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Deville, Henri Étienne Sainte-Claire

aluminium sodium metal temperature

(1818–81) French chemist: developed methods for making light metals in quantity; studied high temperature reactions.

Deville is one of the few major 19th-c scientists to be born in the West Indies, where his family had been leading citizens for two centuries. With his older brother Charles he was educated in Paris. He chose medicine but was soon attracted to chemistry; in the 1840s he worked on essential oils and obtained methylbenzene and methyl benzoate from balsam of Tolu, but his chemical fame began in 1849 when he made the crystalline and highly reactive dinitrogen pentoxide by treating warm silver nitrate with chlorine. From 1851 he held a post at the École Normal Supérieure, with as a colleague and close friend from 1857. The main work of the institution was to train senior school teachers, which Deville did for 30 years while maintaining a major research output. He was a masterly lecturer and experimentalist, uninvolved in disputes over theory. Realizing that sodium metal in quantity would be of great use, he developed a large-scale method for making it by reduction of sodium carbonate with carbon. One target was to use sodium to make aluminium by reduction of AlCl3 . In 1855 Deville was summoned to show aluminium, then rare, to the Emperor; the latter was attracted by the idea of fitting his troops with helmets of the new metal, and a government grant to set up a pilot plant was arranged. Success followed; bars of aluminium were shown at the 1855 Exposition, and it quickly ceased to be mainly used for jewellery. Soon Deville made pure magnesium in quantity, and titanium, and crystalline boron and silicon, all by reduction of chlorides with sodium metal. He worked on the platinum metals and in 1872 was given the task of making the platinum–iridium (90–10) alloy for the standard kilogram and metre.

His interest in high temperature chemistry had begun in the 1850s and his oxy-hydrogen blowpipe method led to technical welding methods as well as studies of minerals and high-melting metals. From 1857 he also studied vapour densities, using porcelain bulbs and the vapour of boiling metal (Hg, Cd or Zn) to give a constant high temperature. He found that relative molecular mass could change with temperature; thus aluminium chloride is mainly Al2 Cl6 at 500°C, but AlCl3 at 1000°C. Chemical changes due to heat which reverse on cooling were described as dissociations by Deville, who first fully examined such changes. He found that at high temperatures H2O, CO2 , CO, HCl and SO2 all dissociated.

Devine, Loretta (1949–) [next]

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