|Molecular formula||CoS (varied)|
|Molar mass||90.9982 g/mol|
|Appearance||black solid (alpha)
grayish-red crystals (beta)
|Melting point||1195 °C|
|Solubility in water||0.00038 g/100 mL (18 °C)|
|Solubility||slightly soluble in acid|
|Crystal structure||octahedral (beta)|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Cobalt sulfide is the name for chemical compounds with a formula CoxSy. 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.
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.
- Cobalt sulfide, NIST Webbook
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