Le Châtelier, Henry Louis

(b. Paris, France, 8 October 1850;d. Miribel-les-Échelles, Isère, France, 17 September 1936)

chemistry, metallurgy.

On his father’s side Le Châtelier came from a line of scientists and technologists, while his mother’s ancestors were artists, sculptors, architects, and geographers. His maternal grandfather, Pierre Durand, operated lime kilns and was a friend of Louis Vicat, a specialist in synthetic cements. Two of Le Châtelier’s uncles were engineers, one was and architect, and one a specialist in African affairs who helped to form French governmental policy in this field. His father Louis was inspector general of mines for France and the engineer responsible for building much of the French railway system. A strong republican, he resigned when Napoleon III became emperor and thereafter acted as advisor in the construction of railroads in Austria and Spain. He was associated with Deville in establishing and aluminum industry in France and with W. Siemens in building the first open-hearth steel furnace. The leading chemists of France frequently visited his home.

Thus young Le Châtelier grew up in and atmosphere in which science and technology met on equal terms. Even in his youth he was allowed to work for a time in Deville’s laboratory. He later said that his contacts with these friends of his father were important influences in shaping his career and establishing his reputation as a chemist. The other significant influence on his life was his mother, who raised her children according to a strict schedule and instilled in them a sense of order and discipline reinforced by the somewhat rigid training obtained in French technical schools. It is not surprising that due to their father’s activities all the children in the family were associated with scientific or technological employment throughout their lives or, in view of his mother’s strictness, that Henry remained a scientific and political conservative. All his life he was more interested in confirming natural laws than in overthrowing them.

Le Châtelier attended a military academy in Paris for a short time before enrolling at the Collège Rollin, from which he received his Litt.B. in 1867 and his B. S. in 1868. In 1869 he entered the École Polytechnique. Even in his student days he showed his originality and his feeling for the importance of and experimental rather than a theoretical approach to science. With some of his fellow students he designed a course in physics based entirely on the positivism of Comte and eliminating all abstract entities such as force.

His studies were interrupted by the Franco-Prussian War, in which he served as a lieutenant in the army. He resumed his academic work in 1871, enrolling in the École des Mines, as he planned to make a career in government administration. After graduation in 1873 he spent several years traveling, chiefly in North Africa in connection with a government plan to create and inland sea in that region. In 1875 he took up the duties of a mining engineer at Besançon. He married Geneviève Nicolas in 1876, and their seven children carried on the family traditions. The three sons became engineers, the four daughters married into the same profession.

In 1877 Le Châtelier’s career underwent a sharp change. Daubrée, the director of the École des Mines, did not know him personally, but he did know his father and had noted that the son had done well in chemistry while in the school. He therefore offered Le Châtelier the position of professor of general chemistry. He accepted the offer and remained at the institution until his retirement in 1919. At first lie taught only chemistry but later added metallurgy to his subjects. He received the degree of Doctor of Physical and Chemical Science in 1887, at which time his title was changed to professor of industrial chemistry and metallurgy. In the same year he accepted the chair of chemistry at the Collège de France and retained the post until 1908. In 1907 he succeeded Moissan as professor of general chemistry at the Sorbonne and held the chair until becoming and honorary professor in 1925. In this post he was able to direct the researches of graduate students. During his active years between 1908 and 1922 he directed the work of more than a hundred students, twenty-four of whom received their doctorates under his supervision. His lectures were very popular, and several were afterward published as books.

Le Châtelier was always interested in the organization of science, especially in relation to its industrial applications. In particular, he attended many international congresses devoted to industrial problems. During his life he held increasingly important positions on a large number of commissions and boards to advise the government on scientific and technical questions. Among these were the Commission on Explosives, the National Science Bureau, the Commission on Weights and Measures, the Commission on Standardization of Metallic Products, the Commission on Inventions, and the Committee for the Control of French Monetary Circulation. In 1916 President Wilson appointed him advisor in the establishment of the National Research Council in the United States.

In 1907 he was appointed inspector general of mines and became a member of the Académie des Sciences. He received medals and honors from almost every French scientific and engineering society and from numerous foreign countries including Poland, Russia, England, and United States, He also held honorary doctorates from the universities of Aix-la Chapelle (Aachen), Manchester., Louvain and Madrid and the Technical University of Denmark.

In his later years Le Châtelier devoted himself of writing on philosophical and social questions, and activity which he continued until his death at his country estate at the age of almost eighty-six.

The research activities of Le Châtelier were many and varied and at first glance it would seem that there was little relation between some of them. Yet, as is often the case with scientists, there was continuity, and it is possible to see how on line of study led to another.

When he first assumed and academic position he was somewhat at a loss as to what research he should undertake. His grandfather had made a collection of different types of hydraulic cements, and he decided and investigation of these might be profitable. For simplicity he began first to study the setting of plaster of Paris, which had originally been investigated by Lavoisier and Payen. They believed that during the burning of gypsum, anhydrous calcium sulfate was formed, and that in setting, the gypsum was immediately regenerated. In his first paper on the subject (1882) Le Châtelier found that the gypsum could be burned at a lower temperature than Payen had called for and that the product formed was not the anhydrous salt but a hemihydrate. In the setting process it formed a supersaturated solution around the particles of gypsum, from which new crystals of gypsum precipitated to form and interlocking mass. This work showed him the importance of compound formation in complex mixtures, and much of his subsequent work in various fields involved the detection of such compounds.

He next turned his attention to the problem of the setting of cements composed of calcium silicates. He found it better first to study barium other and metasilicates which he could easily synthesize in their pure form. The anhydrous forms of these salts, formed by fusion, set with water to form a barium metasilicate hexahydrate. The same changes occurred with the calcium silicates, in all cases giving rise to the essential setting compound, which was 3CaO·SiO₂. Other components of the cements merely acted as fluxes, Le Châtelier next studied a series of calcium aluminates. preparing the pure salts synthetically. These compounds also showed the phenomenon of setting, but the products were less stable than were the silicates. A mixture of silicates and aluminates hydrolyzed to form the stable compound and calcium hydroxide. As was the case with plaster of Paris, a supersaturated solution of calcium salts precipitated the stable component in the form of interlocking crystals. Le Châtelier determined the effect of changing the ratio of lime of magnesia to silica or alumina and determined hte conditions under which disintegration of the cement occurred. He also studied the the setting of cements under varied conditions in air, water, or seawater. He carried out analogous studies on ceramics and glass. Published in 1887 as his doctoral thesis, the work on cements has been called a classic of inorganic chemistry.

In all these studies he was guided equally by the intrinsic scientific interest of the reactions and their practical value to users of cements. He never recognized a distinction between pure and applied science, and many of his most fruitful ideas came from industrial problems.

In the course of his studies on the silicates he had to use very high temperatures, the measurement of which was difficult with instruments then available. Gas thermometers were inaccurate above 500°C. Platinum-iron and platinum-palladium thermocouples had been introduced, but Regnault, after careful study, had concluded that they gave widely varying results and should not be considered in any accurate work. Le Châtelier saw that the difficulty lay in the diffusion of one metal into the other at high temperatures and in lack of uniformity of the wires. After a series of studies he was able to show that a thermocouple consisting of platinum and a platinum-rhodium alloy gave accurate and reproducible results. He also introduced the custom of using the boiling points of naphthalene and sulfur and the melting points of antimony, silver, copper, gold, and palladium as standard fixed point in the calibration of his thermocouples. Since that time these thermocouples have been used successfully in all high-temperature work. He also made a number of studies of optical pyrometers which were useful in his day but have since been superseded by other methods.

A number of serious mine disasters led the French government in 1882 to ask the École des Mines to investigate their cause and prevention. In association with the professor of metallurgy, Mallard, Le Châtelier took up these problems. The two men first studied the temperature of ignition, speed of propagation of the flame, and conditions for explosion of mixtures of hydrogen, methane, and carbon monoxide with air. Later these same factors were investigated in other gases and gas mixtures. The study of the combustion of acetylene resulted in development of the oxyacetylene torch and its use in welding. In the course of their study they determined accurately for the first time the specific heats of a number of gases at high temperatures. Their results subsequently proved very useful in the study of combustion in industrial furnaces. During his investigations of mining problems Le Châtelier made a number of improvements in miner’s safety lamps and, together with Mallard, discovered several explosives that were safer than those in use at the time.

Le Châtelier then began to apply his earlier studies to events that occurred in the blast furnace. Industrialists had been puzzled by the reaction of iron oxides with carbon monoxide in the furnace. It was believed that the products should be iron and carbon dioxide. However, the gases emerging from the furnace still contained a considerable amount of carbon monoxide. Some industrialists believed that this was due to incomplete mixing of the reactants, but increasing the height of the furnace for better mixing did not help. Le Châtelier realized that the carbon monoxide formed carbon dioxide and carbon in a reversible reaction, for which the iron oxides acted as a catalyst.

His studies at high temperatures, both with the silicates and the combustion of gases, and the study of reactions in the blast furnace combined to interest Le Châtelier in the conditions needed for equilibrium in chemical reactions. His friend Deville had shown that in many reversible reactions dissociation occurred, and this emphasized the importance of studying equilibrium conditions. In his studies on the effect of temperature on such equilibria, van’t Hoff had concluded that all equilibria between two different states of matter (systems) are displaced by a lowering of the temperature toward that of the system whose formation develops heat.

Le Châtelier took up the study of these phenomena and in 1884 was able to announce the famous generalization that bears his name, the Le Châtelier principle: “Every system in stable chemical equilibrium submitted to the influence of and exterior force which tends to cause variation either in its temperature or its condensation (pressure, concentration, number of molecules in the unit of volume) in its totality or only in some one of its parts can undergo only those interior modification which, if they occur alone, would produce a change of temperature, or of condensation, of a sign contrary to that resulting from the exterior force.” He stated it more simply in his summary article in the Annales des mines of 1888: “Every change in one of the factors of and equilibrium occasions a rearrangement of the system in such a change in the sense opposite to the original change.” In this paper he illustrated his principle for a number of equilibria involving pressure, temperature, and electromotive force. As was usual with him, he applied the principle to practical studies, working out equilibrium conditions for gas furnaces and gaseous reactions.

Another result of his blast furnace studies was his investigation of the behavior of various gas mixtures. His student Boudouard worked out the conditions for the carbon monoxide reaction when catalyzed by iron oxide. Other gas mixtures were also tested. The most interesting results came from a study of the reaction of nitrogen and hydrogen in the presence of and iron catalyst in and attempt to synthesize ammonia. Le Châtelier worked out the theoretically correct conditions of temperature and pressure and the amount of catalyst needed as early as 1900. Unfortunately, when he tested his calculations in the laboratory, the gas mixture contained some air, and and explosion resulted. Unaware of the cause of this at the time, he abandoned the experiments, and it was left for Haber to accomplish the ammonia synthesis on a commercially practical scale after 1905.

Le Châtelier was greatly interested in thermodynamics. In the course of his work on equilibrium in reversible systems he discovered the work of J. W. Gibbs. He recognized that the highly abstract mathematical form of its presentation had prevented most chemists from understanding its chemical applications, and he did his best to spread knowledge of these in France. In spite of his efforts chemists did not accept it quickly, but he himself utilized it in the rest of his work. Some of his calculations anticipated the Nernst heat theorem. He applied his knowledge in this field to his studies of glasses and glazes, and investigated the properties of refractory materials and slags.

Le Châtelier’s association with Mallard introduced him to metallurgy, and although he hesitated at first to work in this field, feeling that he knew too little of it, he gradually began to introduce lectures on the subjects, as he did for the rest of his life. Therefore, after 1887 he assumed the title of professor of metallurgy in addition to his other titles at the École des Mines.

Mallard asked him to study allotropic modifications in certain minerals. Having decided that a good approach was to investigate the expansion of the minerals with increasing temperature, he designed and efficient dilatometer for this purpose, with it he demonstrated that quartz, instead of expanding evenly with temperature, showed a break in its expansion curve at definite temperatures. These corresponded to formation of different allotropic modifications. He then applied the idea of using physical methods for detecting chemical changes to the study of metals and especially of alloys. Most chemists at this time believed that alloys were simply indefinite mixtures of the component metals. Le Châtelier disproved this by studies at higher temperature than had previously been used, employing his dilatometer and using measurement of electrical conductivity and freezing point-composition diagrams. He was particularly successful in demonstrating the existence of intermetallic compounds by employing the latter method. In 1895 he pointed out that there were two parts to the study of alloys: determination of the chemical constitution, including formation of intermetallic compounds, solid solutions, and allotropic modifications; and the physical structure or arrangement of the several kinds of crystals in the alloys.

Much of his metallurgical work was concerned with the chemistry and metallurgy of iron ad steel. It had been believed that the hardness of quenched steel was due to the retention of a hard variety of iron stable at high temperatures and retained by rapid cooling. Le Châtelier’showed that the solid solution which was stable at high temperatures broke up upon cooling into two phases, iron and iron carbide. He pointed out that this process was analogous to crystallization of two phases from a liquid solution. Quenching prevented this separation. The hard form of iron was thus a solid solution of carbon in the lowtemperature allotropic form of iron the formation of which was not prevented during the rapid cooling. The data from Le Châtelier’s paper were later used by Roozeboom to construct the first equilibrium diagram for this series. This was the earliest application of the phase rule to a metallic system. through Roozeboom’s work the value of phase rule studies was finally recognized by industrial chemists.

Le Châtelier was always interested in the advancement of the science of metallurgy in France. Realizing the lack of a good textbook he arranged for the committee on alloys that he had organized to publish a volume, Contributionàl’études alliages, containing papers by leading French metallurgists. Several of Le Châtelier’s own contributions were included. For a long time it was the only really good textbook on metallurgy available in France. Le Châtelier was also aware that, while both England and Germany had special metallurgical journals, none existed in France. Therefore in 1904 he founded the Revue de métallurgie, which he edited until 1914. In the publication of this journal he was aided by his daughters, especially Genevieève, who died in 1923, the only one of his children who did not survive him.

One article printed in this journal concerned the high-speed steel tools developed in the United States by the industrial engineer F. W. Taylor. Thinking that they had been discovered accidentally, Le Châtelier entered into correspondence with Taylor and was relieved to discover that they were the result of a truly scientific study. He thus became aware of the work of Taylor, the father of scientific management, who stressed the application of scientific methods in the operation of factories and industrial concerns. Le Châtelier was greatly impressed by Taylor’s ideas and devoted much time in his later years to advocating the introduction of the Taylor system into French industry. His book Le Taylorisme, published in 1928, was devoted to and effort to increase the efficiency of French workmen. As part of the desired program he recommended a more liberal status for factory workers, and he became interested in political economy.

During World War I, Le châtelier served as advisor to the government on many military matters. He was influential in a metallurgical study of the heat treatment of shell cases. After the war he gradually withdrew from extensive laboratory work, although he continued to publish short notes on scientific subjects. His writings were always influential and clearly show his interest in the industrial applications of science. Thus Leçons sur le carbone, published from his lectures at the Sorbonne, opens with a discussion of the meaning of science and scientific laws. He then describes the various forms of carbon, leading up to a discussion of fuels ad metallic carbides. The industrial uses of these materials are described. A survey of oxides of carbon and the carbonates leads to a consideration of the laws of equilibrium, including a description of his own work. The book concludes with a section on atomic and molecular weights, although Le Châtelier avoids descriptions in atomic terms. Historical examples are given throughout.

After World War I Le Châtelier became increasingly concerned with sociological and philosophical questions. In his lectures he had always stressed the importance of general principles rather than merely listing chemical compounds and their properties. He was sometimes accused of teaching physics rather than chemistry. Nevertheless he could not accept theories that appeared to him to lack experimental foundation. As he had avoided the concept of force in physics during his student days, so in later life he avoided the use of atomic theory as much as possible. Since he worked almost entirely with inorganic compounds, he was not concerned with questions of structure, and so was able to consider atoms merely as useful pedagogic tools without deciding whether or not they actually existed.

After his retirement he spent much time in consideration of problems of intellectual and moral education. He stressed the importance of literature and Latin as part of general education and campaigned for restraint of political expenditures and better coordination of science and industry. Le Chaâtelier’s last paper, on which he was working at the time of his death, was entitled “Morals and Human Affairs.”

BIBLIOGRAPHY

I. Original Works. There is a complete bibliography in Revue de métallurgie,34 (1937), 145-160. A bibliography of Le Châtelier’s scientific work is inBulletin de la Sociélté chimique de France, 5th ser., 4 (1937), 1596-1611. The complete form of the Le Châtelier principle is given in “Recherches expérimentales et théoriques sur les équilibres chimiques,”in Annales des mines et des carburants, 8th ser., 13 (1888), 157-380. The studies on cements are described in the doctoral thesis Recherches expérimentales sur la constitution des mortiers hydrauliques (Paris, 1887).

II. Secondary Literature. The most complete survey of Le Châtelier’s life and work is the Jan. 1937 special issue, “À la mémoire de Henry Le Châtelier 1850-1936,”of Revue de métallurgie,34 (1937), 1-160. Full biographies with emphasis on the scientific work are C. H. Desch, “The Le Châtelier Memorial Lecture,”in Journal of the Chemical Society (1938), 139-150; and P. Pascal, “Notice sur la vie et les travaux de Henry Le Châtelier,”in Bulletin de la Société chimique de France, 5the ser., 4 (1937), 1557– 1596. A shorter and more personal biography is R. E. Oesper, “The Scientific Career of Henry Louis Le Châtelier,”in Journal of Chemical Education,8 (1931), 442-461.

Henry M. Leichester