Calcium Selenite, CaSeO₃

Calcium Selenite, CaSeO₃, can be obtained in the anhydrous form as crystalline grains by the action of selenious acid on calcium carbonate. It is not very soluble in water. The hydrate, 3CaSeO₃.4H₂O, is obtained in prismatic crystals by the action of sodium selenite on calcium chloride solution, and a dihydrate, CaSeO₃.2H₂O, in silky efflorescent crystals, can also be prepared.

An anhydrous acid salt, CaSeO₃.SeO₂, is deposited at 60° C. from acid solutions of the selenite, and by evaporation at ordinary temperatures, the compound CaH₂Se₂O₆.H₂O can be obtained in prisms and in hexagonal plates which are very soluble in water and unchanged by exposure to the atmosphere.