Arsenic, antimony and bismuth sulfides

Arsenic and antimony sulfide ores are major sources of the group 15 elements (see Section 14.2). In the laboratory, AS2S3 and AS2S5 are usually precipitated from aqueous solutions of arsenite or arsenate. Reaction 14.144 proceeds when the H2S is passed slowly through the solution at 298 K. If the temperature is lowered to 273 K and the rate of flow of H2S is increased, the product is AS2S5. 

The only well-characterized binary sulfide of Sb is the naturally occurring Sb2S3 (stibnite), which has a doublechain structure in which each Sb(III) is pyramidally sited with respect to three S atoms. The sulfide can be made by direct combination of the elements. A metastable red form can be precipitated from aqueous solution, but reverts to the stable black form on heating. Like AS2S3, Sb2S3 dissolves in alkali metal sulfide solutions (see eq. 15.156). Bismuth(III) sulfide, 61283, is isostructural with Sb2S3, but in contrast to its As and Sb analogues, 61283 does not dissolve in alkali metal sulfide solutions. 

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