Claude Louis Berthollet was a French chemist. He was also a chemistry teacher and, with his contemporary Pierre-Simon de Laplace, a patron of young French scientists.
Background
Claude Louis Berthollet was born on December 9, 1748, in Talloires, then part of the Duchy of Savoy (present-day France), the son of Louis Berthollet and Philiberte Donier. He came from a French family that had emigrated to Savoy during the previous century and had become members of the noblesse de robe.
Education
Berthollet first studied at the collèges in Annecy and Chambéry, and later qualified as a physician at the University of Turin in 1770. In 1770, with the patronage of a famed Genevan physician, Theodore Tronchin, he established himself in Paris as physician to the wife of duke of Orléans.
In 1778 Berthollet became a French citizen and began the process of obtaining a medical license from the Paris Faculty of Medicine. Berthollet continued his medical practice for several years while embarking upon a scientific career.
During the 1770s Claude Louis Berthollet had acquired an active interest in chemistry. By 1780 he had presented eighteen mémoires to the Académie des Sciences. He was admitted to the Académie as an adjoint in 1780, promoted to associé in 1785, and promoted to its highest position, pensionnaire, in 1792.
By the early 1780s, Berthollet had gained entrance to the circle of chemists that surrounded Antoine-Laurent Lavoisier, who had been developing his new oxygen-based, antiphlogistic theory of chemistry. Although Berthollet at first criticized features of the new chemistry (and never did accept Lavoisier's oxygen-based theory of acidification), he was the first chemist of Lavoisier's circle to formally and publicly become a supporter. In 1787 he joined with Lavoisier's other close associates (including Antoine Fourcroy and Louis-Bernard Guyton de Morveau) to forge a chemical nomenclature that would be coordinated with the new chemistry.
In 1784 Berthollet was appointed to the post of inspector of the dye works and director of manufacture at the Gobelin tapestry works. While studying the properties of newly discovered chlorine gas ("dephlogisticated marine acid"), Berthollet recognized its superior bleaching properties, and he developed a chlorine-based bleach. In 1791 Berthollet published Élémens de l'art de la teinture, a systematic study and scientific discussion of the nature of dyeing. Berthollet also contributed to another scientific study of a major industry of the 1780s: ironmaking and steelmaking. In this study an attempt was made to provide a scientific explanation of the different kinds of iron (cast, wrought) and steel based on degrees of reduction (removal of oxygen) of the ore and subsequent combination with carbon. A third area of practical chemistry in which Berthollet was active was munitions. His most significant work in this area was the development of a potassium chlorate–based explosive (which turned out to be too powerful for use as a munition).
During the French Revolution and the Napoleonic era, Berthollet came to play active civic and political roles in France. During the Revolution, he was one of the scientists entrusted by the Committee of Public Safety with the emergency amplification of munitions production. He taught at the École Normale and was one of the founders of the École Polytechnique. He became a friend of Napoleon Bonaparte, whom he accompanied to Egypt in 1798, and in Egypt helped to set up a scientific institute along the lines of the Parisian Académie. Napoleon showered Berthollet with honours, including a senatorial appointment, medals, and the title of count. In 1806 Napoleon also bailed him out with a considerable loan to settle debts Berthollet had incurred after turning over his financial affairs to his wife. Thanks to income from his position as a senator, he soon recovered his fortune and used some of it to outfit his Arcueil laboratory. In his declining years, Berthollet was accused unjustly of having abandoned his benefactor in 1814, when he signed the Senate’s bill deposing Napoleon after his defeat at the Battle of Waterloo. Berthollet’s final years were plagued by financial and health problems.
Although Berthollet never published a textbook of chemistry, he did publish the Essai de statique chimique (1803), an ambitious work that attempted to provide a systematic theoretical foundation for chemistry.
Claude Louis Berthollet was a strong supporter of Napoleon Bonaparte.
Views
It was at Arcueil that he wrote the controversial “Essai de statique chimique” (1803; “Chemical Equilibria”), aimed at establishing the general laws of chemical reactions and a systematic approach to physical chemistry. The idea for this sprang from notions discussed with Lavoisier about the role of chemical affinities and Berthollet’s decade-long set of experiments with double decomposition. In particular, he was puzzled over the natural formation of natron (a hydrated sodium carbonate) from a mixture of limestone (calcium carbonate) and seawater (containing sodium chloride) in a valley near Cairo. In the laboratory, reactions with the same components yielded an inverse product. This suggested to him that the concentration of chemicals was a key factor in determining how a reaction would end, an idea that was at odds with the prevailing views on elective affinities. In a paper presented to the Institut on his return from Egypt that was recognized as fundamental, and was quickly translated into English and German, he set forth the principle that affinities did not have absolute values but were modified by physical conditions of the reaction, especially the concentration of reagents. It was this assertion that eventually led to the more precise formulation of the law of mass action in the mid-19th century, and it embroiled him in a major controversy with the French chemist Joseph-Louis Proust starting in 1804. In turn, the Berthollet-Proust debates were central to the establishment of the atomic theory by the English chemist John Dalton.
According to Berthollet’s theory, physical conditions surrounding reagents, including temperature and solubility, often offset the effect of affinities, thereby determining the direction of the reaction. Employing an analogy current in physics, he asserted that chemical reactions seek a static equilibrium, hence the title of his essay. Because it was thought that the molecules in a gaseous reaction were separated by caloric (a hypothetical weightless substance thought to account for combustion and the flow of heat), Berthollet insisted they had to be carried out at certain temperatures in order to be successful. For this research, Berthollet was assisted by his student Joseph Louis Gay-Lussac, with whom he engaged in experiments in the laboratory as well as in a balloon.
In his essay Berthollet also challenged the idea that compounds unite in definite proportions, claiming instead that they could combine in variable proportions between certain limits, depending on physical circumstances. His theories were based on assumptions about the “atomic” character of elements that were subjected to various forces in chemical reactions, not merely those of attraction by affinity, and he attempted to account for these other forces by focusing on the mass of reactants and on cohesion and elasticity in different states of matter. These complex (and ultimately successful) ideas were challenged by Proust, whose views about definite proportions prevailed in the immediate aftermath of their debate. Berthollet was impressed by the newly proposed atomic theory, and he accepted that some reactions constantly combine in definite proportions. Nonetheless, in the long preface to the French translation of British chemist Thomas Thomson’s System of Chemistry (1809), which explained atomic theory, he continued to object to generalizing this fact into a law applying to all reactions.
Membership
In April 1789 Berthollet was elected a Fellow of the Royal Society of London. In 1801, he was elected a foreign member of the Royal Swedish Academy of Sciences. In 1809, Berthollet was chosen an associate member first class of the Royal Institute of the Netherlands, predecessor of the Royal Netherlands Academy of Arts and Sciences. He was elected an Honorary Fellow of the Royal Society of Edinburgh in 1820 and a Foreign Honorary Member of the American Academy of Arts and Sciences in 1822.
Royal Swedish Academy of Sciences
,
Sweden
1801
Royal Institute of the Netherlands
,
Netherlands
1809
Royal Society of London
1789
Royal Society of Edinburgh
,
United Kingdom
1820
American Academy of Arts and Sciences
,
United States
1822
Connections
In 1779, Claude Berthollet married Marguerite-Marie Baur, who bore him their only son, Amédée, in 1780.