BERTHOLLET, CLAUDE-LOUIS, COMTE

(Count) born Dec. 9, 1748, Talloires, near Annecy, France died Nov. 6, 1822, Arcueil French chemist who was the first to note that the completeness of chemical reactions depends in part upon the masses of the reacting substances; he thus came close to formulating the law of mass action. Though he incorrectly concluded that elements unite in all proportions, his resulting controversy with the chemist Joseph-Louis Proust led to the establishment of the law of definite proportions. Educated in medicine at Turin, Italy, Berthollet later became associated with Antoine Lavoisier, whom he assisted in reforming chemical nomenclature. His researches with hydrocyanic (prussic) acid and hydrogen sulfide led him to disagree with Lavoisier's contention that oxygen was an essential element in all acids. Berthollet discovered the composition of ammonia (1785) and introduced chlorine as a bleaching agent. During the French Revolution he served on many scientific committees and became a commissioner of the national mint (1792). Appointed commissioner of agriculture and professor at the polytechnic and normal schools (1794), he helped reorganize the academy as the Institut National (1795) and in 1796 headed a commission sent to Italy to select choice ancient and modern artworks for the national galleries of Paris. He accompanied Napoleon on his expedition to Egypt (1798), where he helped to form an institute modelled on the Institut National and first presented his ideas on chemical equilibria in his book Essai de statique chimique (1803). During the Napoleonic Wars he determined how to obtain iron from ore and convert it into steel. Though his preparation of potassium chlorate did not provide the substitute for saltpetre in gunpowder that he had intended, it did make possible the manufacture of coloured fireworks. Berthollet was also a senator and a grand officer of the Legion of Honour and became a count under the French empire. In retirement he maintained a laboratory and sponsored meetings of distinguished scientists, whose discussions were published between 1807 and 1817.