Calcium Hydrosulphide, Ca(SH)₂

Calcium Hydrosulphide, Ca(SH)₂, is formed in solution by saturating lime-water with sulphuretted hydrogen, by the action of water or sulphuretted hydrogen solution under pressure on the sulphide, or by the action of sulphuretted hydrogen on a suspension of calcium carbonate in water. By treating milk of lime containing 1 part of hydrate to 4 of water with sulphuretted hydrogen, and cooling to a low temperature in the same gas, colourless prismatic crystals of the hexahydrate, Ca(SH)₂.6H₂O, are obtained. They are very soluble in water and alcohol, 4 parts by weight of the crystals dissolving in 1 of water at ordinary temperatures, and the compound is readily hydrolysed, only the hydroxide being left if the solution is dilute. Heat facilitates the reaction. On warming, the crystals of the hydrosulphide melt with decomposition into sulphuretted hydrogen and calcium monosulphide.

The depilatory properties of calcium hydrosulphide have long been known.