Stanislao Cannizzaro

Stanislao Cannizzaro

1826-1910

He was professor of chemistry at Pisa, Italy, and subsequently occupied the same position at Turin, Italy. In 1851 he was appointed professor of physical chemistry at the National College of Alessandria, Piedmont, Italy, where he discovered that aromatic aldehydes are decomposed by an alcoholic solution of potassium hydroxide into a mixture of the corresponding acid and alcohol, e.g. benzaldehyde into benzoic acid and benzyl alcohol, the Cannizzaro reaction. In conjunction with F. S. Cloz (1817-1883) made his first contribution to chemical research in 1851, when they prepared cyanamide by the action of ammonia on cyanogens chloride in ethereal solution. In 1858 he insisted on the distinction, previously hypothesised by Avogadro, between molecular and atomic weights, and showed how the atomic weights of elements contained in volatile compounds can be deduced from the molecular weights of those compounds, and how the atomic weights of elements of whose compounds the vapor densities are unknown can be ascertained from a knowledge of their specific heats.