The presence in a metal of even small proportions of arsenide generally leads to considerable deterioration in mechanical qualities.
It occurs in the uncombined condition and alloyed with iron in meteorites; as sulphide in millerite and nickel blende, as arsenide in niccolite and cloanthite, and frequently in combination with arsenic and antimony in the form of complex sulphides.
An antimony phosphide and arsenide are known, as is also a thiophosphate, SbPS 4, which is prepared by heating together antimony trichloride and phosphorus pentasulphide.
Arsenic forms two hydrides: - The dihydride, As2H2, is a brown velvety powder formed when sodium or potassium arsenide is decomposed by water.
Arsenic trihydride (arsine or arseniuretted hydrogen), AsH3, is formed by decomposing zinc arsenide with dilute sulphuric acid; by the action of nascent hydrogen on arsenious compounds, and by the electrolysis of solutions of arsenious and arsenic acids; it is also a product of the action of organic matter on many arsenic compounds.