WILLIAMSON, ALEXANDER WILLIAM (1824 5904), English chemist, was born at Wandsworth, London, on May 1, 1824. He first studied medicine, but whilst at Heidelberg he became interested in L. Gmelin's work, and decided to take up chemistry; in 1844 he went to Giessen and worked under Liebig and Bischoff. In 1849 he was appointed professor of practical chemistry at University college, London, and from 1855, when Graham resigned, until his retirement in 1887, he also occupied the chair of chemistry. He was elected a fellow of the Royal Society in 1855 and awarded a Royal medal in 1862. He died on May 6, 1904, at Hindhead, Surrey.
Williamson's earliest work (1844) was on the decomposition of oxides and salts by chlorine, and in this he threw considerable light on the action of chlorine on bases; shortly afterwards he published papers on ozone, and on the composition of Prussian blue. His most famous work was, however, done during his first few years at University college, and dealt with the problem of etherification. In the course of this work he definitely settled the vexed problem of the relationship of alcohol, ether and water. He suggested that alcohols, ethers, acids and their derivatives all belong to the "water type" of compound, and thus attempted to introduce a unifying principle into this aspect of organic chemistry. In the course of his work Williamson established the molecular formulae of alcohol and ether, and in this way he helped in the revival of Avogadro's hypothesis, which had lain dormant since 1811, and confirmed the views of Laurent and Gerhardt on atoms and molecules. Various aspects of Williamson's work on
etherification helped in the development of structural organic chemistry, and although he made no direct contribution to the modern side of the subject, yet his investigations helped very materially to bring about a more definite conception of the constitution of organic compounds. In the course of his researches he prepared the first mixed ether (methyl ethyl ether) and, with Kay, he synthesized ethylene glycol (1854). Williamson, in his papers explains the action of sulphuric acid in the production of ether from alcohol by saying that an intermediate compound of the acid and alcohol—ethyl sulphuric acid—is first formed, and this reacts with more alcohol to regenerate the acid and liberate ether and water. This is the first recorded instance of the explana tion of catalysis by what has become known as the "intermediate compound" theory.
His papers on Etherification and the Constitution of Salts were re printed by the Alembic Club (Edinburgh, 1902). See obituary notice, Proc. Roy. Soc. (1907); and Sir W. Tilden, Famous Chemists (1921).