Jean Baptiste Perrin

Born Sept. 30, 1870, in Lille; died Apr. 17, 1942, in New York. French physicist. Member of the Académie des Sciences in Paris (1923).

Perrin worked at the Ecole Normale Supérieure in Paris after graduating from that institution in 1894. He joined the faculty of the University of Paris in 1898 and was a professor there from 1910 to 1940. In 1940, after the capitulation of France, he came to the USA.

Between 1895 and 1898, Perrin investigated cathode rays and X rays; he demonstrated that cathode rays are streams of charged particles. He did research on electrokinetic phenomena and in 1904 proposed a device for studying electroosmosis. Perrin’s work on Brownian motion provided experimental confirmation of the Einstein-Smoluchowski theory; it permitted him to obtain a value for Avogadro’s number that was in good agreement with values obtained by other methods and to prove conclusively the reality of molecules. Perrin also demonstrated the bimolecular structure of thin soap films. Together with his son Francis, he did research on fluorescence phenomena. Perrin was a popularizer of science, and his book Atoms (1913; Russian translation, 1924) has become a classic.

Perrin was an honorary member of the Academy of Sciences of the USSR (1929; corresponding member, 1924). He was awarded a Nobel Prize in 1926.