Antimony Trisulfide

Antimony trisulfide () 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 is also used as friction materials in break lining. It is very important critical primer material for military applications and tracer bullets. 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 formula ), 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

can be prepared from the elements at temperature 500–900 °C:

:

is precipitated when is passed through an acidified solution of Sb(III). This reaction has been used as a gravimetric method for determining antimony, bubbling through a solution of Sb(III) compound in hot HCl deposits an orange form of which turns black under the reaction conditions.A.I. Vogel, (1951), Quantitative Inorganic analysis, (2d edition), Longmans Green and Co

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 and chlorates may explode.

In the extraction of antimony from antimony ores the alkaline sulfide process is employed where reacts to form thioantimonate(III) salts (also called thioantimonite):
:

A number of salts containing different thioantimonate(III) ions can be prepared from . These include:
:

Schlippe's salt, , a thioantimonate(V) salt is formed when is boiled with sulfur and sodium hydroxide. The reaction can be represented as:
:

Structure

The structure of the black needle-like form of , stibnite, consists of linked ribbons in which antimony atoms are in two different coordination environments, trigonal pyramidal and square pyramidal. Similar ribbons occur in and . 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 , 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
Sesquisulfides
Pyrotechnic fuels