Cadmium Selenide, CdSe

When cadmium and selenium are heated together they form cadmium selenide, CdSe. The reaction begins at 360° C. and becomes more vigorous with rising temperature. The selenide is infusible up to 1350° C., and its density is 5.81 at 16° C. It also results when cadmium is heated in hydrogen selenide.

Dark brown CdSe is precipitated from solutions of cadmium salts by hydrogen selenide or alkaline selenides. Acids liberate hydrogen selenide from it.

When cadmium and selenium vapours were heated at a high temperature the resulting selenide was a crystalline mass, golden yellow and lustrous. Margottet obtained lamellated crystals belonging to the regular system by subliming the selenide in hydrogen. They were yellow to blood-red, and their density was 5.80. Brown rhombic crystals, isomorphous with the corresponding zinc selenide, of density 5.81 at 15° C., were obtained by heating cadmium chloride in a current of hydrogen containing hydrogen selenide.

Cadmium selenide is easily decomposed by acids, and chlorine displaces selenium from it on warming. Cadmium oxide and selenium dioxide are formed when it is heated in a current of oxygen.

[Cd] + [Se] = [CdSe] (cryst.)+26.0 Cal.

The corresponding figure for precipitated CdSe is 22.9 Cal.