Henry Louis Le Chatelier (French pronunciation: [ɑ̃ʁi lwi lə ʃɑtəlje]; 8 October 1850 – 17 September 1936) was a French chemist of the late 19th and early 20th centuries. He devised Le Chatelier's principle, used by chemists to predict the effect a changing condition has on a system in chemical equilibrium.
Le Chatelier was born on 8 October 1850 in Paris and was the son of French materials engineer Louis Le Chatelier and Louise Durand. His father was an influential figure who played important roles in the birth of the French aluminium industry, the introduction of the Martin-Siemens processes into the iron and steel industries, and the rise of railway transportation. Le Chatelier's father profoundly influenced his son's future. Henry Louis had one sister, Marie, and four brothers, Louis (1853–1928), Alfred (1855–1929), George (1857–1935), and André (1861–1929). His mother raised the children by regimen, described by Henry Louis: "I was accustomed to a very strict discipline: it was necessary to wake up on time, to prepare for your duties and lessons, to eat everything on your plate, etc. All my life I maintained respect for order and law. Order is one of the most perfect forms of civilization."
As a child, Le Chatelier attended the Collège Rollin in Paris. At the age of 19, after only one year of instruction in specialized engineering, he followed in his father's footsteps by enrolling in the École Polytechnique on 25 October 1869. Like all the pupils of the Polytechnique, in September 1870, Le Chatelier was named second lieutenant and later took part in the Siege of Paris. After brilliant successes in his technical schooling, he entered the École des Mines in Paris in 1871.
Le Chatelier married Geneviève Nicolas, a friend of the family and sister of four fellow students of the Polytechnique. They had seven children, four girls and three boys, five of whom entered scientific fields; two died preceding Le Chatelier's death.
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 again 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 replaced Henri Moissan.
At the Collège de France, Le Chatelier taught:
Phenomena of combustion (1898)
Theory of chemical equilibria, high temperature measurements and phenomena of dissociation (1898–1899)
Properties of metal alloys (1899–1900)
General methods of analytical chemistry (1901–1902)
General laws of analytical chemistry (1901–1902)
General laws of chemical mechanics (1903)
Silica and its compounds (1905–1906)
Some practical applications of the fundamental principles of chemistry (1906–1907)
Properties of metals and some alloys (1907)
After four unsuccessful campaigns (1884, 1897, 1898 and 1900), Le Chatelier was elected to the Académie des sciences (Academy of Science) in 1907. He was also elected to the Royal Swedish Academy of Sciences in 1907. In 1924, he became an Honorary Member of the Polish Chemical Society.
In chemistry, Le Chatelier is best known for his work on his principle of chemical equilibrium, Le Chatelier's principle, and on varying solubility of salts in an ideal solution. He published no fewer than thirty papers on these topics between 1884 and 1914. His results on chemical equilibrium were presented in 1884 at the Académie des sciences in Paris.