Gaudin, Marc Antoine Augustin

(b. Saintes, France, 5 April 1804; d. Paris, France, 2 April 1880)

chemistry.

Despite an unacademic family background (his father was a shopkeeper), Gaudin was active in science at an early age. In 1826, from Rochefort, he submitted his first paper to the Académic des Sciences in Paris, and in 1827 he gained the inspiration for much of his later work when he attended Ampère’s lectures at the Collège de France. From 1835 to 1864 Gaudin was a calculator at the Bureau des Longitudes in Paris but, never holding a teaching or research post, he remained outside the Parisian scientific establishment. His one application for membership in the Académie des Sciences (1851) was unsuccessful, and the only formal recognition of his work by the Academy came in 1867, when he was awarded the Prix Trémont.

Gaudin’s most important work was concerned with the arrangement of atoms within molecules and of molecules within crystals. The earliest statement of his views was contained in two short notes that he submitted to the Académie des Sciences in 1831 and 1832. The first of these notes, published in 1833, is remarkable since it contains a clear exposition of the gas hypothesis of Avogadro written some twenty-five years before the work of Cannizzaro and the Karlsruhe Congress made the hypothesis widely acceptable. Gaudin supported the hypothesis not in the form given it by Ampére but in its modern form. He correctly reconciled it with Gay-Lussac’s law of combining volumes by supposing that the common elementary gases, such as hydrogen and oxygen, were diatomic, but that other gaseous substances, mercury vapor, for example, were monatomic, while others, notably many compound gases, were triatomic, and others again were of still greater complexity.

Of the other issues arising in the papers of 1831–1833 the one that was to prove most absorbing for Gaudin concerned the possible relationship between the physical and chemical properties of substances and the spatial arrangement of the atoms that composed them. It was not until 1847 that he returned to the problem, but from that year he wrote extensively on the subject until 1873, when he published his views in a definitive form in his L’architecture du monde des atomes. In the forty years that had elapsed since they were first expounded, his ideas had changed little, and they were largely obsolete by 1873. Not surprisingly, the book received little attention and stimulated no further work.

Despite his obvious debt to Ampére and to Haüy, Gaudin’s treatment of molecular and crystalline structure showed a good deal of originality. He rejected Ampère’s assumption that even the simplest molecules were polyhedral; and although he adopted a polyhedral form for the more complex molecules, he also abandoned Ampére’s set of basic molecular shapes. Instead he chose his structures in accordance with a rigorously held belief that the atoms within a molecule were always arranged symmetrically. Hence any structure Gaudin proposed had not only to be consistent with the usual crystallographic data and the evidence of chemical composition but also to show symmetry, and this restriction caused his views on crystal structure to deviate considerably from those of Ampère and Haüy. His preoccupation with symmetry also affected his views on chemical combination. In particular it led him to reject the theory of radicals and the type theory, since he believed that symmetry would be destroyed by the simple replacement of certain atoms by others. According to Gaudin, it was only by a complete rearrangement of the atoms of the combining molecules that symmetry could be restored after a reaction.

In his long scientific career Gaudin was active in several other lines of research. He worked in microscopy, invented an ingenious pneumatic pump (1827), and showed a special interest in experimental work at high temperatures. It was Gaudin who prepared the fused quartz for Biot’s work on optical activity in 1839, and he is noted for his method of preparing artificial rubies using an oxyhydrogen blowpipe. An important pioneer of photography, he wrote a comprehensive textbook on this subject in 1844. In his photographic work he was closely associated with his brother Alexis.

BIBLIOGRAPHY

I. Original Works. L’architecture du monde des atomes dévoilant la structure des composés chimiques et leur cristallogénie (Paris, 1873) is Gaudin’s most important book, but he published much else. His Traité pratique de photographie (Paris, 1844) is an admirable practical handbook of photography, and “Recherches sur la structure intime des corps inorganiques définis,” in Annales de chimie et de physique, 2nd ser., 52 (1833), 113–133, is of great historical interest. Most of his numerous communications to the Académie des Sciences are noted in Comptes rendus hebdomadaires des séances de l’Académie des sciences.

II. Secondary Liteature. The best studies are M. Delépine, “Une étape de la notion d’atomes et de molécules,” in Bulletin de la Société chimique de France, 5th ser., 2 (1935), 1–15, with supp. note by G. Urbain, 16–17; and S. H. Mauskopf, “The Atomic Structural Theories of Ampère and Gaudin: Molecular Speculation and Avogadro’s Hypothesis,” in Isis, 60 (1969), 61–74. Biographical information is scarce, but a useful supp. to the standard biographical dictionaries, such as the Nouvelle biographie générale, is in Bulletin de la Société des archives historiques de la Saintonge et de l’Aunis, 2 (1880), 163.

Robert Fox.