Bisulfide

Bisulfide(or Bisulphide in UK Enlgish spelling), also called hydrosulfide, refers the anion with the formula HS−, commonly written SH−. This species is the conjugate base of hydrogen sulfide:
 * H2S HS− + H+

In aqueous solutions, at pH less than 7, hydrogen sulfide is the dominant species; at pH > 7, bisulfide dominates.

A variety of salts are known, including sodium hydrosulfide, potassium hydrosulfide, and ammonium hydrosulfide. Some compounds described as salts of the sulfide dianion contain primarily hydrosulfide. For example, the hydrated form of sodium sulfide, nominally with the formula Na2S·(H2O)9, is better described as NaSH·NaOH·(H2O)8. Aqueous bisulfide absorbs light at around 230nm in the UV/VIS spectrum. Groups have used field spectrometers to measure the absorption due to bisulfide (and hence its concentration) continuously in the ocean and in sewage.

Bisulfide is sometimes confused with the disulfide dianion, S22−. Bisulfuro Bisulfida