Dixon, Harold Baily

(b. London, England, 11 August 1852; d. Lytham, England, 18 September 1930)

chemistry.

Dixon was a leading authority on gaseous explosions and created an international interest in combustion research. The son of William Hepworth Dixon, author of popular historical and travel books and editor of Athenaeum, Dixon intended to follow a literary career. He did poorly as a classical student at Oxford (1871–1875), however, and transferred to chemistry. He worked with A. V. Harcourt until 1879 and was a lecturer at Trinity and Balliol colleges. In 1886 he assumed the chair of chemistry at Owens College, Manchester, where he founded the Manchester School of Combustion Research. He was elected to the Royal Society in 1886 and was a president of the Chemical Society of London and the Manchester Literary and Philosophical Society.

The only detailed studies of gaseous explosions had been made by Bunsen, and for twenty years his results were accepted as authoritative. Bunsen claimed that his experiments were inconsistent with Berthollet’s law of mass action. In his first researches at Oxford, Dixon found Bunsen’s conclusions to be erroneous and that the law of mass action applied to gaseous explosions. In 1880 he discovered the incombustibility of purified and dried gases, proving that prolonged drying of gas mixtures rendered them nonexplosive to electric sparks, whereas wet mixtures exploded readily. His publications began the systematic investigation of the effect of moisture on chemical changes.

Dixon’s major contribution to combustion research was his detailed study of the rate and propagation of explosions. On the basis of Bunsen’s experiments, scientists believed the rates of gaseous explosions were only a few meters per second; but Dixon proved that very great flame speeds were attained and that Bunsen’s speeds applied only to the usually short initial phase of explosions. Dixon determined the velocity and course of explosions, developing his own photographic methods to detect the moving flame. He named the rapid motion of flame “the detonation wave.” Another line of combustion research was his measurement of the ignition temperatures of gases and gas mixtures. He was the first to determine these with accuracy.

BIBLIOGRAPHY

Dixon wrote three long papers that serve as detailed monographs on the subjects of flame and explosions: “Conditions of Chemical Change in Gases: Hydrogen, Carbonic Oxide, and Oxygen,” in Philosophical Transactions of the Royal Society, 175 (1884), 617–684; “The Rate of Explosions in Gases,” ibid, 184A (1893), 97–188; and “On the Movements of the Flame in the Explosion of Gases,” ibid, 200A (1903), 315–352.

Dixon’s life and work are chronicled by his students H. B. Baker and W. A. Bone in “Harold Baily Dixon 1852– 1930,” in Journal of the Chemical Society (1931), 3349–3368. The same essay appears in Proceedings of the Royal Society, 134A (1931–1932), i–xvii; and in Alexander Findlay and William Hobson Mills, eds., British Chemists (London, 1947), pp. 126–145.

Albert B. Costa