Cadmium Selenites

A yellow crystalline powder of the acid selenite, 2CdO.3SeO₂.H₂O, deposits when cadmium carbonate is heated in a solution of selenious acid. It is insoluble in water, soluble in acids, and leaves a residue of cadmium oxide on calcination. If it is heated in a sealed tube to 230° C. with three times its weight of selenium dioxide it forms yellow orthorhombic crystals of the biselenite, which has similar properties (CdO.2SeO₂). If heated with water in a sealed tube to 200° C. it forms the neutral anhydrous selenite, CdSeO₃. This is a pale yellow powder consisting of small orthorhombic crystals. It behaves like the acid salts towards water, acids, and heat.

This salt has also been obtained by dissolving cadmium hydroxide in selenious acid.

The hydrate, 2CdSeO₃.3H₂O, precipitates as a white amorphous powder by adding a solution of sodium selenite to a solution of zinc chloride.

The salts, 3CdO.4SeO₂.H₂O and 3CdO.4SeO₂.2H₂O, have been prepared.