Cobalt sulfide

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Cobalt sulfide
Sulfid kobaltnatý.PNG
Identifiers
CAS number 1317-42-6 YesY
PubChem 14832
RTECS number GG332500
Properties
Molecular 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)
Except where noted otherwise, 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 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[citation needed].

Cobalt sulfide exists in two forms: alpha and beta.

Minerals[edit]

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.[1]

References[edit]

  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. ISBN 0-08-022057-6.