Cannizzaro, Stanislao

Cannizzaro, Stanislao (stänēslä`ō kän-nēt-tsä`rō), 1826–1910, Italian chemist. From 1861 he was professor at Palermo and from 1871 at Rome, where he was also a member of the senate and of the council of public instruction. He is known for his discovery of cyanamide, for obtaining alcohols from aldehydes by Cannizzaro's reaction (in which benzaldehyde is converted to benzoic acid and benzyl alcohol, in the presence of a strong alkali), and for distinguishing between molecular and atomic weights. Of fundamental importance was his explanation of how atomic weights may be determined systematically on the basis of Avogadro's law regarding the volumes of gases and vapors; hydrogen is used as a reference standard and, for elements whose compounds are not volatile (do not form vapors by evaporation), the specific heat is used in the determination of the atomic weight.