CANNIZZARO, STANISLAO

born July 13, 1826, Palermo, Sicily, Kingdom of the Two Sicilies died May 10, 1910, Rome, Italy Italian chemist, teacher, and legislator who recognized the distinction between atomic and molecular weights and also discovered the Cannizzaro reaction. At the University of Pisa (184546), Cannizzaro assisted Rafaelle Piria, who first prepared salicylic acid. Condemned to death for his part in the Sicilian revolution (1848), Cannizzaro escaped to Marseille and arrived in Paris (1849). In the laboratory of Michel-Eugne Chevreul, he helped prepare cyanamide in 1851, the year he became professor of chemistry and physics at the Technical Institute of Alessandria, Piedmont (now in Italy). There he discovered (1853) that treatment of benzaldehyde with a concentrated alcoholic hydroxide (Cannizzaro reaction) produced equal amounts of benzyl alcohol and the salt of benzoic acid. Becoming professor of chemistry at the University of Genoa in 1855, he showed in 1858 that the atomic weights of the elements in the molecules of a volatile compound can be calculated by applying Avogadro's principle concerning gases (gram-molecular weights of different gases occupy equal volumes at the same temperature and pressure); in the case of a nonvolatile compound for which a vapour density is unknown, the atomic weights can be calculated by a measurement of specific heat. In 1891 his finding brought him the Copley medal from the Royal Society of London. While professor of inorganic and organic chemistry at the University of Palermo (186171), he studied aromatic compounds and amines. He was appointed to the chemistry chair at the University of Rome in 1871 and entered the Italian Senate that same year. He became vice president of the assembly and a member of the public instruction council.