BERTHOLLET, bilettla', Count CLArDE Louis (1748-1822). A distinguished French theoretical chemist. He was born at Talloire, a village of Savoy, near Annecy. He studied at the University of Turin, and obtained a medical degree there in 1768. He afterwards went to Paris, where he was appointed physician to the Duke of Orleans. He now applied himself with great assiduity to chemistry; in 1780 he was elected a member of the Academy of Sciences, and, some time after, the Government made him superintendent of dyeing processes. In this situa tion he published a very valuable work on dye ing. In 1785 he announced his adherence to the antiphheristic doctrines of Lavoisier, though he did not admit oxygen to be the acidifying princi ple, and herein he has proved to be right. In the same year lie published a paper on "dephlogisti cated marine acid"—no• called chlorine—point ing out its use for bleaching purposes; and fol lowing up the experiments of Priestley, he showed ammonia to be a compound of three volumes of hydrogen gas and one volume of nitrogen. Dur ing the early part of the French Revolution Berthollet traveled through the country, giving instruction as to the best means of extracting and purifying saltpeter to lie used in the manu facture of gunpowder, and also as to the process of smelting and converting iron into steel. In 1794 he became professor at the Ecole Nor male. His joining the expedition of Napo leon to Egypt led to the formation of the Institute of Cairo. On his return from Egypt Ile was made a senator by Bonaparte, who also conferred on him several marks of honor, and made him a count. Notwithstanding, he voted for the deposition of Napoleon in 1814. On the restoration of the Bourbons, he was made a peer; but in spite of all these honors he remained simple, modest. and unassuming. In collabora tion with Lavoisier and others, he devised the system of chemical nomenclature which is still, in its main features, employed. Berthollet was
the first to introduce the idea of equilibrium into chemical philosophy. Since the time of Bergman, it had been believed that the only fac tor determining the course of a reaction is the mutual chemical affinity of the reacting sub stances. Thus, when common salt (sodium chloride) is acted on by sulphuric acid, the latter takes up the sodium of the former and hydro chloric acid is set free. According to Bergman's teaching, the cause of this phenomenon lies in the fact that sodium has a stronger affinity for sul phuric than for hydrochloric acid. Berthollet, however, advanced the view that besides chemical affinity, there is another important factor upon which the course of a chemical reaction depends: viz. the relative masses of the reacting sub stances and of the products of the reaction. If hydrochloric acid, which is a gas, was not allowed to escape during the reaction and a certain mass of it would remain in the reacting mixture, then only part. of it would be driven out of combination with sodium, so that when the re action would reach the state of equilibrium, the mixture would contain, on the one hand, both sulphuric and hydrochloric acids in the free state, and, on the other hand, both the sulphate and the chloride of sodium. The development and application of Berthollet's idea form one of the most important chapters of theoretical chem istry and have thrown much light on chemical combination. Berthollet's principal work, Essai de statique ehimique, in two volumes, appeared in Paris in 1803. Consult: Curvier, Elope de Cla"le Louis Berthollet (Paris, 1820) ; and Mul ler, Berthollet's Leben (Erlangen, 1828).