Henry Louis Le Châtelier

Henry Louis Le Chatelier (French pronunciation: ​[ɑ̃ʁi lwi lə ʃɑtlje]; 8 October 1850 – 17 September 1936) was an influential French chemist of the late 19th and early 20th centuries. He is most famous for devising Le Chatelier's principle, with the help of his partner Jasper Rossi, 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:

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 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 1885 at the Académie des sciences in Paris.

Le Chatelier also carried out extensive research on metallurgy and was one of the founders of the technical newspaper La revue de métallurgie (Metallurgy Review).

Part of Le Chatelier's work was devoted to industry. For example, he was a consulting engineer for a cement company, the Société des chaux et ciments Pavin de Lafarge, today known as Lafarge Cement. His 1887 doctoral thesis was dedicated to the subject of mortars: Recherches expérimentales sur la constitution des mortiers hydrauliques (Experimental Research on the Composition of Hydraulic Mortars).

Le Chatelier in 1901 attempted the direct combination of the two gases nitrogen and hydrogen at a pressure of 200 atm and 600 °C in presence of metallic iron. The mixture of gases was forced by an air compressor into a steel Berthelot bomb, where they and the reduced iron catalyst were heated by a platinum spiral. A terrific explosion occurred which nearly killed an assistant. Le Chatelier found that the explosion was due to the presence of air in the apparatus used. And thus it was left for Haber to succeed where several noted French chemists, including Thenard, Sainte Claire Deville and even Berthelot had failed. Less than five years later, Haber and Claude were successful in producing ammonia on a commercial scale, acknowledging that the account of Le Chatelier's failed attempt had accelerated their research. Near the end of his life, Le Chatelier wrote, "I let the discovery of the ammonia synthesis slip through my hands. It was the greatest blunder of my scientific career”.

Le Chatelier's principle

Le Chatelier's Principle states that a system always acts to oppose changes in chemical equilibrium; to restore equilibrium, the system will favor a chemical pathway to reduce or eliminate the disturbance so as to restabilize at thermodynamic equilibrium. Put another way,

If a chemical system at equilibrium experiences a change in concentration, temperature or total pressure, the equilibrium will shift in order to minimize that change.

This qualitative law enables one to envision the displacement of equilibrium of a chemical reaction.

For example: a change in concentration of a reaction in equilibrium for the following equation:

If one increases the pressure of the reactants, the reaction will tend to move towards the products to decrease the pressure of the reaction.

However consider another example: in the contact process for the production of sulfuric acid, the second stage is a reversible reaction:

The forward reaction is exothermic and the reverse reaction is endothermic. Viewed by Le Chatelier's principle a larger amount of thermal energy in the system would favor the endothermic reverse reaction, as this would absorb the increased energy; in other words the equilibrium would shift to the reactants in order to remove the stress of added heat. For similar reasons, lower temperatures would favor the exothermic forward reaction, and produce more products. This works in this case, since due to loss of entropy the reaction becomes less exothermic as temperature increases; however reactions that become more exothermic as temperature increases would seem to violate this principle.

It was typical for scientists and engineers of the time to have a very scientific vision of industry. In the first issue of La revue de métallurgie, Le Chatelier published an article describing his convictions on the subject, discussing the scientific management theory of Frederick Winslow Taylor. In 1928, he published a book on Taylorism.

Le Chatelier was politically conservative. In 1934, he published an opinion on the French forty-hour work week law in the Brussels publication Revue économique internationale. However, in spite of certain anti-parliamentarian convictions, he kept away from any extremist or radical movements.

Decorations

Le Chatelier was named "chevalier" (knight) of the Légion d'honneur in 1887, became "officier" (officer) in 1908, "commandeur" (Knight Commander) in 1919, and was finally awarded the title of "grand officier" (Knight Grand Officer) in May 1927.

• Cours de chimie industrielle (1896; second edition, 1902)
• High Temperature Measurements, translated by G. K. Burgess (1901; second edition, 1902)
• Recherches expérimentales sur la constitution des mortiers hydrauliques (1904; English translation, 1905)
• Leçons sur le carbone (1908)
• Introduction à l'étude de la métallurge (1912)
• La silice et les silicates (1914)