Iron(iii) sulfide also called ferric sulfide or iron sesquisulfide is one of the members of iron(3+) sulfides with IUPAC name iron(3+) trisulfide and chemical formula Fe₂S₃ ^{[1, 2]}. It is a relatively unstable artificial black solid that decomposes and turns into a yellow-green powder at room temperature ^[2].

Iron(III) Sulfide Identification
CAS Number	12063-27-3 [1]
PubChem CID	160957 [1]
ChemSpider ID	141408 [3]
EC Number	234-367-5 [1]
ChEBI ID	CHEBI:75899 [2]
InChI Key	KAEAMHPPLLJBKF-UHFFFAOYSA-N [1]

Composition and Synthesis

It is produced by the addition of cooled iron(iii) chloride solution to refrigerated sodium sulfide solution, as represented by the following equation:

2FeCl₃ + 3Na₂S → Fe₂S₃ + 6NaCl

It can also be synthesized as a by-product of desulfurization of hydrogen sulfide gas that is passed through hydrated iron(iii) oxide:

Fe₂O₃ + 3H₂S + H₂O → Fe₂S₃ + 4H₂O

 

Reaction with Hydrogen Chloride

It undergoes a decomposition reaction when combined with hydrochloric acid ^[4]:

Fe₂S₃ + 4HCl → 2FeCl₂ + 2H₂S + S

Properties and Characteristics of Iron(III) Sulfide

General Properties
Molar Mass/Molecular Weight	207.87 g/mol [1]
Physical Properties
Color and Appearance	Turns into yellowish-green powder at room temperature [5]
Melting Point	Decomposes
Boiling Point	N/A [5]
Density	4.3 g cm-3 [5]
State of matter at room temperature	Solid [1]
Solubility	Moderately soluble in acids
Solubility in Water	Very slightly soluble in water [1]

Use

As a source of sulfur and iron(ii) sulfide during the decay of ferric sulfide at room temperature (about 20 °C).

References
1. Iron Sesquisulfide – Homework.study.com
2. CHEBI:75899 – Iron(3+) Sulfide – Ebi.ac.uk
3. Iron(3+) Sulfide (2:3) – Chemspider.com
4. Chemical Equation Balancer – Chemicalaid.com
5. Ferric Sulfide – Americanelements.com