(b. Etaules, Charente-Maritime, France, 6 July 1862; d. Bordeaux, France, 14 March 1956)
plant physiology, molecular physics.
Devaux was born into a Protestant family of sailors and farmers. After graduation from the University of Bordeaux he worked for five years under the leading botanists of the University of Paris. His doctoral thesis (1889) concerned the gaseous exchanges in plant tissues. He then returned to the University of Bordeaux, where he held the chair of plant physiology from 1906 until his retirement in 1932. Devaux soon displayed his inclination toward physical chemistry, showing as early as 1896 that aquatic plants accumulate polyvalent metallic ions, such as lead, in their cell membranes, even when the surrounding solution contains only traces of the ion. This accumulation is reversed when a large concentration of a monovalent ion, such as sodium or potassium, is added to the external solution. This was exactly the process that, nearly forty years later, was known as ion exchange, a process with wide scientific and industrial applications.
From 1903 on, Devaux was interested in the physics of surfaces. In 1890 Lord Rayleigh, and shortly afterward Agnes Pockels, had demonstrated that the surface tension of water is reduced when a film of oil, presumably one molecule thick, is spread over the surface. Direct evidence of surface films one molecule thick was presented by Devaux in 1903. He applied this demonstration to a wide range of films, particularly to proteins. The apparatus used by Devaux was of the most elegant simplicity: a photographic tray filled with either water or mercury lightly sprinkled with talcum powder. When a minute amount of film-forming substance is deposited on the liquid surface, the talcum particles are repelled and reassemble in the form of a circle. By a simple calculation involving the diameter of this circle, Devaux obtained the molecular weights of film-forming substances, particularly proteins and heavy organic acids. The results were at first ignored in France, but a decade later they were noticed by Irving Langmuir. The famous American physicist, who was to make such important contributions to the study of surfaces, gave full credit in many of his publications to Devaux for having demonstrated that the behavior of monomolecular films depends essentially on the reactivity of specific, or polar groups of the molecules. Devaux’s scientific activity continued until his last years. The “wetting” of solid surfaces, the hydration of molecules in surface films, and the evaporation of odorous substances are among the fields to which he made significant contributions.
I. Original Works. Devaux’s works appeared mainly in local scientific publications of limited circulation, but some of his most important papers appeared in the following accessible journals: “De l’absorption des poisons métalliques très dilués par les cellules végétales,” in Comptes rendus hebdomadaires des séances de l’Académiedes sciences, 132 (1901), 717–719; “Oil Films on Water and on Mercury,” in Annual Report of the Board of Regents of The Smithsonian Institution (Washington, D.C., 1913), pp. 261–273; “Action rapide des solutions salines sur les plantes vivantes: déplacement réversible d’une partie des substances basiques contenues dans la plante,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 162 (1916), 561–564; “Ce qu’il suffit d’une souillure pour altérer la mouillabilité d’une surface. Étude sur le contact d’un liquide avec un solide,” in Journal de physique, 4 (1923), 293–309; “La mouillabilité des substances insolubles et les remarquables puissances d’attraction existant à l’interface des liquides non miscibles,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 197 (1933), 105–108; “L’adsorption de l’ovalbumine à la surface libre de ses solutions, lorsque la concentration de celles-ci varie de 10-2 à 10-8,” ibid. 200 (1935), 1560–1565; “Action de l’acide carbonique sur l’extension de l’ovalbumine à la surface de l’eau, et variations de l’épaisseur de ces lames en couches monomoléculaires,” ibid, 199 (1934), 1352–1354; “Détermination de l’épaisseur de la membrane d’albumine formée entre l’eau et la benzine et propriétés de cette membrane,” ibid, 202 (1936), 1957–1960; “Sur une représentation macroscopique des lames monomoléculaires et leur comportement à divers états de compression,” ibid.,206 (1938), 1693–1696, written with L. Pallu; “Étude expérimentale des lames formées de graines sur le mercure. Possibilité de déterminer sur les lames minces les 3 dimensions principals des molécules,” in Journal de physique, 9 (1938), 441–446, written with L. Pallu; “Un rapport remarquable entre la constitution cellulaire et la mouillabilité du corps des mousses,” in Comptes rendus hebdomadaires des séanees de l’Académie des sciences, 208 (1939), 1260–1263; “La mouillabilité des surfaces solides,” ibid,210 (1940), 27–29; “Les lames minces hydrophiles,” ibid., 211 (1940), 91–94; “L’adsorption d’une couronne de molécules d’eau autour de chaque molécule d’un sel étendu en lame mince,” ibid., 212 (1941), 588–590; “L’adsorption hygroscopique d’une couronne de molécules d’eau autour de chaque molécule des substances étendues en lame monomoléculaire sur le mercure,” in Mémoires de l’Académie des sciences de l’Institut de France, 66 (1942), 1–28; and “L’arrangement des particules flottant sur du mercure, sous l’influence d’un champ électrique,” in Journal de physique, 4 (1943), 185–196.
II. Secondary Literature Irving Langmuir gives an extensive account of Devaux’s early work in surface physics in “The Constitution and Fundamental Properties of Liquids,” in Journal of the American Chemical Society, 39 (1917), 1848–1906. A complete bibliography up to 1941 can be found in Actualités scientifzques et industrielles, no. 932 (Paris, 1942), pp. 23–36. A detailed obituary was published by Gordin Kaplan, “Henri Devaux, Plant Physiologist, Pioneer of Surface Physics,” in Science, 124 (1956), 1017–1018.
A. M. Monnier
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