A French chemist and physicist noted for his study of gases at different pressures. He discovered that acetylene is very soluble in acetone and gave rise to a method for storing the gas. His research on rare gases obtained by the liquefaction of air was developed into the invention of neon signs. Two processes are known by his name: the Claude process for liquefying gases by a series of processes including cooling by expansion while performing work against a piston; and the Claude process for the manufacture of ammonia.