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THE

SCIENCE- HISTORY
OF THE UNIVERSE

FRANCIS ROLT - WHEELER

Managing Editor

KM TEN VOLUMES

THE CURRENT LITERATURE PUBLISHING COMPANY

NEW YORK

1909

INTRODUCTIONS BY

Professor E. E. Barnard, A.M., Sc.D.,
Yerkes Astronomical Observatory.

Professor Charles Baskerville, Ph.D., F.C.S.
Professor of Chemistry, College of the City of New York.

Director William T. Hornaday, Sc.D.,
President of New York Zoological Society.

Professor Frederick Starr, S.B., S.M., Ph.D.,
Professor of Anthropology, Chicago University.

Professor Cassius J. Keyser, B.S., A.M., Ph.D.,
Adrain Professor of Mathematics, Columbia University

Edward J. Wheeler, A.M., Litt.D.,
Editor of 'Current Literature.'

Professor Hugo Munsterberg, A.B., M.D., Ph.D., LL.D.f
Professor of Psychology, Harvard University.

EDITORIAL BOARD

Vol. I — Waldemar Kaempffert,
'Scientific American/

Vol. II — Harold E. Slade, C.E.

Vol. Ill — George Matthew, A.M.

Vol. Ill — Professor William J. Moore, M.E.,

Assistant Professor of Mechanical Engineering, Brooklyn

Polytechnic Institute.

Vol. IV — William Allen Hamor,

Research Chemist, Chemistry Department, College of the

City of New York.

Vol. V — Caroline E. Stackpole, A.M.,
Tutor in Biology, Teachers' College, Columbia University.

Vol. VI— Wm. D. Matthew, A.B., Ph.B., A.M., Ph.D.,

Assistant Curator, Vertebrate Paleontology, American

Museum of Natural History.

Vol. VI — Marion E. Latham, A.M.,
Tutor in Botany, Barnard College, Columbia University.

Vol. VII— Francis Rolt-Wheeler, S.T.D.

Vol. VII— Theodore H. Allen, A.M., M.D.

Vol. VIII— L. Leland Locke, A.B., A.M.,
Brooklyn Training School for Teachers.

Vol. VIII— Franz Bellinger, A.M., Ph.D.

Vol. IX— S. J. Woolf.

Vol. IX— Francis Rolt-Wheeler, S.T.D.

Vol. X — Professor Charles Gray Shaw, Ph.D.,
Professor of 'Ethics and Philosophy, New York University.

Leonard Abbott,
Associate Editor 'Current Literature/

THE

SCIENCE - HISTORY
OF THE UNIVERSE

VOLUME IV

CHEMISTRY

By WILLIAM ALLAN HAMOR

INTRODUCTION

By PROFESSOR CHARLES BASKERVILLE

Copyright, 1909, by
CURRENT LITERATURE PUBLISHING COMPANY

CONTENTS

Introduction by Professor Charles Baskerville
chapter pj9ge

I Development of the Chemical Conception. i

II Chemical Knowledge of the Ancients 8

III The Early Alchemists 23

IV The Later Alchemists 43

V The Iatro-Chemical Period 61

VI The Early Phlogistic Period 88

VII The Phlogistic Period Proper 101

VIII Special Branches in Phlogistic Period.... 124

IX Lavoisier and Anti-Phlogisticism. 149

X The Atomic Theory and Davy 173

XI The Atomic Theory and Berzelius 201

XII The Development of Organic Chemistry... 219

XIII Valence and Stereo-Chemistry 238

XIV Modern Inorganic Chemistry 252

XV Atomic Weights and Periodic Law 272

XVI The Development of Applied Chemistry. .. . 300

INTRODUCTION

Technically it is difficult, almost impossible, to draw-
sharp distinctions between the various subdivisions of
natural science. Omitting consideration of mathematics,
which constitutes a necessary, and convenient mode of
numbering, diagrammatization and quantitative interpreta-
tion of natural as well as of other phenomena — a clear and
concise language — the fundamental sciences are physics
and chemistry. Within the last half century the border-
land of these two has become so elastic in its boundaries,
that there has developed again an original science so
closely involving the characteristics of the two fundamen-
tal ones that it is called physical chemistry. With a clear
understanding of the foregoing ther should be no misin-
terpretation of what follows in this "Introduction" or
failure to appreciate what has been set forth within the
covers of this book by its author.

Chemistry took its origin out of knowledge of small
mysteries. Even today many may reasonably look with
wonder at the accomplishments of the chemist, who seems
to be a master at massive as well as at diminutive legerde-
main. Unfortunately, at times it is assumed that he knows
more than he does, and some, as in the charlatan days,
pretend to be wiser than they are. The history of chemis-

x INTRODUCTION

try for the past two centuries has been the history of the
progress of civilization. Its careful student will draw
from it values that are cultural, material and moral.

Its educational value depends upon the accuracy it gives
one's powers of observation, training in the correlation of
the facts observed, tracing the underlying laws thus
brought out, and the stimulation of the imagination to
bring other facts, apparently not in conformity with the
laws, into harmony with them or to so alter the explana-
tions secured as to include the seeming exceptions. Thus
theories, propounded as a logical sequence, which, as Shen-
stone has said, are as "searchlights which cast light into
dark places and enable us to see, sometimes plainly, some-
times only in dim outline, much that would remain hidden
if we were denied their aid," are scrapped like so much
old metal when their usefulness ends. So the history of
chemistry, like the history of inventions, "definable as a
method for utilizing a discovery," often reads like a
romance.

The material value of chemistry has had to do with our
wealth, health and happiness. Chemistry, by the utiliza-
tion of much of the wastes of the world, has produced
great wealth, as is seen in the numerous dyes, synthetic
medicines, etc., which have been made from coal-tar. It
has also saved injurious wastes. At some of the great
copper smelters to-day, where the sulphur gases were for-
merly turned loose into the air to the destruction of for-
ests, they are now converted into the cheap but valuable oil
of vitriol, upon the use of which there is scarcely anything
we eat, drink or wear that is not directly or indirectly de-
pendent. In fact, one may judge the financial progress of

INTRODUCTION xi

a nation by the annual production or consumption, or both,
of this acid. The industries of nations have been changed
through the influence of applied chemistry. The old mad-
der fields of France are now vineyards, the madder dye
(alizarin) being made by German processes in a factory.
So the millions of acres formerly given to the cultivation
of the indigo plant may help feed England when they are
cultivated for food products, as the Germans now manu-
facture a higher grade of indigo, at a lower price, than was
formerly obtainable commercially from the natural
sources, even with the poverty wages paid in India.
Through the application of the principles of chemistry,
better products have been produced at cheaper prices and
thus made available for more people. Substances possess-
ing little or no practical use, rare curiosities for the chemi-
cal museum, have become of great actual value. This may
be seen in the development of incandescent gas lighting.

We have only recently come to an awakened conscience
of fuel. The quantity of fuel required to produce the
energy for an industrial process is dependent upon the
manner in which it is required to do its work. Once smoke
was regarded as an evil, then a nuisance ; now it is known
as a waste, and none has better cause to wage war against
it than he who produces it. A smoking chimney is a thief,
not only because it projects visible unburned carbon into
the atmosphere, but in nine cases out of ten on account of
the invisible gases which are hot and combustible. Re-
generated gas heating not only prevents smoke, but is a
powerful means of economizing heat. It has been esti-
mated that the saving of national wealth effected by its
universal application would amount to a sum sufficient to

xii INTRODUCTION

pay the aggregate national debts of all the civilized nations.
What a horn of plenty may be seen outlined in the dense
smoke hanging like a pall over some of our cities in this
country !

The problem of energy, usually expressed in terms of
fuel, is a most serious one to every nation. Upon the in-
vention of the steam engine the days of the windmill and
old-time water-wheel seemed to be numbered ; sailing ships
gave way to mechanically driven vessels; gas-explosion
engines and electric power applied to motor vehicles are
driving out the horse, without whose aid at one time it was
thought that no civilized nation could exist, and have given
us a propelling force with which the air is navigated. In
some ways there is a disposition to revert in part to the
old order of things, as shown in the utilization of water
power with improved appliances. Inventors are not with-
out hope of utilizing the ocean tides; in fact, several in-
stallations where this is done do exist. The indefinite
hope of some imaginative people that we may secure some
unknown source of energy, however, is at present an
undependable and gratuitous assumption. Therefore, it is
of the utmost importance that the strictest economy be
practiced in the expenditure of our fuel capital.

The conversion of the force of gravity into electrical
energy by means of falling water has given an enormous
impetus to progress in applied chemistry. Not only has it
made the production of new and useful substances possible,
as carborundum and artificial graphite, but it has cheapened
the production of other materials, as caustics, "bleach,"
copper, aluminium, etc., in money values that involve large
figures, and promises to render available bodies of metallic

INTRODUCTION xiii

ores formerly regarded worthless. Cable news tells us
of the renewal of the German potash syndicate which con-
trols the natural deposits of potash salts at Stassfurt and
lays heavy tribute upon every farmer who uses mixed
fertilizers. Electrical energy may yet- give relief from
such a tax upon every civilized person in the world, for
laboratory experiments have shown the possibility of util-
izing the abundant insoluble, hence unavailable, source of
potash, a necessary element for plant growth, which exists
in every soil, but in comparatively small, yet sufficiently
large, amounts.

Perhaps the most important practical forward steps
taken in applied chemistry in recent years have been along
the line of the utilization of atmospheric nitrogen. No
living thing, plant or animal, is known which does not con-
tain nitrogen. Nitrogen is, therefore, necessary; it is the
most expensive, yet abundant and easily wasted, element of
plant food. The air contains 3,900 billion tons of this ele-
ment, but it is not available, except to a limited degree, as
a food. It must be properly combined with other elements
for plants to feed upon it. This has recently been accom-
plished commercially, and its importance is realized when
attention is drawn to the known sources of nitrates, and
the fact is recognized that the visible supply will not suffice
for the life of two generations at the normal rate of in-
crease both in population and productivity of the soil. For-
tunately, the processes devised in this day of wonderful
surprises do not participate in the destruction of valuable
coal deposits in obtaining the energy, but use "white coal,"
which, with the constant aid of nature, through the prin-
ciples of evaporation and condensation, may be used over

xiv INTRODUCTION

and over again. To this end it has stimulated the efforts
of many toward the conservation of the forests, for upon
these depend a constant supply of water and the avoidance
of devastating freshets which destroy the power plants.

The solution of problems of preventive medicine — that
is, sanitation — the development of aseptic surgery, the dis-
covery of anaesthesia, have been contributions of chemistry
to human happiness. The chemist has sought and is seek-
ing the establishment of uniform grades and international
standards and agreed methods for determining them for
products of exchange. Those familiar only with the secu-
lar press accounts of the struggles for pure food and drink
and distinctive labels therefor realize what this means. To
accomplish the refinements of this improvement in com-
munal and international morals, however, will require a
recasting of the meaning of many words in every language.
This cannot fail to promote in a measure the development
of a desirable universal language for all nations.

While the history of chemical economics is one of fasci-
nating interest, it must not be forgotten that these allot-
ments to the benefits of the living are in the end dependent
upon pure chemistry. In most cases they have resulted
from the application of principles derived from facts which
presented no utilitarian aspect in themselves, and the prin-
ciples, too, appeared to have only the remotest connection
with utility. It is not intended to imply that applied
chemistry has been or is entirely dependent upon pure
chemistry, for there are numerous instances where what
knowledge we possess in the speculative and real field of
the science has received its initial impulse from some use-
ful application.

INTRODUCTION xv

The progress of the science has often been with a halt-
ing step. Three important misconceptions — namely, the
immaterial nature of gases, the inverted notion of combus-
tion and the material nature of heat — had first to be re-
moved before the idea that matter is composed not only of
molecules but of atoms, could gain acceptance in the begin-
ning of the nineteenth century. By the atomic conception of
Dalton (1803) different kinds of matter are dependent not
only upon different kinds of molecules, but different kinds
of atoms in molecules, and, furthermore, as later proved,
even the configuration of the atoms within the molecules.

Various energy demonstrations, as heat, electricity and
light, bring about various changes in these molecules to
produce different kinds of matter. We know carbon dioxide
and water, under conditions which obtain in the leaf of a
tree, under the influence of light combine with the elimina-
tion of oxygen and the production of sugar. The chemist
as an expert achievement can produce sugar in his labora-
tory, but so far he has little understanding of the chemical
action of light in the laboratory of the leaf. Altho photo-
chemistry promises soon to yield results which may not be
devoid of startling interest, we do not know how nature
does many things that we are accustomed to see around us
and attribute to a so-called vital force. In exercising the
utmost care to avoid confusing the accomplished with the
projected, the thesis may be reverently supported that life
is energy or a manifestation thereof.

One were devoid of judgment did he not let it be clearly;
understood that he appreciates the objections, such as re-
tention of form through years, reproduction of species and
atavistic inheritance of character, that may be raised with

xvi INTRODUCTION

reason in opposition to the mechanical, physical, chemical
or energy explanation of life. As yet we do not know the
constitution of the highly complicated structures of the
carbon, hydrogen, oxygen, nitrogen and sulphur com-
pounds of the nucleus — "chemical matter," as Neur leister
says. The same could have been truly said of the sugars
before Fischer's masterly work, beginning about a genera-
tion ago, or Osborne's more recent work upon the nucleins
of wheat. Can we say, having learned the structure and
synthetized the nucleus, that we shall not be able in the
laboratory to give it that impulse which launches it upon
a career of reproduction?

Our militant egoism need not be shocked by apparently

Nourishing a youth sublime
With the fairy tales of science.

We thought we knew the air, but within the last two
decades it has been learned that the atmosphere contains
i per cent, of an element never dreamed of — namely, argon.
We thought every chemical atom was characterized by a
distinct ability to combine with other atoms to form com-
pounds. Argon and four other similar elements, including
helium, since found, are devoid of this characteristic.

The nineteenth century gave us Crookes' tubes, which
made the discovery of Rontgen rays possible and gave the
hint that established the existence of the Becquerel rays,
the pursuit of which eventuated in the unmasking of
radium by the Curies. This remarkable substance carries
enormous charges of readily detectable energy and under
certain conditions changes into another element, helium
(Ramsay and Soddy). The transmutation of the elements
has been experimentally demonstrated. In such considera-
tions confusion of terms must be studiously avoided.
Philosophically, radium cannot be an element, because its
molecule breaks up into something other than an atom
of the same thing, yet it has a recognized place in the

INTRODUCTION xvii

table of elements. This latter fact is due to an agreement
among chemists to recognize a substance as an element
which, under proper conditions, exhibits a spectrum show-
ing characteristic lines possessed by no other element and
possesses a definite combining weight. Radium satisfies
these two requirements and Constitutes an exception to the
general proposition of consistency of atoms in an elemen-
tary molecule. If we retain the term element, and there is
no indication of its being discarded soon, its definition
must be broadened.

A philosophic idea has come forward at intervals ever
since the days when we have written records of men's
thoughts — namely, that there is, or was, one, the simplest
substance of which all matter is, or was, made. If that be
true — and perhaps it is — then we only require the knowl-
edge of how to change one element into another and the
necessary apparatus to make the idea an accomplished fact.
So far, however, we have observed only the disintegration
of the elements and we must yet build them up.

A knowledge of the cathode rays produced within a
Crookes tube gave J. J. Thomson and Rutherford experi-
mental data for the latest interpretations of the phenomena
of radio-activity and the most modern answer to the ques-
tion of "What is matter?"

Thirty years ago Crookes suggested the existence of an
ultra-gaseous state of matter, a protyle, of which all matter
is composed, and that its particle weighs about one-thou-
sandth that of a hydrogen atom, the lightest atom known.
Thomson, following an elaborate procedure, weighed these
particles and found that the value was between 800 and
1,000. As they bear electric charges, he designated them
electrons. Rutherford has shown that in the disintegration
of radium a gas, called emanation, is produced. This, in
turn, changes through several steps and continuously into
helium. The change consists in hurling particles, called
a-particles, at a terrific speed from the emanation. These
particles are atoms of helium plus an electron, which is lost

xviii INTRODUCTION

in time. By weighing before and after, the weight of the
electron is determined. These values coincide with those
obtained by Thomson. Etymologically, an atom means
something which cannot be divided. We have been ac-
customed to apply the term to that chemical individual
which has not yet been divided. As soon as it is shown to
be complex the particle ceases to be an atom. As language
changes there can be little objection, if it is done by com-
mon agreement so there may be no misunderstanding, to
applying the term electron to a real atom or the real indi-
visible particle, for undoubtedly the atom of Dalton is
complex.

Therefore, matter is composed of molecules. Molecules
are made up of atoms. Atoms consist of electrons. Elec-
trons are charges of electricity. But what is electricity?
Ostwald asserts that we are aware of matter only through
the evidences of energy. Matter is an assemblage of
energy systems ; there is no matter. All resolves itself into
the mechanics of energy. Heat, electricity and life are
elementary energy systems, having definite capacity and
intensity, and as chemical entities with their equivalents,
represent our atomic conceptions. But here we go into the
realm of metaphysics. Many of the secrets of nature have
been gained, laboriously wrought for, but rich rewards
await the coming generations who inherit a knowledge of
the extremities of our globe but must yet learn of its
interior.

Science may therefore be looked upon as a gem, beauti-
fully cut, with its many facets. We view the light from
one face, or more, with the play of colors most exquisite to
the eye and gratifying to the senses. Whence the light?
That is nature, the throbbing pulsation of which, controlled
by some All-great, hence All-wise, Providence, makes our
universe what it is, however little or much of it we may or
may not comprehend.

Charles Baskerville.

CHEMISTRY

CHAPTER I

DEVELOPMENT OF THE CHEMICAL CONCEPTION

To many intelligent and cultivated persons not specifi-
cally instructed in Chemistry, this word recalls confused
memories of colored liquids, glistening crystals, dazzling
flames, suffocating fumes, intolerable odors, startling ex-
plosions and a chaos of mystifying experiments, the inter-
est in which is proportional to the danger supposed to
attend their exhibition. Further reminiscences are of
many singular objects in wood, metal, glass and earthen-
ware; of retorts and condensers, furnaces and crucibles,
together with bottles innumerable rilled with solids, liquids
and gases. This whole bewildering paraphernalia, more-
over, is connected by glass tubes of eccentric curves, dis-
played in inextricable confusion and meaningless array.

Behind this chaos arise vague memories of a professor
or teacher discoursing learnedly in a polysyllabic jargon,
and attempting to explain the unusual phenomena in
words which seemed stranger than the experiments them-
selves. It is rarely forgotten, as H. C. Bolton suggests,
how potent was the fascination exerted upon the hearer, a
feeling of awe and mystery as tho the mind were approach-
ing the border of the supernatural, impressions that have
clung to chemistry ever since its entanglement with the
superstitions of alchemy, astrology and the "black art."

Men and women interested in modern thought who

2 CHEMISTRY

undertake to gain through chemical literature a knowledge
of what chemists are doing in and for the world encounter
a discouraging nomenclature which repels them by its
apparent intricacy and cumbrousness. Their opinion of
the terminology of an exact science is not enhanced when
they learn that "black lead" contains no lead, "copperas"
no copper, "mosaic gold" no gold, and "German silver"
no silver; that "carbolic acid" is not an acid, "oil of
vitriol" is not an oil; that some sugars and some kinds of
wax are alcohols; that "cream of tartar" has nothing in
common with cream, "milk of lime" with milk, "butter of
antimony" with butter, "sugar of lead" with sugar, nor
"liver of sulphur" with the animal organ from which it
was named.

Readers of chemical writings sometimes fail to appre-
ciate the advantages of styling borax "di-meta-borate of
sodium," or of calling common alcohol "methyl hydrate,"
and they ignore the euphony in such words as pentamethyl-
diamidothiodiphenylamindiiodomethylate (a substance bap-
tized by Dr. Albert Maasen).

Th se vrhose chemical education consisted in attend-
ance on a course of lectures illustrated by experiments
performed in their presence, interspersed with occasional
recitations from a prosaic text-book which taxed the
memory in true Chinese fashion, may be pardoned for
retaining very hazy impressions of the true character of
the science. On the other hand, many thinking and read-
ing persons recognize the magnitude of the scope and
operations of chemistry, and have some appreciation of its
benefits to mankind. It is not to be unexpected, however,
that the layman's conception of chemistry in the abstract —
the cold, exact, abstruse science — seems as far removed
from the realms of romance as the higher mathematics.
Yet mathematics and music are strangely correlated; and
so it is not to be wondered at that the chemist himself, the
enthusiastic master of mysteries, finds in his modern

THE CHEMICAL CONCEPTION 3

miracle making that proportion of romanticism necessary,
perhaps, to the mental well-being of the individual.

The widely varying ideas which have prevailed at dif-
ferent periods in the history of chemical science, with
regard to its nature and object, are significantly por-
trayed in the definitions of chemistry which have obtained
at these periods, and an examination of the following col-
lection of definitions will reveal a curious growth :

Old Proverb. "Alchimia est ars, cujus initium la-
borare, medium mentiri, finis mendicare." Alchemy
is an art, the beginning of which is to work, the
middle to lie, the end to beg (according to Bolton).

Suidas (a Greek lexicographer of the eleventh cen-
tury). "Chemistry, the artificial preparation of silver
and gold."

Paracelsus (1537 [?])• "Chemistry is the art of
resolving bodies."

Denis Lachaire (1540 [?]). "Chemistry (al-
chemy) is that part of natural philosophy which
teaches the preparation of metals on the earth by imi-
tating the operations of Nature in the earth as closely
as possible."

Van Helmont (1620 [?]). "Chemistry is the art
of analyzing bodies by fire."

A Chymical Dictionary, London, 1650. "Chimia is
the art of separating pure from impure and of making
essences."

Salmon (1672). "Chemistry is an art or a practical
science which teaches the methods of resolving com-
pound bodies into their natural principles, and by this
means rendering them most pure and most efficacious
as a medicine, either for curing diseases or for per-
fecting the imperfect metals." ("Bibliotheque des
Philosophes Chimiques," Paris, 1672.)

Lemery (1675). "Chemistry is the art which
teaches the methods of separating the different sub*

CHEMISTRY

stances contained in a compound." ("Cours de
Chymie," Paris, 1675.)

Boerhaave (1724). "Chemistry is an art whereby
sensible bodies contained in vessels (or at least ca-
pable of being contained therein and rendered sen-
sible) are so changed by means of certain instruments,
and especially fire, that their several powers and vir-
tues are thereby discovered with a view to the uses of
medicine, natural philosophy and other arts, and occa-
sion of life." ("Elementa Chemiae," 1724.)

Pernety (1758). "Common chemistry (chimie vul-
gaire) is the art of destroying the compounds which
Nature has made. Hermetic chemistry is the art of
assisting Nature to perfect them." ("Fables Egyp-
tiennes et Grecques," Paris, 1766.)

Pernety (1787). "Alchemy is a science and the art
of making a fermenting powder which serves as a
universal remedy for all the diseases of men, animals,
and plants.

"Dictionnaire Mytho-hermetique," Paris (1787).
"False alchemy cannot better be defined than the act
of making one's self miserable, both as regards for-
tune and health."

Nicholson (1795). "Chemistry as a science teaches
the methods of estimating and accounting for the
changes produced in bodies by motions of their parts
amongst each other which are too minute to affect the
senses individually; and as an art it consists in the
application of bodies to each other in such situations
as are best calculated to produce those changes."
("Dictionary of Chemistry," London, 1795.)

H. Davy (1802). "Chemistry is that part of nat-
ural philosophy which relates to those intimate actions
of bodies upon each other, by which their appearances
are altered and their individuality destroyed." ("Lec-
tures" in Collected Works, vol. ii, 1839.)

Thomson (1810). "The object of chemistry is to

THE CHEMICAL CONCEPTION 5

ascertain the ingredients of which bodies are com-
posed ; to examine the compounds formed by the com-
bination of those ingredients; and to investigate the
nature of the power which occasions these combina-
tions." ("System of Chemistry," 1819.)

Frankland (1866). "Chemistry is the science which
treats of the atomic composition of bodies and of those
changes in matter which result from an alteration in
the relative position of atoms." ("Lecture Notes for
Students," London, 1866.)

Rodwell (1873). "Chemistry is the science which
treats of the various kinds of matter, whether simple
or compound, their properties and the laws which
govern their combination with and separation from
each other." ("Birth of Chemistry," London, 1873.)

Roscoe (1873). "The science of chemistry has for
its aim the experimental examination of the properties
of the elements and their compounds, and the investi-
gation of the laws which regulate their combination
one with another."

Ostwald (1890). "Chemistry is the science which
treats of the different forms of matter, their proper-
ties, and the changes which they undergo."

Mendeleeff (1891). "Chemistry is concerned with
the study of the homogeneous substances or material
of which all the objects of the universe are made up,
with the transformations of these substances into each
other, and with the phenomena which accompany such
transformations."

Remsen (1892). "The science of chemistry has to
deal with everything connected with the deepest-
seated changes in composition which the different
forms of matter undergo."
At the present time, chemistry is usually defined as the
study of matter and the changes produced in it by the
action of chemical force or other forms of energy upon it.
It rests upon a secure basis of fact, and its first object

6 CHEMISTRY

consists in learning the constituents of which the material
world is composed, in reducing these constituents to their
simplest forms, and in building up new chemical compounds
from the latter. These problems, along with the task of
determining the laws governing the chemical combination
of matter, occupy the time and thought of the chemists
of the present day.

The Egyptians, Hebrews, Phoenicians and other ancients
acquired a certain indefinite knowledge of chemical proc-
esses in a purely accidental manner, which were applied
for the practical results obtainable, but no explanation of
these processes was deduced. Neither did the Greeks and
Romans make any attempts to collate facts then known or
to pursue the investigation of natural phenomena for the
attainment of a definite purpose, nor before the fourth
century of the present era were endeavors made to gain
an insight into chemical processes by experiment. Such a
lack of data did not prevent the peoples of antiquity from
speculating on the nature of matter, however, and their
views upon the ultimate constituents, or "elements," of the
organized world have given the first age of chemistry a
characterizing feature.

Altho there is no positive evidence that the Greeks and
Romans were acquainted with a belief in the production of
precious metals from base metals, yet the theory that one
element can be transformed into another was developed
from the ancient doctrines of the nature of the elements,
and at the beginning of the present era, primarily in Egypt,
attempts were made to transform the base metals into gold
and silver. The art of transmutation was termed 'chemia/
a word which is probably derived from the North Egyptian
name for Egypt (von Meyer). This term is mentioned by
Plutarch as the name of Egypt, but there is some diversity
among etymologists whether the present word 'chemistry'
is derived from this Egyptian word; the Arabic 'kerna/
meaning secreting; the Sanskrit 'kerna,' meaning gold; or
the Greek 'chymos,' meaning fluid.

THE CHEMICAL CONCEPTION 7

Alchemy, which is derived from the Arabic 'al-kimija,'
an agent for effecting transmutation, had for its object the
solution of the problem of transmutation, the attainment of
the so-called "philosopher's stone," by the aid of which
metals were to be transmuted and the life of man pro-
longed. This task characterized the Age of Alchemy, a
period extending for at least twelve centuries. This age
was one of magic and necromancy, but effected the exten-
sion of the knowledge of chemical facts.

The next period in the history of chemistry is known
as the Iatro-Chemical, or the period of medical mysticism.
This period extended from the first half of the sixteenth
century to the middle of the seventeenth century and was
characterized by the absorption of medicine by chemistry.
However, chemistry did not lose its alchemistic tendencies
and was not yet an independent branch of natural science.

After the Iatro-Chemical Period occurred a transition
period and chemistry became a science. This period is
known as the period of the Phlogiston Theory, owing to
the fact that the chemists at the end of the seventeenth
and during most of the eighteenth century attempted to
explain the phenomena of combustion by assuming the
existence of a hypothetical principle of combustibility,
'phlogiston.'

The early part of the most recent period in the history
of chemistry is characterized by the decline and fall of
the phlogiston theory and its replacement by the anti-
phlogistic chemistry of Lavoisier, which laid the founda-
tion of the new chemistry, a science which covers the era
of quantitative investigation. This era has had for its
guiding star the chemical atomic theory, and the immense
strides made in the science during the latest epoch are due
to the exact study of chemical composition and the close
investigation of physico-chemical relations.

CHAPTER II

THE CHEMICAL KNOWLEDGE OF THE ANCIENTS

In endeavoring to find traces of a science in the earliest
historic times, the mind must be free of the idea that the
ancient presentment will be similar to the modern form as
it is known to-day. The ancients possessed a knowledge
of isolated scientific facts and occasionally formulated
crude theories, but it is exaggeration to speak of syste-
matic science as existing among them. This was due to
the fact that they preferred to advance from the general to
the particular, instead of drawing general conclusions from
accurately observed facts, s'ince they were disinclined to-
ward experiment and over fond of speculation. The posi-
tion of the natural sciences in the early times, particularly
that of Chemistry, is sufficient to show the manner in
which errors were introduced and became firmly estab-
lished as a result of following the purely deductive method,
which Aristotle deemed the road that should lead to the
desired goal.

Venable very appropriately speaks of the birth of Chem-
istry in terms analogous to the development of the ovum,
which will lead through a series of metamorphoses up to
the perfected insect; and Rodwell compares the study of
the transformations occurring at various periods in the
development of Chemistry with the study of the history of
a nation. Certainly there occurred the primary groping
after causes, struggles to frame laws, and revolutions ; and
it is informing to follow the progress of Chemistry much
as may be traced the history of a people's growth.

ANCIENT CHEMICAL KNOWLEDGE 9

The beginnings of Chemistry are lost in the haze of the
remote past and unquestionably date back thousands of
years to the time when the pressing needs of man taught
him to adapt to his own ends the means and materials
placed at his disposal. It is interesting to note that woman
was the first to receive instruction in chemical lore, ac-
cording to tradition and legend. In the apocryphal book
"Enoch," originally written about 1 15-120 B.C., an account
is given of the relations existing between angels and ter-
restrial folk, and it is stated that one of these angels,
Azazel, taught women the making of jewelry and the use
of rouge, as well as imparting not a little information con-
cerning the metals and precious stones of the earth. This
legend also is met with in writings of the third and fourth
centuries, and even in those times chemistry was held to
have been imparted to mankind in a remote past.

The question of the ultimate constituents of bodies or
the elements occupied the minds of the oldest nations, and
the primary conceptions of these elements occurred in the
mythical times before Empedocles and Aristotle. The
word element is derived from the Greek word 'elephas/
which was changed by circumstances to 'elebas,' 'elemas,'
and then to 'elementum,' the Latin equivalent.

In Babylonia it was believed that what was in the heav-
ens was also in the land and in all portions of it, and the
Babylonians considered that a relation existed between the
heavenly bodies and colors. They soon observed that cer-
tain relations existed between terrestrial phenomena and
the deportment of the heavenly bodies, and this observa-
tion led them to suppose that the first conceived elements —
fire, water, air and earth — were controlled by preternatural
powers. As might be expected from the similarity in their
efforts in accounting for the origin and formation of the
universe, the Egyptian conception of the elements was
similar to the Babylonian.

The oldest writings of India teach that the world was
made of wind, water, earth, fire, and a substance of imma-

io CHEMISTRY

terial nature, ether. In the Laws of Menu the subtle ether
is spoken of as being the first created, and from this, by
transmutation, came air, and this through some change
became light or fire, and by a further change in this came
water, from which lastly earth is deposited. This theory
was accepted by the Brahmans and Buddhists and found
its way into Europe. In the 'Anguttara Nikaja' conscious-
ness is named as a sixth element, and in the writings of
Kapila, the leading exponent of the Samkhya philosophy, it
is stated that there are five subtle particles, rudiments or
atoms — perceptible to beings of a superior order but un-
apprehended by the grosser senses of mankind — derived
from the conscious principle and themselves productive of
the five grosser elements, earth, water, fire, air and space.
Kanada, who founded the Nyaya system of philosophy,
proposed an atomic theory in which he states that atoms
are eternal and that the ultimate atom is simple.

One of the oldest of the Chinese classics, the 'Shu King/
contains a document of still greater antiquity termed "The
Great Plan with Its Nine Divisions," the first division of
which speaks of water, fire, wood, metal and earth as the
elementary substances which went to build up the uni-
verse. This document probably depicts a belief five thou-
sand years old and it is known that the above mentioned
substances were regarded as elements in the dynasty of
Hoang-Ti (2698-2599 B.C.). In that most obscure Chinese
classic, the 'Yi King,' fire and water, wind and thunder,
the ocean and the mountains, appear to be recognised as
the elements.

The most complete theories of the ultimate constituents
of bodies have come down from the Greeks, although it is
highly probable that the Greek philosophers did not them-
selves deduce their theories of atoms and elements, but
derived them from other sources. Some have maintained
that the Pythagorean theories are derived from the phi-
losophy of the Chinese; but, since the Greeks came from
Asia as did the other Indo-Germanic races, it is natural to

ANCIENT CHEMICAL KNOWLEDGE n

suppose that they brought various Eastern theories with
them, modified them according to their environment and
developed them by their own powers.

The earliest Greek cosmogonists were those of the Ionic
school, which was founded by Thales of Miletus, who lived
about 600 B.C. Thales considered that water was the ma-
terial cause of all things, and was ignorant of the atmos-
phere or air. Such views, as well as those of Anaximenes
and Heraclitus (in the sixth century B.C.), who ascribed
to air and fire respectively the role of ground material,
have had no influence upon the development of chemical
knowledge.

Leucippus, who lived in the fifth century B.C. and who is
regarded as the founder of the Atomistic school, consid-
ered that all things consisted of spaces and atoms, the
latter being further indivisible, having only quantitative
differences between one another and being always in
motion. This theory was further developed by Democritus
of Abdera, who took a primal element as the basis of his
speculations, but subdivided this further in that he imag-
ined it to be made up of atoms, which differed from one
another in form and size, but not in the nature of their
substance. According to him, all the changes in the world
consisted in the separation and recombination of these
atoms.

Empedocles of Agrigent (500 B.C.) regarded the 'ele-
ments' air, water, earth and fire as the basis of the world,
and maintained the constancy of matter. He did not speak
of the derivation of the elements from a single substratum
or of ultimate atoms, and in his system the contending
forces cause the combination and separation of the ele-
ments.

The system of natural philosophy of Plato (427-344 B.C.)
has been practically without influence on the development
of physical science. Plato assumed the existence of the
four elements of Empedocles and propounded mathematical
doctrines concerning these elements, but disregarded cer-

12 CHEMISTRY

tain difficulties pointed out by subsequent philosophers.
His pupil, Aristotle (384-322 B.C.), however, among the
most famous of the Greek philosophers, is deemed the

Fig. 1 — Democritus of Abdera (450 b.c), Who Taught an
Atomic Theory.

sr.ge who exercized the most influence upon subsequent
thought. Aristotle considered that four elements were in-
sufficient in themselves to explain the phenomena of
Nature; he therefore assumed a fifth one, which he imag-

ANCIENT CHEMICAL KNOWLEDGE

13

ined to have an ethereal nature and to permeate the uni-
verse.

The followers of the Aristotelian doctrine in the Middle
Ages supposed this 'element' to be material, the 'quinta
essentia/ and made many endeavors to isolate it, causing
endless confusion. The Stagirite considered the properties
of bodies to be the result of the simultaneous occurrence
and intermingling of fundamental conditions, and regarded

■Aristotle and His Students.

the component elements only in the sense of bearers of
these fundamental properties. He held that the chief
qualities of the elements were those apparent to the touch,
as warm, cold, dry and moist, and maintained that each
of the elements of Empedocles is characterized by the pos-
session of two of these fundamental properties, air being
warm and moist, water moist and cold, earth cold and dry,
and fire dry and warm. He concluded, therefore, that the
differences in the material world were to be attributed to

14 CHEMISTRY

the properties inherent in matter and that the elements can
change one into another.

In Aristotle's opinion, the transmutation of the elements
happens owing to the abstraction of certain qualities and
the substitution of others ; hence, he concluded that an ele-
ment can more readily change into one with which it has
one quality in common, as cold water to cold earth and hot
fire to hot air, than into one completely its opposite, as hot,
dry fire to cold, wet water. Aristotle regarded the change
of water into steam as a transmutation of the elements, a
qualitative change of material, as otherwise he could not
explain the great change of bulk if the steam had pre-
viously existed in the water without change or difference.
Views of this nature on the states of the aggregation of
matter led to the idea of transforming one kind of matter
into another, and the generalization of the Aristotelian
ideas fostered the belief in the possibility of the transmuta-
tion of metals, a particular feature of the alchemistic
period.

It is unnecessary to point out how widely the above men-
tioned views with regard to the elements deviate from the
conceptions of modern chemistry, yet the Greek philoso-
phers, with the freedom and boldness of the Hellenic mind,
and an ability to infer and enunciate, had grasped the idea
of elemental substances, elements out of which all things
were made — the principles of things — and had thought out
the existence of atoms as the ultimate constituents of mat-
ter. The belief in the existence of the Hindu and Aristote-
lian element ether was and still is assumed as a necessity
for explaining many phenomena. Various chemical facts
had been learned by empirical methods and by acci-
dent, but the Greeks overvalued the deductive and under-
valued the inductive method, and held aloof from the ob-
servation and practice of chemical processes.

In the earliest records of the Egyptians, Jews and Hin-
dus there is to be found an acquaintance with the working
of different metals, which art was held by the younger of

ANCIENT CHEMICAL KNOWLEDGE 15

those nations to have been taught by mythical personages.
On reference to the drawings found on the tombs in
Egypt, figures are shown therein illustrating the art of
metallurgy, and it has been learned that the operations
were conducted by weighed portions of matter. Moreover,
Biblical history records that the Jews were acquainted with
gold, silver, copper, iron, and probably lead and tin, and
that a form of balance was used for weighing metal. The
Greeks and Romans were familiar with many metallurgical
processes, but made no attempts to explain the chemical
processes involved in the smelting of ores.

The ancients believed that the metals were produced by
the penetration of air into the vitals of the earth, and as-
sumed that the amount of metal increased as the mine
proceeded inward. This conception was based on the testi-
mony of Aristotle and was entertained for a long time.

Gold and silver were the metals earliest known and were
valued highly in the early times. The gold mines of Nubia
were worked by the Egyptians, and in the time of Rameses
II. these mines yielded gold to the value of $600,000,000
per annum. The Phoenicians obtained gold in Eastern
Africa and were the first to mine gold on the Island of
Thasos. The malleability of gold rendered it possible for
the ancients to gild objects by covering them with thin
sheets of the metal, and they later learned to produce a
layer of gold on objects by dissolving the metal in mercury
and heating the amalgam produced. The older nations
were acquainted with processes for freeing gold from ad-
mixtures, as there are extant records of purifying gold dust
by melting it with lead and salt for some time, a method
practiced at a very early period and referred to in various
parts of Scripture. Pliny describes the purification of gold
by means of mercury, and the process used in his time was
similar to the amalgamation process practiced at the pres-
ent day. In general it may be stated that the old and new
methods of obtaining gold differ in details not in principle.
L Silver was supplied to the ancients by the Phenicians,

i6

CHEMISTRY

who worked the Rio Tinto mines in Spain, the native sil-
ver mines of Laurium, and the mines in Armenia. Accord-
ing to Posidonius, silver was discovered in Spain by the
forests taking fire and melting some of the ore in which the
precious metal was imbedded. Strabo states that silver
was purified by fusion with lead, but it does not appear
that the separation of silver from gold was known before
the present era. Beckmann states that the ancients used
an alloy of gold and silver, afterward termed 'electrum/
because they were unacquainted with the art of separating
these metals, and it is known that an amalgam of gold and

Fig. 3 — Ancient., Gold Medal, Commemorating the Foundation
of Rome.

silver was regarded in ancient times as an individual metal,
being termed 'asm' by the Egyptians.

Copper has been known from the earliest times, and
some authorities consider that it was the next metal after
gold which man learned to extract and reduce. The pres-
ent state of archeological research does not suffice to locate
all the principal copper mines of the ancients nor to com-
pute the quantity of metal which they yielded, but it is
believed that both the Hindus and Chinese made coins of
this metal at a period which may be fixed approximately at
about three thousand years ago. Copper was one of .the
greatest articles of commerce with the Phenicians, who de-

ANCIENT CHEMICAL KNOWLEDGE 17

rived a large supply from the mines of Nubia, which at one
time supplied the whole of the western world. They com-
bined with it the tin obtained from the islands of Cyprus
and Britain to make the bronze of commerce, which was
early used for making weapons, ornaments and utensils ; and

Fig. 4 — Carthaginian Shield, Plated With Silver.

the ancient civilized nations were acquainted with bronze
before they had learned to prepare tin in a metallic state.
Palmer states that it is evident that the copper mines in
the neighborhood of Serabit el Khadim and Magharah, in
Egypt, were in full working order at the time of the
Exodus ; and Bauerman is authority for the statement that

18 CHEMISTRY

the period over which the working of the copper mines at
Wady Magharah extends, according to hieroglyphic evi-
dence, is from the third to the thirteenth Manethonian
dynasties. With regard to the smelting processes by which
the 'aes/ or copper, of the ancients was obtained, nothing
certain has as yet been ascertained.

The concurrent testimonies of Hindu, Assyrian, Baby-
lonian and Greek tradition, as well as its own etymology,
fix the discovery of iron — that is to say, the invention of
smelting iron ore and of manufacturing iron and steel, or
the escape of the invention from the temples — at a period
not earlier than the fifteenth century b.c. Among others,
Brahma, Krishna, Nin-Ies, Jason and Osiris were credited
with the invention of iron. Lepsius is authority, for the
statement that iron has been in use in Egypt for more than
five thousand years, and it is well known that the Egyp-
tians early learnt to temper iron, which they employed for
the manufacture of a variety of hard instruments.

Kirchmaier, a writer of the seventeenth century, haz-
arded the conjecture that Adam was the first to use iron
for economic purposes, to which opinion there are no satis-
factory objections based on evidence. The ancients pre-
pared iron from brown iron ore and magnetite in smelting
furnaces, but no particulars are vouchsafed as to the actual
process used. However, old Roman iron smelting furnaces
have recently been unearthed near Eisenberg in the Pfalz,
and the form of furnace used by the Egyptians may be
judged from various inscriptions.

Lead was used by the Romans for making water pipes,
writing tables and coins, and soldering with lead or with
an alloy of lead and tin was also well known. The Romans
worked the lead ore deposits of Britain, but little is known
with regard to the smelting processes used. Tin was pre-
pared quite pure in olden times and was used in the prep-
aration of two important alloys, solder and bronze. The
Phoenicians obtained tin either from India or Britain and
the Israelites procured some from the Midianites. Among

ANCIENT CHEMICAL KNOWLEDGE 19

the Romans lead and tin were distinguished from one an-
other as 'plumbum nigrum' and 'plumbum candidum/ 'Stan-
num,' the present Latin word for tin, signified an alloy of
tin and lead.

Brass, an alloy of zinc and copper, was first described by
Aristotle and was long regarded as copper which had been
colored yellow by fusing it with 'cadmia/ an ore of zinc
often mentioned in ancient writings as having been found
in Cyprus, but was not recognized as an alloy to a much
later date, and zinc as an individual metal was not known
to the ancients. The name 'cadmia' is said to have been
derived from Cadmus, who is reputed to have introduced
the making of brass at Thebes, but this is doubtless incor-
rect. 'Cadmia' was also used as a medicine as early as
300 B.C.

When the metal mercury, or quicksilver, was first dis-
covered is not known, but its preparation from cinnabar by
means of copper and vinegar is mentioned by Theophras-
tus (about 300 b.c.) and it was known at least as early as
Aristotle's time. Some writers consider that in the passage
in the Bible where Moses directs that all the metals taken
from the Amalekites should be made to pass through the
fire and afterward to be "purified by the water of separa-
tion," that this "water of separation" was mercury, but
this is not based on fact.

Dioscorides describes the production of mercury from
cinnabar and iron, and Pliny refers to the purification of
mercury by forcing it through leather. The ancients were
aware of the fact that mercury "attracts particles of gold
and unites with them," and Vitruvius describes the manner
of recovering gold from cloth in which it has been woven
by this means. The principal ore of mercury, cinnabar,
mercuric sulphide, would not fail to attract the attention of
the crudest folk by its brilliant red color, and there are
sufficient evidences to show that it was used as a pigment
or paint by the Romans, Ethiopians and Jews.

Glass, the transparent solid formed by the fusion of

20 CHEMISTRY

siliceous and alkaline matter, was known to the Pheni-
cians and constituted for a long time an important manu-
facture of that people, because of its ingredients — natron,
sand and fuel — abounding upon their coasts. The art of
making glass, however, originated in China and Egypt, and
its discovery in the last mentioned country was accidental,
soda having been addecl as a flux to sand containing gold
for the purpose of extracting the latter. Glass ornaments
have been discovered in Egyptian tombs which are as old
as the days of Moses, and Pliny and Strabo give accounts
of the famous glass works of Sidon and Alexandria. The
Greeks acquired the art of glass making in the fifth cen-
tury B.C., and the Romans used glass for windows, mirrors
and various other purposes. Rawlinson states that trans-
parent glass was brought into use, or at least the oldest
specimen found is, in the reign of Sargon II., 710 B.C.

The artificial coloring of glass by metallic oxides was
discovered at a very early date, and remains have been
found in ancient Egypt which indicate that methods for
producing enamels and artificial gems were known. An-
cient profane authors make mention of immense emeralds
which are considered now to have been made of glass, and
Pliny states that beryl, opal, sapphire, amethyst, etc., could
be imitated, but that these imitations were softer and
lighter than the real gems. The art of engraving on glass
was also known in ancient times and the ancient Assyrians
cut gems with great skill.

The art of pottery presents a more ancient and closer
alliance between art and utility than any other branch of
manufacture, and the date at which this art began to show
itself is lost in the darkness of remote antiquity. The old
Egyptians understood how to coat their earthen vessels
with colored enamel, and porcelain was discovered and
employed by the Chinese at an early date. The potter's
wheel is probably the most ancient mechanical appliance
which industrial art has invented.

The people of ancient times prepared soap by the action

ANCIENT CHEMICAL KNOWLEDGE 21

of alkalis on fats, and drew a distinction between soft and
hard soaps, according as potash or soda was used in the
manufacture. According to Pliny, the soap in Germany
and Gaul was prepared from animal fat and a water ex-
tract of plant ashes strengthened by adding lime.

The art of dyeing no doubt originated in that love of
distinction inherent in the human mind, inducing man, for
its gratification, to stain his dress or his skin with the
gaudy colors of the vegetable kingdom, and was practiced
very long before any views were entertained as to the
nature of the changes which occurred in the chemical proc-
esses involved. The Egyptians developed dyeing with some
degree of scientific precision, as they were acquainted with
the use of mordants, learning that alum imparted no color
itself but fixed certain dyes on cloth, and perfected the dye-
ing of purple.

Tyre made dyeing one of its principal occupations, and
it has been asserted that the invention of the celebrated
dye, Tyrian purple, was made in that city. The discovery
of this purple dye is said to have been made 1,500 years
before the Christian era, and Pliny states that the juice
for communicating it was obtained from two different
kinds of shell-fish. Kermes, indigo, madder, archil, saf-
flower, alkanet, henna, broom, galls, walnut, pomegranate
seeds, Egyptian acacia and litmus were used as coloring
matter in the ancient times. In Pliny's time, white lead,
cinnabar, vermilion, smalt, verdigris, hematite, soot and
indigo blue were used for painting, and ink was prepared
by mixing soot with gum. Galena (sulphide of lead) and
realgar and orpiment (sulphides of arsenic) were used for
pigments and medicines, notwithstanding the fact that
their poisonous action was known.

The Egyptians were the first to use chemical prepara-
tions for medicinal purposes. Verdigris, white lead, lith-
arge, alum, soda and niter were employed in making
medicaments, and lead plasters were made from litharge
and oil. Iron rust was a very old medicine; and Homer

22 CHEMISTRY

speaks of sulphur being burnt to expel the evil spirits from
a home. It was also used for purifying clothes, conserv-
ing wine and for destroying foul odors.

Among other substances whose application dates from a
very early period may be mentioned lime, which was burnt
and used in making mortar, and for causticizing soda for
soap making; soda and potash, which were used in wash-
ing, glass making and soap making; bitumen and asphalt,
which were employed for cements, torches and embalming;
and acetic acid in the form of crude wine vinegar, which
the ancients assumed as being present in all acid plant
juices and considered to be a powerful solvent. Among
the other organic compounds known at the beginning of
the Christian era and possibly before then, were sugar,
starch, petroleum, oil of turpentine, and various fatty and
ethereal oils. Sugar was obtained from the sugar cane,
starch from wheat, and the fatty oils (olive, almond and
castor oils) were pressed from seeds and fruits. Oil of
turpentine was prepared by distilling pine resin. The an-
cients were familiar with beer, wine and bread making, but
did not, with their disinclination toward observation, know
that alcohol and a gas different from air (carbonic acid)
are formed during such processes of fermentation.

CHAPTER III

THE EARLY ALCHEMISTS

The origin of alchemy undoubtedly is to be sought for
in remote antiquity, as mythical tradition reveals the
sources from which the belief in the transmutation of
metals was nourished, and the primary historical sources
are rare and obscure. However, it appears that alchemy
was pursued as a secret science, held in honor, among
the Egyptians, Chaldeans and other nations.

The almost universal tradition among alchemists is that
their art was first cultivated among the Egyptians; and
when it is recalled that ancient Egypt was a country where
the chemical art was widely practiced, it is not surprising
that the earliest records of alchemy are to be found there.
Clement of Alexandria states that the knowledge of the
art was confined to the priests, who were prohibited to
communicate it to any but the heir-apparent to the throne
and to such among the priestly caste as were virtuous and
wise; and Plutarch mentions that the strictest secrecy was
observed. It would seem that the art of alchemy was espe-
cially cultivated at Memphis, and Ptah-mer, the high priest
of Memphis, was so great an adept that he was said to be
familiar with all things.

The first dominant personality with which the origin of
alchemy is associated is that of Hermes Trismegistus, and
the alchemists acknowledge him as one of the earliest
masters, if not the originator of their creed and craft
This Hermes, some assert, is identical with Canaan, the
23

24 CHEMISTRY

son of Ham, and the name is synonymous with the old
Egyptian godhead Thoth, which, when endowed with the
serpent-staff as the symbol of wisdom, was compared by
the Grecians with their Hermes. Hermes Trismegistus
was said to be the author of twenty thousand or more
books, which probably indicates that, as the god of letters,
all books were dedicated to him, and in Roman Egypt
pillars were erected in his honor, upon which alchemistic
inscriptions were put in the form of hieroglyphics.

In the eleventh century the alchemist Hortulanus an-
nounced the Latin version of an essay which he ascribed
to Hermes. This came to be known as the "Smaragdine
Table," or "Tabula Smaragdina," and it is probably one of
the earliest of the Hermetic philosophical or alchemistic
writings. An English translation of this essay, made by
F. G. Weichmann in his "Chemistry, Its Evolution and
Achievements," is as follows:

"True it is without a lie, sure and most true ; what

is below is like that which is above. And what is

above is like that which is below, of one substance to

perform miracles.

"And as all things have come from one being, the

meditation of one, so all things have been generated

from this one thing by adoption.

"Its father is the sun, its mother is the moon. The

wind has carried it in its womb. Its nurse is the earth.

The father of every talisman of the whole world is

this. Its power is unimpaired when it is turned upon

the earth.

"Separate the earth from the fire, the subtile from

the material, gently, with great cleverness. It rises

from the earth to heaven and again descends upon

earth, and receives the force of those above and those

below.

"Thus thou wilt have the glory of the whole world.

All obscurity, therefore, will leave thee.

"This is of all strength the strong strength, because

THE EARLY ALCHEMISTS 25

it will subdue every subtile thing and penetrate every

solid.

"Thus has the world been created. Hence there

will be wonderful adoptions whose measure is this.
"Therefore I have been called Hermes Trismegistos,

possessing three parts of the philosophy of the whole

world.

"What I have said of the operation of the sun has

been fulfilled."
This essay is obscure enough to receive almost any in-
terpretation.

The Chaldeans, who were masters of occult sciences,
undertook the fusion of astrology and magic, and the belief
in the connection between the sun and planets and the
metals, which was assumed for a long period, was of Baby-
lonian origin. It was believed that the planets influenced
a growth of the metals, and the signs of the heavenly
bodies became the symbols of the metals ; in fact, the
metals were called by the names of the stars up to the end
of the eighteenth century. One writer of the fifth century
a.d. states that gold corresponds to the sun, silver to the
moon, lead to Saturn, tin to Mercury, iron to Mars, and
copper to Venus.

In the thirteenth century symbols were used freely to
denote some of the metals ; as, for example, gold, Sol, was
represented by a circle with a dot in its center; silver,
Luna, was depicted by a crescent ; and copper, Venus, was
denoted by the symbol used by Glauber at a later date.
Many of the alchemists saw in these symbols an indication
of the metals they represented. Thus the circle illustrated
perfection of the metallic condition, while the semi-circle
indicated only an approximation to this state. Some have
supposed that the symbol for copper, Venus, represented a
hand mirror, and this is highly probable.

The Jews, who were believers in magic, played an im-
portant part in the fusion of eastern and western doc-
trine at the time of the birth of Christianity, and some

26

CHEMISTRY

writings on alchemy have been ascribed to Jewish writers.
The later alchemists recorded various Biblical characters
as alchemists on the authority of the Bible, as Adam,
Tubal-Cain, Moses and his sister Miriam, and John; and
referred the origin of alchemy to the time before the flood.

□ IS E

Moon, Mercury Venus,

Silver. Quicksilver. Copper.

Sun,
Gold.

e a* s\

Mars,

Saturn,

Jupiter,

Irom

Lead.

Tin..

Fig. 5

— Alchemical Symbols.

(Glauber.)

Democritus (460-357 b.c.) is the earliest historical per-
sonage connected with alchemy, but it is not known how
much of the alchemical knowledge of the ancients should
be assigned to him. His name is found in the magic ritual
of the Leyden papyrus (found in Thebes in the third cen-
tury a.d.), and, according to Pliny, he received instruction
in magic from Ostanes the Mede.

During the first centuries of the present era, the trans-
mutation of copper into gold was thought to be an ascer-
tained fact, and the works of Pliny, Dioscorides, Zosimus,
Aeneas Gazaeos and Themistos Euphrades furnish records

THE EARLY ALCHEMISTS 27

of this belief, which probably originated in the production
of alloys possessing the color of gold or silver. Kopp
has pointed out that it is probable in early times a plating
of gold or silver may have been considered an actual
transmutation of the covered object.

In the early part of the Christian era, alchemy attained
much notoriety and was fostered by the Church. In fact,
the records of alchemy go on increasing from this era,
and the savants of the time have left us fragments of their
works. First among the alchemists of the early part of
the Christian era is Zosimus, who lived in the third cen-
tury. In his "Manipulations/' comprising twenty-eight
books, he speaks of the fixation of mercury, of a univer-
sal medicine, and of a tincture which possessed the prop-
erty of converting silver into gold. Zosimus is spoken of
with great esteem by the later alchemists, and his mystical
language exercised a pronounced influence on the Alexan-
drians and medieval alchemists. Synesius, Bishop of
Ptolemais, wrote commentaries on the works of Zosimus;
he lived in the fourth century.

Olympiodorus, a native of Thebes, reproduced the phi-
losophy of Thales and Anaximenes, and was the first to
distinguish matter according to its combustibility. His
works, however, do not contain any certain information
with regard to definite operations.

Until the fourth century Alexandria had been the center
of science and philosophy, but under Roman rule it gradu-
ally declined, so that at this time only the Temple of Sera-
pis was left. This temple, which was the bulwark of
medical and alchemical study, however, was destroyed in
the reign of Theodosius, so that many books which would
have been invaluable for the history of chemistry were
lost through its destruction. The Serapeum of Memphis and
the Temple of Ptah also were destroyed at the same time
as the Temple of Serapis, and it is only due to the rela-
tions which before then were developed between the Egyp-
tians and the Byzantine Empire that all acquaintance with

28 CHEMISTRY

chemistry was not obliterated. Notwithstanding these
catastrophes, the knowledge of some chemical operations
continued to exist in Egypt, even tho the light of science
was gone and adepts no longer taught their cult, and the
conviction that the base metals could be transmuted into
gold and silver, with its alluring possibilities, still remained
a feature of Egyptian thought.

At the period when ignorance and barbarism prevailed
through every part of the Roman Empire, Greek learning
found an asylum among the Saracens. About the middle
of the eighth century the second prince of the Abbassidean
dynasty, the caliph Al-Mansur, founded the city of Bagdad
and the light of philosophy dawned upon Arabia. Al-
Mansur studied astronomy under the direction of two
Christian physicians at his court, and offered liberal re-
wards to those who would undertake the translation of
the Greek works on philosophy and science, which work
was executed by the Christians then resident in Bagdad.
He also founded a university at Bagdad, and pupils and
professors flocked to it from all parts. Greece, Persia and
India were taxed to help the Arab mind, India especially
providing many alchemical notions.

The succeeding caliphs, Harun al Raschid and Al-
Mamun, also were liberal patrons of learning of every
kind, and under the caliphate of the latter the light of
philosophy shone forth in meridian splendor. Science con-
tinued to enjoy the protection of the Saracen princes even
after the empire was divided into several caliphates, and
was, by means of their conquests, disseminated throughout
the greater part of the world. From the beginning of the
ninth to the end of the thirteenth century, when the power
of the Saracens yielded to that of the Turks, schools of
learning flourished in the empire, and the college at Bag-
dad contained 6,000 masters and scholars at the beginning
of the twelfth century.

About the year 1000, twenty schools were instituted at
Cairo and learning was imparted to a multitude of pupils.

THE EARLY ALCHEMISTS 29

Academies were also founded in Africa and Spain, and
these were distinguished by eminent philosophers when
barbarism universally prevailed among the western Chris-
tians. The library of the University of Cordova contained
280,000 volumes, and it is said that this university pro-
duced 150 authors.

Altho Islamism prohibited magic and all arts of divi-
nation, alchemy applied to the preparation of medicines
was ardently studied and it found its way to the other
Western nations, where from the Arabian universities in
Spain it attained its full development in the thirteenth
century.

The first of the "alchemical adepts" who appeared dur-
ing the Christian era was the so-called founder of experi-
mental chemistry, Abou Moussah Djafar al Soft, afterward
known to Western nations by the name of Geber. This
alchemist is supposed to have lived in the eighth century,
but his life is involved in hopeless obscurity and he has
sometimes been confused with Dschabir of Tharsis. How-
ever, some historians of chemistry have ranked him first
among the chemists and alchemists who flourished prior
to the time of van Helmont, and it has been remarked that
"Geber is to the history of chemistry what Hippocrates
is to the history of medicine."

No less than 500 treatises have been attributed to Geber,
and these are supposed to have included all the physical
sciences ; but the recent researches of Berthelot and others
have proved that the Latin writings hitherto ascribed to
Geber could not have been written by him. The oldest of
these writings, the "Summae Perfectionis magisterii in
sua natura Libri IV," was not written till the middle of
the fourteenth century, and it appears that the "De In-
vestigatione perfectionis Metallorum," which was formerly
thought to contain two important literary productions of
Geber — his testament and a tract on the construction of
furnaces — belongs to an even later date.

Berthelot further has shown that the Arabic manu-

30 CHEMISTRY

scripts of the authentic Geber prove that he did not really
profess the remarkable knowledge attributed to him, but
that he adhered to the Greco-Alexandrian alchemists. His
real views were mystical. For instance, he believed in the
influence of the planets upon the metals, and his reasoning
was mostly from premises which now appear defective.
The Latin treatises, with which, until the investigations of
Berthelot, the name of Geber has been connected, contain
views on sulphur and arsenic, and on the transmutation of
metals; in fact, they would make it seem that the object
of his work had been the discovery of the Philosopher's
Stone, but it is now known that these writings contain the
collected knowledge of the four or five centuries after the
time of Geber.

Rhazes, whose true name was Mohammed-Ebn-Sechar-
jah Aboubekr Arrasi, was a celebrated disciple of Geber.
He was born about the year 850, and no less than 226
treatises are said to have been written by him. These
writings discuss the influence of the stars on the formation
of metallic substances beneath the earth, and contain, some
assert, the first mention of borax, orpiment, realgar, and
certain combinations of sulphur, iron and copper, as well
as some salts of mercury and compounds of arsenic (Fi-
guier). He believed in the transmutation of metals and
undertook to perform a transmutation before Emir Al-
mansour, Prince of Khorassan, after the latter had spared
no e::pense in providing the necessary apparatus and
materials for the accomplishment of the "magnum opus."
He failed miserably, however, and subsequently died in
poverty and obscurity.

The next great Arabian scientist was the illustrious
Ebn Sina, generally called Avicenna, who was born about
980. He is believed to have died in the year 1036, altho
several Oriental peoples assert that he is still alive and
enjoying the nectar of perpetual life and untold wealth,
results of the surcharged power of the Philosopher's Stone.
Six or seven treatises on alchemy have been ascribed to

THE EARLY ALCHEMISTS 31

Avicenna. One of these, the "Tractatulus Alchimise,"
treats of the nature of mercury, which Avicenna regarded
as the universal vivific spirit, capable of penetrating, de-
veloping and fermenting. Avicenna undoubtedly derived
his chemical knowledge from Geber. According to Waite,
he describes several varieties of saltpeter and treats of
the properties of common salt, sulphur, orpiment, vitriol
and sal-ammoniac.

Among the other disciples of Geber may be mentioned
the Arabian physicians Avenzoar, Averrhoes, Maslema
and Abukases, and the philosopher Alfarabi. Avenzoar,
who lived in the eleventh century, is said to have made
some additions to the knowledge of medicinal preparations,
while Averrhoes, a physician celebrated for his personal
virtues, attempted to improve the theory of medicine by the
aid of philosophy and attained some prominence as a
chemist. A North Persian physician, Abu Mansur, wrote
a work on the principles of pharmacology, by which may
be ascertained the chemical knowledge of the time, but it
appears that the Arabian alchemists of the eleventh,
twelfth and thirteenth centuries mostly devoted themselves
to attempts at transmuting the base metals into gold.
These alchemists, in the main, were of little prominence
and contributed nothing new.

At the beginning of the seventh century almost the
whole Western world was overwhelmed with intellectual
darkness, and in the eighth century philosophy and learn-
ing seemed ready to expire among the Greek Christians.
However, the spirit of barbarism which possessed many of
the reigning emperors was not characteristic of the reigns
of Michael, Bardas and Constantine Porphyrogenetes, all
of whom, excited by the example of the Saracen caliphs,
recalled and encouraged learning. Constantine was him-
self, in the ninth century, the pupil of the Byzantine
scholar Michael Psellus, who contributed to the propaga-
tion of alchemistic ideas.

From the eleventh to the fifteenth century philosophy and

32

CHEMISTRY

learning were much neglected in the Greek empire, but
at the time when Constantinople was taken (1451) there
were several learned philosophers among the Greek Chris-
tians. These were obliged to leave their monasteries, how-

Fig. 6

-The 'Great Secret,' Sulphur and Mercury Uniting
to Form the Philosopher's Stone.

ever, and this circumstance occasioned the return of Gre-
cian learning into Europe ; for after the Greek empire was
destroyed by the Turks, the friends of literature and sci-
ence fled into Italy, taking with them many of the Egypto-
Greek and Arabian alchemistic doctrines.

THE EARLY ALCHEMISTS 33

Notwithstanding the fact that the decadence of Saracen
power in Europe was rapid after the expulsion of the
Arabs from Spain, yet for some centuries the influence of
Arabic thought was great. The works of the Arabians
were translated and widely disseminated, and the modes of
their thought and work imitated. Then, too, the returned
crusaders aided in the spread of Eastern learning and
many industries were founded by them. They were par-
ticularly interested in alchemy, however, and as the nobles
were impoverished and desireft to replenish their treasu-
ries, attempts at transmuting the base metals into gold
became more than a craze — it became the cardinal point
toward which all chemical knowledge was directed.

Many Christian princes were imposed upon by pretend-
ing possessors of the Philosopher's Stone. It is especially
interesting to note that the first appearance of an alchemist
at a German court was about the year 1063, when a bap-
tized Jew announced to Adalbert von Bremen that he had
acquired in Greece the knowledge of transmuting copper
into gold.

It was during the thirteenth century that learned men
gave their attention to the study of alchemy, and conse-
quently the art reached a high degree of development.
These scholars considered that the transmutation of the
metals was a settled fact and maintained the existence of
the Philosopher's stone, and some of them — Albertus Mag-
nus, Thomas Aquinas, Roger Bacon, Arnold Villanovanus
and Raymundus Lullius — greatly influenced the develop-
ment of chemistry by their pursuit of alchemy in a scien-
tific spirit.

Albertus Magnus (1 193-1280) was a scholastic theolo-
gian, but his genius and curiosity did not allow him to pass
by the Hermetic science without giving it attention; in
fact, he was the first German chemist of prominence and
is ranked as a skilful practical chemist for the period in
which he flourished. He became a Dominican friar in
1221, and from this time he was an instructor in philoso-

34 CHEMISTRY

phy, grammar, alchemy and natural history at Cologne,
Paris, Hildesheim and Regensburg.

Michael Maier, a later writer on alchemy, states that
Albert acquired the secret of the Philosopher's Stone from
the disciples of St. Dominic and that he communicated it
in turn to Thomas Aquinas. Maier further declares that
for thirty years Albert employed his knowledge as an al-
chemist and astrologer to construct, from metals selected
under proper planetary influences, an automaton having
the power of speech. This was the curious Android, which
was said to reply to every question proposed to it and
which Thomas Aquinas destroyed under the impression
that it was a diabolical machine.

Albert is also said to have suddenly reproduced the
flowers and softness of spring in the midst of winter for
the entertainment of William II., King of the Romans,
when the latter dined in the monastic house at Cologne.
The views of Albert are in the main those of the Arabian
school, altho he added many new chemical facts. He men-
tions alum, caustic alkali, red lead, arsenic, green vitriol,
iron pyrites and liver of sulphur. He knew that arsenic
renders copper white and he was familiar with the method
of purifying the precious metals by lead. He found that
sulphur attacks all the metals then known except gold and
designated the cause of this combination by the term
"afnnitas."

In his "De Rebus Metallicis et Mineralibus," Albert
states that he tested some gold and silver, said to have been
manufactured by an alchemist, and which resisted seven
fusions, but that the pretended metal was reduced to a
scoria by an eighth fusion. He distinctly recognised the
possibility of transmutation, however, when the operations
were performed on the principles of nature; and consid-
ered that all metals are composed of an unctuous and
subtle humidity, incorporated with a subtle and perfect
matter — that is, the metals are all essentially identical
differing only in form. In one portion of his "De Al-

THE EARLY ALCHEMISTS 35

chymia," he asserts that gold is produced by the action of
pure sulphur on pure mercury, by the permanent action of
nature and after more or less time.

Thomas Aquinas (1225-1274), "the universal and the
angelic doctor," was a Dominican friar and disciple of
Albertus Magnus, and taught at Paris and Naples. Several
works on alchemy have been ascribed to him. In one of
these, the "Thesaurus Alchemiae," he states that "the aim
of the alchemist is to change imperfect metal into that
which is perfect," and, moreover, asserts that such a trans-
mutation is possible. The other works of this character
attributed to him are "Secreta Alchymise Magnalia" and
"De Esse et Essentia Mineralium." He wrote on the
manufacture of artificial gems and some of the terms still
in use by modern chemists occur in the supposititious writ-
ings of Aquinas, as, for example, the term "amalgam" for
alloys containing mercury.

Roger Bacon (1214-1294), "the wonderful doctor," was
born at Ilchester, in Somersetshire, England, and studied
at Oxford and Paris. It is said that he studied history,
learned the Oriental and Western languages, and gained a
knowledge of jurisprudence and medicine, subjects to
which little attention was given in his time; and, in order
to prosecute his studies without interruption, he assumed
the monastic life in the order of St. Francis. He employed
his time not in the controversies of the day, but in re-
searches into the properties of natural bodies, and by the
aid of mathematical training and experiment he acquired
a knowledge of mechanics, statics and optics. His success
in physics and in the construction of automata kindled a
spirit of envy among the monks of his fraternity, and this
led to the circulation of a report that he held converse with
evil spirits, causing him to be imprisoned for ten years. He
also knew how to use convex lenses for telescopic and mi-
croscopic purposes, and drew attention to the error which
occasioned the Gregorian reformation in the calendar.

Bacon was familiar with many processes in chemistry,

36 CHEMISTRY

and doubtless would have produced great discoveries in
this science had he not been drawn aside from the path of
true investigation by the philosophical "ignus fatuus"
which led the philosophers of this age to attempts at trans-
mutation. He believed in the Philosopher's Stone and his
views on the transmutation of metals may be illustrated by
the following quotation from his "Speculum Secretorum":
"To wish to transform one kind into the other, as
to make silver out of lead, or gold out of copper, is as
absurd as to pretend to create anything out of nothing.
The true alchemists never held such a pretence. What
is the real problem? The problem is, first, by means
of art, to remove from the rough, earthy mineral a
bright metallic substance, like lead, tin or copper.
But that is only the first step toward perfection; and
the chemist's work must not stop there, for, besides
that, he must look for some means of getting the other
metals, which are always present in the bowels of the
earth in an adulterated condition. For example, the
most perfect is gold, which one always finds in the
native state. Gold is perfect because in it Nature
finished her work. It is necessary, then, to imitate
Nature, but here a grave difficulty presents itself.
Nature does not count the cycles which she takes for
her work, to which the term of life of a man is but as
an hour. It is, then, important to find some means
which will permit one to do in a little time that which
Nature does in a very much longer time. It is this
means which the alchemists call, indifferently, the
elixir, the Philosopher's Stone, etc."
Bacon also stated that

"With the help of Aristotle's 'Secret of Secrets/
experimental science has manufactured not only gold
of twenty-four degrees, but of thirty, forty and on-
ward according to pleasure."
The application of the study of alchemy to the exten-
sion of life was another subject of study with Roger

THE EARLY ALCHEMISTS 37

Bacon, and he states that the operation by which the base
metals are purged from the corrupt elements which they

Fig. 7 — The Philosopher's Stone, Showing Its Twin Nature,
and Symbolizing All Its Powers Over Nature.

contain till they are exalted into gold and silver, is con-
sidered by every adept to be calculated to eliminate the

38 CHEMISTRY

corrupt particles of the human body, so that the life of
mortality may be extended for several centuries. The
chemical investigations of Bacon have proved valuable,
but the above mentioned alchemistic ideas seem incom-
prehensible to moderns when contrasted with his other
views and knowledge. Gunpowder-like mixtures were
within his knowledge, and, according to some, names
sulphur and saltpeter as two constituents, while the third
constituent he denominates under the anagram "luru
mone cap ubre." He probably derived this knowledge
from some Arabic source. The Arabs were acquainted
with gunpowder-like mixtures as early as 1280, and the
knowledge of the propelling force of such mixtures came
about between 1313 and 1325. Guttmann states that "the
so-called ancient records concerning the invention of gun-
powder should be approached with great caution," since
manuscripts of doubtful date and origin have been inade-
quately translated to serve various nations as proofs of
their claim to this invention.

Bacon found that saltpeter could be purified by solution
in water and crystallization; he subjected organic sub-
stances to dry distillation and observed that inflammable
vapors were produced; and he called attention to the fact
that air was necessary for the burning of a lamp. All
these facts, together with many others, Roger Bacon
learned by experiment, and he is to be regarded as the
intellectual originator of experimental research. His im-
portant works are as follows: "Opus Majus," "De Secre-
tis Operibus Artis et Naturae," "Radix Mundi," "Specu-
lum Secretorum," "Secretum Secretorum," "Breviarum
de Dono Dei" and "Alchimia Major."

The alchemistic tendencies of the thirteenth century are
distinctly reflected in the work of the two celebrated
adepts, Arnaldus Villanovanus (Arnold de Villanova) and
Raymundus Lullius, yet much uncertainty exists in regard
to the life of the latter and to the works ascribed to him.
Nevertheless both exercised no small influence on their

THE EARLY ALCHEMISTS 39

generation and they were held in high esteem on account
of their methods and labors. Arnaldus Villanovanus (1245-
1310), whose birthplace is uncertain, studied medicine at
Paris for twenty years, after which he traveled through
Italy, visiting the various universities. He subsequently
went to Spain and practised as a physician in Barcelona,
but learning that Peter d'Apono, a friend, had been seized
by the Inquisition, he withdrew to Sicily, where he wrote
his tracts on medicine under the patronage of Frederick
II., King of Naples and Sicily.

Arnaldus was, however, charged with magical practises,
and in 13 17 the Inquisition of Tarragona condemned his
books to be burned on account of the heretical sentiments
they expressed. He was an adherent of the Arabian
school, believing in the composite nature of the elements
and in the transmutation of the metals, and his skill in
Hermetic philosophy was recognised by his contempora-
ries, one of whom wrote, "In this time appeared Arnold de
Villeneuve, a great theologian, a skilful physician and
wise alchymist, who made gold, which he submitted to all
proofs."

Arnaldus believed that quicksilver was the medicine of
all the metals, that sulphur was the cause of their imper-
fections, and that the Philosopher's Stone existed in all
bodies. He was acquainted with oil of rosemary and oil
of turpentine, and conducted distillations in a glazed
earthen vessel with a glass top. He was probably the first
to point out the poisonous nature of decaying flesh. He
made external application of various mercurial compounds
and understood some of the properties of alcohol. His
knowledge of poisons was extensive. The principal works
of Arnaldus are "Rosarius philosophorum," "Flos florum,"
'"Antidotarium," "De Vinis" and "De Venenis."

Raymundus Lullius (1 235-131 5) was descended from
an old and noble Catalonian family, and led a varied
career. According to Waite, in his "Lives of the Alchy-
mistical Philosophers," he "united the saint and the man

40 CHEMISTRY

of science, the philosopher and the preacher, the apostle
and the itinerant lecturer, the dialectician and the martyr ;
in his youth he was a courtier and a man of pleasure; in
mature age he was an ascetic who had discovered the uni-
versal science through a special revelation from God ; after
his death he was denounced as a heretic and then narrowly
escaped beatification as a saint." He was probably ini-
tiated into the secrets of alchemy by Bacon and Arnaldus.

In all about 500 works have been ascribed to Raymun-
dus, but there is very great uncertainty whether he is iden-
tical with the grammarian and dialectician of the same
name, and, moreover, the errant life which he led could
have afforded him few opportunities for the investigations
involved in the search for the "magnum opus." Therefore
it is supposed that many of his writings are spurious, altho
three of his alchemical writings — the "Testamentum,"
"Codicillus seu Vademecum" and "Experimenta" — are re-
garded as genuine. His alchemistic doctrines are obscure
and mystical, and this led many to think that wonderful
facts were concealed in his treatises.

Raymundus attributed remarkable powers to the Phi-
losopher's Stone, for he was able to say, "If the sea were
of mercury, I would change it into gold." He also af-
firmed that health, long life and precious stones were to
be procured through its means. The alchemist styling him-
self Raymundus Lullius was acquainted with nitric acid
and used it to dissolve certain metals, and he prepared
"aqua regia" by adding sal-ammoniac or common salt to
nitric acid and was aware of its dissolving gold.
Gruelin, in his "Geschichte der Chemie," states that
Lullius was acquainted with spirit of wine and that he
prepared vegetable tinctures by its use; and alum from
Rocca, white and red mercurial precipitates, cupellated
silver, marcasite and oil of rosemary are mentioned in the
works on alchemy attributed to him.

Among the other alchemists of this period were Jean
de Meung, the monk Ferarius and Pope John XXII. The

Fig. 8 — Coins and Medals of Alchemical 'Gold.'

42 CHEMISTRY

latter is claimed as an adept by the alchemists, but his
orthodox biographers deny that he had any alchemistic
inclinations. At his death in 1334, he left in his coffers
eighteen million florins in gold and seven millions in
jewels, and alchemists attribute these treasures to his skill
in their science.

In the fourteenth and first half of the fifteenth centuries
many alchemists were supposed to be in possession of the
Philosopher's Stone. The prominent alchemists of this
period were Nicholas Flamel, Peter Bono, Johannes de
Rupecissa, Isaac of Holland and his son, Bernard Trevi-
san, John Fontaine, Sir George Ripley, Thomas Dalton
and Thomas Norton.

Owing to the fact that alchemy was encouraged at many
of the European courts at this time, many charlatans
sprang up, pretending to be able to make gold without
limit, and in some cases the frauds attempted were dis-
covered. Nevertheless alchemy was not suppressed and
it found especial protection at the court of Henry VI. of
England, notwithstanding the fact that in 1404, by an Act
of Parliament, it was forbidden to make gold or silver,
as the preceding monarchs had had to pay heavily for their
encouragement of the art. As early as 1344, Edward III.
had coins struck from gold said to have been made in the
Tower and later large quantities of counterfeit gold coins
were manufactured. The alchemist Le Cor seduced
Charles VII. of France into a similar experiment during
a war with England, which only resulted in increasing the
national debt. This counterfeiting caused much discredit
to be attached to alchemy and the result was that this was
extended to chemistry itself. However, the knowledge of
chemical compounds and operations was enriched during
this period by some valuable experimental observations,
and toward the beginning of the sixteenth century chemi-
cal knowledge was greatly extended.

CHAPTER IV

THE LATER ALCHEMISTS

Until lately the marked progress in chemical knowl-
edge which occurred toward the end of the fifteenth cen-
tury and at the beginning of the sixteenth century was
always associated with the name of Basilius Valentinus,
but the authenticity of the writings ascribed to him has
become more and more questioned, and they are evidently
spurious in parts. He seems to have been born at May-
ence about 1394 and to have been a monk of the Bene-
dictine order ; but, altho numerous works have been printed
in his name, no further particulars concerning his life
have descended to posterity. The important works which
appeared under his name are as follows: "Currus Tri-
umphalis Antimonii," "De Microcosmo deque Magno
Mundi Mysterio et Medicina Hominis," "Tractatus Chim-
ico-Philosophicus de Rebus Naturalibus et Praeterna-
turalibus metallorum et mineralium," "Practica, una cum
duodecim Clavibus et Appendice," "De magno Lapide
Antiquorum Sapientum" and "Testamentum ultimum." It
is impossible to extract from these works the knowledge
gained and possessed by the original author, but, as von
Meyer states, "there can hardly be any doubt that a large
number of facts were recorded by the writer who lived
about a hundred years before the books were published,
this being especially the case in the 'Triumphal Car of
Antimony,' in which we possess what for a time was a
marvelous description of an element and its compounds."
43

44 CHEMISTRY

In this work the extraction of antimony from the sul-
phide found in nature is described and the properties of an-
timony are in part mentioned. Antimony was used in puri-
fying gold and its compounds were applied medicinally.
It would appear that Basil Valentine was the first to pre-
pare hydrochloric acid by heating together copperas and
common salt ; and that he was acquainted with the rectifi-
cation of the distillate obtained from beer and wine by
means of potassium carbonate, the use of precipitation as
a method of experimenting, and the employment of the
spirit lamp in certain operations.

Judging from some passages in the works ascribed to
him, Basil Valentine made the first attempts at qualitative
analysis, for he proved that iron was present in certain
hard tins, gold in Hungarian silver, silver in Mansfield
copper and copper in Hungarian iron. The language used
in the works of Valentine is frequently obscured by mysti-
cal pictures and ideas, and, like others of his time, he
often found it impossible to express his alchemistic
thought in any language save that of far-fetched allegory.

The sixteenth century, a period of reformation, adven-
ture and discovery, is characterized by the Paracelsists,
who formed a transition from the alchemists of the Arabic
school to the iatro-chemists. The latter had other objects
of research than the alchemists, but as some of the Para-
celsists and Medical Mystics were "hermetic philoso-
phers," it is appropriate to refer to their alchemistic views
here.

Paracelsus, the "Luther of Medicine," the "seer of
Hohenheim," created a new school of alchemy. He con-
sidered that gold could be made by application of chemis-
try, but that the process is not to be compared with the
method of producing gold by an exercise of the occult
powers existing in the soul of man. On adopting this
view, the Paracelsists with alchemistic tendencies aban-
doned experimental investigation and sought within them-
selves the great secret of alchemy.

THE LATER ALCHEMISTS 45

Libavius, who criticized the mystical writings of the
Paracelsists, nevertheless fully believed in the transmuta-
tion of the metals, and even van Helmont, the most dis-
tinguished of the iatro-chemists, went so far as to testify
that he himself had effected the transmutation of mercury
into gold. In his work, "De Vita Eterna," according to
Waite, van Helmont makes the following declaration:
"I have seen and I have touched the Philosopher's
Stone more than once; the color of it was like saf-
fron in powder, but heavy and shining like pounded
glass. I had once given me the fourth part of a grain.
I call a grain that which takes six hundred to make
an ounce. I made projection therewith, wrapped in
paper, upon eight ounces of quicksilver, heated in a
crucible, and immediately all the quicksilver, having
made a little noise, stopped and congealed into a yel-
low mass. Having melted it in a strong fire, I found
within eleven grains of eight ounces of the most pure
gold, so that a grain of this powder would have trans-
muted into very good gold nineteen thousand one
hundred and fifty-six grains of quicksilver."
He states further that he performed a similar operation
in public many times, and consequently believed in the
certainty of the art, altho he did not possess the secret of
making the transmuting agent. Other chemists of the
sixteenth century, as Agricola and Sennert, were not
avowed alchemists, yet they did not oppose views respect-
ing the transmutation of metals. The last important iatro-
chemist, Tachenius, alone contended against the ennobling
of metals. His instructor in Leyden, Franz de la Boe,
accepted the belief of his times in regard to transmutation.
In the reign of James I. of England reports were circu-
lated that an artist, Butler, had performed several trans-
mutations in London by means of a red powder secured
from an Arabian alchemist, and later he is said to have
accomplished wonderful cures with a Hermetic medicine.

46 CHEMISTRY

Van Helmont attests these miracles, some of which he had
the opportunity of witnessing.

After chemistry had assumed its proper position as a
science in the Phlogistic Period and its study was neither
obscured by attempts at transmutation nor limited to the
preparation of medicines, many experimenters still re-
mained convinced of the possibility of converting indi-
vidual metals into one another. Altho alchemical work
was kept secret to a great extent and was looked down
upon, yet expressions of belief were far from being un-
common, even among such chemists as Robert Boyle,
Johann Kunckel, Homberg, George Stahl and Hermann
Boerhaave. In his old age, however, Stahl advised and
warned against the pursuit of alchemy, and Boerhaave,
after considerable experimental work, showed the falsity
of many of the views held by the alchemists.

For example, the alchemists asserted that quicksilver
could be fixed in a fireproof, metallic condition without the
addition of any other substance, but Boerhaave disproved
this by keeping quicksilver at a somewhat raised tempera-
ture in an open vessel for fifteen years without noting any
change, and when he heated the quicksilver at a higher
temperature in a closed vessel for six months no change
was observed. Ernst von Meyer states in his "History
of Chemistry" that "after his (Boerhaave's) time no
notable exponent of chemistry — which had now attained
to the rank of a science — spoke" in support of the al-
chemistic views, "but all the greater was the number of
cheats and swindlers who cultivated the lucrative field of
gold-making even during the eighteenth century. The
conviction of the impossibility of transmutation, which
was at that time establishing itself among scientific chem-
ists, made its way but slowly into outer circles. Credulity
and the hope of obtaining riches for nothing were the
means of leading many into very doubtful paths, even so
late as the end of the eighteenth century and the beginning
of the nineteenth. The final echoes of the alchemistic

THE LATER ALCHEMISTS 47

problem which had for so long a period of time held the
cultured of every nation in a state of tension and had even
blinded eminent scientific men only appear to have died
away during the last decades of the nineteenth century."

The statements of witnesses and conductors of alleged
transmutations are often impressive and convincing, and
such testimony is the strongest of the supposed evidence
in favor of gold making. Probably the most interesting
of such records is that contained in the "Golden Calf
(the World's Idol)" of John Frederick Helvetius, an emi-
nent Dutch physician, written in 1667. In this work, Hel-
vetius narrates the fact that he received from the "Artist
Elias" a piece of the Philosopher's Stone the latter had in
his possession, and that this piece — no larger than "a grain
of rape seed" — transmuted six drams of lead into the finest
gold. This gold was then taken to a silversmith, who first
mixed four parts of silver with one part of the gold, "then
he filed it, put aqua fortis to it, dissolved the silver, and
let the gold precipitate to the bottom; the solution being
poured off and the calx of gold washed with water, then
reduced and melted, it appeared excellent gold, and instead
of a loss in weight, we found the gold was increased, and
had transmuted a scruple of the silver into gold by its
abounding tincture." In the seventeenth century it ap-
peared impossible to doubt such testimony; and at that
time it was not known that the articles made from alche-
mistic gold were but worthless alloys, prepared for fraud-
ulent purposes.

Among the other hermetic philosophers and adepts of
the seventeenth and eighteenth centuries, may be men-
tioned: Jean d'Espagnet, author of a treatise on mystical
alchemy; Alexander Sethon, who suffered from exposure
of his "power"; Michael Sendivogius, who made gold by
projection in the presence of Emperor Rudolph II. at
Prague, and at Varsovia and Wurtemberg; Busardier, who
left a powder when he died, one grain of which was used
by Emperor Ferdinand III. for converting three pounds of

48 CHEMISTRY

mercury into gold; Eirenaeus Philalethes; Pierre Fabre;
John Obereit; Lascaris, who is recorded as having
changed mercury into gold and gold into silver ; and De-
lisle. Alchemistic efforts were especially encouraged dur-
ing this period at the courts of a large number of German
princes, many of whom were amateur alchemists them-
selves and who expended large sums of money in fostering
gold-making. The prints of trickery were, however,
finally exposed as frauds and rogues, and a dire punish-
ment was meted out to them, almost without exception.

It has been mentioned that the alchemistic ideas, with
the transmutation of metals as their leading tenet, origi-
nated in Egypt, where they were first fostered by the
initiates of the "Sacred Art"; and that the conversion of
the sacred art of Egypt into alchemy resulted through con-
tact with European thought and ecclesiastical mysticism.
The Egyptian priests taught the unity of nature and as-
serted that a fundamental similarity existed between heav-
enly and terrestrial things ; but alchemy, while its argument
rested on a supposed familiarity with Nature's methods,
and postulated an orderly and simple universe, applied
moral conceptions to material phenomena and pursued a
policy, rich in fantastic detail, dictated by fanciful concep-
tions.

The original and central aim of alchemy was the pro-
duction of a substance which was variously designated as
the "Philosopher's Stone," "the one thing," "the essence,"
"the great elixir," "the great magisterium," "the red tinc-
ture," "the stone of wisdom," "the heavenly balm," "the
divine water," "the virgin water," "the phcenix," "the
lion," "the old dragon," "the basilisk," and "the carbuncle
of the sun." This substance was supposed to have the
power of transmuting base metals into gold; but other
powers were attributed to it also, and the alchemist un-
doubtedly regarded it as "the soul of all things." After
the eighth century, the Philosopher's Stone was reputed

THE LATER ALCHEMISTS 49

to possess the power of curing all diseases and was styled
"the great panacea."

This belief in its powers came into existence gradually
owing to the Western alchemists attaching too literal an
interpretation to some of the Arabian descriptions of its
powers; for instance, Geber termed the base metals in-
valids which he would cure (transmute) by means of the
Philosopher's Stone. At a much later date (about 1600),
it was claimed that the Philosopher's Stone could trans-
form quartz into gems, change a thousand pearls into one
pearl of great beauty, and render glass malleable. It was
also said to possess the power of imparting moral culture
and redemption from sin.

The descriptions of the "one thing" differ widely and
the alchemists could describe it only in contraries. Some
spoke of it as a red powder, others stated that it possessed
a peach-blow color, and many affirmed that it was of a
gray appearance. Paracelsus described it as a very stable,
red substance, transparent as crystal, pliable as gum, and
yet as fragile as glass. When pulverized, it was said to
resemble saffron. Philalethes states, in his "Brief Guide
to the Celestial Ruby" :

"The Philosopher's Stone is a certain heavenly,
spiritual, penetrative, and fixed substance, which
brings all metals to the perfection of gold or silver,
according to the quality of the medicine, and that by
natural methods, which yet in their effects transcend
Nature. . . . Know, then, that it is called a stone,,
not because it is like a stone, but only because, by
virtue of its fixed nature, it resists the action of fire
as successfully as any stone. In species it is gold,
more pure than the purest; it is fixed and incombusti-
ble like a stone, but its appearance is that of a very
fine powder, impalpable to the touch, sweet to the
taste, fragrant to the smell, in potency a most penetra-
tive spirit, apparently dry and yet unctuous, and easily
capable of tinging a plate of metal."

5® CHEMISTRY

The processes given for preparing the "Great Magis-
terium" are also numerous and varied. The methods
whereby the agent is itself perfected, and the processes
wherein the agent effects the perfecting of the base and
imperfect things, were divided into ten or twelve "Gates,"
or stages, by the alchemists. The prime requisite was the
securing of the crude material to be employed. This was
called the "materia prima cruda," "terra virginea," etc.,
and altho it was thought to occur in very large amounts,
its identity was unknown and the procuring of this sub-
stance was considered to be the really difficult part of the
undertaking.

From the "materia prima cruda" was to be obtained the
"materia prima matura," a substance also known as the
"mercurius philosophorum," or "azoth," to which was then
to be added "auro philosophorum." This mixture was
then digested at a low heat for some time without the
presence of the air, in the "ovum philosophicum," to pro-
cure the "raven's head," or "caput corvi," a black substance
which, through long digestion, became transformed into
the "swan," a white body. The latter was then exposed to a
higher temperature to produce the Philosopher's Stone.
The various "Gates" were known as calcination, dissolu-
tion, conjunction, putrefaction, congelation, citation, sub-
limation, fermentation and exaltation.

The Alexandrians believed that the metals were alloys
of varying composition and, consequently, that the trans-
formation of one metal into another was possible, either by
means of the addition of other substances or the expulsion
of some present; and the Western alchemists regarded all
metals as compounds. For example, Arnaldus Villano-
vanus and Raymundus Lullius assumed mercury and
sulphur as their constituents, and the latter asserted that
every substance is composed of these two substances.
Under the term "mercurius," or mercury, the alchemists
saw the cause of metallic glance and malleability, while
the term "sulphur" was used to express the idea of trans-

THE LATER ALCHEMISTS 51

mutability and also combustibility; and the various metals
were regarded as compounds of these substances in differ-
ent proportions.

For instance, gold, the most perfect metal, which
Nature was thought to form slowly in the earth, was con-
sidered to be a compound of much mercury with only a
small amount of sulphur. Therefore, considering that all
other metals differed from gold only in the proportions in
which mercury and sulfur were present, the alchemists
sought for an agent whereby these proportions could be
changed and gold produced. Introspection preceding ob-
servation gave rise to the alchemistic views of the universe
and natural phenomena, and, to quote M. M. Pattison
Muir, "the change from alchemy to chemistry is an ad-
mirable example of the change from a theory formed by
looking inward, and then projected on to external facts,
to a theory formed by studying facts, and then thinking
about them."

Altho many of the theories of the alchemists were ridic-
ulous and much unimportant material was accumulated
by them, yet they untiringly pursued their quest, their
views were connected with their practice, and, as Muir
observes, "there was a constant action and reaction be-
tween their general scheme of things and many branches
of what we now call chemical manufactures." The result
of this was that some progress, worthy of account, was
made in the knowledge of applied chemistry during the
alchemistic period.

Metallurgy was not the least of these. Three new
metals — antimony, bismuth and zinc — were discovered in
the second half of the Age of Alchemy and the knowledge
of the properties of the metals already known was in-
creased; but few alterations were made in the methods of
extracting and purifying the metals. As might be ex-
pected, the greatest importance was attached to the treat-
ment of gold and silver ores; and quite accurate balances

52 CHEMISTRY

came to be used as a result of the attention given to the
yield of the noble metals. For a long time, gold was ob-
tained in a pure condition just as it was in earlier times —
that is, by the use of lead; but later it was ascertained
that it could be purified by fusion with stibnite (antimony
trisulfide), and in the time of Albertus Magnus it was
found that gold and silver could be separated by treatment
with nitric acid. Prior to this time, the cementation
process of the ancients was employed for effecting the
separation of the noble metals. Silver was extracted by
fusion with lead, a method in use in Pliny's time.

Mercury was obtained by roasting its ores in furnaces
and by distilling sublimate (mercuric chloride) mixed
with caustic lime; it was used in extracting the noble
metals, in gilding, and in alchemical research. Zinc and
bismuth are mentioned in alchemical literature, and it
would appear that zinc was used in the early medieval
times; however, these metals were not used technically.
Cobalt ore is also sometimes mentioned.

In the fifteenth century, copper was prepared by im-
mersing plates of iron in solutions of bluestone (copper
sulphate), but there are no important improvements to
record in the methods of extracting and preparing iron,
lead and tin. However, the various degrees of hardness
and softness of iron were known at an early period, and
the deportment of copper, iron, lead and tin when sub-
jected to heat and to the action of acids was studied
throughout the alchemistic period.

Ceramics advanced to no little degree. In ancient times
glass had been colored by adding various oxides of metals
to the fused mass, but in this age it was learned that the
colors could be burned in — a decidedly important dis-
covery. It was also found that the use of glazes contain-
ing lead and tin for earthenware vessels was advantageous
for certain purposes.

Dyeing became better understood. Several important
dyes were introduced during the alchemistic period. Or-

THE LATER ALCHEMISTS 53

chilla, which was known in ancient Rome, was brought
from the East about the thirteenth century, and cochineal
was introduced by the Arabians. Indigo also began to be
used during this period. Alum was employed almost en-
tirely as the mordant in dyeing.

Inorganic Compounds were more thoroughly studied.
Nitric and sulphuric acids were obtained at an early date.
The former was first prepared by the distillation of a mix-
ture of saltpeter, blueslone and alum, but later it was
found that it could be produced from saltpeter and
sulphuric acid; and sulphuric acid was prepared by dis-
tilling a mixture of iron vitriol and pebbles, and by burn-
ing sulphur, after the addition of saltpeter, under a hood
fitted with a side tube for the overflow of the acid pro-
duced. When sulphur is burned alone, a gas now known
as sulphur dioxide is produced, and it is known that the
water solution of this gas was often confounded with
sulphuric acid. Geber prepared sulphuric acid by heating
alum, but failed to study its properties other than finding
that it was a powerful solvent. At a much later date,
hydrochloric acid was prepared by heating common salt
and green vitriol. This acid, which was known as
"spiritus salis," was mixed with nitric acid to prepare
"aqua regia," a strong solvent which the alchemists
thought closely approximated to the "alkahest," or uni-
versal solvent.

The alchemists were acquainted with a large number of
salts, of which it was thought that solubility in water was
a general characteristic; hence, the term "sal" included a
large number of substances and was widely distorted. The
term "alkali" is first mentioned in the Latin writings
ascribed to Geber, but, according to von Meyer, "one
seldom meets in the alchemistic age with a strict distinc-
tion between potash and soda, or between their carbonates,
while, on the other hand, preparations of carbonate of
potash obtained in different ways were regarded as dis-
similar products. The distinction drawn by Abu Mansur

54 CHEMISTRY

between 'Natrun' — i.e., the soda found in Nature as a
mineral deposit — and 'Qualia,' the alkali from the ashes
of land plants, is, however, very noteworthy. These
names have perpetuated in the German words 'natron'
and 'kali.' " The solvent power of the lyes obtained from

Fig. 9 — Alchemist Preparing Sulphuric Acid.

the carbonates of potash and soda by the addition of lime,
was made use of by the alchemists.

Among the salts known to the alchemists were alum,
which was prepared from alum shale and widely used;
iron and copper vitriols; saltpeter, salmiac and carbonate
of ammonia. Saltpeter (potassium nitrate) was probably

THE LATER ALCHEMISTS S5

used in early times in the manufacture of fireworks; it
was known in various periods of this age as "sal petro-
sum," "sal nitri" and "nitrum." Salmiac, "sal ammoni-
acum," chloride of ammonia, was originally prepared from
dung, altho some of the naturally occurring product
of volcanic origin was used. Carbonate of ammonia was
prepared by the chemists of the thirteenth century and
was known to them as "spiritus urinae" ; later it was ob-
tained from salmiac and alkali carbonate.

Other inorganic compounds known to the alchemists
were nitrate of silver, chloride of silver, mercuric oxide,
mercuric chloride, basic mercuric sulphate, mercuric
nitrate, zinc oxide, zinc sulphate, antimony trichloride,
basic chloride of antimony, antimony trioxide, potassium
antimoniate, arsenious acid, peroxide of iron, oxide of
copper and the lead oxides. As before mentioned, the
alchemists knew that gold dissolved in "aqua regia" ; this
solution, "aurum potabile," was thought to possess won-
derful medicinal effects. They also knew that silver could
be precipitated from a silver nitrate solution by the use
of mercury or copper.

The preparation of antimony from the sulphide by
fusion with iron, is described in several of the works
ascribed to Basil Valentine. It is mentioned in these
works that antimony does not possess the properties of a
metal in full degree, and that it is a variety of lead. In
the fifteenth century, antimony was used in certain alloys,
and the compounds of it then known were used in medi-
cine. Arsenic was prepared in the thirteenth century by
the Western alchemists, who considered that it was a
"bastard metal." Arsenious acid was prepared as early as
the tenth century, by roasting realgar, and was called
"white arsenic." At a much later period, about the close
of the Medieval Age, it was observed that arsenious acid
occurs in the fumes from pyrites furnaces.

Mention has been made of some sulphur compounds,
the sulphides of mercury (cinnabar) and antimony (stib-

56 CHEMISTRY

nite) among others, which were found to be valuable
materials for the production of sulphur and other bodies.
These were grouped together as forming a particular
variety of compounds, under the name of "marcasitae"
(Albertus Magnus), zinc blende, galena (lead sulphide),
and iron and copper pyrites being included among them.
The peculiarity which these substances had in common,
that of giving off a product of such characteristic odor as
sulphurous acid, when roasted, may have formed the main
reason for assigning them to one group. It should be
remembered, however, that the production of several
metallic sulphides from their components had been ob-
served {e.g., the formation of cinnabar from quicksilver
and sulphur), and this may be supposed to have con-
tributed materially to a knowledge of their composition.
Realgar and orpiment were known to the Arabian physi-
cians.

The alchemists were fond of using the names of animals
as symbols of certain mineral substances, and of repre-
enting operations in the laboratory by what may be
called animal allegories. The "yellow lion" was the alchem-
ical symbol of yellow sulphides, the "red lion" was synony-
mous with cinnabar, and the "green lion" meant salts of
iron and of copper. Black sulphides were called "eagles,"
and sometimes "crows." When black sulphide of mercury
is strongly heated, a red sublimate is obtained, which has
the same composition as the black compound; if the tem-
perature is not kept very high, little of the red sulphide is
produced; the alchemists directed to urge the fire, "else
the black crows will go back to the nest."

Organic Compounds were also examined and their
properties recorded. Notwithstanding the fact that the
alchemists originally paid more attention to the properties
of mineral bodies rather than to those of organic bodies,
yet the study of the action of heat upon bodies when air is
excluded and improvements in methods of distillation,
led to the investigation, in a crude manner, of the products

THE LATER ALCHEMISTS 57

of distillation and eventually to the discovery of definite
organic compounds. Among the few organic preparations
known to the alchemists, spirit of wine takes a prominent
place. This compound was formerly designated by very
different names; for instance, Marcus Graecus (eighth
century) calls it "aqua ardens," the Latin translators of
Geber's works refer to it as "aqua vitae," and others men-
tion it as "aqua vitis," "mercurius vegetabilis," "spiritus
vivus" and "consolatio ultima corporus humani." The
term "spiritus vini" first occurs in the writings ascribed
to Basil Valentine, and the name "alcohol" was first used
by Libavius at the end of the sixteenth century.

The symbols used to denote the metals have been re-
ferred to; among other signs employed instead of writing
the names of substances, were the following:

* wZa7\ V "~ V

Sulphur. Vitriol. Fire. Air. Water. Water. Earth.

V*V)V3 ?AA

Aqua Aqua Aqua Day. Night. Amalgam. Alembic.
Fortis. Regia. Vitae.

Some Alchemical Symbols.

The Alexandrians employed two vessels in conducting a
distillation, one for evaporating the liquid and the other
for condensing the vapor, and this improvement resulted
in the simplification of the method of manufacturing spirit
of wine, and an extension of its importance in medicine
and alchemy. The preparation of concentrated spirit of
wine by repeated distillation and by rectification over dry
carbonate of potash was described by Raymundus Lullius,
who also examined the action of sulphuric acid upon spirit
of wine. Spirits were generally dehydrated by rectifying
at a low temperature, however, and in order to condense

58

CHEMISTRY

the vapors completely they were passed through long con-
densing tubes, often of an extraordinary form.

At the close of the Middle Ages, the alchemists were
acquainted with several ethers, which they prepared in
an impure state by the action of acids on spirit of wine.

Fig. io — Alchemical Still.
(a) — Copper still; (b) — Still head ; (c) — Cooling medium ; (i) —
Condensing tube; (<?) — Receiver.

One of the alchemical writers speaks of a spirit prepared
in this way which has a "subtle, penetrating, pleasant taste,
and an agreeable smell." This probably referred to ethyl
oxide, or ethyl ether, a compound prepared by various
chemists in the sixteenth and seventeenth centuries.

THE LATER ALCHEMISTS 59

It has been mentioned that the only acid with which
the ancients were acquainted was vinegar — that is, an

Fig. 11 — Improved Distilling Apparatus.
Frontispiece of Hieronymus Brunschwick's 'Liber de arte dis-
tillandi de compositis.'

impure wine vinegar. The alchemists, however, learned
to concentrate vinegar, and it is to them that is owed
the first production of acetic acid by distillation. The

60 CHEMISTRY

alchemical views concerning the formation of acetic acid
from alcohol are vague and it was frequently confounded
with the acids observed in plant juices.

The belief in the transmutability of metals was dis-
missed from chemistry when Lavoisier established the
important generalization of the new chemistry, namely,
that matter may be changed, but neither destroyed nor
created (1770). Nevertheless, many have applied them-
selves to attempts at converting the bountiful metals into
the agreed standard of exchange, but these experimenters
have been for the most part men of limited chemical knowl-
edge and experience, and, to quote Charles Baskerville, "a
careful analysis of the motives actuating and methods
pursued presents merely an inferior picture of the per-
fected practises we are gradually learning of as obtain-
ing in that circle termed 'high finance/ " The alchemical
literature of the nineteenth century is quite extensive, but
is, in general, cabalistic and teeming with credulity, mis-
conception, and misinformation.

At the present time, there is a strong inclination among
chemists toward a belief in the mutual convertibility of
chemically similar elements. This view is based on the
supposition that all the chemical elements are combinations
of different quantities of one primal element and on the
peculiar conduct of certain recently discovered elements;
in fact, the belief in the transmutation of atoms is in close
agreement with the present theories of atomic disintegra-
tion, but this is based upon new discoveries and on cor-
rectly interpreted chemical problems, and not upon false de-
duction and experiment. It is, therefore, not to be confused
with the earlier views, for even if the hypothetical primal
element should be isolated, one aim of alchemy would be
fulfilled, but the fulfilment would not be that whereof the
alchemystical philosophers taught and dreamed.

CHAPTER V

THE PERIOD OF MEDICAL MYSTICISM I THE IATRO-CHEMICAL
PERIOD

The sixteenth century, one of epoch-making discovery,
witnessed the differentiation of Chemistry from Alchemy.
Up to this time traditional belief had dominated every
branch of science and scientific inquiry had been pursued
almost solely in the cloister ; but now the great universities
of Oxford, Heidelberg, and others in France and Italy,
were beginning to make their influence felt, and the
sciences found a foothold in these institutions. Then, too,
these seats of learning favored the free exchange of
thought, and the introduction of the art of printing re-
sulted in the quick and wide dissemination of ideas. Con-
sequently, the capacity for reflection and criticism spread,
and the boundaries of human knowledge were enlarged.

A further aid to the development of the natural sciences
was supplied by certain modern eclectic philosophers who
perceived the defects and errors of ancient lore and phi-
losophy, and burst the enclosure of authority by attempting
innovations in philosophy. The inductive method was
found to be of especial value in combating and controvert-
ing medieval belief, and by its means the experimental
sciences came into existence.

It was believed that Chemistry should serve the interests

of Medicine, and, therefore, there was a strong tendency

toward a concatenation of the two. Medicine was, to a

certain extent, regarded as a division of Applied Chemis-

61

62 CHEMISTRY

try, and then it began to be viewed as the true end of
Chemistry. The chemist was to discover, prepare and in-
vestigate medicines — duties which resulted in the carrying
out of many careful researches and in the discovery of new
compounds, while the physician was to study their action
on the human economy. This fusion resulted in the birth
of Organic Chemistry ; and the application of men belong-
ing to a learned profession to the problems offered by
chemical phenomena, enriched both Medicine and Chem-
istry. This increase in knowledge gradually led to definite
ideas, and the latro-Chemical Period thus formed a period
of extension for Chemistry.

In the first half of the sixteenth century, a Suabian phy-
sician, Philippus Aureolus Paracelsus Theophrastus Bom-
bastus von Hohenheim, better known as Paracelsus, a name
which has always carried with it a mysterious suggestion
of power, liberated Chemistry from the yoke of Alchemy
and joined it with Medicine. He accomplished this dur-
ing a period of ecclesiastical and national reformation —
when Luther and Calvin were combating against super-
stition, when Copernicus was remodeling astronomy — and
the changes he wrought, through his originality of thought
and teaching, and freedom and vigor of expression, well
entitle him to the appellation some have seen fit to give him,
the "Luther of Medicine."

Paracelsus was born at Einsiedeln, Switzerland, on No-
vember ioth, 1493. His father was a physician, and Para-
celsus received his first instruction in medicine from him;
and at the age of sixteen he entered the University of
Basel, where he studied for a short time. So desirous was
he of penetrating into the mysteries of Nature, however,
that he neglected books and took prolonged journeys
through most of the known countries of the world, where
he had many romantic and hazardous experiences, but
nevertheless sought to glean every scrap of knowledge ob-
tainable from literary and learned men, mechanics, metal-
lurgical workers, occults, and every one with whom he

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12 — An Old Notice of Paracelsus.

64 CHEMISTRY

came in contact. He returned to Switzerland about 1525,
and was recommended by Oecolampadius to the chair of
physic at Basel. He commenced his career at this insti-
tution by publicly burning the works of Avicenna and
Galen, and at once began his fight against the old medical
school. He was forced to leave Basel, however, in 1527,
after a quarrel with the Municipal Council, and withdrew
into Alsace, whither his fame in medicine followed him.
About 1530, he returned to Switzerland, and from this
time he seems to have roved restlessly in Germany and
Austria, until at last, in the year 1541, he died in the hos-
pital of St. Sebastian, in Salzburg in the Tyrol. The char-
acter and ability of Paracelsus have been rated high by
some, and extolled and abused by others, even his disciples.

One writer says of him: "He lived like a pig, looked
like a drover, found his greatest enjoyment in the company
of the most dissolute and lowest rabble, and throughout
his glorious life he was generally drunk." It is true that
his life offered a strong contrast to his mentality, but he
was a man of noble character and intentions, a Christian
humanist and ambulatory theosophist, who hoped to in-
spire mankind with a love of conscientiousness and verac-
ity and to restore the suffering to health.

Paracelsus was active as a teacher, physician and writer,
and over a hundred books have been attributed to him.
These works cover many subjects — chemistry, medicine,
astrology, botany, etc. — but it has lately been shown that
much of the subject matter was not really his. The chemi-
cal knowledge and medical views of Paracelsus are best
seen in the following works : 'De Tinctura Physicorum,'
'Archidoxa/ 'Paragranum,' 'Paramirum/ 'De morbis ex
Tartaro Oriundis' and 'Grosse Wundarznei.' Two other
of his well known works are 'Das guldin Fliiss' and 'Tes-
tamentum Theophrasti Paracelsi.' An excellent collec-
tion of various editions of the works of Paracelsus, to-
gether with many commentaries and translations, is now

PERIOD OF MEDICAL MYSTICISM 65

preserved in the Homeopathic Medical College of Phila-
delphia.

Paracelsus taught that "the object of chemistry is not
to make gold, but to prepare medicines," and he considered
that the operations which occur in the human body are
chemical ones and that the state of health is dependent
upon the composition of the organs and the juices they
secrete. Medicine, Paracelsus asserted, rests upon four
pillars, chemistry, philosophy, astronomy, and virtue. Or-
ganic bodies were composed of mercury, sulphur and salt,
which corresponded to the physical "phenomena of vola-
tilization, combustibility and solidification," but which were
related in a higher sense to spirit, soul and body; and the
increase and decrease of these principles from their normal
amount caused illnesses.

For example, he states that an increase of mercury pro-
duces paralysis, that an increase of salt gives rise to diar-
rhea, and that gout results from the elimination of the
sulphur of the body. Paracelsus maintained that each dis-
ease must be antagonized by specific medicines ( "arcana"),
and that the preparation of these remedies was the aim
of chemistry. In inaugurating this method of combating
disease, he employed many chemical preparations, among
which were sugar of lead (lead acetate), corrosive subli-
mate (mercuric chloride), copper vitriol (copper sul-
phate), lapis infernalis (silver nitrate), and many anti-
mony compounds.

In addition, he was the first to use oil of vitriol sweet-
ened by spirit of wine, iron saffron and iron tinctures; and
introduced improved methods of preparing various es-
sences and extracts by means of spirit of wine. These ad-
ditions to the medical treasury instigated apothecaries and
physicians to engage in the study of chemistry; for the
preparation of new medicines required a certain familiarity
with chemical facts, and before the advent of Paracelsus,
the apothecary had been a mere herbalist and storekeeper.
It may be said, therefore, that pharmacy began here, and

66 CHEMISTRY

that pharmacy as a distinct profession and subject of study
was largely founded by Paracelsus.

There seems no doubt that Paracelsus discovered many
facts which became of importance in chemistry. He dis-
tinguished metals from substances which had been classed
with metals ; his criterion of a metal was ductility, and he
was therefore led to separate the metals from the half-
metals — a foundation for a classification of the metals
which lasted for many generations. He obtained the in-
flammable gas we now call hydrogen by the reaction be-
tween iron filings and sulphuric acid, tho it could not be
said to be a discovery in the sense of preparing and iden-
tifying the gas. The work he did upon the preparation
and application of various inorganic and organic com-
pounds, led to an extension of the knowledge of chemical
preparations.

The Paracelsists, who arose as a result of the labors of
Paracelsus, appear to have been largely mystics, but in-
cluded also physicians who were adherents to his school,
alchemists, and charlatans. These disciples engaged in
a violent contest with the ones faithful to the doctrines of
Galen, and during the sixteenth century the medical world
was in a state of agitation as a result of the controversies
and polemical writings which resulted. This contest was
decided, if not altogether in favor of Paracelsus, at least in
that of the iatro-chemists.

Many of the disciples of Paracelsus imitated the rough-
ness, the wandering life, and the charlatanism of their
master. These men, among whom was Thurneysser, re-
produced the ideas of Paracelsus, but were without his
mental gifts and wrought harm by the careless use of poi-
sonous preparations. Such acts induced legal action, and
in some places the prescription of poisonous preparations
was prohibited. Such was the case in Paris, for example,
where the parliament put a stop to the use of antimonial
preparations in medicine.

There were such prominent physicians and chemists,

PERIOD OF MEDICAL MYSTICISM 67

however, as Turquet de Mayerne, van Mynsicht, Croll and
Andreas Libau, who belonged to the school of Paracelsus,
but regarded his doctrines from a critical standpoint and
attempted to extract only the good they contained. In
these endeavors to separate true scientific facts and doc-
trines from a mysticism and seeming charlatanism mar-
ring the works of Paracelsus, they enriched both medi-
cine and chemistry. Turquet de Mayerne (1 573-1655)
possessed an excellent knowledge of chemistry for this
age, and endeavored to introduce the rational application
of chemical remedies. Oswald Croll was the first to
recommend the use of volatile salt of amber (succinic
acid) and of sulphate of potash in medicine; and Adrian
van Mynsicht brought tartar emetic into vogue.

Andreas Libau (Libavius) was born at Halle, and there
studied medicine and practiced as a physician. He also
acted as head of the "Latin School" at Rothenburg from
1 591 to 1607, and later became director of the gymnasium
at Coburg, where he died in 1616. Libavius had a wide
knowledge of chemistry and made many valuable chemi-
cal discoveries. From tin he obtained its tetrachloride,
by distilling it with sublimate; and to him belongs the
merit of simplifying the method of preparing sulphuric
acid, and of showing that the acid obtained in many ways
— from alum, sulphate of iron, or sulphur and nitric acid
— was the same substance (oil of vitriol). He also dis-
covered sulphate of ammonia, and investigated the ace-
tates of lead. He vigorously combated the defects in
the doctrines of Paracelsus, and did much to indicate the
meaningless nature and obscurity of the mystical and
sophistic writings of the Paracelsists.

Libavius wrote the first text-book on chemistry, which
put, clearly and in order, all the most important facts
and theories of the science at the date of publication
(1595) ; this work, which was published under the title
'Alchemia e dispersis passim optimorum auctorum
. . . collecta, adhibitisque ratione et experientia quanta

68 CHEMISTRY

potuit esse methodo accurata explicata et in integrum
corpus redacta,' was frequently reprinted and was held
in high esteem for a long time.. His other writings ap-
peared under the title, 'Opera Omnia Medico-chymica'
shortly before his death.

Libavius possessed a thoro general education and a
sound judgment, yet he believed in many of the tenets of
alchemy. This was mainly due, however, to the predilec-
tion of the period in which he lived, and did not prevent
Libavius from serving the interests of chemistry to good
purpose. It is important to mention that he made efforts
to establish large and well-fitted chemical laboratories.

Paracelsus and his followers had turned chemistry into
new Lines, and the finest talent was enlisted in the ranks
of the iatro-chemists, or medico-chemists, to whose work
Paracelsus had given such impetus. The most distin-
guished of these iatro-chemists was Johann Baptist van
Helmont, a celebrated physician, born at Brussels in 1577.
At an unusually early, age van Helmont applied himself
to the study of philosophy and theology, and, to quote
from an autobiographical fragment which he left
(Brande), "In 1594, being then seventeen years of age, I
finished my courses of philosophy, but upon seeing none
admitted to examinations at Louvain who were not in a
gown and hood, as tho the garment made the man, I was
struck with the mockery of taking degrees in arts.

"I therefore thought it more profitable, seriously and
conscientiously, to examine myself; and then I perceived
that I really knew nothing, or, at least, nothing that was
worth knowing. I had, in fact, merely to talk and to
wrangle, and therefore refused the title of Master of
Arts, finding that nothing was sound, nothing true, and
unwilling to be declared master of the seven arts, when
my conscience told me I knew not one. The Jesuits, who
then taught philosophy at Louvain, expounded to me the
disquisitions and secrets of magic, but these were empty

PERIOD OF MEDICAL MYSTICISM 69

and unprofitable conceits; and instead of grain, I reaped
stubble. In moral philosophy, when I expected to grasp
the quintessence of truth, the empty and swollen bubble
snapped in my hands.

"I then turned my thoughts to medicine, and having
seriously read Galen and Hippocrates, noted all that
seemed certain and incontrovertible; but was dismayed
upon revising my notes, when I found that the pains I
had bestowed, and the years I had spent, were altogether
fruitless; but I learned at least the emptiness of books
and formal discourses and promises of the schools. I
went abroad and there I found the same sluggishness in
study, the same blind obedience to the doctrines of their
forefathers, the same deep-rooted ignorance." He there-
fore concluded that medical knowledge was not to be ob-
tained from the writings of men or from human industry.

About this time he learned, from a chemist, the prac-
tical operations of the chemical art, and devoted himself
with great zeal and perseverance to this pursuit, in hopes
of finding in a chemical laboratory that knowledge which
he had in vain sought for from books. The medical skill,
which he by this means acquired, he employed in the ser-
vice of the poor, and, in addition, he enriched chemistry
by a great number of valuable observations. He died in
Brussels in 1644.

Van Helmont possessed ready talents, read much, and
by the aid of experiment, improved both chemistry and
medicine; but his vanity led him into empirical preten-
sions and he had an intense inclination toward the super-
natural— the result of his mystical studies and application
to theology, especially to the pious writings of Thomas-a-
Kempis and John Tauler. Thus did he who possessed
powers of observation and perception unapproached be-
fore his time by any other observer, give expression to
fantastic views upon the elements and vigorously defend
the transmutation of the base metals into gold. He
thought that wisdom is to be obtained only by humility

70 CHEMISTRY

and prayer, and believed that he had once seen his soul as
a brightly shining crystal.

He was convinced that dirty linen packed in a yessel
with flour would in time produce mice, and that a toad's
bones applied to an offending part was a certain anodyne.
He boasted that he possessed a fluid, the "alcahest," which
was capable of penetrating into bodies, producing an en-
tire separation and transmutation of their component
parts. No one, not even his son, saw this wonderful
fluid, and its possession was a secret van Helmont cau-
tiously guarded.

Van Helmont looked upon water as the chief constit-
uent of all matter, and brought forward many arguments
in support of his theory from the animal and vegetable
world. That water was present in organic bodies he con-
cluded from the fact of invariably procuring it as a prod-
uct of their combustion. He believed that he contrib-
uted a strong proof of this by the following experiment:
He took an earthen vessel of large dimensions, and filled
it with two hundred pounds of dry earth, in which he
planted a willow weighing five pounds. This was then
duly watered with rain and distilled water for five years,
at the end of which time he pulled up the willow and found
that it weighed one hundred and sixty-nine pounds and
three ounces. Moreover, the earth had decreased two
ounces in weight. He therefore concluded that one hun-
dred and sixty-four pounds of root, leaves, etc., had been
produced from water alone, and that it was the only nu-
triment of plants. Fish, he asserted, live on water, and
nevertheless, they contain all the peculiar animal sub-
stances; the latter are therefore produced from water.

Basing his belief on such imaginary proofs as these,
van Helmont was convinced of the transformation of
water into earthy matter. With respect to his views
concerning the four Aristotelian elements, he denied alto-
gether that fire could be of a material nature, but it is un-
certain whether he regarded air as an element or not.

PERIOD OF MEDICAL MYSTICISM 71

His conception of the elements also differed from those of
Basil Valentine and Paracelsus, for mercury, sulphur and
salt were not to be detected in the human body.

Until the time of van Helmont little was known con-
cerning gases. Pliny had spoken of "spiritus," which
possessed properties differing from those of ordinary air;
and of terrestrial emanations, some of which were com-
bustible, others unendurable. But even Basil Valentine
looked upon all such as common airs with differing im-
purities. Paracelsus had observed the evolution of gas
when sulphuric acid is poured on iron, but this had ap-
pealed to him only as a mere expulsion of air. Van Hel-
mont, however, changed the whole aspect of the question
and proved himself an investigator of the first rank when
he opened out a new field for chemistry by his researches
on gases. In his writings the word "gas" occurs for the
first time, a word he probably derived from the German
"gascht," the foam which appears during the process of
fermentation ; and by this generic name he classed all
such emanations as could not be brought into the liquid
state. For example, the gases now known as hydrogen,
carbonic acid, and sulphurous acid were distinguished
by van Helmont from vapors, in so far that the latter were
condensed to liquids upon cooling, while the former were
not.

The views of van Helmont on the composition of sub-
stances also were far in advance of any of his predeces-
sors, and he recognised much more clearly than his con-
temporaries the unalterability of matter in many instances.
Van Helmont further showed that the same substance
continued to exist in many of its compounds, as, for ex-
ample, silver in its salts; and demonstrated by quantita-
tive experiment that if one body combines with another and
is then precipitated, the weight so obtained is equal to
that originally taken; e.g., he found that silica, when
fused to a glass with potash and again precipitated by the
addition of an acid, lost nothing in weight. He had there-

72 CHEMISTRY

fore clearly grasped the fundamental idea of the theory
of the conservatism of matter in certain cases.

When he came to consider physiological and patholog-
ical phenomena, van Helmont accepted the doctrines of
Paracelsus only in part. As before mentioned, he con-
sidered that the presence of mercury, sulphur and salt in
the human body was unproven ; and held that the acid of
the gastric juice brought about digestion, but that this pro-
duced illnesses if present in excess, as it could not then
be neutralized by the alkali present in the bile, as under
normal conditions, when the mixture took place in the
duodenum. He therefore declared that diseases resulting
from such incomplete neutralization should be treated by
the prescription of alkalis or acids according to their na-
ture. These views show a distinct advance upon those of
Paracelsus, as van Helmont endeavored to decide theoreti-
cal questions by the aid of experiments with juices and
other secretions of the body, thereby laying the first foun-
dation of chemical physiology.

The footsteps of this iatro-chemist were closely fol-
lowed by his son, Francis Helmont, whose 'Paradoxical
Dissertations' are a mass of medical and theological para-
doxes, scarcely to be paralleled in the history of literature.
He did a service, however, by publishing the collected
works of his father in 1648. These works, which ap-
peared under the title 'Ortus Medicinas vel Opera et Opus-
cula Omnia,' were translated into German, English and
French, and passed through three Latin editions.

In Germany and the Netherlands, various other physi-
cians, well equipped with chemical and medical knowl-
edge, were also active in combating many evils and en-
deavored to separate true scientific doctrines from mys-
ticism ; among these were Daniel Sennert and Angelo Sala.
Sennert, who was born at Breslau in 1572, was educated
at Wittenberg, where he became professor of medicine,
and died in 1637. He wrote "Hypomneuma Physica," in
which he contradicts many of the Aristotelian principles;

PERIOD OF MEDICAL MYSTICISM 73

and altho he was unable to disentangle himself from
many of the false conceptions of the Paracelsists, he did
much to reconcile the adherents of the Hippocratic school
to the new medicine, indicating the efficacy of chemical
remedies when properly used and pointing out that the
new medicine did not ignore the facts learned empirically
under the old system, but attempted to interpret them cor-
rectly.

Sala was born at Vicenza in 1576 and died in 1637. He
had a wide knowledge of chemistry for the period in which
he lived, and formed correct ideas with regard to the com-
position and deportment of many chemical compounds ; for
example, he states that salmiac is composed of carbonate
of ammonia and hydrochloric acid, and that nitric acid
may be expelled from its salts by means of oil of vitriol.
The works on chemistry by Sala are as follows : 'Saccha-
rologia' (1637), 'Hydrelseologia' (1639), and 'Opera med-
ico-chymica' (1647, io93)-

Other influential men of this time were Francois de la
Boe Sylvius, Otto Tachenius and Thomas Willis. Sylvius
was born at Hanau in 1614, but his life was mainly spent in
Holland. In learning and culture he far surpassed most of
his contemporaries, and he ably filled the chair of medicine
in Leyden until his death in 1672. Sylvius directed all his
efforts to showing that the physiological and pathological
processes occurring in the human body were purely of a
chemical nature, and his views were in the main those of
van Helmont, with the spiritualistic element omitted. He
did not hesitate to prescribe preparations of antimony and
mercury, nitrate of silver, mercuric chloride, and zinc
vitriol for internal use in medicine. His "Opera omnia"
were published in Paris in 1671.

Otto Tachenius, a devoted pupil and follower of Sylvius,
was born at Herford in Westphalia and practised as a
physician at Venice in the middle of the seventeenth cen-
tury. He was the last iatro-chemist of importance who
adhered to the doctrines of Sylvius, and was an investi-

74 CHEMISTRY

gator of note. He made some valuable contributions to
the knowledge of the composition of chemical substances,
originating the first pointed definition of the term 'salt,'
as a compound of an acid and an alkali, and studying the
proportions by weight in which substances react chemi-
cally. One of his important observations is that in which
he noted the increase in weight which takes place when
lead is transformed into its oxide. Among the writings
of Tachenius, the following two English translations are
best known : 'Clavis to the ancient Hippocratical Physick
or Medicine made by manual experience in the very foun-
tains of nature, whereby through fire and water, in a
method unheard of before, the occult mysteries of nature
and art are unlocked and clearly explained by a compen-
dious way of operation' (1677) 5 an<^ 'Hyppocrates Chym-
icus' (1677).

In 1659 appeared the 'Diatribe de Fermentation' of
the English chemist Willis, who held that fermentation
was a decomposition brought about by communication of
a vibratory motion to the particles of must, and the re-
sulting separation of their loosely combined components.
This theory was developed by Stahl forty years later.

The iatro-chemical doctrines contributed much to the
general advancement of the science of chemistry, but two
mistakes were made by the iatro-chemists : they endeav-
ored to explain, on chemical principles, all the changes
and processes occurring in the body — an attempt which
was futile for the chemistry of that day; and, secondly,
they set too narrow a limit for chemistry, which was not
destined to remain in a subordinate position. Conse-
quently, their medico-chemical ideas were upset after
the middle of the seventeenth century, altho the tenet of
the Phlogistic Period — the phlogistic hypothesis, which
predominated during most of the eighteenth century —
was indicated by many of the iatro-chemists.

No mention has been made thus far of those distin-

Fig. 13 — Melting Furnace for Iron.
An illustration from Georg Agricola's 'De re Metallica libri XII*
(1546).

76 CHEMISTRY

guished technical chemists — Georgius Agricola, Bernard
Palissy and Johann Glauber — who promoted applied chem-
istry during the iatro-chemical age. This was made
necessary, since they worked independently of the main
iatro-chemical current and, in general, only fostered chem-
istry in its applications to industries.

Contemporaneous with Paracelsus, but forming a
strong contrast to him, was the true investigator, Geor-
gius Agricola, who was born at Glauchau, near Meissen,
in 1494, and died while mayor of Chemnitz in 1555. Agri-
cola was a noted physician, but devoted himself more par-
ticularly to the study of mineralogy and metallurgy, writ-
ing little on medical subjects and not troubling himself
about the storm over the revolution of Paracelsu^. His
works, which are indispensable to the history of metal-
lurgy and mineralogy, are characterized by clearness and
intelligibility; they are as follows: 'De re metallica libri
XII, quibus officia, instrumenta, machinse, ac omnia
denique ad metallicam spectantia non modo luculentis-
sime describuntur, sed et per effigies suis locis insertas,
adjunctis Latinis Germanicisque appellationibus, ob ocu-
los ponuntur, ut clarius tradi non possint' (1546); 'De
ortu et causis subterraneorum — de natura eorum quae ef-
fluunt ex terra — de natura fossilium — de veteribus et
novis metallis — Bermannus, sive de re metallica dialo-
gus' (1558), and 'De mensuris et ponderibus, . . . de
precio metallorum et monetis' (1580). It was through
these writings that the important metallurgical operations
first became generally known; Agricola was also among
the first to indicate a method by means of which it was
possible to estimate approximately the amount of metal
in an ore, and to explain intelligibly the manufacture of
various preparations of industrial importance.

Vanuccio Biringucci, author of a work on metallurgy
entitled 'Pirotecnica' (1540), in which various techni-
cal processes are described, like Agricola, held aloof from
the discussion of tht iatro-chemical questions current in

PERIOD OF MEDICAL MYSTICISM 77

his time. He gave directions for preparing ultramarine,
distinguishing it from copper azure.

Bernard Palissy busied himself in the domain of the
ceramic art, and succeeded in affixing durable enamels on
earthenware vessels, especially on those of faience pot-
tery. His observations on enamels, on the burning-in of
colors, and on the use of various clays for pottery, are
embodied in his work, 'L'Art de Terre.' His works are
clearly written, and show that he contributed to the
founding of agricultural chemistry and mineralogy, and
that he combated every speculation not based upon ob-
servation and experiment; among these are his "Dis-
cours admirables de la nature des eaux et fontaines, tants
naturelles qu' artifkielles ; des metaux, des sels et salines,
des pierres, des terres, du feu et des emaux; avec plu-
sieurs autres excellents secrets des choses naturelles"
(1580) ; and the "Moyen de devenir riche et la maniere
veritable par laquelle tous les hommes de la France pour-
ront apprendre a multiplier et augmenter leurs thresors
et possessions" (1636). Along with Agricola, Palissy
was the chief exponent of experimental chemistry in his
time.

The next name of importance is that of Johann Rudolf
Glauber, who was born in Franken, Bavaria, in 1604, and
died at Amsterdam in 1668, and who still shares a some-
what hazy popular fame as the discoverer of "Glauber's
salt" (sodium sulphate). This compound, which is men-
tioned in his 'De Natura Salium,' published in 1658, was
obtained from the residue left in the preparation of hy-
drochloric acid, and, under the name "sal mirabile," was
prized highly by physicians. The collected works of
Glauber were translated into English and published in a
folio volume, containing three parts embodying twenty-
six treatises, by Christopher Packe, in London, in 1689.
In these treatises are found clear descriptions of the prep-
aration of many chemical compounds, and intelligible ex-
planations in theoretical points of chemistry. Glauber

78 CHEMISTRY

also showed intelligence in questions of national and do-
mestic economy, and on numerous occasions he sought
to prove that Germany should work up and improve its
own products, and not leave this for other countries to do.
He was, however, inoculated with the prejudices of his
age, and was addicted to the fantastic extravagances of
alchemy. In writing he sometimes affected the style of
the older alchemists, and the following passage from a
discussion on "concentrating and amending metals by
niter" will show how humorously absurd some of his
ideas were : "First a man is to be made of iron, having
two noses on his head, and on his crown a mouth which
may be opened and again close shut. This if it be to be
used for the concentration of metals is to be inserted into
another man made of iron or stone, that the inward head
only may come forth of the outward man, but the rest
of his body or belly may remain hidden in the belly of
the exterior man. And to each nose of the head glass
receivers are to be applied, to receive the vapors ascend-
ing from the hot stomach. When you use this man you
must render him bloody with fire to make him hungry
and greedy of food. When he grows extremely hungry
he is to be fed with a white swan. When that food shall
be given to this iron man, an admirable water will ascend
from his fiery stomach into his head, and thence by his
two noses flow into the appointed receivers; a water, I
say, which will be a true and efficacious aqua-vitae ; for
the iron man consumeth the whole swan by digesting it,
and changeth it into a most excellent and profitable food
for the king and queen, by which they are corroborated,
augmented, and grow. But before the swan yieldeth up
her spirit she singeth her swan-like song, which being
ended, her breath expireth with a strong wind, and leav-
eth her roasted body for meat for the king, but her anima
or spirit she consecrateth to the gods that thence may
be made a salamander, a wholesome medicament for men
and women."

PERIOD OF MEDICAL MYSTICISM 79

In his 'Proserpine: or, the Goddess of Riches/ Part
III, Glauber details "the fundamental process, how to
make good gold out of silver, with profit, and how to sep-
arate good gold and silver out of iron, tin, copper, and
lead."

Notwithstanding his adherence to mysticism, Glauber
enriched chemistry in an eminent degree by his discov-

!Fig. 14 — Glauber's 'Iron Man.'

eries. In attacking the question of the composition of
bodies, he commenced by considering the conditions under
which certain salts were produced, and the products of
their mutual decomposition. Instead of preparing the
chlorides of metals as heretofore, by heating the metal
with sublimate (mercuric chloride), he treated the metal
directly with hydrochloric acid, and concluded that the
salt produced was merely a solution of the metal in the
acid. This was a convincing blow to the time-honored

80 CHEMISTRY

idea that the mercury of the sublimate had entered into
the composition of the chlorides obtained.

Moreover, Glauber taught how to prepare hydrochloric
acid from rock salt and oil of vitriol, and also fuming
nitric acid from saltpeter and white arsenic. The prepa-
ration of hydrochloric acid, or 'spirit of salt,' is described
in the first section of the second part of the 'Miraculum
Mundi.' Here also is given the method of obtaining 'sal
mirabile,' the discovery of which first appeared in his
*De Natura Salium.' To the discussion of the 'spirit of
s~lt,' Glauber adds : "Plainly after the very same manner
as we have taught spirit of salt to be prepared, so may
also be made 'Aqua fortis' (nitric acid). . . . In-
stead of salt take niter, and you will have 'Aqua fortis.' "
For a long time afterward the acid thus obtained (fu-
ming nitric acid) was known as 'spiritus nitri fumans
Glauberi.'

The combination of acids with metals or alkalis was
attributed by Glauber to a certain associative tendency,
which he termed 'Gemeinschaft.' He never employed the
term 'affinity,' altho, as mentioned before, it was already
the property of chemical literature. In Glauber's works
we find a clear description of the preparation of sulphate
of ammonia, formerly known as "sal ammoniacum secre-
tum Glauberi," and the discovery of nitrate of ammonia,
'nitrum flammans.' He was also the first to prepare chlo-
ride of arsenic, and ferric and plumbic chlorides, and to
him is due a clearer knowledge of the chemistry of anti-
moniate of potash and other antimony compounds. He
prepared impure zinc chloride by heating calamine
strongly with hydrochloric acid; proved that copper sul-
phate, blue vitriol, is produced by boiling copper with
oil of vitriol; and he was the first to mention a case of
what is called double decomposition. His observations on
the latter are of interest; to quote from one of his trea-
tises, "Aqua regia which has taken gold into solution
Jdlls the salt of tartar (potash) of the liquor of flints

PERIOD OF MEDICAL MYSTICISM 81

(silicate of potash) in such a way as to cause it to aban-
don the silica, and in exchange the salt of tartar para-
lyzes the action of the aqua regia in such a way as to make
it let go the gold which it had dissolved. It is thus that
the silica and gold are both deprived of their solvents.
The precipitate is composed, then, at the same time of
gold and of silica, the weights of which together represent
that of the gold and of the silica originally taken."

With Glauber and Tachenius the period of Medical
Mysticism closes. Both of them advanced chemistry by
valuable observations, and in many of their chemical ideas
and also in point of time, they really belong to the next,
the Phlogistic, Period. The iatro-chemists had preserved
a real science throughout a troublous and Philistine pe-
riod, while their often fantastic speculations had caused no
inconsiderable increase in the knowledge of chemical
preparations. However, the advance in the knowledge of
the composition of substances and in the observation of
reactions first became pronounced toward the close of the
Period.

In the works of Agricola, Biringucci, Caesalpino, Glau-
ber and Palissy, stress is laid upon accurate description of
technical operations, and it is from these works that
knowledge accrues of the progress made in technical
chemistry during the Iatro-chemical Period.

With regard to the extension of metallurgical knowl-
edge, it is to be expected that the iatro-chemists were more
interested in the salts prepared from metals than in the
latter themselves, as there was always the possibility of
chemical preparations proving of value in medicine. Nev-
ertheless, especially in the works of Agricola, referred to
before, it is found that a knowledge of the individual
metals and of metallurgical operations became extended in
the sixteenth century, as a result of the publication of
what had hitherto been kept secret. The methods of ob-
taining iron became known through the works of Agri-

82 CHEMISTRY

cola, and he was the first to describe the production of
steel by the puddling process. It is interesting to note
that steel was looked upon as a very pure iron. Of the
other metals, the separation of gold and silver by means
of nitric acid, and the amalgamation process became gen-
erally known; tin was employed in the sixteenth century
for tinning iron; and altho zinc and bismuth were often
confused with antimony, yet a better knowledge of them
was acquired, and the tutty from zinc ores was employed
for making brass.

One of the earliest treatises on glass manufacture is
that by Antonio Neri, entitled 'L'arte vetraria distinta in
libri sette; ne' quali si scoprono maravigliosi effetti e
s'insegnano segreti bellissimi del vetro nel fuoco ed altre
cose curiose/ which was published in Florence in 1612,
and in Latin at Amsterdam in 1681. In this work, Neri
details his extensive experience, and it contributed to the
diffusion of a knowledge of special ceramic operations.
In the sixteenth century are found the first dependable ob-
servations on the manufacture of ruby glass by means of
gold, and considerable skill was attained about 1600 in the
production of artificial gems. Johannes Baptista Porta
(1538-1615), of Naples, was the author of a treatise, 'De-
gemmarum adulteriis,' in which recipes for preparing imi-
tation precious stones were detailed. Agricola, in his
treatise, 'De re Metallica/ gives the first drawing of the
interior construction of a glass furnace, and in this work
as well as in Mathesius' 'Sarepta or Bergpostill' (1654),
are found explicit and interesting directions about the
manufacture of glass as carried out in Venice, Germany
and Bohemia.

In Bohemia, the glass industry began to flourish in the
sixteenth century, the purity of the materials occurring
there enabling glass manufacturers to produce the color-
less glass for which the Bohemian glass-houses have long
been famous. When the Venetian glass manufacture fell
into decay, Bohemian glass replaced Venetian. The first

PERIOD OF MEDICAL MYSTICISM 83

manufacture of glass in England is that of window glass,
established in the fifteenth century, but the product was
not satisfactory, and in the reign of Elizabeth, French art-
ists were brought to London, and these carried on their
trade of making window glass at Crutched Friars in 1557,
while flint glass was first manufactured at a glass-house
at Savoy House in the Strand. Mirror glass was manu-
factured at Lambeth by Venetian workmen brought over
by the Duke of Buckingham in 1670. Glass works were
established in France at an early date, but it was not un-
til the eighteenth century, when workmen were brought
from Germany, that a pure kind of French glass ware was
produced. One of the important discoveries of this pe-
riod was that of cobalt blue by Schiirer, a Saxon glass
blower, who obtained it on fusing the cobalteous residue
from the manufacture of bismuth with glass; this latter
became known as zaffre and smalt.

The efforts of Palissy in extending the knowledge of
ceramics have been referred to, and it only remains to
state that Johannes Porta was engaged in similar work in
Italy about the same time. These savants devoted them-
selves with self-sacrificing assiduity to the production of
glazed and colored faience, and laid the foundation of mod-
ern art pottery.

In dyeing a variety of vegetable colors were employed.
Indigo and cochineal were imported from America and the
East Indies, and numerous observations were made on
dyeing processes. Drebbel learned that a solution of tin
in aqua regia could be employed for fixing colors on cloth
about 1630, and the methods of mordanting with alum and
iron solutions were improved. The art of printing proved
for dyeing, as well as for other arts, its great pioneer and
propagator. In the middle of the sixteenth century,
Plictho's "Art of Dyeing" was published. This treatise
gave general instructions for dyeing all kinds of fabrics,
and laid the foundation for that improvement of this art
which soon after followed throughout Germany, France

84 CHEMISTRY

and England. It is interesting to note that the use of in-
digo was forbidden by the English Parliament in the reign
of Queen Elizabeth, and that this act remained in full
force till the time of Charles II.

Considerable interest was evinced in the distillation of
liquors during this Period, and numerous works upon this
subject appeared; among these were the following: Hie-
ronymus Saler's 'Liber de arte distillandi de compositis'
(1500, 1512, 1527) ; John French's 'The Art of Distilla-
tion' (1651); and Elsholtz's 'Distillatoria curiosa seu
ratio ducendi liquores coloratos per alembicum' (1674).
Many improvements were made both in distilling appara-
tus and in the methods of distillation, and the distillation
of brandy became an industry.

The word distillation up to the end of the fourteenth
century meant the separation of the more light or subtle
parts of anything from the more heavy or gross by a proc-
ess of dropping. Thus Geber and others included the fil-
tration of a liquid as a variety of distillation. The Latin
word "distillo" applies to a dropping liquid, but such em-
ployment of the term does not appear after the fourteenth
century in chemical works, altho the older use of "distil"
is still found in ordinary writings, especially in poetry, and
occurs in Fielding and Shakespeare. The process of dis-
tillation was classified in various ways; for instance, ac-
cording to the source and mode of application of the heat,
the shape of the alembic or distillatory vessel, and the
direction impressed on the vapor upward or downward
('distillatio ascensum vel decensum').

The heat was applied in the form of the direct heat of
a fire, or the heat conveyed through water or through
sand, or the direct heat of the sun. Porta, about 1585, em-
ployed concave mirrors to concentrate the sun's rays
(Fairley). Repeated distillation was often prescribed, as
the purity of the distillate was thought to be increased by
each distillation up to the fifth distillate, which was termed
the '"quintessence." An alcoholic distillate obtained in

PERIOD OF MEDICAL MYSTICISM 85

this way from selected wine was considered to possess
great medicinal value.

During the sixteenth and seventeenth centuries the dis-
tillation of fermented alcoholic liquids became subject to
State supervision in many European countries. In Ire-

Fig. 15 — Saltpeter Manufacture.
Plant for preparing saltpeter on a large scale (about 1600).

land, where it has been shown that the distillation of a
spirit from fermented barley was practiced in 1170, up to
1556 the distillation of spirits was carried on without li-
cense or taxation. In the reign of Henry VIII, distil-

86

CHEMISTRY

leries were established in Pembroke by Irish settlers, and
it is considered likely that the soldiers of Henry II, 300
years previous, brought back with them the knowledge of
whisky, or 'uisque-beatha.' The manufacture of 'aqua

Fig. 16 — Glauber's Distilling Apparatus.
(a) — Oven with distilling vessel installed ; (c) — Form of distilling
vessel ; (d) — Cross-section of same ; (e) — Method of heating
by coal.

vitse' from malt appears to have been common in Scot-
land and England in 1494, and, in the middle of the seven-
teenth century, the manufacture of spirits was made a
source of revenue by excise duties on the amount manu-

PERIOD OF MEDICAL MYSTICISM 87

factured. In the Tudor and Stuart period, licenses had
been required to use stills.

The knowledge of chemical compounds, especially the
preparation of inorganic compounds, showed decided im-
provements ; and the beginnings of qualitative analysis are
to be sought for in this Period, in so far that conclusions
concerning the presence of one or another constituent
were deduced from the appearance and behavior of pre-
cipitates and of salts which crystallized out from solutions.
Glauber designed several forms of furnaces and casting
vessels which were found to be useful in the preparation
and investigation of a number of inorganic substances.

As a result of the attention paid to the products of vege-
table and animal assimilation, organic compounds became
known in rapidly increasing numbers, but the composition
of these bodies remained quite undiscernible. It is worthy
of note that many of the iatro-chemists assumed that "oil
or fat contains a hidden acid," basing their conclusion on
the old observation that fats were acted upon and changed
by alkalies.

The importation of sugar from Spain, Portugal, Ma-
deira, the West Indian islands, and Brazil soon made this
article better known throughout Europe. Libavius in his
'Alchymia' (1595) mentions "Sacchari crystallini quod
candi appellant," and he recommends a plan of purifying-
Madeira sugar by means of albumen, and Angelus Sala in
his 'Saccharalogia' advises the use of egg albumen and
lime water for this purpose.

Milk sugar, occurring in the milk of mammalia, espe-
cially in that of the herbivora, was first examined by
Fabrizio Bartoletti in 1619; it was termed by him "manna
s. nitrum seri lactis." It was more closely examined by
Testi in 1698. Glauber noticed in 1660 that a granular
sugar is contained in honey, raisins and in the juice of
sweet cherries, but he did not point out that it differs from
cane sugar.

CHAPTER VI

THE EARLY PHLOGISTIC PERIOD

Heretofore the inducements to a study of chemical
phenomena had been successively a belief in the possibility
of transmutation, and a conviction in the potency of
heroic medicines prepared in the chemical laboratory.
But from the middle of the seventeenth century onward
another aim is manifest in the works of the masters; for,
from the time of Boyle forward, the great end of chemis-
try was recognised as being the discovery of new chemical
facts, with the object of arriving at the truth alone, and,
thanks to the spirit of true investigation which had begun
to extend itself to chemistry and the effect of the induc-
tive method of Francis Bacon, chemistry assumed irs
proper place as a science.

As an approach is made to modern times, it becomes
more difficult to define historically the successive phases
of chemistry. The learned societies which were founded
in the second half of the seventeenth and beginning of the
eighteenth centuries, and whose periodicals furnished ever-
accumulating data for the discussion of old and the initia-
tion of new theories, and disseminated the results of
chemical investigations in general, assisted materially to-
ward the healthy progress of chemical science; but nev-
ertheless firm obsequiousness to any one school of scien-
tific thought was not to be expected, nor was it found.

The London Royal Society was founded by Charles II.,
and was incorporated by him in 1662, under a royal
88

THE EARLY PHLOGISTIC PERIOD 89

charter, for the improvement of natural knowledge. The
first volume of the 'Philosophical Transactions' of that
society bears the date 1665, and ever since its foundation
the Royal Society has been a nucleus around which has
clustered the scientific genius of Great Britain. In 1666,
the Academie Royale was instituted in Paris under the
protection of Louis XIV., and its 'Memoires' began to
appear in 1699. Other scientific societies — the Accademia
del Cimento of Florence (1657), the Academia Naturae
Curiosum of Vienna (1652), and the Berlin Academy
(1700) — also brought together those who were in sym-
pathy through their devotion to knowledge, and by the in-
terchange of their ideas thought was quickened and the
advance of science aided. The reciprocal action of chem-
istry and allied branches of science upon each other was
also promoted by bringing together their respective ex-
ponents, and the discussion of scientific researches helped
more thoroly to sift the evidence on which their con-
clusions were based, and tended to promote increased ac-
curacy and simplicity of thought and expression.

Altho the literature of the day bears record of many
observations, isolated discoveries, and discussions on
chemical problems, yet there was one problem which en-
grossed the attention of almost all philosophers during the
seventeenth and eighteenth centuries, and this was the
explanation of fire and the phenomena caused by fire.
Notwithstanding the fact that here scarcely any two
chemists were agreed in their conclusions, their modes
of arriving at them showed remarkable similarity. Little
note was taken of the proportions by weight in which sub-
stances entered into reaction, the qualitative side of
phenomena alone being considered.

This period of about one hundred and twenty years,
from Boyle to Lavoisier, may therefore be described as
that of Qualitative Chemistry — a step toward the quan-
titative work of the Modern Period, and an immense
step forward from the speculative and fortuitous chemis-

90 CHEMISTRY

try of the preceding periods. It was a period of generali-
zation, for just as fire was to be explained by the assump-
tion of one general principle, 'phlogiston' — a doctrine
which influenced chemists to such an extent that this pe-
riod is characterized as the Phlogistic Period — so the gen-
eral properties of acidity and causticity were to be viewed
as conferred by one fundamental acid and one funda-
mental alkali respectively; and altho it was itself handi-
capped by erroneous views, the Phlogistic Period con-
tributed largely to the refutation of alchemical and iatro-
chemical errors, and was a highly productive period for
chemistry.

Robert Boyle (1627-1691) was the seventh son and
fourteenth child of Richard, Earl of Cork. He was born
at Lismore, in Munster. At eight years of age he was
sent to Eton, where, says he, a perusal of 'Quintus Cur-
tius' "conjured up in me that unsatisfied appetite for
knowledge that is yet as greedy as when it was first
raised." After about four years at Eton, Boyle went to his
father's seat in Dorset and afterward traveled. He be-
came a student at Geneva and continued his studies at the
manor of Stalbridge from 1644 to 1654, when he settled at
Oxford. In 1668 Boyle moved to London and was a promi-
nent member of the then newly constituted Royal Society.
He was elected president in 1680, but refused to serve, ow-
ing to a scruple he entertained as to taking oaths. In 1689
his health began to fail and he issued an advertisement re-
stricting the visits of his acquaintances. He also had a
board put up outside his house anouncing when he re-
ceived visits. Boyle's health had never been good; from
the age of twenty-one he suffered from stone, and much
feared that if it forced him to take to his bed the pain of
it would become intolerable. He died, however, without
pain, and almost without serious illness.

Boyle developed talent early, and at twenty-one he had
already written on ethics and published several moral and
religious essays. In 1665 he published his 'Occasional

THE EARLY PHLOGISTIC PERIOD 91

Reflection upon Several Subjects,' which procured him
the satire of Swift in 'A Pious Meditation upon a Broom-
stick, in the style of the Honourable Mr. Boyle.'

It would be needless to attempt to go over the whole
ground of Boyle's work, altho there is much in it of
interest even at the present time, as, for example, his
papers on the 'Saltness of the Sea,' and the 'Nature of
the Sea's Bottom,' and his 'Essay of the Intestine Motions
of the Particles of Quiescent Solids wherein the absolute
Rest of Bodies is called in question.' He was perhaps
the first to draw attention to the desirability of studying
the forms of crystals, and his paper on the 'Figures of
Salts' contains many curious observations ; in his 'Experi-
ments about the Superficial Figures of Fluids, especially
of Liquors contiguous to other Liquors,' he breaks ground
which has taxed the energies of our greatest mathema-^
ticians. His 'Treatise on Cold' abounds with striking and
original experiments ; for example, he demonstrates the ex-
pansive power of freezing water by bursting a gun barrel
filled with water and securely plugged, by placing it in a
mixture of snow and salt, a freezing mixture which he
himself introduced in England. His 'Essays on the Use-
fulness of Experimental Natural Philosophy' were of the
greatest service in his time in furthering the cause of
science by showing how the material interests of civiliza-
tion may be promoted by its study; and, lastly, his tract
on 'Unsucceeding Experiments' must have been, to quote
Thorpe, "as the wine of gladness and the oil of consola-
tion to many a despondent virtuoso."

Boyle was born in the year in which Bacon died; and
Boyle's place in the history of science is that of the first
true exponent of the Baconian method, and the 'Sceptical
Chymist' is his greatest work. This work probably con-
tains a greater number of well-authenticated facts than
is to be found in any other chemical treatise of its day.

But the real merit of this work consists in its deter-
mined attack on the authority of the Peripatetics and

92 CHEMISTRY

the Paracelsians. To quote from his own statement in
'The Sceptical Chymist' :

"To acquaint you with divers of the conjectures (for
I must yet call them no more) I have had concerning the
principles of things purely corporeal : for though, because
I seem not satisfied with the vulgar doctrines, either of
the Peripatetick or Paracelsian schools, many of those,
that know me, . . . have thought me wedded to the Epi-
curean Hypothesis (as others have mistaken me for a
Helmontian). ... I should tell you, that I have some-
times thought it not unfit, that to the principles, which
may be assigned to things, as the world is now constituted,
we should, if we consider the great mass of matter, as
it was whilst the universe was in making, add another,
which may conveniently enough be called an Architecton-
ick principle or power ; by which I mean those various!
determinations, and that skilful guidance of the motions
of the small parts of the universal matter by the most
wise Author of things, which were necessary at the be-
ginning to turn that confused chaos into this orderly and
beautiful world. . . . For I confess I cannot well conceive,
how from matter, barely put into motion, and then left
to itself, there could emerge such curious fabricks, as the
bodies of men and perfect animals, and such yet more
admirably contrived parcels of matter, as the seeds of
living creatures."

Boyle is severe upon the affected mysticism of the Spa-
gyrists. They may be as obscure as they like about their
elixir, and the rest of their grand arcana, "yet when they
pretend to teach the general principles of natural philoso-
phers, this equivocal way of writing is not to be endured.
For in such speculative inquiries where the naked knowl-
edge 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

THE EARLY PHLOGISTIC PERIOD 93

sense of what he equivocally expresses, to that of learn-
ing the truth of what he seems to deliver."

Indeed, Boyle does not hesitate to say that the reason
why the Spagyrists wrote so obscurely of their three great
principles was, according to Thorpe, "that not having
clear and distinct notions of them themselves, they could
not write otherwise than confusedly of what they had
confusedly apprehended: they could scarcely keep them-
selves from being confuted but by keeping themselves
from being clearly understood — home thrusts which must
have made many a Helmontian wince. The effect of such
hard hitting is made evident on the most superficial com-
parison of the general style of chemical treatises imme-
diately preceding Boyle's time with those published toward
the close of the seventeenth century."

The 'Sceptical Chymist' compelled the decline of the
doctrine of the 'tria prima,' and before the close of the
century the Paracelsians were as much out of date as
a Phlogistian would be to-day. Boyle indeed appeared
to incline to the belief that all matter is compounded of
one primordial substance — in other words, that all mat-
ters are merely modifications of the 'materia prima.'

To quote again from his 'Sceptical Chymist' :

"I consider, that if it be as true, as it is probable, that
compounded bodies differ from one another but in the
various textures resulting from the bigness, shape, motion,
and contrivance of their small parts, it will not be irra-
tional to conceive, that one and the same parcel of the
universal matter may, by various alterations and contex-
tures, be brought to deserve the name, sometimes of a
sulphureous, and sometimes of a terrene, or aqueous body.'*

How closely he was in accord with the modern spirit is
shown in this remarkable passage : "I am apt to think
that men will never be able to explain the phenomena
of nature, while they endeavor to deduce them only from
the presence and proportions of such or such material in-
gredients, and consider such ingredients or elements as

94 CHEMISTRY

bodies in a state of rest; whereas indeed the greatest
part of the affections of matter, and consequently of
the phenomena of nature, seem to depend upon the mo-
tion and contrivance of the small parts of bodies."

It was possible for Boyle to expose the shortcomings
and fallacies of the then prevalent idea of Element or
Principle: "I mean by elements, as those chymists,
that speak plainest, do by their principles, certain primi-
tive and simple, or perfectly unmingled bodies; which
not being made of any other bodies, or of one another,,
are the ingredients of which all those called perfectly;
mixt bodies are immediately compounded, and into which
they are ultimately resolved. I need not be so absurd,
as to deny, that there are such bodies as earth and water,
and quicksilver and sulphur: but I look upon earth and
water, as component parts of the universe, or rather of
the terrestrial globe, not of all mixt bodies."

This conception of an element gave the term a positive
meaning.

Boyle also looked forward to the discovery of a much
greater number of elements than was at that time as-
sumed, at the same time maintaining that many of the
substances then held to be elementary were not really so.
Boyle was the first to state clearly that a chemical com-
pound results from the combination of two constituents,
and that it has properties entirely different from those
of either of its constituents alone. He was, therefore,
enabled to draw a sharp distinction between mixtures and
chemical compounds, and to grasp clearly the main prob-
lem of chemistry — the investigation of the composition
of substances. In doing this he had the solid ground-
of experience and experiment under his feet, and could
always bring forward evidence for the probability of his
views. His endeavors to get at the root of the compo-
sition of bodies gave an impetus to analytical chemistry,
which before his time could hardly be said to exist; and
we are at the same time indebted to him for ixing the

THE EARLY PHLOGISTIC PERIOD 95

meaning of a "chemical reaction." Boyle appears to
have been the first to employ the term analysis, in the
sense in which it has since been used by chemists.

Also he devoted much attention to the inquiry of the
cause of combustion and other similar phenomena, and
altho his attempts at explaining these were not very
successful, his experiments on the role played by air in
combustion aided the later solution of the problem. His
investigations on air and gases led him in 1660 to the
well-known discovery of the law that "the volume of a gas
varies with the pressure" (Marriotte educed this inde-
pendently in 1677).

Boyle's writings, which were extensively read in his
own time, are characterized by simplicity of style and
clearness of expression; they offer, as von Meyer ob-
serves, ''an agreeable contrast to the works of many of
the other chemists of his time, who sought to hide their
deficiencies in clear thought and accurate knowledge by
metaphorical and mysterious language." In addition to
other papers published in the 'Philosophical Transactions/
the following works of his, which were brought out both
in English and Latin, are to be particularly mentioned:
'The Sceptical Chymist' ('Chemista Scepticus'), first pub-
lished anonymously in 1661, and afterward in many edi-
tions with Boyle's name as author ; 'Tentamina quae dam
Physiologica' (1661); and 'Experimenta et Considera-
tions de Coloribus' (1663). Editions of his complete
works were published in London in 1700, 1725, and 1744.

A contemporary of Boyle who made important observa-
tion on combustion was Robert Hooke (1635-1702).

Hooke was born in the Isle of Wight and was originally
intended for the Church, but he was of a weakly consti-
tution, and much subject to headache, and owing to these
causes the idea was finally abandoned. His leanings were
first shown in a considerable aptitude, as a boy, for con-
structing mechanical toys. After his father's death Dr.
Busby took him into his house and supported him while

96 CHEMISTRY

at Westminster School. After leaving school he went to
Christ Church, Oxford, and, in 1655, he was introduced
to the Philosophical Society. Here his talents were speed-
ily discovered and he was employed to assist first Dr.
Willis and then Mr. Boyle. In 1662 he was made curator,
of experiments to the Royal Society, and when this body
was established by charter he was one of the first nom-
inated to fellowship. He obtained several professional
posts and in 1665 he published in folio his 'Micrographia,
or some physiological descriptions of minute bodies made
by magnifying glasses, with observations and inquiries
thereupon.' It was dedicated to Charles II.

It is usual to state that Hooke anticipated the modern
view of the nature of combustion in this treatise; but
it will appear from the following extract that whatever
value may be assigned to his work, it cannot be claimed
that he did more than recognize the part played by the
air in the process, while still adhering to the conception
of a 'sulphureous principle' which is lost by the body dur-
ing combustion. Thus he observes :

"From the experiment of charring of coals . . . we may
learn . . . that the air in which we live, move, and breath,
and which encompasses very many, and cherishes most
bodies it encompasses, that this air is the menstruum, or
universal dissolvent of all sulphureous bodies . . . that
the dissolution of sulphureous bodies is made by a sub-
stance inherent, and mixt with the air, that is like, if
not the very same, with that which is fixt in saltpeter,
which by multitudes of experiments that may be made
with saltpeter, will, I think, most evidently be demon-
strated. . . . The dissolving parts of the air are but few,
that is, it seems of the nature of those saline menstruums,
or spirits, that have very much flegme mixt with the spir-
its, and therefore a small parcel of it is quickly glutted,'
and will dissolve no more; . . . whereas saltpeter is a
menstruum, when melted and red-hot, that abounds more
with those dissolvent particles, and therefore as a small

THE EARLY PHLOGISTIC PERIOD 97

quantity of it will dissolve a great sulphureous body, so
will the dissolution be very quick and violent. ... It is
observable, that, as in other solutions, if a copious and
quick supply of fresh menstruum, though but weak, be
poured on, or applied to the dissoluble body, it quickly
consumes it: so this menstruum of air, if by bellows, or
any other such contrivance, it be copiously apply'd to
the shining body, is found to dissolve it as soon, and as
violently as the more strong menstruum of melted nitre."

The completion of Hooke's theory was effected by John
Mayow, who was born in the parish of St. Dunstan, Lon-
don, in 1645. In I&74 he produced the treatise on
which his fame rests; it is entitled Tractatus quinque
medico-physici quorum primus agit de salnitro et spiritu
nitro-aereo, secundus, de respiratione, tertius de respira-
tione foetus in utero et ovo, quartus de motu musculari et
spiritibus animalibus, ultimus de rhachitide; studio Joh.
Mayow, LL.D. & Medici, nee non Coll. Omn. Anim. in
Univ. Oxon. Socii. Oxonii e Theatro Sheldoniano, An.
Dom. mdclxxiv/

Mayow's assumption — that atmospheric air contained a
substance, the 'spiritus nitro-aereus' (also present in salt-
peter), which combined with metals when they were cal-
cined, and which sustained respiration and converted
venous blood into arterial — was bound to result in the
right interpretation of the phenomena of combustion, when
the observations which had led to it were sufficiently ex-
tended. Mayow's early death in 1679 was perhaps the
reason why this did not occur, the development of the
new chemistry being greatly retarded as a result.

Two members of the French Academy became promi-
nent at this period, Lemery and Homberg. Wilhelm
Homberg (1652-1715) was a lawyer, but gave up the
practice of his profession to study natural science and
medicine. He knew both Boyle and Kunckel, and was
a good observer and skilful in carrying out his experi-
ments, but a poor interpreter of results. He was tram-

98 CHEMISTRY

meled by alchemistic views, maintained that substances
consisted of mercury, sulphur, and salt, and took little
part in establishing the new theories. He contributed a
large number of papers on chemical, zoological, botani-
cal, and physical subjects to the French Academy.

Nicolas Lemery (1645-1715) was especially renowned
as a teacher, tho he was also a good worker, dealing
in the practical rather than the theoretical. His son,
Ludwig Lemery, was also a distinguished chemist. The
elder Lemery's greatest work was the writing of his text-
book of chemistry, 'Cours de Chimie' (1675), which em-
braced all that was known of chemistry, and endeavored
to give a suitable connection between the facts recorded,
and to systematize them. This was for many years the
best text-book on the science, and was issued in thirty-two
editions. Thirteen editions appeared during the author's
lifetime, and a last much-changed one was issued by Baron
in 1756.

Two German contemporaries of Boyle were Johann
Kunckel and Johann Joachim Becher. Kunckel was es-
sentially an experimentalist; he was imbued with a belief
in the Philosopher's Stone, and regarded mercury as the
necessary component of a metal. He was born at Rends-
burg in 1630, and died in 1702. He was the son of an
alchemist, and himself passed much of his life as the
employee of sundry German princes (among them the
Elector John George of Saxony, the great Elector of
Brandenburg, and the Dukes of Lauenburg) in the unsuc-
cessful pursuit of the Philosopher's Stone.

Before the second half of the seventeenth century the
blowpipe had been used neither in chemical analysis nor
for working glass. It was Kunckel's task to demonstrate
the ease with which a metallic calx might be reduced by
heating it on charcoal before the blowpipe, and to insti-
tute a more expeditious mode of hermetic sealing than
that of inserting the drawn-out neck of flask or other
vessel in a hot fire, hitherto in vogue.

THE EARLY PHLOGISTIC PERIOD

99

Kunckel was the first to recognize an analogy between
putrefaction and fermentation, and to show how the pro-
duction of vinegar in the latter process depended on the
initial formation of alcohol and avoidance of low tem-

Modern Forms of Blowpipes.

perature or presence of acids. Among his treatises the
following may be mentioned : 'Oeffentliche Zuschrifft von
dem Phosphoro mirabili und dessen deuchtenden Wunder-
Pilulen' (1678); 'Ars Vitraria Experimental' (1689);
and Thilosophia chemica experimentis confirmata' (1694).

ioo CHEMISTRY

Johann Joachim Becher, who was born at Speyer in
1635 and died in London in 1682, worked almost contem-
poraneously with Kunckel, altho more for the theoreti-
cal explanation of already observed facts than for the
practical side of the subject; but in his unsettled life and
his inclination toward new schemes, he resembled the lat-
ter. He worked as an alchemist at the courts in Mainz,
Munich and Vienna, but he was too honorable to deceive
his patrons, and entirely too candid to allow of his remain-
ing long in any one place. In theoretical questions
as to the composition of substances, Becher attempted
to revive the old ideas of Paracelsus in another form.
In place of mercury, sulphur and salt, he adopted three
''earths," of which all inorganic ("Subterrestrial")
bodies should consist, viz., the "mercurial," the "vitre-
ous," and the "combustible" ('terra pinguis'). The nature
of any material depended upon the proportions in which
these three fundamental earths were contained in it. Of
especial importance was Becher's assumption that when
substances were burnt or metals calcined, the 'terra pin-
guis' escaped: "Fire dissolves and breaks up all things
made up of different parts — in metals the more volatile
part is expelled." That is, he regarded combustion as a
destruction. Hence, he concluded that every combustible
substance must in itself contain the cause of combustibil-
ity, and that a substance incapable of being resolved into
others (an element) cannot burn. It was from this con-
ception that Stahl's phlogiston theory originated.

These theoretical views are to be found in Becher's
first work, 'Physica Subterranea' (1669), and in his last,
'Theses Chymicae' (1682). His doctrines acquired great
celebrity through Stahl, whose work belongs for the most
part to the eighteenth century, on which he conferred a
character of its own by his development of the phlogiston
theory.

CHAPTER VII

THE PHLOGISTIC PERIOD PROPER

One of the most interesting chapters in the history of
chemical science is that dealing with the study of the phe-
nomena of combustion and their interpretations. As
Freund observes, it lends itself specially well to the pur-
pose of indicating within the scope of not too complicated
phenomena, "how a theory arises, how it is applied, how
the conservatism inherent in the human mind is reluctant
to give up an accustomed interpretation of nature, even
when it no longer answers to the first requirements of a
theory; that is, when it no longer explains the facts and
laws observed in the class of phenomena to which it refers ;
but how after all facts are and always must be strongest,
and hence how a theory is finally given up when no longer
able to deal with the facts, and how its place is then taken
by another better fitted to do so."

The effect of heat on matter had from early times been
a subject for observation and experiment, which soon led
to classification and generalization. It was observed that
while some substances are not permanently changed when
heated (sand, noble metals, etc.), others are (wood, sul-
phur, base metals, etc.). The burning of substances — that
is the occurrence of a permanent change marked by the
appearance of flame — great evolution of light and heat, and
the remaining behind of ash — naturally arrested attention
and the view that substances were combustible in virtue
of the common presence in them of "fire matter" goes

IOI

102 CHEMISTRY

back to the time of the Greek philosophers. That the sub-
stances left behind when wood is burnt or when metals
such as copper and lead are heated, were alike called
"cineres" (ashes), bears witness to the fact that even then
these two phenomena, outwardly not very similar, the
burning of wood and the change produced by heating met-
als, were already classed together.

The name of "calces" (Latin calx = lime) for burnt
metals, which up to about 1600 was used along with
"cineres," and after that exclusively, is due to the Arabian
alchemists, and suggests an analogy with the burning of
chalk, the burnt metal being produced from the metal by
the same process as quick-lime from chalk, namely, by
heating. All through the Middle Ages the idea was re-
tained that what occurs when substances burn with flame,
and when metals are changed to calces, is of essentially
the same nature and must therefore be explained by the
same cause. For many centuries sulphur was looked upon
as the principle of combustibility and metals which could
be "burnt" — i.e., calcined — owed this to the common pres-
ence in them of sulphur (Freund). "Ubi ignis et calor, ibi
sulphur," summed up this view. Becher's 'terra pinguis'
had much in common with the fire of the schoolmen and
the sulphur of Abertus Magnus and Paracelsus. The scope
of the phenomena to which this explanation of combustion
applied was extended by Stahl, and the theory of the phe-
nomena of combustion and other analogous processes
which were to be explained by the assumption of the hypo-
thetical phlogiston was the point round which chemists
in general gravitated during the eighteenth century; until
the appearance of Lavoisier the phlogiston theory received
the assent of most investigators.

Georg Ernst Stahl, born at Anspach in 1660, devoted
himself to the study of medicine and acquired, first at Jena
and later on at Halle — to which university he had been
called as professor of medicine and chemistry in 1693 — the
reputation of a distinguished physician and academic

THE PHLOGISTIC .PERIOD PROPER 103

teacher. When he was appointed physician to the king in
1716, he removed to Berlin, where he successfully strove
for the extension of chemical knowledge until his death in
1734. He investigated chemical problems in the true scien-
tific spirit ; himself guided by the ardent desire to discover
the truth, he was able to draw around him pupils animated
by a similar purpose. The most eminent among the Berlin
chemists of the succeeding generation studied under him.

Even in his own lifetime the doctrines which he taught,
together with a number of valuable detached observations,
were widely disseminated by means of his writings and
especially by his lectures, the later of which were published
by several of his pupils. Stahl, however, exercised his
greatest influence both upon his contemporaries and upon
the succeeding generation by his phlogiston theory, which
eclipsed all his other chemical work.

Phlogiston was defined by Stahl as "materia aut prin-
cipium ignis, non ipse ignis," and was conceived to be 'ka
very subtle matter, capable of penetrating the most dense
substances; it neither burns, nor glows, nor is visible; it
is agitated by an igneous motion ('igneo motu'), and it is
capable of communicating its motion to material particles
apt to receive it. The particles when endued with this
rapid motion constitute visible fire. . . . The igneous
motion is 'gyratorius seu vorticillaris.' . . . Heat is an
intestine motion of the particles of matter."

Phlogiston was a new name for an old principle. We
know that the idea of the existence of a subtle fire innate
in matter has pervaded physical philosophy from the earli-
est times. Phlogiston was, as Rodwell notes, another name
for the 'pure fire' of Zoroaster ; the cctekvekov itvp of Zeno ;
the 'subtilis ignis' of Lucretius ; the 'elemental fire,' 'astral
fire,' 'sulphur,' or 'sulphureous principle' of the chemists;
the 'calor cselestis' of Cardanus; the 'sideric sulphur' of
Paracelsus; the 'materia cselestis' of Descartes, and the
'terra inflammabilis' of Becher. The functions of this entity
had been varied by different thinkers, almost as much as

104 CHEMISTRY

its name, until Descartes gave them accurate definition.
The theory of phlogiston was the theory of the 'Materia
Cselestis' extended in a chemical direction. Phlogistic
chemistry was Cartesian chemistry. Descartes defined the
physical functions of the 'Materia Caelestis,' while Becher
and Stahl defined its chemical functions and applied them
to the explanation of diverse chemical phenomena.
Throughout the writings of Becher and Stahl we find a
sprinkling of Cartesianism; they did not, however, adopt
the system in its entirety, but appear to have discarded the
second and third elements, and adopted the first as the
parent of their own system.

The theory of phlogiston was essentially and completely
a syncretistic theory. It was built up, as Rodwell observes,
of 'idola theatri/ collected from various sources, and these
were cemented together by the particular 'idola specus' of
Becher and Stahl. In this process of syncretism the merit
of these men lay ; their fault was a too hasty generalization.
In that stage of chemistry syncretism was inevitable ; in-
deed, all theories are more or less tinctured by it, with the
exception of those which emanate from a new mode of
experimenting, such, for example, as KirchhofFs theory
of the constitution of the sun. A theory proceeds by slow
evolution until it dominates or is destroyed, and fE was thus
with the theory of phlogiston.

Arising under the most favorable conditions, it attained
full development, became most cardinal, most sovereign,
and then fell. For twenty-eight years it was looking a
half- formed thing through the mists of chemistry; for
thirty-four years it was growing in strength and proclaim-
ing its dynasty; for fifty-four years it was dominant, and
it was fully ten years yielding up the ghost. Becher and
Stahl were the prophets of a new mode of chemical
thought, essentially classificatory, systematic, and syncre-
tistic. In their day chemistry was at the commencement
of a period of transition, and they bridged the gap which
existed between empirical chemistry and modern chemis-

THE PHLOGISTIC PERIOD PROPER 105

try. They did not collect the materials for the structure —
they did not altogether construct it, but they designed it,
and helped in the work of building. Albeit a bad bridge,
and built upon shifting sands, yet it was a channel of
escape from mystic science, and many passed over to take
refuge on the other side.

To Stahl, however, belongs the merit of grouping to-
gether the phenomena of oxidation and reduction, as we
now term these, albeit by the aid of a false hypothesis.
The addition of phlogiston is equivalent to reduction and
its withdrawal or escape to oxidation. The analogy be-
tween respiration and the decomposition of animal matters
on the one hand and combustion on the other did not
escape Stahl, who likewise assigned the chief role in these
processes to phlogiston.

The value of his theory lay therefore in the interpreta-
tion which it afforded of a variety of processes from one
common point of view. The simplicity of this explanation
blinded both himself and the generation which followed
him to such a degree that they left unnoticed all the glar-
ing contradictions between many actual facts and the
phlogistic doctrine. Notwithstanding this, however, the
latter was not an obstacle to the development of chemistry,
considering that chemists like Black, Cavendish, Marg-
graf, Scheele, Bergman, and Priestley, who so greatly
extended the science by their wide-reaching discoveries,
were phlogistonists in the full sense of the word.

Stahl's two most famous contemporaries were Friedrich
Hoffmann and Hermann Boerhaave. Hoffmann, born at
Halle in 1660, after acquiring a thoro knowledge of medi-
cine, mathematics and the natural sciences, practised first
as a physician and then became professor of the science
of medicine in Halle, where he ultimately died in 1742,
after an interregnum spent in Berlin. His most important
work was done in medicine, and in pharmaceutical and
analytical chemistry. He combated with success the iatro-

io6 CHEMISTRY

chemical doctrines of Sylvius and Tachenius, which still
held their ground with many physicians, exposing their
absurdities and showing to what nonsensical deductions
such exaggerations led.

Hoffmann's views on combustion were very similar to
those of »Stahl. With respect to the calcination of the
metals and the reduction of their oxides, however, he ex-
pressed opinions which approximate to those held at the
present day, believing, as he did, that metallic 'calces' con-
tained a 'sal acidum' in addition to a metal, the former of
which escaped when the 'calces' were reduced. This as-
sumption did away with the similarity between combustion
and calcination; these phenomena became indeed rather
opposed to one another thereby, and with this the special
use of the phlogiston theory vanished. Hoffmann was a
very voluminous author, and his collected works in six
volumes and five supplements, entitled 'Opera Omnia Phys-
ico-medica' (1740-1760), show clearness of style and pre-
cision of expression. Gmelin in his 'Geschichte der
Chemie' enumerates 122 chemical treatises by Hoffmann.

Hermann Boerhaave was born at Voorhout, near Ley-
den, in 1668, where he received his education and became
professor of medicine and afterward of chemistry and
botany. The thirty-six years of his residence there were
the most brilliant in the history of this university. Look-
ing at his chemical work alone, he is found distinguished
in the main as a teacher and for his skill in interpreting
chemical facts and the clearness of his theoretical views.
He exposed the errors of the iatro-chemists and recognised
chemistry as a distinct science.

He also showed the falsity of the views held by the
alchemists. He spoke only of things tested and observed
by himself, and spared neither pains nor time to have his
observations correct. For instance, the alchemists main-
tained that mercury could be fixed in the form of a fire-
proof metal, without the addition of any other substance.
Boerhaave kept mercury at a somewhat raised tempera-

THE PHLOGISTIC PERIOD PROPER 107

ture in an open vessel for fifteen years without noting any
change. So, too, when heated higher in a closed vessel
for six months no change could be discovered. This con-
vinced him that the fixing of#mercury was an impossibility.
The alchemists said also that if* mercury was repeatedly
distilled, a more volatile essence with peculiar properties
could be obtained. Boerhaave carried out this distillation
five hundred times without securing the essence. And so
he tested other of their peculiar notions and prescribed
methods without obtaining the results promised; and as
the methods were still credited in some quarters, he did
good service in disproving them, and won for himself the
reputation of being a most excellent and painstaking
worker.

His lectures were published first in the 'surreptitious
edition/ Tnstitutiones et Experimenta Chemiae' (1724) and
afterward corrected by him under the title 'Elementa
Chemise' (1732). Eleven editions and translations were
published in Germany, France, and England.

Boerhaave appears to have concurred in the phlogiston
theory in many points. At least he expressed no opinions
contrary to Stahl's fundamental views, altho he did not
agree in regarding the 'calces' of the metals as the earthy
elements of these latter.

The influence of Stahl's doctrine manifested itself more
immediately in Germany, where it received the almost
unequivocal support of chemists, Berlin remaining the
center point of this theory. Among the men who upheld
and endeavored to propagate it, Marggraf was the most
active.

Kaspar Neumann ("born 1683) and Johann Theodor
Eller (born 1689), contemporaries of Stahl, were also
active adherents of the doctrine in Berlin. Both of them,
as professors at the Medico-Chirurgical Institute, were
in a high degree active in maintaining and disseminating
a knowledge of chemistry. Their own observations were,
however, of little importance; Neumann made the first

108 CHEMISTRY

accurate observation of the acid obtained from ants; and
the views of Eller were chiefly upon subjects of medical
physiology, and are full of crude speculations. Stahl's
pupil, Johann Heinrich Pott (born 1692), improved chem-
istry by many valuable observations, but he was unfor-
tunate in his explanation of these. He regarded boracic
acid, for instance — a substance which he had himself in-
vestigated carefully — as consisting of copper vitriol and
borax. The results which he achieved were not, as von
Meyer notes, at all commensurate with his untiring per-
severance, which he showed, among other ways, in his
endeavors to prepare porcelain. Altho an adherent of
the phlogistic doctrine, Pott did not bring forward any-
thing new in its favor; with regard to the nature of
phlogiston itself, he could only express the opinion that
it was "a variety of sulphur." A notable achievement as-
sociated with his name was a wide extension of the method
of dry analysis. His 'Chymische Untersuchungen' was
published in Berlin in three parts in 1757.

Neumann's pupil, Marggraf, was the last of the well-
known German chemists of the phlogiston period. An-
dreas Sigismund Marggraf was born at Berlin in 1709,
and proved a most able experimenter; indeed, it is for his
many isolated discoveries that he is remembered rather
than for any influence exerted on the general trend of
chemical philosophy. One of the most lasting benefits
owed to him is the introduction of the microscope as an
aid in laboratory work. The occasion was noteworthy.
A paper appeared in the memoirs of the Berlin Academy
for 1745, in which Marggraf stated that small crystals
of sugar might be seen with'the aid of a microscope upon
the finely divided and desiccated roots of the carrot and
beetroot. He further stated that this sugar could be ex-
tracted by lixiviation with hot alcohol, and added that
mere compression of carrot or beet would yield a sac-
charine liquid, from which the sugar might readily be
extracted. These observations remained unnoticed, un-

THE PHLOGISTIC PERIOD PROPER 109

til the continental blockade of France in 1806 urged its
people to find some substitute for their imported sugar.

Of prime importance was Marggrafs observations on
phosphoric acid, whose principal physical and chemical
properties he accurately described. He obtained this acid
by burning ordinary phosphorus in the air, and dissolving
the resulting "fleurs de phosphore" in water; also by
heating phosphorus with concentrated nitric acid. Marg-
grafs work on the composition of gypsum was remark-
able; he had noticed that potassium sulphate on heating
with charcoal emitted the pungent smell of burning sul-
phur, and as this also occurred when gypsum or heavy
spar was substituted for the potassium salt, they too must
be compounds of sulphuric acid. One should not forget
his introduction of potassium ferrocyanide as a reagent
for iron, nor his separation of microcosmic salt from
urine; he remarked that it was this salt which contained
the phosphorus.

With great talent for observation Marggraf united the
gift of deducing what were generally sound conclusions
from his work. In one point, however, Marggraf, like all
phlogistonists, was not in a position to do this; altho he
had himself proved that phosphorus increases in weight
by conversion into phosphoric acid, he could not free him-
self from the idea that phlogiston escaped during this
process of combustion. And he could never be brought
to see that this conception was an erroneous one, altho
the anti-phlogistic doctrine was brought out several years
before his death. Marggrafs papers are, as mentioned,
almost all contained in the 'Memoirs' of the Berlin Acad-
emy; most of them were published from 1761-1767 in twov
volumes, under the title 'Chymische Schriften.' A French
edition appeared in 1762.

In France, the principal exponents of chemistry during
the eighteenth century, until the downfall of the phlogistic
system, were Geoffroy, Duhamel du Monceau, Rouelle and
Peter Joseph Macquer.

no CHEMISTRY

Stephen Franqois Geoff roy (the elder, to distinguish him
from his less celebrated younger brother, Claude Joseph,
whose work was chiefly pharmaceutico-chemical) was
born in Paris in 1672, and helped for some time in his
father's apothecary shop; he gave himself up, however,
to chemical and medical studies, and labored with great
success as professor of medicine in the Jardin des Plantes
from the year 1712 until his death in 1731. Geoff roy
became well known throughout the scientific world by
his researches upon chemical affinity; his Tables des
Rapports' (tables of affinity), in which the results of his
most important observations are collected, exercized a
great influence upon the doctrine of affinity. His theo-
retical views were less idoneous — e.g., he looked upon the
iron found in the ashes of plants as having been pro-
duced artificially during the process of ignition.

Geoffroy's views on combustion were in principle those
of Stahl, though he expressed himself in the nomencla-
ture of the earlier period; yet there was much promise in
his conviction that the different 'calces' were radically
different bodies.

A real service was rendered by him by the energy with
which he attacked alchemistic frauds, subjecting these
as he did to critical examination in the memoir 'Des Su-
percheries concernant la Pierre Philosophale/ presented
to the French Academy. Geoffroy's treatises were pub-
lished partly in the 'Memoirs of the French Academy,'
and partly in the 'Philosophical Transactions.' His long-
celebrated work, 'Tractatus de Materia Medica,' shows
that he regarded chemistry as a sister science and an
invaluable aid to medicine.

Henri Louis Duhamel du Monceau (born 1700, died
1781), of the school of Lemery and Geoffroy, spent his
life in Paris, where his versatility gained for him a high
reputation. His sterling work was not by any means
in pure chemistry alone, but also in physics, meteorology,

THE PHLOGISTIC PERIOD PROPER in

physiology, botany, and particularly in chemistry as ap-
plied to agriculture.

Duhamel's great achievement was the differentiation of
the two alkalis, soda and potash. The composition of
ordinary salt had hitherto eluded research. Stahl, it is
true, believed one constituent to be an alkali, and an alkali
quite different from potash, if one might judge by differ-
ences in the crystalline form and solubilities of their re-
spective salts. There was a vagueness about his work,
however, and it had met with little recognition. Duhamel
published a paper in 1736 on sea salt which put the matter
beyond question. In it he first showed that the base of
salt was not an earth, for the addition of potash caused
no precipitation, then that its several salts all differed
essentially from those of potash corresponding. He laid
stress, too, on the fact that the further one moves from
the sea, the less the quantity of the new base and the
greater the quantity of potash in the surrounding vegeta-
tion. Subsequently, while describing minutely the differ-
ences between the analogous salts of these bases, Duha-
mel mentioned the yellow and violet colorations which
they respectively give to a colorless flame.

While Duhamel worked mainly as an academician, Guil-
laume Francois Rouelle (born 1703, died 1770) was occu-
pied in teaching at the Jardin des Plantes, and some of
his pupils, particularly Lavoisier and Proust, attained the
highest eminence. At the same time he was also busy
as an investigator, as many admirable observations and
conclusions drawn from the latter show. Rouelle fixed
the meaning of the term "salt" (in the 'Memoirs' of the
Academy for 1745) from a far more general point of
view than van Helmont or Tachenius had done. The
composition of a substance alone was sufficient to tell
him whether it belonged to the class of salts or not. Salts
were produced by the combination of acids of every kind
with the most various bases; and in addition to neutral
salts, he drew a distinction between acid and basic ones.

ii2 CHEMISTRY

With views so lucid as these, Rouelle was far ahead of
his contemporaries.

Rouelle's "Cours de Chimie," according to Hoefer, ex-
ists only in manuscript.

The last of the French chemists of renown to adhere
to the phlogistic theory was Pierre Joseph Macquer, who
was born at Paris in 1718. He became a member of the
French Academy at the age of twenty-seven. Excellent
opportunity for work was afforded him by his position as
professor at the Jardin des Plantes, and his methods of re-
search were more like those of the present. He deter-
mined the solubility of various salts in alcohol, and used
this as a means of separating them from one another.
Some of his researches were on potassium arseniate, and
on the coloring matter of Berlin blue. The later he iden-
tified with phlogiston because it was destroyed on heating.
He was the author of several text-books, "Elemens de
Chymie Theorique" (1749) and "Elemens de Chymie
Pratique" (1751), which were highly thought of; but his
chief work was his "Dictionnaire de Chymie," which ap-
peared first in 1766. This was the first dictionary of
chemistry, and it was enlarged three times, and translated
into English, German, Italian and Danish. Macquer died
in 1784. All his life he remained a phlogistonist, and did
all that he could to reconcile the continually augmenting
dissidences between theory and facts; he paid no attention
to proportions by weight, for it was only in this way that
he could maintain the phlogistic hypothesis. And even
although it was proved to be erroneous and untenable
several years before his death, he was still unable to relin-
quish it.

During the eighteenth century many distinguished
chemists flourished in Great Britain and Sweden, all of
vvnom were adherents to the phlogiston theory of Stahl,
and this notwithstanding the fact that it was their inves-
tigations, particularly those of Black, Cavendish, Priest-

THE PHLOGISTIC PERIOD PROPER 113

ley, Scheele, and Bergman, which destroyed the founda-
tions of this theory.

Black was born near Bordeaux in 1728, and died in
Edinburgh in 1799. His father, a wine-merchant, was
originally a native of Belfast, being descended from a
Scotch family which had been settled there for some
time. Black's original thesis for his degree was entitled
'Experiments upon Magnesia Alba, Quicklime, and other
Alcaline Substances.' It was published in 1755, and was
reprinted in 1777 and 17G2. During the ten years he was
Professor of Medicine at the University of Glasgow he
began and made great progress with his well-known re-
searches on the heat of fusion of ice, and the heat of
vaporization of water, or, as he termed them, the "latent
heats" of water and of steam.

The carbonates of the alkaline earths were before
Black's time regarded as simple substances; and it was
also supposed that when limestone was burnt fire-stuff
was taken up, and that this went over into potashes or
soda when these were causticized by means of lime. Black,
on the other hand, showed by his investigations that when
limestone (carbonate of lime) or "Magnesia alba" was
calcined, something escaped which caused a loss of weight
and which was identical with van Helmont's "gas sylves-
tre." This gas — which he termed "fixed air" on account
of its being held bound by caustic alkalies, lime, etc. — he
proved to be also present in the mild alkalies; and these
latter became caustic when deprived of their carbonic
acid by lime or magnesia. In this research methods are
met with which have the imprint of a new departure.
That Black devoted great attention to the proportions by
weight of the compounds which entered into the reaction
is seen in all his investigations; and it is thus easy to un-
derstand how he gave up the phlogiston theory and con-
curred in the doctrine of Lavoisier when the correct ex-
planation of combustion and similar processes became
possible through the discovery of oxygen.

114 CHEMISTRY

Cavendish, the distinguished co-worker and fellow coun-
tryman of Black, was born at Nice in 1731, two years be-
fore Priestley; but, notwithstanding his brilliant circum-
stances, he lived the life of a recluse, devoting himself
entirely to the furtherance of his beloved science. He died
in 1810. His most important work was the discovery of
hydrogen, which he called "inflammable air." This he dis-
tinguished from the "fixed air" of Black, concluding that
this "inflammable air" was the unaltered phlogiston of the
metals. He was the first to attempt to determine the
specific gravity of the gases. He showed that lime car-
bonate was held in solution in water by dissolved fixed air
or carbonic acid. He proved in his experiments on air
that when hydrogen was burned water was formed, thus
really determining the composition of water, tho he did
not recognize this fact. This led to a sharp controversy
as to the phlogistication of the air or atmosphere, and in
the hands of that great interpreter of results, Lavoisier,
did much to clear up and advance chemical theory.

The opposition of Cavendish to the antiphlogistic doc-
trine, which he helped to found by his own investigations,
can only be explained by the fact that he did not take the
proportions by weight in the processes of combustion into
due consideration, but interpreted the latter in a manner
which appeared to him sufficiently convincing, viz., by
regarding hydrogen, "inflammable air," as identical with
phlogiston.

In addition to this Cavendish showed a wonderful ex-
actitude in his researches upon gases, whose specific grav-
ities and volume-ratios in chemical reactions he estab-
lished. With what ingenuity he thought out and carried
through physical experiments is well illustrated in his
work on the specific heats of metals, and in his attempt —
the first one which was successful — to determine the spe-
cific gravity of the earth. Another instance will be fresh
in the memory of most readers, viz., Cavendish's suspicion,
from the results of his own experiments on the combina-

THE PHLOGISTIC PERIOD PROPER 115

tion of oxygen and nitrogen, that there was possibly still
another gas present in the air in small quantity (argon).
When this marvelous versatility is considered and the
thoro mathematical training that Cavendish had gone
through is remembered, the wonder seems great that he
laid too little stress upon proportions by weight in chemi-
cal reactions.

Joseph Priestley was born at Fieldheads, near Leeds,
in 1733, and received his education at a public school and
at an academy of the Dissenters. His studies were theo-
logical in character, and he became a dissenting minister.
He was not a success in this work, becoming extremely
unpopular even with his own sect. He also conducted
a school, but was in very needy circumstances. He was
able, however, to buy a few books and some instruments,
including a small air-pump, an electrical machine, etc.,
and was tireless in his work, training himself and his
scholars in natural science. Meeting Franklin in London,
he was attracted to the study of electricity, and wrote a
history of electricity. This, together with some new ex-
periments on electricity performed by him, won some out-
side reputation and his election as Fellow of the Royal
Society.

He moved to Leeds, settling near a brewery. This gave
him opportunity for examining the "fixed air" discovered
by Black, and which had been shown to be one of the prod-
ucts of fermentation. He collected this gas from the
vats, and performed many experiments with it. Moving
away from the brewery, he had to prepare the "fixed air"
for himself; and this led to his devising the simple and
useful pneumatic trough. In the heated times of the French
Revolution, his church and dwelling-house were mobbed
and burned, his library and apparatus destroyed, and he
himself escaped with difficulty to London, and finally took
refuge in America, where he settled in Pennsylvania. In
this country he pursued his scientific experiments, dis-
covering carbon monoxide. He died in retirement in the

n6 CHEMISTRY

year 1804. One French historian, Henri Gautier, states in
his "Essai sur l'histoire de la Chimie" that Priestley
"sought an asylum among the Indians, and eventually he
and his entire family died by poison !"

Priestley was a brilliant investigator, performing many
most striking experiments. He was, however, neither
thoro nor very careful, and was lacking in the scientific
acumen needed for the proper interpretation of his re-
sults. It was upon the gases that his most valuable work
was done; his invention of the pneumatic trough enabling
him not only to discover new gases, but to investigate the
properties of many already partially known. He consid-
ered that "More is owing to what we call chance . . .
than to any proper design or preconceived theory in this
business," and shows how large a share this element of
chance had in his discovery of the new gas, oxygen.

His method of experimenting is well illustrated by his
own account of his discovery of oxygen (1774) : "Having
procured a (burning) lens, I proceeded with great alacrity
to examine, by the help of it, what kind of air a great
variety of substances would yield, putting them into ves-
sels filled with quicksilver, and kept inverted in a basin of
the same. After a variety of other experiments, I endeav-
ored to extract air from 'mercurius calcinatus per se,'
and I presently found that, by means of this lens, air was
expelled from it very readily. Having got about three or
four times as much as the bulk of my materials, I admitted
water to it, and found that it was not imbibed by it. But
what surprised me more than I can well express, was
that a candle burned in this air with a remarkably vigor-
ous flame. I was utterly at a loss how to account for it."
His experiments showed him that this air "had all the
properties of common air, only in much greater perfec-
tion"; and he called it "dephlogisticated air," regarding it
simply as very pure ordinary air. In 1843, Cuvier en-
deavored to show that the French chemist Bayen preceded
Priestley in the discovery of oxygen. Bayen, however, in

THE PHLOGISTIC PERIOD PROPER 117

reducing "precipitate per se," noted only the metal and
entirely disregarded the escaping gas.

He seems to have looked upon all gases as easily
changeable, one into the other, at least in the first period
of his work. Many experiments were made by him on the
action of the various gases known to him upon animals
and plants. He would place a mouse in a jar of the gas,
and notice the effect upon its breathing and general life
processes. Plants were grown in similar jars, and the
result upon the growth noted. He showed that air which
had become noxious through breathing or the burning of
a candle could be restored to its original condition by
growing a plant in it. This, he said, was due to the im-
pregnation with phlogiston in the first case, and its re-
moval in the second. "It is very probable," he wrote,
"that the injury which is continually done to the atmos-
phere by the respiration of such a number of animals
as breathe it, and the putrefaction of such vast masses,
both of vegetable and animal substances exposed to it,
is, in part at least, repaired by the vegetable creation."
He was unable to explain how this was accomplished.

He held that all combustible bodies contained hydro-
gen. This was, in his view, phlogiston. The metals con-
tained it, and their "calces," or oxides, were simply the
metals deprived of hydrogen. Thus, he showed that when
iron oxide was heated in hydrogen gas the hydrogen was
absorbed and metallic iron formed. Rich iron slag or cin-
der was, in his opinion, iron with some hydrogen retained.
To prove this, it was mixed with the carbonates of the al-
kaline earths and heated strongly. This gave him an in-
flammable gas, and all inflammable gases were hydrogen
in a more or less impure condition, acording to his belief.

That water could be impregnated with carbon dioxide
was found out by him, and its use in disease suggested,)
Nitrogen dioxide and carbon monoxide were discovered
by him, but his greatest discovery was that of oxygen gas.
He examined sulphur dioxide, hydrochloric acid, and am-

n8 CHEMISTRY

monia in the gaseous form. These are only the most im-
portant of his discoveries. Inaccurate in his experiments,
he was decidedly weak as a theorizer. He was a firm be-
liever in the phlogiston theory, and endeavored to explain
the various phenomena noted by him by means of it.

The important works of Priestley are the following:
'Directions for impregnating Water with Fixed Air in
order to communicate to it the peculiar spirit and virtues
of Pyrmont Water, and other mineral waters of a similar
nature' (1772); 'Philosophical Empiricism' (1775); 'Ex-
periments and Observations on Different Kinds of Air'
(1774-1779) ; 'Experiments and Observations relating to
various branches of Natural Philosophy with a continua-
tion of the Observations on Air' (1779-1786); and 'Ex-
periments on the Generation of Air from Water' (1793).

Coetaneously with the three last-mentioned British
chemists, two eminent investigators, Torbern Olaf Berg-
man and Karl Wilhelm Scheele, were supporting the phlo-
gistic theory in Sweden, but their brilliant discoveries
and observations only served so deeply to undermine it
that its dispensation was inevitable. Bergman had acquired
such a wide knowledge of the natural sciences that he
taught with eminent success as professor of physics, min-
eralogy and chemistry at Upsala. He was born in the
year 1735, and died at the early age of forty-nine, undoubt-
edly from the effects of overwork upon a weak constitu-
tion. His chief services to chemistry, to which from 1767
he mainly devoted himself, were in the domain of analysis,
which he treated systematically and enriched by valuable
methods.

Bergman's system of wet analysis first took form dur-
ing an investigation of natural waters; but he later made
it embrace the examination of minerals in general, fusing
such of these as were insoluble in hydrochloric acid with
carbonate of potash. Bergman laid great stress on the
analytical value of the blowpipe, between whose inner and
outer flame he discriminated ; and he endeavored to extend

THE PHLOGISTIC PERIOD PRPOER 119

the use of such reagents as soda, borax, and microcosmic
salt, substances whose value had been demonstrated
by the mineralogist Cronstedt. It is to Bergman's
pupil Gahn that the introduction of cobalt solution as a
reagent is owed, and the substitution of platinum wire for
the gold or silver used hitherto. Up to this time, reduc-
tion to the metallic state had been regarded as a necessary
precedent to the quantitative estimation of metals in com-
bination. Bergman now introduced the revolutionary
method of combining them in stable salts of known com-
position, and from the weight of these calculating the
metallic content.

Bergman's analyses were not very accurate, yet they en-
joyed the widest popularity; on the other hand, his Ger-
man contemporary, Carl Friedrich Wenzel, found little
consideration, tho his method was similar, and his re-
sults more fortunate. Meanwhile, the number of chemists
who applied themselves to the quantitative side of phe-
nomena was steadily increasing, an indication of the straits
to which the phlogiston theory had been reduced. Yet
at this eleventh hour Bergman set to work to determine
the relative quantities of phlogiston in metals. Believing
that metals only dissolve after conversion into their
'calces/ he ascertained those weights of various metals
which precipitated the same weight of some other in solu-
tion, surrendering their phlogiston to its 'calx'; these
weights, to his mind, contained the same quantity of
phlogiston.

He knew well how to render his chemical experiences
useful for the definition and classification of minerals, and
thereby laid the foundation of mineralogical chemistry
and chemical geology. The current views upon chemical
affinity gained through him precision and clearness;
the scientific character of chemistry was materially raised
by such observations, and a general survey of chemical
processes rendered much easier. His papers appeared
originally in the "Memoirs" of the Academies of Stock-

120 CHEMISTRY

holm and Upsala; later on they were collected together
and published in six volumes in 1779-1790, under the title
'Opuscula Physica et Chemica.' This Latin edition was
translated into English in 1784-1791.

Carl Wilhelm Scheele was born in 1742 in Stralsund, the
capital of Swedish Pomerania, where his father was a
merchant and a burgess. He was the seventh of eleven
children. After receiving his education, partly in a pri-
vate school, partly in the public school ("gymnasium")
at Stralsund, he was apprenticed at the age of fourteen
to the apothecary Bauch in Gothenburg. In those days
an apothecary was in large measure a manufacturer as
well as a retailer of drugs. He had to prepare his medi-
cines in a pure state from very impure materials, as well
as to mix them in order to carry out prescriptions; and,
indeed, he himself often, as sometimes happens still, ven-
tured to prescribe in mild cases. Scheele's master taught
him such methods, and in addition instructed him in the
use of the chemical symbols in vogue at that date; these
he afterward freely employed in his manuscripts, and
this renders them exceedingly difficult to decipher.

Restricted almost entirely to several old text-books, to-
gether with the fairly good chemical inventory of Bauch's
shop, Scheele, by constant experimenting, acquired such a
knowledge of things chemical that, by the time he went to
Malmo (in 1765) he had gained more experience than the
majority of the chemists of the time, altho he was yet only
an apprentice. At Malmo and also in Stockholm (1768-
1770) and Upsala (1770-1775), he increased his knowl-
edge of the most important branches of chemistry with-
out, however, becoming so well known at the time as he
deserved.

It was only when, as stated by Nordenskiold, through
Gahn he came into close relation with Bergman — a con-
nection which began in a misunderstanding and coolness,
but which developed into a friendship — that Scheele con-
tinued to gain steadily in reputation. After taking over

THE PHLOGISTIC PERIOD PROPER 121

the pharmacy at Koping in 1775, he was able to devote
himself more closely to scientific work, and with still
more brilliant results. The records of his researches
followed one another rapidly in the 'Transactions of the
Stockholm Academy, into which he had been received as
"Studiosus Pharmacia?" in 1775. In 1777 he published
the results of his investigation on air, oxygen, combustion
and respiration at Upsala and Leipzig in a volume entitled
'Chemische Abhandlung von der Luft und dem Feuer' ('A
Chemical Essay on Air and Fire'). After his early death
at barely forty-four years of age, his collected works were
published in two volumes in German by S. F. Hermbstadt
(Berlin, 1793), under the title 'Sammtliche Physische und
Chemische Werke.' The Latin edition by Schaefer had
appeared four years previous.

Altho the results of his principal investigations will be
discussed further on, it is important to mention here that
to Scheele is due the first knowledge of chlorine and of
the individuality of manganese and baryta. He was an in-
dependent discoverer of oxygen, ammonia and hydro-
chloric acid gas. He discovered also hydrofluoric, nitro-
sulphonic, molybdic, tungstic, and arsenic acids among
the inorganic acids; and oxalic, citric, tartaric, malic and
mucic among the organic acids. He isolated glycerin and
milk-sugar; determined the nature of microcosmic salt,
borax, and 'Prussian blue,' and prepared hydrocyanic
acid. He demonstrated that plumbago is nothing but car-
bon associated with more or less iron, and that the black
powder left on solution of cast iron in mineral acids is
esentially the same substance. He ascertained the chemi-
cal nature of sulphuretted hydrogen, discovered arsen-
uretted hydrogen, and the green arsenical pigment which
is associated with his name. He found new processes for
preparing gallic acid, ether, powder of algaroth, phos-
phorus, calomel, and 'magnesia alba.' His services to
quantitative chemistry included the discovery of ferrous
ammonium sulphate, and of the methods still in use for

122 CHEMISTRY

the analytical separation of iron and manganese, and for
the decomposition of mineral silicates by fusion with al-
kaline carbonates.

The greatest work of the life of Scheele, however, was
his memoir on 'Air and Fire,' which appeared in 1777, and
which, on account of its relations to the chemical theory
of that time, attracted universal attention, and was trans-
lated into English, French and German. The chief part
of the experimental material for this work, as is proved
by the correspondence and laboratory journals published
in 1892 by Nordenskiold, was collected partly in Malmo
and Stockholm — that is, before the autumn of 1770, and
partly during the earlier portion of his stay in Upsala —
that is, prior to 1773. These dates are important in view
of Scheele's relations as a discoverer to Priestley and
Lavoisier. A number of circumstances, and more espe-
cially the dilatoriness of the publisher Swederus, retarded
the appearance of the book. From the letters to Gahn it
appears that the manuscript was sent to the printer to-
ward the close of 1775, but nearly two years elapsed be-
fore the work was made public. Scheele, in several of his
letters, laments over the delay.

In August, 1776, he wrote to Bergman: "I have thought
for some time back, and I am now more than ever con-
vinced, that the greater number of my laborious experi-
ments on fire will be repeated, possibly in a somewhat dif-
ferent manner, by others, and that their work will be pub-
lished sooner than my own, which is concerned also with
air. It will then be said that my experiments are taken,
it may be in a slightly altered form, from their writings.
I have to thank Swederus for all this." However, no im-
putation of plagiarism was ever brought against Scheele.
The wThole conduct of his life was proof indeed against
even a suspicion of unfair dealing. He was exceedingly
unselfish and veracious. To quote Thorpe, "With all
Priestley's candor and sense of rectitude, he had Caven-
dish's indifference to fame and his contempt for notoriety*

THE PHLOGISTIC PERIOD PROPER 123

It can hardly be doubted, however, that had Scheele's
work appeared in 1775 he himself would have occupied a
still higher position in the estimation of his contempo-
raries, and that it would not have been left to posterity to
assign him his true place in the history of scientific dis-
covery." He further expresses the following apprecia-
tion:

"It is impossible to read this, or indeed any other of
Scheele's memoirs, without being impressed by his ex-
traordinary insight, which at times amounted almost to
divination, and by the way in which he instinctively seizes
on what is essential and steers his way among the rocks
and shoals of contradictory and conflicting observations.

"It is, perhaps, idle to speculate on the causes which
prevented Scheele from recognising the full significance
of his work. It may be that from the lack of mathemati-
cal training the quantitative aspects of chemistry had few
attractions for him, but it is equally probable that the pe-
culiar character of his inquiries may have been determined
by the circumstances of his position, by his poverty, and by
the want of the refined and costly apparatus needed for
quantitative research. But surmises, as Scheele himself
said, cannot determine anything with certainty. It must be
admitted that he was wanting in the faculty of coordina-
tion, grasp of principle, and power of generalization that
so strikingly characterize Lavoisier; and his greatest in-
vestigation, while it testifies to his genius as an experimen-
talist, reveals, no less clearly, his weakness as a theorist.
But when every legitimate deduction has been made,
Scheele's work, with all its shortcomings and limitations,
stamps him as the greatest chemical discoverer of his age.
His story constitutes, indeed, one of the most striking ex-
amples of what may be achieved by the diligent cultivation
of a single natural gift."

CHAPTER VIII

DEVELOPMENT OF SPECIAL BRANCHES DURING THE PHLOGIS-
TIC PERIOD

Altho the services of the chemists whose investiga-
tions did most toward building up the chemistry of gases
have been referred to, yet the influence of this work in
shaping chemistry was so great that discussion of pneu-
matic chemistry and its relations to the phlogistic theory,
in more detail, is necessary. Boyle, ingenious though ho
was, was unable to fathom the mystery of atmospheric air.
His views regarding it are succinctly stated by him in his
'Memoirs for a General History of the Air,' and in the
same work he sums up the views of the ancients. His
words are :

"The Schools teach the air to be a warm and moisfl
element, and consequently a simple and homogeneous
body. Many modern philosophers have, indeed, justly
given up this elementary purity in the air, yet few
seem to think it a body so greatly compounded as it
really appears to be. The atmosphere, they allow, is
not absolutely pure, but with them it differs from true
and simple air only as turbid water from clear. Our
atmosphere, in my opinion, consists not wholly of
purer aether, or subtile matter which is diffused
thro' the universe, but in great number of numberless
exhalations of the terraqueous globe ; and the various
materials that go to compose it, with perhaps some
substantial emanations from the celestial bodies, make
124

DEVELOPMENT OF SPECIAL BRANCHES 125

up together, not a bare indetermined feculancy, but a
confused aggregate of different effluvia."

His researches, however, show a marked advance over
those of van Helmont in the mode in which he collected
gases and worked with them ; at the same time neither he
nor his contemporaries felt quite sure whether carbonic
acid and hydrogen, whose characteristic properties he
was acquainted with, differed materially from atmospheric
air. In fact, the idea that gases were simply atmos-
pheric air with various admixtures, had become fixed in
the minds of chemists. The experimentalist Stephen
Hales, for example, discovered gases and prepared them
in a more or less pure state, but had no theory to guide
him, and concluded that it was possessed of "a chaotic na-
ture," since he failed to recognise his gases as different
kinds of matter, but regarded them all as modified air.

Black's account of "fixed air" and its properties is the
first example of a clear and logical series of experimental
researches, where nothing was taken for granted, but
everything was made the subject of careful quantitative
measurement. It was not long since Hales had announced
air to be a chaotic mixture of effluvia. Black showed that
common air contains a small amount of "fixed air," and
that "fixed air" must be considered as a fluid differing in
many of its properties from common air, especially in its
being absorbed by quicklime and by alkalies. It must be
remembered that at that time carbon was not recognised
as an element; and hence, tho Black knew that "fixed
air" was a product of the combustion of charcoal, he did
not attribute it to the union of carbon with oxygen.

Black held that the change from chalk to lime consists
only in the withdrawal of "fixed air," and he adduced in
proof the changes in weight accompanying the change
from chalk to lime and back again :

"A piece of perfect quicklime, made from two drams
of chalk, and which weighed one dram and eight grains,
was reduced to a very fine powder, and thrown into a fil-

126 CHEMISTRY

trated mixture of an ounce of a fixed alkaline salt and two
ounces of water. After a slight digestion, the powder,
being well washed and dried, weighed one dram and fifty-
eight grains. It was similar in every trial to a fine powder
of ordinary chalk."

The changes referred to are:

chalk heated = lime r+ fixed air
CaC03= CaO + CO*
lime + fixed alkali = chalk + caustic alkali
CaO + K2C03=CaC03 + K20

The methods of collecting gases had improved consider-
ably since the times of Hales. Air was ascertained to be a
fluid capable of measurement, which possessed weight, and
which could be transferred from one vessel to another,
just like all other fluids. The apparatus which Black,
Priestley, Bergman, and Scheele employed, and those
which we use at the present time, gradually developed
themselves from that of Hales. Joseph Priestley was the
first to describe the collection of gases over mercury, and
by this means he succeeded in discovering gaseous am-
monia, hydrochloric acid, silicon fluoride, and sulphurous
acid — gases which had been overlooked so long as water
was employed in the collecting vessels. As mentioned be-
fore, Scheele is now known to have anticipated Priestley
in the isolation of some of these gases, as well as of nitric
oxide and sulphuretted hydrogen (hydrogen sulphide).
These investigations, along with the recognition of Caven-
dish that hydrogen is a peculiar gas, and the supplemental
researches of Bergman and Black on carbonic acid, are
to be emphasized as being particularly noteworthy, since
they helped to do away with many misconceptions and
errors.

The discovery of so many gaseous substances of such
different character naturally roused the chemical world.
The properties of each gas were carefully studied; and,
after Mayow's researches, and especially after the more

DEVELOPMENT OF SPECIAL BRANCHES 127

exact determinations conducted by Cavendish, the density
was taken as the criterion of one gas differing from an-
other and from atmospheric air. Due attention was also
given to the greater or lesser absorption of gases by
water, as a distinct test for some of them; Bergman, for
instance, determined with fair accuracy the solubility of
carbonic acid in water. However, the exact composition
of gaseous bodies remained unknown during this period,
great uncertainty prevailing even about the simplest of
them, until Lavoisier had pronounced his opinion as to the
elementary nature of oxygen and hydrogen. But this
could not be otherwise, so long as phlogiston was believed
to be present in most gases. Hydrogen was thought to be
identical with phlogiston by many chemists, soon after the
middle of the eighteenth century, Cavendish and Richard
Kirwan setting the precedent for this ; others looked upon
coal as being rich in phlogiston, if not as the latter itself;
and often confused opinions were expressed concerning
the composition of carbonic acid, carbonic oxide, nitric
oxide, sulphurous acid, sulphuretted hydrogen, and other
gases, these opinions being made to conform with the
views of the phlogistic doctrine prevalent at that time.

Of greater importance than these views upon the con-
stitution of the gases just named were the long unsettled
questions, "Is atmospheric air a simple or a compound
body, and — if the latter — what are its constituents or in-
gredients?" These questions were solved experimentally
by chemists belonging to the phlogistic era, more par-
ticularly by Scheele and Priestley; but it was left to La-
voisier to interpret their observations correctly.

The first observation which assisted in overthrowing the
old assumption of air being a simple substance, was the
deportment of an enclosed volume to a burning body
and to metals heated in it. The alchemists had asserted
that when a substance is burned in the air it is separated
or analyzed into things simpler than itself. The acute
Boyle had said the process is not necessarily a simplifica-

128 CHEMISTRY

tion; it may be, and certainly sometimes is, the formation
of something more complicated than the original sub-
stance, and when this happens, the process often consists
in the fixation of 'the matter of fire' by the burning sub-
stance. He was led by his investigations in this direction
to the assumption that one ingredient of the atmosphere
was necessary to respiration and combustion, and that the
increase in weight during the calcination of metals was
due to a ponderable firestufT. He remarked that,

"It will not be irrational to conjecture that multitudes of
these fiery corpuscles, getting in at the pores of the glass,
may associate themselves with the parts of the mixt body
whereon they work, and with them constitute new kinds
of compound bodies, according as the shape, size and other
affections of the parts of the dissipated body happen to
dispose them. ... I have been induced to think that the
particles of an open fire working upon some bodies may
really associate themselves therewith; and add to the
quantity." (Boyle, 'The Sceptical Chymist,' 1661.)

He was unable to isolate this ingredient, however.

Stahl paid no attention to the change in weight result-
ing from calcination — a position which was taken also by
many later phlogistonists, who either regarded such a
change as accidental or advanced crude explanations of it.
Johannes Juncker, for example, pointed out that the
metallic 'calces' were denser than the metals, and con-
sequently heavier — decidedly an incorrect statement, as
Boyle had already demonstrated in certain cases that the
'calces' were specifically lighter than their corresponding
metals. Equally ridiculous was the assumption that the
phlogiston which escaped in calcination possessed a nega-
tive weight, and therefore that the end product was the
heavier.

In 1630 Jean Rey published a series of essays entitled:
'Essays of Jean Rey, Doctor of Medicine, on the Re-
searches of the Cause owing to which Tin and Lead in-
crease in Weight when they are calcined.'

DEVELOPMENT OF SPECIAL BRANCHES 129

"Now I have made the preparations, nay, laid the
foundations for my answer to the question of the
sieur Brun, which is, that having placed two pounds
six ounces of fine English tin in an iron vessel and
heated it strongly on an open furnace for the space of
six hours with continual agitation and without add-
ing anything to it, he recovered two pounds, thirteen
ounces of a white calx; which filled him at first with
amazement, and with a desire to know whence
the seven ounces of surplus had come. And to in-
crease the difficulty, I say that it is necessary to en-
quire not only whence these seven ounces have come,
but besides them what has replaced the loss of weight
which occurred necessarily from the increase of vol-
ume of the tin on its conversion into calx, and from
the loss of the vapours and exhalations which were
given off. To this question, then, I respond and sus-
tain proudly, resting on the foundations already laid,
That this increase in weight comes from the air,
which in the vessel has been rendered denser, heavier,
and in some measure adhesive, by the vehement and
long-continued heat of the furnace: which air mixes
with the calx [frequent agitation aiding] and becomes
attached to its most minute particles: not otherwise
than water makes heavier sand which you throw into
it and agitate, by moistening it and adhering to the
smallest of its grains/ "
The manner in which Rey arrives at his answer is not
by any direct experiments on calcination, but rather by
experiments and the reference to experiments of a purely
physical nature, such as the discussion of the causes, like
change of volume, which can, and of those, like heat,
which cannot, produce change of weight. Thus he lays
a sound foundation for his method, which is one of elimi-
nation, showing that none of the causes to which it had
been usual to ascribe the observed increase in weight
could be considered legitimate ; that it could not be due to

130 CHEMISTRY

the giving up of heat of negative gravity, nor to the ab-
sorption of fire matter of positive weight, not to an in-
crease in density, not to the absorption of soot or of any-
thing else from the materials of the containing vessels.^
And so none is left unchallenged of all the possible modes
of explanation save that of the fixation of the air.

Consequently, his conclusion that calcination of a metal
probably consists in the fixation of particles of air by the
metal, does not amount to a proof.

Mayow assumed that a "spiritus igno-aereus" brought
about combustion. According to him, the substance that
is being calcined lays hold of this particular constituent of
the air, which, however, he failed to isolate. Neverthe-
less, he approached closely to the correct interpretation
of the phenomena in question, the real solution of which
was brought forth after oxygen and nitrogen had been
prepared with success.

Nitrogen was first isolated by Scheele, but Daniel Ruth-
erford, who discovered it independently in 1772, preceded
Scheele in publication. Rutherford removed the oxygen
from ordinary air by combustibles such as charcoal, phos-
phorus, or a candle; and having got rid of the carbon
dioxide, in those cases when it was formed, by alkali or
lime, he obtained a residue, now known as nitrogen. His
view of the nature of this gas, in the phlogistic language
of the time, was that the burning bodies had given up
some of their 'phlogistic material' to the air, which was
thus altered. Nitrogen was 'phlogisticated air,' even
tho incombustible; hydrogen, too, was phlogisticated
air, but air produced by the union of pure phlogiston with
atmospheric air. The step taken by Rutherford, under
Black's guidance, was an advance, though not a great one,
in the development of the theory of the true nature of
air. It followed from Scheele's, as well as Rutherford's,
observations that this new gas, which was a non-supporter
of either respiration or combustion, must be one of the in-

DEVELOPMENT OF SPECIAL BRANCHES 131

gredients of atmospheric air. The other was discovered
by Scheele and Priestley.

It should be mentioned here that passages in early
works suggest the possibility of a much earlier acquaint-
ance with oxygen gas. Hoefer, in his 'Histoire de la
Chimie' (Vol. II, p. 271), claims to discover traces of a
knowledge of oxygen gas in the writings of Zosimus, a
Greek writer on alchemy, who lived in the third or fourth
centuries. In a manuscript preserved in the National
Library of Paris, entitled 'Zosimus the Panopolitan on the
Sacred Art of making Gold and Silver/ this passage oc-
curs: "Take the soul of the copper, which is borne upon
the water of mercury, and disengage an aeriform body
('soma pneumatikon')." Hoefer states that here we have
indications of the production of a gaseous body by means
of a red substance (the soul of copper) which floats on
the surface of liquid mercury; if this substance is red
oxide of mercury, the "aeriform body" must have been
oxygen.

Moreover, in Campbell's 'Hermippus Redivivus; or the
Sage's Triumph over Old Age and the Grave/ which was
published in London in 1749, the following statement oc-
curs: "I could mention another preparation from the vital
part of the air itself, which is a great secret among these
philosophers, and is perhaps the 'white dove' so often
mentioned in the writings of Philalethes, of which, thus
much is certain, that when the air is once despoiled of this
principle, it is no longer fit for animal respiration, and it
was by a contrivance of this kind that the famous Corne-
lius Drebbel made that liquor, which supplied the place of
air in the machine he contrived for carrying on a kind
of submarine navigation. This medicine, which is, as I
have said, extracted from the air, is whiter than the snow,
colder than ice, and so volatile that if a quantity of a nut-
meg be exposed to the air it is absorbed thereby in the
space of a few seconds." As Bolton has remarked, this
passage refers "in an unmistakable manner to the prepara-

132 CHEMISTRY

tion of oxygen and its property of supporting life." Dreb-
bel (1572-1634) appears to have rowed in a boat under
water in the Thames River for a distance of about eight
miles, and his employment of compressed oxygen gas, if it
may be so interpreted, must have been about the begin-
ning of the seventeenth century.

Scheele prepared oxygen by heating black oxide of
manganese with sulphuric or arsenic acid, and also from
nitrates, and from the oxides of mercury and silver, and
noted its characteristics very clearly. Priestley, who also
observed the gas at about the same time, without, however,
recognizing its peculiar nature, first isolated it for certain
on August 1st, 1774, by heating red oxide of mercury; and
as he published his results earlier than Scheele, he has
generally been regarded as the first discoverer of oxygen.
Both observed that this gas was capable of supporting
combustion and respiration in an intensified degree.
Priestley named it "dephlogisticated air," and Scheele at
first 'aer vitriolicus/ later 'fire-air,' and also 'life air.'

The discovery of oxygen enabled both Scheele and
Priestley to recognize air as being a mixture of two kinds
of gas; Priestley calls nitrogen Thlogisticated air/ and
Scheele terms it 'spent air.' Priestley employed salt-
peter gas (nitric oxide) as an absorbent for oxygen, while
Scheele made use of phosphorus, hydrate of protoxide of
iron, mixtures of iron and sulphur, and moist iron filings.
Both made the important observation that, upon burning
a candle in an enclosed volume of air, exactly as much
''fixed air" (carbon dioxide) was generated as oxygen
had vanished.

Notwithstanding all this, they did not arrive at the cor-
rect explanation of combustion, respiration and calcina-
tion, whose analogy to one another they clearly saw.

The breathing of animals and the burning of substances
were supposed to load the atmosphere with phlogiston.
Priestley spoke of the atmosphere as being constantly "viti-
ated," "rendered noxious," "depraved," or "corrupted" by

DEVELOPMENT OF SPECIAL BRANCHES 133

processes of respiration and combustion; he called those
processes whereby the atmosphere is restored to its origi-
nal condition (or "depurated," as he said), "dephlogis-
ticating processes." As he had obtained his "dephlogis-
ticated air" by heating the calx of mercury, Priestley was
forced to suppose that the calcination of mercury in the
air must be a more complex occurrence than merely the
expulsion of phlogiston from the mercury; for, if the
process consisted only in the expulsion of phlogiston, how
could heating what remained produce exceedingly pure
ordinary air? It seemed necessary to suppose that not
only was phlogiston expelled from mercury during cal-
cination, but that the mercury also imbibed some portion,
and that the purest portion, of the surrounding air. Priest-
ley did not, however, go so far as this ; he was content to
suppose that in some way, which he did not explain, the
process of calcination resulted in the loss of phlogiston by
the mercury, and the gain, by the dephlogisticated mer-
cury, of the property of yielding exceedingly pure or de-
phlogisticated air when it was heated very strongly.

Consequently, the path distinctly indicated by his own
observations was left for another to tread. It was Lavoi-
sier who was destined to do this, as he easily threw aside
the trivial phlogistic misconceptions that he cherished at
the commencement of his scientific career. The others,
indeed, supported a contradictory explanation of combus-
tion and analogous processes, in order to remain loyal to
the phlogistic doctrine. But that it was Priestley and
Scheele, who, by their exhaustive investigations on oxygen
and the part which it played in the processes mentioned,
furnished the experimental material for the correct inter-
pretation of these, and not Lavoisier, is beyond all ques-
tion. It remained for the latter, however, to give the
correct explanation of combustion, calcination and similar
processes.

Among the treatises on air which appeared during this
period, other than those mentioned, were Bohn's 'Medita-

134 CHEMISTRY

tiones physico-chymicae de aeris in sublunaria inflexir
(1685) ; Arbuthnot's 'An Essay concerning the Effects
of Air on Human Bodies' (1751) ; and Cavallo's 'A Trea-
tise on the Nature and properties of Air and other per-
manently elastic Fluids' (1781).

In order to appreciate the advances which the chemical
ideas of the Phlogistic Period showed upon those of the
periods already discussed and to understand the connec-
tion which exists between the theoretical views of the
phlogistonists and those of the chemists of the Modern
Period, it is necessary to become acquainted with their
views regarding elements, chemical compounds and chemi-
cal affinity.

Boyle's definition of an element — that it is any substance
which cannot be further decomposed — was one of great
significance for the whole of natural science. He also con-
sidered that the elements attainable by chemical investi-
gation were not the ultimate constituents of matter. Nev-
ertheless, his contemporaries and successors, failing to ap-
preciate these views, exhibit a tendency to revert to the
alchemistic elements and even to those of Aristotle. For
instance, Lefevre, author of a treatise on theoretical chem-
istry, and Lemery classified earth and water with the three
elements of Basilius Valentinus and Paracelsus, while
Becher held to those three under other names — the "veri-
fiable," the "inflammable," and the "mercurial" earths —
and added water to the list.

According to Stahl's views, sulphur consists of sul-
phuric acid and phlogiston; and a metal, of its metallic
"calx" (oxide) and phlogiston. Therefore, the phlogis-
tonists assumed that all products of calcination and com-
bustion (acids and oxides) were elements, in which class
of substances they also classed phlogiston itself. These
erroneous assumptions kept back a knowledge of the true
elements, and only after it was clearly demonstrated that
instead of the escape of phlogiston, the absorption of oxy-

DEVELOPMENT OF SPECIAL BRANCHES 135

gen must be allowed, and in place of the assimilation of
phlogiston the removal of oxygen, did that extraordinary-
genius Lavoisier bring light into the confusion which pre-
vailed by his brilliant ideas and observations.

A better understanding of the composition of substances
was gained by analytical chemistry, which was gradually
developing during this period; but altho certain constitu-
ents of compounds could be identified and distinguished
from one another, yet the proportions by weight in which
substances combined were not considered, and conse-
quently the real development of the term ''chemical com-
pound" was reserved for the period of quantitative chem-
istry.

The chemists of the Phlogistic Period were forced to
draw their conclusions concerning the composition of sub-
stances from analogy, notwithstanding which fact, how-
ever, several contributed materially to an insight into the
nature of chemical compounds. Robert Boyle, for ex-
ample, recognised the dissimilarity of such substances to
elements, while he, Mayow, and Boerhaave stated that
the characteristic properties of substances which combine
chemically disappear after such combination, notwith-
standing the fact that they are still present in the com-
pound formed. Acids, salts and oxides ("calces") were,
however, regarded as being of similar composition; and,
until it was recognised that salts were produced by the
combination of acids with bases — an achievement of this
period — the term "salt" was applied promiscuously. Stahl,
for instance, applied the term to acids and alkalies as well
as to salts proper, and considered that salts were made up
of an earth and water.

In 1745, Rouelle rendered a great service to the study
of salts and the diffusion of knowledge respecting this
class of compounds in his attractive lectures. He defined
salts as the products of the union of acids with bases, and
distinguished normal, acid and basic salts, and showed

136 CHEMISTRY

their action on vegetable dyes. Yet he confounded many
salts with acids, and could not throw off the old idea that
the vitriols and other metallic salts consisted of metal and
acid. Bergman demonstrated the falsity of this assump-
tion when he proved that it is the metallic calces and not
the metals themselves which combine with acids to form
salts. After the time of Rouelle, solubility in water and
taste were no longer regarded as characteristics of salts,
inasmuch as he classed several insoluble compounds among
them.

Important work on chemical affinity was contributed
during this period, notwithstanding the fact that the old
assumption that those bodies have an affinity for one an-
other which have something in common — that affinity is
governed by this, remained a mental fixture with specula-
tive chemists even into the eighteenth century. The term
"affinitas," used by Albertus Magnus to express this idea,
presupposed the similarity of substances which interact
chemically. As is generally the case, another idea evolved
itself, and has lived until the present time, side by side
with the first, to which it is exactly contradictory; this
considers union as dependent upon contrast, on polar dif-
ference, on an effort to fill up a want. This contrary idea
found a devoted exponent in Boerhaave, who maintained
that it is unlike substances which show the greatest tend-
ency to combine with each other. His influence secured
the general adoption of his views by chemists.

After the time of Glauber, and particularly after that of
Boyle, much attention was paid to the processes in which
the forces of affinity show themselves. Cases of so-called
simple elective affinity ("attractio electiva simplex," a
term which originated with Bergman) were interpreted
correctly by both the chemists just named, and also by
Mayow; for instance, the expulsion of ammonia from sal-
miac by fixed alkali, by the assumption that the attraction

DEVELOPMENT OF SPECIAL BRANCHES 137

of the latter for hydrochloric acid was greater than that
of this acid for the ammonia (fluchtiges Laugensalz).
Observations of this kind on the expulsion or precipitation
of bases or acids from salts, by substances endowed with
stronger powers of affinity, soon caused chemists to solve
the order in which analogous bodies were separated from
their compounds by others. The observations on the pre-
cipitation of metals and on the expulsion of various acids
from salts by means of sulphuric and nitric acids, among
others, may have tended in an especial degree to make
clear the different strengths of affinity in analogous bodies.

Stahl, the founder of the phlogistic theory, contributed
important work on affinity. He attempted (1720) to
classify the effects of affinity by arranging similar
substances in a series in the order in which they
expel one another from a compound : "The following me-
chanical experiment may serve as an example. Dissolve
silver in nitric acid, it will take up the silver and appear
as a light liquor; into the clear and transparent liquor
throw thin strips of copper foil, the nitric acid will dissolve
these and will drop the silver in the form of a powder;
pour this clear green solution on to lead foil, it will be at-
tacked and the copper previously dissolved will be dropped ;
pour off the clear solution and pour it on to zinc, it will
dissolve the zinc and allow the previously dissolved lead
to drop; into this clear solution put chalk, it will be dis-
solved and the zinc dropped; then to this solution add
spirits of urine, which will combine with it, releasing the
chalk; and finally drop in lye, the solution will take it up
and allow the volatile salt to go."

Geoffroy used such a classification as the basis of his
tables of affinities, 'Tables des Rapports' (1718), an ar-
rangement destined to become very popular. The princi-
ple was to arrange similar substances so that the one fol-
lowing was always expelled by the one preceding from
combination with the one heading the list. When thus

138 CHEMISTRY

represented, Stahl's example just quoted becomes: Nitric
Acid : potash, ammonia, lime, zinc, lead, copper, silver.

But yet another most important discovery concerning the
action of affinity is due to Stahl. He recognised the fact
that a reaction occurring at one temperature in one direc-
tion could be reversed at another temperature; that at or-
dinary temperatures calomel is decomposed by silver,
while under the influence of heat silver chloride is de-
composed by mercury. Such reciprocal reactions led to
the suggestion to prepare tables of affinity for medium and
high temperatures, both for wet and dry (i.e., fusion) re-
actions. Bergman made the attempt in 1775 to work out
this proposal of Baume's by investigating the mutual be-
havior of a very large number of compounds, with the re-
sult that the doctrine of chemical affinity was materially
advanced, in so far as this was possible by such empirical
work.

Bergman's work on affinity was published in his 'Opus-
cula physica et chemica.' His views may be summarized as
follows: (1) There is a sequence in the magnitude of the
elective affinities of a series of substances toward one with
which they all combine, and this is manifested by the fact
that the one possessing the greater affinity, expels from the
combination the one possessing the lesser affinity. (2) This
order is constant under each of the two different conditions
of interaction in the moist and dry way respectively, but
differs under these two distinct conditions. (3) The sub-
stance of lesser affinity is completely expelled by that of
greater affinity, subject, however, to the possibility that the
mass of the expelling substance may have to be very much
greater than that required for simply replacing the ex-
pelled substance in the combination. (4) It is impossible
to reverse such a reaction.

The following abstract from the table of Bergman on
affinity will indicate the principles upon which it was
based :

DEVELOPMENT OF SPECIAL BRANCHES 139

Sulphuric acid.

Wet way.
Baryta

Potash and soda
Ammonia
Alumina
Zinc oxide
Iron oxide
Lead oxide
Copper oxide
Mercury oxide
Silver oxide

Dry way.
Phlogiston
Baryta
Potash
Soda
Lime
Magnesia
Metallic oxides
Ammonia
Alumina

Potash.

Wet way.
Sulphuric acid
Nitric acid
Hydrochloric acid
Phosphoric acid
Arsenic acid
Acetic acid
Boracic acid
Sulphuric acid
Carbonic acid

Dry way.
Phosphoric acid
Boracic acid
Arsenic acid
Sulphuric acid
Nitric acid
Hydrochloric acid
Acetic acid

In the table the order from top to bottom gives the rela-
tive displacing power. Thus in combination with sul-
phuric acid, where the action takes place in aqueous solu-
tions, baryta is represented as displacing any of the sub-
stances placed below it, and so with potash, ammonia,
etc. Where the dry substances are subjected to heat, the
order is changed somewhat.

It was recognised then that the strength of affinity
varied with the temperature. This is the "attractio elec-
tiva simplex" of Bergman. He recognised also an "at-

140 CHEMISTRY

tractio electiva duplex." Macquer made use of the term
"affinitas reciproca," where two bodies seemed to have
nearly the same strength of affinity for a third substance,
one replacing the other under slightly changed conditions
— a partial recognition of the fact that affinity is dependent
upon other conditions besides temperature.

This should have sufficed to show the unreliable char-
acter of the various tables offered, but chemists were slow
to give them up. Nor did they value at its true worth the
remarkable work of Berthollet in the next period and his
conclusion that the action of affinity was proportional to
the masses of the interacting substances. This, properly
understood, entirely did away with all such tables, for a
body with lesser affinity could displace one of greater, pro-
vided it was present in a sufficiently greater mass.

Among the chemists of this period who wrote treatises
on the subject of affinity may be mentioned Limbourg
(1761), Marherr (1762), Wenzel (1777), Keir (1778),
Wiegleb (1780), Elliot (1786), Guyton de Morveau
(1786), and Schmieder (1799).

The growth of applied chemistry during the Phlogistic
Period is next to be recorded. This division of the science
was especially assisted in its development by that indis-
pensable branch, analytical chemistry, in which notable
advances were made.

Qualitative chemical analysis, which had its beginnings
in the iatro-chemical period, was developed by the investi-
gations of Boyle, Hoffmann, Marggraf, Scheele and Berg-
man. The first named introduced the word "analysis" for
those chemical reactions by which individual substances
could be detected in the presence of one another, and con-
siderably advanced the analytical examination of sub-
stances in the wet way. He employed reagents to distin-
guish the important classes of compounds, and the sys-
tematic use of plant juices as indicators for the detection
of acids, bases and neutral substances originated with him.
For this purpose, he used the coloring matters in the juices

DEVELOPMENT OF SPECIAL BRANCHES 141

of litmus, violets and corn-flowers. Among the other re-
agents he introduced may be mentioned solutions of cal-
cium and silver salts for the recognition of sulphuric and
hydrochloric acids respectively, infusions of oak leaves or
gall nuts for the detection of solutions of the salts of iron,
and volatile alkaline salt for the recognition of copper
salts. He recognised ammonia by the white cloud that re-
sulted when it came in contact with fuming acids, such as
hydrochloric or nitric acids.

Hoffmann busied himself in analytical chemistry mainly
with the investigation of mineral waters. He examined
many samples, and showed that they contained carbonic
acid, iron, common salt and salts of magnesia and lime. He
furnished valuable information as to the methods of test-
ing for these substances, and also indicated many charac-
teristics of mineral waters. The 'Tabelle iiber einige 40
Mineralwasser' was an important contribution by Carl A.
Hofmann (1789).

Marggraf, besides proving that gypsum consisted of
lime and sulphuric acid, and that the latter was also a
constituent of heavy spar, made use of the different colora-
tions which the salts of soda and potash impart to a flame
as a means for their recognition, and employed a solution
of prussiate of potash as a test for iron.

Scheele made many valuable observations in analytical
chemistry. He it was who perceived the difference be-
tween soluble and insoluble silicic acid, and effected the
separation of iron and manganese by acetic acid, in addi-
tion to independently observing the flame colorations of
salts of soda and potash, and explaining the difference be-
tween the inner and outer flames of the blowpipe, a piece
of apparatus which was introduced into chemistry by
Gahn, Cronstedt and Bergman. The latter was indebted
to Scheele for many observations, but was more systematic
than his contemporary. He suggested the use of subli-
mate, liver of sulphur, and sugar of lead as reagents; of
hydrochloric acid or carbonate of potash to open up ores;

142 CHEMISTRY

and of methods for the separation of salts and the estima-
tion of precipitates. The tests he employed for the recog-
nition of sulphuric, hydrosulphuric, carbonic, arsenious
and oxalic acids, and of lime, baryta and copper, are still
in use.

Bergman was, to quote von Meyer, "probably the first
to proceed on the principle that an element should not be
itself isolated and estimated according to its own weight,
but separated in the most convenient form as an insoluble
precipitate — e.g., lime earth as oxalate of lime, and sul-
phuric acid as sulphate of baryta," in the determination
of the weights of metallic precipitates. This procedure, in
conjunction with the endeavors of Marggraf, Homberg,
Scheele and Black, to take the proportions by weight into
account — in other words, to determine the quantity of a
substance or substances present in a solution — furnished
important preparatory work for the quantitative investiga-
tions of the next period.

In the analysis of gases, the most noteworthy work of
the period was done by Cavendish, who made a determina-
tion of the amount of oxygen in the air by exploding with
hydrogen. He found that the oxygen amounted on the
average to 20.85 per cent., a result which is only 0.05 per
cent, short of the mean as determined at the present day.
It was learned that carbonic acid and oxygen could be es-
timated volumetrically by the use of absorptives: caustic
potash was used for the absorption of the former, and
phosphorus for that of oxygen.

Mainly owing to the efforts of such investigators as
Boyle, Kunckel, Marggraf and Duhamel du Monceau,
technical chemistry made considerable progress during the
Phlogistic Period.

In metallurgy, correct explanations of many processes
were brought out, afltho in general it may be said that the
methods of extracting metals from their ores underwent
little improvement. In the manufacture of iron and steel,
however, some material changes were made as a result of

DEVELOPMENT OF SPECIAL BRANCHES 143

the investigations of Bergman, Gahn, Rinman and Rene
Reaumur. The latter's work, "L'Art de convertir le fer
forge en acier et i'art d'adoucir le fer fondu, ou de faire
des ouvrages de fer fondu aussi fin que de fer forge," pub-
lished in Paris in 1722, brought the author a pension of
12,000 francs from the Duke of Orleans, because of the
improvements it effected in the manufacture of cast iron
and steel. An account of Reaumur's method of softening
cast iron was also embodied in Home's 'Essays Concerning
Iron and Steel,' a work of useful observations published
in London in 1773. Duhamel improved the manufacture
of brass, and Marggraf introduced a more satisfactory
method of preparing zinc from calamine.

A valuable treatise by Kunckel on the ceramic art and
glass-making appeared in 1689. This work was entitled
'Ars vitraria experimentalis/ and contained Neri's 'Arte
vitraria/ with additions by Kunckel and others. After the
introduction of the importation of chinaware, many at-
tempts were made to imitate this true porcelain. In this,
Bottger (1685-1719) made the first advance in 1709, altho
it is now known that a porcelain of soft paste was made
at Florence as early as 1580. Bottger first made a red
ware, but eventually, by employing kaolin, he made a true
porcelain at Meissen. The process of manufacture re-
mained a secret, however, and it was not until it was solved
at Sevres in 1769 by the experimental work of Reaumur
and other chemists that the manufacture spread.

In England, porcelain appears to have been experimen-
tally manufactured at Fulham, by Dwight, as early as
1671 ; but it was not produced in quantity until about 1730,
when works were established at Bow. In this connection,
Higgins' 'Experiments and Observations made with the
view of Improving the Art of composing and applying
Calcareous Cements' (1780) should be mentioned. This
treatise contained the results of valuable experimental in-
vestigations on the induration and strength of cements.

Two works of great aid to the dyer — Macquer's 'L'Art de

144 CHEMISTRY

la teinture en soie' (1763), and Hellot's 'L'Art de la tein-
ture des laines et etoffes de laine' (1750, 1786) — in that
they contained speculations upon the manner in which
dyeing operations are carried out, appeared during this
period. Stahl, Hellot and Macquer divided dyes into two
classes, viz., those capable of being fixed on cloth without
the aid of mordants, and those requiring the use of such
agents, and in 1794, Bancroft distinguished these divisions
as adjective and substantive dyes. Prussian blue was dis-
covered by Diesbach in 1710.

Sulphuric acid, the manufacture of which constitutes
one of the most important branches of modern technical
chemistry owing to the great variety of purposes for which
it is required, was first manufactured on* a large scale by
a quack physician of the name of Ward, about the middle
of the eighteenth century. For this manufacture, he em-
ployed glass globes of about 40 to 50 gallons capacity; a
small amount of water having been poured into the globe,
a stoneware pot was introduced, and on this a red-hot iron
ladle was placed. A mixture of sulphur and saltpeter was
then thrown into this ladle, and the vessel was closed.
The vapors evolved were absorbed by the water, and sul-
phuric acid costing from is. 6d. to 2s. 6d. per pound was
obtained. Roebuck of Birmingham was the* first to sug-
gest the use of leaden chambers instead of glass globes.
These leaden chambers were set up in Birmingham in
1746, and were worked intermittently; the continuous
working of them is an achievement of the nineteenth cen-
tury.

The manufacture of fuming sulphuric acid was first car-
ried out at Nordhausen in the Harz, by heating roasted
green vitriol, but was subsequently removed to Bohemia.
Rouelle demonstrated that nitric acid could be concen-
trated by distillation with sulphuric acid. A number of
improvements were made in the manufacture of this acid
by Stahl and other chemists, but hydrochloric acid was not
prepared in large quantities, as it was not employed

DEVELOPMENT OF SPECIAL BRANCHES 145

technically. As early as 1670, an artist, Henry Schwan-
hard, prepared hydrofluoric acid for etching figures on
glass, and it is probable that his preparation was the same
as that known to some artists as a secret in 1721, and pub-
lished by Weygand in 1725.

The alkalies and their carbonates were obtained just as
in ancient times, viz., from the ashes of plants, incrusta-
tions on the soil, and carbonized tartar. However, it was
shown by Duhamel and other chemists that common salt
could be converted first into sulphate of soda, and finally
into carbonate of soda. A description of such a process
is contained in the 'Description de Divers Procedes pour
Extraire la Soude du Sel Marin,' published by the Tm-
primerie du Comite de Salut public' in 1795. Duhamel
also introduced suitable methods of preparing starch and
soap, and improved the processes of manufacturing sal
ammoniac and sugar. His 'L'Art de raffiner le sucre'
(1764) was held in high esteem in this period. Marg-
graf's discovery of cane sugar in the juice of the red beet
has been referred to; it only remains to say that it laid
the foundation for the now enormous and important beet
sugar industry.

The knowledge of the chemical elements and compounds
was enlarged to a remarkable degree in the Phlogistic
Period, and the discoveries made and facts learned after-
ward became of great technical importance. Six new ele-
ments— chlorine, phosphorus, manganese, cobalt, nickel
and platinum — were added to the ones already known.
Phosphorus was obtained by Brand, a Hamburg alchemist,
in 1669, by distilling the residue from evaporated urine;
he called it "cold fire,'*' and in 1671 Johann Elsholtz, of
Vienna, gave it the same name as the Bologna stone, or
"phosphor," which was discovered about 1603. The dis-
covery of phosphorus caused much excitement on account
of its properties, but its preparation was kept secret, and
it was only after many endeavors that Boyle and Kunckel

146 CHEMISTRY

discovered the method of obtaining it. The "phosphorus"
described by Balduinus in 1675 is thought to have been dry
calcium nitrate, while that discovered by Homberg in
1693 was an oxychloride of calcium. Kunckel, in several
treatises on phosphorus, gave an account of its discovery
and contributed to a better knowledge of the element.

The first account of metallic manganese was given in the
'De metallis dubiis' of Jacob Winterl and J. G. Kaim,
which was published in Vienna in 1770. Gahn, however,
is generally credited with its isolation, which he effected
in 1774. Cobalt was discovered by Brandt in 1742, and
the earliest full account of the metal is contained in
Johann Gesner's 'Historia cadmise fossilis metallicse sive
cobalti,' which appeared the next year. Nickel was first
prepared by Cronstedt in 1750. The observations of Arvid-
son on this interesting metal were published in 1775.

Platinum is first referred to in Don Antonio de Ulloa's
'Relacion historica del viage a la America Meridional'
(1748). William Watson, an English chemist, was the
first to examine the "Platina di Pinto," found in the Span-
ish West Indies by explorers, and his observations, along
with Brownrigg's experiments on the metal, were published
in the 'Philosophical Transactions' of the London Royal
Society in 1751. Watson's experiments were continued
by Lewis in 1755, Macquer in 1758, and Marggraf in 1761.
De Buffon asserted that platinum was an alloy of gold
and iron, and von Milly considered that it contained these
metals, together with mercury. Its elementary nature was
not established to the satisfaction of all until the next
period.

The knowledge of organic compounds was also con-
siderably extended, and new fields for organic chemistry
were opened up toward the close of the period. However,
the real composition of all organic compounds was not as-
certained until the time of Lavoisier.

Boyle investigated dry distillation, and proved that the

DEVELOPMENT OF SPECIAL BRANCHES 147

liquid obtained by the distillation of wood is not a simple
body, but that it contains, besides pyroligneous acid, an
indifferent body which may be separated by distillation
over burnt coral. The crude wood-spirit thereby procured
he termed "adiaphorous spirit." He also wrote on the
production and rectification of alcohol, a subject of fre-
quent investigation by the chemists who followed him.
Spirit of wine was prepared fairly pure, and was used
in analytical chemistry for the separation of various salts,
but confused opinions were held with respect to its forma-
tion in spirituous fermentation processes.

Attempts were made by Reaumur in 1733, and Mathurin
Brisson in 1768, to determine the amount of alcohol in
aqueous solutions containing it from its specific gravity.
An interesting treatise on wines, 'Ueber die Verfalschung
der Weine,' was written by Friedrich Cartheuser in 1779.
Frobenius (1730), Hoffmann, Pott, Antoine Baume
(1757), and Cadet de Gassicourt (1775) investigated ether
("spiritus vini vitriolatus"), but until 1800 it was be-
lieved to contain sulphur. A mixture of ether with alco-
hol, known as "Hoffmann's drops," and the compound
ethers were used officmally.

Scheele discovered, or first clearly distinguished, the
important organic acids, showing that grapes contained
one (tartaric acid) which differs from that found in
lemons (citric acid) ; that another (malic acid) occurred
in apples, and again a new one (oxalic acid) was detected
in wood-sorrel. The latter he prepared by the oxidation
of cane-sugar with nitric acid, and found that it differed
from the one obtained by treating milk sugar with nitric
acid (mucic acid). He also discovered lactic acid in sour
milk, uric acid in bladder stones, and prussic acid by de-
composing yellow prussiate of potash with sulphuric acid;
and improved the methods of preparing gallic and ben-
zoic acids. He showed that the latter forms a lime salt
freely soluble in cold water, and therefore may be readily
obtained by boiling gum benzoin with milk of lime, con-

148 CHEMISTRY

centrating the filtrate and separating the acid by means of
hydrochloric acid. On the other hand, he learned that
malic, tartaric and citric acids formed insoluble salts with
lime or lead oxide, by the aid of which substances they
might be separated from other bodies in the fruit. He
prepared the acids by decomposing their lime or lead salts
thus obtained with sulphuric acid.

Formic acid was discovered by Wray in 1760, and was
further investigated by Arfvidson and Cehrn in 1777. Its
resemblance to acetic acid, which was now prepared in a
pure form, was soon observed, and this produced some
confusion. Marggraf proved that they differed.

Oils and fats were frequently investigated, and Scheele
showed that they contained a common constituent, oelsiiss,
or the "sweet principle of oils." This is now known as
glycerin, or glycerol. Scheele stated that i* is related to
sugar, not only because of its taste, but also on account of
the fact that both substances yield oxalic acid in treat-
ment with nitric acid. The importance of this discovery
was not realized until a much later date.

Considerable progress was made during this period in
medical and pharmaceutical chemistry, and many new
medicines came into vogue. Among these were carbonate
of ammonia, sulphate of potash, magnesia alba and sul-
phate of magnesia.

Among the text-books which appeared may be mentioned
the following: the 'Manuductio ad chemiam pharmaceu-
ticam' of Rivinus (1690) ; Fick's 'Chymicorum in phar-
macopoeia Bateana et Londinensi explicatio' (1711); von
Ludolff's 'Die in der Medicin siegende Chemie' (1750), and
Baume's 'Elements de Pharmacie Theorique et Pratique'
(1762). The advances made in organic and medical
chemistry prepared the ground for physiological chemistry,
a branch which has been greatly developed in the most
recent period.

CHAPTER IX

LAVOISIER AND THE ANTIPHLOGISTIC CHEMISTRY

It has been seen how far the development of chemical
knowledge during the seventeenth century was influenced
by Stahl's phlogistic theory — that this theory exerted a de-
cided influence on the progress of chemistry, but that it
was too elastic to give exact definition to the tendency of
investigation. It had, however, done good work, since it
coordinated facts and developed unity of purpose, and
served admirably as a period of preparation for the scien-
tific experimental work of the era commencing with the
discovery of oxygen by Scheele and Priestley — the Mod-
ern Chemical Period. For twenty years following this
discovery a contest concerned mainly with the recognition
of the experimental method was pursued. It had to do
with the support of the method of observation under defi-
nite conditions as the foundation of all theoretic infer-
ences and views, and with the subduction of the prejudices
which had resulted from following the method which fos-
tered speculation and the adaptation of observations, as
far as possible, to the established system.

This short period of revolution (1774-1794) is rendered
radiant by the reforms of one of the most remarkable men
in the history of science, Lavoisier, who abolished old
prejudices and masterfully applied scientific principles to
the explanation of chemical phenomena. His combustion
theory supplanted the doctrine of phlogiston — a change,
it is true, that primarily only required the substitution of
149

150 CHEMISTRY

the words "addition of oxygen" for "withdrawal of phlo-
giston," but which eventually resulted in a complete trans-
formation of all ideas concerning combustion, calcination
and respiration, and consequently the views respecting
chemical composition — a displacement which culminated in
the conversion of the chemistry dominated by the dogma
of Stahl into the antiphlogistic system, the "New Chem-
istry."

The Phlogistic Theory was deposed by the Theory of
Oxygen, but, as Whewell has pointed out, "this circum-
stance must not lead us to overlook the really sound and
peimanent part of the opinions which the founders of the
phlogistic theory taught." In this connection, we must
not forget how much Lavoisier owed to his predecessors.
He sifted and collated the facts handed down to him by
the phlogistonists, and, mainly from the standpoint of the
physicist, gave correct explanations of many processes;
but he made no independent chemical discoveries, and is
honored not as a Scheele or Black, but as the founder of
a new system based on his comprehensive and correct ex-
planations of the observations of other investigators.
Consequently, it may be said that Gallic patriotic bias
prompted Wurtz to state in his "Histoire des Doctrines
Chimiques" that "La chimie est une science franchise" —
an assertion which was repeated twenty years later by
Jagnaux. Since, however, chemistry only took rank as a
science when quantitative work was made its basis, Lavoi-
sier must be given credit above all others in having di-
rected it into and along this road.

Antoine Laurent Lavoisier was born in Paris on the
26th of August, 1743. His father was wealthy and spared
no expense on his education. In his twenty-first year La-
voisier obtained a gold medal from the Academy of Sci-
ences for an essay on the most appropriate method of
lighting the streets of Paris, but it was some years before
he made definite choice of his subject. He published me-
moirs relating to geology and to mathematics, before the

LAVOISIER 151

fame of Black's and Priestley's discoveries reached him
and induced him to turn his attention to scientific chem-
istry.

By good business management he greatly added to his
property and became a man of wealth. He lived well, giv-
ing dinners which were famed for their excellence and
for the company gathered at them. This attracted atten-
tion to him and won for him some enemies whose influence
was felt in the storm gathering against all that smacked
of aristocracy. In addition, he was a f ermier-general ;
and tho he brought about some reforms, some of his meas-
ures proposed to the Government were exceedingly un-
popular, as, for instance, his plan for taxing Paris. Im-
peached under the Reign of Terror, he was condemned to
death, and was executed, together with twenty-eight other
fermiers-generaux, on the 8th of May, 1794.

In Lavoisier is seen a master mind, not only capable of
devising and conducting experiments, but mainly of assim-
ilating those of others, and deducing from them their cor-
rect significance. Altho his additions to the known
chemical compounds were few in number, and cannot, as
mentioned, be compared with those of Scheele or of
Priestley, yet his reasoning in disproof of the phlogistic
theory was so exact that it rapidly secured conviction,
and laid the foundation for the new chemistry of the quan-
titative era. Hitherto exclusive importance had been at-
tached to visible phenomena, but Lavoisier introduced a
more exhaustive investigation of chemical reactions and
the relations of quantity. The important work in which
he recognised and explained the part played by oxygen in
the process of combustion, calcination, and respiration
embodies the chief investigations of his life, however, and
in this lies his abiding service to science.

The earlier observations of Rey, Mayow, and others,
who had attributed the increase in weight of the metals
during their calcination to an absorption of air, contained
only the first germs of the true explanation of these proc-

152 CHEMISTRY

esses. From the year 1772 Lavoisier engaged in investi-
gations bearing upon this subject, the first results of
which he delivered in a sealed note to the French Academy
on November 1st of that year. This note was to the fol-
lowing effect:

"About eight days ago I discovered that sulphur, when
burned, instead of losing weight, gains weight; that is to
say, from one pound of sulphur much more than one
pound of vitriolic acid is produced, not counting the mois-
ture gained from the air. Phosphorus presents the same
phenomenon. This increase of weight is due to a great
quantity of air which becomes fixed during the combus-
tion, and which combines with the vapors. This discov-
ery, which I confirmed by experiments which I regard as
decisive, led me to think that what is observed in the
combustion of sulphur and phosphorus might likewise take
place with respect to all the bodies which augment in
weight by combustion and calcination; and I was per-
suaded that the gain of weight in calces of metals pro-
ceeded from the same cause. Experiment fully confirmed
my conjectures. I effected the reduction of litharge in
closed vessels with Hales' apparatus, and I observed that
at the moment of the passage of the calx into the metallic
state, there was a disengagement of air in considerable
quantity, and that this air formed a volume at least a
thousand times greater than that of the litharge employed.
As this discovery appears to me to be one of the most in-
teresting which has been made since the time of Stahl, I
thought it expedient to secure to myself the property, by
depositing the present note in the hands of the secretary
of the Academy, to remain secret till the period when I
shall publish my experiments. Lavoisier/'

He was, however, in the same position as Mayow had
been — that is, still in doubt as to which portion cf the air
caused this increase in weight, as to the air itself being a
mixture of gases, and especially as to the nature of the

LAVOISIER 153

process which occurred in the reduction of the litharge;
he felt inclined to regard the generated gas (carbonic
acid) as the fluid originally combined with the lead. This
uncertainty was brought about by his giving little atten-
tion to the qualitative side of the chemical reactions.

In 1774, after repeating these and similar investigations,
Lavoisier found his error with regard to the reduction of
litharge, and furnished more elaborate details of his obser-
vations, especially of the calcination of tin. He began by
considering the possible solutions of the problem, and then
investigated what changes really do occur, from which he
inferred the cause. To quote from his "CEuvres" :

"Thus then did I at the beginning reason with myself:
if the increase in the weight of metals calcined in closed
vessels is due, as Boyle had thought, to the addition of
the matter of the flame and the fire which penetrate the
pores of the glass and combine with the metals, then it fol-
lows that on introducing a known weight of metal into a
glass vessel and sealing this hermetically, determining the
weight exactly, and then proceeding to calcination by a
charcoal fire — just as Boyle had done — and then finally
after calcination, before opening it, again weighing the
same vessel, this weight must be found augmented by that
of the whole quantity of fire matter which had been in-
troduced during calcination. But if, said I to myself, the
increase in the weight of the metal calx is not due to the
addition of fire matter nor of any other extraneous matter,
but to the fixation of a portion of the air contained in the
vessel, the whole vessel after calcination must be no
heavier than before and must merely be partially void of
air, and the increase in the weight of the vessel will not
occur until after the air required has entered."

To test these theoretical considerations, Lavoisier se-
lected the calcination of lead and of tin in sealed retorts.
From two careful experiments with eight ounces of tin —
similar ones with lead were unsuccessful — Lavoisier found
that the increase in weight of the tin on cajcinatioa was

154 CHEMISTRY

practically identical with the weight of air which took the
place of that absorbed during calcination. His conclusions
were as follows:

"Summing up the results of the two experiments on tin
just described, it seems to me impossible not to draw the
following conclusions :

"First. In a given volume of air only a fixed quantity
of tin can be calcined.

"Secondly. This quantity is greater in a large retort
than in a small one.

"Thirdly. The hermetically sealed retorts, weighed be-
fore and after the calcination of the tin contained in them,
showed no difference of weight, which evidently proves
that the increase in weight of the metals arises neither
from the fire matter nor from any other matter extraneous
to the vessel.

"Fourthly. In all calcinations of the iin the increase in
weight of the metal is sufficiently nearly equal to the
weight of the air absorbed, to prove that the portion of
the air which combines with the metal during calcination
is of specific gravity approximately equal to that of at-
mospheric air."

Thus the problem he had undertaken had been solved by
Lavoisier. He had ascertained the cause of the increase
in the weight of metals on calcination and had found it
to be combination with a certain portion of the air. And
having proved before that sulphur and phosphorus on
burning also increase in weight and absorb a large vol-
ume of air, Lavoisier must at that stage, as Freund re-
marks, be supposed to have established that combustion
consists in combination with a portion of the atmospheric
air, whereby the increase in weight on combustion is ac-
counted for. However, he knew nothing as yet concerning
the nature of the portion of air absorbed. In the time
between the memoir on the calcination of tin and his next
contribution to the subject of combustion, falls Priestley's
discovery of a gas obtainable by the heating of red oxide

LAVOISIER

155

of mercury, the investigation of the properties of this
gas, and the recognition that it is a better supporter of
combustion than ordinary air; Lavoisier learned of this
new fact, and his next paper bears evidence of the manner
in which he was helped thereby.

This paper, which was written in 1775, was entitled "On
the Nature of the Principle which combines with Metals
during their Calcination, and which increases their
Weight." In this he described epxeriments showing that
when metallic "calces" are converted into metals by heat-

Fig. 18

-Lavoisier's Apparatus for the Calcination of
Mercury.

ing with charcoal, a quantity of fixed air is expelled; and
here for the first time he pointed out that " 'fixed air' is a
compound of carbon with the elastic fluid contained in the
'calx.' " He then described the preparation of oxygen by
Priestley's process of heating red oxide of mercury ("mer-
curius precipitatus per se"), and. showed that the red
oxide, when heated with charcoal, exhibited the properties
of a true "calx," inasmuch as metallic mercury was
formed and a large quantity of "fixed air" was produced.
In 1776, Lavoisier observed that the combustion product
of the diamond was composed of carbonic acid alone; and
in his next paper, which appeared the following year, he

i56 CHEMISTRY

dealt with the combustion of phosphorus ; he recapitulated
Rutherford's experiments, and showed that one-fifth of the
air disappeared, and that the residue, to which he gave the
name "mouffette atmospherique," is incapable of support-
ing combustion. As mentioned, Rutherford named this
residue "phlogisticated air," since he imagined it to have
absorbed phlogiston from the burning phosphorus;
Scheele, too, had made a similar experiment with a like
result. From these observations, Lavoisier concluded that
air consists of a mixture or compound of two gases, one
capable of absorption by burning bodies, the other inca-
pable of supporting combustion.

The results of these investigations, along with the ob-
servations of Scheele and Priestley, and a research on the
combustion of organic substances made in 1777, the prod-
ucts of which he showed to be water and carbonic acid,
enabled Lavoisier to enunciate his views on combustion
in a memoir published in 1778. The main points of this
combustion or oxidation theory are as follows:

(1) Substances burn only in pure air ('air eminem-
ment pur').

(2) This air is consumed in the combustion, and the
increase in weight of the substance burnt is equivalent to
the decrease in weight of the air.

(3) The combustible body is, as a rule, converted into
an acid by its combination with the pure air, but the
metals, on the other hand, into metallic 'calces/

Hence the mechanism of combustion according to La-
voisier is represented by:

Metal -f- oxygen = metal 'calx'
(simple) (complex)

Metal 'calx' — oxygen = metal
Carbon withdraws oxygen, forming fixed air

in direct contradiction to the phlogistic scheme:
Metal — phlogiston = metal 'calx'
(complex) (simple)

LAVOISIER 157

In 1783, there appeared a memoir by Lavoisier, entitled
"Reflections concerning Phlogiston." After explaining the
phenomena of combustion and reduction as combination
with oxygen or its separation, he proclaimed the non-ex-
istence of phlogiston, saying in part as follows :

"But if in chemistry everything can be satisfactorily
explained without the aid of phlogiston, it thereby becomes
eminently probable that such a principle does not exist,
that it is a hypothetical being, a gratuitous assumption,
and sound logic is opposed to unnecessary complication.
Perhaps I might have confined myself to these negative
proofs and remained content to show that the phenomena
can be better explained without phlogiston than by means
of it; but the time has come when I must speak out in
a more definite and formal manner concerning a view
which I consider an error fatal to chemistry, and which
appears to me to have considerably retarded progress by
the method of false reasoning it has engendered. All
these reflections prove what I have advanced, what it has
been my object to demonstrate, what I will repeat once
more, namely, that chemists have turned phlogiston into a
vague principle, one not rigorously defined, and which
consequently adapts itself to all the explanations for which
it may be required. Sometimes this principle has weight
and sometimes it has not; sometimes it is free fire and
sometimes it is fire combined with the earthly element;
sometimes it passes through the pores of vessels, some-
times these are impervious to it ; it explains both causticity
and non-causticity, transparency and opacity, colors and
their absence; it is a veritable Proteus, changing in form
at each instant."

It was in this year that his important memoir upon the
composition of water appeared, and it was this research
which removed the last obstacles with which the antiphlo-
gistic system had to contend.

James Watt, the Scotch inventor, was the first to state
distinctly that water is not an element, but that it is com-

158

CHEMISTRY

posed, weight for weight, of two other substances, one
of which he considered to be phlogiston and the other
"dephlogisticated air"; and John Waltire, a friend of
Priestley, was one of the first chemists to note the de-
posit of moisture on the inside of a tube after exploding a
mixture of air and "inflammable gas." To Cavendish,
however, belongs the credit of having first supplied the
correct experimental basis upon which accurate knowledge

Fig. 19 — Lavoisier's Apparatus for the Analysis of Water.

could alone be founded. When Lavoisier learned that
Cavendish had proved that water alone is produced by the
combustion of hydrogen — information which was imparted
to him by Sir Charles Blagden in 1782 — he immediately re-
peated Cavendish's experiments on a large scale, and was
assisted on that occasion by Laplace, Blagden also being
present. A large quantity of water was produced, and the
volumes of the combining gases were found to be 1 of
oxygen to 1.91 of hydrogen. Not long after, in conjunc-
tion with Meunier, he performed the converse operation,
in decomposing steam by conducting it over iron wire
heated to redness in a porcelain tube. The iron removed

LAVOISIER 159

the oxygen from the water, while the hydrogen passed on
and was collected in the gas-holder.

The explanation of the solution of metals in acids was
now simple : it depended on the decomposition of water.
While the oxygen combined with the metal to form a
'calx/ the hydrogen was evolved; the 'calx' dissolved in
the acid, forming a salt of the metal. The operation of
producing hydrogen by the action of steam on red-hot iron
met with an equally easy explanation: the oxygen and
iron united to form an oxide — the ancient "ethiops mar-
tial"— while the hydrogen escaped. The converse oc-
curred during the reduction of a 'calx' to the metallic
state by hydrogen. In this case the hydrogen seized on
the oxygen of the 'calx,' removed it in the form of water,
and the metal was left. These experiments were due to
Cavendish ; all that Lavoisier did was to indicate and
prove the true nature of the phenomena. The opponents
of the new doctrines, Priestley prime among them, ex-
erted themselves to disprove the view that water was a
compound of oxygen and hydrogen. But their efforts
were in vain. Many of Lavoisier's opponents had to ad-
mit the justice of his views ; and chemists of standing
commenced the application of his ideas, first in France
(Berthollet 1786, de Morveau, and the cautious Fourcroy
not until 1787), and soon in other countries also (Kirwan,
e.g., in 1792). Lavoisier's critical treatises, which were
directed to showing the untenability of the phlogistic the-
ory, conjoined with his "Traite de Chimie," gave the final
blow to that doctrine. The new doctrine was accepted by
the most prominent chemists after the comparatively short
time which was required to put it to the proof. From the
year 1792, after Klaproth, following Hermbstadt, Girtan-
ner, etc., in Germany, Kirwan and Higgins in England,
Troostwyk, Deiman and van Marum in Holland, and Gio-
bert, Brugnatelli, etc., in Italy, had signified their adhesion
to it, one may speak of the final victory of Lavoisier's sys-
tem; and this, notwithstanding the fact that still many

160 CHEMISTRY

chemists of great eminence refused to accept it in its full
extent — for example, de la Metherie, Sage, and Baume in
France ; Westrumb, Gren, Crell, and Wiegleb in Germany ;
Gadolin and Retzius in Sweden; and Cavendish and
Priestley in England.

Some opponents of the new system, mainly owing to
their misinterpretation of the Lavoisieriain views, contin-
ued to combat it till about 1800.

As late as 1796, Lamarck, for example, wrote an attack
on the Lavoisierian theory of combustion, in which he re-
ferred to the "pretended existence of a material called
oxygen which the pneumatic chemists have never seen nor
studied, and the existence of which they imagine to ex-
plain the effects of 'fixed acidific air.' "

A few words should be said in this connection with re-
gard to Lavoisier's views on the relation of plants and
animals to the atmosphere.

Priestley already knew that oxygen was necessary for
respiration, but his unfamiliarity with accurate analytical
work and his close adherence to the phlogiston theory pre-
vented him from arriving at a true explanation of the
facts he observed. Lavoisier showed how oxygen was
used up in the lungs, in the formation of carbonic acid
and of water, and how this process, which he properly
classed as one of combustion, furnishes to man the heat
necessary for his existence. He demonstrated that the ex-
pired carbonic acid derives its carbon from the blood it-
self; that in the process of respiration we thus, to a cer-
tain extent, burn ourselves, and would consume ourselves
if we did not replace, by means of our food, that which we
have burned.

The experiments which Lavoisier made on respiration
show the clearness of his methods.

One of Lavoisier's earlier memoirs, that presented to
the Academie des Sciences in 1770, entitled "On the Na-
ture of Water and on the Experiments adduced in Proof
of the Possibility of its Change into Earth," illustrates his

LAVOISIER 161

accuracy, thoroughness and acute reasoning. He states
that the purpose of the research was as follows :

"I find myself confronted with the task of settling by
decisive experiments a question of interest in physics,
namely, whether water can be changed into earth, as was
thought by the old philosophers, and still is thought by
some chemists of the day."

It had been noted by many earlier investigators, that
when water was boiled for a long time in a glass vessel, a
mass of white residue was found in the vessel after evapo-
ration. This was long regarded as a conclusive proof that
water could be changed into earth. Lavoisier weighed his
glass vessel, and then, after heating water therein for one
hundred days, found there was no change in the weight of
the vessel and its contents. When he evaporated the
water, he obtained a residue of earthy matter which he
found corresponded, within the range of experimental
error, with the loss in weight of the empty vessel. He
therefore concluded from his experiments, "that the
greater part, possibly the whole, of the earth separated
from rain water by evaporation, is due to the solution of
the vessels in which it has been collected and evaporated."

Scheele afterward showed that this 'earth,' or residue,
possessed the same composition as the glass, thereby con-
firming Lavoisier's work. The old alchemical idea of
transmutation was thus shown to be false, and was finally
dismissed from chemistry.

Lavoisier established the important generalization that
matter may be changed, but not destroyed nor created.
The matter lost from the glass vessel was merely dissolved
in the water. This is the principle of the Indestructibility
of Matter, the fundamental principle of modern science.
However, it must be realized that while from the com-
mencement of his experimental life Lavoisier was guided
in all his reasoning by the recognition of the principle of
the conservation of mass, yet it was only after he had

i62 CHEMISTRY

found this view proved by his work on combustion that he
enunciated it (1785). To quote from his "CEuvres":

"Nothing- is created, either in the operations of art or in
those of nature, and it may be considered as a general
principle that in every operation there exists an equal
quantity of matter before and after the operation; that
the quality and the quantity of the constituents is the same,
and that what happens is only changes, modifications. It
is on this principle that is founded all the art of perform-
ing chemical experiments; in all such must be assumed
a true equality or equation between the constituents of the
substances examined, and those resulting from their analy-
sis."

The establishment of the law of the conservation of
mass has followed curious lines. As Freund observes,
Lavoisier did not arrive at it strictly inductively, by gen-
eralization from a large number of cases in which the
weights of the substances participating in a chemical reac-
tion were compared with the weights of those resulting
from it. The available data of chemical investigations did
not supply him with the material for so doing. The belief
growing among physicists of the imponderable nature of
heat, together with the old view of the indestructibility of
matter in general, must have supplied him with the basis
for an assumption, from which he drew deductions that
were verified by the result of experiment. Generally
speaking, ever since his time, the scientific world has been
content to regard the conservation of mass as an axiom.

A number of Lavoisier's statements indicate that his
views upon the nature of his "matiere de chaleur" (mat-
ter of heat) approximate to the Mechanical Theory of
heat. Thus he states that "Heat is the energy which re-
sults from the imperceptible movements of the molecules
of a substance; it is the sum of the products of the mass
of each molecule into the square of its velocity."

According to him, matter consists of small particles
which do not touch one another, since, otherwise, a dim-

LAVOISIER 163

inution of volume by lowering of temperature could not
be explained: the matter of heat exists between these
particles. The hotter a substance is the more of the mat-
ter of heat does it contain. In the investigations into the
specific heats of various substances, carried out along
with Laplace, Lavoisier further proved that, for a like
increase in temperature, substances do mot take up like
quantities of the matter of heat. Lavoisier knew that, by
the addition of heat, ice is first converted into water, and
the water then into steam. Hence, gases contain most of
the matter of heat. This is what we should understand
when he says that his 'air pur' consists of the acidifying
principle and the matter of heat. During combustion the
former unites with the combustible substance, and the
matter of heat is liberated. It produces light and heat.
Lavoisier also termed the matter of heat "calorique."

Lavoisier's views with respect to the heat liberated dur-
ing combustion, altho not quite accurate, are also of
great importance. He considered that when a solid sub-
stance (phosphorus) burned in gas (oxygen), and the
product of the combustion was solid (phosphoric anhy-
dride), the disengagement of heat was due to the conden-
sation which the gas had undergone, in order that it may
become solid. If the product was gaseous (carbonic anhy-
dride), he attributed the disengagement of heat to the al-
teration of the specific heat. He advanced the general
view that the heat of combustion must be greatest when
two gases unite to form a solid substance. How correctly
he understood the application of these fundamental ideas
is shown by his mode of explaining the lowering of tem-
perature produced by dissolving salts in water. Lavoisier
assumed, as we do, that it is the change of state of aggre-
gation which occasions the absorption of heat. He showed,
further, that the evolution of heat which occurs on mixing
sulphuric acid with water is accompanied by a decrease in
volume, and that both maxima coincide ; so that theory and
experiment agree, (Ladenburg.)

164 CHEMISTRY

It may be said, therefore, that Lavoisier laid the foun-
dation for the modern thermo-chemistry.

Lavoisier also occupied himself with organic chemistry,
or the chemistry of life-products, and made a beginning
toward a scientific study of it by devising a method of
analysis by which these bodies could be burned, and the
water and carbon dioxide which were formed measured.

He heated a known weight of the substance with a
known weight of red mercury oxide, and weighed the car-
bonic acid and water produced. He knew the oxygen con-
tent of the mercuric oxide, and so could ascertain how far
this supplied the carbon and hydrogen with the oxygen
they required, and how far this was furnished by the com-
pound under investigation. Lavoisier in this way deter-
mined the composition of alcohol.

However, the whole system of quantitative organic
chemistry was too young for Lavoisier to anticipate the
nicety with which Liebig, later, could handle these
methods of ultimate analysis; he considered his experi-
ments to be merely confirmatory of his system, the com-
position of sugar a mere incident. Organic bodies in
general he regarded as oxides of a radical, which might
Itself contain hydrogen and carbon, or in some cases these
together with nitrogen, sulphur, and phosphorus.

Lavoisier adhered to Boyle's definition of an element.
With him, an element was any substance which could not
be further decomposed. The metals and the most impor-
tant non-metals were ranked among the elements; and
compound bodies like the alkalies, ammonia and the earths
were numbered among these also, but not without consid-
erable uncertainty being expressed as to their elementary
nature. Oxygen, also recognised as an element, became,
because of its part in combustion and its capacity for com-
bining with so many other elements, the center point of
the antiphlogistic system, which indeed owed its inception
to the knowledge of the behavior of other elements to-
ward oxygen. The importance which Lavoisier attached

LAVOISIER 165

to this gas is clearly shown in his theory of acids, in which
he explained the properties of acids by the hypothesis of
the acidifying principle being oxygen, the name of which
(d^vsyevvaoo, I generate acid) still bears witness to this
view; and in the statement that the bases which combine
with acids also contain oxygen. The composition of a
large number of compounds — oxides, acids and salts — was
thus rightly interpreted, the phlogistic hypothesis having
regarded as simple the substances belonging to the first
two of these classes.

The views of Lavoisier and his disciples with respect to
elements and compounds are to be found in the treatise
entitled "Methode de nomenclature chimique," which was
published by Lavoisier conjointly with Guyton de Mor-
veau, Berthollet, and Fourcroy, in 1787. This work,
in conjunction with the "Traite Elementaire de Chimie"
(1789), changed the existing language of chemistry and
shaped the course of progress still pursued.

In the first-mentioned treatise all substances are divided
into elements and compounds. To the former belonged
— in addition to light and heat — oxygen, hydrogen and ni-
trogen; these formed the first class. The second group
contained the acid-forming elements, sulphur, phospho-
rus and carbon, to which were added the hypothetical rad-
icals of hydrochloric, hydrofluoric and boracic acids. The
third class comprised the metals, the fourth the earths,
and the fifth the alkalies; but Lavoisier considered the ele-
mentary nature of the last of these as so improbable that
in the "Traite Elementaire de Chimie" he no longer in-
cluded them among the elements. For the nomenclature
of the latter, the old names of the metals and of some of
the non-metals {e.g., soufre, phosphore, etc.) were re-
tained, while Lavoisier's new names for others of the non-
metallic elements {e.g., oxygene, hydrogene, azote) were
introduced.

Next came the binary substances, consisting, as they did,
of two elements. The acids occurred in this class. Their

166 CHEMISTRY

names were in each case composed of two words, of
which the first was common to them all and indicated
their acid character (acide), while the second was a spe-
cific name indicating the element or radical occurring in
each. Thus we have 'acides sulfurique, carbonique, phos-
phorique, nitrique/ etc. Two acids containing the same
element or radical were distinguished by the different ter-
mination of the specific name; that containing the smaller
proportion of oxygen receiving the termination 'eux,'
whereby such names as 'acides sulfureux, nitreux, etc.,
were obtained. Hydrochloric acid was called 'acide mu-
riatique,' and the existence of oxygen in it was assumed;
while oxygen was supposed to be present in still greater
quantity in chlorine — the 'acide muriatique oxygene/

The names of the binary substances of the second group
— i.e., of the basic compounds containing oxygen — were
formed in a manner exactly similar. For these the gen-
eral designation 'oxides' was introduced, and to this word
the specific name was appended in the genitive; for ex-
ample, 'oxide de zinc/ 'oxide de plomb,' etc.

The remaining binary compounds were distinguished as
sulphur, phosphorus, carbon, etc., compounds, and received
the class names 'sulfures/ 'phosphures,' 'carbures/ etc.

Compounds of the metals with one another were called
'alliages* (alloys), the expression 'amalgames' being re-
tained, however, for mercury alloys.

With regard to the ternary compounds, the salts alone
need be mentioned. They obtained their class names from
the acids from which they were derived, and were called
accordingly 'sulfates/ 'nitrates/ 'phosphates.' The termi-
nation 'ate' became 'ite' when the salts were derived from
the acid poorer in oxygen instead of from that richer in
oxygen. The name of the base was appended; for exam-
ple, sulfate de zinc, de baryte, etc.

This system of nomenclature embodies the principles
and constitutes the basis of the chemical nomenclature
now in use.

LAVOISIER 167

Studies of the new nomenclature were published by
Scherer (1792), who made an attempt to Germanize the
new terms; Eimbke (1793), who sought to reconcile the
old and the new views in his synonymicon; Arzt (1795) ;
Spalding, who published a work at Hanover, N. H., in
1799, in which he followed de Morveau, but adopted the
name 'septon* for nitrogen and 'septic acid' for nitric
acid, as proposed by Samuel Mitchill, of New York; Sev-
rin (1807) ; and Ritter (1808). It is amusing to note here
that Richard Chenevix, a London chemist, published a
critical examination of the nomenclature of the "French
Neologists" in 1802, in which he quoted Balthazar Sage's
remark that oxygen signified the "son of a vinegar mer-
chant."

When the nature of the theoretical views held during
the Phlogistic Period is compared with that of the ones
accepted at the time of Lavoisier's execution, it will be
understood why a new era — that of quantitative chemistry,
or, as Fourcroy termed it, the "French Chemistry" —
dates from him.

As mentioned, the teachings of Lavoisier gradually be-
came recognized in France — a reward which Lavoisier
himself had the satisfaction of witnessing — and also
gained ground in England, and, through the influence of
Klaproth, in Germany, where his works were translated,
so that at the beginning of the nineteenth century chemists
had almost universally given in their adherence to the
antiphlogistic chemistry.

Lavoisier not only overthrew the old theory, but it is
to his credit that he introduced a new one in its place, and
it is perhaps advisable to state here the most important
heads of his theory (Ladenburg) :

r. In all chemical reactions it is the kind of matter
alone that is changed, while its quantity remains con-
stant; consequently, the substances employed and the
products obtained may be represented by an algebraic

i68 CHEMISTRY

equation in which, if there is any unknown terra, tfois may
be calculated.

2. In the process of combustion the burning substance
unites with oxygen, whereby an acid is usually produced.
In the combustion of the metals, metallic calces are pro-
duced.

3. All acids contain oxygen, united, as he expresses it,
with a basis or radical which, in inorganic substances, is
usually an element, but in organic substances is composed
of carbon and hydrogen, and frequently contains also ni-
trogen or phosphorus.

If these three statements be contrasted with the views of
the phlogistians — i.e., with the theories which prevailed
prior to Lavoisier — we shall appreciate the reformation
introduced by him into chemical science. The direction of
chemical thought was entirely changed, and the facts hith-
erto ascertained appeared in a new light.

Chemistry now had the basis of a correct theory; and
what was of greater value, a knowledge that theories
could be deduced only from the weight relations of ac-
tually occurring reactions. To quote Venable, "There
were to be no baseless and delusive dreams for the future,
altho mistakes might be made in the interpretation of
facts. Further, the grand division into elements and
compounds had been effected, and a suitable nomencla-
ture had been devised, capable of any expansion demanded
by increase of knowledge. The balance, too, had been in-
troduced as the instrument by which precision and accu-
racy were to be attained, and the great arbiter of the fate
of theories. True progress now became possible; and the
century which has since passed has seen this science de-
velop and grow, until men have come scarcely to dare to
put a limit to its possibilities/'

Those three investigators — Guyton de Morreau, Claude
Louis Berthollet, and Antoine Francois Fourcroy — who, in
conjunction with Lavoisier, furnished the basis ol a sci-

LAVOISIER 169

entific nomenclature, and also contributed to the develop-
ment of chemistry by their other works, are next to be
considered.

Louis Bernard Guyton de Morveau (1737-1816) was a
zealous propagandist of the new chemistry, and, upon his
election as a deputy in 1791, he endeavored to render the
chemical knowledge he had acquired and its practical ap-
plication of assistance to France. He aided in founding
the "Ecole Polytechnique," in which institution he sub-
sequently accepted a professorship, and with Maret and
Durande as co-authors, he published a comprehensive text-
book on chemistry in three volumes, entitled "Elemens de
Chymie theorique et pratique" (1777).

Claude Louis Berthollet, who was born at Talloire in
Savoy in 1748, was one of the most distinguished of the
many contemporaries and successors of Lavoisier. He
became an antiphlogistonist in 1786, and from that time
until his death in 1822 he conducted valuable chemical
researches. His important experimental investigations
were in connection with the composition of ammonia,
the properties and nature of chlorine, the production
of bleaching compounds from chlorine, and the com-
position of hydrogen sulphide and hydrocyanic acid. He
observed that solutions of chlorine in water gave off bub-
bles of oxygen, when exposed to the action of light, while
hydrochloric acid remained. Lavoisier had considered
that this acid was a compound of the radical 'murium'
with oxygen, and consequently Berthollet explained the
phenomenon referred to by regarding chlorine as 'oxy-
muriatic acid' — that is, a higher oxygenated product of
'murium/ Berthollet discovered that ammonia is com-
posed of hydrogen and nitrogen; and, after convincing
himself that hydrogen sulphide and hydrocyanic acid con-
tained no oxygen, he opposed the dictum that oxygen was
the principle of acidity.

Berthollet was the author of the following works:
"Elemens de 1'art de la Teinture" (1791), "Kecherches

170 CHEMISTRY

sur les Lois de l'Affinite" (1801), and "Essai de Statique
Chimique" (1803). The last-mentioned treatise was an
exceedingly important contribution to theoretical chem-
istry, for it exerted a powerful influence on the question
of chemical affinity. Berthollet's doctrine of affinity will
be discussed in the next chapter.

Antoine Franqois de Fourcroy (1755-1809) deserves
mention as an organizer, author and teacher. He was an
active expounder of the antiphlogistic doctrine, and prop-
agated the new chemistry by means of articles and treati-
ses. He was the author of the following works : "Leqons
Elementaires d'Histoire Naturelle et de Chimie" (1782),
"Elemens d'Histoire Naturelle et de Chimie" (1789),
"Memoires et Observations de Chimie" (1784), "Philo-
sophic Chimique" (1792), and "Systeme des Connaissan-
ces Chimiques et leurs Applications aux Phenomenes de la
Nature et de l'Art" (1801). Fourcroy 's experimental
work served to pave the way for biological chemistry, and
his joint investigations with Vauquelin furthered the
knowledge of organic compounds.

Another important representative of chemistry in
France at this time was Louis Nicolas Vauquelin (1763-
1829), who succeeded Fourcroy as Professor of Chemis-
try to the Medical Faculty in 1809. To Vauquelin is
owed the discovery of chromium (1797) and beryllia
(1797), the former of which he found in lead spar and the
latter in beryl. His work on the separation of platinum,
palladium (discovered by Wollaston in 1803), rhodium
( Wollaston, 1804), iridium (Tennant, 1803), and osmium
(Tennant, 1803) is also worthy of note. Vauquelin's in-
vestigations on the metals of the platinum group were car-
ried out with the assistance of Fourcroy, and it is likely
that they preceded Smithson Tennant in the discovery of
iridium. In his researches in organic chemistry, Vauque-
lin discovered quinic acid, asparagine, and camphoric acid.
He was the author of two works — "Instruction sur la
Combustion des Vegetaux. la Fabrication du Salin, de la

LAVOISIER 171

Cendre Gravelee" (1794), and "Manuel de rEssayeur"
(1812) — both of which passed through several editions.

The leading chemists of Great Britain and Sweden at
the time when Lavoisier began his attack on the phlogistic
theory strongly opposed the new chemistry. Cavendish,
Priestley, Bergman, and Scheele were unable to accept it,
but Black renounced the old doctrine in 1791, and was fol-
lowed by Dickson and Richard Kirwan. The latter's in-
teresting "Essay on Phlogiston and the Constitution of
Acids" (1787) deals with the transition period from the
old to the new theories, and was translated into French by
Mme. Lavoisier. Among the lesser celebrities in the sci-
ence in England, Lubbock subscribed himself to Lavoi-
sier's views as early as 1784, while Peart and Pew at-
tempted to prove the existence of phlogiston as late as
1795.

In 1810, a small 'Essay on Combustion' was published
in Philadelphia by a Mrs. Fulhame, "wherein the phlogis-
tic and antiphlogistic hypotheses are proved erroneous."
This is merely mentioned on account of its being one of
the earliest American contributions to the subject.

Martin Heinrich Klaproth (1743-1817), first Professor
of Chemistry at the University of Berlin, was character-
ized by the accuracy with which he carried out his investi-
gations; the quantitative method of research was devel-
oped and improved by him, and he thereby helped on the
recognition of the cardinal principles advocated by La-
voisier. After Klaproth had become satisfied with the
correctness of the antiphlogistic doctrine, by testing the
reactions which took place in combustion and calcination,
he became one of its devoted adherents; and his example
led many other German chemists in the same direction.

Klaproth discovered uranium (1789), titanium (1794),
cerium (1803), and zirconia (1789) ; and investigated the
new elements chromium, beryllium, and tellurium (dis-
covered by Miiller von Reichenstein in 1782). He was

172 CHEMISTRY

particularly active in analytical and mineralogical chem-
istry, and introduced many improvements of analytical
methods. Klaproth was, in fact, a true investigator in
every sense of the word. In reporting the results of an
analysis, he published the actual figures obtained, thus in-
troducing a new custom which made it possible to subject
results to correction or criticism. His works are "Chem-
ische Untersuchung der Mineralquellen zu Karlsbad"
(1790), and "Beitrage zur chemischen Kenntniss der
Mineralkorper" (1795-1815). The latter is a collection of
his papers published in the "Memoirs" of the Berlin Acad-
emy and in the "Chemische Annalen fur die Freunde der
Naturlehre." He also published the "Chemisches Wor-
terbuch" (1807-10, 5 volumes; 1815-19, 4 volumes), a
French edition of which appeared in 181 1 ; and edited the
third edition of Friedrich Gren's "Systematisches Hand-
buch der Gesammten Chemie,' an excellent treatise first
published in 1787-90.

From 1803-10, Klaproth was on the board of editors of
the "Neues allgemeines Journal der Chemie," which was
started in 1798 by Scherer. In this connection it should
be mentioned that at that time about twelve chemical peri-
odicals were being published in Germany, three in France,
two in Italy, two in Belgium, one each in Holland and
Sweden, and two in England. These journals exercised
the greatest influence upon the enlargement and diffusion
of chemical knowledge, and they show the extent to which
chemistry was fostered during the last decades of the
eighteenth century.

CHAPTER X

TJSE ATOMIC THEORY AND THE WORK OF DAVY

A desire ingenite in the human mind to find an explana-
tion of natural phenomena, by the aid of speculations re-
specting the ultimate constituents of matter, resulted in
guesses and ideas concerning atoms, in olden times, with-
out, however, the evolution of an exact chemical atomic
theory. With respect to the hypotheses of the ancient
philosophers regarding the constitution of matter, the fol-
lowing estimate by Clifford will suffice in this connection :

"From the earliest times that men began to form any
coherent idea of [the world] at all, they began to guess in
some way or other how it was that it all began, and how
it was all going to end. . . . Modern speculations are
attempts to find out how things began and how they are to
end, by consideration of the way in which they are going
on now. ... A great number of people appear to
have been led to the conclusion that [the modern theory
of the molecular constitution of matter] is very similar to
the guesses which we find in ancient writers — Democritus
and Lucretius. . . . It so happens thai these ancient
writers did hold a view of the constitution of things which
in many striking respects agrees with the view which we
hold in modern times. . . . The difference between
the [ancient and modern views] is mainly this : the atomic
theory of Democritus was a guess, and no more than a
guess. Everybody around him was guessing about the
origin of things, and they guessed in a great number of
i73

174 CHEMISTRY

ways; but he happened to make a guess which was more
near the right thing than any of the others."

The conception of atoms had up to the close of the
eighteenth century been almost entirely the property of the
metaphysician and the mathematical physicist, and had
assisted in extending their sciences. With the exception
of Sennert and Boyle, chemists had aided little in its form-
ulation and less in its establishment, nor had they derived
inspiration from it for the proper founding of their own
science. For more than a century they had been following
the "ignis fatuus" of a false theory of combustion and a
most elusive hypothetical phlogiston. The close of the
eighteenth century found them engaged in bitter strife
over these theories, and too fully occupied to think of
much else than the destruction of the old beliefs and the
adaptation of the new. The master mind of Lavoisier, who
had wrought this revolution, was busied with the greater
work of reconstruction and, dealing little with hypotheses
which could not be directly proved by experiments in his
laboratory, was laying broad and strong the foundations of
the New Chemistry. Consequently the works of Bergman,
Scheele, Priestley, Black, Cavendish, Macquer, and others
do not treat of atoms and their moving forces, except in
an occasional indefinite reference to some sort of particle.

Yet the chemist was the very one required to undertake
the scientific development of the atomic hypothesis and to
establish it as a theory, by discovering a series of facts
which were connected together by it and found in it a sim-
ple explanation.

In 1783, the English chemist Kirwan went so far as to
refer to affinity as that force which holds atoms so inti-
mately together that simple mechanical means are insuffi-
cient to separate them; while his countryman, Higgins,
writing in 1790 on the composition of sulphurous and sul-
phuric acids, expressed the opinion that the atom of sul-
phur is combined with one atom of oxygen in the first, but
with two atoms in the second. It is in view of this state-

ATOMIC THEORY— WORK OF DAVY 175

rnent, and others similar tc it, that some have regarded
Higgins as the real originator of the modern atomic doc-
trine. However, Higgins restricted his attention to a
small number of compounds. His conceptions were not
consistent with fact; he regarded those weights of ele-
ments which combine to form the simplest compound as in
general equal; and he made no attempt to seek confirma-
tion for any theory he had in the laboratory. For long the
common consent of public opinion has given the undivided
honor, due to the discoverer of the great atomic general-
ization in its modern aspect, to John Dalton.

Before the establishment of the chemical atomic theory
could be brought to completion, however, it became neces-
sary to fix the signification of the term "chemical propor-
tions/' according to which simple substances unite to
form compound bodies; and an important part of this
question was solved by two chemists prior to Dalton —
Richter and Proust.

Jeremias Benjamin Richter (1762-1807) published in his
"De usu Matheseos in Chymia" (1789), "Aufangsgrunde
der Stochyometrie oder Messkunst Chymischer Elemente"
(1742-1794), and "Ueber die neuren Gegenstande der
Chymie" (1 791-1802), the results of researches made
mainly while employed as a works chemist in Berlin. The
last two mentioned treatises contain the conclusions which
he drew from his work upon the proportions by weight iai
various compounds.

Richter looked upon chemistry as a branch of applied
mathematics, and exhibited all the distressing qualities of
a person possessed by a fixed idea; he spent his life in
seeking arithmetical regularities in the weights of acids
and alkalies neutralizing each other, and in finding them
in spite of their non-existence.

Nevertheless, he managed to make discoveries of the
highest importance. He not only noticed, but also cor-
rectly interpreted the fact, that when two neutral salts
decompose one another, the resulting salts are still neu-

17$ CHEMISTRY

tral. To quote his conclusions: ". . . concerning that
very common experience that two neutral salts on decom-
position again produce neutral compounds, I could draw
no direct inference other than that fixed quantitative re-
lations must exist between the constituents of the neutral
salts. If a solution of two components is so constituted
that neither of them, as long as it remains in the solu-
tion, exhibits the peculiar characteristics it had before
solution — e.g., the reactions of an acid or of an alkali —
then such a solution is called saturated or neutral, or
also a neutral compound. . . . When two neutral solu-
tions are mixed and a decomposition ensues, the newly-
formed products are also, almost without exception, neu-
tral. . . . Hence it follows that if the combining ra-
tios in the original compounds be known, those in the
newly formed compounds are known also."

C. F. Wenzel (1740-1793), at an earlier date (1777),
had demonstrated that acids and bases combine in con-
stant proportions, but had failed to note the persistency
of the neutrality in the double decomposition of the neutral
salts.

Richter deduced from the maintenance of neutrality
when one metal precipitates another from a neutral solu-
tion— a relation Bergman had observed, but which he in-
terpreted in terms of another theory — that the quantities
of two metals which dissolve in the same amount of acid
also unite in their oxides with the same amount of oxygen.
Therefore, he established that quantities of two substances
which are equivalent in one reaction are also equivalent in
others; he was the originator of stoichiometry, or "the
art of chemical measurement, which has to deal with the
laws according to which substances unite to form chemi-
cal compounds."

Notwithstanding the fact that Richter's treatise con-
tained such important discoveries these remained unrecog-
nised until Fischer published a table of the relative affini-

ATOMIC THEORY— WORK OF DAVY 177

ties of bases and acids, founded on the values Richter
had obtained, in his translation of Berthollet's "Recher-
ches," made in 1802.

Berthcllet accepted the law of proportionality and gave
an account of it in his "Essai de Statique Chimique,"
in which he reprinted Fischer's note. Thus Richter's work,
which at the time of its publication had been almost com-
pletely ignored, became more widely known and appre-
ciated.

Louis Jose Proust (1 755-1826), altho a Frenchman by
birth, conducted his most important researches in Madrid,
where he settled after 1791. The work for which he is
celebrated was the result of a series of questions which
Berthollet had advanced.

The two works of Berthollet on affinity — "Recherches
sur les Lois de rAffinite" and "Essai d'une Statique Chi-
mique" — were particularly directed against false views of
affinity and the misuse of the so-called affinity tables of
Geoffrey, Bergman, and others.

He contended that affinity was by no means a simple
force, and easy to determine or measure; but was influ-
enced by temperature, physical state, cohesion, and espe-
cially by mass. The latter largely determined the course
of chemical reactions.

He went further, however, and from the correct pre-
mise of the influence of mass on the chemical effect pro-
duced, Berthollet drew the erroneous inference that mass
had an influence, not only on the amount of change but
also on the kind, producing a continuous variation in the
ratio in which the constituents are united in the com-
pound. He asserted the variability of the composition
of chemical compounds, the possibility of combination be-
tween constituents in all sorts of continuously varying
ratios. None of the other leading chemists of the day were
able to concur with his views as to the lack of any fixity
or constancy of proportions in chemical compounds. Yet

178 CHEMISTRY

they raised no objection, probably owing to Berthollet's
reputation, and it remained for Proust to attack the theo-
retical conclusions of his eminent contemporary.

Proust's numerous papers in his controversy with Ber-
thollet appeared in the "Journal de Physique" between the
years 1802 and 1808. The lucidity of the arguments em-
ployed, the variety of the experimental work described,
and the freedom and keenness of the style, render these
papers, which deal exclusively with the distinctly dry
subject of quantitative analysis, most interesting reading
even now.

Proust proves that substances formed under the most
varied conditions have a fixed composition, and he shows
that Berthollet's examples of variable composition were
all cases of mixtures. This involves him in the necessity
of discriminating between mixtures and compounds, an
undertaking the difficulties of which he fully realized, and
with which he dealt in a manner very much like that still
resorted to for the same purpose, (von Meyer.)

In 1799, Proust had proved the constant composition
of native and artificial carbonate of copper, and had
enunciated the general principle of which this constituted
an example. Of greater importance than these were ob-
servations he made upon the two compounds iron forms
with sulphur and the two stages of oxidation shown by
tin. He further investigated the compounds of antimony,
cobalt, nickel, and copper, and throughout he found that,
vary the conditions and relative masses at pleasure, the
oxides and sulphides produced always have a definite
composition. To be sure, an element might combine with
oxygen or sulphur in two proportions, but each was a
compound of definite proportions.

Proust showed the error which underlay the old method
of determining the quantity of oxygen in oxides, of esti-
mating the metal and calculating the oxygen by difference,
proving that in many cases the bodies so examined were
not oxides at all, but compounds containing hydrogen —

ATOMIC THEORY— WORK OF DAVY 179

hydroxides we now call them. He, moreover, demon-
strated that many of the bodies, on the analysis o£ which
Berthollet had based his generalization, were not simple
at all, but mixtures of substances, themselves of perfectly
definite composition. So accurate were his analytical in-
vestigations, and so logical his reasoning, that Berthollet
was overcome at every point. The law of definite chemi-
cal proportions, as we now have it, was the fruit of his
persevering labors. This law is one of the fundamental
principles of chemistry. It is expressed by the greatest
teacher cf chemistry as follows:

"If one substance is transformed into another, then the
masses of these two substances always bear a fixed ratio
to each other. If several substances react together, then
their masses, as well as those of the new bodies formed,
always bear fixed proportions to each other." (Ostwald,
"Outlines of General Chemistry.")

Undoubtedly, if Proust had calculated the results of
his experiments on the composition of binary compounds
(sulphides, oxides) in another manner from what he did,
he would have discovered the law of multiple proportions,
but the propounding of this is due to Dalton.

John Dalton (1766-1844) was born at Eaglesfield, in
Cumberland, the son of a poor weaver; endowed with nat-
ural aptitude and an indomitable will, he utilized all pos-
sible opportunities for the study of mathematics and natu-
ral philosophy. From 1781 to 1793 he taught school, in-
structed and lectured at Kendal, devoting all the time
and energy he could spare to scientific investigations,
chiefly meteorological.

In 1793 he went to Manchester as tutor of mathematics
and natural philosophy at a Presbyterian College. Tho
he resigned this post six years later, he remained in
Manchester to the end of his life, earning his living as
a private teacher, and devoting himself uninterruptedly
and earnestly to scientific research.

i8* CHEMISTRY

The earlier researches of Dalton on the expansion of
gases by heat and their absorption by liquids were of
considerable influence on his later chemical work, as it
was through them that he acquired the experimental skill
which led to the discovery of the law of multiple propor-
tions, which, with the conception of the atomic theory
which arose from it, dates from 1802.

On November 12, 1802, Dalton read a paper entitled
"An Experimental Enquiry into the Properties of the
Several Gases or Elastic Fluids constituting the Atmos-
phere," in which is found the first example of the law.
In determining the amount of oxygen in the air the fol-
lowing experiment was performed:

"If 100 measures of common air be put to 36 of pure
nitrous gas in a tube 3/is of an inch wide and 5 inches
long, after a few minutes the whole will be reduced to
79 or 80 measures, and exhibit no signs of either oxygen-
ous or nitrous gas. If 100 measures of common air be
admitted to 72 of nitrous gas in a wide vessel over water,
such as to form a thin stratum of air, and an immediate
momentary agitation be used, there will, as before, be
found 79 or 80 measures of pure azotic gas [nitrogen]
for a residuum. If, in the last experiment, less than 'j'Z
measures of nitrous gas be used, there will be a residuum
containing oxygenous gas; if more, then some residuary
nitrous gas will be found. These facts clearly point out
the theory of the process: the elements of oxygen may
combine with a certain portion of nitrous gas, or with
twice that portion, but with no intermediate quantity.
In the former case nitric acid is the result; in the latter
nitrous acid: but as both these may be formed at the
same time, one part of the oxygen going to one of nitrous
gas, and another to two, the quantity of nitrous gas ab-
sorbed should be variable; from 36 to y2 per cent, for
common air."

With regard to this experiment Roscoe says: "In the
memorable case in which Dalton announces the first in-

ATOMIC THEORY— WORK OF DAVY 181

stance of combination in multiple proportions the whole
conclusion is based upon an erroneous experimental ba-
sis. If we repeat the experiment, as described by Dalton,
we do not obtain the results he arrived at. We see that
Dalton's conclusions were correct, altho in this case it
appears to have been a mere chance that his experimental
results rendered such a conclusion possible."

The first of the observations of Dalton which furnished
the experimental basis for the atomic theory consisted in
the determination of the composition of two hydrides
of carbon. Dalton writes : "It was in the summer of 1804
that I collected at various times and in various places the
inflammable gas [marsh gas] obtained from ponds." He
found that marsh gas, like olefiant gas (ethylene), con-
tains nothing but carbon and hydrogen, and that these
two substances, termed light and heavy carburetted hydro-
gen, respectively, showed a simple multiple ratio between
the weights of the constituent elements, namely :

In carburetted hydrogen from stagnant water, 4.3 of
carbon were combined with 2 of hydrogen.

In olefiant gas, 4.3 of carbon were combined with 1
of hydrogen.

This regularity induced him to investigate other com-
pounds in the same direction ; thus, in the case of carbonic
oxide and carbonic acid he found that, for the same
amount of carbon, the ratios of oxygen present in these
were again, respectively, as 1:2. His conviction that
there must be a law underlying these simple relations
scarcely necessitated any further accretion after he had en-
countered similar simple numerical proportions in the re-
sults of his analysis of nitrous oxide, nitric oxide, nitrous
acid and nitric acid — i.e., the anhydrides of the two last —
and the oxygen compounds of sulphur. He had, there-
fore, demonstrated that when different quantities of one
element combined chemically with one and the same quan-
tity of another, these amounts stood in a simple relation
to one another — a relation which could be expressed by

iS2 CHEMISTRY

whole numbers. The "law of multiple proportions" was
thus discovered; it had, indeed, been deduced from ex-
periments which were of necessity not very exact, but
this was to be expected from the condition of analytical
chemistry at that time.

Dalton next sought an explanation of the numerical
relations he had discovered, and this was afforded him
by the atomic hypothesis. For instance, he had but to
assume that in carbon monoxide one atom of carbon was
combined with one of oxygen, and in carbonic acid one
atom of carbon was united to two of oxygen. Upon this
basis Dalton erected his Atomic Theory, which may be
detailed from statements in his "New System of Chemical
Philosophy'' (1808-1810), as follows:

1. All bodies of sensible magnitude are constituted of
a vast number of extremely small particles or atoms of
matter bound together by a force of attraction, which, as
it endeavors to prevent their separation, is called attrac-
tion of cohesion ; but as it collects them from a dispersed
state is called attraction of aggregation, or, more simply,
affinity.

2. The ultimate particles of all homogeneous bodies are
perfectly alike in weight, figure, etc. In other words,
every particle of water is like every other particle of
water, every particle of hydrogen is like every other
particle of hydrogen, etc.

3. No new creation or destruction of matter is within
the reach of chemical agency. All the elements we can
produce consist in separating particles that are in a state
of cohesion or combination and joining those that were
previously at a distance.

4. The ultimate particles of all simple bodies are atoms
incapable of further division. These atoms (at least
viewed along with their atmospheres of heat) are all
spheres, and are possessed of particular weights which
may be denoted by number.

ATOMIC THEORY— WORK OF DAVY 183

5. If there are two bodies which are disposed to com-
bine, then their combination takes place by atoms.

6. In an elastic gas each particle occupies the center of
a comparatively large sphere and supports its dignity by
keeping all the rest, which by their gravity, or otherwise,
are disposed to encroach upon it, at a respectful distance.

The method by which Dalton determined the relative
atomic weights from the proportions by weight in which
the elements unite to form compounds, falls next to be
described.

To accomplish this the first thing necessary was to set-
tle the number of atoms in a compound. According to
Dalton, this number is to be sought for, in general, in the
simplest possible ratios. In estimating it, he started from
the following principles:

1. When only one compound of two elements is known,
this is composed of an atom of the second order.

2. When two compounds are known, the one consists of
an atom of the second and the other of an atom of the
third order.

3. When three compounds are known, one atom of the
second and two atoms of the third order must be assumed.

How did Dalton now proceed to the determination of
the atomic weights — i.e., the relative weights of the small-
est particles? In the first place it was necessary to choose
a unit for comparison. As unit he assumed hydrogen
with the atomic weight = 1, and he referred all the other
atomic weights to this. To fix the others, he then applied
his first principle. At that time only one compound each
of oxygen and of nitrogen with hydrogen was known,
viz., water and ammonia, respectively; therefore, the
atomic weights of oxygen and nitrogen can be determined
directly from the composition of these compounds. In this
way Dalton found them to be 7 and 5, respectively. He
checked the numbers so obtained by the proportions of
the oxygen and nitrogen in the oxygen compounds of
nitrogen. He was acquainted with four of the latter. In

i84 CHEMISTRY

nitric oxide he found 7 parts of oxygen for 5 of nitrogen ;
its atom was, therefore, the atom of the second order,
derived from these elements. In nitric acid, according to
his view, there were 14 parts of oxygen for 5 of nitrogen,
or two atoms of the former gas for one of the latter. In
nitrous oxide, 7 parts of oxygen were combined with 10
parts of nitrogen, and in this he therefore assumed two
atoms of nitrogen and one of oxygen. Nitrous acid,
however, is supposed to contain loyi parts of oxygen for
5 of nitrogen, and in it he might have assumed two atoms
of nitrogen and three of oxygen. He preferred, however,
to regard this substance as a compound of nitric acid and
nitric oxide.

Likewise, he found in ethylene 5.4 parts of carbon for
1 of hydrogen, and in marsh gas the same quantity of
carbon for 2 of hydrogen. On this account he regarded
ethylene as consisting of atoms of the second order, and
assumed the atomic weight of carbon to be 5.4. Carbonic
oxide likewise consisted of atoms of the second order,
since he found in it 7 parts of oxygen for 5.4 of carbon,
while carbonic anhydride had atoms of the third order,
because it contains 14 parts of oxygen for 5.4 of carbon.

As the analytical methods Dalton employed were liable
to many sources of error, it was out of the question that
the results he obtained could be accurate. However, he it
was who propounded the principle of the determination
of the combining weights of the elements, and this work
brought him everlasting fame.

Dalton's atomic theory, generally speaking, was favor-
ably received by chemists. Thomas Thomson (1773-1852),
who founded the first chemical laboratory for general in-
struction in Great Britain while professor in the Univer-
sity of Glasgow, became its devoted supporter, and his
"System of Chemistry" (1807) made it known to the
general public. In 1808, Thomson supplied an observation
of his own in support of the law of multiple proportions.

Dalton's attempts at a graphic presentment of the ulti-

ATOMIC THEORY— WORK OF DAVY 185

mate particles of various substances must not be forgotten.
The symbols he used to represent the atoms of the ele-
ments and to indicate the constitution of chemical com-
pounds, as well as his relative weight values, are here
given. This system of notation never came into general
use owing to the introduction of a simpler system by
Berzelius some time afterward.
To quote his own inference:

"It appears that there are two oxalates of strontian, the
first obtained by saturating oxalic acid with strontian
water, the second by mixing together oxalate of ammonia
and muriate [chloride] of strontian. It is remarkable
that the first contains just double the proportion of base
contained in the second." He also investigated the potash
salts of oxalic acid.

"Oxalate of potash readily crystallizes in flat rhom-
boids, commonly terminated by dihedral summits. The
lateral edges of the prism are usually beveled. At the
temperature of 6o° it dissolves in thrice its weight of
water. . . . This salt combines with an excess of acid
and forms a super-oxalate, long known by the name of
salt of sorrel. The acid contained in this salt is very
nearly double of what is contained in oxalate of potash.
Suppose 100 parts of potash; if the weight of acid neces-
sary to convert this quantity into oxalate be x, then 2x
will convert it into super-oxalate."

Similar research was done by W. H. Wollaston (1766-
1828), who, by experiment, found that in the two com-
pounds termed "subcarbonate of potash" and "carbon-
ate of potash," the proportions of carbonic acid relatively
to the same amount of potash were as 1:2. He also
showed that "super-sulphate" (bisulphate) of potash con-
tains "exactly twice as much acid as is necessary for the
mere saturation of the alkali present." These contribu-
tions proved the applicability of the law for salts, and
the importance of the relation thus made evident was, in
general, realized by the chemists of the day.

186 CHEMISTRY

Fig. Rel. wt.

ii. 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

Fig. Rel. wt.

1. Hydrogen 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

21. An atom of water or steam, composed of 1 of oxy-

gen and 1 of hydrogen, retained in physical con-
tact by a strong affinity, and supposed to be sur-
rounded by a common atmosphere of heat 8

22. An atom of ammonia, composed of 1 of azote and

I of hydrogen 6

23. An atom of nitrous gas, 1 azote -f- 1 oxygen 12

24. An atom of defiant gas, 1 carbone -f- 1 hydrogen. . 6

25. An atom of carbonic oxide, 1 carbone -f- 1 oxygen. 12

26. An atom of nitrous oxide, 2 azote -j- 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 -j- 2
hydrogen 16

30. An atom of oxynitric acid, 1 azote + 3 oxygen. . 26

31. An atom of sulphuric acid, 1 sulphur -j- 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 + I nitrous

gas 31

35. An atom of acetous acid, 2 carbone + 2 water. . . 26

36. An atom of nitrate of ammonia, 1 nitric acid -f- l

ammonia -j- 1 water ^$

37. An atom of sugar, 1 alcohol -f- 1 carbonic acid. . . 35

CLEMENTS

Simple

*. Z 3. 4. &' 6.^ ?/ &

O. © # O © © © ©

& 10. 11. 12. 13. 14. 15. 1&

®#©©O©0O

17. 18. 19. 20.

© © © o

Binary

81. 22. 23. 24. 25}

©o o® (do ©@ om

Ternary
26- 27. 2a 29.

©O© CKDO 0®0 ©@©

Quaternary
30. 31. 32. 33.

CTO CTO CTO

Quinquenary and Septenary

34. 35.

q|3bO

Septenary

36. 37.

Fig. 2© — Dalton's Graphic Presentment of the Elements.

188 CHEMISTRY

It is now necessary to discuss the position which Davy
and Gay-Lussac, among others, held respecting Dalton's
atomic theory, as well as to narrate their services to
chemistry in general.

Humphrey Davy, the son of an engraver, was born at
Penzance in 1778. The family circumstances were some-
what impecunious, and at the age of seventeen he was
apprenticed to a surgeon-apothecary in his native town

Fig. 21 — Preparation of Nitrous Oxide.

At the age of twenty he was placed in charge of the
laboratory of the Pneumatic Institute at Bristol, founded
by Beddoes for the application of gases to the treatment
of diseases. Davy's environments here were most pro-
pitious for a successful career of scientific research. His
laboratory was well furnished, and was supported by the
subscriptions of scientific men. He had plenty of time
at his disposal, and the age was one of discovery and rapid
progress in the science. His experiments related chiefly
to nitrogen monoxide, or nitrous oxide, and in a short
time he published his "Researches Chemical and Philo-
sophical, chiefly concerning Nitrous Oxide and its Res-
piration." His courage and his determination were well

ATOMIC THEORY— WORK OF DAVY 189

proved by these experiments. The effects of this gas,
supposed to be poisonous, were tried upon himself. He
discovered its anesthetic action. He then subjected him-
self similarly to the action of hydrogen, nitrogen, and
carbonic acid. In 1801, Davy left Bristol to become a
lecturer at the Royal Institution, and two years later was
elected Fellow of the Royal Society. He was soon a
necessary figure in the fashionable life of the day; his
auditors at the Royal Institution were numbered by the
thousand ; his name was on everybody's lips. It was Cole-
ridge who said, "I attend Davy's lectures to increase my
stock of metaphors." He was knighted in 181 1 and cre-
ated baronet in 1812. A terrible mining disaster at Fel-
ling brought him an invitation from the governors of
the mine to investigate the conditions of such occurrences,
and after an extended investigation into the nature of
marsh gas in its different admixtures with air, he pro-
jected his well-known safety lamp. This is but one in-
stance out of many of his scientific insight being turned
to material advantage. Davy was elected President of the
Royal Society in 1820, and died at Geneva in 1829.

At the Royal Institution Davy had at his command an
excellent electric battery, and, as he had for some time
considered that the most-needed step in chemistry was the
decomposition of some of the substances then regarded as
elementary, he thought that this was the most promising
means for the solution of the question.

In 1790 Galvani made his well-known experiment, and
ten years later Volta invented his electric cell. These
were important elements in the inquiry which went to cor-
relate chemical and electrical phenomena, and the percep-
tion that a close relation existed between electrical force
and chemical reaction spread rapidly at the beginning of
the nineteenth century, after the decomposition of water
into its constituents by the galvanic current had been
proved by Nicholson and Carlisle (in 1800), and that of
salts into their bases and acids by Berzelius and Hisinger

190 CHEMISTRY

(in 1803). The most important of the many and varied
observations on the deportment of chemical compounds
when subjected to the action of the current, however, were
made by Davy, and his discoveries entitle him to be re-
garded as the pioneer of electrochemistry, as well as one
of the most brilliant chemists the world has ever seen.

Davy was among the first to investigate the question of
the decomposition of water. This work was begun in
1800. In his Bakerian lecture delivered before the Royal
Society in i8c6, the subject of which was, "On Some
Chemical Agencies of Electricity," is found an investiga-
tion concerning the products of the electrolysis of water.
Besides hydrogen and oxygen there were also formed acid
and alkali. Davy states this as a fact :

"The appearance of acid and alkaline matter in water
acted on by a current of electricity at the opposite elec-
trified metallic surfaces was observed in the first chemical
experiments made with the column of Volta."

The problem requiring solution then was to ascertain
whether the acid and alkali were derived from the water,
and if not, whence they came. Davy therefore proceeded
to carry out this electrolysis in vessels of various mate-*
rials, and showed that the products mentioned, the acid
and alkali, were due to the glass, or to the matter dissolved
in the water, or to the air itself. If the water, distilled in
silver, was electrolyzed in gold vessels, in an atmosphere
of hydrogen, the acid and alkali did not appear. To give
his own description :

"I repeated the experiment under more conclusive cir-
cumstances. I arranged the apparatus as before [gold
cones and water distilled in silver vessels] ; I exhausted
the receiver and filled it with hydrogen gas from a conven-
ient air-holder; I made a second exhaustion and again
introduced hydrogen that had been carefully prepared.
The process was conducted for twenty-four hours, and
at the end of this time neither of the portions of the water
altered in the slightest degree the tint of litmus. It seems

ATOMIC THEORY— WORK OF DAVY 191

evident then that water chemically pure is decomposed by
electricity into gaseous matter alone, into oxygen and
hydrogen."

He next investigated the decomposition of salt solutions,
and found confirmation of the statements of Berzelius and
Hisinger. But he proceeded with still greater circumspec-

Fig. 22 — Davy's Apparatus for Electrolysis of Water.
A. and B., electrodes ; C, strand of asbestos.

tion, and sought to follow up the phenomena more exactly.
All the means were at his command, and he did not hesi-
tate to avail himself of them.

Direct observation proved to Davy that hydrogen, the
alkalies, the metals, etc., are separated by means of the
current at the negative pole, and oxygen and the acids at
the positive pole. From this he concluded that the former
substances possess a positive, while oxygen and the acids

192 CHEMISTRY

possess a negative electrical energy; that in this case, as
usual, the oppositely electrified bodies attract each other;
and that, in consequence, the positive substances separate
at the negative pole, and vice versa. In this assumption
Davy had arrived at an explanation of the phenomena of
decomposition observed in the galvanic circuit. But he
proceeded a step further, and endeavored to refer all
chemical combination and decomposition to similar causes.

According to him the heat observed in certain cases of
decomposition were manifestations of electricity.

On November 19, 1807, Davy delivered an account to
the Royal Society of his most recent work on the nature
of the alkalies. He had made an attempt to decompose
them by the electrolysis of their aqueous solutions, but
without success; he had then passed a powerful current
through solid potash fused over a flame, and had observed
a most intense light at the negative pole, due probably to
the combustion of the element he was seeking. And his
next experiment was decisive ; to give his own description :
"A small piece of pure potash, which had been exposed for
a few seconds to the atmosphere, so as to give conducting
power to the surface, was placed upon an insulated dish
of platina, connected with the negative side of a powerful
battery, . . , the positive pole was brought in contact with
the upper surface of the alkali. -On passing the current,
the potash began to fuse at both its points of electric ac-
tion. There was violent effervescence at the upper sur-
face ; at the lower or negative surface there was no liber-
ation of elastic fluid, but small globules having a high me-
tallic luster appeared." And he had treated soda in the
same manner with similar results. "It appears," he said,
"that in these facts there is evidence for the decomposi-
tion of potash and soda into oxygen and two peculiar sub-
stances." To these two peculiar substances he gave the
names potassium and sodium.

In 1808, Davy had decomposed hydrochloric acid by
means of potassium, and in this way had obtained hydro-

ATOMIC THEORY— WORK OF DAVY 193

gen and potassium chloride, the latter of which he had
also prepared by burning potassium in chlorine. He
proved, in 1809, that the chlorides (muriates) of the met-
als are not decomposed by heating them with calcium
metaphosphate or with silicic anhydride, but that decom-
position at once begins when aqueous vapor is conducted
over the mixture. Davy considered that Henry's hypothe-
sis furnished the explanation of these experiments, and
that hydrochloric acid could only be separated as soon as
the quantity of water necessary for its existence was sup-
plied.

About the same time Gay-Lussac and Thenard showed
that water is produced as well as silver chloride by the
action of this acid upon silver oxide; and, as formerly,
they assumed that this water was already present in the
hydrochloric acid. They then effected the synthesis of the
acid, by exposing a mixture of chlorine and hydrogen to
sunlight. On this occasion, they advanced a complete the-
ory regarding hydrochloric acid and chlorine, by means of
which they were able to explain all their experiments.
According to them, hydrochloric acid was a compound of
an unknown radical, "muriaticum," with oxygen and
water; chlorine, on the other hand, was anhydrous hydro-
chloric acid combined with more oxygen.

Davy next sought to find the oxygen which was assumed
to be present in "oxymuriatic acid," but by no means what-
ever could he abstract the oxygen from this compound;
2. succession of electric sparks produced no effect, neither
did strongly ignited carbon. If the gas were oxidized, mu-
riatic acid, phosphorus and sulphur might be expected to
combine with the oxygen and liberate the muriatic acid;
no such result had been obtained, however, and the oily
liquids which were produced only yielded muriatic acid
on the addition of v/ater. The "oxymuriatic acid/' when
passed over oxides of potassium, barium, and other metals,
produced "muriates" with evolution of precisely that
amount of oxygen contained in the oxides. Referring to

i94 CHEMISTRY

this experiment, Davy remarks, "It is contrary to sound
logic to say that the exact quantity of oxygen is given
off from a body not known to be compound, when we are
certain of its existence in another." He therefore ex-
plained these facts by regarding "oxidized muriatic acid"
as an elementary substance, and muriatic acid as its com-
pound with hydrogen ; but chemists hesitated about ac-
cepting his views. Davy maintained that this element, to
which he gave the name "chlorine," resembled oxygen in
many respects, and, in a limited sense, was also to be re-
garded as an acidifier and supporter of combustion.

The work of Davy was clear and brought conviction,
and by 1820 his theory of the nature of chlorine was gen-
erally accepted. But oxygen could no longer be regarded
as the sole acid-making principle, and this necessitated a
new theory of acids.

A French saltpeter manufacturer, Courtois, in 181 1 dis-
covered a peculiar substance in the soda obtained from
sea plants; he related his observation to Clement, who
showed the body in question to Davy. Davy soon demon-
strated its elementary nature, and Gay-Lussac, after a
complete investigation of iodine, as he termed it, and its
compounds, succeeded in showing its marked likeness to
chlorine. Bromine was discovered by Balard, in 1826, in
the mother liquor of sea-water. Hydrofluoric acid re-
sisted all attempts to isolate its radical, but Ampere's sug-
gestion that it was constituted similarly to muriatic acid
found general acceptance.

From his observation that iodic anhydride was devoid
of acid properties, but acquired them after combination
with water, Davy arrived at the conclusion that hydrogen
and not oxygen was the acidifying principle in the latter
compound; hydrogen, in his opinion, was an essential con-
stituent of all acids. The assumption that hydrated acids
and salts contained water or metallic oxides together with
acid anhydrides, he held to be unproven and unnecessary.

The French chemist Dulong expressed himself in a

ATOMIC THEORY— WORK OF DAVY 195

like manner after an investigation of oxalic acid and its
salts ; the former he looked upon as a compound of hydro-
gen with carbonic acid, while in the latter he assumed an
analogous combination of the metals with the elements of
carbonic acid.

The principles of a new theory of acids was, therefore,
included in the discussions of Davy and Dulong, but it is
to be deplored that they did not follow them up sufficiently,
as otherwise they might have prevented the distinction
which now began to be drawn between acids containing
oxygen and those which did not.

With regard to Davy's attitude to the atomic theory of
Dalton, it should first be mentioned that he asserted in
1809 that William Higgins was the originator of this doc-
trine. The latter's "A Comparative View of the Phlogis-
tic and Antiphlogistic Theories with Inductions" (1789),
Davy maintained, contained views similar to those of Dal-
ton; but later he recognised Dalton's service.

Davy regarded Dalton's atomic weights as simply the
proportion numbers of the elements, and maintained that
there was no positive basis upon which to proceed for the
determination of the atomic weights. Two other investi-
gators of this time — Wollaston and Gay-Lussac — also re-
fused to admit that Dalton's atomic weights were really
such. Previous to Davy, Wollaston had asserted that
these were the chemical equivalents of the elements, while
Gay-Lussac would only concede that the ratio of one ele-
ment to another was fixed by analytical and synthetical
determinations. His law of combining volumes had a
definite bearing on the atomic theory, however, and this
generalization, along with his work in analytical chemistry
and numerous researches in inorganic chemistry, render
further notice of him necessary.

Josephe Louis Gay-Lussac (1778-1850) was a student of
Berthollet, and in 1809 became professor of chemistry at
the Ecole Polytechnique, at the same time holding the
chair of physics at the Sorbonne. In 1832, he accepted the

196 CHEMISTRY

chair of chemistry at the Jardin des Plantes. Gay-Lussac
was a masterly investigator, capable of the most accurate
analytical work and exact in observation, and enriched
chemistry with many valuable researches. Of especial im-
portance was his work on iodine and its compounds; on
cyanogen, which he characterized as the first compound
radical; on sulphur and its compounds; on the oxides of
nitrogen ; on the isolation of boron ; and his conjoint in-
vestigations with L. J. Thenard on the alkali metals, and
with Liebig on the fulminates. He also introduced im-
proved methods of inorganic and organic analysis, and is
to be regarded as having laid the foundations of volumet-
ric analysis. His name is particularly associated, however,
with his investigations on the combining volumes of gases.

In 1805, Gay-Lussac and Alexander von Humboldt pub-
lished a memoir entitled "Experiments on the Ratio of the
Constituents of the Atmosphere," in which they announced
that they had found the volume ratio, hydrogen : oxygen : :
200: 100. This led Gay-Lussac to extend his investigations
to the volume relations of other gaseous substances which
are compounds of gaseous constituents, and by the close
of the year 1808 he was able to announce results which
showed the existence of a simple and general law. He
summarized his results as follows :

"I have shown in this memoir that the compounds of
gaseous substances with each other are always formed in
very simple ratios, so that representing one of the terms
by unity, the other is one, or two, or at most three. These
ratios by volume are not observed with solid or liquid sub-
stances, nor when we consider weights, and they form a
new proof that it is only in the gaseous state that sub-
stances are in the same circumstances and obey regular
laws. . . . The apparent contraction of volume suf-
fered by gases on combination is also very simply related
to the volume of one of them, and this property likewise
is peculiar to gaseous substances."

ATOMIC THEORY— WORK OF DAVY 197

This law of combining volumes is stated by Ostwald in
his "Outlines of General Chemistry" as follows:

"If gaseous substances enter into chemical combination,
their volumes are in simple rational proportions, and if
a gaseous substance is formed by their union, its volume
also is rationally related to the volumes of the original
gases."

Gay-Lussac was himself inclined to conjoin his law of
volumes with the atomic theory — indeed, he recognised in
it a support for the latter. A similar molecular condition
was essential, however, in order that all gases should de-
port themselves alike toward pressure and changes of
temperature, and, besides, obey his law of volumes. In
other words, equal volumes of gases must contain equal
numbers of molecules. Gay-Lussac drew no distinction
between these molecules and atoms, recognizing but one
kind. of final particle. Dalton opposed this reasoning, and
stated that he had held the same view as to combining vol-
umes at one time, but finally saw that it was untenable.
To quote from his "A New System of Chemical Philoso-
phy":

"At the time I formed the theory of mixed gases I had
a confused idea, as many have, I suppose, at this time,
that the particles of elastic fluids are all of the same size ;
that a given volume of oxygenous gas contains just as
many particles as the same volume of hydrogenous. But
... I became convinced that different gases have not their
particles of the same size; and that the following may be
adopted as a maxim till some reason appears to the con-
trary, namely :

"That every species of pure elastic fluid has its parti-
cles globular and all of a size; but that no two species
agree in the size of their particles, the pressure and tem-
perature being the same."

He also maintained that gases do not combine exactly
by volumes, but frequently by fractions of volumes. He
said: "The truth is, I believe, that gases do not unite in

198 CHEMISTRY

equal or exact measures in any one instance; when they
appear to do so, it is owing to the inaccuracy of our ex-
periments. In no case, perhaps, is there a nearer approach
to mathematical exactness than in that of one measure of
oxygen to two of hydrogen; but here the most exact ex-
periments I have ever made gave 1.97 hydrogen to 1 oxy-
gen."

His argument may be illustrated as follows, taking hy-
drochloric acid as an example :

One atom of hydrogen chloride consists of one atom
of hydrogen and one atom of chlorine. Then, if equaf
volumes of gases ccntain equal numbers of molecules, one
volume of hydrogen and one volume of chlorine should
produce one volume of hydrogen chloride, but they really
form two. Consequently, each one of these can contain
only half as many atoms as the original volumes of the
constituents. Such ratiocination is manifestly conclusive
so far as the theory of the volumes containing the same
number of atoms is concerned, unless some different defi-
nition of atoms is assumed.

The connection between Gay-Lussac's law of volumes
and Dalton's atomic theory was shown by the Italian
physicist Amadeo Avogadro (1776-1856) in 181 1.

Avogadro discarded Dalton's artificial distinction be-
tween the ultimate particles of a compound and those of
an element, and made a distinction between what he
termed "molecules integrants" and "molecules elemen-
taires," or molecules and atoms, the former being com-
pound particles made up of the indivisible atoms. The
researches of Gay-Lussac indicate, then, that a molecule
of water consists of one molecule of hydrogen and one-
half molecule of oxygen. A molecule of hydrogen chlo-
ride consists of one-half molecule of hydrogen and one-
half molecule of chlorine, and so the difficulty pointed out
by Dalton was effaced from chemical literature.

Avogadro's assumption that "equal volumes of gases,

ATOMIC THEORY— WORK OF DAVY 199

elementary or compound, at the same temperature and
pressure contain equal numbers of molecules," altho only
a hypothesis, is generally referred to as "Avogadro's
Law." It is of fundamental importance to chemistry. He
also stated that the relative weights of gaseous molecules
may be determined by measurement of the relative weights
of equal volumes of the gaseous substances — that is, by
comparison of gaseous densities; and that the number of
gaseous volumes interacting indicates the relative number
of molecules interacting, and similarly the volume of the
compound gas formed when compared with that of the
constituents gives the number, whole or fractional, of
elementary molecules entering into the composition of one
compound molecule.

Avogadro's conclusions produced practically no effect at
the time they were promulgated, and fifty years passed by
before they were received with due recognition. These
conclusions of Avogadro are sometimes credited to the
French mathematician Ampere (1775-1836), but the mem-
oir of the latter did not appear until 1814, and is much
less important than that of Avogadro.

While Davy and Gay-Lussac were conducting their val-
uable investigations, an important literary-chemical event,
most impressive and attractive in nature, occurred when
William Prout (1785-1850) advanced his hypothesis of
the genesis of the elements.

In 181 5, in a paper upon the relations between the spe-
cific gravities of bodies in the gaseous state and their atom-
ic weights, Prout stated that he had often observed the
close approximation to round numbers of many of the
weights of the atoms. From the table at his command he
further deduced that all elementary numbers, hydrogen
being considered as 1, are divisible by 4, except carbon,
nitrogen and barium, and these are divisible by 2, appear-
ing, therefore, to indicate that they are modified by a
higher number than unity or hydrogen. He considered

200 CHEMISTRY

the other number might be 16, or oxygen, and that pos-
sibly all substances were composed of these two elements.

A short time after, in 1816, he expressed the following
views: "If the views we have ventured to advance be
correct, we may almost consider the itpoorr) v\rj of the an-
cients to be realized in hydrogen, an opinion, by the by,
not altogether new. If we actually consider this to be the
case, and further consider the specific gravities of bodies
in their gaseous states to represent the number of volumes
condensed into one, or, in other words, the number of the
absolute weights of a single volume of the first matter
{itftoDzr] v\r}) which they contain, which is extremely prob-
able, multiples in weight must always indicate multiples in
volume and vice versa and the specific gravities or ab-
solute weights of all bodies in a gaseous state must be
multiples of the specific gravity or absolute weight of
the first matter, because all bodies in a gaseous state,
which unite with one another, unite with reference to this
volume."

Prout's conjecture was taken up by Thomas Thomson,
who, being carried away by the attraction of simplicity,
became the advocate of a philosophical speculation con-
trary to experimental facts, and even perceived in it a
fundamental law of chemistry. Other chemists, too,
showed a predilection for "Prout's Hypothesis," and, not-
withstanding the fact that Berzelius and Turner demon-
strated its untenability, some exact investigators as late
as 1840 betrayed an inclination to some of Prout's views.
In fact, some writers of the present day consider that
there may be a kernel of truth concealed in it, and, al-
tho it has suffered numerous reversals, it is still revived
at intervals.

CHAPTER XI

BERZELIUS AND THE DEVELOPMENT OF THE ATOMIC THEORY

Complete success had rewarded the exertions of La-
voisier, and, through the efforts of Proust, Richter, Dal-
ton, Gay-Lussac, and Davy, the spirit of order was creep-
ing in on all sides, but it was exceedingly fortunate for
chemistry that an investigator with the sense of coordina-
tion that Berzelius possessed should have made his ad-
vent just at this time, when laws required confirmation
and theories nourishment. The foundations of the new
system required extension and generalization, and how
opportune was the appearance of one who could illumine
the whole domain of chemistry. Berzelius ruled as an au-
tocrat for over a quarter of a century, and the modern
chemist can hardly over-extol his obligation to him.

Jons Jakob Berzelius was born at Wafversunda, in
Gstergotland, Sweden, on August 20th, 1779. His father
was a schoolmaster in Linkoping, and died four years
after the birth of his son, who for some time afterward
had to endure many privations.

Berzelius studied medicine at Upsala, and subsequently
practiced, but he had early acquired a devotion to chem-
istry and kept in close touch with it. He was but twenty
when he undertook his first extensive chemical research —
an investigation of the medicinal springs at Medevi, in the
neighborhood of his birthplace. A short time after, in
1802, in conjunction with Hisinger, he commenced the
examination of the action, of the electric current on vari-

202 CHEMISTRY

cus salts, with the most far-reaching results for chemistry
and for himself; for almost immediately the desire to keep
so promising a student in Stockholm induced the authori-
ties to create for him a new academic position, that of as-
sisant professor of medicine, botany and pharmacy at the
University of Stockholm.

In 1807, he was installed in the chair of medicine and
pharmacy, and also taught chemistry at the Military
College from the year 1806. In 1815, he accepted the chair
of chemistry in the Chirurgico-Medical Institute of Stock-
holm, where he accomplished the researches which made
him famous, and where his lectures enabled him to impress
his views upon the rising generation of chemists. Among
his pupils may be mentioned Heinrich and Gustav Rose,
Mitscherlich, Wohler, Christian Gottlob Gmelin, Magnus,
Mosander, Svanberg and Sefstrom.

From the year 1818, when he was nominated permanent
secretary to the Stockholm Academy, of which he had
been a member since 1808, and more particularly after
1832, when Mosander succeeded him in his chair, Berze-
lius devoted himself to literary work with a subservience
which has hardly been equaled from a utilitarian stand-
point by any chemist either before or after him. He died
on the 7th of August, 1848.

Berzelius was an exceptional observer, and a most ac-
curate and operose investigator, exhibiting very close at-
tention to details. It is difficult to render an account of
his achievements, as they extended over almost the entire
field of chemistry and produced reforms of great impor-
tance.

And one must not forget that the laboratory in which
Berzelius accomplished his famous researches was small
and imperfectly equipped. To give Wohler's description
of his first visit to it:

"No water, no gas, no hoods, no oven, were to be seen ;
a couple of plain tables, a blowpipe, a few shelves with
bottles, a little simple apparatus, and a large water-barrel

BERZELIUS AND THE ATOMIC THEORY 203

whereat Anna, the ancient cook of the establishment,
washed the laboratory dishes, completed the furnishings
of this room, famous throughout Europe for the work
which had been done in it. In the kitchen which adjoined,
and where Anna cooked, was a small furnace and a sand-
bath for heating purposes."

Berzelius introduced many improvements in analytical
chemistry. It was he who first employed far smaller
amounts of substances than the large quantities recom-
mended by Klaproth, who introduced the spirit-lamp which
bears his name, thereby rendering the incineration of fil-
ter-paper and the ignition of precipitates facile, and who
worked out many new methods of analysis. Among the
latter were his plan of decomposing silicates by the aid
of chlorine. He enriched mineralogy by many analyses of
minerals and mineral waters, and in a number of these
— e.g., those of platinum ores — he devised new methods
of separation.

Berzelius was the first to characterize minerals as being
in every respect "chemical compounds," and he classified
them similarly to substances prepared artificially. He was
also able to demonstrate that the doctrine of chemical pro-
portions, and consequently the atomic theory, was applica-
ble to minerals.

The close attention which Berzelius gave to details re-
sulted in the discovery of selenium (1817), thoria
(1828), and, in conjunction with Hisinger and independ-
ent of Klaproth, he discovered ceria (1803). He also
discovered many new chemical compounds, among which
were the compounds of selenium with hydrogen and oxy-
gen, and some molybdenum compounds; isolated the ele-
ments silicon (1810), zirconium, and tantalum (1824) ;
and extended the knowledge of the platinum metals.

Passages in the works of Berzelius indicate that he
regarded the firm establishment of the doctrine of chemi-

204 CHEMISTRY

cal proportions, and, in conjunction with this, the deter-
mination of the atomic weights of the elements and the
constitution of chemical compounds, as his main task. To
quote from his "Lehrbuch der Chemie," fifth edition:

"I resolved to make the analysis of a number of salts
whereby that of others might become superfluous. ... I
soon convinced myself by new experiments that Dalton's
numbers were wanting in that accuracy which v/as requi-
site for the practical application of his theory. ... I
recognised that if the newly arisen light was to spread, it
would be necessary to ascertain with the utmost accuracy
the atomic weights of all elementary substances, and par-
ticularly those of the more common ones. Without such
work, no day would follow the dawn. This was therefore
the most important object of chemical investigation at the
time, and I devoted myself to it with unresting labor. . . .
After work extending over ten years ... I was able in
1818 to publish a table which contained the atomic weights,
as calculated from my experiments, of about 2,000 simple
and compound substances."

In the years 1812 to 1816, Berzelius investigated the
stages of oxidation of most of the metals and metalloids
then known, and, by determining the composition of these
oxides, confirmed the law of multiple proportions. His
analytical work greatly surpassed that of Dalton, and in
the rules established for his guidance in deciding the num-
ber of atoms in a given compound or molecule, he exhib-
ited a greater knowledge ; still, his rules were, in some re-
spects, arbitrary and unsatisfactory.

He took oxygen =100 as his standard, giving as his
reason for this preference the following:

"To refer the other atomic weights to that of hydrogen
offers not only no advantages, but has, in fact, many in-
conveniences, seeing that hydrogen is very light and is
seldom a constituent of inorganic compounds. Oxygen,
on the other hand, unites all the advantages in itself. It
is, so to speak, the center-point round which the whole

BERZELIUS AND THE ATOMIC THEORY 205

of chemistry revolves." This view is, again, at the pres-
ent time held by many chemists, who take 16 as the atomic
weight of oxygen, and base the atomic weights of all the
other elements upon this number.

Berzelius began his work at the time when Wollaston
was attempting, by his use of the term equivalents, to elim-
inate the question of atoms. Thomson was employing the
standard oxygen = 1, considering that this number would
give more of the atomic weights as whole numbers, and
failing to perceive that the law of volumes had any partic-
ular significance from the atomic standpoint.

Berzelius, however, perceived in the law of volumes a
corroboration of the atomic theory, and allowed himself
to be guided by it in his views upon the number of atoms
in chemical compounds, and, consequently, upon the nu-
merical values of the atomic weights. His "volume the-
ory" contained the attempt to combine Gay-Lussac's law
with the atomic theory. He set forth the atomistic view,
which he had himself put into shape under the influence
of the law of volumes, definitely and conclusively in two
papers. He started with the assumption that in the case
of every simple substance, when it was in the gaseous
form, one volume corresponded with one atom, and, there-
fore, made use of the designation "volume atoms" for
those smallest particles. Wherever it was practicable, he
attempted to measure the volumes of the combining sub-
stances, and from these deduced the atomic numbers. The
analysis of the compound, in which the volumes of the
elementary constituents were known, led him to the true
determination of the atomic weights of the latter. For ,
example, from the fact that water consists of two volumes
of hydrogen and one of oxygen, he deduced the atomic
composition of water which holds at the present day, to-
gether with the relative atomic weights of oxygen and hy-
drogen; and from the mode of formation of carbonic ox-
ide and carbonic acid he arrived at the true composition

206 CHEMISTRY

of these compounds, and at the atomic weight of carbon,
and so forth.

Still, the use which Berzelius made of Gay-Lussac's law
was too limited to free him from the necessity of employ-
ing rules for deciding the number of atoms in compounds.

In 1818, Berzelius gave a table of atomic weights which
contained values which compare favorably with those of
other observers. Nine years later he published another
table which brought his atomic weights still closer to those
now current.

The reason given by Berzelius for halving in 1S26 many
of the atomic weights assigned to the metals in 181 8 was
as follows:

"It is known that the oxide of chromium contains three
atoms of oxygen. Chromic acid for the same number of
chromium atoms contains twice as much oxygen, which
would be six atoms; but in its neutral salts chromic acid
neutralizes an amount of a base containing one-third as
much oxygen as it contains itself, a relation found to hold
in the case of all acids with three atoms of oxygen — e.g.
sulphuric acid and sulphates. In order to harmonize the
multiple relation between the amount of oxygen in the
oxide and in the acid, it is most probable that the acid con-
tains three atoms of oxygen to one atom of chromium, and
the oxide three atoms of oxygen to two of chromium.
Isomorphous with the oxide of chromium are those of
manganese, iron and aluminium ; these also we know to
contain three atoms of oxygen, and consequently must rep-
resent them as containing two atoms of the radicle. But
if the ferric oxide consists of 2Fe + 3O, the ferrous oxide
is Fe + O, and the whole series of oxides isomorphous
with it contains one atom of the radicle and one atom of
oxygen."

Thus we see that E. Mitscherlich's law of isomorphism
— that compounds of analogous composition and contain-
ing the same number of atoms crystallize in the same crys-
talline form — announced in 1819, and which Berzelius re-

BERZELIUS AND THE ATOMIC THEORY 207

garded as 4<the most important since the establishment of
the doctrine of chemical proportions," was an aid in test-
ing his atomic weight determinations, for, according to
him, isomorphism indicated similarity in atomic consti-
tution.

Berzelius further showed that with the exception of
cobalt and silver the law of specific heat justified the
change made in 1826. This law was advanced in 1819 by
P. L. Dulong and T. A. Petit, who, in investigating the
specific heats of the metals and other bodies, reached the
important conclusion that these were very nearly inversely
proportional to their atomic weights. Multiplied by their
atomic weights, the specific heats gave a constant quan-
tity. This resulted in the law as stated by them : the atoms
of the different elements have the same capacity for heat.
It is not difficult to perceive that by means of the specific
heat one could readily approximate to the true atomic
weight, and arrive at a decision as to which of two or
more possible figures represented the true weight.

There were exceptions to the law which have been ex-
plained only in late years. However, the law was ex-
tended to simple chemical compounds, and proved of great
assistance after it was more fully understood. Berzelius
opposed the acceptance of it at first, in part, because it
would necessitate a revision of his table of atomic weights,
and might endanger the accepted views as to some of the
atomic relations. He gradually gave up this position,
however, when the law was confirmed by other workers,
and more accurate determinations were made than the
first ones of Dulong and Petit.

Berzelius substituted for Dalton's geometrical symbols
a more convenient system of chemical notation, which, to
give his own words, "might facilitate the expression of
chemical proportions, show briefly and clearly the number
of elementary atoms in each compound, and after the
determination of their relative weights, present the results

208 CHEMISTRY

of each analysis in a simple and easily retained manner."
The atom of each element was represented by the initial
letter of its Latinized name, a second letter being added
when two elements had names beginning with the same
capital. An index number was added when more than one
atom was present

A compound was thus represented by placing the proper
number of these symbols side by side. Thus, H is hydro-
gen, CI is chlorine, and HC1 is hydrogen chloride. Ber-
zelius assumed the existence of certain double atoms
(where two atoms of an element occur together). These
were indicated by a mark across the symbol ; thus H with
a stroke through it, followed by O, was water, or, as it is
slow written, H20. For convenience' sake, an atom of
oxygen was often indicated by a point or dot, thus :

Carbon Dioxide, C ; "Nitrous Acid," N ; Potassium Nitrate, KN„

These symbols were a great advance over those sug-
gested by Dalton, which were diagrammatic and quite un-
practical. Dalton, however, criticized the system of no-
tation of Berzelius, saying that "Berzelius' symbols are
horrifying; a young student in chemistry might as soon
learn Hebrew as make himself acquainted with them."

Berzelius adopted dualism as the basis of his chemical
system. He extended the term atom so that it included
what he regarded as compound atoms, which were built
up of two parts, each of which might be a simple atom
or several atoms, in which each of the two parts acted as
a single simple atom. This was the dual structure, which
dominated all of his views with regard to chemical phe-
nomena, and for more than a decade held a preeminent
position in chemistry. Berzelius seemed to have formed
this idea of dualism from his observations upon the vol-
umes of gases. For a certain number of these gases the
equivalent is formed of two atoms. This was true not

BERZELIUS AND THE ATOMIC THEORY 209

only of hydrogen, but of nitrogen, chlorine, and others, in
the form of vapor. The atomic weights of these bodies
represent also the specific gravities, or the weights of one
volume compared with one volume of the standard; but
since it requires two volumes of nitrogen, two volumes of
chlorine, etc., to form the first stage of oxidation with
oxygen, two volumes of nitrogen, etc., represent the equiv-
alents of these bodies compared with oxygen. Berzelius
considered that these atoms, therefore, were united two
and two, and called them the double or compound atoms.

A uniform method of considering compounds dualistic-
ally became possible to a still greater degree in the light
of electro-chemical phenomena, and Berzelius introduced
this into chemistry and established it.

Davy had inclined to the assumption that electrical
processes and the phenomena of chemical affinity arose
from a common cause. His electro-chemical theory was
characterized by the axiom that the small particles of sub-
stances which have an affinity for one another only be-
come oppositely electrified upon contact. The researches
of Berzelius, however, caused the abandonment of this
principle, while otherwise many of Davy's original ideas
were retained. Davy advanced ideas as to the manner in
which he considered chemical and electrical phenomena
to be related, but he never succeeded in producing a theory
which might serve as the basis of a chemical system.
This was accomplished by Berzelius, and therefore his
views are of greater importance in the development o£
chemistry than those of Davy are. To quote from A.
Ladenburg's "Lectures on the History of Chemistry" :

"According to Berzelius, it is not only when two sub-
stances are brought into contact that electricity is gener-
ated, but it is a property of matter; and in every atom,
two oppositely electrical poles are assumed. These poles
do not, however, contain equal quantities of electricity.
The atoms are unipolar, the electricity of the one pole pre-
dominating over that of the other; and thus every atom

210 CHEMISTRY

(and therefore every element) appears Lo be either posi-
tively or negatively electrical. In this respect it is possi-
ble to arrange the elementary substances into a series, so
that each member is always more electro-negative than
the next succeeding one. Oxygen stands at the top and
is absolutely electro-negative, while the other substances
are only relatively positive or negative according as they
are compared with elements which come before them or
after them in the electrical series. This series does not
constitute a table of affinities in the GeofTroy-Bergman
sense ; and it does not express the affinity of the individual
substances for oxygen, for example. Berzelius has not
forgotten Berthollet's teaching, that affinity is not of a
constant character and independent of the physical condi-
tions, as he supposes this unipolarity to be; and he is also
well aware that oxygen can be removed from metallic ox-
ides by carbon or sulphur — that is to say, by other electro-
negative substances. With him, affinity depends princi-
pally upon the intensity of the polarity — i.e., upon the
quantity of electricity which is contained in the two poles."
This is variable, however, especially with changes of tem-
perature, and, generally speaking, is increased by furnish-
ing more heat, which explained why certain combinations
only occurred at a high temperature.

Chemical combinations of the elements or compounds
consisted, according to Berzelius, in the attraction of the
dissimilar poles of the small particles and in the conse-
quent neutralization of the different electricities. When
positive electricity predominated in the original substance,
then an electro-positive compound resulted, and vice versa.
If the electricities neutralized one another, then an elec-
trically indifferent product was the result. Oxygen, as the
most electro-negative element, served Berzelius here as
the standard by which to determine the kind of polarity of
the various elements. Those elements which yielded basic
compounds with oxygen, even altho only their lowest ox-
ides were basic, were classed as electro-positive, and those

BERZELIUS AND THE ATOMIC THEORY 211

whose oxides were acids as electro-negative. Following
this principle he arranged the simple substances in a se-
ries, in which oxygen as the first member was followed by
the other metalloids, while hydrogen formed the bridge
between the latter and the metals, the whole ending with
sodium and potassium.

Such conceptions formed the substance of his electro-
chemical theory, which constituted the basis of the dual-
istic theory of chemical composition. Berzelius estab-
lished it as follows :

"If the electro-chemical views are accurate, it follows
that every chemical combination depends wholly and solely
upon two opposite forces, namely, the positive and the
negative electricities, and that every compound must be
composed of two parts, united by the effects of their elec-
tro-chemical reactions, since there is not any third force.
From this it follows that every compound substance, what-
ever the number of its constituents may be, can be di-
vided into two parts, of which the one is positively and
the other is negatively electrical. Thus, for example, sul-
phate of soda is not composed of sulphur, oxygen, and
sodium, but of sulphuric acid and soda, each of which can,,
in turn, be separately divided into an electro-positive and
an electro-negative constituent. In the same way, also,
alum cannot be regarded as immediately composed of its
elementary constituents, but is to be looked upon as the
product of the reaction of sulphate of alumina, as negative
element, with sulphate of potash, as positive element; and
thus the electro-chemical view justifies what I have said
with respect to compound atoms of the first, second, third,
etc., orders."

In the year 1819, when Berzelius contributed a complete
exposition of his electro-chemical theory, he was con-
vinced that all acids contained oxygen. In his view water
assumed in hydrated acids the role of a weak electro-
positive constituent, and in metallic hydroxides that of a

212 CHEMISTRY

weak electro-negative one; the hydrates of sulphuric acid
and of cupric oxide, therefore, received the formulae —

+ - ■+-

H2O.SOs CuO.H20.

The binary conception, which had already been applied by
Lavoisier to acids and bases, and even by Rouelle to salts,
thus received the strongest support from the electro-chem-
ical theory, and was materially developed as a result.

Finally, however, the theory of the oxygen acids, based
on the tenet established by Lavoisier, was abandoned by
chemists during the second decade of the nineteenth cen-
tury, as a knowledge of facts in opposition to it aug-
mented, and at last Berzelius convinced himself of the
existence of acids free from oxygen, at which time the
unadaptable system of dualism began to decline in favor.
It had explained, however, the mysterious chemical force,
even tho the identification of chemical affinity with elec-
trical polarity was one not justified by the facts at hand,
and dominated chemistry for two decades.

As a result of the efforts of Berzelius, chemistry was
now in the possession of a comprehensive theory of chem-
ical reaction, a rational and systematic nomenclature, and
a large quantity of experimental data. He was responsi-
ble for a solid basis in the laws of constant proportions
and multiples, and the table of atomic weights which he
published in 1827 was remarkably accurate, the determina-
tions approaching the more exact work of the present
lime. These contributions equipped chemistry for the
period of remarkable extension in the accumulation of
data and in the formulation of theory which the past
eighty years have witnessed.

Mention has been made of the law of Dulong and Petit
and of the law of Mitscherlich. The exceptions to the
former, exhibited by many of the non-metals in a greater
or lesser diminution of the atomic heats, have only in

BERZELIUS AND THE ATOMIC THEORY 213

some measure been explained in recent years by the
proof that the specific heats of such elements vary greatly
with the temperature. In the case of simple chemical
compounds, a relation was soon found between their spe-
cific heats and atomic weights by Neumann in 1831, who
said:

"I find that for compound substances a simple relation
exists between the specific heats and the stoichiometric
quantities; and I call stoichiometric quantities the amounts
of substances which, as for instance in the case of the
anhydrous carbonates, contain the same amount of oxy-
gen, while in the case of sulphur compounds the amount
of sulphur is the measure of the stoichiometric quantity,
For chemically similar substances the specific heats are
inversely proportional to the stoichiometric quantities; or
what comes to the same thing, the stoichiometric quanti-
ties of chemically similar substances have the same heat
capacity. The investigation of the carbonates first led me
to the discovery of this law."

Regnault, who extended the empirical basis of the law
of constant atomic heat in 1840, while engaged in investi-
gations on the specific heats of compounds corroborated
Neumann's result, but it was reserved for Kopp in 1865 to
definitely prove that the connection between the specific
heat and the composition of a compound holds in the per-
fectly simple and general manner enunciated by Petit and
Dulong, and that heat capacity is of the nature of an ad-
ditive property.

The law of Mitscherlich was the outgrowth of coordi-
nating physical form with chemical composition, a ques-
tion which, until the time of Eilhard Mitscherlich (1794-
1863), had been attacked entirely from the crystallo-
graphic side.

In 1801, Abbe Haiiy (1743-1822), the founder of the
science of crystallography, produced a system of mineral
classification based first on their crystalline character, and
secondly on their chemical composition. His guiding prin-

214 CHEMISTRY

ciple was that every difference in the fundamental form of
a crystal implied difference in its chemical composition.

This supposed law was supported by numerous facts,
but there were also on record well-denned and undoubted
exceptions. As far back as 1772, Rome de ITsle had ob-
served that copper sulphate and ferrous sulphate crystal-
lize from a mixed solution in the form of the latter, and
in 1788 Klaproth established the chemical identity of
rhombohedral calcite and rhombic aragonite.

Mitscherlich was the first to recognise definitely the
relation between crystalline form and chemical constitu-
tion. He explained the occurrence of isomorphous crys-
tals in substances of different nature by demonstrating
that they possessed a similar chemical composition. For
instance, he found, on examining the salts of phosphoric
and arsenic acids, that only those of analogous composi-
tion and containing equal amounts of water of crystalliza-
tion were isomorphous. His subsequent investigations of
selenates and sulphates, of the isomorphism of magnesium
and zinc oxides, and of iron, chromium and aluminium*
salts, confirmed the intimate connection existing between
crystalline form and chemical composition. Primarily,
after making those observations, Mitscherlich was of opin-
ion that isomorphism depended chiefly on the number of
the elementary particles, but he soon became convinced
that the chemical nature of these had also to do with it.

The importance of Mitscherlich's work met with imme-
diate recognition, and data in support of the law were
quickly accumulated. With regard to its deductive appli-
cation, it is employed for purposes of classifying the ele-
ments and of atomic weight determinations. From the
isomorphism of the salts of an acid of selenium with sul-
phates and chromates, Mitscherlich was led to the discov-
ery of that acid (selenic acid) ; and his recognition of the
isomorphism with potassium sulphate of the green potas-
sium salt of a manganese acid, and of the isomorphism
with potassium perchlorate of the red potassium salt of

BERZELIUS AND THE ATOMIC THEORY 215

another manganese acid, has revealed the true composi-
tion of these two acids.

It has been mentioned how the isomorphism of sulphates
and chromates induced Berzelius to modify the formula
of basic chromic oxide and to a subsequent halving of the
atomic weights of most of the metals. He still adhered to
the idea that the amounts of the elements contained in
equal gaseous volumes were proportioned to their atomic
weights. However, this assumption was soon invalidated
by the remarkable results of an investigation which ex-
ercised such a marked influence on the views of many
chemists that it must be described at this point.

This was the work of Jean Baptiste Andre Dumas
(1800-1884) on the atomic weights. In 1827, Dumas pub-
lished a paper entitled "Memoir on some points of the
atomistic theory," in which he stated that "The object of
these researches is to replace by definite conceptions the
arbitrary data on which nearly the whole of the atomic
theory is based."

Dumas showed that the conception of the equivalent
cannot be employed as the basis of a system, because it
loses its significance when it is extended further than to
acids, to bases, and to other substances which closely re-
semble each other (oxides and sulphides) ; and, particu-
larly, that it becomes quite obscure when the attempt is
made to identify the equivalent with the combining weight,
since very many substances can combine in several pro-
portions. For example, 8 parts of copper are combined
with 1 part of oxygen in cuprous oxide, while for 8 parts
of copper, 2 parts of oxygen are contained in cupric oxide.
Calculated from these numbers, the equivalent of copper,
referred to that of oxygen as unity, is 8 or 4.

In order to confirm his ideas, Dumas adopted Avoga-
dro's hypothesis as a basis, and devised in 1827 an admir-
able method for the determination of vapor densities.

He considered that the determination of the density of
vapors and gases, elementary as well as compound, was

216 CHEMISTRY

necessary to elucidate the question of the composition of
the elementary molecule. But his practice did not agree
with his theory; he and his contemporaries argued from
the premise that the vapor densities of elements are pro-
portional not only to their molecular weights, but also to
their atomic weights, which of course involved the un-
warranted assumption that all* elementary gaseous mole-
cules are composed of the same number of atoms — i.e., of
two.

He was successful in elaborating a method for conduct-
ing determinations of this kind at high temperatures, and
used it for ascertaining the relative densities of the vapors
of iodine, phosphorus, sulphur, mercury, etc. His results,
from which he anticipated confirmation of his views, in-
duced him to abandon them. He found the density of
phosphorus vapor to be twice as great, and that of sul-
phur vapor to be three times as great as he had previously
assumed, while that of mercury vapor was only one-half
of what he had supposed. In view of these facts he began
to doubt; in fact, he declared that even the simple gases
do not contain, in the same volume, the same number of
chemical atoms. According to him, the assumption could
still be made that there is the same number of molecular
or atomic groups present in equal volumes of all gases ;
but that this is only a hypothesis, which cannot be of ser-
vice. Dumas was obliged to admit that Gay-Lussac's law,
when applied in the way he had applied it to the determi-
nation of atomic weights, furnished erroneous results.
Hence he believed that it could not be employed for this
purpose, and he abandoned Avogadro's hypothesis.

Berzelius also was able no longer to maintain the law
of volumes so far as its application in atomic weight de-
terminations was concerned, and confined his proposition
to the permanent gases.

The reform which Dumas had aimed at was, therefore,
without result, and, if anything, he had merely introduced
obscurity into the atomic weight system of Berzelius.

BERZELIUS AND THE ATOMIC THEORY 217

As a result, chemists regarded Avogadro's law with in-
difference. The law of Dulong and Petit was shown also
to have some unexplained exceptions, and Mitscherlich,
by his further discovery of dimorphism, had thrown much
doubt upon his law of isomorphism. Consequently, at the
close of the thirtieth year of this century the atomic theory
was regarded by many chemists as either disproved or
excluded to a very hypothetical position.

Even Gay-Lussac and Liebig doubted whether it was
possible to determine the relative weights of the atoms
with certitude, and would have left the atomic weights
out of consideration, substituting the establishment of
equivalents. Leopold Gmelin, however, was at the head
of the movement to supplant the system of Berzelius by
the equivalents of Wollaston.

According to Gmelin, there was no strict distinction be-
tween mixtures and compounds, and this demonstrates that
he did not believe in the real existence of atoms. Two
substances, especially when they possess only a weak affin-
ity for each other, can combine, according to him, in an
infinite number of proportions ; but the greater the affinity,
the greater is their tendency to combine in few propor-
tions only. These proportions then stand to each other in
simple relations. "There can, therefore, be assigned to
every substance a certain weight in which it combines
with definite weights of other elements. This weight is
the stoichiometric number, the chemical equivalent, the
mixture weight or atomic weight, and so on. Compounds
are composed in such proportions that one mixture weight
of one substance is united to %, }i, y2, 2/z, Ya, i, 1^2, 2,
2^, 3, 4, 5, 6, 7, or more mixture weights of the other."
According to Gmelin, Gay-Lussac's law runs as follows:
"One measure of an elastic fluid substance combines with
1, 1%, 2, 2.y2, 3, $y2, and 4 measures of the other."

Gmelin's table of equivalents is well known. It ran :
H = 1, O = 8, S = 16, C = 6, etc. Water was written
HO, and in formulae generally the attempt was made to

218 CHEMISTRY

replace by simplicity what they had lost in conception
and in purpose. As Ladenburg observes, "Chemistry was
to become a science of confined observation — indeed al-
most to description alone. Skill in manipulation was all
that was required ; speculation was banished as dangerous.

"It had come to this, then: Inorganic chemistry, in
connection with physics, had not been able to maintain
the conception of the atom."

By the assistance of the growing science of organic
chemistry, however, the theories of chemistry were res-
cued and advanced, and the atomic theory was reintro-
duced. But reference must be made to the status of the
atomic theory in England at this time.

In England in the 1833 edition of Edward Turner's
"Elements of Chemistry" the atomic theory is referred to
as follows:

"In consequence of the satisfactory explanation which
the laws of chemical union receive by means of the atomic
theory it has become customary to employ the term atom
in the same sense as combining proportion or equivalent."

A discovery of great importance was made in 1834,
when Michael Faraday (1794-1867), professor in the
Royal Institution of London, who had been engaged in
studying quantitatively some changes produced by the
passage of a current of electricity, detected the connection
which existed with the combining numbers of the elements,
and thereby deduced his law of electrical equivalents.

Faraday made the observation that the same galvanic
current decomposed electrolytes—^., water, hydrochloric
acid and metallic chlorides — in such a manner that equiva-
lent amounts of hydrogen or metal were separated at the
negative pole, and the corresponding quantities of oxygen
or chlorine at the positive. He classified those facts to-
gether under the title of "The Law of definite Electro-
lytic Action." In the determination of electro-chemical
equivalents he perceived a sure auxiliary means for ad-
justing chemical atomic weights in doubtful cases.

CHAPTER XII

THE DEVELOPMENT OF ORGANIC CHEMISTRY

Lavoisier showed that organic substances were com-
posed principally of carbon, hydrogen, and oxygen, to-
gether with nitrogen, and sometimes sulphur and phos-
phorus. He had observed that an element was capable
of forming more than one oxide, and from this he con-
cluded that organic radicals deported themselves similarly.
He consequently regarded sugar as the neutral oxide "d'un
radical hydro-carboneux," and oxalic acid as its higher
oxide. He even hazarded the conjecture that the fatty
oils, which he considered to be hydrocarbons, might actu-
ally constitute organic radicals in the free state, and
might, by oxidation, be converted into neutral oxides and
vegetable acids.

Among Lavoisier's other investigations in organic chem-
istry, his research on the process of vinous fermentation
is worthy of mention. He expressed the results in the
form of the equation —
3 oz. 7 gros of water + 2 lbs. 8 oz. sugar produce, on

fermentation,
1 lb. 7 oz. 5 gros 18 grains of alcohol + 1 lb. of carbonic
acid.

"In this equation," says he, "there is only sugar whose
constitutional parts are unknown to me. I know the com-
position of water, of alcohol, and of carbonic acid, and
nothing is easier than to substitute these values in the
equation established and then deduce the constituent parts
of sugar."

219

220 CHEMISTRY

However, Lavoisier did not regard organic chemistry
as a separate division of the science. He classed all acids
together, and, like Lemery (1675), subdivided them into
mineral, vegetable, and animal acids. With a few ex-
ceptions, the immediate followers of Lavoisier followed
the same plan, and the division of chemistry into inor-
ganic and organic chemistry was not generally adopted
until it became clear that several compounds occur both
in the vegetable and animal kingdom, and therefore that
no difference existed between vegetable and animal chem-
istry. In this connection the work of M. E. Chevreul
(1786-1889) should be emphasized, as it was his investi-
gations which demonstrated that many of the fats and
acids and other substances, occurring in both kingdoms,
were identical.

However, for some time subsequently considerable
doubt prevailed as to the boundary of inorganic and or-
ganic chemistry. One reason for this was that inorganic
substances, as well as some which had to be considered as
organic, gave on analysis numbers which demonstrated
that their composition was in accordance with the laws
of constant and multiple proportions. As Berzelius stated
in 181 1, the majority of organic substances, however,
appeared not to obey these laws, and consequently he un-
dertook to decide this question by the analysis of a large
number of them. After years of labor, and after improv-
ing the appliances and methods of organic analysis, he
finally obtained results which proved that altho most or-
ganic compounds possessed a much more complicated com-
position than the mineral compounds, yet they obeyed the
laws of constant and multiple proportions. He adopted
the views of Lavoisier, and said (Schorlemmer) :

"After we have got a clearer insight into the difference
existing between the products of organic and inorganic
nature, and the different manner in which their ultimate
components are united with each other, we find this dif-
ference consists really in the fact that in inorganic nature

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222 CHEMISTRY

all oxidized bodies contain a 'simple radical/ while all
organic substances are 'oxides of compound radicals/ The
radicals of vegetable substances consist generally of car-
bon and hydrogen, and those of animal substances of car-
bon, hydrogen, and nitrogen."

In his ideas as to these radicals he was especially influ-
enced by the research of Gay-Lussac upon cyanogen, in
which he showed that this radical played the role of an
element. Attempts were multiplied to discover the vari-
ous organic substances having complex groupings of atoms
which performed as elements. Thus, Gay-Lussac regarded
alcohol as ethylene and water. Dobereiner considered ox-
alic acid as carbonic acid and carbon monoxide. As Ber-
zelius pointed out, this was opposed to the electro-chemical
theory, and there was danger of confusion and error.

The search for the proximate constituents in organic
substances induced a rapid development of the science,
leading especially to many efforts at definitely determining
the chemical constitution of these bodies. One of the most
important of the discoveries in the third decade was that
of isomerism. This was viewed as an error by chemists
at first, so little prepared were they to believe that bodies
similarly composed could be chemically and physically
different. It was in the year 1823 that Liebig announced
that his analysis of silver fulminate yielded the same re-
sults as Wohler had found in the preceding year for his
silver cyanate. He was confident that his figures were
correct, and believed that Wohler must have made a mis-
take. A careful repetition of the analyses showed him
that both were correct, and so it was proved that two
bodies, totally unlike, could and did have the same com-
position. Gay-Lussac saw that the only explanation of
this lay in the different mode in which the elements were
combined. In 1826, Berzelius reported on Liebig's ful-
minate of silver as follows :

"This substance has been made the subject of a new
joint investigation by Gay-Lussac and Liebig, and the

ORGANIC CHEMISTRY 223

result is of the utmost interest. Fulminate of silver dried
at ioo° loses all its water, and in 3 experiments they found
between 16.87 and 17-3%% cyanogen, the mean being
17.16%. The silver oxide was separated by hydrochloric
acid, and was found to be 77.528% of the weight of the
salt. These quantities add up to 94.688%. The deficiency
is only 5.312%, a quantity absolutely equal to that of the
oxygen in the silver oxide. Hence the salt was composed
of 77.528% of silver oxide and 22.472% of cyanic acid;
but this result is identical with that obtained by Wohler in
his analysis of silver cyanate, in spite of which agreement
between the analytical results the two substances have not
the same properties. The chief difference is that Wohler's
cyanate of silver, when heated by itself, does not explode,
but only burns with moderate intensity; and further, that
when decomposed by acids it is completely changed into
carbonic acid and ammonia . . . while fulminic acid
has explosive properties, and gives ammonia and prussic
acid when its salts are decomposed by oxyacids. These
facts point unquestionably to a difference in composition."
("Jahresbericht," 1826.)

In 1825, Michael Faraday announced the results of his
work on the hydrocarbons from oil-gas, when he demon-
strated the existence of butylene, an isomer of ethylene.
In 1827, Berzelius commented on this discovery in part as
follows :

"The two gases are of like constitution, but ... a
given volume of the one contains twice as many simple
atoms as does the other, and this produces a certain dissimi-
larity in physical and chemical character. . . . Definite
knowledge concerning this phenomenon would be of such
significance in the doctrine of the composition of vege-
table and animal bodies, and would have so important a
bearing on organic chemistry, that it must not be accepted
as demonstrated until its truth has been subjected to the
most severe proof. It is not my intention to dispute the
possibility or the actuality of such a fact, but I maintain

224 CHEMISTRY

that before accepting it with confidence the relation ob-
served by Faraday must be found in a number of other
cases."

In 1832 and 1833, Berzelius formally adopted the addi-
tion to the doctrine of chemical composition rendered
necessary by these observations, and suggested his clas-
sical classification of the new phenomena, concluding as
follows :

"But since it is requisite that we should be able to
express our conceptions by definite and appropriately
chosen terms, I have proposed to call substances of the
same composition and of different properties 'isomeric,'
from the Greek ivonzprjc, (composed of equal parts)."

The general designation isomerism has since then been
retained. Berzelius soon saw himself necessitated to de-
fine more strictly the meaning to be attached to this word,
and therefore he distinguished between polymerism and
metamerism, as special cases of isomerism.

The ideas of Berzelius with regard to the probable
cause of isomerism in organic compounds are clearly
shown in many of his statements ; in his view isomeric
compounds are those in which the atoms of the elementary
constituents have grouped themselves differently into com-
pound radicals. "The isomerism of compounds in itself
presupposes that the positions of the atoms in them must
be different." And it appears that he considered it pos-
sible to determine the mutual relations of the atoms in
their compounds.

At the period that is now reached, to quote Carl
Schorlemmer, "we find Berzelius laying stress again on a
difference between organic and inorganic substances, first
pointed out by Gmelin (1817), and according to which
the latter, but not the former, could be prepared arti-
ficially. Berzelius was of opinion that within the sphere
of living nature the elements obeyed laws totally differ-
ent from those ruling in inanimate nature. It was then
commonly supposed that the compounds found in plants

ORGANIC CHEMISTRY 225

and animals were produced by the action of a so-called
Vital force,' and that altho they might be changed into
other compounds none of them could be prepared arti-
ficially from their elements. Thus, grape-sugar, a com-
pound widely distributed in the vegetable kingdom, by
fermentation yielded alcohol, which could be converted
into ether, acetic acid, and many other compounds; and
all these were considered to be organic, as none of them
could be prepared synthetically."

It was Friedrich Wohlers synthesis of urea which
finally removed this obstacle to the growth of organic
chemistry. In 1828, Wohler made the discovery that
cyanate of ammonia, which was regarded as an inorganic
compound, could be converted into urea, a substance hith-
erto known only as a product of animal metabolism. This
was the first synthesis of an organic compound, and is
generally referred to as marking the beginning of scientific
organic chemistry. Yet it remained an isolated fact for
a long time and failed to shake the belief in a "vital force,"
a belief which was maintained during the lapse of many
years.

In 1830- 183 1, Liebig perfected and simplified the opera-
tions for the ultimate analysis of organic compounds, and
this to such a degree that his processes have not required
any essential alterations to fit them to modern require-
ments. These perfected methods enabled Liebig to carry
out his famous researches in Giessen, work which renders
a brief biographical mention of this master fitting.

Justus Liebig was born at Darmstadt on May 12, 1803.
The fact of his father being a dealer in dye-stuffs brought
him early into contact with laboratory problems. At fif-
teen years he was sent to a neighboring town to learn
the business of apothecary. But pharmacy was not chem-
istry, as Liebig was beginning to understand it, so he
entered the University of Bonn. Here was certainly
change, much "ingenious contemplation," but no chemis-
try. He traveled to Erlangen, where he heard lectures,

226 CHEMISTRY

read books, and at nineteen obtained a degree. Then
his chance came. His ability being made known to the
Grand Duke of Hesse-Darmstadt, he was provided with
the means of studying in Paris. There worked those
giants, Gay-Lussac, Thenard, Chevreul, Vauquelin, and
Dulong; nor was it long before Liebig was received into
the laboratory of Gay-Lussac. Liebig had meanwhile won
the appreciation of Humboldt; his was a personality that
inspired immediate and warm friendships. "Of slender
form was he, a friendly earnestness in his regular fea-
tures, great brown eyes with shady eyebrows which at-
tracted one instantly." It was Humboldt who, in 1824,
brought him as extraordinary professor of chemistry to
Giessen. Two years later he was elected to the ordinary
professorship, which office he held for the next twen-
ty-six years. The dull little town of Giessen became
famous; the fires of Liebig's laboratory acted as a beacon
light, attracting chastened spirits from the four quarters
of the civilized world. For it was not long before the
master had roused the Darmstadt Government to build
a laboratory where all might come and seek and find.
And the movement spread. Liebig, through his pupils,
tinctured the world; there were other governments than
that of Darmstadt, and soon there were other public
laboratories than that of Giessen. In 1845 Liebig was
created Baron. In 1852 he accepted a call of the Bava-
rian Government to the Munich professorship of chemis-
try. Warmly appreciated by the Bavarian court, entering
into the social and philosophical life of the university
town, courted by all the scientific circles of Europe, yet
continually fighting weakening health, Liebig passed the
remainder of his life in Munich. He died in 1873.

Liebig devoted his full powers of mind to organic
chemistry, but did not neglect inorganic chemistry, as
his work on the compounds of silicic acid, alumina and
antimony clearly shows. His work in physiological and
agricultural chemistry rendered him a general benefactor

ORGANIC CHEMISTRY 227

of mankind, and, to quote A. W. von Hofmann, "If we
sum up in our minds all that Liebig did for the good of
mankind, in industries, in agriculture, and in the laws
of health, we may confidently assert that no other man
of learning, in his course through the world, has ever
left a more valuable legacy behind him."

Writing in 1810, Gay-Lussac and Thenard gave, as a
reason for the slow progress of animal and vegetable
chemistry, the inadequacy of the methods of organic analy-
sis. In their "Recherches physico-chimiques," which ap-
peared in 181 1, they gave an exhaustive description of a
new method of organic analysis, the results of analyses
of sugar, starch, gum arabic, milk sugar, wood, and
mucic, oxalic, tartaric and acetic acids, as well as of oils,
resins and waxes, and the following generalizations made
from the results of their work:

1. A vegetable substance is always acid when it contains
more oxygen than will form water with the hydrogen.

2. It will be always resinous, oily, or alcoholic when it
contains less oxygen than suffices the hydrogen.

3. The body will be neither acid nor resinous, but analo-
gous to sugar or ligneous fiber, when the oxygen and
hydrogen are present in just the proportions to form
water.

This classification was, of course, of little service, but
it was suggestive, and altho no proper classification was
possible at this time, the interpretation of Gay-Lussac and
Thenard gave a stimulus to the study of the constituents
of organic compounds.

Berzelius explained in 1819 that his electrochemical the-
ory could not be extended to organic chemistry, because
under the influence of the vital force the elements there
possessed entirely different electrochemical properties. In
decay, putrefaction, fermentation, etc., he observes phe-
nomena which he regards as demonstrating the tendency
of the elements to return to their normal condition. He

228 CHEMISTRY

did not, at that time, as yet consider it possible to regard
all organic substances as binary groups. Dualism was,
indeed, extended as far as possible ; the oxygen compounds
were looked upon as "oxides of compound radicals, which,
however, do not exist free, but are wholly hypothetical,"
a mode of regarding the matter which was especially
applicable to the acids.

In 1838, Liebig defined a compound radical, enunciating
three characteristics and making use of cyanogen as an
instance: "We term cyanogen a radical because (1) it is
the unchanging constituent of a series of compounds; (2)
because it is capable of replacement in these by simple
substances; and (3) because in those cases where it is
combined with one element this latter can be exchanged
for its equivalent of another element." At least two of
the conditions here adduced had to be fulfilled in order
that an atomic complex might be stamped as a radical.
The existence of these conditions, moreover, could only
be established by the most minute investigation of the
chemical behavior of organic bodies. That is to say, the
nature of the radicals assumed in the latter could only
be arrived at from the study of their reaction- and decom-
position-products.

This radical theory aroused considerable interest, and
chemists of eminence were attracted to the task of inves-
tigating the constituents of compounds related to one
another. Thus, the research of Bunsen upon the cacodyl
compounds, which formed one of the strongest supports
of the theory, may be mentioned.

Robert Wilhelm Bunsen (1811-1899) enriched every
branch of chemistry by his valuable researches. He cre-
ated the gas analysis methods of to-day, with Kirchhoff
he developed spectrum analysis into one of the great
branches of to-day, and in his investigations in analytical
and inorganic chemistry and in geochemistry he showed
himself a pioneer in the science.

Bunsen's researches on the cacodyl compounds resulted

ORGANIC CHEMISTRY 229

in the proof that the so-called "alkarsin," the product of
the distillation of acetate of potash with arsenious acid,
contained the oxide of an arseniuretted radical AS2C4H12
(H = 1, C = 12, As = 75), this radical remaining un-
changed in a long series of reactions of that oxide, and
being even itself capable of isolation. This "compound
element" containing arsenic (an unusual constituent of
organic bodies) was thus shown to be a true radical.

Inasmuch as the radical was supposed to be constituted
of atoms held together by stronger forces than those which
united the group to other atoms, it attained a real signifi-
cance in the minds of chemists; and as the dualistic theory
and the theory of compound radicals became more solidly
intrenched in chemistry, they rendered the atomic theory,
on which, of course, they were founded, an essentiality,
and even after dualism was discredited the only changes
were in the ideas as to the nature of the ultimate particles,
or atoms.

About this time, however, facts became known which
could not be brought into accord with the radical theory,
and as a result doubts were expressed as to the theory of
dualism; but it was the discovery of the principle of
substitution which actually caused this theory to succumb,
and paved the way for the so-termed unitary theory.

The conception of equivalence might have led to that
of replacement or substitution, since the quantities of two
acids were equivalent when they saturated the same quan-
tity of a base. The acid in a neutral salt could thus be
replaced by its equivalent without the neutrality being
interfered with. The word "replacement" received fur-
ther justification after Mitscherlich had studied the phe-
nomena of isomorphism. It could then be said that cer-
tain elements in a crystal might be replaced by others
without alteration of the crystalline form. Such substi-
tutions possessed the peculiarity, however, that they were
not connected with any proportions by weight, and it
may thus appear all the more remarkable that they should

230 CHEMISTRY

render important assistance in the determination of atomic
weights. The hypothesis underlying the phenomena of
isomorphism was that one atom could only be replaced by
one other; that is to say, that the numbers of the atoms
in isomorphous compounds must be identical. Since
chemically similar substances had alone been compared,
an extension of the prevailing views, based on the phe-
nomena of isomorphism, would have been quite possible;
but this class of phenomena had never led to any attack
upon the system.

In the bleaching of wax by means of chlorine, Gay-
Lussac had observed that for every volume of hydrogen
eliminated, an equal volume of chlorine was taken up. He
had also found the same thing in the action of chlorine on
hydrocyanic acid. In the course of their investigation
of the benzoyl compounds, previously referred to, Wohler
and Liebig, when acting with chlorine upon bitter almond
oil, had discovered benzoyl chloride; and they expressly
remark that this substance is produced from the bitter-
aimond oil by two atoms of chlorine taking the place of
two of hydrogen.

In the year 1834 Dumas, a propos of an investigation on
the mutual action between chlorine and oil of turpentine,
but more especially of his work upon the production of
chloral from alcohol, condensed into two empirical rules
the facts with regard to substitution, for which he pro-
posed the designation metalepsy (i.e., exchange, fiErak^ii).
These were not intended to comprize a theory of substi-
tution, as his first utterances on the subject show, but
only to give expression to the facts. They were as fol-
lows:

"When a compound containing hydrogen is exposed to
the dehydrogenizing action of chlorine, bromine, or iodine,
it takes up an equal volume of chlorine, bromine, etc.,
for each atom of hydrogen that it loses.

"If the compound contains water, it loses the hydrogen
of this without replacement."

ORGANIC CHEMISTRY 231

The second of these rules was deduced from the trans-
formation of alcohol into chloral, and was thus intended
to explain the mode of formation of the latter and at the
same time to support Dumas' view of the constitution of
alcohol, the latter being regarded by him as a compound
of ethylene and water.

By means of various examples, Dumas further endeav-
ored to prove the general validity of the laws which he ad-
vanced. In establishing the correct composition of the
Dutch oil he pointed out that the chloride of carbon ob-
tained from it by means of chlorine, and examined by
Faraday, supplied a new argument in favor of the accu-
racy of his views. He also found similar support in the
action of chlorine on hydrocyanic acid, on bitter almond
oil, etc.

However, he was unsatisfied with this, and extended
his statement to one of greater significance, regarding
oxidations as cases of substitution, as, for instance, the
conversion of alcohol into acetic acid.

While Dumas limited himself at this time (1835) to
condensing the known facts into the above laws, Auguste
Laurent (1807-1853), a pupil of Dumas, went further,
and considered the nature of the compounds resulting
from substitution and made a comparison of them with
the original ones. He was thereby induced to enunciate
the proposition that the structure and chemical nature
of organic compounds are not materially changed by the
entrance of chlorine and the separation of hydrogen. This
law is the core of the substitution theory proper, of which
Laurent was the propounder.

Laurent endeavored to give expression to the observed
facts, and to the hypotheses based upon them, in the so-
called nucleus theory. This theory is of importance in the
science (altho it never obtained any general recognition
in it) because chemists have adopted, if in another form,
many of the ideas embraced by it, and also because it was
adopted by Gmelin as the basis of the organic portion of

232 CHEMIS1RY

his excellent handbook. On this account the chief points
of Laurent's doctrines will be stated.

According to Laurent, all organic substances contain
certain nuclei, which he calls either fundamental ("radi-
caux fondamentaux") or derived. The former are com-
pounds of carbon with hydrogen, in which the mutual
proportion of the number of the atoms is a simple one
(i to 2, 3, 4, etc., 2 to 3, etc.). For any definite propor-
tion, several nuclei exist which are polymeric among
themselves. Besides, these fundamental radicals are so
chosen that the hydrogen and carbon atoms contained in
them occur in pairs.

The derived nuclei ("radicaux derives") were produced
from the original nuclei, either through the substitution
of hydrogen by other elements or by the addition of other
atoms.

This theory manifestly sprang from the old radical the-
ory, but with an important change, namely: the radical
here is not an unchanging group of atoms, but it is a
combination which can be changed through the substitu-
tion of equivalents. It is but a step in the evolution of
the modern theory, as seen in the benzene nucleus.

Trie nucleus theory was regarded as unscientific by
Liebig, and Berzelius opposed it, but the latter was moved
before long by Malaguti's investigation of the simple and
compound ethers — in which he demonstrated that the chlo-
rine atoms again played the part just as the hydrogen
atoms they had displaced — and, as Armitage observes in
his "History of Chemistry," he "saw that here was the
thin edge of a most potent wedge, which, unless imme-
diately removed, might break down the whole fabric of
that chemical theory he had spent so much on building."

Before Laurent, in conjunction with Gerhardt, had
again brought forward his ideas in a more perfect form,
Dumas entered the lists to do battle against the radical
theory, and, with this, against the dualistic idea in general.
His beautiful discovery of "chloracetic acid" afforded him

ORGANIC CHEMISTRY 233

the immediate occasion for this, and he now gave in his
adhesion to Laurent's opinions, which formerly he would
have nothing to do with.

By the action of chlorine, in sunlight, upon acetic acid,
Dumas had obtained a crystalline substance whose com-
position could be expressed by the formula GCI6H2O4, and
which could, therefore, be regarded as acetic acid, CJHLCX,
in which six atoms or volumes of hydrogen were replaced
by six atoms of chlorine. The interesting and important
part of this reaction lay in the properties of the new com-
pound, which Dumas called chloracetic acid. This acid
had the same saturating capacity as acetic acid, so that
Dumas was able to assert that by the entrance of chlorine
in place of the hydrogen, the chief character of the com-
pound was not altered; or, as he expresses himself, "that
in organic chemistry there are certain types which per-
sist even when an equal volume of chlorine, bromine, or
iodine is introduced into them in place of the hydrogen
which they contain."

He was thus led to the same view which had already
been taken up by Laurent, but his theory of types (1839)
was hardly a mere application of the views of Laurent.
The principal propositions of this theory were as follows:

1. The elements of a compound body can, in many
cases, be replaced by equivalents of other elements or of
compound bodies which play the part of simple ones.

2. If such a substitution occurs equivalent for equiva-
lent, the compound in which the replacement has taken
place retains its "chemical type," and the element or group
which has been taken up plays in it the same part as the
element which has gone out.

The term "chemical type" failed to satisfy Dumas, how-
ever, and he permitted it to merge into that of "mechani-
cal type," which included all compounds which might be
supposed to be formed from one another by substitution,
even tho they differed in properties.

Berzelius could not accept these views, and when Dumas

234 CHEMISTRY

characterized his electrochemical theory as erroneous, an
embittered discussion ensued which lasted for years. The
proposition of Dumas that every chemical compound
forms a complete whole and cannot therefore consist of
two parts, that its chemical character is dependent pri-
marily upon the arrangement and number of the atoms,
and in a lesser degree upon their chemical nature, pro-
claimed a decided unitarism, and was therefore violently
opposed by Berzelius.

Berzelius sought to get over the difficulties which the
substitution of hydrogen by chlorine and other elements
involved, by arguing that compounds formed in this man-
ner must have a constitution different from that of the
original ones. But here he entered upon dangerous ground,
and was thereby led, prudent investigator as he was, into
the most utter contradictions of the principles which he
had formerly held to be inviolable.

Facts now increased which went to demonstrate the cor-
rectness of the theory of substitution, and in 1842 Mel-
sens found that by the action of potassium amalgam on a
water solution of trichloracetic acid, its chlorine was com-
pletely replaced by hydrogen, acetic acid being repro-
duced. This was a discovery of the greatest import, as it
showed inverse substitution was possible, yet it did not
shake Berzelius's faith. He merely decided to look upon
acetic acid in the same way as its chlorine derivative — i.e.,
as a copulated oxalic acid with the copula methyl, C.H3,
formulating the two compounds thus:

C2H3 + CaO,-HO Acetic acid.

C2C13 + C203.HO Chloracetic acid.

This was practically giving up the fight, as by it he ac-
knowledged that the "Paarling," or copula, could undergo
substitution, and that its exact nature did not have a pre-
dominating influence in determining the nature of the
compound into which it entered. Yet Berzelius remained

ORGANIC CHEMISTRY 235

an opponent of the theory of types until his death in 1848,
and his adherents experienced great difficulty in recon-
structing radicals anew from his copulae after his death.

In 1845, A. W. Hofmann discovered the substituted ani-
lines, and observed that it appeared without doubt that
chlorine or bromine could assume the role of hydrogen in
organic compounds, taking their electro-negative charac-
ter with them into the new compounds. Liebig commented
on Hofmann's report as follows : "The author appears
to have definitely proved that the chemical nature of a
compound does not in any way depend upon the nature of
the elements contained in it as is assumed by the electro-
chemical theory, but entirely on their arrangement." Lie-
big now turned to the unitary theory and opposed Berze-
lius's attempted explanations. Other prominent chemists,
too, became his opponents, and yet, in spite of the slight
regard in which the radical theory was held in many quar-
ters, it soon became evident that, for the investigation of
chemical constitution, the assumption of radicals, which
had been displaced by the theory of types, was indispen-
sable.

In the fifth decade a fusion of the radical theory with
the doctrine of types occurred on the Unitary side, and as
a result of the work of Auguste Laurent and Charles Ger-
hardt (1816-1856) the older theory of types was trans-
formed into the new theory.

In 1839, Gerhardt published his views on the process
which occurs when an element is replaced by a group of
atoms. In his opinion it was not a substitution, but a
union of two residues to a unitary whole and not an artic-
ulated binary compound. He termed these groups of
atoms "le reste" or "le restant," and later developed his
theory of residues, according to which a residue could
have the composition of a compound radical but was not
present as such in a compound. His conception of radicals
soon replaced the older views, and its introduction into the
theory of types induced a fusion of both theories.

236 CHEMISTRY

The first advance in this direction was made in 1849,
when C. A. Wurtz (1817-1884) discovered the compound
ammonias. Hofmann found another method of preparing
the bases discovered by Wurtz, and the "typical" view
of these bases was first arrived at by means of his inves-
tigations. He showed that in the amine bases, as well as
in aniline, the two hydrogen atoms of the amide could be
replaced by alcohol radicals. A. W. Williamson (1824-
1904) then demonstrated that in a similar manner the alco-
hols and their ethers could be referred to the type water.
He also pointed out that acetic acid must have a consti-
tution similar to that of alcohol, and proposed to call the
radical C2H3O, obtained from ethyl by oxygen substitution,
othyl. Gerhardt, employing a reaction similar to that
by which Williamson had prepared the ethers, discovered
the anhydrous acids ; and chemists began to attempt to find
among the more simple inorganic compounds other types
for organic compounds, thereby giving rise to Gerhardt's
theory of types. According to this theory, the organic
compounds of known constitution can be classified under
four types, namely, hydrogen, hydrochloric acid, water,
and ammonia; for example, the hydrocarbons, aldehydes,
and the acetones or ketones were classed in the first type ;
the halides (chlorides, bromides, iodides, and fluorides) in
the second ; the alcohols, ethers, monobasic acids, and sul-
phides and hydrosulphides in the third; and the amines
were placed in the fourth type.

The general arrangement and the comprehensive char-
acter of Gerhardt's system leave nothing to be desired.
Even altho views have been considerably changed and
cleared up since that time, and altho one is compelled,
from the modern standpoint, to look upon the types as in-
sufficient, still Gerhardt's services to chemistry can never
be questioned. Unfortunately he did not live to witness
the reception which was extended by many chemists to the
views laid down by him in the fourth volume of his "Lehr-
buch der Organischen Chemie." The type theory was

ORGANIC CHEMISTRY 237

particularly extended by the assumption of "mixed types,"
which was intended to render clear the relations of many
organic compounds to two or more types. This was par-
ticularly applied by August Kekule.

It was also in the fifth decade that Hermann Kolbe
(1818-1884) revived the much-ridiculed copulae. He and
Sir Edward Frankland (1825-1899) were followers of
Berzelius, and held similar views to Gerhardt, but as they
did not accept at that time either the new atomic weights
or the existence of radicals containing oxygen, they made
use of other formulae.

Kolbe united the conclusions deduced from his re-
searches with the declining theory of Berzelius; he in-
dued the latter with new life by casting aside whatever of
it was dead and replacing this by vigorous principles.
From his own and other investigations he came to the
conclusion that the unalterability of radicals, as taught by
Berzelius, could no longer be maintained, since the facts
of substitution had to be taken into account. He did, in-
deed, adopt Berzelius' hypothesis of copulae, but attached
another meaning to these, since he allowed that they ex-
ercized a not inconsiderable influence upon the compounds
with which they were copulated.

He endeavored to make this theory have a deeper bear-
ing upon the constitution of organic compounds, and, as a
result of the influence of several important researches, his
ideas regarding copulae and conjugated compounds were
altered several times. His theoretical views and, with them,
the revived radical theory reached their completed form in
a contribution published in 1859.

The principal result of Kolbe's speculations is given as
follows : "Organic compounds are all derivatives of inor-
ganic, or result from the latter — in some cases directly — by
wonderfully simple substitution-processes." This idea runs
through the 1859 contribution and is illustrated by numer-
ous examples from the wide field of organic chemistry.

CHAPTER XIII

VALENCE, THE CONSTITUTION OF ORGANIC COMPOUNDS, AND
THE DEVELOPMENT OF STEREO-CHEMISTRY

In the preceding chapter mention has been made of the
influence exerted by Frankland on the views developed by
Kolbe respecting the constitution of organic compounds.
It was Frankland who, in his now classical paper —
"A New Series of Organic Compounds containing Metals"
— demonstrated that the pairing of the radicals with the
elements was to be explained on the ground of some char-
acteristic property of the atoms, and thus he expelled the
useless part of the radical theory (1852).

Frankland observed that "When the formulae of inor-
ganic chemical compounds are considered, even a super-
ficial observer is struck with the general symmetry of their
constitution; the compounds of nitrogen, phosphorus, an-
timony and arsenic especially exhibit the tendency of these
elements to form compounds containing 3 or 5 equivalents
of other elements, and it is in these proportions that their
affinities are best satisfied ; thus in the ternal group we have
NOa, NH3, NI3, NS3, P03, PH3, PCI,, Sb03, SbH3, SbCl,,
As03, AsH3, AsCl3, etc. • and in the five atom group N05,
NH4O, NHJ, PO5, PHJ, etc. Without offering any hy-
pothesis regarding the cause of this symmetrical group-
ing of atoms, it is sufficiently evident, from the examples
just given, that such a tendency or law prevails, and that,
no matter what the character of the uniting atoms may be,
the combining power of the attracting element, if I may be
238

VALENCE 239

allowed the term, is always satisfied by the same number
of these atoms."

He then proceeded to represent the organo-metallic com-
pounds obtained by formulae which brought out the an-
alogy with the inorganic types, from which they were
thought to have been derived.

From his work on the organo-metallic compounds,
Frankland developed the doctrine of the valence of the
elements, the germ of which may be recognized in much
that has gone before, particularly in the law of multiple
proportions, which stated that the elements show different
yet definite stages in their combinations.

The so-called doctrine of the polybasic acids contributed
materially to the development of ideas upon the subject of
the saturation capacity of the atoms. Gay-Lussac, Gme-
lin, and others inclined to the assumption that the atoms
of the various metallic oxides contained one atom of oxy-
gen united to one atom of metal, and that these oxides'
combined with one atom of acid to form neutral salts.
Berzelius also, after 1826, considered that this combining
proportion was the rule. However, by Thomas Graham's
famous investigation of the phosphoric acids (1833), it
was shown that a view so simple as this, according to
which almost every acid was looked upon as monobasic,
was untenable. Graham proved that in the ortho-, pyro-,
and meta-phosphoric acids, for each "atom" of phos-
phorus pentoxide there were three, two and one "atoms"
of "basic water," these latter being replaced by equivalent
amounts of metallic oxides.

The saturation capacities of these acids were in this
way shown to be dependent upon the amounts of "basic
water" which entered into their constitution. Liebig ex-
tended this to many other acids and distinguished between
mono-, di-, and tri-basic acids, and the property was re-
ferred to as the "basicity" of the atoms, a term which^
with the ideas inherent in it, clung for some time to the
theory of valence. In 1857, f°r example, the terms "basic-

24o CHEMISTRY

ity," "valency," and "atomicity" were used as synonymous,
and as the measure of the number of hydrogen atoms that
could be replaced or held in combination.

The idea of "basicity" was soon extended to the com-
pound organic radicals. In 1855, C. A. Wurtz (1817-
1884), a pupil of Liebig and Dumas, showed that glycer-
ine (C3H8Os) may be regarded as the hydrate of the radi-
cal C3H5. Four years previous A. W. Williamson (1824-
1904) had expressed the view that a large number of com-
pounds may be referred to the type of water, the mono-
basic acids to one molecule, and the polybasic acids, which
are of greater molecular complexity, to a condensed water
type. He wrote

3 O = acetic acid .... jt2 02 = sulphuric acid.

Wurtz now showed that the composition of glycerine
could be represented by the formula

CsH/"

03, which was similar to the formula by which,
H3
in accordance with the ideas of Williamson, ordinary

(PO)'"
p' ocphoric acid Oa was represented.

H,

Gerhardt in his "Traite de Chimie Organique" stated
that "In order to compare the radicles among them-
selves, I propose to refer them all to the radicle of hydro-
gen, and consequently I name them monatomic, diatomic,
triatomic according to the quantity of hydrogen which
they are capable of replacing in the type H20 — i.e., accord-
ing to whether they are equivalent to 1, 2, or 3 atoms of
hydrogen — so for instance 1'n alcohol and in ether:

VALENCE 241

C2H5 C2H6

o o

H C2H5

CsHb, the radicle ethyl, is monatomic because it replaces H
(one atom of hydrogen) in the type water."

The terms "monatomic" and "polyatomic" had been em-
ployed much earlier, but in a different sense. Thus, in
1827, Berzelius called fluorine, chlorine, etc., "polyatomic,"
because several atoms of these halogens unite with a sin-
gle atom of another element. In 1833, Gaudin de Saintes
used the same terms to express the number of atoms in a
molecule, in which sense they were used by Gmelin, Clau-
sius, and Odling. Williamson attached the idea of ca-
pacity for saturation or atomicity of the radical to the
number of hydrogen atoms capable of substitution, and
the notion of atomicity was soon extended to the known
compound radicals and played an important part in the
theories of types, etc., which obtained in organic chemis-
try.

Frankland's speculations concerning the substitution
value of radicals compared with that of elementary atoms
were of great importance, yet they did not meet with
immediate approval.

By 1858, however, the valence theory had made rapid
progress. In this year August Kekule first deduced the
valence of carbon from its simplest compounds, declaring
it to be tetravalent. This had already been recognised by
Kolbe and Frankland, if not expressly stated by them.
But Kekule rendered further and much greater service by
inquiring into the manner in which two or more of these
tetravalent carbons were united with one another. The
doctrine of atomic chains, open and closed, sprang from
this, and the domination of the structural idea in chemis-
try became complete.

In the same year and independently of Kekule, M. S.

242 CHEMISTRY

Couper arrived at conclusions almost identical with those
of Kekule.

Both Kekule and Couper expressed with absolute def-
initeness the axiom that the "atomicity of the elements"
was to be made use of for arriving at the constitution of
chemical compounds. The idea of the term "atomicity"
had without any doubt been introduced by Frankland six
years previous to this. The further development of the
above axiom and its utilization in the theory of the link-
ing of atoms was carried out mainly by Kekule, and in the
succeeding years also by Butlerow and Erlenmeyer.

While the radical and type theories were attempts at
securing an idea of the structure of chemical compounds,
it was the valence theory which rendered it possible to
furnish a lucid answer to the question as to the composi-
tion of such bodies; and, especially after the year 1870,
the determination of the constitution of complex mole-
cules became the higher aim of chemistry.

Some rudiments of systematic classification had before
this been introduced into organic chemistry, and these
classificatory beginnings were of great assistance in the
erection of structural chemistry. In 1836, Laurent, when
he brought forward his nucleus series, arranged organic
compounds in series, and it was in 1841 that Gerhardt
entered on a research to discover some general law which
might suggest an all-sufficing system of classification, and
the following year he was ready with his "ladder of com-
bustion"— with its highest rung cerebral matter, its low-
est carbonic acid, water and ammonia — to enfold the whole
science of organic chemistry. He soon found, however,
that this arrangement, according to mere complexity of
composition, was no sufficient classification, so he betook
himself to another line of inquiry, A note of triumph
seems to ring through the following lines from the preface
to his "Precis de Chimie Organique," published in 1844:
"I have succeeded in establishing homologous series.

VALENCE 243

. . . These have indicated to me the means of classify-
ing organic substances in natural families, and of dis-
posing them on a kind of combustion ladder." As a mat-
ter of fact, it was only the word "homology" that Gerhardt
could claim as his own. Two years earlier J. Schiel had
shown that a very simple relation existed between the
alcohols then known, that their radicals might all be rep-
resented by the general expression nR -f- H, R suggesting
the group C2H2(C = 6); moreover, in the same year
Dumas had demonstrated the existence of a similar rela-
tion between the several members of the fatty acids
known to him. Yet Gerhardt generalized from this fact
of homology and proved the possibility of predicting the
existence of terms unknown in his series.

Many systems of classification were suggested during
the sixth decade, the classification by series as that of
Schiel and Dumas, that of series depending upon for-
mulae, series depending upon chemical behavior, and many
other systems. The lack of agreement among chemists,
however, as to the formulae belonging to the different
compounds, as to the relative weights of the molecules,
the atomic weights, and even the number of atoms, pre-
vented a general acceptance of any of the classifications
proposed until Kekule established the fact of the tetrava-
lence of the carbon atom, showed the difference between
saturated and unsaturated compounds, and deduced his
chain formulae.

About i860 Frankland's views regarding a saturation
capacity peculiar to the elements were accepted either
delitescently or expressly by most chemists, but it was
considered that this saturation capacity, under certain
circumstances, might be a varying one. In 1856, Gerhardt
had stated that nitrogen was sometimes triatomic and
sometimes pentatomic. This view was also held by Frank-
land, Wurtz, Williamson and Couper, and the latter three
considered that the valence was also variable in the cases
of many other elements. Kolbe thought that it must be

244 CHEMISTRY

assumed that a constant valency was characteristic of a
few elements and a varying one characteristic of many
more, since he perceived in it another expression
for the law of multiple proportions and nothing was
known concerning the cause of valence. As early as 1854,
Kolbe had concluded that each element possessed a maxi-
mum saturation capacity, but that lower stages of satura-
tion might exist along with this; and toward the begin-
ning of the sixties, several chemists who took an active
part in developing the structure theory expressed the same
opinion in a more definite manner. Erlenmeyer, in partic-
ular, maintained in various papers, and afterward in his
"Lehrbuch der organischen Chemie," that each element
possesses a maximum valency, or that each is furnished
with a definite number of "Affinivalenten" or affinity-points
("Affinitatspunkten"), only part of these, however, being
in many cases combined with the affinity-points of other
elements.

Kekule's theory of the constant valence of the elements
could not withstand the critical examinations to which it
was subjected, however, and in the course of the last
forty years the majority of chemists have adopted the
view that the atoms of most of the elements possess a
varying saturation capacity, varying according to the
conditions.

Altho the structure theory was unable to accomplish the
extreme expectations which aimed at a knowledge of the
spacial arrangement of the atoms, it possessed none the
less great practical value. The development of organic
chemistry since the middle of the sixth decade shows in
fact that, through the aid of the structural hypothesis,
the discovery of new modes of formation and decomposi-
tion of compounds, the recognition of the relations exist-
ing between various classes of bodies, and, especially, the
interpretation of the constitution of numerous organic
substances became possible. Kekule's theory of the aro-

VALENCE 245

matic compounds forms the most striking proof of this.
In 1865-1866, taking the quadrivalence of carbon as his
principle, Kekule called attention to the fact that in the
fatty compounds the carbon atoms are linked together by
one valence of each. In the case of benzene, the next
simplest assumption was made, in accordance with which
the carbon atoms are linked together by one and two
valencies alternately, so as to form a closed chain or ring.
Of the twenty-four affinities of the six carbon atoms,
eighteen are employed in linking carbon to carbon, thus :

6 6

—.4 + — .2 = 18
2 2

Six valencies then remain which are satisfied by the six
hydrogen atoms of the benzene. Hence, according to
Kekule, benzene may be represented by means of a regular
hexagon whose sides are composed.of single and of double
lines alternately, the CH groups occupying the corners,
thus :

H

/\

HC CH

II I

HC CH

H

Kekule and his pupils, together with many other chem-
ists who had busied themselves with the derivatives of
benzene after this view had been published, now directed
their efforts to comparing all the known and rapidly in-
creasing observations bearing upon this class of bodies
with the deductions drawn from the above formula, and
therewith to proving by actual experiment the admissibil-

246 CHEMISTRY

ity of the assumptions on which the formula was based.
The result was that Kekule's anticipations were realized
and his hypothesis substantiated.

In 1866, Kekule had stated that "What is wanted is that
the largest possible number of substitution products of
benzene should be prepared by the most diverse methods;
that they should be most carefully compared with regard
to isomerism; that the modifications so found should be
counted. ..."

And in the 1867 edition of his text-book, he called at-
tention to a number of cases of isomerism which at that
time had received no explanation. Among these we find
that of ethylene chloride with ethylidene chloride; of
acetal with diethyl glycol; for maleic and fumaric, for
mucic and saccharic acids, the last effort of his philosophy

had only found him the two formulae ^ 2 [• 02 and

68 6 l 02 respectively. Kekule instanced, too, those

bodies which only differed in their effect on polarized
light, the tartaric, the malic and camphoric acids, and the
amyl alcohols.

It was owing to these cases of isomerism that structural
formulae could not be assigned. In some cases a greater
number of isomeric bodies were known than could possibly
be accounted for by any arrangement of the atoms in
formulae upon a plane surface, retaining, of course, the
accepted views as to valence, etc., and since these isomers
differed principally in certain physical properties, they
were at first termed "physical isomers." The study of
these resulted in the consideration of the arrangement of
atoms in space — the chemistry of space, or Stereochem-
istry, in which branch of the science an extended view of
atomic grouping was essayed.

Modern stereochemistry was anticipated by Emmanuel
Swedenborg in 1721, when he made an attempt to ex-
plain the phenomena of chemistry and physics on geo-

VALENCE 247

metrical principles in his Trodromus Principorium rerum
Naturalium sive Novorum Tentaminum Chymiam et
Physicam Experimentalem Geometrice Explicandi,' and
similar beginnings were made by Johann Barchusen ten
years earlier.

In 1864 Carius, who first used the term "physical iso-
merism," explained it as follows :

"I have tentatively expressed a view as to the cause of
what I call 'physical isomerism.' Substances [which ex-
hibit this property] yield, under the same or nearly the
same conditions, products which are either identical or
physically isomeric. According to our present views, I
think it improbable that such substances should have their
atoms differently arranged — i.e., that they should be meta-
meric. But it is quite conceivable that in the formation
of physical isomers differences of condition may cause
the production of substances with the same arrangement
of the atoms within the molecule, but with a different
aggregation of these molecules; and that thereon depends
the difference in their properties. . . . Thus we must
consider as certainly only physically isomeric a large num-
ber of the substances distinguished by the difference o£
their action on polarized light, such as the two modifica-
tions of amyl alcohol, the tartaric acids, the malic acids,
etc."

This explanation was inadequate, and in 1873 Johannes
Wislicenus (1835-1902), who succeeded Kolbe as pro-
fessor of chemistry at Leipzig in 1885, suggested the sub-
stitution of the term "geometrical isomerism" for "physi-
cal isomerism." He had been engaged in an investigation
of the varous modifications of lactic acid, and had found
that the ethylene lactic acid, or hydracrylic acid, prepared
by Beilstein by treating /2-iodo-propionic acid with silver
oxide, possessed properties different from those of the
ethylene lactic acid obtained from ethylene cyanhydrin.
This difference was so marked that he thought it might
be explained by assigning the two acids different structural

248 CHEMISTRY

formulae. The first was optically inactive, while the sec-
ond (paralactic acid) was dextro-rotary. This one point
of difference appeared hardly sufficient to "make it neces-
sary to assign to paralactic acid a structural formula other
than that of the fermentation lactic acid." It seemed
much more likely that here, at any rate, were cases of
what Carius had called "physical," but what Wislicenus
now proposed to call "geometrical isomerism." He said,
"My conclusion for the present is to declare paralactic
acid and the fermentation lactic acid as most probably only
geometrically isomeric. Their great similarity, even iden-
tity in all chemical properties, the ease of transformation,
on heating, of the first into the second, and their differ-
ences, particularly in optical behavior, may all alike be
explained on this basis.

"Concerning the special 'how' of this explanation, I am
engaged in experimental investigations."

The next year J. H. Van't Hoff furnished an answer
to this. However, before giving his exposition, mention
must be made of Louis Pasteur's (1822-1895) pioneer work
in this field. Pasteur studied the various tartrates crystal-
lographically, and showed that there are four isomeric tar-
taric acids, viz. : racemic acid, inactive tartaric acid, and
right and left rotating tartaric acids. He showed, more-
over, that the two latter acids crystallize in similar, but
in oppositely built-up (enantiomorph) forms; that they
both rotate a ray of polarized light through equal angles,
but in opposite senses ; and that when mixed in equal quan-
tities they yield optically inactive racemic acid. Further,
he succeeded in decomposing racemic acid again into the
two optically active tartaric acids by three different
methods.

Pasteur established the correlation of molecular disym-
metry and rotary power in these investigations, and it
remained to discover under what conditions the disym-
metry could obtain in two molecules structurally identical.
This was undertaken in 1874 by J. H. Van't Hoff in Hoi-

VALENCE

249

land and J. A. Le Bel in France, who in papers published
that year offered an explanation practically the same for
cases of isomerism which could not be included under the
theories of the time.

Van 't Hoff states that in general Le Bel's original paper
and his were in accord, but that while Pasteur's researches
formed Le Bel's starting point, he took for his own ''Ke-
kule's law of the tetravalence of carbon, [to which he]

C02H CO..H C02H

Tartaric Acids. III., meso-tartaric acid.

I., active acid. II., other active acid. (Inactive, divisible.)
IV., racemic acid.
(Inactive, indivisible.)

added the hypothesis that the four valencies are directed
toward the corners of the tetrahedron in the center of
which is the carbon atom." To quote from Freund's
'Study of Chemical Composition,' "Van't Hoff introduced
no fundamental change in, or addition to, the original
valency hypothesis; a two-dimensional representation of
molecular structure could not at any time have been con-
sidered as really true to the actual occurrence, but it was
legitimate to use it, because of its greater simplicity, as
long as it proved adequate to the purpose. And with this
recognition and restriction we continue to use plane struc-
tural formulae in the majority of cases." Van 't Hoff, fol-
lowing up the suggestion that may be found implied in
Pasteur's paper, and that was explicitly stated by Wish-

250 CHEMISTRY

cenus, introduces into the science the consideration of the
arrangement of atoms in space :

"Stereochemistry [from crrspeo^ solid], in the re-
stricted sense of the word, comprizes chemical phenomena
which demand a consideration of the grouping of atoms
in space."

Carbon compounds only were considered at first, but
the scope of the phenomena dealt with has been extended
and now includes compounds of trivalent and pentavalent
nitrogen, of tin, and of sulphur.

Van't Hoff's theory of the asymmetric carbon atom,
however, met with difficulties on its enunciation. To quote
from F. P. Armitage's "History of Chemistry" :

"When Van't Hoff enunciated his theory of the asym-
metric carbon atom, he was able to say, with much show
of truth, that all optically active substances did contain
certainly one such atom. Soon, however, were heard dis-
sentient voices. What of propyl alcohol, asked one; and
of styrolene, demanded another. The propyl alcohol owes
its activity to traces of amyl alcohol, answered Henniger;
the styrolene is impure, said Van't Hoff; and their evi-
dence was irrefutable. But Van't Hoff could not, in 1874,
maintain that the presence of one asymmetric carbon atom
necessarily implied optical activity; for secondary amyl
alcohol and its derivatives, also propylene alcohol, were
certainly inactive, yet all contained an asymmetric car-
bon atom. The problem set the stereochemists was some-
what similar to that of the relation between tartaric and
racemic acid, so happily solved years before by Pasteur.
His methods were recalled; and Le Bel soon showed that
these inactive bodies were in reality mixtures of two
optically opposite isomers, and, others helping, that in-
deed every substance with but one asymmetric carbon
atom was equally capable of 'mesotomism.' The four va-
rieties of tartaric acid had offered no difficulty; with two
asymmetric carbon atoms similarly habited there was
necessarily neutralization or duplication of optical activity.

VALENCE 251

But where two or more carbon atoms occurred, asymmetric
by union with different radicals, as in the sugars and'
their derivatives, many more cases of physical isomerism
suggested themselves, and have since been verified. With-
out doubt the asymmetric carbon atom has made a tri-
umphant progress, winning for Le Bel the Jecker prize
of 188 1, for Van't Hoff a dominant voice in the scientific
councils of the world; it will rank with the phlogiston of
Stahl, the oxygen of Lavoisier, the atom of Dalton, and
the dualism of Berzelius."

Among the most noted workers in the field of stereo-
chemistry have been A. von Baeyer, Wallach, Victor
Meyer, Riecke, Bischoff, Werner, Hantzsch, Auwers and
Overton. Even now the subject is in its infancy, and
stereochemical theories are as yet insufficiently advanced
to present a clear view of the question of geometrical iso-
merism, yet, as Ladenburg has said, "It is beyond doubt
that the founding and development of stereochemistry (a
name which originated with Victor Meyer) is the most
important thing that was accomplished in organic chem-
istry during the last two decades of the nineteenth century.
Stereochemistry possesses a significance for this period
similar to that which the foundation and introduction of
the theory of aromatic compounds possessed for the twenty-
years preceding."

CHAPTER XIV

PROGRESS IN INORGANIC CHEMISTRY DURING THE MODERN
PERIOD

A rapid growth in inorganic chemistry ensued after
the introduction of the New Chemistry by Lavoisier. A
mass of information concerning the nature of the elements
and their compounds was accumulated, and many new
bodies were discovered. However, even now, after the
accurate study of the chemical behavior of mineral sub-
stances by many careful investigators, we are still far from
a definite knowledge of the nature of all the elements and
their compounds, and new bodies are from time to time
added to the extensive series already known. In the case
of the elements, for example, Lavoisier in his 'Traite de
Chimie' mentioned twenty-six, while eighty-one are at
the present time accepted. An endeavor to sketch the
important advances in inorganic chemistry since the time
of Davy and Gay-Lussac will be made in this chapter.

Cadmium was discovered by Stromeyer in 1817 and
about the same time by Hermann. It was named by Stro-
meyer "cadmia fornicum" (furnace zinc), because it was
found in the zinc furnace, cadmia being the original name
for zinc.

In the same year lithium was discovered by Arfvedson
in petalite and spodumene. The metal was first obtained
by Bunsen and Matthiessen in 1855. The name is Greek
and means stony, and the metal was so called because it
was then supposed to be found only in rocks, and not in
the plant and animal bodies.
252

MODERN INORGANIC CHEMISTRY 253

Silicon was first isolated in 1810 by Berzelius by fusing
together iron, carbon and quartz, and Wohler showed that
it exists in the crystalline form as well as in the amorphous
state.

In 1827, Wohler isolated aluminium by the action of
potassium upon its chloride, and eighteen years later St.
Claire Deville prepared the metal on a large scale by
using sodium, while Bunsen effected its preparation by
electrolytic means. Aluminium is now prepared in quan-
tity by the electrolytic decomposition of the oxide, alu-
mina, dissolved in cryolite. Beryllium, or glucinum, was
also obtained by Wohler, who effected its isolation in
1828 by the action of potassium upon the chloride. Bro-
mine was isolated by Balard in 1826 from the mother
liquor of sea-salt, and was further investigated three
years later by Lowig; along with iodine, which was dis-
covered by Courtois in 181 1 in the ashes of sea plants,
and chlorine, it constituted the group of halogen elements
of Berzelius, since fluorine was then unknown. The lat-
ter was first isolated in 1886 by Moissau by the electrolysis
of hydrogen fluoride in the presence of potassium fluoride.

Tellurium, which had been discovered by Muller von
Reichenstein in 1782, was thoroly investigated by Berze-
lius, who discovered an element chemically analogous to
it — selenium — in 181 7.

The isolation of the metals comprising the cerium and
yttrium groups has presented numerous difficulties. Al-
tho the discovery of yttria — impure, it is true, from ad-
mixture with other earths — was accomplished by Gadolin
in 1794, and investigators have busied themselves with the
question, the chemistry of the cerium metals is not even
yet completely elucidated, and may possibly remain un-
solved for a considerable time to come. After Klaproth
and Berzelius had independently prepared cerium sesqui-
oxide from cerite, and the latter had identified this as the
oxide of a metal, Mosander discovered two new oxides
in crude yttria, the metals of which — lanthanum (1834)

254 CHEMISTRY

and didymium (1841)— he isolated. Two years later (1843)
he added to these two others, erbium and terbium, whose
existence and nature is not yet, however, definitely set-
tled, in spite of the admirable work which has been done
on the subject. This has given us a better knowledge of
yttrium, while yttria, which was formerly held to be a
homogeneous substance, has proved itself a mixture of
the oxides of various metals, of which, however, only one
or two have as yet been isolated; for example, the discov-
ery of scandium by Nilson and Cleve in 1879, and of ytter-
bium by Marignac. The most recent additions to the
knowledge of chemistry of this group of elements and
their compounds have been made by Welsbach, Drossbach,
Kriiss, Winkler, Crookes, Brauner, Baskerville, Urbain
and others. Welsbach separated didymium into praseo-
and neodymium. An analytical method has been elab-
orated for the separation of the various constituents of
the cerium, ytterbium and thorium earths, which has been
of help in the manufacture of mantles for incandescent
light burners. Quite recently Urbain has separated ytter-
bium into two other elements — neoytterbium and lutecium.
In spectrum analysis, chemistry now possesses an ex-
ceedingly valuable instrument for investigating rare
metals and earths, and its use in the last five decades has
been extensive.

Spectrum analysis has grown out of some apparently
insignificant and disconnected observations made by
Marggraf, Scheele, Herschel and others upon the light
emitted by flames colored by certain salts. The spectra
of such flames were investigated by various scientists,
among whom Talbot, Miller, Alter and Swan deserve first
mention; but it was only after Kirchhoff (in i860) proved
the definite statement — that every glowing vapor emits
rays of the same degree of refrangibility that it absorbs —
that spectrum analysis became developed by Bunsen and
himself into one of the great branches of our science.

MODERN INORGANIC CHEMISTRY 255

Its importance for analytical chemistry, especially in the
discovery of new elements, is almost beyond mention, and
it opened up a new era in chemistry.

Roscoe once said, "The spectroscope, next to the bal-
ance, is the most useful and important instrument which
the chemist possesses." Crookes has remarked, "If I
name the spectroscope as the most important scientific in-
vention of the latter half of this century, I shall not fear
to be accused of exaggeration." The very importance of
the subject prevents an entrance into any long discussion
of it here. It has come to form a distinct branch of chem-
ical science. In the hands of men like Bunsen and Crookes
it has explored the recesses of the rocks for minute traces
of hidden treasures, while with it workers like Miller,
Huggins and Lockyer have fathomed the abysses of space
and determined the constitution of the stars.

Among the elements discovered by the use of the spec-
troscope were rubidium and caesium in lepidolite and in
the Durkheim mineral water by Bunsen and Kirchhofr";
indium by Reich and Richter, in 1863, as a constituent of
Freiberg zinc blende; gallium in 1875 by Lecoq de Bois-
baudran; and thallium by Crookes in 1861. The chemical
nature of the last-mentioned metal was established by
Lamy in the same year.

The knowledge of the metals discovered in the preced-
ing era was greatly enlarged by investigations conducted
during this period. The analogues of nitrogen — phos-
phorus, arsenic, antimony and bismuth — were carefully ex-
amined, and the atomic weight which Berzelius deter-
mined for phosphorus was confirmed by Dumas, while his
atomic weight for arsenic was corroborated by Pelouze
and Dumas. The metals of the alkaline earths — barium,
strontium, calcium and magnesium, which were isolated
by Davy — were investigated by Berzelius, Marignac and
Dumas, who determined their atomic weights. Recently
Winkler found that magnesium is an excellent reducing

256

CHEMISTRY

agent for metallic oxides. Cobalt and nickel have been
the subject of researches of an important nature, mainly
because of the remarkable compounds they form — e.g.,
nickel tetra-carbonyl and the ammonio-cobaltic com-
pounds. Nickel is now extensively used in metallurgy,
especially in the production of nickel steel.

Fig. 24 — Spectroscope.
A., telescope, through which the spectrum is seen magnified ; B.,
colhmator-tube ; C, tube containing a scale ; P., prism for
dispersing the light.

The rarer metals have, of course, received considerable
attention. Uranium, which was discovered by Klaproth
in 1798, was investigated further by Peligot, Roscoe and,
lately, by Zimmermann. Molybdenum and tungsten, iso-
lated respectively by Hjelm and d'Elhujar, have become

MODERN INORGANIC CHEMISTRY 257

better known, and the acids and the complicated salts of
these have been studied by Scheibler, Marignac, Fried-
heim and Gibbs. Uranium, and, particularly, tungsten
and molybdenum are now employed extensively as steel-
hardening materials. Uranium compounds are also used
in dyeing and ceramics.

Titanium, zirconium and thorium have now become,
in the form of various compounds, particularly the oxide,
of practical importance. Thorium was discovered by
Berzelius in 1828; its oxide, thoria, is applied in the manu-
facture of Welsbach gas mantles, which consist essen-
tially of a web of 99 per cent, thoria and 1 per cent, cerium
oxide. Titanium is employed for the manufacture of
special alloys, and zirconium, as zirconia, is made use
of both in gas and electric illumination. Germanium, an
element which resembles these in some respects, was dis-
covered by Winkler in 1886 in a Freiberg silver ore.

The element vanadium, which was discovered by Del Rio
in 1801, was isolated by Roscoe in 1867. He also inves-
tigated its compounds carefully, determining its different
stages of combination with oxygen and chlorine. This
metal, which is widely distributed, is utilized in the pro-
duction of sheet and tool steel and armor plates. Tan-
talum, a related metal, which, along with columbium, or
niobium, was examined exhaustively by Blomstrand and
Marignac, is used in alloys to make small springs and
anvils, and in the metallic form to make special incan-
descent electric light filaments.

The metals of the platinum group— platinum, palladium
(Wollaston, 1803), rhodium (Wollaston, 1804), iridium
(Tennant, 1803), osmium (Tennant, 1803), and ruthe-
nium (Claus, 1844) — have been given careful considera-
tion by chemists. Platinum is used extensively in making
chemical apparatus, especially crucibles and stills; and
osmium and iridium have recently come into use as fila-
ments for incandescent lamps.

258 CHEMISTRY

About fifteen years ago the number of the chemical ele-
ments was enlarged by two gases of great theoretical in-
terest— argon and helium.

As early as 1785, Cavendish had noticed that a residue
of about 0.6 per cent, remained when the nitrogen and oxy-
gen were removed from air, and in 1894 Rayleigh discov-
ered that nitrogen from the atmosphere was 0.5 per cent,
heavier than nitrogen prepared chemically. Rayleigh and
Ramsay then prepared large quantities of this atmospheric
residue and found it to be a gas different from nitrogen.
They called it 'argon' from the Greek 'argos,' lazy.

Helium was discovered by Ramsay in 1895 in the min-
eral cleveite. It had already been found to exist in the
chromosphere of the sun by Janssen in 1868, and his ob-
servations were confirmed by Frankland and Lockyer.
Helium, primarily obtained by heating cleveite with sul-
phuric acid, and since found in small quantity — often to-
gether with argon — in the minerals uraninite, malacone,
etc., as well as in the gases from some mineral water
springs, is, like argon, inert and indifferent. Up to now,
in spite of persistent effort, no compound of either argon
or helium has been prepared. And, further, altho many
diffusion experiments with both gases have been carried
out, with the object of seeing whether they were really
elementary, the densities of both have remained unaltered
— i.e., it has been found impossible to subdivide them by
diffusion into two or more components. From the ratio
of the specific heats at constant volume and constant pres-
sure, it follows that the molecule and atom are identical
in both argon and helium — i.e., that the gases are mona-
tomic; and this applies also to the other more recently
discovered gases of the air — krypton, neon and xenon.

These were separated from liquid air in 1898 by Ramsay
and Travers. The atomic weights of these gases and the
proportions in which they are present in the air are as
follows :

MODERN INORGANIC CHEMISTRY 259

Helium

Atomic Weight.

One Part by Volume in Air.

4

2,450 volumes

Neon

20

808

Argon

39-9

105

Krypton

81.8

746,000 "

Xenon

128

3,846,000 "

Since the interest attached to these gases has been re-
cently augmented by the discovery of Ramsay and Soddy
that radium emanation eventually changes, at least in part,
into helium, and since Ramsay has shown that when the
radium emanation decays in the presence of water neon is
produced, and that argon results when the decay takes
place in the presence of water containing a copper salt in
solution, the radioactive elements may be conveniently
referred to here.

Henri Becquerel found in 1896 that compounds of ura-
nium spontaneously and continuously emit some radiation
which, among other properties, has that of making air a.
conductor of electricity. This effect, the quantity of which
can be determined with great accuracy, was used by Mme.
Sklodowska Curie to measure the amount of radiation
produced by various compounds of uranium and of tho-
rium, which latter had been found by Schmidt to emit the
same kind of radiation.

She subsequently tested a large number of rocks and
minerals, and found that certain minerals which contained
uranium and thorium — e.g., pitchblende (oxide of urani-
um), chalcolite (double phosphate of copper and uranium)

Fig. 25 — Apparatus Employed in Studying Radioactivity.
1., spinthariscope. In this instrument a particle of radium nitrate
is placed near a fluorescent screen of zinc sulphide ; when
this is examined with a high-power magnifier a scintillating
appearance of great brilliancy is observed, giving the appear-
ance of a "turbulent luminous" sea. The small set-screw
regulates the distance between the screen and the radium,
thus allowing of a variation in the effects produced. 2., ra-
dium cell. 3., electroscope with discharging plates. 4., tube
for the removal of radium emanation from solution ; R =
radium salt in solution, i — inlet tube for air stream, and
O = outlet tube for air.

MODERN INORGANIC CHEMISTRY 261

— possess radio-activity much greater than that "theoreti-
cally" due to the amount of uranium present.

Mme. Curie therefore inferred that, "It appeared prob-
able that if pitchblende, chalcolite, etc., possess so great a
degree of activity, these substances contain a small quan-
tity of a strongly radio-active body, differing from uranium
and thorium and the simple bodies actually known. I
thought that if this were indeed the case, I might hope to
extract this substance from the ore by the ordinary meth-
ods of chemical analysis."

The investigation was consequently pursued, and, with
the assistance of her husband, Pierre Curie, and Gustave
Bemont, Mme. Curie commenced the laborious treatment
of the residue remaining after the extraction of the ura-
nium from pitchblende, a large quantity of which had been
placed at her disposal by the Austrian Government, and
finally separated the salts of radium in 1898. While en-
deavoring to isolate radium, Mme. Curie discovered po-
lonium, and other investigators — Debierne, Giesel, Marck-
wald and Hofmann — have given the names of actinium,
emanium, radio-tellurium and radio-lead to similar sub-
stances, the two last being possibly products of the spon-
taneous change in radium. Among those who have worked
with success upon the problem of radio-activity, Elster and
Geitel, Rutherford, Soddy and Ramsay may be mentioned
here.

Radium maintains a temperature one or more degrees
above that of the atmosphere, injures the eyes, and dis-
organizes the flesh when kept long in contact with it. Its
peculiar properties have been explained in various ways.
The most plausible suggestion is that atoms of high atomic
weight slowly disintegrate into ultimate corpuscles or
particles, and that this decomposition is attended with the
devolopment of great energy.

The successive disintegration of the radium atom as
exemplified by the disintegration products is shown in the
following table, which represents, according to Ernest

262

CHEMISTRY

Rutherford, the complete radium series as at present
known :

Element.

Radium

4

Radiation
' emitted.

Period.

i particles 2000 3

I

Range of a

particles in air

at normal

pressure.

3*5 cms.

Emanation .
I

a particles

1 3 8 days
1

4'3 cms.,

-3 JRa. B . . .

•e j r

a particles
3 particles

1

3 minutes

26 minutes

41 8 cms..

# ARa. C,. . ..

(a and /3 particles )
\y rays ' /

19 minutes

706 cms.

8>

i
•a

,Ra. D . . .

4

Ea. E . . .
41

9

40 years
6 days

.—

1

Ra. F . . .

4

Ra. G . . .

4

8 particles

45 days

-

a particles

140 days

3-86 cms.

It appears that uranium is the source of radium, and
Boltwood has recently announced the immediate parent
of radium, "ionium." Radium resembles barium chemi-
cally and, according to Mme. Curie and Thorpe, it has an
atomic weight of 226.5. Several observers have demon-
strated that it possesses a characteristic spectrum, and
consequently, notwithstanding its disintegration and pe-
culiar conduct, radium is regarded as a chemical element,

MODERN INORGANIC CHEMISTRY 263

owing to an affidation among chemists to recognize a body
as a chemical element when, under proper conditions, it
possesses a definite atomic weight and exhibits a spectrum
containing characteristic and novel lines.

In 1823, Mitscherlich discovered the existence of sulphur
in two different crystalline varieties — rhombic and ob-
lique, and a third variety, the plastic form, was also known.
Frankenheim learned that by heating and cooling, these
varieties could at definite temperatures be converted into
one another, and in describing these phenomena the term
isomerism was employed, to which, however, Berzelius
published an objection in 1841. To quote from his 'Janres-
bericht' for that year:

"I feel compelled to call attention to the fact that the
word isomerism, which is applied to different substances
composed of an equal number of atoms of the same ele-
ments, is not compatible with the view as to the cause
of the different properties exhibited by the various modi-
fications of sulphur, carbon, silicon, etc. . . . While
the term still lends itself to the expression of the relation
between ethylformate and methylacetate, it is no longer
suitable in the case of simple substances which assume
different properties, and it might be desirable to substi-
tute for it a better chosen term — e.g., allotropy, or allo-
tropic modifications. In accordance with these views
there can be more than one cause for that which we call
isomerism, namely:

(1) Allotropy, in which case . . . the difference
between the sulphides of iron is due to the fact that they
contain different modifications of sulphur.

(2) Differences in the relative position of the atoms
in the compound, of which the two kinds of ether (ethyl-
formate and methylacetate) are so striking a proof.

(3) A combination of (1) and (2)."

Since then the term allotropy has been in constant use,
and numerous allotropic phenomena have been observed,

264

CHEMISTRY

particularly among the non-metals. The allotropism of
carbon was the first observed example (1773), and its
modifications exhibit marked points of difference; for in-
stance, comparing diamond and graphite :

J:

-a

a,

0

c 0

">

a;

Zh.2

rt__a>

O

c
-a

&w

.H o>

ill

IG

rt

0

a.
O

a) Si

0,
t/l

X

Diamond

Cubic

Colorless, trans-

Non-conductor of

3-52

10

/

parent; high refrac-

heat and electric-

. tive index,

ity, not attacked by

Carbon

,M=2.4I7

oxidizing agents;

\

ignition tempera-

ture 7600 to 8750

Graphite

Hexagonal ?
Oblique ?

Opaque

Good conductor of
heat and electric-
ity; oxidized to
graphitic acid; ig-
nition temperature
5750 and above

2.25

I

When amorphous carbon (coal, peat, lampblack, etc.)
and diamond are heated, they pass into the graphitic va-
riety, and graphite is now produced in large amounts by
heating carbon to a high temperature (4,000° C.) by an
alternating electric current. Henri Moissan (1852-1907),
an eminent French chemist, succeeded in preparing syn-
thetic diamonds by dissolving pure sugar charcoal in
molten pure iron and suddenly cooling the mass by plung-
ing it into water; and three English chemists, Sir F. A.
Abel, W. H. Noble and Sir William Crookes, obtained dia-
monds by exploding some of the high explosives in steel
bombs, the liquid carbon produced crystallizing as it cooled.
However, no diamonds have thus far been produced of
commercial size or amount.

The most peculiar, as well as noteworthy, example of
allotropism is afforded by the conversion of oxygen into
ozone. Ozone was first noticel by Van Marum in 1785

MODERN INORGANIC CHEMISTRY 265

in electrified air. In 1840, C. F. Schonbein called attention
again to this substance, discovered its oxidizing action,
and showed that it was produced in the electrolysis of
water and in the slow combustion of phosphorus and sul-
phur. He gave it the name "ozone," which means a smell.
The investigations of Marignac, De la Rive, Becquerel,
Tait, Fremy, Andrews and Brodie have proved it to be
modified oxygen. Its density was determined by Soret
in i860. The latter, and before him Andrews, proved that
the ozone molecule contains three atoms of oxygen, while
a molecule of the latter is made up of two atoms. Ozone
is now used in the sterilization of water.

Among other allotropic modifications those of selenium
and phosphorus are of interest. Berzelius investigated
the allotropes of selenium, and those of phosphorus were
studied by Berzelius, Schrotter, Hittorf and Schenck.
Schrotter discovered the red variety in 1845, and Hittorf
found that it could be transformed into a metallic modifi-
cation. Several additional allotropes of sulphur have been
discovered in late years, and the fact that many metals
can also exist in allotropic forms has been clearly demon-
strated— e.g., colloidal gold, silver, platinum and mercury.

The list of the compounds of the elements was greatly
extended from the time of Lavoisier, particularly with
the discovery of new acids and the growing knowledge of
the different basicity of the various acids. It is important
to mention some of the discoveries of moment.

In 1818, one of the most interesting of inorganic com-
pounds was discovered by Thenard. He proved that
water was not the sole oxide of hydrogen, but that an-
other— peroxide of hydrogen, but which he termed "oxy-
genated water" — may be prepared. This compound plays
a prominent role in many processes of nature, and is now
prepared in quantities, by treating barium dioxide with
sulphuric c.cid, for disinfecting and bleaching purposes.

The list of the halogen acids was completed prior to

266 CHEMISTRY

1820. Gay-Lussac and Balard studied hydriodic and hy-
drobromic acids ; the former, Davy and Faraday inves-
tigated hydrochloric acid ; while Thenard, Gay-Lussac and
Berzelius contributed greatly to an intimate knowledge
of hydrofluoric acid. In 1869, Gore and Nickles contin-
ued the investigation of anhydrous hydrofluoric acid, and
the latter lost his life through its action. Gore and Fremy
established its composition, but, as before mentioned, the
element fluorine was not isolated until 1886.

The oxygen compounds of chlorine, iodine and bromine
have been given much attention since the commencement
of the nineteenth century. The work of Gay-Lussac on
chloric acid, Balard on hypochlorous acid, Millon on chlo-
rous acid, and Davy and Stadion on chlorine peroxide, was
exceedingly valuable and led to researches which firmly
established the composition of these bodies. The oxygen
compounds of iodine received careful attention in the
hands of Davy and Magnus, and the latter discovered iodic
acid, the principal compound of that halogen.

Following Gay-Lussac's discovery of "hyposulphurous
acid" in 1813 and dithionic acid in 1819, little attention
was given to the compounds of sulphur and oxygen until
the fourth decade, when the thio-acids, which contain more
sulphur and are more closely related to sulphuric acid,
were recognized. More recently the early known oxides
of sulphur — sulphur dioxide and sulphur trioxide — have
received several additions in sulphur sesquioxide, sulphur
tetroxide and sulphur heptoxide. Sulphuric acid, the most
important of all chemicals, is used in enormous quantities
in the industries, and its manufacture has been immensely
developed. , Over two million tons were used in the
United States in 1908.

The very poisonous compounds of hydrogen with phos-
phorus, arsenic and antimony — phosphine, arsine and sti-
bine — were given considerable attention during the first
and second decades of the modern period. Phosphine, or
hydrogen phosphide, was discovered in 1783 by Gen-

MODERN INORGANIC CHEMISTRY 267

gembre, and its composition was studied by Davy. Rose
continued its investigation at a later date. Arsine was
prepared in a pure state by Soubeiran; Gehlen fell a vic-
tim to its toxic action in 181 5.

Phosphorous and phosphoric acids were known to
Lavoisier, but their constitution was not established until
a much later period. It was upon the relations which
Gay-Lussac, Stromeyer and Graham found existing be-
tween the ortho-, pyro and meta-phosphoric acids, that
Liebig founded his theory of polybasic acids, which marked
such an important step forward in chemistry.

The important compound hydroxylamine, which may be
regarded as ammonia in which a hydrogen atom has been
replaced by hydroxyl (OH), was discovered by Lossen
in 1865. It has led to a knowledge of many remarkable
organic compounds. Similarly, the analogous compound,
hydrazine, which was first prepared by Curtius in 1887,
has entered into the preparation of a series of interesting
compounds; for example, the hydrazones and hydrazides.
It is an exceedingly powerful reducing agent.

Of the simple carbon compounds, the greater number
were discovered in the first decade. Carbon disulphide,
which was accidentally discovered by Lampadius in 1796
while heating pyrites with coal, was accurately examined
by Vauquelin in 1812. It is now prepared in an electric
furnace, by conducting sulphur vapor over heated carbon,
and finds extensive use as a solvent. Carbonyl chloride, or
"phosgene gas," was discovered by Davy in 181 1, and
carbon oxysulphide by von Than quite recently. The
compounds of carbon with certain metals — carbides — are
now of great technical importance. In 1808, Davy dis-
covered potassium carbide, the first described in chemical
literature, and in 1862 Wohler prepared calcium carbide,
now one of the most important on account of its use in
the generation of acetylene and in the manufacture of
calcium cyanamide, a new constituent of fertilizers. Cal-

268 CHEMISTRY

cium carbide has, since 1894, been prepared by fusing
limestone and carbon together in an electric furnace.

Before closing this brief resume of some of the advances
made in the knowledge of chemical compounds mention
must be made of the metallic peroxides, hydrides and ni-
trides.

Sodium peroxide, which was discovered by Gay-Lussac,
is now used extensively under the name "oxone" as a
bleaching and oxidizing agent, and calcium peroxide,
discovered by Gay-Lussac and Thenard, is used in den-
tistry. The discovery of the hydrides belongs to the pres-
ent day ; among the most important of these is calcium hy-
dride, "hydrolite," which is used for generating hydrogen.
The metallic nitrides, as magnesium, calcium, boron and
lithium nitrides, have only lately been investigated care-
fully, but may become of great importance.

Numerous important chemical and physical facts were
learned concerning the gaseous bodies, especially during
the second, third and seventh decades, and the experiments
which were conducted with a view of liquefying gases are
of the highest import, more particularly with regard to
the production of liquid air and its application to re-
searches at low temperatures.

The experiments of Davy and Faraday, in which the
gases were generated in curved closed glass tubes and
cooled to about — 200 C. in a freezing mixture, resulted in
the liquefaction of all the common gases, with the excep-
tion of hydrogen, nitrogen, oxygen, methane, carbonic
oxide and nitric oxide. In 1834, Thilorier liquefied carbon
dioxide in considerable quantities and obtained the solid ;
he was the first to operate on a large scale, and subsequent
investigators made use of many of his observations. Be-
tween the years 1844 and 1855, Natterer studied the rela-
tionship of pressure and volume over wide ranges of pres-
sure, and in 1852 he exposed hydrogen to a pressure of
2,790 atmospheres, but was unable to effect its liquefaction..

MODERN INORGANIC CHEMISTRY 269

It was only in 1877 that Raoul Pictet and Lewis Cailletet
succeeded, almost simultaneously, in liquefying the ma-
jority of the so-called permanent gases. Their success
was due to a recognition of the fact that reduction of tem-
perature was necessary as well as pressure, but it was not
possible by the aid of the methods and appliances which
they employed, to obtain the liquids in large amounts and

P| water

■if 1 1 ; ' 1 1 " 1 i Li 1 i>{

WliillJJilLMWL

^^Ss^^^^SS^SSSSSBSS

Fig. 26 — Ammonia Ice-Plant.
Ammonia gas is pumped under great pressure into the condenser
pipes, which are cooled by a shower of cold water. The
liquefied ammonia is admitted through the expansion-valve
v to the coils in the brine tank. The cold produced by the
volatilization and expansion of the ammonia lowers the tem-
perature of the brine to about — 20. The water to be frozen
is placed in prismatic vessels and lowered into the brine.

to determine their physical constants. This was accom-
plished by Wroblewsky, a chemist in Cracow, and he had
Olszewsky first obtained quantities of oxygen and nitrogen
in the liquid state, and described many of their properties.
These two investigators share with Dewar, an English
chemist, the honor of having first devised practical meth-
ods for the production of liquid air in quantity; and in

270

CHEMISTRY

1896 C. Linde in Germany and W. Hampson in England
constructed technically efficient forms of apparatus for
producing liquid air.

Apparatus for Liquefying Air.

Lind's apparatus consists essentially of a pump (P.), a cooler
(J.), a double spiral tube surrounded with non-conducting
material (D.), and a reservoir for the liquid (T.). The
double tube, which is several hundred feet in length, is so
arranged that the air in the inner tube is subjected to a
pressure of 200 atmospheres, while the pressure in the outer
tube is only 20. The pump draws air from the outer and
forces it into the inner tube. The air passes through the
cooler to remove the heat due to compression and is then
allowed to flow through a cock (R.) into the reservoir, where
it is cooled by its sudden release from pressure and its rapid
expansion. In a little while the air reaches the liquefying
temperature and slowly collects in the receiver.

Liquid air has not as yet, however, found any technical
application upon a large scale. Nearly pure oxygen is
obtained from it very cheaply, and the attempt has been

MODERN INORGANIC CHEMISTRY 271

made to apply it in the manufacture of explosives, but, so
far, liquid air has achieved the most important results in
chemical research.

In the first place, it must be mentioned that Dewar, by
its aid, has succeeded in liquefying hydrogen, and in ob-
taining air, oxygen and hydrogen in the solid state ; and
that in doing so he has achieved almost everything that can

-A

28 — Cryogenic Apparatus.

Some apparatus employed in experiments with liquid air. a.,
Dewar bulb, a vessel of double walls separated by a vacuum ;
the walls of the evacuated space are silvered to reduce the
heating effect of transmitted light. Vessels of this type are
used as containers for liquid air. b., another view of same.
c, apparatus for obtaining liquid oxygen in the laboratory.

be done in this direction. However, he is at present at-
tempting to reach the so-called absolute zero.

The results that have been obtained by means of this
agency with respect to the discovery of the "noble gases"
are of greater importance. Since these have been de-
scribed, it only remains to be stated that Onnes, in his
cryogenic laboratory in Leyden, has recently announced
that he has liquefied helium and that it boils at — 268.50 C.

CHAPTER XV

THE ATOMIC WEIGHTS AND THE PERIODIC LAW

In a preceding chapter an attempt was made to trace
the early development of the atomic theory, and later it
was shown how this theory became a necessity for the
development of organic chemistry.

It had fallen into disfavor because of the difficulties en-
countered by Berzelius and others in distinguishing be-
tween atoms and molecules; but much light was thrown
upon this and other matters as the chemistry of the com-
pounds of carbon was better understood ; and the fact that
the dominant doctrine of the new chemistry quietly as-
sumed the truth of Dalton's theory in all its important
particulars was reflected upon the older chemistry, so that
this great theory became the basis for it all.

The old confusion between atoms and equivalents was
not entirely done away with until after Frankland's in-
vestigations of the organo-metallic bodies, yet in 1846
Laurent had clearly distinguished between atom, molecule
and equivalent, and his definitions are still current. He
stated that "the atom of M. Gerhardt represents the
smallest quantity of ta simple body which can exist in a
combination ; my molecule represents the smallest quantity
of a simple body which must be employed to perform a
chemical reaction."

This definition of a molecule was employed until quite
lately in general, but in 1888 Lothar Meyer pointed out
that it was insufficient. Gerhardt defined "equivalent"
as follows:

272

THE ATOMIC WEIGHTS 273

"According to our views, the conception of equivalent
implies that of similarity of function ; it is known that the
same element can play the part of one or other of several
very different elements, and it may happen that to each
of these different functions corresponds a different weight
of the first element."

Seven years previously, in 1842, when he had not ar-
rived at a clear distinction between "equivalent" and
"atomic weight," Gerhardt had doubled the equivalents of
carbonic acid and of water, and in 1843 he followed this
up by doubling the values of the symbol weights used by
French chemists (H = 0.5, O = 8, C = 6, etc.), render-
ing them thereby identical with Berzelius' atomic weights.
The reasons for this change were derived from the study
of chemical reactions. He found that the amounts of
water, carbonic acid, ammonia and sulphurous acid evolved
in the interactions between the quantities of organic com-
pounds represented by the formulae assigned to them on
chemical grounds, were always two (or multiples of two)
equivalent weights of H20, C02 S02, when H = 0.5, O =
S, C = 6, S = 16.

Both Gerhardt and Laurent expressed sound views on
the selection of atomic weights. They recommended the
choice of such of these as were in agreement with the re-
quirements of the law of isomorphism, the law of Avo-
gadro and the law of heat capacity, and which above
everything are chemically adequate. However, appar-
ently the chemical public was not yet ready for the change.
In his great text-book on organic chemistry, the publica-
tion of which was begun in 1853, Gerhardt retained
Gmelin's equivalent-weight notation. He is reported to
have said in private conversation that unless he had done
so no one would have bought the work ; in the introduction
to the book the matter is put more formally :

"I have even sacrificed my notation, retaining the old
formulae the better to show by example how irrational they

274 CHEMISTRY

are, and leaving to time the consummation of a reform
which chemists have not yet adopted."

Confusion continued to reign for some time longer.
The terms equivalent, atomic weight, molecular weight
were used and abused in every conceivable sense; some-
times even employed as synonymous.

About the middle of the century two units or standard
elements were in use for the determination of combining
weights. Dalton had suggested hydrogen as unity, and
this standard was adopted by Gmelin and many others.
Wollaston and Berzelius took oxygen as the standard,
Wollaston giving it the value 10, and Berzelius using it
as ioo ; Thomson had given it the value I. The standard
of Berzelius was the accepted one for a long time, but
about 1842 a return was made to the standard of Dalton.
It was in this year that Dumas, whose atomic weight de-
terminations are classical, redetermined the ratio oxygen :
hydrogen from the composition of water, and had ascer-
tained it to be 15.96:2, and had expressed his belief that
the true value was probably 16:2. His number, which
in the same year was confirmed by the results of Erd-
mann and Marchand, was for a long time considered as
extremely exact.

However, the work of Jean Servais Stas (1813-1891)
soon after furnished numbers for the combining weights
of a large number of elements which had all been de-
termined by direct reference to 16 of oxygen, and the ac-
curacy of which was far superior to that of the ratio oxy-
gen : hydrogen. Indirectly he had obtained for hydrogen
in terms of oxygen = 16.00, the value 2.02. Though not
attaching special importance to this result, Stas asserted
that the composition of water was not known with suffi-
cient accuracy for hydrogen to be a suitable standard, and
he expressed himself in favor of 16 of oxygen. Since,
however, 16.00 was then generally accepted as the exact
combining weight of oxygen in terms of the hydrogen
standard, Stas' recommendation involved no recalculation;

THE ATOMIC WEIGHTS

275

that is, no change in practice, only a change in theory de-
sirable from the point of view of future possibilities. The
adoption of the oxygen standard advocated would have
meant that if a redetermination of the composition of
water should lead to a change in the value of the ratio
oxygen : hydrogen, the effect of this would only be an al-
teration of the value used for the combining weight of
hydrogen, and not the necessity of a recalculation and a
consequent change of all the combining weight values de-
termined directly in terms of oxygen. Stas' suggestion,
which it must be admitted was not pressed strongly, did not
receive much support.

All the work of Stas was monumental in the care taken
to secure accuracy. The determinations of atomic weights
by him of importance were those of silver, potassium, so-
dium, lithium, lead, chlorine, bromine, iodine, sulphur, ni-
trogen and oxygen.

.A-G

Fig. 29 — Apparatus of Stas.
Apparatus used by Stas for the complete analysis of silver iodate.

Much of this work was carried out to prove or disprove
the correctness of Prout's hypothesis, and Stas concluded
as follows : "I have arrived at the absolute conviction, the
complete certainty, as far as it is possible for a human
being to attain to certainty in such a matter, that the law
of Prout, together with M. Dumas' modifications, is noth-
ing but an illusion, a mere speculation definitely contra-
dicted by experience."

In i860, J. C. Marignac (1817-1894), who had deter-
mined the atomic weights of a number of elements, pub-

276 CHEMISTRY

lished a paper in support of what he termed Prout's "law."
He observed that "... the differences between the
results obtained by M. Stas and those required by the law
of Prout are certainly very small, but they are consid-
erably greater . . . than the greatest differences be-
tween the results obtained in each set of experiments."

The results referred to, as well as those of Marignac
himself, are appended:

Stas (i860). Marignac. Prout.

Silver 107.943 107.921 108

Chlorine 3546 35456 35-5

Potassium 39.13 39-II5 39

Sodium ..." 23-°5 23

Ammonium 18.06 .... 18

Nitrogen 14.041 14.02 14

Sulphur 16.037 16

Lead (synthesis of sulphate). 103453 .... 103.5

Lead (synthesis of nitrate) . . 103460 .... 103.5

Marignac reasoned from Stas' results that Prout's hy-
pothesis was substantiated rather than disproved. He
employed the two arguments of the Proutians, that Stas'
numbers were very close approximations to whole numbers
and hence could be considered as such, and that those
approximations were too numerous to be accidental. This
fatal error of rounding off fractions into whole numbers
was the very thing which misled Prout at the beginning
and with him there was far more excuse for it. Marignac
further said that should future determinations of other
elements give similar approximations he would feel as-
sured of the existence of some fundamental cause which
brought about the multiple relation of the atomic weights
and subordinate causes which modified it. He thought that
Prout's Law deserved to rank with that of Gay-Lussac or
of Mariotte.

In another place Marignac referred to Prout's Law as

THE ATOMIC WEIGHTS 277

one of those not absolute but only approximate laws, like
many other natural laws.

From 1888 onward, there appeared in quick succession
redeterminations of the ratio oxygen : hydrogen, all demon-
strating that Dumas' experimental number 15.96 was too
high; but in the meantime Lothar Meyer and Seubert,
strong champions of the hydrogen standard, had made this
value the basis of very popular atomic weight tables. The
new data did not provide a sufficiently reliable number to
make recalculations of all the other values desirable, and
the obvious way out of the difficulty, the use of the tables
of Ostwald in which the 16.000 oxygen standard was used,
was not generally accepted. As a result two tables of
atomic weights, one based on O = 16 and the other on
0=15.96, were in use until quite recently.

From the year 1896 onward, K. Seubert exerted himself
to effect a general agreement with regard to the basis upon
which all atomic weights should be founded, and in 1900
an International Atomic Weights Commission was ap-
pointed for the purpose of settling the question. The re-
sult of their deliberations has been to make oxygen (O =
16) the "official" basis instead of hydrogen (H == 1) ; the
hydrogen unit is, however, often preferred still, both in
practical work and in teaching. The main ground for the
Commission's taking oxygen as the foundation is the fact
— originally brought forward by Berzelius — that by far the
greater number of the atomic weights have been derived
from compounds of oxygen and not from compounds of
hydrogen.

Among the chemists other than those mentioned whose
efforts were directed to improving the methods of deter-
mining atomic weights may be mentioned Turner, Penny,
Marchand, Pelouze, De Ville, and Scheerer. Recently
Morley and Richards have done noteworthy work.

The most recent table of International Atomic Weights
is as follows:

278

Aluminium. . ..Al
Antimony . . . Sb

Argon A

Arsenic As

Barium Ba

Bismuth Bi

Boron B

Bromine Br

Cadmium . . ..Cd

Caesium Cs

Calcium Ca

Carbon C

Cerium Ce

Chlorine CI

Chromium ...Cr

Cobalt Co

Columbium . . Cb

Copper Cu

Dysprosium ..Dy

Erbium Er

Europium . . . Eu

Fluorine .F

Gadolinium . . Gd

Gallium Ga

Germanium ..Ge

Glucinum Gl

Gold Au

Helium He

Hydrogen . . . H

Indium In

Iodine I

Iridium Ir

Iron Fe

Krypton Kr

Lanthanum . . La
Lead Pb

CHEMISTRY

0 = i6

0 = i6

27.1

Lithium ....

.Li

7.00

120.2

Lutecium . .

.Lu

174.0

39-9

Magnesium .

• Mg

24.32

75-o

Manganese .

.Mn

54.93

137-37

Mercury . . .

•Hg

200.0

208.0

Molybdenum

.Mo

96.0

11.0

Neodymium

.Nd

144-3

79.92

Neon

.Ne

20.0

112.40

Nickel

.Ni

58.68

132.81

Nitrogen . . .

.N

14.01

40.09

Osmium . . .

..Os

190.9

12.00

Oxygen

.O

16.00

140.25

Palladium ..

.Pd

106.7

3546

Phosphorus .

..P

31.0

52.1

Platinum . . .

.Pt

195.0

58.97

Potassium . .

.K

39.10

93-5

Praseodym'm

.Pr

140.6

63.57

Radium ....

..Ra

226.4

162.5

Rhodium . . .

.Rh

102.9

167.4

Rubidium . .

..Rb

85-45

152.0

Ruthenium .

..Ru

101.7

19.0

Samarium .

.Sa

150.4

157-3

Scandium ..

.Sc

44.1

69.9

Selenium . .

.Se

79-2

72.5

Silicon ....

.Si

28.3

9.1

Silver

•Ag

107.88

197.2

Sodium

..Na

23.00

4.0

Strontium .

.Sr

87.62

1.008

Sulphur . . .

.S

32.07

1 14.8

Tantalum . .

..Ta

181.0

126.92

Tellurium . .

..Te

127-5

I93-I

Terbium . . .

..Tb

i59-£

55-85

Thallium . .

.Tl

204.0

81.8

Thorium . . .

..Th

232.42

139.0

Thulium . . .

..Tm

168.5

207.10

Tin

..Sn

1 19.0

THE ATOMIC WEIGHTS 279

0 = i6
Titanium . . . .Ti 48.1

Tungsten W 184.0

Uranium U 238.5

Vanadium ...V 51.2

Xenon Xe 128.0

0 = i6
Ytterbium . . . Yb 172.0
(Neoytterbium)

Yttrium Y 89.0

Zinc Zn 65.7

Zirconium ...Zr 90.6

Reverting to the middle of the past century, one finds
that much of the credit of removing the difficulties attend-
ing the determination of the atomic weights, and of trans-
ferring them to a more substantial foundation than had
hitherto been in use, is due to Stanislao Cannizzaro

(1826 ). It was he who, by his criticism in a paper

entitled 'Sunto di un Corso de Filosofia Chimica' ('Out-
lines of a Course of Chemical Philosophy') (1858), eluci-
dated the methods employed for arriving at the relative
atomic weights of the elements. He recognized, as espe-
cially reliable, the deduction of these values from the
vapor densities of chemical compounds — a method now in
universal use.

Cannizzaro's paper began as follows (Freund) :

"It seems to me that the progress of chemistry within
the last year has served to confirm the hypothesis of Avo-
gadro, Ampere and Dumas concerning the similar constitu-
tion of gaseous substances; namely, the assumption that
equal volumes of gases, whether elementary or compound,
contain an equal number of molecules. But they by no
means contain an equal number of atoms, the reason for
this being that the molecules of different substances, or
even of the same substance in the different states which
it can assume . . . may consist of a different number
of atoms of the same or of different kinds. In order to
bring my pupils to this same conviction I have let them
follow the same path that had led me to it ; namely, that of
the historical examination of chemical theories.

"I begin by showing how from a consideration of the
physical properties of gases, together with Gay-Lussac's

280 CHEMISTRY

law concerning the relation between the volume of a com-
pound and that of its constituents, there has arisen, as it
were, of itself that hypothesis which was first enunciated
by Avogadro and shortly afterward by Ampere. While
expounding in detail the line of argument followed by
these two physicists I proceed to prove that it is not in
contradiction to a single known fact, provided only that we
do as they did: (i) Distinguish between the molecules
and the atoms; (2) avoid confounding the criteria for
comparing the weights and numbers of molecules with
those employed for ascertaining the weights of atoms; (3)
abandon the erroneous view that while the molecules of a
compound may consist of any number of atoms, those of
the different elements must consist of one atom only, or
at any rate of an identical number of atoms."

He then discussed molecular weight determinations and
showed that the hypothesis of Avogadro was a guide in
such work. His argument in favor of making the weight
of half the hydrogen molecule the standard met with favor
and acceptance. Turning from the molecule to the atom,
Cannizzaro showed that the law of Dulong and Petit, and
Avogadro's hypothesis were a guide in the determination
of the atomic weights. To quote further from his paper:

"We next proceed to the investigation of the composi-
tion of the molecules. Whenever the substance cannot be
decomposed, it must be assumed that the whole weight of
its molecules is composed of one kind of matter only; but
if the substance is a compound we analyze it and thereby
determine the invariable ratio by weight of its constitu-
ents, and we then proceed to divide the molecular weight
into parts proportional to those of the relative weights of
the constituents and thus obtain the quantities of the ele-
ments contained in a molecular weight of a compound, all
of them referred to the same unit in terms of which all
molecular weights are expressed. According to this
method I compile the table of molecular composition which
follows :

THE ATOMIC WEIGHTS

281

Name of the substance

Hydrogen

Oxygen

Electrified oxygen

Sulphur under i,ooo°

Sulphur above i,ooo°

Phosphorus

Chlorine

Bromine

Iodini

Nitrogen

Arsenic

Mercury

Hydrochloric acid

Hydrobromic acid

Hydriodic acid

Water

Ammonia

Arsenine

Phosphine

Mercurous chloride

Mercuric chloride

Arsenic chloride

Phosphorous chloride

Ferric chloride

Nitrous oxide

Nitric oxide

Carbonic oxide

Carbonic acid

Ethylene

Propylene

Acetic acid

Acetic anhydride

Alcohol

Ether

filg
fflfl

2.

32

128

192

64

124

71

160

254

28

300

200

36.5

81

128

18

17

78

35

235-5

271

181.5

138.5

325

44

30

28

44

28

42

60

102

46

74

Weights of the constituents of one Tolume or ol

one molecule, all referred to the weight of

a half hydrogen molecule = 1

2 Hydrogen

32 Oxygen

128 Oxygen

192 Sulphur

64 Sulphur

124 Phosphorus

71 Chlorine

160 Bromine

254 Iodine

28 Nitrogen

300 Arsenic

200 Mercury

35.5 Chlorine

80 Bromine

127 Iodine

16 Oxygen

14 Nitrogen

75 Arsenic

32 Phosphorus

35.5 Chlorine

71 Chlorine
106.5 Chlorine
106.5 Chlorine

213 Chlorine

16 Oxygen

16 Oxygen

16 Oxygen

32 Oxygen

4 Hydrogen

6 Hydrogen

4 Hydrogen 32

6 Hydrogen 48

6 Hydrogen 16

10 Hydrogen 16

1 Hydrogen
1 Hydrogen

1 Hydrogen

2 Hydrogen

3 Hydrogen
3 Hydrogen
3 Hydrogen

200 Mercury

200 Mercury
75 Arsenic
32 Phosphorus

112 Iron
28 Nitrogen
14 Nitrogen
12 Carbon
12 Carbon
24 Carbon
36 Carbon
Oxygen 24 Carbon
Oxygen 48 Carbon
Oxygen 24 Carbon
Oxygen 48 Carbon

282

CHEMISTRY

"From this it follows that all the different quantities of
hydrogen contained in the molecules of the different sub-
stances are whole multiples of the quantity contained in
the hydrochloric acid molecule."

He defined the atomic weight as the weight of one atom
of the element referred to the weight of the hydrogen atom
taken = i.oo (or oxygen = 16.00), and stated that it is
determined by finding the least amount of the element
present in the molecular weight of any of its compounds,
which if these are volatile is the least amount present in
2 volumes of any of these compounds in the gaseous state.

It is unnecessary that the molecular weight of the ele-
ment be known, only the molecular weights of as many
volatile compounds as possible, together with the composi-
tion of these compounds expressed as parts of the molecu-
lar weights.

Chemists were thus taught to rely on Avogadro's hy-
pothesis, all inferences drawn from which, Cannizzaro
showed, "are in complete agreement with all the physical
and chemical laws so far discovered." He gave as an
application of Dulong and Petit's law the following:

"The specific heat of copper in the free state . . .
confirms the atomistic conception of its chlorides based
on analogies with the corresponding chlorides of mercury.
Their composition leads us to the inference that they have
the formulae CuCl and Q1CI2, and that the atomic weight
of copper is 63, a fact made apparent by the following
relations :

Ratio between the
components ex-
pressed by num-
bers whose sum
is = 100

Ratio between the
components ex-
pressed by the
atomic weights

Cuprous chloride
Cupric chloride

Chlorine Copper
36.04 : 63.96
52.98 : 47.02

35.5: 63 = CI :Cu
71 : 63 = Cl2: Cu

THE ATOMIC WEIGHTS 283

But the number 63 for the atomic weight, when multi-
plied by the specific heat of copper, gives a product nearly-
equal to that of the atomic weight of mercury or of iodine
multiplied by their respective heats. We get :

63 X 0.09515 =6

At. wt. of copper Spec, heat of copper."

By the use of this law and Avogadro's hypothesis an
approximation to a correct table of atomic weights was ob-
tained, and the road for the inception of the great natural
law underlying them was opened up.

Before the atomic theory was formulated, numerical
relations were proposed by Richter, the founder of Stoi-
chiometry, between the equivalents obtained by him for
the various bases and acids. This mathematical work
served but little purpose beyond bringing the whole sub-
ject of his equivalents into some disrepute. Only a few
years passed after the publication of the first tables of
atomic weights before their inter-relation became a sub-
ject of speculation and research. In 181 5 we have Prout
pointing out the strange fact of their close approximation
to whole numbers and boldly rounding them off into such.
If they were integral multiples of hydrogen, he reasoned,
then this might be the primal matter and all elements made
up of it. The "Multiplen-fieber" quickly took possession
of the chemical world, even of conservative, level-headed
workers such as Berzelius. Enthusiastic support was given
it by the English chemists especially and, when Berzelius
afterward became its great antagonist, Thomson and
others busied themselves in its defense. The newly or-
ganized British Association devoted its fresh energies to
an examination into the condition of the various sciences
and, among other inquiries, set on foot one as to the
grounds for believing in what was then called and has
been often so called since, Prout's Law. The result of this
inquiry was adverse to the "law" and it would have been
dropped, in all probability, had it not been taken up by

284 CHEMISTRY

Marignac, Dumas and the French chemists, with certain
modifications rendered necessary by the more perfect
knowledge of the atomic weights.

Meanwhile, a different style of numerical regularity had
been brought to the notice of chemists. In 1817, Dobereiner
first noticed a strange grouping of analogous elements
into threes, or triads as they soon came to be called. He
said, according to Venable:

"Noteworthy relations are revealed when one examines
the stoichiometrical values of the chemical elements and
compounds arranged in series.

"1. Those most often found in plants have the smallest
values and are the most abundant. The highest values
are less widely distributed.

"2. Those corresponding in many physical and chemical
properties, as iron, cobalt and nickel, have almost the
same stoichiometrical value.

"3. Compounds which have like equivalent numbers are
almost alike in chemical constitution."

For a long period following this paper there was no
further attention given to this question, but in 1829 Dobe-
reiner published another paper which appears to have been
a result of the atomic weight determinations of Berzelius
in 1825. He indicated that the atomic weight of bromine
approximates the arithmetical mean of the atomic weights
of chlorine and iodine, namely :

35470 -f 126.470

= 80.970, considering H = 1.

2

Of this mean he stated that tho somewhat greater than
78.383, the number actually found by Berzelius, it so
closely approximates to it as to justify the hope that re-
peated accurate determinations of all the atomic weights
involved will lead to a disappearance of any difference.
He found similar relations for the alkaline earths, the

THE ATOMIC WEIGHTS 285

alkalies, and for the group comprising sulphur, selenium,
and tellurium, as shown by the equations :

356.019 (== Ca) + 956.880 (= Ba)

= 656.449 (= Sr),

2
but experiment gave for strontium, regarding O = 100,
647.285.

195-310 (= Na) + 589.916 (= K)

= 3926l3 (=Li),

2
but experiment gave for lithium, regarding O = 100,
390.897.

32.239 (= S) + 129.243 (=Te)

■ = 80.741 (=Se),

2

but experiment gave for selenium, considering H = 1,
79.263.

For more than twenty years little was added to the work
of Dobereiner and no new ideas were advanced. This
was in part due to imperfections in the determinations of
the atomic weights and ignorance as to whether they
should be written as had been done by Berzelius or many
of them doubled as was done by Gerhardt.

Further, the whole question of atomic weights was in
much doubt and numerical speculations concerning them
would have had little significance during this period.

The first to continue the consideration of such "triads"
was Dumas, who in 185 1 called attention to the triads of
Dobereiner, and suggested that in a series of bodies, pro-
viding the extremes are known, the intermediate bodies
might be discovered, and stated that a suspicion arose as to
the possibility of the intermediate body being composed of
the extremes of the series and thus processes of transmuta-
tion might be hoped for.

The next year P. Kremers pointed out the existence of
certain regularly ascending series among the elements, and

286 CHEMISTRY

in 1858 he followed up the old idea of triads, arranging the
elements in the form of "conjugated triads," thus:
Li = 7, Na = 23, K = 39.

Mg = 24, Zn = 40, Cd = 1 12.

Ca = 40, Sr = 87.5, Ba = i37.

In these triads we have the following proportions:
Li : Na : K as 7 : 23 : 39 as Li : Mg : Ca.

Such close agreement was not found in every case, how-
ever, and in 1863 Kremers gave up the doctrine of triads.
In 1853, J. H. Gladstone announced that he found the
numerical relations between the elements to be of three
varieties, namely:

1. The atomic weights of analogous elements are the
same.

2. The atomic weights of analogous elements are in mul-
tiple proportions.

3. The atomic weights of analogous elements may differ
by certain regular increments.

He considered the doctrine of triads as partly a natural
law.

The following year J. P. Cooke published a study of
these numerical relations. He stated that the triads broke
up natural groups of elements — a fatal blow to the doctrine
— and classified the elements into six series, in each of
which the number whose multiples form the differences is
different and may be said to characterize the series. In
the first it is nine, in the second eight, in the third six, in
the fourth five, in the fifth four and in the last three. The
elements were further arranged in series according to the
strength of their electro-negative properties, or in other
words, as their affinities for oxygen, chlorine, sulphur, etc.,
increased, while those for hydrogen decrease as we de-
scend.

Cooke laid stress on the fact that his grouping demon-
strated that the elements may be classified in a few series
similar to the homologous series of organic chemistry. In
1858, John Mercer carried out this comparison with the

THE ATOMIC WEIGHTS 287

organic radicals more fully, basing his work partly on that
of Max von Pettenkofer, who, while engaged on the sub-
ject of the regularities in the atomic weights, made the fol-
lowing comparison:

1. The equivalents of the inorganic elements, which form
natural groups, show among themselves such constant dif-
ferences as the equivalents of organic compound radicals
which belong to natural groups.

2. The simple inorganic elements can therefore be re-
garded from the standpoint of the compound organic radi-
cals.

Pettenkofer also criticized the doctrine of triads.

Lennsen and Odling were about the last chemists to at-
tempt to develop the doctrine of the triads. The former
gave twenty triads, grouping the elements according to
their chemical and physical characteristics, but this classi-
fication was unsatisfactory and he suggested a division in
diads, the third member forming a binding member; for
example, the triads K, Na and Li became diad K. Na, and
binding member Li.

The consideration of the numerical regularities of the
atomic weights from the point of view of the homologous
organic series, of which the ideas of Pettenkofer form a
good illustration, was also taken up by Dumas, who later
published his view of double parallelism. He made this
comparison :

N = i4 P = 3i As = 75 Sb = i22
F=i9 01 = 35.5 Br — 80 1 = 127
On adding 108 to the number for nitrogen we obtain that
for Sb, and on adding it to F we get I, and so the addition
of 61 gives us respectively As and Br. These facts teach
the propriety, he says, of arranging the metals in series
that shall show a double parallelism, for such a classifica-
tion brings to view the various analogies existing between
these elements.

1 None of these considerations materially advanced the
subject of triads from the state in which it had been left

288 CHEMISTRY

by Dobereiner. But, to quote from Freund's 'Study of
Chemical Composition/ "When stress had once been laid
on the approximate constancy of the differences in the
atomic weights of elements forming a group, the ever-
dominant desire for simplicity in numerical relations as-
serted itself. This led to unjustifiable attempts to alter the
experimental values in order to make them agree with
preconceived ideas. We know how variable and arbitrary
were the criteria (prior to i860) used in the determination
of equivalent and atomic weights in general; but in the
special cases of groups of elements there was more uni-
formity, hence the numbers obtained were comparable, and
since the above considerations concerning classification
applied only to groups of elements, it was possible to bring
out within this compass a relation between atomic weight
and properties. The extension to the case of elements in
general soon followed. This was done in a set of short
papers published from 1863 onward by Newlands, the fore-
runner of Lothar Meyer and Mendeleeff."

The work of Newlands followed immediately upon that
of de Chancourtois, who was the first to devise a sym-
metrical arrangement of the elements in his theory of the
"Telluric Screw." His first paper (1863) considered some
numerical relations between the atomic weights. To quote
from Venable's 'Periodic Law' : "These relations were in
part along the line of the old triads. Thus zinc was pointed
out as the mean between magnesium and cadmium, copper
between cobalt and zinc. In the group of the alkalies, one
of lithium and one of potassium made two of sodium ; one
of lithium and two of potassium made one of rubidium, etc.
Similar relations were observed for other groups. He also
endeavored to show a certain kind of symmetry when the
lowest member of a group was subtracted from the next
higher member and when the lowest member of a triad
was deducted from the highest."

In a paper published in 1864, Newlands furnished a table
containing the elements arranged in the order of their

THE ATOMIC WEIGHTS

289

atomic weights. In a side column the differences between
these weights were given, each being deducted from the one
next higher in the scale. The next year Newlands an-
nounced his "law of octaves," which he deduced from his
arrangement of the elements. He said in part that, "If the
elements are arranged in the order of their equivalents,
with a few slight transpositions, as in the accompanying
table, it will be observed that elements belonging to the
same group usually appear on the same horizontal line.

No.

No.

No.

No.

No.

No.

No.

No.

H 1

F 8

CI 15

Co

Ni 22

Br 29

Pd 36

I 42

Pt Ir 50

Li 2

Na 9

K 16

Cu

23

Rb 30

ca 38

Cs 44

Tl 53

G 3

Mg 10

Ca 17

Zn

25

Sr 31

BaV45

Pb 54
Th 56

Bo 4

Al 11

Cr 19
Ti 18

Y

3

Ce La 33

U 40

Ta 46

C 5

Si 12

In

Zr 32

Sn 39

W 37
Nb 48

Hg 52

N 6

P 13

Mn 20

As

27

Di Mo 34

Sb 41

Bi 55

0 7

S 14

Fe 21

Se

28

Ro Ru 35

Te 43

Au 49

Os 51

"It will also be seen that the numbers of analogous ele-
ments generally differ either by 7 or by some multiple of 7 ;
in other words, members of the same group stand to each
other in the same relation as the extremities of one or
more octaves in music."

The same year he gave as an explanation of the exist-
ence of triads the fact that "in conformity with the
Law of Octaves, elements belonging to the same group
generally have numbers differing by seven or by some mul-
tiple of seven. That is to say, if we begin with the lowest
member of a group, calling it 1, the succeeding members
will have the numbers 8, 15, 22, 29, etc., respectively. But
8 is the mean between 1 and 15; 15 is the mean between 8
and 22, etc., and therefore as an arithmetical result of the
Law of Octaves the number of an element is often the
exact mean of those of two others belonging to the same
group and consequently its equivalent also approximates
to the mean of their equivalents."

Two years before the presentation of Newland's paper
before the London Chemical Society, containing the "Law

290 CHEMISTRY

of Octaves," Lothar Meyer (1830-1895), published
the first edition of his 'Die Modernen Theorien der Che-
mie,' in which he gave a table of the elements arranged
horizontally according to their atomic weights, so that
analogous elements stood under one another and the
change of valence, along with that of atomic weight, could
be easily observed.

This was Meyer's first attempt, and his table exhibited
less evidence of periodicity than that of Newlands, but it
caused Meyer to give the question of the relationship of
the atomic weights more serious consideration and his
mind continued working on the atomic relationship. His
first table had been in the following form:

4 val.

Meyer's First
3 val. 2 val.

Table.

1 val.

1864.
1 val.
Li 7.03

2 val.
(Be 9.3)

Diff

16.02

(14.7)

C 12.0

N 14.4 O 16.00

F 19.0

Na 23.5

Mg 24.0

Diff. 16.5

16.96 16.07

16.46

16.08

16.0

Si 28.5

P 31.0 S 32.0

ci 3546

K 39-13

Ca 40.0

Diff .A|* 4445

44.0 46.7

44-51

46.3

47.0

As 75.0 Se 78.8

Br 79.97

Rb854

Sr 87.0

Diff. *H 44.55

45-6 49-5

46.8

47.6

49.0

Sn 117.6 Sb 120.6 Te 128.3

I 126.8

Cs 133.0

Diff. ^44.7

^437 ....

35-5

Pb 207.0

Bi 208.0 ....

....

(Tl 204.0?)

Ba 137.1

4 val.

4 val. 4 val.

2 val.

1 val.

{ Mn 55.1
I Fe 56.0

Ni 58.7 Co 58.7

Zu 65.0

Cu 63.5

( 49-2
Diff \

(48.3

45-6 47-3

46.9

44.4

Ru 104.3

Rh 104.3 Pd 106.0

Cd 1 1 1.9

Ag 107.94

Diff. -4--S- 46.0

-4^-46.4 ^-46.5

H* 44-5

*¥* 44-4

Pt 197.1

Ir 197. 1 Os 199.0

Hg 200.2

Au 196.7

On leaving Eberswald in 1868, he left with his successor
the following elaborate table, according to Seubert:

00

o *v

II -9 II

'I "I II III

t>»

Zn= 65.0
46.9

Cd= 1 1 1.9
83.3 = 2.44.5
Hg = 200.2

2

ON M °°

VO

<7\ ■* *>»

VO M..M

II* II I II

-*

VO

0 rA
00 6 r?

11 O II VO II

to

06
m

II

2

m o\

M 0

pq

° O vo 2.

tj-^-j vo rt ^ i-h e, rt

Tf

II
<

0 ^

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292 CHEMISTRY

The following year Dmitri Mendeleeff (1834-1907), a
Russian chemist, published his first paper embracing the
important principles of the Periodic Law. He states that
he was led to the consideration of the question in this way:

"When I undertook to write the text-book, entitled The
Foundations of Chemistry/ I had to decide for some one
system, lest, in the classification of the elements, I should
have allowed myself to be guided by accidental, and, so
to speak, instinctive reasons rather than by an accurate
and definite principle."

Mendeleeff then showed that the principles hitherto
used in classification had not been of a quantitative na-
ture, and he laid stress on the superiority of a system
which is based on numerical relations and therefore leaves
no scope for arbitrary interpretation. Consideration of
the numerical data available in the case of the elements
led him to the rejection of the optical, electrical and
magnetic properties, because these vary with the condi-
tions ; and of the vapor density, because this is not known
for many elements, and is different for the allotropic modi-
fications.

He next emphasized the unalterability of the atomic
weight, stating that, "For this reason I have tried to take
as basis for my system of classification the value of the
atomic weight. . . . Beginning with the one of small-
est atomic weight, I arranged the elements according to
the magnitude of their atomic weights, when it became
evident that there exists a kind of periodicity in the prop-
erties of the simple substances. . . .

"Hence in this system of classification the atomic weight
of an element determines the place to be assigned to it,
. . . and all the comparative investigations that I have
made lead me to the conclusion that the magnitude of its
atomic weight determines the character of an element in
the same measure, as the molecular weight determines the
properties and many of the reactions of a compound.

THE ATOMIC WEIGHTS 293

"I designate by the name of 'Periodic Law' the mutual
relations between the properties of the elements and their
atomic weights, relations which are applicable to all the
elements, and which are of the nature of a periodic func-
tion."

Mendeleeff's first table was very imperfect, and the
scheme of arrangement he followed was not entirely ac-
cording to the size of the atomic weights. It was accord-
ing to this arrangement:

mendeleeff's table. 1869.

Ti 50 Zr 90 ? 180

V 51 Nb 94 Ta 182

Cr 52 Mo 96 W 186

Mn 55 Rh 104.4 Pt 197.4

Fe 56 Ru 104.4 Ir 198

Ni,Co 59 Pd 106.6 Os 199

Hi Cu 63.4 Ag 108 Hg 200

Be 9.4 Mg 24 Zn 65.2 Cd 112

B 11 Al 27.4 ? 68 Ur 116 Au 197

C 12 Si 28 ? 70 Sn 118

N 14 P 31 As 75 Sb 122 Bi 210

O 16 S 32 Se 79.4 Te 128?

F 19 CI 35.5 Br 80 I 127

Na 23 K 39 Rb 85.4 Cs 133 Tl 204

Ca 40 Sr 87.6 Ba 137 Pb 207

? 45 Ce 92

?Er 56 La 94

?Y 60 Di 95

?In 75.6 Th 118

He made use of other arrangements also, but the tables
which he gave in 1871 contain the plan resorted to in its
final and perfected form. One of these tables gave the
horizontal and the other the vertical method of arrange-
ment; these follow:

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THE ATOMIC WEIGHTS

295

MENDELEEFF S TABLE

11.

Gr. Ser.i

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4-

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8

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12.

I.

Li 7

K39

Rb85

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Ni 58.6

Ru 103
Rh 104
Pdio6

Os 194
Iri95
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Na23

Cu 63.5

Agio8

Au 197

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Mg24

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Ga 69

In 113

Tl 204

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Si 28

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Sn 118

Pb 204

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As 75

Sb 120

Bi 208

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S 32

Se79

Te 125?

VII.

CI 35-5

Br 80

I 127

These tables contain the Periodic Law as it is known
to us. They have not been very materially altered, tho
they have been corrected in minor points. The work since
has been mainly one of elaboration, and, as Venable ob-
serves, "The credit for the expansion and filling out of
the Periodic Law, its extension to the other properties of
of the elements and the bringing of the various com-
pounds of these elements into consideration also, has been
almost entirely due to the skill and knowledge of Men-
deleeff."

In 1870, Meyer offered a full table representing the na-
ture of the elements as a function of their atomic weights
which was so similar to Mendeleeff's that many accused
him of plagiarism, but his claims to the authorship of the
Periodic Law are based on his 1864 and 1868 tables, and
his 1870 system appears to have been an expansion of his
earlier tables. It is generally considered that Mendeleeff"
and Meyer worked out the Periodic Law independently.

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THE ATOMIC WEIGHTS 297

The Periodic Law soon attracted merited attention, but
for several years its importance was not generally recog-
nized, and it was not until the discovery of some new
chemical elements, thereby fulfilling certain predictions
of MendeleefT, that it became accepted.

MendeleefT had obtained the atomic weights of elements
not fully investigated by taking the mean of the weights
of what he termed the "atom-analogues." For instance,
the atom-analogues of selenium were arsenic and bromine
on the one hand, sulphur and tellurium on the other; its

f 75 + 80 + 32 +, 125 1
atomic weight should be < >• = 78.

He had also applied the Periodic Law to the determina-
tion of the properties of unknown elements. This was
accomplished by estimating the physical and chemical char-
acter from those of the atom-analogues, since he had es-
tablished that all properties were functions of atomic
weight. He described the properties of three undiscovered
elements, and the following values he predicted will show
why the Periodic Law was finally gladly accepted :

Eka-aluminium Gallium

Suggested by MendeleefT Discovered in 1875 by Lecoq de
Atomic weight, 68. Boisbaudran

Specific weight, 60. Atomic weight, 699.

Atomic volume, 11-5. Specific weight, 596.

Atomic volume, 11-7.

Eka-boron Scandium

Suggested by MendeleefT Discovered in 1879 by Nilson

Atomic weight, 44. Atomic weight, 4397.

Oxide, Eb2Os; Sp. Gr., 35. Oxide, SC2O3; Sp. Gr., 3864.

Sulphate, Eb2(S04)3. Sulphate, Sc2(SO*)3.

Double sulphate not iso- Double sulphate, 3K2S04.Sc2

morphous with alum. (S04)3.

Crystallizes in fine columns.

298 CHEMISTRY

The other, eka-silicon (Es = 72), was discovered by
Winkler in 1886. It is now called geranium (Ge = 72).

At the present time all chemists recognize the depen-
dence of the properties of the elements upon the atomic
weights, and the periodic law has become the central idea
in the classification and study of the elements and their
compounds. This law is the greatest discovery in chem-
istry since the announcement of Dalton's atomic theory,
and has been much more rapidly accepted. It promises
to lead up to results of the utmost importance.

The close and mystifying relationship existing between
the chemical elements which was revealed by the Periodic
Law, naturally has attracted the minds of scientists to
thoughts similar to the conception of one primordial mat-
ter as expressed by the Ionian philosophers, and later by
Bacon, Descartes and Boyle. To quote Freund:

"Within the last two decades experimental evidence,
physical and chemical, has been accumulating in support of
these speculations, and the last few years' contributions
have been such as to make the complexity of the atoms as
much of an established fact as that of the molecular and
atomic structure of the masses of matter that we per-
ceive. Moreover, the empirical results which, taken in
their entirety, can almost be said to have proved this point,
have also supplied evidence which justifies the course hith-
erto followed by chemists in assigning to the atoms a very
special place in the scale of the complexity of different
kinds of matter. It seems that the diversity of matter be-
gins only with the atom: that while the component parts
of a molecule A are not the same as those of another kind
of molecule B, or C, or D, etc., the constituents of an
atom M are identical with those of any other different
atom P, or Q, or R, etc.; that all atoms are compounded
of the same one kind of primordial matter."

The most important papers which have been published on
the unity of matter and on the composite character of the

THE ATOMIC WEIGHTS 299

elements are those of Sir William Crookes, Anton Grun-
wald, Gustav Wendt, Henry Wilde, Eduard Meusel, W.
Preyer, C. T. Blanshard and Sir Norman Lockyer.

Of these speculations and views, the most important is
the hypothesis of Crookes. According to him, the chemi-
cal elements have resulted by gradual condensation from
a primary material which he terms "protyle." He ar-
rived at this view in 1886 from observations on the phos-
phorescence spectra of the yttrium earths. When he ad-
vanced this hypothesis, "provisionally," Crookes had to
assume the complexity of the elementary atoms, but since
then experimental and theoretical knowledge on this
point has become more definite, as is shown by J. J. Thom-
son's investigations on the structure of the atom. Thom-
son started from the hypothesis that the atom is an aggre-
gation of a number of simpler systems, and that these
are formed by "corpuscles" associated with equal charges
of positive electricity. He then traced the analogies be-
tween atomic structures and atomic properties, and fur-
nished an explanation for the empirical relations be-
tween atomic weight and atomic properties embodied in
the Periodic Law. As Freund remarks, "In a section of
the community usually referred to as the 'general public'
there seems to be an impression that the recognition of
the divisibility of the atom has dealt a deathblow to that
atomic theory which was founded by Dalton just a hun-
dred years ago. No misconception could be more com-
plete. While nothing has had to be given up, nothing to
be modified, there has been deepening of the foundations,
extension of scope, correlation with other sciences. Ex-
cept that some of the anticipations expressed have since
been realized, the situation to-day is what it was when
Kekule" stated that while from a philosophical standpoint
he did not believe in the actual existence of atoms, yet as
a chemist he regarded the assumption of atoms, "not only
as advisable, but as absolutely necessary in chemistry."

CHAPTER XVI

THE DEVELOPMENT OF APPLIED CHEMISTRY

Analytical chemistry — that division of chemistry
which treats of the methods of ascertaining the chemical
composition of substances and mixtures both as to kind
(qualitative analysis) and quantity (quantitative analysis)
— has been an indispensable aid to all branches of chemis-
try, pure and applied, during their modern development,
and has itself undergone considerable elaboration and per-
fection. In particular, analytical methods, both qualitative
and quantitative, have been and are being continuously
improved.

The services of Boyle, Hoffmann, Marggraf, Scheele
and Bergman in qualitative analysis have been mentioned,
and it will be remembered that Bergman was the first to
publish a system of qualitative analysis in the wet way.
He laid a firm foundation for the methodical employment
of reagents, and the methods of qualitative analysis now in
use have been developed from his analytical course of
procedure. Wilhelm August Lampadius and Johann Gott-
ling contributed materially to the systematic arrangement
of the analytical methods in use during the first decade.
The former published in 1801 his "Handbuch der Che-
mischen Analyse der Mineralkorper," and the latter his
"Praktische Anleitung zur Priifenden und Zerlegenden
Chemie" in 1802. Other works followed these, and analyti-
cal methods became known and improved.

Qualitative analysis in the dry way has been perfected
300

APPLIED CHEMISTRY 301

by the use of the blowpipe, an instrument which was origi-
nally employed for soldering metals, and which was fipst
employed for testing minerals by Cronstedt and Enge-
stroem. Bergman and Gahn studied thoroly the deport-
ment of various substances and reagents under the flame
of the blowpipe, and their treatise on this important
branch of chemical analysis was published in 1779. Ber-
zelius, Hausmann and Wollaston later became interested
in this field, and Berzelius, who was notably instrumental
in introducing the blowpipe into chemistry, published a
treatise on the application of this instrument in 1820.
More recently the art of dry assay ("docimacy") was con-
siderably advanced by the important flame-reactions of
Bunsen. His treatise, "Flammen-Reactionen," was pub-
lished in 1880.

After the preparatory investigations of Bergman, Klap-
roth, Vauquelin and' Proust, it was Berzelius who worked
out new methods of quantitative analysis, thereby promot-
ing the systematic development of this branch. He had
shown great ingenuity and inspired his pupils, more espe-
cially Heinrich Rose and Friedrich Wohler, with like
powers. Rose and Wohler extended the observations of
Berzelius, and made analytical methods generally known
by the publication of their treatises. The "Hand-
buch der Analytischen Chemie" of the former first ap-
peared in 1829, and passed through six German editions
and three French editions; while the "Practische Uebun-
gen in der Chemischen Analyse" of Wohler, which was
published in 1853, was translated into Russian, French
and English.

The chief exponent and great master of analytical
chemistry, however, was' C. Remigius Fresenius (1818-
1897), who for over half a century devoted his life and
labors to its extension. He collated and examined all
methods formerly in use, and devised many new ones; but
his greatest services were the establishment of the "Zeit-
schrift fur Analytische Chemie" in 1862, and the publica-

302

CHEMISTRY

tion of his "Anleitung zur Qualitativen Chemischen Ana-
lyse" in 1841 and his "Anleitung zur Quantitativen Che-
mischen Analyse" in 1846. These works have been pub-
lished in numerous editions and translations since.

Fig. 30 — Apparatus Designed by Fresenius.
j., hot-air oven; 2., gas-drying jar; 3., absorption flask ^ 4., chlo-
rine distillation apparatus; 5., distillation head.

Other chemists who have aided in the discovery of new
tests, improved methods of separation and determination,
and in the designing of suitable chemical apparatus for
analytical operations are Liebig, Stromeyer, Bunsen,
Fremy, Turner, Scheerer, Rammelsberg, Gibbs, Blom-

APPLIED CHEMISTRY 303

strand, Marignac and Winkler. Classen's services in
electro-analysis have been referred to.

Volumetric analysis — that process in which the reagents
are employed in solutions of known strength — has been
greatly developed during the last seventy years, and volu-
metric methods are much used in technical analysis, owing
to the fact that no weighing is necessary after the standard
solutions are once made up, thus saving considerable time.

The quantitative analysis of gases was greatly perfected
by Bunsen, whose researches in this direction began in
1838. Bunsen published methods of estimating various
gases by absorption and combustion, which have required
only slight modifications since, but the qualitative analysis
of gases has only lately been developed in a scientific man-
ner. The work of Winkler in this connection has been
important, and he and Hempel have improved the appa-
ratus for gasometry and gas analysis and have generalized
methods.

The quantitative analysis of organic compounds has
gradually developed from the observation that carbonic
acid and water are products of their combustion. Lavoi-
sier indicated the right path here, and his process was im-
proved upon by Gay-Lussac and Thenard, Berzelius, Lie-
big, and more recently by Dennstedt, Collie and Hempel.
The exact determination of nitrogen only became possible
after 1830, when Dumas had devised his method. Other
methods of determining nitrogen have been worked out by
Will and Varrentrapp, and by Kjeldahl, whose method is
extensively used in agricultural-chemical analysis for esti-
mating protein. Many methods for determining the halo-
gens, sulphur, phosphorus, and other elements which occur
less frequently in organic bodies, have been worked out,
and these have found extended application in forensic
chemistry, hygiene and agricultural chemistry.

The beginnings of phytochemistry, the chemistry of
plant-life, can be traced back to investigations made at the
close of the eighteenth centry.

304 CHEMISTRY

Priestley, Senebier, de Saussure, and others were famil-
iar with the fact that green plants under the influence of
sunlight will remove carbonic acid gas from the atmos-
phere and decompose it. They were also aware of the fact
that ammonia salts are of value in stimulating the growth
of plants, Nicolas Leblanc having pointed this out at the
end of the eighteenth century.

Altho the problems of plant-life, the mode and manner
of plant-nourishment and growth, had engaged the labors
of many trained observers for many years, yet even during
the first three decades of this century the belief was almost
universal that plants, like animals, derived their nourish-
ment directly from organic matter.

This assumption found its chief advocates in Germany
and France in Albrecht Thaer and Mathieu de Dombasle
respectively. In their opinion inorganic salts, the impor-
tance of which could not be absolutely denied, acted merely
as stimulants and not as if they were essential to the
growth of the plant. Indeed, Thaer held that the creation
of earths in plants through their vital forces was possible.
In this assumption he followed the opinion of Schrader,
who so early as the year 1800 imagined that he had proved
by actual experiments the generation of the ash-constitu-
ents of plants by the vital forces.

J. G. Wallerius, a Stockholm chemist, had sought to lay
a much more rational foundation for agricultural chemis-
try in 1761 in his "Akerbrukets Chemiska Grunder," when
he made a comparison between the plant constituents and
the constituents of the soil on which they grew.

It was Justus von Liebig who demonstrated the falsity
of the views of Thaer and Dombasle, and who entirely
disproved the humus-doctrine, as the theory held at that
time was called. It was in 1840, after exhaustive investi-
gations on the weathering of rocks, on the formation of
soils, and on the effects of rain and the gases which rain
holds in solution, that Liebig published his classic work on
the application of chemistry to agriculture and physiology.

APPLIED CHEMISTRY 305.

In this Liebig completely undermined the foundations
of the humus theory and enunciated the following founda-
tion principles of modern agricultural chemistry:

1. Inorganic substances form the nutritive material for
all plants.

2. Plants live upon carbonic acid, ammonia (nitric acid),
water, phosphoric acid, sulphuric acid, silicic acid, lime,
magnesia, potash and iron ; many need common salt.

3. Manure, the dung of animals, acts not through the
organic elements directly upon plant-life, but indirectly
through the products of the decay and fermentative proc-
esses; thus carbon becomes carbonic acid and nitrogen,
becomes ammonia or nitric acid. The organic manures,,
which consist of parts of remains of plants and animals,
can be substituted by the inorganic constituents into which
they would be resolved in the soil.

Practical field trials, carried out by governments and
large land-owners, proved the correctness of Liebig's de-
ductions from his laboratory experiments, and the many
investigators in this line since have come either directly
or indirectly from Liebig's school. Liebig's conclusion
that one must restore to the soil that which the removal of
the crop had withdrawn, if one would prevent its exhaus-
tion, is the basis of successful agricultural practice to-day.

A French chemist, J. B. Boussingault, worked inde-
pendently along similar lines to Liebig, and the services
which he rendered in carrying out researches on the nutri-
tion of plants by new methods were of great importance.

Mention may be made here about nitrification in soils,
and the assimilation of free nitrogen by plants, the most
important discoveries in agricultural chemistry of recent
years. In 1849, Georges Ville, then director of the Agri-
cultural Experiment Station at Vincennes, proved by
actual experiment that certain plants assimilate free at-
mospheric nitrogen, but his conclusions were strongly dis-
puted, being directly opposed to those of Boussingault and
Liebig, and also to subsequent investigations by Lawes,

3o6 CHEMISTRY

Gilbert and Pugh in 1857. An important experiment bear-
ing on the point and extending over many years was begun
in 1855 by Herr Schultz, of Lupitz, in Altmark, Germany.
He grew lupines on very poor soil with the addition of
non-nitrogenous manures only and found that, notwith-
standing this, the soil became richer in nitrogen year by
year. The next step toward the solution of the question
was the discovery in 1877 of the now well-known process
of "nitrification" in soils by Schloesing and Miintz, this
nitrification being the work of definite microbes, some of
which have been isolated, while more recent work has
proved that the direct assimilation of atmospheric nitrogen
by leguminous plants is brought about by the agency of
certain micro-organisms (tubercle bacteria) originally
present in the soil. Cultures of these specific bacteria are
now prepared on a manufacturing scale, under the name of
"nitragins," for application to soils naturally deficient in
them.

It only remains to mention as a factor in the present and
future growth of agricultural chemistry the experiment
stations and laboratories established now by the govern-
ments of every civilized country. In the United States, for
example, there are at present sixty-one agricultural ex-
periment stations, all in charge of efficient specialists, and
many intricate problems of national importance have been
solved.

The large chemical industries and, in fact, all branches
of chemical technology have been immensely developed
during the nineteenth and twentieth centuries, and the
achievements of chemistry in the arts and industries have
been stupendous and varied.

During the Modern Chemical Period pure chemistry and
applied chemistry have been constantly interactive, and
the latter has profited immensely by the extension of the
former, while pure chemistry (theoretical, inorganic, or-
ganic and practical chemistry) has in turn been greatly

APPLIED CHEMISTRY 307

benefited by the opportunities offered by the industries.
The advancement of technical chemistry has been espe-
cially aided, however, by the development of analytical
chemistry, which has allowed of a keen insight into the
composition of the various industrial products, thereby
leading to the introduction of many technological innova-
tions. Then, too, industrial research has been and is being
constantly fostered by chemical manufacturers, and this
has led to the accruement of important novelties and im-
provements.

The literature of technical chemistry is very extensive,
but the standard treatises of Rudolf von Wagner ("Hand-
buch der Chemischen Technologie"), Karl Karmarsch
("Geschichte der Technologie seit der Mitte des achtzehn-
ten Jahrhunderts"), T. E. Thorpe ("A Dictionary of Ap-
plied Chemistry") and Ernst von Meyer ("A History of
Chemistry," translated by McGowan) contain accounts of
the development of the important industries.

The manufactures of sulphuric acid and soda, which may
be looked upon as the basis of all the other chemical in-
dustries and which are naturally followed by those of
hydrochloric acid, bleaching powder, chlorate of potash,
and other salts of potassium, nitric acid, etc., only attained
to their full vigor after the various processes involved had
been explained by chemical investigation and after the
most favorable conditions for those processes had been
worked out.

Important practical improvements were made in the
manufacture of sulphuric acid so early as the beginning of
the nineteenth century — e.g., the amount of steam required
was regulated and the process was made continuous (the
latter by Holker). The first attempt to explain this re-
markable chemical process of the formation of sulphuric
acid from sulphurous acid, air, water and nitrous gas was
made by Clement and Desormes, who recognized the
important part played by the nitric oxide. How essential
for the manufacture the careful observations on the chemi-

3o8

CHEMISTRY

car behavior of nitrous acid to sulphurous and sulphuric
have been is sufficiently evidenced by the introduction of
the Gay-Lussac and Glover towers to which they gave
rise and which have made the process into one complete
whole.

In 1831, Peregrine Phillips discovered the "contact
process" by bringing about the combination of sulphur
dioxide and oxygen in presence of platinum, but it was
only forty to fifty years later that Clemens Winkler con-
verted this experiment into a technical manufacture. The
contact process, in many modifications, has developed and

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improved so rapidly that many think it will eventually
supplant the old chamber process altogether.

Common salt forms the foundation of the soda industry,
whose history commences with the beginning of the mod-
ern chemical period. Nicolas Leblanc was the first to suc-
ceed in converting salt into soda, with sodic sulphate as
an intermediate product, Malherbe and de la Metherie
having some time previously attempted to utilize the latter
substance in the same way, but without material success.
It was in 1791 that Leblanc commenced the actual manu-
facture of soda, and in the year 1823 Muspratt began the
erection of his alkali works at Liverpool; his name de-
serves a foremost place in connection with the develop-
ment of the soda industry. The formation of soda from

APPLIED CHEMISTRY 309

the sulphate, by fusing the latter with coal and limestone,
was ultimately so far explained by exact chemical experi-
ments as to allow of a tenable theory of this fusion process
being advanced.

Scientific researches have also given rise to numerous
important improvements in the soda manufacture — e.g.,
to the beautiful process of Hargreaves and Robinson, by
which sulphate of soda is prepared directly without the
previous production of sulphuric acid, to the introduction
of revolving soda furnaces, and to many processes for util-
izing and rendering harmless the unpleasant alkali waste.
But the greatest advance of all in this direction is the
comparatively recent and exceedingly simple process of
Chance, by which nearly all the sulphur in alkali waste
can be recovered at a very cheap rate.

Purely chemical observations have also led to what was,
until quite recently, the most important of all the innova-
tions in the soda industry, viz., the conversion of common
salt into carbonate of soda without the intermediate forma-
tion of sulphate at all, by the ammonia-soda process. The
manufacture of "ammonia soda" and of artificial manures
has grown so enormously of late years that the demand
for salts of ammonia has increased proportionately, but
this requirement has in its turn been met by the introduc-
tion of improved apparatus for the working up of gas
liquor and by the successful attempts to extract the nitro-
gen of fuel in the form of ammonia, at the same time that
the heat from the fuel or the residual coke is itself being
utilized.

Berthollet's experiments upon the bleaching action of
chlorine and the chlorides of the alkalies led to the manu-
facture of the bleach liquor known under the name of "Eau
de Javelle." Chloride of lime was first produced by Messrs.
Tennant & Co. in Glasgow in the year 1779. Weldon's
process for the recovery of the manganese dioxide, re-
quired in the preparation of chlorine, from the otherwise
worthless chlorine waste has been in practical working

310 CHEMISTRY

since 1867. Deacon's method 01 producing chlorine di-
rectly from hydrochloric acid has never been very widely
used.

The manufacture of bromine and iodine is based upon
the original work of Gay-Lussac and Balard. Laboratory
experiments have also led to the production of iodine from
mother liquors which were formerly looked upon as value-
less— e.g., those from Chili saltpeter and from phosphorite
after its treatment with acid. To A. Frank is due the
merit of having made bromine available for technical pur-
poses by preparing it from the mother liquor of the Stass-
furt waste salts.

Nitric acid plays an important part in chemical indus-
tries, especially since the development of the manufac-
ture of explosives on a large scale. Potassium nitrate,
which has been known and valued for so long, is still an
indispensable ingredient of black gunpowder. Since the
introduction of the nitrate of soda from the Chili deposits,
nitric acid has been prepared from it (instead of from the
more expensive nitrate of potash) by the old process of
distillation with sulphuric acid, the latest advance here
being the distillation of the nitric acid in a vacuum.

The explosives, whose preparation now forms a great
industry, have all been made available for practical use by
chemical investigations. The epoch-making discovery of
gun-cotton by Schonbein and Bottger (independently) in
1846 must be recalled here. Nitro-glycerine had been
known as a chemical preparation, discovered by Sobrero,
for fifteen years before it began to find extended applica-
tion in 1862, as the result of Nobel's researches.

The match industry owes its enormous development to
the increased knowledge of chemical preparations and
processes. There is a marked contrast between the
"chemical tinder" of 1807 — i.e., matches containing a mix-
ture of chlorate of potash and sulphur, which were ignited
by dipping them into sulphuric acid — and the present fric-
tion matches ! Those prepared with ordinary yellow phos-

APPLIED CHEMISTRY 311

phorus were most probably first introduced in 1833 by
Irinyi of Pesth, and subsequently by Romer of Vienna
and Moldenhauer of Darmstadt; they have since under-
gone many improvements, the most important of these
being subsequent to the discovery of amorphous (non-
poisonous) phosphorus, which has been used since the
year 1848. Phosphorus has been manufactured on the
large scale for about fifty years. Scheele's process for its
preparation was improved upon by Nicolas so far back as
1778, and has been materially modified in recent years.

Closely connected also with the soda industry are the
manufactures of ultramarine and of glass. The former
substance was discovered in 1828 by Chr. Gmelin and at
about the same time by Guimet; a little later it was also
discovered, independently, by Kottig of Meissen, who was
the first to prepare it on a technical scale.

The production of glass reached a high state of develop-
ment in olden times through pure empiricism, but has
greatly benefited by chemical research. The manufacture
of glass with sulphate of soda, and the improvements in
flint and crystal glasses belong to the last century, while
progress has also been made in silvering (by Liebig), and
in glass painting through the discovery of new mineral
colors.

Water glass, which was known to Agricola and Glauber,
was made available for technical purposes by Fuchs in
1818, and has since then been used for a great number of
different purposes — e.g., for impregnating wood and pre-
paring cements.

The attempts to utilize raw vegetable products, particu-
larly wood and straw, for the production of paper were
first carried out in the year 1846. In caustic soda a reagent
was found by means of which cellulose could be prepared
from these materials, while of late years a solution of cal-
cium sulphite in sulphurous acid has shown itself especially
well adapted for this purpose. The above process for the
production of sulphite cellulose resulted from the chemical

312

CHEMISTRY

investigations of Tilghman. Cross and Bevan's discovery
that cellulose can be dissolved by carbon disulphide and
soda, and thus be converted into a soluble cellulose
xanthate has enormously extended the uses to which the
plastic material can be put. Objects of all kinds, from

Fig. 31 — Glass Tank-Furnace.
Plan and elevation of a tank-furnace for the manufacture of
glass. The batch is introduced at (A.), and a gas flame issues
from (C, C.) and plays over the surface of the charge. The
batch (B.) soon fuses and the liquid mass flows toward the
opposite end of the tank. At (F.) are elliptical "floaters" of
fire-clay, one end of which rests in recesses in the wall, while
the free ends meet in the middle of the furnace. The cur-
rent of melted glass, flowing toward (D.), constantly presses
these floaters together and prevents their separation. The
liquid mass thus passes under the "floaters" and collects in
the compartment (D.), from which it is withdrawn through
the openings (E., E.).

"artificial silk" to billiard balls, can now be made of pure
cellulose.

The beet-sugar industry has developed into an enormous
manufacture from experiments carried out by chemists on
a small scale. Marggrafs discovery, in 1747, that sugar

APPLIED CHEMISTRY 313

was present in the juice of beet, was not at that time
capable of being applied commercially. Achard, a pupil
of Marggraf, and others again took up at the end of the
eighteenth century the problem of obtaining sugar from
beet on the large scale, and they devised a process which
was carried out in factories during the years of the Na-
poleonic wars. However, this process was unable to exist,
being a very imperfect one and giving but a small yield of
sugar, and it is from the year 1825 that the real rise of the
beet-sugar industry dates, various factors entering into its
growth, not the least of which was the practical application
of chemical knowledge. Scheibler's strontia process for
obtaining the crystallizable sugar from molasses is based
upon a knowledge of the various saccharates of strontia.
The nitration of the refined juice through bone charcoal
was first recommended by Figuier in 181 1 and then by
Derosne in 1812, and has since become an essential part of
the process. The use of vacuum pans for evaporating the
syrup was introduced by Howard in 1813, since which time
many improvements have been made in them. Osmosis,
which was first applied on the large scale by Dubrunfaut
in 1863 for extracting the crystallizable sugar from mo-
lasses, was developed by researches in physical chemistry.

The development of the fermentation industries has been
immensely extended by chemical investigation, while at the
same time the nature of the processes themselves has been
explained. The latest work of E. Buchner and his pupils
has resulted in showing that fermentation is brought about
by an enzyme ("zymase") produced from the yeast.

Among the more important observations in this branch
during recent years are those of Effront upon the favorable
effect of a minute quantity of hydrofluoric acid on the
fermentation process, and of others upon the advantages
gained by ventilation and by the use of pure yeast cultures.

A knowledge of the normal composition of wine and beer
has led to rational suggestions for the improvement of
those liquors. It would be impossible to attempt even a

314 CHEMISTRY

bare enumeration of the more important innovations in
this branch, many of which are due to Pasteur — e.g., the
Pasteurization of beer.

In no other section of technical chemistry have there
been so many discoveries made by systematic investigation
as in that of artificial dyes.

The first aniline dye which was produced upon a techni-
cal scale was the mauve prepared by W. H. Perkin in 1856,
by acting upon aniline with bichromate of potash and sul-
phuric acid, and it is to him that the introduction of the
color industry is due. A. W. Hofmann observed in 1858
the formation of aniline red (magenta), which was shortly
afterward manufactured by another method by Verguin of
Lyons and introduced into commerce under the name of
fuchsine. This was followed by the discovery of aniline
blue, aniline violet and aniline green, all of which were
first prepared by Hofmann himself, while he proved that
all of them were derivatives of fuchsine. The discovery of
methyl violet by Lauth in 1861 and that of aniline black by
Lightfoot in 1863 were of great practical importance. In
addition to this new and important methods for the produc-
tion of rosaniline dyes have been discovered and developed
— e.g., oxalic acid, formic aldehyde and carbonyl chloride
are now used for the synthesis of diphenylamine blue, the
new magenta, methyl violet, and allied compounds.

The valuable dye alizarine was formerly prepared en-
tirely from the madder root, but is now obtained from
coal-tar, this revolution having been brought about by
Graebe and Liebermann's successful synthesis (in 1869)
of alizarine from anthracene, a constituent of coal-tar.
Following alizarine, other derivatives of anthracene were
prepared from the year 1880 onward.

An immense industry — that of so-called chemical prepa-
rations— has gradually been developed on scientific lines
from apparently insignificant beginnings which had their
origin in the work of the apothecary; such "preparations"
belong partly to inorganic and partly to organic chemistry.

APPLIED CHEMISTRY 315

As instances of this one may take the great increase in the
production of silver salts, bromine and iodine for photo-
graphic and other purposes, and the manufacture of num-
berless other metallic salts — e.g., thiosulphates, hydrosul-
phites, borates and silicates, not to speak of newly intro-
duced compounds like the peroxides of hydrogen and so-
dium, sodium persulphate and other per-salts and com-
pounds of lithium, rubidium, vanadium, etc. The already
imposing list of inorganic preparations is being continually
added to.

The manufacture of organic preparations is still more
extensive. The various alcohols themselves, their ethers
and esters, chloroform, chloral, iodoform, aldehyde, etc.,
are now all essential to chemical manufactures and to
medicine. The processes by which these compounds are
manufactured are the result of scientific researches, old
and new.

From what has been said it is seen that coal-tar
is the raw material from which many organic
preparations are obtained, the technical importance of
which it is difficult to estimate. Formerly a troublesome
waste material, it is now of at least equal value with the
other products from the distillation of coal. The manu-
facture of ammonia and salts of ammonia from gas liquor
is now a thoroly rational one, thanks to the careful chemi-
cal examination of the latter, and it forms a large and im-
portant branch of industry.

The manufacture of coal gas was at first developed quite
empirically, and it was only in the second half of the nine-
teenth century that improvements were introduced which
were based upon the scientific investigation of the relations
existing between the composition of the gas and the mode
in which the distillation of the coal was conducted, and
this also applies to improved methods of purifying the
crude gas. The present distillation process was introduced
about the year 1880, after it was seen that by raising the
temperature of decomposition the yield of gas from pit

3i6

CHEMISTRY

coal was nearly doubled. In order to achieve the necessary-
white heat, gas retorts are now made from the most refrac-
tory fireclay (instead of iron), and they are heated by
regenerator gas.

About fifteen years ago acetylene began to come into
prominence as an important illuminant ; indeed, enthusiasts
on the subject prophesied that the brilliant light which it
gave would prove to be "the light of the future." Pro-

Fig.
Plan of the Otto-Hopfmann by-product oven.

32 — By-product Coking Oven.

In this type the
retorts "are narrow chambers' (O.) about 40 feet long 5 feet
high and 22 inches wide, having doors at each end, and
heated by vertical flues (T.. T.) in the walls. Coal is
charged through (F.. F.), while the gases and tar pass off
through (A., A.) to the hydraulic main (V., V.).

duced from calcium carbide, a product of electro-chemistry,
it looked for a time as if acetylene were destined to be-
come a formidable competitor of the electric light.

The first impulse toward the use of furnace gas as a
heating agent was given by the experiments of Faber de
Faur and of Bunsen, experiments made with the object
of utilizing the gases issuing from the mouth of iron blast
furnaces, which are rich in carbon monoxide. These, as
well as the gases from coking ovens, were for long allowed

APPLIED CHEMISTRY

3*7

to escape, and still are to some extent, but for the most
part they now constitute important sources of heat. Lowe
introduced "water gas" into technical use in 1875, prepar-
ing it by passing steam over red-hot coal; it is now much
used for heating and illuminating purposes and will un-
doubtedly become even more employed in time.

The above resume of the development of industrial

Fig. 33 — Manufacture of Water Gas.
The Lowe process for making illuminating water gas.

chemistry during the Modern Period will indicate how it
has been elevated by a continuous infusion of scientific
spirit, and manufacturing, once a matter of empirical judg-
ment and individual skill, is more and more becoming a
system of scientific processes. Quantitative measurements
are replacing guesswork, and thus waste is diminished
and economy of production insured. In the United States
several decades ago few industrial establishments furnished
regular employment to chemists, but now American manu-

318 CHEMISTRY

facturers are becoming more and more appreciative of
scientific research, and the results so far obtained have
resulted in far-reaching improvements. In the produc-
tion of a metal from its ores, or of indigo from coal-tar,
it is chemistry that points the way, and the more com-
plex the problem the greater the dependence. In devising
new processes and in the discovery of new and useful
products, chemistry is again the pathfinder. The commu-
nity is apt to overlook the extent and diversity of the
services rendered by the chemist, because of the quiet and-
unobtrusive way in which the work is carried out.

The measure of a country's appreciation of the value of
chemistry in its material development and the extent to
which it utilizes this science in its industries, generally
measure quite accurately the industrial progress and pros-
perity of that country. In no other country in the world
has the value of chemistry to industry been so thoroly
understood and appreciated as in Germany, and in no other
country of similar size and natural endowment have such
remarkable advances in industrial development been re-
corded, and this, too, with steadily increasing economy in
the utilization of the natural resources.

Ex-President Roosevelt has well said, "The life of the
nation depends absolutely on the material resources which
have already made the nation great," and M. T. Bogert re-
cently has eloquently indicated how the chemist can and
will be of service in that great problem, the conservation of
natural resources. This work is not entirely that of the
engineer, and, with the awakening of the producer and
manufacturer to the value of science in industry, the out-
come of the conservation movement can only be a success-
ful one through the assistance of the chemist.

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