Perrin, Jean Baptiste

PERRIN, JEAN BAPTISTE

(b. Lille, France, 30 September 1870; d. New York, New York, 17 April 1942)

physical chemistry.

Along with his two sisters, Perrin was raised in modest circumstances by his mother, after his father, an army officer, died of wounds received in the Franco-Prussian War. Perrin obtained his secondary education in Lyons and at the Lycée Janson-de-Sailly in Paris, where his special preparation in mathematics enabled him, in 1891, after serving one year in the army, to gain entrance into the École Normale Supérieure. In 1895 he became agrégé-préparateur at the École Normale, and two years later he completed his doctorate.

Perrin’s years as a student at the Ecole Normale were exceptionally formative owing primarily to the influence of his teacher, Marcel Brillouin, who was an outspoken advocate of Boltzmann’s “statistical mechanics” and an outspoken adversary of Ostwald’s and Mach’s “energetics.” It is possible to detect Perrin’s atomistic biases even in his first paper of 1895, in which he reported experiments demonstrating that cathode rays are negatively charged by collecting them in a “Faraday cup” (an open-ended metal cylinder with appropriate electrical connections). In 1896 Perrin won the Joule Prize of the Royal Society for his experiments on cathode rays and for certain preliminary studies on Rontgen’s recently discovered X rays; this formed the basis for his doctoral thesis the following year.

Soon after receiving his degree, Perrin married Henriette Duportal; they had a daughter,Aline, and a son, Francis. Perrin was placed in charge of developing a course in physical chemistry at the Sorbonne, for which he wrote his pro-Boltzmannian Traite de chimie physique. Les principes (1903). For Perrin, these years, in general, were years of transition. The focus of his research shifted from cathode rays and X rays, and a general concern with the atomic hypothesis (in 1901 he suggested, for example, that the atom was like a miniature solar system), to experiments on ion transport and the whole problem of how an electrolyte transfers its charge to the walls of a container (electrisation par contact). It was out of these studies, in turn, and the stimulation provided by Siedentopf and Zsigmondy’s 1903 invention of the “slit ultramicroscope,” that Perrin’s interest arose in the behavior of colloidal particles and, in particular, in their Brownian motion. By 1906 this problem had already begun to attract his attention, and in 1908 he inaugurated his classic series of experiments on the subject.

It struck Perrin that colloidally suspended particles undergoing Brownian motion (as a result of collisions with the molecules of the surrounding fluid) should distribute themselves vertically in a definite way at equilibrium. Only after finding experimentally that their number decreases exponentially with increasing height, and only after proving that this variation (and hence a definite value of Avogadro’s number) follows from kinetic theory, did Perrin learn, through Langevin, of Einstein’s and Smoluchowki’s 1905–1906 theoretical papers on Brownian motion, and subsequently understand that his work was also consistent with theirs.

In auxiliary experiments Perrin proved that Stokes’s law (and hence his calculation of the particle’s mass) was valid for particles as small as 0.1 micron. In 1909 Perrin’s student Chaudesaigues also demonstrated the accuracy of Einstein’s prediction that the mean displacement of a given particle undergoing Brownian motion is proportioinal to the square root of the time of observation, a result that undercut earlier criticisms of Einstein’s work by Svedberg and others. During the same year Perrin continued to refine and extend his experiments (for example he verified Einstein’s formula for rotatioinal Brownian motion). Perrin’s work brought him a great deal of formal recognitioin over the years; in 1909 he was awarded the Prix Gaston Planté; he was appointed to a chair of physical chemistry especially created for him at the Sorbonne, which he held for three decades (1910–1940); in 1911 and 1921 he received invitations to the extremely influential Solvey conferences in 1923 he was elected to the Academie des sciences (he became its president in 1938); he was awarded eight honorary degrees, several prizes and membership in seven foreign academies of science and in 1926 he received the Nobel Prize for physics. His most fundamental conclusion—that he had finally uncovered irrefutable proof for the real existence of atoms—contrary to the assertions and expectations of Ostwald, Mach, and others—was soon universally accepted and popularized in his book Les atomes (1913), which went through many editions and translations.

As an army officer in World War I, Perrin worked on acoustic detection devices for submarines and other military equipment. Between 1918 and 1921 he studied the phenomenon of fluorescence and the interaction between light and matter. He simultaneously demonstrated his insight into current problems of nuclear physics by offering essentially correct, albeit qualitative, speculations on the origin of solar energy and on the nature of nuclear reactions. In subsequent years, as a convinced socialist, Perrin became increasingly involved with the institutional development of science in France. In the late 1930’s, for example, he was primarily responsible both for establishing the Centre National de la Recherche Scientifique and for founding the Palais de la Découverte in Paris. In 1940 his well-known and outspoken antifascism made it necessary for him to emigrate from France. He came to the United States, where he helped establish the French University of New York (École Libre des Hautes Études). His son, Francis, was then teaching at Columbia University, where Perrin himself had been an exchange professor in 1913. Perrin died in New York, but after the war his remains were returned to his homeland and buried in the Pantheon.

BIBLIOGRAPHY

I. Original Works. Perrin’s initial papers were “Nouvelles propriétés des rayons cathodiques,” in Comptes rendus hebdomadaires des seances de l’Academie des sciences, 121 (1895), 1130; and his doctoral thesis, “Rayons cathodiques et rayons de Roentgen,” in Annales de chimie et de physique, 11 (1897), 496–554. Two of his early Sorbonne papers were “Mecanisme de l’electrisation de contact et solutions colloïdales, “in Journal de chimie physique, 2 (1904), 601–651; 3 (1905), 50–110. He offered a summary of his 1908–1909 work (especially as it had appeared earlier in Comptes rendus ) in “Mouvement Brownien et realite moleculaire,” in Annales de chimie et de physique 18 (1909) 1–114, trans. into English by Frederick Soddy (London, 1910) and into German by J. Donau (Dresden-Leipzig, 1910). Two of Perrin’s postwar papers were “La fluorescence,” in Annales de physique, 10 (1918), 133–159, and “Matiéree et lumiere,” ibid., 11 (1919), 1–108. These papers, and later papers directed at institutioinal concerns, have been collected under the title Oeuvres scientifiques de Jean Perrin (Paris, 1950). Perrin’s two most important books are Traite de chimie physique, I. Les principes (Paris, 1903), and Les atomes (Paris, 1913).

II. Secondary Literature. The most comprehensive study of Perrin’s life and work is Mary Jo Nye, Molecular Reality (London, 1972), the bibliography of which lists all important secondary sources on Perrin, certain primary source documents not contained in Oeuvres scientifiques de Jean Perrin, and other primary source documents, for example, Einstein’s papers on Brownian motion.

Roger H. Stuewer