Cobalt sulfide

Cobalt sulfide

Identifiers
CAS Number	1317-42-6 Y
PubChem	14832
RTECS number	GG332500
Properties
Chemical formula	CoS (varied)
Molar mass	90.9982 g/mol
Appearance	black solid (alpha) grayish-red crystals (beta)
Density	5.45 g/cm3
Melting point	1195 °C
Solubility in water	0.00038 g/100 mL (18 °C)
Solubility	slightly soluble in acid
Structure
Crystal structure	octahedral (beta)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cobalt sulfide is the name for chemical compounds with a formula Co_xS_y. Well-characterized species include minerals with the formula CoS₂ and Co₃S₄, and the synthetic material Co₉S₈. In combination with molybdenum, the sulfides of cobalt are used as catalysts for the industrial process called hydrodesulfurization, which is implemented on a large scale in refineries.

Cobalt sulfides precipitate when aqueous solutions of cobalt(II) ions are treated with hydrogen sulfide. This reaction is useful in the purification of cobalt from its ores as well as in qualitative inorganic analysis. In general, the sulfides of cobalt are black, semiconducting, insoluble in water, and nonstoichiometric. They react with strong acids to release hydrogen sulfide gas again. They are weak reducing agents and can be oxidized to cobalt sulfate.

Cobalt sulfide exists in two forms: alpha and beta.

Minerals

The best defined sulfides of cobalt occur as minerals. The rare mineral cattierite has the stoichiometry CoS₂. It is isostructural with iron pyrite, featuring disulfide groups, i.e. Co²⁺S₂²⁻. Linnaeite, also rare, has the formula Co₃S₄ and crystallizes in the spinel motif.

References

• Cobalt sulfide, NIST Webbook