The perfectly pure metal may be prepared by heating the oxide or oxalate in a current of hydrogen; when obtained at a low temperature it is a black powder which oxidizes in air with incandescence; produced at higher temperatures the metal is not pyrophoric. Peligot obtained it as minute tetragonal octahedra and cubes by reducing ferrous chloride in hydrogen.
Ferrous oxide is obtained when ferric oxide is reduced in hydrogen at 300 as a black pyrophoric powder.
The condensation of acetylene to benzene is also possible at ordinary temperatures by leading the gas over pyrophoric iron, nickel, cobalt, or spongy platinum (P. Sabatier and J.
Prelinger's manganese has a specific gravity of 7.42, and the variety obtained by distilling pure manganese amalgam in vacuo is pyrophoric (A.
Operating Precautions A COSHH Special Assessment must be carried out before using pyrophoric material.
By electrolysis it yields uranium dioxide as a pyrophoric powder, and peruranic hydroxide, U04.2H20, when treated with hydrogen peroxide.
When obtained by reduction processes at as low a temperature as possible the finely divided metal so formed is pyrophoric, and according to P. Schutzenberger (Comptes rendus, 1891,113, p. 177) dry hydrochloric acid gas converts this form into nickel chloride and a volatile compound of composition NiHC1.
Tungsten dioxide, W02, formed on reducing the trioxide by hydrogen at a red heat or a mixture of the trioxide and hydrochloric acid with zinc, or by decomposing the tetrachloride with water, is a brown strongly pyrophoric powder, which must be cooled in hydrogen before being brought into contact with air.
At a high temperature hydrogen reduces it to the metal partly in the form of a black pyrophoric powder.
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