Antimony trisulfide (Sb₂S₃) is found in nature as the crystalline mineral stibnite and the amorphous red mineral (actually a mineraloid) metastibnite. It is manufactured for use in safety matches, military ammunition, explosives and fireworks. It also is used in the production of ruby-colored glass and in plastics as a flame retardant. Historically the stibnite form was used as a grey pigment in paintings produced in the 16th century. In 1817, the dye and fabric chemist, John Mercer discovered the non-stoichiometric compound Antimony Orange (approximate formula2 Sb2S3•Sb2O3), the first good orange pigment available for cotton fabric printing. Antimony trisulfide was also used as the image sensitive photoconductor in vidicon camera tubes. It is a semiconductor with a direct band gap of 1.8–2.5 eV. With suitable doping, p and n type materials can be produced.

Preparation and reactions

Sb₂S₃ can be prepared from the elements at temperature 500–900 °C: :2 Sb + 3 S → Sb₂S₃ Sb₂S₃ is precipitated when H₂S is passed through an acidified solution of Sb(III). This reaction has been used as a gravimetric method for determining antimony, bubbling H₂S through a solution of Sb(III) compound in hot HCl deposits an orange form of Sb₂S₃ which turns black under the reaction conditions.A.I. Vogel, (1951), Quantitative Inorganic analysis, (2d edition), Longmans Green and Co Sb₂S₃ is readily oxidised, reacting vigorously with oxidising agents. It burns in air with a blue flame. It reacts with incandescence with cadmium, magnesium and zinc chlorates. Mixtures of Sb₂S₃ and chlorates may explode. In the extraction of antimony from antimony ores the alkaline sulfide process is employed where Sb₂S₃ reacts to form thioantimonate(III) salts (also called thioantimonite): :3 Na₂S + Sb₂S₃ → 2 Na₃SbS₃ A number of salts containing different thioantimonate(III) ions can be prepared from Sb₂S₃ these include: : bS₃sup>3−, bS₂sup>−, b₂S₅sup>4−, b₄S₉sup>6−, b₄S₇sup>2− and b₈S₁₇sup>10− " Schlippe's salt", Na₃SbS₄·9H₂O, a thioantimonate(V) salt is formed when Sb₂S₃ is boiled with sulfur and sodium hydroxide. The reaction can be represented as: :Sb₂S₃ + 3 S²⁻ + 2 S → 2 bS₄sup>3−

Structure

The structure of the black needle-like form of Sb₂S₃, stibnite, consists of linked ribbons in which antimony atoms are in two different coordination environments, trigonal pyramidal and square pyramidal. Similar ribbons occur in Bi₂S₃ and Sb₂Se₃. The red form, metastibnite, is amorphous. Recent work suggests that there are a number of closely related temperature dependent structures of stibnite which have been termed stibnite (I) the high temperature form, identified previously, stibnite (II) and stibnite (III). Other paper shows that the actual coordination polyhedra of antimony are in fact SbS₇, with (3+4) coordination at the M1 site and (5+2) at the M2 site. These coordinations consider the presence of secondary bonds. Some of the secondary bonds impart cohesion and are connected with packing.

References

{{Sulfides Antimony(III) compounds Sulfides