Stanislao Cannizzaro

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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 heatspecific heat,
ratio of the heat capacity of a substance to the heat capacity of a reference substance, usually water. Heat capacity is the amount of heat needed to change the temperature of a unit mass 1°.
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 is used in the determination of the atomic weight.

Cannizzaro, Stanislao


Born July 13, 1826, in Palermo; died May 10, 1910, in Rome. Italian chemist. One of the originators of the atom-molecular theory.

Cannizzaro studied medicine at the universities of Palermo and Pisa. In 1845 he began working with the Italian chemist R. Piria (1814–65). Cannizzaro participated in a national uprising in Sicily, emigrating to France (1849) after its suppression. In Paris he collaborated with the French chemist F. Cloëz (1817–83); in 1851 they successfully prepared cyanamide by the reaction CNC1 + NH3 = CNNH2 + HC1. Upon his return to Italy, Cannizzaro was appointed professor of chemistry at the National College in Alessandria (1851), where he discovered the Cannizzaro reaction. He was a professor at the universities of Genoa (from 1856), Palermo (from 1861), and Rome (1871–1910); it was in Rome that he began studying santonin and its derivatives (from 1873).

Cannizzaro’s historical contributions to science include the refinement of atomic weight values for certain elements (metals in particular) on the basis of Dulong and Petit’s law and the demonstration of the universal application of Avogadro’s principle to determining the molecular weights of simple and complex substances in the vaporous state. He rigorously differentiated the concepts of “atom,” “equivalent” (combining weight), and “molecule.” Cannizzaro’s views were reflected in his published works (1858) and expounded in his address to the International Congress of Chemists held at Karlsruhe in 1860. They received universal recognition in subsequent years.


Scritti vari e lettere inedite. Rome, 1926.
In Russian translation:
Obzor razvitiia poniatiia ob atome, chastitse i ekvivalente i razlichnykh sistem formul Kiev, 1873.
O predelakh i o forme teoreticheskogo prepodavaniia khimii. Kiev, 1873.


Mendeleev, D. I. “Khimicheskii kongress v Karlsrue.” Soch., vol. 15. Moscow-Leningrad, 1949.
Giua, M. Istoriia khimii. Moscow, 1966. (Translated from Italian.)
Bykov, G. V., and V. A. Kritsman. Stanislao Kannitstsaro. Ocherk zhizni i deiatel’nosti. Moscow, 1972. (Includes a bibliography of Cannizzaro’s works.)


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