Henri Deveaux

Background

Henri Deveaux was born on July 6, 1862 in Etaules, Charente-Maritime, France, into a Protestant family of sailors and farmers.

Education

Devaux studied at the University of Bordeaux. His doctoral thesis (1889) concerned the gaseous exchanges in plant tissues.

Career

Devaux worked for five years under the leading botanists of the University of Paris. 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 mono-molecular films depends essentially on the reactivity of specific, or polar groups of the molecules. Devaux’s scientific activity continued until his last years.

Achievements

• Henri Deveaux imposed himself in the early 20th century as one of France’s specialists in the physics of surfaces and thin films. 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.

Religion

Devaux was a fervent evangelical Christian, very active in this community.

Membership

Devaux was a corresponding member (1933) and then non-resident member (1946) of the Académie des Sciences.

Personality

Defender of the concept of complementarity, Devaux regularly combined scientific research with theological reflection in his laboratory notebooks, a practice which he sometimes extended to his scientific papers.

References

• Journal of the American Chemical Society, Volume 39
  1917