Henri Le Châtelier was a French chemist who is most famous for devising Le Chatelier's principle in 1884, used by chemists to predict the effect of a change in conditions on a chemical equilibrium. The principle states that if an external change is imposed on a system in reactive equilibrium, the system will establish a new equilibrium, which counteracts the external change. Le Châtelier's principle was fully explained in an 1888 paper. This fundamental contribution to chemical thermodynamics had been anticipated in part by J. W. Gibbs, whose work Le Châtelier translated into French, helping Gibbs' ideas reach a broader audience. Le Châtelier also suggested the use of a thermocouple to measure high temperatures, and invented the optical pyrometer, a thermometer that uses infrared radiation to determine an object’s temperature by measuring the wavelength of the radiation emitted. He is also known for is work on the variation of the solubility of salts in an ideal solution.

Despite training as an engineer, and even with his interests in industrial problems, Le Chatelier chose to teach chemistry rather than pursue a career in industry. In 1887, he was appointed head of the general chemistry to the preparatory course of the École des Mines in Paris. He tried unsuccessfully to get a position teaching chemistry at the École polytechnique in 1884 and in 1897. At the Collège de France, Le Chatelier succeeded Schützenberger as chair of inorganic chemistry. Later he taught at the Sorbonne university, where he succeeded Henri Moissan. After four unsuccessful efforts (1884, 1897, 1898 and 1900), Le Chatelier was elected to the Académie des sciences (Academy of Science) in 1907.

Sources

• Cleveland, Cutler (Lead Author); Peter Saundry (Topic Editor). 2008. "Le Châtelier, Henri." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth September 15, 2006; Last revised August 21, 2008; Retrieved March 8, 2009].
• Wikipedia Contributors, Henri Le Châtelier , Wikipedia The Free Encyclopedia, Accessed 8 March 2009.