Sodium hydrosulfide

Sodium hydrosulfide (CAS 16721-80-5), also known as sodium sulfhydrate and commonly abbreviated as NaHS, is an inorganic sulfide salt used across heavy industry as a reactive sulfur source and chemical intermediate. It functions primarily as a reducing agent, precipitant, and flotation reagent in processes where controlled sulfide chemistry is required. In mining and metals processing, NaHS is used as a selective flotation depressant.

It acts as a metal sulfide precipitant to recover copper, zinc, and other non-ferrous metals from ore slurries. Pulp and paper manufacturers use it in kraft cooking liquor to improve pulping efficiency and delignification rates. Leather processors apply it as a depilatory agent to remove hair from hides during the beamhouse stage, a step critical to tannery throughput. In wastewater treatment, it precipitates heavy metals from industrial effluent streams.

This process creates insoluble sulfides, supporting compliance with discharge limits. Sodium hydrosulfide is supplied as an aqueous solution, typically at concentrations around 45% NaHS, and in solid flake form. Technical grade is the standard commercial specification across most industrial applications. Solution grades are common for continuous-process industries due to handling and dosing convenience.