NaHS

Sodium hydrosulfide, or NaHS, is an inorganic salt consisting of the sodium cation and the hydrosulfide anion (HS−). It is a white to off-white hygroscopic solid that dissolves readily in water, forming alkaline solutions. In solution, HS− behaves as an amphiprotic species, able to act as both a base and a weak acid. Under acidic conditions, NaHS releases hydrogen sulfide (H2S), a toxic gas.

Production and preparation methods commonly involve reactions between related sulfur species. NaHS can be prepared by reacting sodium sulfide (Na2S) with hydrogen sulfide (H2S): Na2S + H2S ⇌ 2 NaHS. It can also be formed by neutralizing H2S with sodium hydroxide: H2S + NaOH → NaHS + H2O. Upon heating, NaHS thermally decomposes to release H2S and form disodium sulfide: 2 NaHS → Na2S + H2S.

Uses of NaHS are primarily in industrial chemistry and mineral processing. It serves as a source of HS− for chemical synthesis and as a precursor to sodium sulfide (Na2S). In the mining industry, NaHS is used in flotation processes to collect sulfide minerals. It also functions as a reducing agent and as a reagent in various sulfur-containing syntheses.

Safety and handling considerations are important due to toxicity and malodorous gases. NaHS solutions release H2S upon acidification, which is highly toxic and requires proper ventilation and gas-detection measures. It should be stored in airtight containers, away from acids and oxidizers, and handled with appropriate personal protective equipment.

See also: sodium sulfide, hydrosulfide salts.