Cadmium Arsenide

The freezing-point, density, and atomic volume curves, supplemented by an examination of the microstructure, confirm the existence of Cd₃As₂ and CdAs₂. Cd₃As₂ is reddish grey, of density 6.25, and it melts at 721° C. Its hardness is less than 3.5. CdAs₂ is bluish grey, of density 5.86, and it melts at 621° C. Its hardness is 3.5–4.0.

Cd₃As₂ has been prepared by subjecting cadmium and arsenic, in appropriate proportions, to a pressure of 6500 atmospheres. Some Cd₆As was formed when cadmium and arsenic were melted together, but Cd₃As₂ is readily formed by heating cadmium in arsenic vapour mixed with hydrogen or an inert gas. It was thus obtained in reddish octahedra of density 6.211 at 15° C. It reacts with acids and the halogens like the arsenides in general.

Descamps obtained Cd₃As by reducing cadmium arsenate with potassium cyanide. It was white, with a slight reddish colour and a metallic lustre.