Sodium hydrosulfide

Sodium hydrosulfide (CAS 16721-80-5), also known as sodium bisulfide or sodium mercaptan, is an inorganic sulfur compound with the formula HNaS. It carries no assigned E-code and is commercially supplied as a solid or in aqueous solution. It is registered under EC number 240-778-0.

In leather processing, sodium hydrosulfide depilates hides by breaking disulfide bonds in keratin, enabling efficient hair removal without mechanical damage. In mining, it selectively activates sulfide mineral surfaces during froth flotation, improving metal recovery rates. Water treatment facilities use it to reduce hexavalent chromium and neutralize oxidising agents in industrial effluent.

Sodium hydrosulfide is available in technical and industrial grades, supplied as crystalline solid or aqueous solution, typically in concentrations of 70-72% flake or 25-45% liquid. It falls under REACH regulation and requires a Safety Data Sheet compliant with EU GHS standards. Packaging formats include drums, IBCs, and bulk tanker delivery for liquid grades.