Wikipedia
Sodium hydrosulfide is the chemical compound with the formula NaHS. This compound is the product of the half neutralization of hydrogen sulfide with sodium hydroxide. NaHS is a useful reagent for the synthesis of organic and inorganic sulfur compounds, sometimes as a solid reagent, and more often as an aqueous solution. Solid NaHS is colorless and typically smells like HS due to hydrolysis by atmospheric moisture. In contrast with sodium sulfide, NaS, which is insoluble in organic solvents, NaHS, being a 1:1 electrolyte, is more soluble. Alternatively, in place of NaHS, HS can be treated with an organic amine to generate an ammonium salt. Solutions of HS are sensitive to oxygen, converting mainly to polysulfides, indicated by the appearance of yellow.