Zinc Selenites

The biselenite, ZnO.2SeO₂.3H₂O, has been prepared in colourless transparent crystals by adding 5-6 grm. zinc carbonate, in successive portions, to a solution containing 20 grm. selenium dioxide in 30 grm. water. The deposit becomes crystalline after decanting off the syrupy liquid.

The anhydrous neutral selenite, ZnSeO₃, is obtained by heating the mother-liquor from the preparation of the biselenite in a sealed tube at 200° C. It separates as prismatic orthorhombic crystals that are insoluble in water, soluble in acids, and calcine in air to zinc oxide. The biselenite also becomes zinc oxide when heated in air, dissolves in cold water, and is converted by hot water into white pulverulent ZnSeO₃.

The dihydrate, ZnSeO₃.2H₂O, and the monohydrate have also been prepared.

Orange crystals, resembling potassium chromate, of the tetraselenite, ZnSeO₃.3H₂SeO₃, were obtained by dissolving zinc in a concentrated solution of selenious acid. They are stable in air, very soluble in water, and become white and opaque at 40° C.