Berthollet, Claude-Louis

views updated May 18 2018

Berthollet, Claude-Louis

FRENCH CHEMIST
1748–1822

Claude-Louis Berthollet was influential in four areas: theoretical chemistry, experimental chemistry, practical chemistry, and chemical writing. He was also a chemistry teacher and, with his contemporary Pierre-Simon de Laplace, a patron of young French scientists. Born in 1748 in the town of Talloire, near Annecy, France, Berthollet studied medicine at the University of Turin. Arriving in Paris in 1772, he soon found a medical patron in one of the great Parisian aristocrats, Louis-Philippe, duke of Orléans. To consolidate his professional status, Berthollet obtained a medical degree at the University of Paris and continued to practice medicine until the mid-1780s. During the 1770s he 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. Under the aegis of Napoleon, Berthollet was made a count, a senator of Montpellier, and a grand officier of the Légion d'Honneur.

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. Like his predecessors, Berthollet conceived of the microscopic-level forces by which chemical substances "attracted" one another as being the same as or analogous to gravity. But Berthollet challenged his predecessors' view that the strengths of chemical affinity forces were determined solely by the nature of the reagents and were invariant under all physical and chemical condition. He held that factors such as the masses of the reagents, their physical states before and after the reaction, and general physical circumstances could affect the directions of reactions and even the combining proportions of their products.

Regarding combining proportions, Berthollet asserted that chemical reagents in continuous ranges of weight proportions could combine, depending on the masses of the reagents and the physical circumstances of the reactions. By this time, Joseph-Louis Proust had already set forth his general assertion that true chemical combination was always marked by fixed-weight proportions of the reagents. Berthollet and Proust argued the issue in print for several years without any resolution of the argument. What "settled" the issue was the ascendancy of John Dalton's chemical atomic theory(1808), which in its laws of definite and multiple proportions supported Proust's position.

see also Dalton, John; Lavoisier, Antoine.

Seymour Mauskopf

Chemistry: Foundations and Applications Mauskopf, Seymour

Claude Louis Berthollet

views updated May 21 2018

Claude Louis Berthollet

The French chemist Claude Louis Berthollet (1748-1822) made many original contributions to both theoretical and applied chemistry. He was one of the foremost disciples of Lavoisier.

Claude Louis Berthollet was born on Dec. 9, 1748, in the village of Galloire on Lake Annecy. He attended the University of Turin in Italy, where he graduated in medicine in 1770. He moved to Paris in 1772 to study chemistry.

In 1778 Berthollet married and took a second doctorate in medicine at the University of Paris, where his Italian degree was not recognized. By 1780 his published research on chemistry had earned him admission to the Royal Academy of Sciences in Paris, and 4 years later he was appointed director of the Gobelin tapestry works. Here he made a special study of the chemistry of dyeing, on which he published an important two-volume work in 1791.

In 1785 Berthollet adopted the new system of chemistry based upon the oxidation theory of combustion, developed by the French chemist A. L. Lavoisier. In the same year Berthollet published an important paper on chlorine, describing the bleaching action of this gas in a solution of alkali, which revolutionized the bleaching industry. Unlike his mentor Lavoisier, Berthollet emerged from the French Revolution unscathed, having served the Revolutionary government as an adviser on technical matters.

A Scientific Debate

Berthollet's career reached its climax during the Napoleonic era. In 1798 Napoleon, who had a well-informed interest in science, chose Berthollet to accompany him on the expedition to Egypt as a scientific adviser. Berthollet became a prominent member of the scientific and archeological institute which Napoleon established in Cairo. It was to this institute that Berthollet read his first papers on the subject of chemical affinity, that is, the forces by which chemical substances are attracted to one another. These papers formed the bases of his two important works on theoretical chemistry, Researches into the Laws of Chemical Affinity (1801) and Essay on Chemical Statics (1803). Berthollet maintained that the masses of substances involved in a chemical reaction could influence the products and that a chemical reaction could be reversed by varying the quantities of the substances. These views led Berthollet into a protracted scientific debate with J. L. Proust. Proust said that chemical compounds were formed in fixed proportions by weight of their elements. Berthollet argued that the proportion by weight of the elements in a compound could vary according to the mass of the reactants from which the compound resulted. Proust's view seemed vindicated in the light of John Dalton's atomic theory, which depends on the law of fixed proportions. However, the outcome was that Berthollet's important insight into the role of reacting masses was neglected for more than 40 years.

Berthollet's country home at Arcueil, near Paris, became the center for a group of distinguished young chemists and physicists, to whom he offered the facilities of his private laboratory. This group organized themselves into the Society of Arcueil in 1807 under Berthollet's leadership. His last days were clouded by the suicide of his son in 1810 following the failure of a chemical factory in which he had a major interest. Berthollet died at Arcueil on Nov. 6, 1822.