[Sommaire
Doazit]
[Jean
Darcet]
[Bibliographie
Darcet]
(fichier d’origine extrait de : http://169.158.24.166/texts/pd/092/04/2/09204206.pdf, avec autorisation de l'auteur)
Revista CENIC Ciencias Químicas, Vol. 35, No. 2, 2004.
RESEÑA BIOGRAFICA
Jean Darcet
Jaime
Wisniak
Department of Chemical Engineering,
Recibido: 13 de noviembre de 2003. Aceptado: 30 de diciembre de 2003.
Palabras clave: minerales, altas temperaturas, porcelana dura, cerámica, aleación Darcet
Key words:
minerals, high temperatures, true porcelain, ceramic, Darcet’s
alloy.
RESUMEN.
Jean Darcet (1724-1801) es otro de los científicos
Franceses famosos que dedicó su vida a la educación, la
ciencia y al desarrollo de
la industria nacional en el
período crítico de
ABSTRACT. Jean Darcet (1724-1801) is another of the
famous French scientists that devoted his life to teaching, to science, and to
the development of the national industry at the critical time of the
Revolution. His well-known memoir on the behavior of
minerals under high heat led to a better classification of them and to his
discovery of the method for making true porcelain from native raw materials, a
finding that made
LIFE AND CAREER
Jean Darcet (Fig. 1) was
born on September 7, 1724, at Audignon, near Doazit, St. Sever,
In 1762 Darcet was awarded
his medical degree and although on November 18, 1762 he was appointed docteur-régent (Note 1) at the Faculty of Medicine he never
practiced medicine. His strong interest in science led him to attend the
courses in chemistry given at the Jardin du Roi by Guillaume François Rouelle (1703-1770), the most famous pharmacist of his
time. Rouelle
influenced him in such a manner that not only they started working together
Fig.1. Jean Darcet (1724-1801).
(By permission of Edgar Fahs Smith Collection,
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but also
he spent the rest of his life studying chemistry. A major factor to his
appointment to the Collège de France in 1774 was the fact
that among all the physicians being considered, he was the only who had made
chemistry his sole occupation.
Darcet, little by little, specialized in
the theoretical study of chemistry, looking for the application of theory to
practice. His opportunity came with the count Louis de Lauraguais
(1733-1824), a nobleman interested in chemistry and industrial entrepreneur. At
that time all objects made of quality porcelain were imported from
A year after Rouelle’s
death his widow carried out the wishes of her husband and as a testimony of
their confidence in him in 1771 she offered to Darcet, then 41, to marry her daughter
Françoise Amélie. The bride was then 18 years and
died in 1791 at the age of 38. They had four children, two boys (one of them
died in infancy) and two girls. When Madame Rouelle
also died, her aunt, a young sister of Madame Rouelle
kept house for him and the three children.
On December 1774 Darcet was appointed to the first chair
of experimental chemistry at the Collège de France.
His inaugural speech was symbolized by some drastic changes in the traditions
of the Collège not only because he was allowed to
give it in French instead of Latin but also without wearing the traditional
robe. The authorization for lecturing in French was more one of public
relations than factual, it was said that Latin did not have enough technical
terms to express appropriately Darcet’s
scientific terms. In fact, Darcet’s
concepts were not that different from previous scientific lectures given at the
Collége; in addition, he was very well versed in
Latin and Greek, as seen by his early occupation as a tutor in both languages.
The creation of the chair of
experimental chemistry at the Collége was accompanied
by promises from the ministers Anne Robert Jacques Turgot
(1727-1781) and Chrétien Guillaume de Malesherbes
(1721-1794) to provide the space and equipment for a research laboratory. This
turned out not to be the case, space for a laboratory was provided but not
funds for the equipment and ancillaries. Darcet had to supply his own equipment,
reagents, and fuel, which he paid from his salary (at that time 1 200 francs)
and his own private resources. He did not have much difficulty in doing so
because his wife brought him a substantial dowry, together with Rouelle’s stock and apparatus. He was a hard working
chemist, and it was a matter of pride to be teaching his science on the most
advanced level at the Collège. In 1778 he assured the
ministry that his demonstrations and experiments were as full as if he had been
giving private lectures for subscribers.
Darcet’s chemistry course at the Collège followed more or less the structure of the one
given by Rouelle, in which the knowledge of chemistry
was explained along the lines of the mineral, animal, and vegetable kingdoms.
His auditorium was always full. In 1784 he took on an assistant, Jérôme Dizet (1764-1852), a
nineteen-year-old pharmacist apprentice from his native region in Les Landes. Dizé prepared the
demonstrations and experiments and performed the same service for the course in
experimental physics, which Louis Lefêbre de Gineau (1751-1829) had begun teaching in 1786. Dizé was an extremely meticulous worker that relieved Darcet of most of
the experimental duties related to the course. Darcet taught for 27 year at the Collège de France; he became known as a remarkable teacher,
by the content of the courses he taught, the clarity of exposition, and the
logic of his reasoning.
Recognition by the Académie de Sciences came late to Darcet. On April 4, 1784, at the age of
fifty-nine, he was appointed associé chimiste supernuméraire to the Académie de Sciences in replacement of Pierre-Joseph Macquer (1718-1784), and remained a member until its
suppression in 1784. The supernumeraries were scientists of prestige, nominated
by the King without previous presentation to the Académie
and destined to become titulaires (Note 2). In 1785
the government created the Institute de France and Darcet was
among the first members of the institution.
After the occupation of
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heated
under the proper proportions with calcareous earths and stones. Darcet’s findings
helped to clarify the ideas about the classification of minerals and eventually
they also led to the improved production of true or hard porcelain in
In 1783 he read a memoir on the
action of heat on calcareous earth (calcium carbonate) where he proved that the
ability of this material to scavenge other earths and minerals during the
fusion of glass was due to its alkaline nature.
Darcet’s work on the geology of the
French of the work on viper venom by Felix Fontana (1730-1805), as well
as annotating Joseph-Louis Lagrange’s (1736-1813) translation of Seneca’s Questions
Naturelles. Darcet
was also called by the Duc d’Orleans
as a referee of Nicolas Le Blanc’s (1742-1806) proposal for converting common
salt into soda, or mineral alkali. Darcet was extremely busy at that time
and turned the matter over to Dizé. When Dize’s first attempts to reproduce Le Blanc’s results
failed, the latter requested that the initial report be delayed and that Dizé continue working with him in order to find and
overcome the source of the difficulty. Dizé agreed,
with the concurrence of Darcet,
and thus did the development of the Leblanc process begin in the laboratory of
the Collège de France.
His wide experience in industrial activities
led to his being picked by the government to participate in the direction of
several manufacturing activities of the state. For example, Darcet occupied several important
positions at the Manufacture Royale de Sèvres. First he became inspector of colors,
then one of the representatives (commissaire) of the Académie in the directing body, replacing Étienne Mignot de Montigny (1714-1782) who had recently died; and in 1784 he
became Directeur of the factory, replacing Macquer. According to Gillespie there is no evidence on the
reasons why the compte Charles Claude d’Angiviller (1730-1809) selected Darcet instead of Fourcroy
to succeed Macquer. During his tenure at Sèvres Darcet perfected the different manufacturing
procedures and demonstrated the identity between the scarlet dye
obtained from the wild cochineal of
Director of the Mint.
His many academic and industrial
activities made Darcet
very rich; he devoted part of his patrimony to different philanthropic
activities, particularly for hospitals.
In 1789, at a time when only the
esteem determined the right to vote, he was selected as Elector for the city of
At the end of 1800, the Constitution
of the year VIII, through its four assemblies, created the Senate, to which
Bonaparte incorporated all the illustrious of
The many intrigues going on at that
time in France led the Convention to charge Darcet with the macabre accusation of
manufacturing cups of gelatine using the bones of Jean-Baptiste
Molière (1622-1673), Blaise
Pascal (1623-1662), Hélöise (1101-1164) and Abélard (1079-1142), etc. Another rumour said that he had
used the bones for preparing the calcium phosphate required for manufacturing a
porcelain cup at Sèvres, on which he and friends had
drank patriotically to the Republic. He was again condemned to the guillotine
but managed to escape the night before he was to be decapitated.
Darcet died on February 12, 1801, at the
age of seventy-five, during violent intestinal spasms, probably caused by a
gout metastasis. Georges Cuvier (1769-1832)
pronounced the Éloge Funèbre.
HONORS AND
POSITIONS
Darcet received many honors
for his contributions to science, industry, and the Nation. He was a member of
the Lycée des Arts and one of its founders, Professor
of chemistry at the Collège de France, member of the Académie des Sciences, honorary member of the Collège de Pharmacie, member of
the senate; member of the Sociéte Royale
d’Agriculture, Inspector General of Assays of Coins,
and Inspector of the Manufactures Nationales de Sèvres
et des Gobelins.
Scientific
contribution
Some of the most important
contributions of Darcet
will now be described with more detail.
1. Hard
porcelain
Darcet and his patron, the count of Lauraguais, studied more than two hundred soils, minerals,
and metal oxides and eventually were able to determine the constituents and
proportions of the materials needed for the manufacture of true porcelain (porcelaine dure). Under the
direction of Darcet
the manufacture of porcelain at Sèvres achieved
numerous improvements. The changes he made in the composition of the paste
allowed the manufacture
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and burning of large vases made of one piece, which
could not be burned before but only divided into five or six related pieces.
The delicate coating of porcelain was changed and made more beautiful; he
conceived a fumigation process that was afterwards applied in the muffles of
the painting ovens in order to give the colors on
porcelain an iridescent appearance, as well as having more variegated shades;
he also developed some important improvements on the porcelain ovens
themselves. He participated in the detection and exploitation of the St. Yrieix kaolin deposits in 1768 and thus the manufacturing
enterprise at
Darcet’s results at Sèvres were so significant that it was said that “les
Saxons avoient bien le
secret de leur belle porcelaine,
mais qu’ils ne connoissoient pas l’art de faire la porcelaine”
(the Saxons have the secret of their beautiful porcelain, but do not know the
art of making porcelain).
2. Geology of the
Darcet was very fond of hiking in the
Darcet and his friend, Gaspar Monge (1746-1818), a professor
of physics at Mézierfes, used their vacations to make
barometric and temperature measurements in the Pyrenean. Darcet raised afterwards the question
that if it was certain that the air became rarified
with height, or was the reason simply the changes in air density caused by the
oscillations of the barometer? Since Darcet felt that at the top of the
mountain he could breath easily, he could not square
this fact with the claim that at higher heights air became rarified.
He believed that those who had reached higher heights had became
dizzy and bleedy simply because they had become very
tired. Darcet
thought air was a fluid like water, having essentially a constant density.
3. The burning of diamond controversy
It was generally
believed that diamond was indestructible under the action of high heat, Robert Boyle (1627-1691) was the first to study with
some precision the action of fire on diamond and Isaac Newton (1642-1727) had
predicted that diamond could be burned and had thus classified it in the class
of combustible substances. In his book Opticks
Newton, after presenting a table of the values of the ratio between the
refractive power and the density for twenty-two substances (diamond had the
largest value, 14,556) wrote: “all Bodies seem to have their refractive Power
proportional to their Densities…it seems rational to attribute the refractive
Power of all bodies chiefly, if not wholly, to the Sulphureous
Part with which they abound. And as Light congregated by a Burning glass acts
upon Sulfureous Bodies to turn them into Fire and
Flame…” Hence, according to
Between 1694 and 1695
Jean-Gaston de Médicis, Grand Duc
of Tuscany (Cosmo III), had seen in
In July 1771, Godefroide Villetaneuse and Macquer heated a diamond (to a temperature not higher than
to turn copper red) in a crucible in Macquer’s
furnace, in the presence of Darcet,
Rouelle, and others. After 20 min heating the crucible
was opened and the observers no-
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ticed that the diamond
appeared to be enveloped in a small pale phosphorescent flame. They repeated
the procedure for another half hour with the same stone and on opening the
furnace found that the diamond had been completely destroyed. An account to the
experiments was read to the Academy the following day. Further experiments were
made later by Rouelle and Darcet.
Stanislas
Marie Maillard, despite the failure of Le Blanc’s
experiment, offered three diamonds for experiment, which he surrounded very
carefully with charcoal and sand, and this time, after two hours of heating,
the diamond was found to be unchanged This result was quite unexpected by Macquer, who concluded from it, and from the flame that he
had seen before on the surface of a red-hot diamond, that diamonds were
combustible and, like other bodies, required air for their combustion.
Subsequently Maillard allowed Macquer
to repeat the experiment in the furnace of the factory at Sèvres,
with a diamond he had packed as before, to prevent contact with air. Again, the
stone was unharmed by the fire.
Antoine-Laurent Lavoisier (1743-1794), who had witnessed some of the
preceding experiments and found them quite relevant to the work he was doing on
the causes and agents of combustion, invited Louis-Claude Cadet de Gassicourt (1731-1799) and Macquer
to assist him in performing more experimental work. Their experimental set up
was now provided with the necessary ancillaries to permit collection of the
possible gases released, either by distillation or by sublimation in the cooler
parts of the apparatus. They were, however, unable to detect any product. When
the diamond was burnt in a closed vessel by means of the glass in the apparatus
designed by Lavoisier, it was found that a part of
the air in the vessel was used up as was the case with other combustible
bodies, and when lime was subsequently added it turned milky and deposited a
precipitate. When a diamond was subjected to the heat from
the Academy’s large burning-glass, it decrepitated
and split into tiny fragments, but this did not happen if the heat was applied
gradually, when the diamond slowly disappeared without giving off any smell or visible
fumes.
Sometime later
Louis-Bernard Guyton de Morveau (1737-1816)
accomplished the combustion of diamond in the presence of oxygen and suggested
that it was made of pure carbon. Additional experiences with strong heat led Darcet to prove that
rubies, sapphire, emerald, topaz, although having similar properties to diamond
had a completely different nature.
4. Soap manufacture
Darcet tried to obtain soda from marine salt, and
manufactured soap from all types of oils and fats. By the end of the eighteenth
century, the only comprehensive account of soap making then extant was the
almost 100 page long “Rapport sur
Darcet, Lelièvre, and Pelletier
also studied the methods for making hard soaps from potash soaps by the
addition of salt solution to the soft soap and boiling the mixture for several
hours. They also considered the methods for making fraudulent soaps,
particularly by the addition of water, salt, alum, starch, chalk, and lard.
According to them, the only way of identifying the adulterants was by analysis.
The final part of the
report was a set of instructions for those who wanted to make soap by
themselves.
5. Alloys
During his work on
fusible alloys Darcet
developed (1775) an alloy made of three part of tin, eight of bismuth, and five
of lead that was liquid at the temperature of boiling water and latter found
use in the production of stereotype plates (Note 3). Further
work on alloys, some in collaboration with Bertrand. Pelletier
(1761-1797), his assistant and demonstrateur at the Collége de France, enabled Darcet to develop a method of separating
the copper from church bells and show how these could be melted down to cast
cannon. In order to try to solve the monetary deficit, the Assemblée
Nationale Constituante
decreed in 1789 that all the ecclesiastical property should be put at the
disposition of the Nation; as a consequence many churches fell in disuse and a
large number of bells came into the market and with them the interest in the
large quantity of copper available in the form of bell metal, an al-
3. The name fusible metals is now applied to a variety
of alloys, usually composed of bismuth, lead, and tin, which possess the
property of melting at comparatively low temperatures, (between 91 to
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loy containing 20 to 25 % of tin. Several
possibilities were considered for their use: to sell them as such, to separate
the components, or to alloy them with a certain amount of copper in order to
make them ductile enough so that they could be used to manufacture cannons,
coins, or statues. Darcet
in collaboration with Pelletier, and Fourcroy made
the most important contributions to the subject. Darcet and Pelletier’s method was based
on the oxidation of the bell alloy with manganese oxide, which attacked the tin
before the copper and gave a good yield. Fourcroy’s
approach was in two different directions, based on the variable affinity that
oxygen has for metals. In one of them, the bell metal was heated it in a
crucible in the presence of air until the increase in weight showed that
sufficient oxygen had been absorbed to convert all the tin into oxide, followed
by heating the molten metal in a closed crucible, avoiding the possibility of
further absorption of oxygen. During this second heating stage the copper oxide
was reduced by the unreacted tin and at the end of
the reaction all the tin was oxidized and could be separated from the molten
copper. Fourcroy’s second approach was based on the
oxidation of the tin by heating the alloy with certain metallic oxides; he
achieved good separation with black oxide of manganese but litharge and oxide
of arsenic were found to be unsatisfactory.
As a result, in 1793, when large
quantities of copper were urgently needed for manufacturing cannon, the
Committee of Public Safety decreed the destruction of all church bells.
Instructions describing both Pelletier’s and Fourcroy’s
methods were published in detail and both were recommended. Fourcroy’s
procedure proved to be cheaper, although both helped provide copper to the
revolutionary government during the many wars it held during
its
existence.
6.
Miscellaneous
The logical reform of the chemical
language proposed by Lavoisier, Fourcroy,
Berthollet, and Guyton de Morveau,
did not gain a complete approval of the referees appointed by the Académie des Sciences in 1787, Antoine Baumé
(1728-1804), Louis-Claude Cadet de Gassicourt
(1731-1799), Darcet,
and Balthazar-Georges Sage (1740-1824). The three were supporters of the
phlogiston theory and hence they recommended: “Nous pensons qu’il
faut soumettre cette théorie
nouvelle (la chimie pneumatique) ainsi que sa nomenclature, à l’épreuve du
temps, au dire des expériences, au balancement des opinions qui en est la
suivre; enfin au jugement du public comme au seul tribunal d’où elles doivent
et puissent ressortir. Alors ce ne sera plus une théorie, cela deviendra un
enchaînement de vérités, ou une erreur. Dans le premiere
cas, elle donnera une base solide de plus aux connaissances humaines, dans le
second, elle rentrera dans l’oubli avec toutes les théories et les systèmes de
physique qui l’ont precede” (We
believe necessary to subject this new theory, as well as its nomenclature, to the test of
time, to the experiments,
to the doubts it has raised, in short, to the judgment of the public as the only tribunal. Then it will not be a theory; it will become a chain of facts or an
error. In the first case it will provide a solid base for solid human
knowledge; in the second case, it will go into oblivion with all other theories
and systems that have preceded it).
BIBLIOGRAPHY
1. Cuvier G., Notice Historique Sur Jean Darcet, Mémoirs de l’Institut, 4, 74-88, 1801.
2. Cuvier G., Éloge Historique de Jean Darcet, Recueil des Éloges Historiques, I, 165-185, 1819.
3. Coleby L.J.M.
The Chemical Studies of P. J. Macquer, George Allen
& Unwin,
4. Cuzacq R. Le Chimiste Jean Darcet et sa Famille, Editions Jean-Lacoste, Mont-de-Marsan, 1955.
5. Wisniak J. Guillaume-François
Rouelle, Educ. Quím., submitted (2004).
6. Gillispie
C.C. Science and Polity in
7. Darcet J. Mémoire sur
8. Darcet J. Second Mémoire sur
9. Pott
J.H. Fortsetzung Derer Chymischen Untersuchungen Welche von der Lithogeognosie, Oder Erkäntniss und Bearbeitung derer Steine und Erden Specieller Handeln, Christian Friedrich Voss, Potsdamm,
1746.
10. Darcet J. Mémoire sur
11. Darcet J. Rapport sur l’Électricité Dans les Maladies Nerveuses, Paris, 1785.
12. Lelièvre C.H., Darcet J., Giroud A. Rapport sur les Divers Moyens d’Extraire Avec Avantage le Sel de Soude du Sel Marin, De l’Imprimerie du Comité de Salut Public, Paris, 1795. Published also in Ann. Chim., 19 (1797) 58-156.
13. Fourcroy
A., Darcet J., Guyton
de Morveau L.B. Rapport Sur les Couleurs Pour
14. Darcet J. L’Ètat Actuel des Montagnes des Pyrénées et les Causes de leur Dégradation, J. Phys., 8, 403-425, 1776.
15. Darcet J. Mémoire sur le Diamant et Quelques Autres Pierres Précieuses, Hist. Acad. Royale de Sciences, 1771.
16. Macquer P.J. Dictionnaire de Chymie, Lacombe, Paris; Vol. 1, 499-524, 1766.
17.
18. Rouelle G.F., Darcet J. Procés-verbal des Expériences Faites Dans le Laboratoire de M. Rouelle, Sur Plusieurs Diamans & Pierres, Paris, 1772.
19. Rouelle
G.F., Darcet J. Expériences Nouvelles
sur
20. Lavoisier
A.L. Premier Mémoire Sur
21. Lavoisier,
A. L., Second Mémoire Sur
22. De Montigny T., Macquer P.J., Cadet L.C., Lavoisier A.J. Premier Essai du Grand Verre Ardent de Mr. Trudaine Établi au Jardin de l’Infante au Commencement du Mois d’Octobre de l’Année 1774, Mém. Acad. Royale Sci., 62-72, 1774.
23. Dizé M. J.J. Précis Historique Sur
24. Darcet. J., Lelièvre
C.H., Pelletier B. Rapport sur
25. Darcet J. Expériences sur l’Alliage Fusible de Plomb, de Bismuth et d’Étain, Hist. Acad. Royale de Sciences, 1775.
26. Pelletier B., Darcet J. Instruction sur l’Art de Séparer le Cuivre du Métal des Cloches. Publié par Ordre du Comité de Salut Public, De l’Imprimerie du Comité de Salut Public, Paris, 1794.
27. Fourcroy A.F. Recherches Sur le Métal des Cloches, et Sur les Moyens d’en Séparer le Cuivre, Ann. Chim., 9, 305-352, 1791.
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[Sommaire
Doazit]
[Jean
Darcet]
[Bibliographie
Darcet]