thus obtained were in some cases identical
with the atomic weights deduced by Berzelius; in others they were
not; but, nevertheless, when they differed, they stood in some simple
relation to the assumed atomic weight. The significance of Faraday’s
observation was not lost sight of, although his anticipation that the
determination of electro-chemical equivalents would be of use in fixing
atomic weights was not immediately appreciated. A clear distinction
between the _equivalent_, the _atom_, and the _molecule_ was not
then apprehended. As will be subsequently shown, it was only during
the latter half of the nineteenth century that the discrepancies and
inconsistencies thus revealed were definitely reconciled and cleared
up.




CHAPTER XI

THE FOUNDATIONS OF ORGANIC CHEMISTRY


As the horizon of chemistry widened and its operations extended, it
became necessary to treat its subject-matter methodically. Accordingly
attempts were made in the various systematic treatises which began to
appear in the seventeenth century to group its facts into an orderly
and rational arrangement. One of the earliest of such systematic
treatises was the _Cours de Chimie_ of Nicolas Lemery, published in
1675. Although this work was styled by Boerhaave “a tumultuary mass of
pharmaceutical processes, without any certain design or coherence,” it
is noteworthy as being the first of its kind to divide the science into
its present main branches of inorganic and organic chemistry.

It may be desirable to indicate, as briefly as possible, the general
state of knowledge respecting the chemistry of organic substances
down to the early years of the last century. As already mentioned,
such substances as acetic acid, turpentine, starch, sugar, certain
dye stuffs, and oils, had long been known; and such processes as
saponification and fermentation had been practised from very early
times. The alchemists had prepared a variety of essential oils,
aliphatic ethers, and esters; and the iatro-chemists had obtained
benzoic and succinic acids, and acetic acid from wood. Milk sugar
was first prepared by Fabrizio Bartoletti in 1619. Grape sugar was
first mentioned as occurring in honey by Glauber in 1660. Boyle first
detected the presence of a spirit among the products of the destructive
distillation of wood. Few of the followers of Stahl occupied themselves
with organic products; and it was only towards the end of the
phlogistic period that attention was once more directed to products of
animal and vegetable origin. Scheele isolated glycerin in 1784, and
obtained _ethyl chloride_ by the distillation of a mixture of common
salt, pyrolusite, oil of vitriol, and alcohol. _Ethyl acetate_ was
first prepared by Lauraquais in 1759. Arvidson obtained _ethyl formate_
in 1777. _Oxalic ether_ was first made by Savary in 1773. What was
long known as _oil of wine_ appears to have been first mentioned by
Libavius, but its true nature was discovered by Hennel in 1826. The
formation of _aldehyde_ was first recognised by Scheele in 1774, and
it was in turn investigated by Fourcroy and Vauquelin, Döbereiner, and
Gay Lussac; but it was first definitely isolated in 1835 by Liebig, who
gave it its name.

The first organic acid known was vinegar (acetic acid), and for a
long time all naturally occurring organic acids having a sour taste
were regarded as identical with or as forms of vinegar. It was only
during the second half of the eighteenth century that it was clearly
ascertained that a variety of organic acids exist, perfectly distinct
from acetic acid. _Glacial acetic acid_ was first obtained by Löwiz
in 1789. Acetic acid, as a product of the destructive distillation of
wood, was first obtained by Göttling in 1779. The acetic fermentation
has been studied from very early times. Surmises as to the mode in
which wine was converted into vinegar are to be met with in the works
of Basil Valentine, Becher (1669), Lemery (1675), and Stahl (1667).
Priestley, for a time, held the opinion that vinegar contained a
vegetable acid air, but he subsequently discovered and corrected his
error. The direct conversion of spirit of wine (ethyl alcohol) into
acetic acid was studied by Lavoisier and Berthollet, who first clearly
recognised that it was a process of oxidation. The quantitative
composition of acetic acid was first established by Berzelius in 1814.
Many of the acetates have been known from early times. _Verdigris_ is
mentioned by Theophrastus, Dioscorides, and Pliny. _Zinc acetate_ was
known to Geber, and _potassium acetate_ to Pliny, who mentions its use
in medicine. _Ammonium acetate_ was also used in medicine as far back
as the beginning of the seventeenth century, and was particularly
recommended by the physician, Raymond Minderer. _Sodium acetate_ was
prepared by Duhamel in 1736. _Lead acetate_ was known in the fifteenth
century, and was styled by Libavius _saccharum plumbi quintessentiale_,
in allusion to its sweet taste. What was called by the alchemists _lac
virginis_ was a turbid solution of basic lead acetate, and it was
frequently used in medicine, more particularly by Goulard in 1760.
What we now call _acetone_ was first observed by Libavius, in 1595,
and subsequently by Boyle, during the destructive distillation of lead
acetate: its formation from other acetates was noticed by Trommsdorff,
Derosne, and Chenevix, by whom it was termed pyroacetic spirit. Its
true nature and composition were first ascertained by Liebig in 1831.

The formation of tartar in the manufacture of wine has been known
from the earliest times. It was regarded as, and originally styled,
the _faex vini_. The word “Tartarus” is first met with in alchemistic
literature in the eleventh century, and is the Latinised form of an
Arabic word. Marggraf, in 1764, recognised that the tartar of wine
contained potash; but tartaric acid itself was first isolated by
Scheele in 1769.

The _double tartrate of potash and soda_ was first prepared in 1672
by Peter Seignette, an apothecary of Rochelle, and was used by him
in medicine. _Tartar emetic_ was discovered by Adrian von Mynsicht
in 1631, and its true nature explained by Bergmann in 1773. _Racemic
acid_ was first mentioned by a wine manufacturer named Kestner, and
was recognised as an acid in 1819. Its relation to tartaric acid, with
which it is isomeric, was first explained by Berzelius, who gave it its
name.

The naturally occurring oxalates were long considered as identical with
tartar. _Oxalic acid_ was obtained by Scheele in 1776 by means of the
action of nitric acid upon sugar. This acid was further investigated
by Bergmann, who observed its decomposition by heat with the formation
of a gas burning with a blue flame. The identity of the naturally
occurring oxalic acid with that prepared from sugar was established
by Scheele in 1784. The quantitative composition of oxalic acid was
first ascertained by Dulong in 1815. _Mucic acid_ was discovered by
Scheele in 1780, and was studied by Fourcroy, who gave it the name it
now bears. _Pyromucic acid_ was also known to Scheele, and was observed
by Hermbstädt and Houton-Labillardière. _Camphoric acid_ was first
recognised by Bouillon-Lagrange and Vauquelin. _Suberic acid_ was
discovered by Brugnatelli in 1787.

That gum benzoin yielded a product (_benzoic acid_) by sublimation was
known in the sixteenth century. It was introduced into medicine by
Turquet de Mayerne as _flowers of benzoin_. Scheele showed how this
acid might be obtained by wet methods from gum-benzoin. It was detected
in Peru-balsam by Lehmann in 1709. Rouelle found it in the urine of the
cow and the camel. Liebig, in 1829, detected the difference between
_hippuric acid_ and benzoic acid. The characteristic acid in amber
(_succinic acid_) was first detected by Pott in 1753.

_Formic acid_ was first isolated by Wray in 1676. _Lactic acid_ was
discovered by Scheele in sour milk in 1780. For a time it was regarded
as impure acetic acid, until it was detected in muscle juice by
Berzelius, and its individuality established. Its true composition was
ascertained by Mitscherlich and by Liebig in 1832. _Citric acid_ has
been known since the thirteenth century, but it was first definitely
isolated by Scheele in 1784. Apple juice was used in medicine in the
sixteenth century, and the soda salt of its characteristic acid (_malic
acid_) was prepared by Donald Monro in 1767.

It was known to the ancients that extract of gall nuts acquired a
black colour when mixed with a solution of iron vitriol; and Boyle
and Bergmann ascribed this phenomenon to the presence of a peculiar
acid. _Gallic acid_ was first isolated by Scheele in 1785, and its
composition established by Berzelius in 1814. _Tannic acid_ was
definitely recognised as distinct from gallic acid by Seguin in 1795.

Mellite, or honey-stone, is mentioned in mineralogical treatises in the
sixteenth century. That it consisted of the alumina salt of a special
acid (_mellic acid_) was shown by Klaproth in 1799.

_Prussian blue_ was accidentally discovered in 1710 by a dyer named
Diesbach. Its mode of manufacture was first made known by Woodward
in 1724. The peculiar reaction by which it was obtained was made the
subject of investigation by many chemists of the period without any
decisive result. Scheele observed that, when the salt which occasioned
the blue colour with vitriol was distilled with sulphuric acid, a
volatile acid, inflammable and soluble in water, was obtained. This
acid received from Bergmann the name of _acidum cœrulei berolinensis_,
or “Berlin-blue acid,” subsequently shortened by Guyton de Morveau
to _prussic acid_. Scheele also prepared the cyanides of silver and
ammonium. That prussic acid was free from oxygen was established
by Berthollet. Anhydrous prussic acid was first obtained by Von
Ittner, who first established its highly poisonous nature. Bolim, in
1802, had previously observed the presence of prussic acid in oil
of bitter almonds, the poisonous character of which was known to
Dioscorides. Porret first definitely isolated _potassium ferrocyanide_,
and subsequently discovered the _thiocyanates_, the quantitative
composition of which was ascertained by Berzelius in 1820. That
prussic acid was a compound of hydrogen and cyanogen was established by
Gay Lussac in 1815.

_Cyanic acid_ was discovered by Wöhler in 1822, in which year also L.
Gmelin discovered the _ferricyanides_.

_Fulminating mercury_ was first prepared by Howard in 1800, and
_fulminating silver_ by Brugnatelli in 1802. These were recognised
by Liebig, in 1822, to contain a peculiar acid, which he termed
_fulminic acid_, and which he showed to have the same composition
as the cyanic acid discovered by Wöhler. _Uric acid_, so named by
Fourcroy, was discovered in gall stones by Scheele in 1776. _Urea_ was
first definitely isolated by Fourcroy and Vauquelin in 1799, and was
synthetically prepared by Wöhler in 1828.

The bitter principles of plants and their medicinal virtues early
attracted attention, but the first attempt to isolate them was made by
Fourcroy and Vauquelin in the case of the Peruvian bark, long known for
its power as a febrifuge. In 1806 Vauquelin obtained _quinic acid_.
_Cinchonine_ was first isolated by Gomes in 1811.

The chemical nature of opium was the subject of numerous inquiries in
the early years of the nineteenth century. In 1805 Sertürner detected
the existence of _meconic acid_, and in 1817 that of _morphine_, which
he recognised as an alkaloid. _Narcotine_ was discovered by Robiquet in
1835. The investigation of other bitter substances was undertaken by
Pelletier and Caventou, who in 1818 discovered _strychnine_, _brucine_
(1819), and _veratrine_ (1820).

The contemporaries and immediate followers of Lavoisier were the
first to make a systematic attempt to elucidate the chemical nature
of organic products of animal origin. To this period belongs the work
of Fourcroy and Vauquelin on animal chemistry. Chevreul, a pupil of
Fourcroy worked on urine, adipocire, and the animal fats in the first
decade of the last century. Kirchhoff in 1811, discovered the method
of converting starch into sugar; and Döbereiner, in 1822, described
a method of preparing formic acid artificially. Dumas and Boullay,
in 1827–1828, prepared a number of new derivatives of ethyl alcohol;
and in 1834 Dumas and Peligot studied in like manner the chemistry of
methyl alcohol, and pointed out many analogies which their compounds
possessed, not only among themselves, but also to inorganic substances.

Although a considerable amount of information as to the existence,
modes of occurrence, and properties of bodies found in the animal
and vegetable kingdoms had been accumulated by the end of the first
quarter of the nineteenth century, no serious attempt was made to
study them systematically until after that period. In fact, they
were not even regarded as coming within the operations of laws
found to be applicable to the products of the inorganic world, by
the investigation, of which products, indeed, those laws had been
discovered.

Down to 1828 it was considered that inorganic and organic substances
were sharply differentiated by the circumstance that, whereas the
former might be prepared by artificial means, and even built up from
their elements by synthetic processes in the laboratory, the latter
could only be formed in the bodies of animals and plants as the result
of vital force. In that year Wöhler showed that urea, pre-eminently
a product of animal metabolism, could be prepared synthetically from
inorganic materials. Other instances of a similar kind were discovered
in rapid succession; and the idea that organic substances could alone
be formed by vital processes was proved to be invalid. Moreover, large
numbers of substances of a character analogous to those produced by
physiological action, but not known to occur in the animal or vegetable
kingdom, were prepared. There is, therefore, no absolute distinction to
be drawn between the chemistry of the inorganic and organic worlds.

At the present day we mean by “organic compounds” simply the compounds
of carbon. These are so numerous, and frequently so complex, that
it is convenient to group them together and study them as a special
section of the science. At the outset it was supposed that only very
few elements entered into the composition of organic substances. This,
indeed, was held to be a point of fundamental distinction between
organic and inorganic compounds. Lavoisier was of opinion that all
organic bodies were combinations of carbon, hydrogen, and oxygen.
Berthollet first discovered the presence of nitrogen in a product
of animal origin. Sulphur and phosphorus were detected later. There
is apparently no _à priori_ reason why any element should not be
associated with carbon, and enter into the composition of an organic
compound.

Lavoisier was one of the first to devise methods for ascertaining
the composition of organic (carbon) compounds, and to indicate the
general principles by which the proportion of the elements met with
in these substances can be ascertained. So imperfectly, however, were
these methods worked out that it was not established until the close
of the first decade of the nineteenth century that organic compounds
even obeyed the law of multiple proportions. Thanks to the efforts
of Berzelius, Gay Lussac, and Thénard, and especially of Liebig, in
1830, methods of organic analysis were so far perfected that it became
possible to ascertain the empirical composition of these compounds
with certainty. This point reached, the development of this section
of chemistry proceeded with unexampled rapidity. Not only was the
composition of numbers of products, such as sugar, starch, the
vegetable acids, certain alkaloids, etc., established, but altogether
unlooked-for facts became manifest. One of the most surprising of these
was that of _isomerism_.

Up to the close of the first quarter of the nineteenth century it
seemed self-evident that substances of the same percentage composition
are necessarily identical. In 1823 Liebig showed that the silver
cyanate of Wöhler had the same composition as silver fulminate.
Faraday, in 1825, found a hydrocarbon in oil gas, which had the same
composition as olefiant gas, but was otherwise different from it; and
in 1828 Wöhler discovered that urea and ammonium cyanate—perfectly
dissimilar substances—were identical in elementary composition. Lastly,
Berzelius found this to be true of tartaric and racemic acids; and he
thereupon proposed the term _isomerism_ to denote the general fact.
He further pointed out that the phenomenon could only be explained
by supposing that the relative positions of the atoms in isomeric
compounds are different.

But the influence of molecular or atomic grouping in determining
the specific character of a substance is not confined to compounds.
The same phenomenon is observed to occur among the elements. It was
conclusively established by Lavoisier that the diamond and charcoal
are chemically the same thing—both forms of carbon. Scheele showed that
graphite was a third form of carbon. Phosphorus, sulphur, and oxygen
were subsequently shown to be each capable of existence in various
modifications. Instances of this character were grouped together in
1841 by Berzelius under the term _allotropy_.

The recognition of the fact of isomerism exerted a great influence
on the development of organic chemistry. It ultimately led to the
assumption that particular groups of elements or atomic complexes,
so-called _radicals_, were to be found in organic compounds—a
conception based originally on Gay Lussac’s discovery of _cyanogen_,
a combination of carbon and nitrogen, which was found to behave like
a simple substance, such as chlorine, and to give rise to compounds
analogous to the corresponding chlorides. This idea of the existence of
compound radicals was greatly strengthened by a memorable investigation
by Liebig and Wöhler, in 1832, on oil of bitter almonds and its
derivatives, in which they showed that these substances might be
represented as containing a special group or radical termed _benzoyl_,
which behaved like an element. The idea of groups of elements going
in and out of combination like a simple substance was not new to
chemists: there was not only the case of cyanogen, discovered by Gay
Lussac in 1815. The attempt had been made by Dumas and Boullay in
1828 to classify the derivatives of alcohol and ether as compounds
containing a common radical _etherin_. Gay Lussac had pointed out that
the vapour density of ethyl alcohol seemed to show that it consisted
of equal volumes of ethylene and water. Robiquet had also shown that
ethyl chloride might be assumed to be a compound of hydrochloric acid
and ethylene; and Döbereiner had regarded anhydrous oxalic acid as a
combination of carbonic acid with carbonic oxide.

But the investigation of Liebig and Wöhler served to give precision
to the conception. It thereby exercised a profound influence on the
development of organic chemistry by demonstrating, in effect, that
this branch of the science might be regarded as the chemistry of the
compound radicals, in contradistinction to inorganic chemistry—the
chemistry of the simple radicals. Additional support for this view
was afforded by the remarkable research by Bunsen on the so-called
_alkarsin_, the “fuming liquor of Cadet”—an evil-smelling substance
long known as being formed when an acetate is heated with arsenious
oxide. Bunsen showed that this liquid contained a compound radical
having arsenic as a constituent; and he prepared a series of
derivatives, all of which might be formulated as combinations of this
radical, which he termed _cacodyl_. The study of the electrolytic
decomposition of the acetates by Kolbe and the discovery of
_zinc-ethyl_ by Frankland afforded powerful support to the doctrine of
combined radicals.

Although there can be no doubt that this doctrine greatly stimulated
the pursuit of organic chemistry, it was gradually perceived that to
regard inorganic and organic chemistry as the chemistry respectively of
the simple and of the compound radicals was an imperfect and misleading
conception of the true relations of the two main divisions of the
science. Facts showed that the properties of a substance depend more
on the arrangement of its atoms than on their nature. The doctrine of
compound radicals was implicitly an attempt to extend the dualistic
conceptions of Berzelius to the facts of organic chemistry; and as such
it was welcomed by the great Swedish chemist. But dualism was found to
have its limitations, even in inorganic chemistry; and these were still
more apparent when it was sought to apply it in the other main branch
of the science. Attempts were therefore made—notably by the French
chemists Laurent, Dumas, and Gerhardt—to formulate organic substances
by methods in which the electro-chemical and dualistic conceptions of
Berzelius and his followers had no part. How these attempts developed,
and how they subsequently grew into the organic chemistry of to-day,
will be shown in the second part of this work.

It will be convenient also to delay any account of the personal history
of the creators of the science of organic chemistry—Liebig, Wöhler,
Dumas—until we are in a position to give a fuller statement of their
labours, and of the results which flowed from them. Although the
foundations of organic chemistry may be said to have been laid during
the closing years of the first half of the nineteenth century, the
superstructure was not erected until the second half.




CHAPTER XII

THE RISE OF PHYSICAL CHEMISTRY


Physics and Chemistry are twin sisters—daughters of Natural Philosophy;
like Juno’s swans, coupled and inseparable. Physics is concerned
with the forms of energy which affect matter; chemistry with the
study of matter so affected. Each, then, is complementary to the
other. Philosophers of old drew no practical distinction between
them, at least as regards their own studies. Men like Boyle, Black,
Cavendish, Lavoisier, Dalton, Faraday, Graham, Bunsen, were pioneers
“on a very broad gauge,” pushing their inquiries into territories
common to the two branches as their genius or inclinations directed
them. Accordingly, it has happened that many so-called physical laws
have been discovered by men who were professed chemists. It has also
happened that men who began their scientific career as chemists, like
Dalton, Regnault, and Magnus, eventually gave the whole of their
energies to physical measurements; or, like Black, Faraday, and
Graham, devoted themselves to the elucidation of physical problems. As
certain of these physical laws and problems have greatly influenced
the progress of chemistry, it becomes necessary, in any historical
treatment of the subject, to give some account of their origin, and to
show how they affected the development of chemical theory.

The relations of heat to chemical phenomena are so obvious and so
intimate that the study of their connection necessarily attracted
attention in very early times. But it was only when this study became
quantitative that any important generalisations became possible.
Most quantitative estimations of heat depend eventually upon the
thermometer; and thermometry is indebted to Englishmen in the first
instance for attempts to render the instrument trustworthy.

In this connection may be mentioned the names of Newton and Shuckburgh.
Brooke Taylor, in 1723, made a special study of the mercurial
thermometer as a measurer of temperature. In other words, he sought
to discover whether equal differences of expansion or contraction of
mercury corresponded to equal additions or abstractions of heat. The
results showed that the principle of the mercurial thermometer is valid
within at least the limits of temperature between the boiling and
freezing-points of water. These experiments were subsequently repeated
and confirmed by Cavendish, and, independently, by Black.

The discovery of the phenomenon of _latent heat_ by Black some time
prior to 1760 marks an epoch in the history of science. It was then for
the first time clearly recognised that the state of aggregation of a
substance is associated with a definite thermal quantity, and that, in
order to effect a change, a definite amount of energy, in the form of
heat, must be employed. The quantitative connection that exists between
work and energy was thus foreshadowed.

The doctrine of _specific heat_ was taught by Black in his lectures
at Glasgow between 1761 and 1765. The subject was subsequently
investigated experimentally by Irvine between 1765 and 1770, and by
Crawford in 1779. A series of determinations was published in 1781 by
Wilcke, in the _Transactions_ of the Swedish Academy. In these the
term _specific caloric_, since changed to _specific heat_, was first
used. About this time the determination of the amount of heat required
to raise substances through a definite interval of temperature was
made the subject of experiment by many observers, notably by Lavoisier
and Laplace, who greatly improved the calorimetric arrangements. The
values they obtained long remained the most trustworthy estimations of
the specific heats of substances. Their joint research had a further
influence on the development of thermo-chemistry by indicating the
general experimental conditions which were needed to ensure accuracy
in such determinations. Lavoisier and Laplace also measured, in
1782–1783, the heat disengaged by the combustion of substances, and
that evolved during respiration. In 1819 Dulong and Petit pointed out
that the specific heat of a number of substances, more particularly the
metals, were inversely proportional to their atomic weights; or, in
other words, the product of the specific heat into the atomic weight
was a constant. The nature of the relation will be seen from the
following table of certain of the results obtained by Dulong and Petit:—

    Element.  At. wt.  Spec. heat.  Atomic heat.

    Bismuth     208      0.0288         6.0
    Lead        207      0.0293         6.0
    Gold        197      0.0298         5.8
    Platinum    195      0.0314         6.1
    Silver      108      0.0570         6.1
    Copper       63      0.0952         6.0
    Iron         56      0.1138         6.4

It will be seen that these various elements have an uniform, or nearly
uniform, atomic heat—approximately 6.2 on the average.

This would appear to prove that, as Dulong and Petit expressed
it, “the atoms of simple substances have equal capacities for
heat.” The variations from a constant value are due partly to
errors of observation, but more particularly to the circumstance
that the substances compared are not all in a strictly comparable
condition—_e.g._, they are not all equally remote from their melting
points. It was shown, moreover, that the amount of heat needed to raise
a substance through a definite interval of temperature increased with
the temperature. The range of temperature through which a determination
was made in a particular instance affected, therefore, the value of
the specific heat. The most noteworthy departures from a uniform value
were observed to occur among the metalloids—_e.g._, carbon, the various
modifications of which had different specific heats—and generally among
elements of low atomic weight, in which the variation of specific heat
with temperature was particularly rapid.

Nevertheless, the significance of the generalisation discovered by
Dulong and Petit, in spite of its limitations, was quickly appreciated,
as it was perceived that a knowledge of the specific heat of an element
might be of great value in determining its atomic weight. The immediate
effect was that a certain number of the atomic weights fixed by
Berzelius mainly on chemical considerations were required to be halved.
Although subsequent experience has proved that the law of Dulong and
Petit is not capable of the simple mathematical expression they gave
it, it has shown itself to be of great value in fixing doubtful atomic
weights.

=Pierre Louis Dulong= was born in 1785 at Rouen, and, after studying
chemistry and physics at the Polytechnic School at Paris, became its
Professor of Chemistry and subsequently its Professor of Physics.
In 1830 he was made its Director of Studies; and in 1832 he became
permanent Secretary of the Academy of Sciences. As a young man he
worked with Berzelius, with whom he made the first approximately
accurate determination of the gravimetric composition of water. In
1811 he discovered the highly explosive _nitrogen chloride_, in the
investigation of which he was severely injured, losing an eye and
several fingers. He died in 1838. His collaborator, =Alexis Therese
Petit=, was born in 1791 at Vesoul, and died, when holding the position
of Professor of Physics at the Lycée Bonaparte, in 1820.

The attempt made by Neumann to extend Dulong and Petit’s “law” to
compound substances was only partially successful. Nor has any
important generalisation followed from our knowledge of the specific
heat of liquids. Almost simultaneously with the publication of Dulong
and Petit’s “law,” Mitscherlich made known the fact that similarity
in chemical constitution is frequently accompanied by identity of
crystalline form. Boyle, as far back as the middle of the seventeenth
century, had insisted upon the importance of the forms of crystals
in throwing light upon the internal structure of bodies. Romé de
l’Isle and Hauy had remarked that many different substances had the
same crystalline form. It had been observed that a crystal of potash
alum would continue to grow and preserve its shape in a solution of
ammonia alum; and similar observations had been shown to occur in
the case of vitriols. The invention of the reflecting goniometer by
Wollaston greatly facilitated the investigation of such phenomena.
Mitscherlich showed that the phosphates and arseniates of analogous
composition had the same crystalline shape, or, in other words, were
isomorphous. The same fact was observed to occur in the case of the
analogously constituted sulphates and selenates, and in that of the
oxides of magnesium and zinc, etc. The value of isomorphous relations
in determining the group-relationships of the elements and in deducing
the composition of salts was at once recognised by Berzelius, who
styled the discovery of isomorphism by his pupil Mitscherlich as “the
most important since the establishment of the doctrine of chemical
proportions.” The quantities of the isomorphously replacing elements in
a compound were regarded by him as a measure of their atomic weights;
and the principle was subsequently constantly employed by him, whenever
possible, as a criterion in fixing their values. Other investigators
have followed his example in this respect; and isomorphism is still
regarded as an important consideration in establishing the genetic
relations of an element.

=Eilhard Mitscherlich=, the son of a minister, was born in 1794 at
Neu Ende, near Jever, in Oldenburg, and, after studying philology
and oriental languages at Heidelberg, went to Paris, and thence to
Göttingen, where he occupied himself with natural science. In 1818
he repaired to Berlin and commenced to work on the arseniates and
phosphates, the similarity in the crystal-forms of which he was the
first to detect. His friend Gustav Rose, the mineralogist, thereupon
instructed him in the methods of crystallography; to enable him to
verify his discovery and to establish it by goniometric measurements.
In 1821 he joined Berzelius at Stockholm, where he pursued his
inquiries on the connection between crystal-form and chemical
composition. It was at the suggestion of Berzelius that he adopted the
term “isomorphy” to express this connection—the mechanical consequence
of identity of atomic constitution. In the same year he was appointed
Klaproth’s successor in Berlin, where he died in 1863.

Mitscherlich also worked on the manganates and permanganates, on
selenic acid, on benzene and its derivatives, and on the artificial
production of minerals.

The study of the physical phenomena of gases, initiated in 1660
by Boyle’s discovery of the law of gaseous pressure, has greatly
contributed to our knowledge of their intrinsic nature. Boyle himself
only proved his law in the case of atmospheric air; but the observation
was subsequently (1676) generalised by Marriotte. Charles, Dalton,
and Gay Lussac independently showed that gases have the same rate of
thermal expansion.

That gases are made up of particles possessing an internal movement was
surmised by the Greeks; but experimental evidence for such a view of
their constitution was first presented by Thomas Graham in 1829–1831,
when he discovered that gases move, or are diffused, at rates inversely
proportional to the square roots of their densities. Observations of a
like character, which found their explanation in Graham’s discovery,
had previously been made by Priestley, Döbereiner, and Saussure. This
interchange in the position of their particles is a property inherent
in gases. Inequality of density is not essential to diffusion. Graham
proved this by connecting together two vessels, one containing nitrogen
and the other carbonic oxide, which have the same density. After the
expiration of a certain time both gases were found to be uniformly
diffused through the vessels.

How these laws were found to be interdependent and mutually connected,
and how they led up to a molecular theory of gases which serves
to explain them, as well as certain other gaseous phenomena to be
subsequently noted, will be shown in the second part of this work.

By the end of the period with which we are concerned—that is, the
middle of the nineteenth century—a considerable body of information had
been accumulated as to the conditions which determine the different
states of aggregation of matter—that is, the conditions which allow of
the passage of the gaseous state into that of the liquid, and of the
liquid into that of the solid. That the same substance was capable of
existence in the three states of gas, liquid, and solid was of course
evident from the case of water. Even the most primitive races must
have realised that steam, dew, rain, snow, hail, and ice were only
modifications of one and the same substance. As knowledge increased,
other substances came to be known which resembled water in their
capacity for existence in various physical states. It was but natural
to assume that this was a general attribute, and that all substances
would, sooner or later, be found capable of existence in each of the
different conditions of aggregation.

Attempts were made during the first quarter of the last century to
prove that all the æriform bodies then known were simply vapours
more or less remote from their point of liquefaction, and still
further removed from their point of congelation. Monge and Clouet
condensed sulphur dioxide some time before 1800; and Northmore,
in 1805, liquefied chlorine. But these observations attracted
little attention until Faraday, in 1823, independently effected the
liquefaction of chlorine, and Davy that of hydrochloric acid. Faraday
almost immediately afterwards liquefied sulphur dioxide, sulphuretted
hydrogen, carbon dioxide, euchlorine, nitrous oxide, cyanogen, and
ammonia.

Other experimenters, among whom may be mentioned Thilorier and
Natterer, greatly improved the mechanical appliances for liquefying
these gases; liquid carbonic acid and nitrous oxide were obtained
in considerable quantities, and employed in the production of cold.
Certain of the gases—hydrogen, oxygen, nitrogen, nitric oxide, carbonic
oxide, etc.—resisted all attempts to liquefy them; and hence gaseous
substances came to be classified as _permanent_ and _non-permanent_,
depending upon whether they could or could not be liquefied. The
division was felt to be irrational even at the time it was made. There
seemed no _à priori_ reason why carbon dioxide and nitrous oxide should
be liquefiable, while carbonic oxide and nitric oxide should resist
all attempts to coerce them into changing their state. The real clue
to the conditions required to effect the liquefaction of a gas was
not discovered until nearly half a century later, when, as will be
shown subsequently, the arbitrary division of gases into permanent and
non-permanent was swept away.

The discovery of the law of gaseous combination by Gay Lussac, and the
recognition by Ampère and Avogadro of the relation between the density
of a gas or a vapour and its atomic weight, early led to improvements
in the methods of determining the absolute weights of gases and
vapours, especially by French chemists. Both Gay Lussac and Dumas
devised processes for determining vapour densities which were in use
until late in the century, and which, although now superseded by more
convenient and more rapid modifications afforded valuable information
concerning the molecular weights of substances and the phenomena of
gaseous dissociation.

During the first decade of the nineteenth century Dalton and Henry
discovered the simple law which connects pressure with the solubility
of a gas in any solvent upon which it exerts no specific action. Dalton
further developed the law so as to include the absorption by a solvent
of the several constituents of a gaseous mixture.

Attempts were made by Schröder, Kopp, and others, to discover
relations between the weights of unit volumes of liquids and solids
and their chemical nature; but such attempts were only partially
successful, owing to the difficulty of finding valid conditions
of comparison. By comparing the specific gravities of liquids
at their boiling-points Kopp succeeded in detecting a number of
regularities among their specific volumes which seem to indicate that
a comprehensive generalisation connecting them may yet be discovered.
Kopp has also shown that regularities exist among the boiling-points
of correlated substances, and that there is an interdependence between
the temperature of their ebullition and the chemical characters of
compounds.

This short summary will suffice to show that attempts to discover
relations between the physical attributes of substances and their
chemical nature were made more or less sporadically from the time
that chemistry was pursued in the spirit of science. But it is only
in recent times that any great accession to knowledge has resulted
from such efforts. The science of physical chemistry is practically a
creation of our own period. Its systematic study may be said to date
only from the last quarter of the nineteenth century, since which time
it has made extraordinary progress. Its broad features will be dealt
with in the second volume of this work.




BIBLIOGRAPHY

RELATING TO THE PERIOD COVERED BY VOL. I.


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Agricola, Georg. _Vom Bergwerck XII. Bücher darinn mit schöner
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Berthelot, Marcellin. _La Chimie des Anciens et du Moyenâge._
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Berthelot, Marcellin. _La Révolution Chimique._ Félix Alcan, Paris,
1890.

Berthollet, C. L. _Essai de Statique Chimique._ Firmin Didot, Paris,
1803.

Birch, Thomas. _Life of Boyle._ Millar, London, 1744.

Boerhaave, Hermann. _New Method of Chemistry._ Shaw and Chambers,
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Boulton, Richard. _Boyle’s Works Epitomised._ Phillips and Taylor,
London, 1699.

Burton, W. _Life of Boerhaave._ Lintot, London, 1746.

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Davy, John. _Life of Sir Humphry Davy._ Longmans, London, 1836.

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and Co., London, 1839.

Figuier, Louis. _L’Alchimie et les Alchimistes._ Victor Lecon, Paris,
1855.

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Paris, 1811.

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1869.

Grimaux, Edouard. _Lavoisier, 1743–1794._ Félix Alcan, Paris, 1888.

Henry, William Charles. _Life of Dalton._ Cavendish Society, London,
1854.

Hoefer, Ferdinand. _Histoire de la Chimie._ Two vols., Deuxième
édition. Firmin Didot Frères, Paris, 1866.

Jones, Bence. _Life and Letters of Faraday._ Longmans, London, 1870.

Kopp, Hermann. _Geschichte der Chemie._ Four vols. Braunschweig,
1843–47.

Kopp, Hermann. _Die Alchemie in älterer und neuerer Zeit._ Heidelberg,
1886.

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Meyer, Ernst v. _History of Chemistry._ Translated by George M’Gowan.
Macmillian and Co., London, 1891.

Nordenskiöld, A. E. _Carl Wilhelm Scheele._ Norsledt and Söner,
Stockholm.

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Paris, John Ayrton. _Life of Sir Humphry Davy._ Colbourne and Bentley,
London, 1831.

Priestley, Joseph. _Experiments and Observations on Different Kinds of
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Roscoe, H. E., and Harden, A. _A New View of the Origin of Dalton’s
Atomic Theory._ Macmillian and Co., London.

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Schubert, E., und Sudhoff, K. _Paracelsus’s Forschungen._ Frankfurt,
1887–89.

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Stahl, G. E. _Cheimia Rationalis_ (1720).

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Bentley, London, 1830.

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Wilson, George. _Life of Cavendish._ Cavendish Society, London, 1851.




INDEX


    Æneas Garæus, 35

    Agricola, Georg, 66

    Aidoneous, god of earth, 22

    Albertus Magnus, 40, 47

    Alchemy, 28
      and astrology, 36
      its character, 39

    Alkahest, 51

    Anastatius the Sinaite, 35

    Anaxagoras, 26

    Anaximenes, 21

    _Aqua regia_, 39

    Arabian learning, influence on Western Europe, 25

    Archæus, 59

    _Argentarium_, 10

    _Argentum vivum_, 11

    Aristotle, his doctrine of “elements”, 23
      his character as a man of science, 24

    Arnoldus Villanovanus (Arnaud de Villeneuve), 42, 47, 48, 51

    Arvidson, 155

    _Arrenichon_, 13

    _Ars Transmutatoria_, 46

    Artephius, 49

    Astrology and alchemy, 36

    Atoms, ancient theories of, 26

    _Atramentum_, 14

    _Aurichalcum_, 9

    _Auri pigmentum_ (orpiment), 13

    Averroes, 25, 38

    Avicenna, 38

    Avogadro, 181


    Bacon, Roger, 40, 41

    Bacon, Lord, 55

    Baldwin’s phosphorus, 80

    Bartoletti, Fabrizio, 155

    Basil Valentine, 43, 47, 49, 156

    Bathurst, Ralph, 74

    Becher, John Joachim, 81, 156

    Benther, David, alchemist, 53

    Bergman, 94, 107, 124, 158, 160

    Berigard de Pisa, 48

    Berthollet, Claude-Louis, 116 _et seq._, 156, 160, 164

    Berthelot, 37

    Berzelius, Jöns Jakob, 133, 156, 159, 160, 164

    Black, Joseph, 98 _et seq._, 171

    Bochart, 4

    Boerhaave, 3–20, 35, 42, 49, 51, 106
      his life and work, 84 _et seq._

    Bolim, 160

    Borri, 53

    _Botryitis_, 12

    Bouillon-Lagrange, 158

    Boullay, 162, 167

    Boyle, Robert 20, 72 _et seq._, 107, 113, 155, 157, 159, 175, 177

    Bragadino, alchemist, 53

    Brooke Taylor, 171

    Brugnatelli, 158, 161


    _Cadmia_, 12

    _Cœruleum_, 12

    Caligula, 34

    _Carbunculus_, 48

    Cardan, 110

    Cavendish, 94, 102 _et seq._, 107, 171

    Caventou, 162

    Cerium, its discovery, 121

    _Cerussa_, 10
      _usta_, 12

    _Chalcantum_ (copper sulphate), 12

    Charles, 178

    Chalybes, smelters of iron, 11

    Chemistry of the ancients, 1

    Chenevix, 157

    Chevreul, 54, 162

    Chlorine, discovery of, 107

    Chromium, discovery of, 120

    _Chrysocolla_, 12

    Cinnabar, use as pigment, 13

    Clouet, 180

    Clytemius, John, 54

    Cobalt, discovered by Brandt, 107

    Combining proportion, 129

    Conservation of matter, 113

    Conringius, Hermann, 51

    Copper, Egyptian, 8
      Roman, 9

    Cordus Valerius, 69

    Crawford, 107, 172

    Croll, Oswald, 65

    Cronstedt, 107

    Cyanogen, discovery of, 151


    Dalton, 125 _et seq._, 178, 181

    Davy, 29, 141

    Dee, John, 53

    Delambre, 116

    Demokritos, 26

    _De Re Metallica_, 66

    Derosne, 157

    Dickinson, 50

    Diodorus Siculus, 7

    Dioscorides, 156, 160

    Döbereiner, 155, 162, 167

    Dorn, 60

    Duchesne, 61

    Duhamel, 98, 157

    Dumas, 162, 167, 168, 181

    Dulong, 158, 173, 174

    Dyeing by the Egyptians, 14


    Egypt, birthplace of chemistry, 1

    _Electrum_, 8

    _Elementa Chemia_, 87

    “Elements,” Aristotelian, qualities of, 23

    _Elephantinum_, 14

    Elixir, 32

    Eller, 94

    Empedokles, 23

    Erastius, Thomas, 51

    Equivalent, 129


    _Fæx vini_, 137

    Fischer, G. E., 124

    Flos æris, 12

    Fourcroy, 112, 118, 155, 158, 161, 162

    Frankland, 168


    Gahn, 108

    _Gas sylvestre_, 63

    Gay Lussac, 150, 155, 161, 164, 167, 178, 181

    Geber, 36
      theory of metals, 37, 156

    Generation of metals, 33

    Geoffroy, 106

    Gerhardt, 168

    Glass, known to the ancients, 15

    Glauber, Johann Rudolf, 68

    Glucinum, its discovery, 120

    Gmelin, L. 161

    Gold, extraction by ancients, 7

    Goulard, 157

    Gomes, 161

    Göttling, 156

    Graham, Thomas, 178

    Gresham College, 74

    Gualdo, 49

    Guyton de Morveau, 112, 160


    _Hæmatinon_, 15

    Hales, Stephen, 89

    “Harmonics,” Paracelsian, 61

    Hauy, 176

    Hellot, 108

    Helmont, John Baptist van, 63

    Helvetius, 48

    Hennel, 155

    Henry, 181

    Herakleitos, 21

    Here, god of air, 22

    Hermbstädt, 158

    Hermes Trismegistus, 4, 33

    “Hermes of Germany, the”, 52

    Hoffmann, 106

    Homberg, William, 84

    Houton-Labillardière, 158

    Howard, 161

    _Hyalos_, use of, for kindling fire, 15

    _Hydrargyrum_, 11


    Iatro-chemistry, 57

    Ink of the ancients, 14

    Ingenhousz, 21

    Invisible College, the, 74

    Iron, use of, by the ancients, 10

    Irvine, 172

    Isaac of Holland, 49

    Isomerism, 165

    Isomorphism, discovery of, 176


    “Kalid,” his philosopher’s stone, 48

    _Key of Wisdom_, 53

    Kircher, 51

    Kirchhoff, 162

    Kirwan, 113

    Klaproth, 120, 160

    Klettenberg, Hector de, 54

    Kopp, 181

    Krohnemann, William de, 53

    Kunkel, John, 51, 79


    _Laboratorium Chymicum_, 80

    _Lac Virginis_, 157

    Lagrange, 116

    Laplace, 172

    Latent heat, 99, 172

    Lauraquais, 155

    Laurent, 168

    Lavoisier, 20, 22, 109
      antiphlogistic theory, 112, 116, 156, 164, 166, 173

    Law of Dulong and Petit, 173, 174

    Law of electrolytic action, 153

    Lead, known to the ancients, 10

    Leblanc, 108

    Lehmann, 159

    Lemery, Nicolas, 83, 154, 156

    Leo Africanus, 36

    Leukippos, 26

    Libavius, Andreas (Libau), 62, 155, 157

    Lieber, Thomas, 65

    Liebig, 155, 156, 159, 164, 167

    Löwiz, 156

    Lucretius, 26, 27

    Lully, Raymund, 41, 47, 49


    Macquer, 98

    Magistery, grand, 48
      small, 48

    _Magnesia alba_, nature of, 107

    Manganese, discovery of, 107

    Marggraf, 95, 107, 108, 157

    Marie Ziglerin burnt, 53

    Martian preparations, 37

    Marriotte, 178

    Maternus, Julius Firmicus, 35

    Mayerne, Turquet de, 65

    Mayow, John, 82 _et seq._

    Medicine and Astrology, 58

    _Melinum_, 13–14

    Menethes Sibonita, 3

    “Mercury,” as “element”, 31

    Mercury, receipt for fixing, 50

    Metallurgy of the ancients, 7

    Metals of the phlogistians, 104

    Minderer, Raymond, 157

    _Minium_, 12

    Mitscherlich, 159, 175, 176, 177

    _Molybdena_, 12

    Monge, 180

    Monro, Donald, 159

    Mordants, Egyptian, 15

    Mundamus, 43

    Mynsicht, Adrian van, 65, 158


    Narcotine, 161

    _Natron_, used as a detergent, 16

    Natterer, 180

    Nestis, god of water, 22

    Neumann, 94, 175

    _New System of Chemical Philosophy_, Dalton’s, 129

    Nickel, discovery of, 107

    Nitrogen, discovery of, 107

    Northmore, 180


    _Œrugo_, 12

    Oil of wine, 155

    _Okeanos_, 19

    Oleus Borrichius, 33

    Olimpiodorus, 35

    _Onychitis_, 12

    Operinus, 60

    _Ostracitis_, 12

    Oxides, metallic, used by ancients to colour glass 15

    Oxygen, its discovery, 105
      influence of, on chemistry, 105


    Palissy, Bernard, 67

    Paracelsus, 40, 48, 57

    _Paratonium_, 13

    Pelletier, 162

    Peligot, 162

    Peripatetic philosophy, influence on science, 24

    Petit, Alexis Therese, 173, 175

    Pherekides, 21

    _Philosophia Orientalis_, 38

    Philosopher’s Stone, 32, 46, 49

    Philosophical egg, 33

    Phlogistonism, 95 _et seq._

    Phosphorus, discovery of, 80, 107

    _Placitis_, 12

    Platinum, discovery of, 107

    Plato’s doctrine of “elements”, 23

    Pliny, 156

    _Plumbum album_, 10
      _nigrum_, 10

    Pope John XXII., alchemist, 46

    Porret, 160

    Pott, 94, 95, 159

    Price, James of Guildford, 54

    Priestley, Joseph, 20, 22
      his life and work, 99 _et seq._

    Proust, Joseph Louis, 121

    Purple of Cassius, 81

    _Purpurissum_, 13


    Quintessence of philosophers, 32


    Raquetaillade, Jean de, 43

    Realgar, 13

    Reaumur, 108

    Rey, 110

    Rhazes, 38

    Richter, Jeremiah Benjamin, 124

    Ripley, George, 43

    Robiquet, 161, 167

    Roebuck, 108

    Romé de L’Isle, 176

    Rose, Gustav, 177

    Rosenkreutz, Christian, 55

    Rouelle, 94, 106, 159

    Royal Society, foundation of, 74

    _Rubrica_, 13

    Rupecissa, Johannes de, 43


    _Saccharum plumbi quintessentiale_, 157

    Sala, Angelus, 65

    _Sal Armoniacum_, 44

    _Sal Duplicatum_, 81

    _Sal mirabile_, 68

    _Sandarach_, 13

    Saturnine solutions, 37

    Savary, 155

    Sceptical Chemist, The, 70

    Scheele, 96 _et seq._, 107, 155, 158, 159, 160, 166

    Schroeder, 181

    _Scoria æris_, 12

    Sefström, 135

    Seguin, 159

    Seignette, Peter, 157

    Selenium, its discovery, 135

    Sennert, Daniel, 65

    Sertürner, 161

    Severinus, 61

    Silver, known to the ancients, 7

    _Sinopis_, 13

    Soap, manufacture by Gauls, 15

    Specific heat, discovery of, 99

    _Spiritus igno-aëreus_, 82

    Stahl, George Ernst, 92, 156

    _Stannum_, 10

    _Statical Essays_ of Hales, 89

    _Statique Chimique_, 117

    Stephanus, 35

    _Stibium_, 13
      _Stimmi_, 13

    Strontia, discovery of, 107

    Suidas, 34

    “Sulphur,” as “element”, 31

    Sulzbach, 110

    Sun worship, 22

    Sylvius, Francis de le Boë, 64

    Syncellus, 35


    Tachenius, 69

    Tartarus, doctrine of, 59, 157

    Tellurium, discovery of, 121

    _Terra pinguis_ of Becher, 92

    _Tertiarium_, 10

    Tertullian, 19

    Thales of Miletus, 19

    Thénard, 152, 164

    Theophrastus, 156

    The Tincture, 32

    Thilorier, 180

    Thomson, Thomas, 129

    Thorium, its discovery, 135

    Thurneysser, Leonard, 53, 60

    Tin, known to the Egyptians, 9

    Transmutation, 28, 30

    Trommsdorff, 157

    Tubal Cain (Tuval-Cain), 7

    Turquet de Mayerne, 158

    Tyrian purple, 14


    Valentine, Basil, 43, 47, 49, 156

    Van Helmont, 20, 48, 63

    _Vasa murrhina_, 15

    Vauquelin, 119, 155, 158, 161, 162

    Verdigris, 56

    Vincent de Beauvais, 50

    Von Ittner, 160


    Wallis, John, 74

    Ward, Seth, 74

    “White” gold, 7

    Wilcke, 172

    Willis, Thomas, 64, 74

    Wöhler, 161, 163, 167

    Wollaston, 144, 176

    Woodward, 160

    Wray, 159

    Wren, Christopher, 74


    Zacharias, Daniel, 49

    Zozimus the Panopolite, 4




Transcriber’s Notes


Punctuation and spelling were made consistent when a predominant
preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced
quotation marks retained.

Ambiguous hyphens at the ends of lines were retained; occurrences of
inconsistent hyphenation have not been changed.

Index not checked for proper alphabetization or correct page references.

Page 16: “_jeunesse d’oreé_” was printed that way, but should be
“_jeunesse dorée_”.

Page 183: “Moyenâge” was printed that way, but should be “Moyen Âge”.