CLAUDE LOUIS, one of the most distinguished chemists of the French school, was not a native of France, but born at Talloire, near Annecy, in Savoy, in 1748. He received his education first at Chambery, and subsequently in the provincial college at Turin, where he took his degree as a physician. On arriving at Paris, he soon became the medical attendant of Philip Duke of Orleans; and by the publication of a volume of chemical essays, which gained him such reputation that he was admitted, in 1781, into the Académie des Sciences. Through the interest of his royal patron he was appointed government superintendent of the establishment for the improvement of dyeing; and the result was the production of his very valuable essay Sur la Teinture, a work that first systematized and chemically explained the principles of the art of dyeing. This work has been well translated into English by Dr Wm. Hamilton, in two vols., 1791.

Berthollet early adopted the chemical views of Lavoisier, which he illustrated with great ingenuity, and contrasted with the phlogistic hypothesis of Stahl; and to the two former, assisted by Moreveau and Fourcroy, we owe that beautiful system of chemical nomenclature to which subsequent philosophers have been so much indebted. Berthollet confirmed and extended the discoveries of Priestley on ammonia; discovered, among other curious substances, fulminating silver; and greatly extended our knowledge of that important substance the dephlogisticated marine acid of Scheele, for which the name of oxyuriatric acid was then proposed, and which is now termed chlorine. It was he who first proposed to apply it to bleaching—in 1785. During these researches he discovered the remarkable salt now called chlorate of potassa; and we owe to him also an excellent essay on the chemical constitution of soaps. But we cannot here attempt an enumeration of all the contributions to chemistry by this estimable philosopher: they are scattered through between eighty and ninety memoirs in the Journal de Physique, Annales de Chimie, Memoires de l'Institut, and Memoires d'Arceuil, from which they have been copied into all the philosophical journals of Europe.

At the commencement of the French Revolution the scarcity of saltpetre for the manufacture of gunpowder was much felt; and Berthollet was placed at the head of a commission for improving the processes for obtaining this important product within the territory of France. In this vocation he visited almost all France, and greatly improved and simplified the modes of obtaining and purifying saltpetre. Soon afterwards we find him one of a commission for improving the processes in the smelting of iron, and converting it into steel. The government fully appreciated his merits; and in 1792 he was appointed a director of the mint, in which he introduced several important improvements. In 1794 he was an active member of the committee on agriculture and the arts; while he filled the office of teacher of chemistry in the Polytechnic and Norman Schools of Paris, and was an active member in the remodelling of the National Institute in 1795.

When the victories of Buonaparte prostrated Italy, Berthollet and Monge were appointed by the convention as the heads of a commission to select from the spoils of Italy the choicest specimens of ancient and modern art, for the national galleries of Paris. This circumstance introduced Berthollet to the victorious general; and, in after years, led to his accompanying Buonaparte in the expedition to Egypt, where he was one of the most distinguished members of the Institute of Cairo. On the overthrow of the executive directory, Berthollet was made a senator, and a grand officer of the Legion of Honour. Under the empire he was created a count, and sat as a peer on the restoration of the Bourbons.

His last work was his curious essay on Chemical Statistics, in which he endeavoured to show that other causes than the mere force of elective attractions, as explained by Bergman, aided in producing chemical combinations; and he particularly showed how certain decompositions could be explained without the supposition of what was termed predisposing affinities, by the influence of insolubility, of aggregation, and of the mass of one of the ingredients. This ingenious theory was never generally adopted by chemists, the theory of definite proportions, and of opposite electric states, being supposed sufficient to explain chemical phenomena.

Berthollet was a man of great modesty and unostentatious manners. For some years he lived rather retired at Arceuil, especially after his grief for the misconduct and suicide of his only son. In 1822 he was attacked with a painful and lingering malady, which he bore with manly fortitude, and which ended in an enormous gangrene that put a period to his sufferings on the 6th of November of that year. (r. s. t.)