Reactivity and Uses
Calcium sulfide decomposes upon contact with water, including moist air, giving a mixture of Ca(SH)2, Ca(OH)2, and Ca(SH)(OH).
- CaS + H2O → Ca(SH)(OH)
- Ca(SH)(OH) + H2O → Ca(OH)2 + H2S
Milk of lime, Ca(OH)2, reacts with elemental sulfur to give a "lime-sulfur", which has been used as an insecticide. The active ingredient is probably a calcium polysulfide, not CaS.
It reacts with acids such as hydrochloric acid to release toxic hydrogen sulfide gas.
- CaS + 2 HCl → CaCl2 + H2S
Read more about this topic: Calcium Sulfide