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Born Sept. 20, 1842, in Kincardine-on-Forth, Scotland; died Mar. 27, 1923, in London. British physicist and chemist. Member of the Royal Society of London (1877).
Dewar graduated from the University of Edinburgh in 1861. He was a professor at Cambridge University (from 1875) and at the Royal Institution in London (from 1877). He was also president of the Chemical Society of England (1897). Dewar studied carbonyl compounds and ozone. In 1871 he proposed structural formulas for benzene and pyridine. His principal works dealt with the study of thermal phenomena. In 1872 he worked out methods of measuring specific heat at low temperatures and discovered that it decreases with decreasing temperature. In 1898 he obtained liquid hydrogen for the first time and determined its constants. Dewar invented a vessel in which bodies can retain their temperatures for long periods of time. He investigated the change in the electrical conductivity of metals as a function of temperature. In collaboration with P. Curie he experimentally proved (1904) that helium is formed during the radioactive decay of radon.