LAVOISIER AND LA RÉVOLUTION CHIMIQUE
We have seen how chemistry made a new departure during the political
upheaval which occurred in this country about the middle of the
seventeenth century. It acquired a new impetus and took a fresh course
during the political cataclysm which overwhelmed France and alarmed
Europe towards the close of the eighteenth century. The instigator
and leader of this second revolution in chemistry was Lavoisier, one
of the most distinguished men of his age, and himself a victim of the
political fury of his own people.
=Antoine-Laurent Lavoisier= was born in Paris in 1743. At the Jardin
du Roi he came under the influence of Rouelle, one of the best
teachers of his time, who eventually shaped his career as a chemist.
In 1765 he sent to the Academy his first paper on gypsum, which is
noteworthy as giving for the first time the true explanation of the
“setting” of plaster of Paris, and the reason why overburnt gypsum
will not rehydrate. Three years later he became a member of the
_Ferme-général_—a company of financiers to whom the State conceded, for
a fixed annual sum, the right of collecting the indirect taxes of the
country. It was this connection that brought Lavoisier to the scaffold
during the revolution of 1794. Like Stahl, Lavoisier discovered no new
substance; but, also like Stahl, he created a new epoch by destroying
the philosophical system which Stahl had established.
It is commonly stated that the exception is a proof of the rule. The
history of science can show many instances whereby the rule has been
demolished by the exception. Little facts have killed big theories,
even as a pebble has slain a giant. During the reign of phlogiston
a few of such facts were not unknown—at least to some of the better
informed of Stahl’s followers.
Some of the alchemists had discovered that a metal gained, not lost,
weight by calcination. This was known as far back as the sixteenth
century. It had been pointed out by Cardan and by Libavius. Sulzbach
showed that such was the case with mercury. Boyle proved it in the case
of tin, and Rey in that of lead. Moreover, as knowledge increased it
became certain that Stahl’s original conception of the principle of
combustion as a ponderable substance—he imagined, with Becher, that it
was of the nature of an earth—was not tenable. The later phlogistians
were disposed to regard it as probably identical with hydrogen. But
even hydrogen has weight, and facts seemed to require that phlogiston,
if it existed at all, should be devoid of weight.
Towards the latter half of the eighteenth century clearer views
began to be held concerning the relations of atmospheric air to the
phenomena of combustion and of calcination; many half-forgotten facts
relating to these phenomena were recalled, and the inconsistencies
and insufficiency of phlogiston as a dogma became gradually manifest.
Three cardinal facts conspired to bring about its overthrow—the
isolation of oxygen by Priestley; the recognition by him of the nature
of atmospheric air, and of the fact that one of its constituents
is oxygen; and, lastly, the discovery by Cavendish that water is a
compound, and that its constituents are oxygen and hydrogen. The
significance of these facts was first clearly grasped by Lavoisier, and
to him is due the credit of their true interpretation. By reasoning
and experiment he proved conclusively that all ordinary phenomena of
burning are so many instances of the combination of the oxygen of the
air with the combustible substance; that calcination is a process of
combination of the oxygen in the air with the metal, which thereby
increases in weight by the amount of oxygen combined. Water—no longer a
simple substance—is formed by the union, weight for weight, of oxygen
and hydrogen. Lavoisier’s reasoning was so sound and his experimental
evidence so complete that his views gradually gained acceptance in
France. The phlogiston myth was thus exploded. Inspired by Lavoisier,
a small band of French chemists—Berthollet, Fourcroy, Guyton de
Morveau—thereupon set to work to remodel the system of chemistry
and to recast its nomenclature so as to eliminate all reference
to phlogiston. The very names “oxygen,” “hydrogen,” “nitrogen,”
corresponding respectively to the “dephlogisticated air,” “phlogiston,”
and “phlogisticated air” of Priestley, were coined by the new French
school. For a time _le principe oxygine_ was regarded by this school
in much the same relation as phlogiston was regarded by Stahl and his
followers. The one fetich was exchanged for the other. The combustible
principle—phlogiston—was renounced for the acidifying principle—oxygen.
The new chemistry for a time centred itself round oxygen, just as
the old chemistry had centred itself round phlogiston. The views of
the French school met with no immediate acceptance in Germany, the
home of phlogistonism, or in Sweden or England, possibly owing, to
some extent, to national prejudices. The spirit of revolution, even
although it might be an intellectual revolution, had not extended to
these countries. Priestley, Cavendish, and Scheele could not be induced
to accept the new doctrine. It was, however, accepted by Black, and
its principles taught by him in Edinburgh; and before the end of the
century it had practically supplanted phlogistonism in this country.
Some of those who, like Kirwan, had energetically opposed the new
theory ended by enthusiastically embracing it. Its introduction into
Germany was mainly due to the influence of Klaproth.
We further owe to Lavoisier the recognition of the principle which lies
at the basis of chemical science—the principle of the conservation of
matter. Lavoisier was not the first to introduce the use of the balance
into chemistry: quantitative chemistry did not actually originate with
him. Boyle, Black, and Cavendish, as a matter of fact, preceded him in
recognising the importance of studying the quantitative relations of
substances. Nevertheless, no one before him so clearly foreshadowed the
doctrine of the indestructibility of matter, and it was mainly through
his teaching that the balance came to be recognised as indispensable to
the pursuit of chemistry. Before his untimely death he had succeeded
in impressing upon the science the main features which at present
characterise it.
Lavoisier was one of the most distinguished men of his age, and his
merits as a philosopher were recognised throughout Europe. Indeed,
it is not too much to say that at the time of his death he was the
dominant figure in the chemical world of the eighteenth century.
In addition to his position as a member of the _Ferme-général_ he
was made by Turgot a commissioner of the _Régie des Poudres_; and
in this capacity he effected improvements in the manufacture and
refining of saltpetre, and greatly increased the ballistic properties
of gunpowder. He became Secretary of the Committee of Agriculture,
and drew up reports on the cultivation of flax, of the potato, and
on the liming of wheat; he prepared a scheme for the establishment
of experimental farms, and for the collection and distribution of
agricultural implements. He introduced the cultivation of the beet root
in the Blesois, and improved the breed of sheep by the importation of
rams and ewes from Spain. He was successively member of the Assembly
of the Orléanais, _Député suppléant_ of the States-General, and of
the Commune of Paris. In 1791 he was named Secretary and Treasurer of
the famous Commission of Weights and Measures, out of which grew the
international system, based theoretically on a natural unit, known as
the metric system, and now adopted by most civilised countries in the
world. He was not only the administrative officer of the Commission:
he contributed to the nomenclature of the system, and directed the
determination of the physical constants on which the measurements
rested, and especially the determination of the weight of the unit
volume of water on which the value of the standard of mass was based.
Lastly he was Treasurer of the French Academy until its suppression in
1793 by the Convention, which shortly afterwards ordered the arrest
of Lavoisier and others of the Fermiers-généraux—twenty-eight in all.
They were sentenced to be executed within twenty-four hours, and their
property confiscated. Coffinhal, who pronounced their doom, declared:
“_La republique n’a pas besoin de savants_.” Thus in the fifty-first
year of his age, perished the creator of modern chemistry—a victim to
the senseless, sanguinary fury of the “Friends of the People.” His
rectitude, his public services, the purity of his private life, the
splendour of his scientific achievements—all were unheeded. As Lagrange
said to Delambre: “It required but a moment to strike off this head; a
hundred years may not suffice to reproduce such another.”
[Illustration: LAVOISIER AND BERTHOLLET
in the Laboratory of the Sorbonne, Paris.]
Of the men who were associated with Lavoisier in the creation of what
was known at the period as the antiphlogistic chemistry, the most
eminent was Berthollet.
=Claude-Louis Berthollet= was born in Savoy in 1748, and, after a
medical education, became physician to the Duke of Orleans. Devoting
himself to chemistry, in 1781 he was made a member of the Academy,
and he became Government Commissary and Director of the Gobelins,
the chief tinctorial establishment of France. Although in the main
in agreement with Lavoisier, he never wholly subscribed to the idea
that all acids contained oxygen. He discovered the bleaching power of
chlorine, prepared potassium chlorate, and investigated prussic acid
and fulminating silver.
In his _Statique Chimique_, published in 1803, he combated the
partial and imperfect views of Bergman and Geoffroy with regard to
the operation of chemical affinity, and showed that the direction
of a chemical change is modified by the relative proportion of the
reacting substances and the physical conditions—temperature, pressure,
etc.—under which the change is effected. He was one of the first to
draw attention to a class of phenomena known as reversible reactions,
and gave a number of instances of their occurrence. Berthollet
pushed his conclusions so far that he was led to doubt that chemical
combination took place in fixed and definite proportions; and his views
gave rise to a memorable controversy between him and Proust, in which
the latter eventually triumphed.
Berthollet enjoyed a great reputation in his time, and played a
considerable part in the political history of his country. It was
largely to his zeal, sagacity, and skill in developing her internal
resources at a critical period when she was hemmed round by foreign
troops and her ports blockaded by British ships, that France was
saved from conquest. His life was more than once in jeopardy when
France was governed by a Committee of Public Safety; but his honesty,
sincerity, and courage even impressed Robespierre, and he escaped the
perils of the Great Terror. He was an intimate friend of Napoleon,
and accompanied him to Egypt as a member of the Institute. He died at
Arcueil in 1822.
Davy, who visited him at his country house in 1813, says of him:—
Berthollet was a most amiable man; when the friend of Napoleon,
even, always good, conciliatory, and modest, frank and candid.
He had no airs, and many graces. In every way below La Place
in intellectual powers, he appeared superior to him in moral
qualities. Berthollet had no appearance of a man of genius; but one
could not look on La Place’s physiognomy without being convinced
that he was a very extraordinary man.
Other notable men of this period were Fourcroy, Vauquelin, Klaproth,
and Proust.
=Antoine-François Fourcroy=, the son of a pharmacist, was born at Paris
in 1755, and started his career as a dramatic author. On the advice
of Vicq d’Azir, the anatomist, he turned to medicine, and in 1784, by
the influence of Buffon, obtained the chair of Chemistry at the Jardin
du Roi, in succession to Macquer. He was an excellent teacher—clear,
orderly, and methodical. He had, indeed, a talent for oratory. This he
assiduously cultivated, and became one of the most popular lecturers of
his time in France. Ambitious and time-serving, he became embroiled in
the turbulent politics of the period, and, after a chequered career,
died, embittered and disappointed, in the fifty-fourth year of his
age. His chief services to science consisted in his works, _Système
des Connaissances Chimiques_ and _Philosophie Chimique_. These, no
less than his public lectures, did much to popularise the doctrines of
Lavoisier among his countrymen.
=Louis Nicolas Vauquelin=, the son of a Norman peasant, was born in
1763, and while a boy became assistant to an apothecary in Rouen. In
1780 he came to Paris, and entered Fourcroy’s laboratory. Much of the
experimental work published in Fourcroy’s name was actually done by
Vauquelin. He became a member of the Academy in 1791, Professor of
Chemistry at the Mining School, Assayer to the Mint, and subsequently
Professor of Chemistry at the Jardin des Plantes. On Fourcroy’s
death he was made Professor of Chemistry of the Medical Faculty of
Paris. Vauquelin was no theorist; he was, however, an excellent
practical chemist, and one of the best analysts of the period. He
made a large number of mineral analyses, more particularly for Hauy,
the crystallographer. He discovered the element _chromium_ in the
so-called red-lead ore (lead chromate) from Siberia. He also first made
known the existence of _glucinum_ in beryl. He described a method of
separating the platinum metals, and worked upon _iridium_ and _osmium_.
He investigated the _hyposulphites_, _cyanates_, and _malates_. He
discovered the presence of _benzoic acid_ in the urine of animals; with
Robiqet, he first isolated _asparagin_; with Buniva, _allantoic acid_;
and with Bouillon de la Grange, _camphoric acid_.
Vauquelin lived wholly for science, and had no other interests
than in his laboratory. He was pensioned in 1822, and died at his
birthplace—St. André d’Héberlot—in the sixty-sixth year of his age.
=Martin Heinrich Klaproth=, born in 1743 at Wernigerode, in the
Hartz, began life, like Vauquelin, as an apothecary’s apprentice at
Quedlinburg. Thence he went to Hanover, and ultimately to Berlin,
where he studied under Pott and Marggraf and entered the pharmacy of
Valentine Rose, father of Heinrich Rose, the distinguished chemist,
and Gustav Rose, the mineralogist. In 1788 he became a member of the
Berlin Academy, and, on the creation of the Berlin University in 1809,
was made Professor of Chemistry. As already stated, he was the first
chemist of eminence in Germany to adopt the antiphlogistic theory. He
was distinguished as an analyst. He discovered _tellurium_, analysed
_pitchblende_ and _uranit_, and first made known the existence of
_uranium_, _zirconium_, and _cerium_, which he termed “ochroita.” He
analysed _corundum_, and was an independent discoverer of _titanium_
and _glucinum_, termed by him _beryllium_. He made a large number of
analyses of minerals, such as leucite, chrysoberyl, hyacinth, granite,
olivin, wolfram, malachite, pyromorphite, etc. He continued actively at
work until his death, in the seventy-fourth year of his age.
Analytical chemistry is under great obligations to Klaproth. He
established a standard of accuracy never before approached; and much
of his analytical work, both as regards processes and results, is of
permanent value.
=Joseph Louis Proust=, the son of a pharmacist was born at Angers in
1761. He received his early training in chemistry from his father,
and, after studying under Rouelle in Paris, obtained an appointment
at the Salpetrière. Proust has the credit of being the first chemist
to make a balloon ascent—in a Montgolfier balloon with Pilatre de
Rozier. On the invitation of the King of Spain, he went to that
country to superintend certain chemical manufacturing processes. He
became Professor of Chemistry at the University of Salamanca, and
subsequently went to Madrid, where he was installed in a well-equipped
laboratory to enable him to examine the mineral riches of Spain. On
the breaking out of war his work was interrupted, and he was obliged
to leave Madrid. His laboratory was completely destroyed, and his
valuable collection of apparatus and specimens dissipated. Through the
good offices of Berthollet, Proust was offered a considerable sum of
money by Napoleon in order to induce him to turn his discovery of grape
sugar to practical account. Proust was, however, too broken in health
to undertake the work of a factory manager, and he retired to Mayence.
On the restoration of the Monarchy he was made a member of the French
Academy, his honorarium as an Academician being augmented by a pension
from Louis XVIII. He died in 1826, while on a visit to Angers, his
native place.
Proust is the discoverer of what is now styled “the law of constant
proportion,” which states that the same body is invariably composed
of the same elements, united in the same proportion. He was a skilful
analyst, and made numerous analyses of minerals; and he was one of the
earliest to undertake a systematic study of metallic salts of organic
acids.