Claude-Louis Berthollet (1748-1822), French doctor and chemist. Berthollet graduated in medicine, but by 1780 his work in the new science of chemistry led to his admission to the French Academy of Sciences. Berthollet supported the theories of Lavoisier, but correctly disagreed with him by proposing that some acids do not contain oxygen. His book Essai de statique chimique (1803) was the first systematic work on chemical physics. He also worked on a wide range of chemicals, as well as dyes and gunpowder. Berthollet was a friend of Napoleon Bonaparte and was made a count (Comte Berthollet), but in 1814 he helped depose Napoleon as Emperor, 'for the good of France'. 19th-century engraving.