Denbray, Henri Jules

(b. Amiens, France, 26 July 1827; d. Paris, France, 19 July 1888)

chemistry.

Debray studied in Paris at the École Normale Supérieure. In 1850 he began teaching at the Lycée Charlemagne, and in 1855 he received his doctorate. From 1855 to 1868 he was lecturer at the École Normale, and from 1868 he was lecturer at the École Polytechnique. He held the latter position until his death, serving at the same time as assayer at the mint. In 1877 he was elected to the Institut dc France.

Debray was a talented writer of textbooks. His Cours élémentaire de chimie appeared in eight editions between 1863 and 1871. He undertook his first scientific work in collaboration with St. Claire Deville, a professor at the École Normale. Their first experiments were in the use of an oxyhydrogen blowpipe to melt platinum. They were commissioned by the Russian government to investigate the applicability of platinum–iridium alloys to coinage and ascertained that these alloys resist corrosion even better than platinum does. At their suggestion the standard meter in Paris was made, under their supervision, from an alloy composed of 90 percent platinum and 10 percent iridium. In further publications Debray reported on investigations of the compounds of tungsten, arsenic, and antimony; on the properties of rhodium; and on the compounds in the platinum metals family and methods of separating them.

Debray also concerned himself with dissociation phenomena. He established that in the dissociation of calcium carbonate the pressure of the carbon dioxide at a given temperature is constant and independent of the degree of dissociation. He made the same finding regarding the water-vapor pressure over hydrated salts. (Wiedemann later raised priority claims in this matter, but Debray obtained his results without knowledge of the results that Wiedemann had published in a little-known journal.) Debray also determined the density of mercurous chloride vapor.

BIBLIOGRAPHY

Debray’s books include Métallurgie du platine et des métaux qui l’accompagnent (Paris, 1863); and Cours élémentaire de chimie (Paris, 1863; 8th ed., 1876). There are about fifty publications in French periodicals.

The only secondary literature is a short notice in Poggendorff, III, 337–338.

F. SzabadvÁry