Calcium Bisulphite, Ca(HSO₃)₂

Calcium sulphite is soluble in an aqueous solution of sulphur dioxide, probably on account of the formation of an acid sulphite, Ca(HSO₃)₂. Elbs and Becker found the maximum solubility to be 9.3 grm. per litre, but according to Frank much more concentrated solutions can be obtained. The salt has not been obtained in the solid state.

A solution of calcium bisulphite, Ca(HSO₃)₂, prepared commercially by the action of sulphur dioxide on milk of lime, is used as an antiseptic in the brewing industry. It is also employed for bleaching cellulose in the manufacture of paper.