Iron(III) sulfide explained

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⁺ + 3S^2- → Fe₂S₃The resulting solid decays at a temperature over 20 °C into iron(II) sulfide (FeS) and elemental sulfur:^[1]

Fe₂S₃ → 2 FeS + SWith hydrochloric acid it decays according to the following reaction equation:^[2]

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.^[3]

Notes and References

1. Book: Holleman, Wiberg . Inorganic Chemistry . 2001 . 1451 . 0-12-352651-5.
2. H. Roempp, Chemie (1997), S. 1099;
3. Vaughan, D. J.; Craig, J. R. "Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. .