Iron(III) sulfide, also known as ferric sulfide or sesquisulfide (), is one of the several binary iron sulfides. It is a solid, black powder that degrades at ambient temperature.
Reactions precipitates from solutions containing its respective ions: 2Fe3+ + 3S2− → Fe2S3 The resulting solid decays at a temperature over 20 °C into iron(II) sulfide (FeS) and elemental sulfur: The same products also form when Fe3+ reacts with sulfide ions in alkaline solutions. Fe2S3 → 2 FeS + S With hydrochloric acid it decays according to the following reaction equation:H. Roempp, Chemie (1997), S. 1099; Fe2S3 + 4 HCl → 2 FeCl2 + 2 H2S + S
Greigite Greigite, with the chemical formula , is a mixed valence compound containing both Fe(III) and Fe(II). It is the sulfur equivalent of the iron oxide magnetite (Fe3O4). As established by X-ray crystallography, the S anions form a cubic close-packed lattice, and the Fe cations occupy both tetrahedral and octahedral sites.Vaughan, D. J.; Craig, J. R. "Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. .
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