Sodium thioantimoniate

Sodium thioantimoniate or sodium tetrathioantimonate(V) is an inorganic compound with the formula Na3SbS4. The nonahydrate of this chemical, Na3SbS4*9H2O, is known as Schlippe's salt, named after Johann Karl Friedrich von Schlippe (1799–1867). These compounds are examples of sulfosalts. They were once of interest as species generated in qualitative inorganic analysis.

Structure
The nonahydrate consists of the tetrahedral tetrathioantimonate(V) anions SbS4(3−) and sodium cations Na+, which are hydrated. The Sb-S distance is 2.33 Å. Related salts are known for different cations including ammonium and potassium.

The anhydrous salt is a polymer with tetrahedral Na and Sb sites.

Preparation
Sodium tetrathioantimonate nonahydrate is prepared by the reaction of "antimony trisulfide", elemental sulfur, and aqueous sulfide source.
 * 3 Na2S + 2 S + Sb2S3 + 18 H2O → 2 Na3SbS4*9H2O

The Na2S can be generated in situ by the reaction of sodium hydroxide and S (co-generating sodium sulfate):
 * Sb2S3 + 8 NaOH + 6 S → 2 Na3SbS4 + Na2SO4 + 4 H2O

Charcoal can also be used to reduce the sulfur.

The required antimony trisulfide is prepared by treatment of Sb(III) compounds with sulfide sources:
 * 2 SbCl3 + 3 H2S → Sb2S3 + 6 HCl

Reactions
The hydrate dissolves in water to give the tetrahedral SbS4(3−) ion. The salt gives antimony pentasulfide upon acidification:
 * 2 Na3SbS4 + 6 HCl → Sb2S5 + 6 NaCl + 3 H2S