Antimony pentasulfide
# Antimony pentasulfide

Antimony pentasulfide is an inorganic compound of antimony and sulfur, also known as antimony red. It is a nonstoichiometric compound with a variable composition. Its structure is unknown. Commercial samples are contaminated with sulfur, which may be removed by washing with carbon disulfide in a Soxhlet extractor.

## Production

Antimony pentasulfide can be produced by the reaction of antimony with sulfur at a temperature from 250 to 400 °C in an inert atmosphere.

## Uses

It may be used as a red pigment and is one possible precursor to Schlippe's salt, $Na_3SbS_4·9H_2O,$ which can be prepared according to the equation:

    3 $Na_2S$ + $Sb_2S_5$ + 9 $H_2O$ → 2 $Na_3SbS_4·9H_2O$

It is also used in the vulcanization of rubber to produce red rubber.

## Physical chemistry

Like many sulfides, this compound liberates hydrogen sulfide upon treatment with strong acids such as hydrochloric acid.

    6 HCl + $Sb_2S_5$ → 2 $SbCl_3$ + 3 $H_2S$ + 2 S

Analysis by Mössbauer spectroscopy indicates that this compound is a derivative antimony(III), explaining the production of antimony(III) chloride, rather than antimony(V) chloride, upon acidification. It is, therefore, not analogous to the phosphorus(V) compound phosphorus pentasulfide.

