TAYLOR, HUGH STOTT

(b. St. Helens, Lancashire, England, 6 February 1890; d. Princeton, New Jersey, 17 April 1974)

physical chemistry.

Hugh Stott Taylor was the third of the eight children of James and Ellen Stott Taylor. His father was a glass technologist and his mother a school-teacher. Like his parents, Taylor was a devout Roman Catholic. After school in St. Helens, Taylor attended Liverpool University (1906–1912), where he received the B.Sc. (1909), the M.Sc. (1910), and, on the evidence of published researches, the D.Sc. (1914). Acting on the advice of F. G. Donnan, professor of physical chemistry at Liverpool, Taylor went to study with Svante Arrhentus at Stockholm (1912–1913) and then with Max Bodenstein at Hannover (1913–1914). He was appointed instructor in chemistry at Princeton University in 1914, partly on the recommendation of James Kendall, a fellow Stockholm student. Taylor remained at Princeton for the rest of his life. In 1919 he married Elizabeth Sawyer from Southport, England. They had two daughters.

His academic advancement was rapid. Taylor became associate professor (1921), full professor (1922), chairman of the chemistry department (1926–1951), and dean of the graduate school (1945–1958). In 1953 he was knighted (K.B.E.). Finally, Taylor became the first president of the Woodrow Wilson National Fellowship Foundation (1958–1969).

Taylor was an industrious, well-organized chemist whose judgment was both well respected and sought after. He wrote over three hundred scientific papers and articles and undertook valuable editorial work. His research began in inorganic chemistry and phase equilibria under Donnan’s pupil, Henry Bassett, Jr., at Liverpool. At Stockholm, under Arrhenius, he examined the influence of neutral salts on the acid-catalyzed hydrolysis of esters. The catalytic activity of hydrochloric acid was increased when he added potassium chloride. From his results Taylor derived a relationship between the catalytic constant and the acid-dissociation constant that to some extent anticipated the Brönsted-Pederson equation for general acid catalysis.

In Bodenstein’s laboratory Taylor gained important experience in high-vacuum techniques through an investigation of the effect of alpha particles on a mixture of hydrogen and chlorine gases. Large numbers of hydrogen chloride molecules were produced for each ion pair formed. His results were comparable with those obtained in 1913 by Bodenstein and Dux from the same reaction with photochemical initiation. Bodenstein originally interpreted this reaction as an ionic chain sequence. In 1918 H. W. Nernst suggested that it was an atomic chain sequence, a view that is now generally accepted.

At Princeton. Taylor was encouraged by his professor. G. A. Hulett, to determine thermochemical data and to test the Nernst heat theorem using electrical cells. His major studies, however, were devoted to gas adsorption and heterogeneous catalysis. Taylor’s research during World War I may have stimulated his interest in catalysis. In 1917 he rejoined Donnan for two years at University College, London. Working with E. K. Rideal Taylor manufactured synthesis gas (CO₂ and H₂) in order to prepare hydrogen for ammonia synthesis. This was achieved by the water-gas shift reaction CO + H₂O ⇄ CO₂ + H₂, for which they developed a coprecipitated iron oxide/chromium oxide catalyst.

In the 1920’s Taylor and his co-workers at Princeton investigated the adsorption of gases on metals in order to elucidate the action of catalysts. The specific nature of adsorption was revealed by measurements of the heat of adsorption of hydrogen on both nickel and copper. Adsorption depended on both the gas and the metal used in experiments. It was not a simple liquefaction process. Catalysts were also revealed to be quite specific in their action. They were markedly sensitive to heat treatment, sintering, and poisons. In a notable paper of 1925, Taylor emphasized that catalyst surfaces were heterogeneous and that only a fraction of the surface available for gas adsorption might be active. The catalytic action was connected with exposed atoms on the corners, edges, or surfaces of metal crystals. He called these sites “active centers.” In an extension of Irving Langmuir’s views on adsorption, Taylor suggested that several gas molecules might be adsorbed on one site, and there they might react with one another.

Further insight into the mechanism of heterogeneous catalysis came in 1930 and 1931; Taylor suggested that adsorption of gases by solids might be a very slow process. He distinguished between two kinds of adsorption of diatomic gas molecules. First, there was weak but rapid molecular adsorption involving van der Waals forces. This was physical adsorption. Second, there was a stronger dissociative adsorption that produced gaseous atoms on the catalyst surface. This was chemisorption, and it required a certain activation energy comparable with that of chemical reactions. He emphasized that activated adsorption was fundamental to any understanding of the mechanism of heterogeneous catalysis. In 1931 Taylor and A. T. Williamson obtained evidence for different kinds of activated adsorption of hydrogen on manganous oxide/chromic oxide surfaces. Taylor found further support for activated adsorption in the 1930’s by isotope-exchange reactions with hydrogen and deuterium.

During the same period Taylor continued to investigate homogeneous gas reactions and photochemistry. By using photosensitization to excite mercury atoms, Taylor and A. L. Marshall dissociated hydrogen molecules into atoms and examined their reactions. In 1925 Taylor showed that ethylene reacted rapidly with a hydrogen atom to give an ethyl radical: C₂H₄ + H → C₂H₅. This ethyl radical then reacted with a hydrogen molecule to make both the product ethane and a hydrogen atom to repeat the whole process: C₂H₅ + H₂ → C₂H₆ + H. This was one of the earliest examples of organic free radicals acting as chain carriers in chemical reactions. Taylor and Marshall also demonstrated free radical chain reactions between hydrogen and carbon monoxide to produce formaldehyde, and in 1926Taylor and J. R. Bates converted ethylene into liquid polyethylene, a forerunner of industrial polyethylene production. A commercially useful reaction studied by Taylor and J. Turkevich in 1935 was the dehydrogenation and ring closure of heptane to make toluene, using a chromium oxide gel catalyst.

In the 1930’s Taylor was one of the first chemists to produce heavy water on a reasonable scale. This experience was valuable in 1941 and 1942, when he worked on the large-scale production of water for the Manhattan Project. From 1943 to 1945 he again assisted with the project by statistically testing new nickel barriers for the separation of uranium 235 from uranium 238 by fractional diffusion of uranium hexafluoride.

BIBLIOGRAPHY

I. Original Works. Catalysis in Theory and Practice (London, 1919; 2nd ed.. London and New York, 1926), written with E. K. Rideal; Fuel Production and Utilization (London and New York, 1920); Industrial Hydrogen (New York, 1921; 2nd ed., New York, 1931); A Treatise on Physical Chemistry (editor and contributor), 2 vols. (New York, 1924; 3rd ed., edited with S. Glasstone, 1942–1951); “Photosensitization and the Mechanism of Chemical Reactions,” in Transactions of the Faraday Society, 21 (1925), 560–568; Elementary Physical Chemistry (New York, 1927; 3rd ed., written with H. A. Taylor, New York, 1942); “Fundamental Science from Phlogiston to Cyclotron,” in Molecular Films. Cyclotron and the New Biology (New Brunswick, N.J., 1942, repr. 1946), written with Irving Langmuir and Ernest O. Lawrence; Physical Measurements in Gas Dynamics and Combustion, ed. with B. Lewis and R. N. Pease (Princeton, 1954); Science in Progress, editor of the 10th and 11th series (New Haven, 1957–1960).

II. Secondary Literature. C. M. Kemball, “Hugh Stott Taylor,” in Biographical Memoirs of Fellows of the Royal Society, 21 (1975), 517–547, includes a complete bibliography. Obituaries appeared in Nature, 251 (1974), 266; and Chemistry in Britain, 11 (1975), 370–371.

Michael Stanley