Calcium hydrosulfide is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula or . It is formed from the reaction of calcium hydroxide or calcium carbonate with hydrogen sulfide: :Ca(OH)₂ + 2H₂S → Ca(HS)₂ + 2H₂O :CaCO₃ + 2H₂S → Ca(HS)₂+H₂O+CO₂

References

Calcium compounds Hydrosulfides {{inorganic-compound-stub