Comte Claude Louis Berthollet (1748-1822), French chemist. Berthollet was born near Annency in southern France. Originally a physician, he moved to chemistry and became an early supporter of Lavoisier's ideas. He was the first to determine the composition of ammonia and studied the sulphides of hydrogen, hydrogen cyanide, cyanogen chloride and the reactions of chlorine. He deduced that some acids do not contain oxygen. He discovered potassium chlorate, but his use of it in gunpowder destroyed a powder mill in 1788. His work on bleaching fabrics with chlorine, and on dyes and steel-making, was more successful. With Lavoisier he devised a system of chemical nomenclature that is the basis of the modern naming system of compounds. Berthollet was a friend of Napoleon, visiting Egypt during Napoleon's military campaign, but in 1814 he helped depose the Emperor 'for the good of France'.