DEWAR, SIR JAMES British chemist and physicist, was born at Kincardine-on-Forth, Scotland, on Sept. 20, 1842. He was very fond of music as a child, and when he met with an accident which prevented him from playing the flute he practised making fiddles, and so acquired a manual dexterity which served him in good stead in later years. He was educated at Dollar academy and Edinburgh university, being first a pupil, and afterwards the assistant, of Lyon Playfair, then professor of chemistry; he also studied under Kekule at Ghent. In 1875 he was elected Jacksonian professor of natural experimental philos ophy at Cambridge, and in 1877 he succeeded J. H. Gladstone as Fullerian professor of chemistry in the Royal Institution, London. He was president of the Chemical Society in 1897, and of the British Association in 1902, served on the Balfour commission on London water supply , and as a member of the committee on explosives (1888-91) invented cordite jointly with Sir Frederick Abel. He was awarded the Rumford medal of the Royal Society in 1894; and the Smithsonian institution, the French Academy of Sciences, the Italian Society of Sciences and the Royal Society of Arts honoured his work. He was knighted in 1904, and died on March 27, 1923.
Dewar's scientific work covers a wide field. His earlier papers deal with organic chemistry, with measurement of high tempera tures, with electro-photometry and the chemistry of the electric arc. With J. G. M'Kendrick, of Glasgow, he investigated the physiological action of light, and examined the changes which take place in the electrical condition of the retina under its influence. With G. D. Liveing, of Cambridge, he began in 1878 a long series of spectroscopic observations, the results of which were published in 1915 as Collected Papers in Spectroscopy. With J. A. Fleming, of University college, London, he investigated the specific induc tive capacity of substances at very low temperatures. Dewar is best known for his work on the liquefaction of the so-called per manent gases (see LIQUEFACTION OF GASES), and his researches at temperatures approaching the absolute zero. His interest in this branch of inquiry dates back at least as far as 1874, when he discussed the "Latent Heat of Liquid Gases" before the British Association. Subsequently he was stimulated by the work of L. P. Cailletet and R. P. Pictet in 1877, and of Z. F. Wroblewski and K. S. Olszewski a few years later; and by 1891 Dewar had con structed a machine for producing liquid oxygen in quantity. He made use of this liquid for some low temperature experiments on meteorites, and in 1891 showed that both liquid oxygen and ozone are magnetic. About 1892 the idea occurred to him of using vacuum-jacketed vessels for the storage of liquid gases, and so efficient did this device prove in preventing the influx of external heat that it was found possible to preserve the liquids for com paratively long periods ; this apparatus which he designed is known as the "Dewar flask," and is invaluable for low temperature work. The principle has been used extensively in the common "thermos" or vacuum flask. He next experimented with a high-pressure hydrogen jet by which low temperatures were realized through the Joule-Thomson effect (see THERMODYNAMICS), and the success ful results thus obtained led him to build at the Royal Institution the large refrigerating machine by which hydrogen was first liquefied in 1898 and solidified in 1899. He investigated the gas absorbing powers of charcoal cooled to low temperatures, and ap plied them to the production of high vacua and to gas analysis.
With collaborators he also studied the physical and chemical properties of iron and nickel carbonyls, the properties of thin films, and atomic heats at low temperatures. Dewar had a fine directing power and was able to do excellent work with competent assist ants. His greatest strength was probably in his manipulative skill, and his lectures at the Royal Institution were always remarkable for the experimental demonstrations which accompanied them. See Royal Institution Lecture H. E. Armstrong, Jan. 1924.
