Time has only underscored Lagrange's assessment of Lavoisier.
He died at the age of 51 at the height of his creative powers and after establishing modern chemistry on a firm footing. Who
knows what more he might have achieved had he lived? Every modern chemist, indeed every chemist for the last 200 years, lives
in the shadow and on the legacy of Lavoisier. E.J. Holmyard in his book (Chemistry to the time of Dalton (OUP, Oxford
1925) identified Lavoisier and Dalton as the founders of modern chemistry:
"The coping-stones of eighteenth century chemistry, which
are at the same time the foundation-stones of the modern science, were laid by Antoine Laurent Lavoisier (1743-1794) and John
Dalton (1766-1844)."
In 1994 we celebrate the 200th. anniversary of the death of Lavoisier
and the 150th. anniversary of the death of Dalton, and coincidentally the death of Linus Pauling, the greatest chemist of
the 20th. century.
It is instructive 200 years later to look back at Lavoisier's
life and achievements, to the very birth of modern chemistry. Before he died the phlogiston theory was dead, although some
chemists like Joseph Priestley refused to acknowledge it in their lifetimes, and the oxygen theory of combustion and respiration
was firmly established. Lavoisier laid his personal claim to be the author of the chemical revolution in 1792:
"This theory is not, as I have heard it called, the theory
of the French chemists in general, it is mine, and it is a possession to which I lay claim before my contemporaries
and before posterity. Others, no doubt, have given it new degrees of perfection, but I hope that one will not be able to deny
me the whole theory of oxidation and combustion; the analysis and decomposition of air by metals and combustible bodies; the
theory of the formation of acids; more exact knowledge of a great number of acids, notably vegetable acids;the first ideas
on the composition of plant and animal substances, and the theory of respiration."
A chronology of the main events in Lavoisier's life is given
in Box 1.
His early years
Antoine-Laurent Lavoisier was born on August 26th. 1743 in the
Marais district of Paris, the first child of Jean-Antoine Lavoisier (a lawyer) and Emilie (ne Punctis), the daughter of a
well-connected lawyer. A sister, Marie, was born in 1745 and in 1748 his mother died. They all went to live with Mme Punctis,
his maternal grandmother. Lavoisier stayed in this house until he was married in 1771. From 1754 to 1760 he went to school
at the College-Mazurin, where he won several prizes, including one in his second year for industry in his studies! In 1760
his sister died at the age of 15.
On leaving school he entered the School of Law and qualified
as a Bachelor of Law in 1763 and Licentiate in 1764. At school his initial interest was in art and literature and he wanted
to be a writer. Later he developed an interest in science while still at school and while studying law he developed this interest
further in his spare time under a number of remarkable teachers: the astronomer and mathematician de Lacaille, the botanist
de Jussieu, the geologist Guettard and the chemist Rouelle. Lavoisier's science was marked by its breadth of interest and
this background in a number of scientific disciplines, as well as his classical education, was a vital part of his later success
in many fields of science. As well as attending their lectures he also worked with them in the laboratory and did fieldwork,
learning practical skills as well as theory.
_________________________________
Box 1 Chronology of Lavoisier's life
26/8/1743 Born in Paris
1754-1760 Attended the Collége Mazurin in Paris
1763 Bachelor of Law
1763 Attended chemistry lectures by G.F.Rouelle
1765 Gold medal of the Academy of Sciences for a paper on lighting
a city
1768 Elected member of the Academy of Sciences
1768 Joined the company
Fermé-Génerale, which collected taxes for the government
1771 Married Marie Paulze (then aged 14)
1772 Started to investigate combustion and the calcination of
metals
1774 Published Opuscules Physiques et Chymiques
1774 Joseph Priestley visits in Paris in October
1775 Reports on the production and properties of vital air
1775 Joined the new gunpowder commission, Regie des Poudres
1776 Moved to live and work at the Royal Arsenal (until 1792)
1778 Started scientific farming at Fréchines
1783 Sur la Chaleur (with Pierre Laplace)
1783 Demonstrated the formation and decomposition of water
1787 Methode de
Nomenclature Chimique (with de Morveau, Berthollet and Fourcroy)
1789 Published Traité
Élémentaire de Chimie (The Elements of Chemistry)
1789-90 Studied human metabolism (with A.Séguin)
1791 The Fermé-Génerale suppressed
1792 Started work
on a complete edition of his memoirs (intended to be in eight volumes)
1792 Resigned his
post with the Gunpowder Commission and left the Royal Arsenal
4/11/1793 Arrest of former members of the Fermé-Génerale ordered
28/11/1793 Lavoisier gives himself up and is imprisoned
7-8/5/94 Lavoisier
tried before the Revolutionary Tribunal and condemned on false charges
8/5/1794 Lavoisier
guillotined with his fellow farmer-generals and his father-in-law
___________________________________
He studied chemistry under Guillame-Francois Rouelle who taught
chemistry at the Jardin du Roi from 1742-1768. Rouelle had an international reputation as a teacher and is remembered for
his classification of salts by their crystal forms, and for his chemical lectures. He was a great popularised of chemistry
and like Davy and Faraday at a later date in England, society flocked to hear Rouelle's demonstration lectures. He was the
demonstrator in chemistry and it was the custom in France at that time for the Professor of Chemistry and his demonstrator
to give the lectures in tandem: the Professor would first deal with the chemical theory and leave, and then the demonstrator
would take over and follow with experiments to support the Professor's ideas. Rouelle's Professor was Boudelin and he would
end his part of the lecture by saying:
"Such, gentlemen, are the principles and the theory of this
operation, as the demonstrator will now prove to you by his experiments."
He would then leave and Rouelle would enter. Unfortunately, Rouelle's
experiments often disproved or contradicted the Professor's theory, but people flocked to see Rouelle's demonstrations. He
was the greatest chemical educator of his time and Lavoisier was to be his most famous pupil. Rouelle came in full dress and
as the lecture proceeded he would strip off item by item, hanging has clothes on bits of apparatus, as he warmed up. Lavoisier
obtained a copy of Diderot's notes on Rouelle's lectures, which he studied at his leisure, adding his own notes and comments.
He also worked with Rouelle in his laboratory.
As well as chemistry, Lavoisier extended his studies to anatomy,
mathematics and meteorology, which was to become one of his life-long interests (much like John Dalton) and he made regular
observations for 30 years.
His scientific work
Lavoisier's scientific career was to last only 30 years but he
packed an immense amount of work into that period, despite many other activities that took up his time. He published his first
chemical memoir (or paper) when he was only 22 and in 1768 he was elected as a member of the prestigious Académie des Sciences,
France's most important scientific organisation (equivalent to the Royal Society in England). Around the same time he made
the fateful move of seeking to increase his personal wealth (based on legacies) by becoming a member of the Fermiers-Généraux
(Farmers-General), a tax-collecting syndicate. His membership of this reviled institution, despite his own irreproachable
conduct and honesty, was to be the direct cause of his arraignment by the forces of the French Revolution and his execution
a quarter of a century later.
From 1770 to 1775 he performed his key experiments on the combustion
of first non-metals and then metals which were to destroy both the phlogiston theory and also Boyle's idea that heat, a material
substance, passed through the container from the fire and resulted in an increase in mass when a metal was heated in air.
Lavoisier disagreed with Boyle, as he said:
"If the increase in weight of metals calcined in closed vessels
is due, as Boyle thought, to the addition of the matter of flame and fire which penetrates the pores of the glass and combines
with the metal, it follows that if, after having introduced a known quantity of metal into a glass vessel, and having sealed
it hermetically, one determines its weight exactly; and that if one than proceeds to the calcination in a charcoal fire, as
Boyle did; and lastly that if one then reweighs the same vessel after the calcination, before opening it, its weight ought
to be found to have increased by the whole of the quantity of the matter of fire which entered during the calcination.
If, on the contrary ... the increase in weight of the metallic
calx is not due to the combination of the matter of fire nor to any exterior matter whatever, but to the fixation of a portion
of the air contained in the space of the vessel, the vessel ought not to weigh more after the calcination than before, it
ought merely to be found partly empty of air, and the increase in weight of the vessel should take place only at the moment
when the missing portion of air is allowed to enter."
Lavoisier put his ideas to the test by careful, systematic experiments
using the most sensitive balance he could obtain. He had this to say on the importance of careful measurement:
"As the usefulness and accuracy of chemistry depend entirely
upon the determination of the weights of the ingredients and products, too much precision cannot be employed in this part
of the subject, and for this purpose we must be provided with good instruments."
The results clearly showed that his ideas were correct and the
increase in weight of a metal when heated to form a calx (oxide) was due to combination with part of the air, not to the absorption
of the hypothetical 'matter of fire', nor to the equally hypothetical phlogiston. Other experiments were done to consolidate
his views and he then could state categorically in 1774:
First, that one cannot calcine an unlimited quantity of tin
in a given quantity of air;
Second, that the quantity of metal calcined is greater in
a large vessel than in a small one, although it cannot yet be affirmed that the quantity of metal calcined is exactly proportional
to the capacity of the vessels.
Third, that the hermetically sealed vessels, weighed before
and after the calcination of the portion of tin they contain, show no difference in weight, which clearly proves that the
increase in weight of the metal comes neither from the material of the fire nor from any matter exterior to the vessel.
Fourth, that in every calcination of tin, the increase in
weight of the metal is, fairly exactly, equal to the weight of the quantity of air absorbed, which proves that the portion
of the air that combines with the metal during the calcination, has a specific gravity nearly equal to that of atmospheric
air.
I may add that, from certain considerations drawn from actual
experiments made upon the calcination of metals in closed vessels, considerations which it would be difficult for me to explain
to the reader without going into too great detail, I am led to believe that the portion of the air which combines with metals
is slightly heavier than atmospheric air, and that that which remains after the calcination is, on the contrary, rather lighter.
Atmospheric air, on this assumption, would form, relatively to the specific gravity, a mean result between these two airs."
At this point (October 1774) an important event occurred when
Lavoisier met the English chemist, Joseph Priestley, who was visiting France. Priestley told Lavoisier of his recent discovery
of dephlogisticated air (oxygen) by heating mercury calx (oxide). Lavoisier immediately linked this new gas with his active
component of the atmosphere and over the winter of 1774-75 he repeated and extended Priestley's experiments. He heated the
red calx of mercury with carbon and obtained mercury and 'fixed air' (carbon dioxide); he then heated the red calx alone and
obtained 'respirable or vital air'. He investigated these changes quantitatively and also studied the chemical and physiological
properties of the new gas, repeating Priestley's work. He reported his findings to the Acadmie des Sciences in 1775 (without
acknowledging Priestley's work) but his conclusions he drew from his measurements were his own:
"It thus appears to be proved that the principle which combines
with metals during their calcination, and which increase their weight, is nothing else than the purest portion of the very
air which surrounds us, which we breathe, and which passes, during this operation, from the gaseous state to the solid state;
if, therefore, one obtains it in the from of fixed air in all metallic reductions where carbon is used, this effect is due
to the combination of the carbon with the pure portion of the air. It is, indeed, very probable that all metallic cases would,
like that of mercury, give nothing but 'eminently respirable air' if one could reduce them all without the addition of any
other substances, as one reduces red precipitate of mercury per se."
(His failure to acknowledge what he borrowed from Priestley in
his work on oxygen, and later in 1783 what he borrowed from Cavendish in his work on the composition of water, have generated
immense controversies between the English and French schools as to who discovered what first. This is well illustrated by
the 'discussion' by T.E.Thorpe in Essays on Historical Chemistry chs. VI and VII, Macmillan, London 1902)
His crucial experiment is the one which has come to be called
"Lavoisier's Experiment", and is described in Box 2 in his own words, taken from the 1789 Traité Élémentaire de la Chimie
(Translated into English in 1790 as The Elements of Chemistry, a great title for a great book and still available as
a Dover reprint). Notice the clarity of the language and style in which it is written (in the first person), and the emphasis
on describing exactly what was done and on measuring the changes observed quantitatively. It is not cluttered with theory
or strange terminology, and it says no more and no less than the experiment demonstrates.
He had not yet publicly attacked the phlogiston theory, although
he made no use of it in his papers and he had been steadily demolishing its foundations with his experiments. However, in
1783 he published Reflexions sur Phlogistique (Reflections on Phlogiston), which made his position clear and
also brought out the opposition. He destroyed the citadel of Phlogiston with his careful experiments, his rigorous logic and
his well-chosen words:
"It is time to recall chemistry to a more rigorous method
of reasoning; to strip away the facts with which this science is enriched every day from that which reasoning and prejudices
add thereto; to distinguish fact and observation from that which is systematic and hypothetical; finally, to mark the limit,
so to speak, to which chemical knowledge has arrived, in order that those who follow us may set out with confidence from this
point to advance the science ..
Chemists have made of phlogiston a vague principle which is
not rigorously defined, and which consequently adapts itself to all explanations into which it may be brought. Sometimes this
principle is heavy, and sometimes it is not; sometimes it is free fire, sometimes it is fire combined with the earthy element;
sometimes it passes through the pores of vessels, and sometimes they are impenetrable to it. It explains at once causticity
and non-causticity, transparency and opacity, colours and the absence of colours. It is a virtual Proteus which changes its
form at every instant."
Since 1775 he had done many more experiments and showed that
non-metals combined with his respirable air to give acids. However, he now decided to change his name for this 'vital air'
that Priestley had discovered:
"I shall for the future call dephlogisticated air or eminently
respirable air by the name of the acidifying principle, or, if the same meaning is preferred in a Greek word, by that of the
oxygine principle."
In English this new name became oxygen. Professor Henry Armstrong,
the famous 19th. century English chemist and educator of, said this of Lavoisier's naming of oxygen:
"In designing the word Oxygen Lavoisier rose to the greatest
height of his unparalleled genius. Not only is the word a monument to his astounding insight into chemical phenomena, to his
philosophic power; it is also proof of a deep philological feeling and acumen, as well as of his sense of the beauty of words.
Think of the astounding step he took, after his instant appreciation of Priestley's discovery, in translating the old nonconformist's
ponderous reminder of the doubtful past of our science conveyed in the name Dephlogisticated Air into an all-significant
word of the aural and lingual perfection of Oxygen .... think of him as the pioneer who not only sought to put system into
the souls of chemists but also tipped their tongues with harmony."
Lavoisier had overturned over 50 years of chemical theory and
had stepped on the toes of all the famous and influential chemists of his time. Many older chemists rejected his views and
stuck to the old theory. The Swedish chemist Scheele wrote to Bergman in 1784:
"Would it be so difficult to convince Lavoisier that his system
of acids is not to everybody's taste? Nitric acid composed of pure air and nitrous air, aerial acid of carbon and pure air,
sulphuric acid of sulphur and pure air!.... Is it credible? ... I will rather place my faith in what the English say."
The Irish chemist Richard Kirwan initially rejected the new ideas
but then in 1791 publicly accepted Lavoisier's views:
"At last I am laying down my arms and abandoning phlogiston.
I see clearly that there is no authentic experiment in which the production of fixed air from pure inflammable air has been
demonstrated, and that being so, it is impossible to maintain the system of phlogiston .. I myself will give a refutation
of my own essay on phlogiston."
Henry Cavendish and Joseph Priestley remained believers in phlogiston
until their deaths, although Black in Edinburgh, Klaproth in Germany, Bergman in Sweden, and most American and Russian chemists
accepted the validity of Lavoisier's views. The chemical revolution, a relatively bloodless coup, was over during Lavoisier's
short lifetime, although in his paper of 1785 he himself was more pessimistic of the adoption of his new ideas:
"I do not expect that my ideas will be adopted all at once;
the human mind adjusts itself to a certain point of view, and those who have looked at nature from one standpoint, during
a portion of their life, adopt new ideas only with difficulty; it is, then, for time to confirm or to reject the opinions
which I have brought forward. Meanwhile, I see with great satisfaction that young people who begin to staidly the science
without prejudice, that mathematicians and physicists who come fresh to chemical truths, no longer believe in phlogiston in
the way in which Stahl presented it, and look upon the whole of this doctrine as a scaffolding more embarrassing than useful
for the continuance of the structure of chemical science."
In 1791 Joseph Black wrote to Lavoisier, as follows:
"The numerous experiments which you have made on a large scale,
and which you have so well devised, have been pursued with so much care and with such scrupulous attention to details, that
nothing can be more satisfactory than the proofs you have obtained. The system which you have based on the facts is so intimately
connected with them, is so simple and so intelligible, that it must become more and more generally approved and adopted by
a great number of chemists who have long been accustomed to the old system .... Having for thirty years believed and taught
the doctrine of phlogiston as it was understood before the discovery of your system, I, for a long time, felt inimical to
the new system, which represented as absurd that which I had hitherto regarded as sound doctrine; but this enmity, which springs
only from the force of habit, has gradually diminished, subdued by the clearness of your proofs and the soundness of your plan."
Another important contribution Lavoisier made to chemistry was
to revise the names used in chemistry. He worked on this for several years (1782-1787) with de Morveau, Berthollet and Fourcroy,
and in 1787 they published Methode de Nomenclature Chimique (Methods of Chemical Nomenclature). If Lavoisier had done
nothing else this alone would have ensured his place in chemistry's Hall of Fame. Until this time the language of chemistry
was a confusing mess of unsystematic names, with many different names for the same substance and no way of relating the name
to the chemical composition. Overnight Lavoisier and his French colleagues swept away the alchemical accretions of centuries
and pot in place a system, which remained essentially unchanged until this century and still provides the basis of chemical
nomenclature. Chemistry was full of compounds such as Epsom Salts, Fuming Liquor of Libavius, Butter of Arsenic, Oil of Vitriol
etc. Lavoisier had the job of drawing up and explaining the principles on which the new nomenclature was to be founded.
Box 2 Lavoisier's Experiment
"I took a matrass [A] of about 36 cubical inches capacity,
having a long neck BCDE, of six or seven lines internal diameter, and having bent the neck as in [the figure], to allow of
its being placed in the furnace MMNN, in such manner that the extremity of its neck E might be inserted under the bell-glass
FG, placed in a trough of quicksilver RRSS; I introduced four ounces of pure mercury into the matrass, and, by means of a
syphon, exhausted the air in the receiver FG, so as to raise the quicksilver to LL, and I carefully marked the height at which
it stood, by pasting on a slip of paper. Having accurately noted the height of the thermometer and barometer, I lighted a
fire in the furnace MMNN, which I kept up almost continuously during twelve days, so as to keep the quicksilver always very
near its boiling point.
