Le Chatelier, Henri Louis

[luh shatlyay] (1850–1936) French physical chemist and metallurgist: devised a much-used but doubtful principle.

As a young man, Le Chatelier was much influenced by his father Louis, an engineer who was Inspector General of Mines for France. Tuition from his father and family friends such as aided him and shaped his interests, and he became a professor in the École des Mines in 1877. His early research was on cement (his grandfather operated lime kilns); he worked also on the structure of alloys, on flames and on thermometry. In the 1880s he developed the idea known as Le Chatelier’s principle: this states that if the conditions (temperature, pressure, or volume) of a chemical system initially at equilibrium are changed, then the equilibrium will shift in the direction that will tend to annul the change, if possible. The principle has been much criticized, and it is best replaced by two laws due to ; they are (1) increase in pressure favours the system having the smaller volume, and (2) rise in temperature favours the system formed with absorption of heat. Thus for the equilibrium in which the volume diminishes when the reaction proceeds to the right, an increase of pressure will shift the equilibrium in favour of ammonia formation. Also, as ammonia formation is exothermic, rise in temperature favours the reactants.