Hydrosulfide
Hydrosulfide, or the hydrosulfide ion, is the anion HS− formed by deprotonation of hydrogen sulfide (H2S). In aqueous solution it represents the conjugate base of H2S and participates in acid–base equilibria that determine the relative proportions of H2S, HS−, and S2−, with pKa values around 7.0 and 12.9 at 25 °C.
HS− is a soft base and a relatively good nucleophile, readily forming metal sulfide precipitates such as
Industrially, hydrosulfide is produced by neutralizing hydrogen sulfide with base: H2S + OH− → HS− + H2O, or by
Safety considerations are important: hydrogen sulfide gas is highly toxic and flammable. Hydrosulfide salts release H2S