Iron(II) sulfide, also popular as iron sulfide or ferrous sulfide, is an inorganic, water-insoluble compound represented by the chemical formula FeS ^{[1, 2]}. In IUPAC nomenclature, it is called sulfanylideneiron ^[1]. It naturally occurs as the minerals troilite and pyrrhotite ^[3]. FeS has the nickel arsenide structure, with trigonal prismatic sulfides and octahedral iron centers ^[5].

Iron(II) Sulfide Identification
CAS Number	1317-37-9 [1]
PubChem CID	14828 [1]
ChemSpider ID	8466211 [2]
EC Number	215-268-6 [1]
MDL Number	MFCD00011013 [1]
InChI Key	MBMLMWLHJBBADN-UHFFFAOYSA-N [1]

Iron(II) Sulfide Composition and Synthesis

When iron and sulfur are mixed and heated in a test tube, it undergoes an exothermic reaction to produce iron(ii) sulfide ^[6].

Fe + S → FeS

Reaction with Hydrochloric Acid

Iron sulfide reacts with hydrochloric acid to yield ferrous chloride and hydrogen sulfide, as indicated by the following reaction:

FeS + 2 HCl → FeCl₂ + H₂S

Properties and Characteristics of Iron(II) Sulfide

General Properties
Molar Mass/Molecular Weight	87.905 g/mol [1]
Physical Properties
Color and Appearance	Gray to brownish-black rods, lumps, or granular powder, colorless when pure [1]
Odor	Odorless [8]
Melting Point	1194 °C, 2181 °F [1]
Boiling Point	Decomposes [1]
Density	4.75 g cm-3 [1]
State of matter at room temperature	Solid [1]
Solubility	Reacts in acids with the production of hydrogen sulfide, insoluble in nitric acid [1]
Solubility in Water	0.00062 g/100 cc at 18 °C [1]
Magnetic Susceptibility (χ)	1074 X 10-6 cm3/mol
Atomic Properties
Crystal Structure	Octahedral

Uses

• As a pigment in ceramics, hair dyes, and glass containers ^{[1, 7]}.
• Treating exhaust gases and lessening heavy metal pollution ^[1].
• To synthesize hydrogen sulfide in the laboratory ^[1].

Is It Safe

Iron sulfide can cause irritation to your skin, eyes, lungs, and gastrointestinal tract when inhaled [1]. It is known to cause slight toxicity upon ingestion ^[8].

References
1. Ferrous Sulfide – Pubchem.ncbi.nlm.nih.gov
2. Iron(II) Sulfide – Chemspider.com
3. Ferrous Sulfide – Chemicalbook.com
4. Iron(II) Sulfide – Americanelements.com
5. Structures Related to NaCl and NiAs – Chem.libretexts.org
6. Iron and Sulfur Reaction – Rsc.org
7. Iron(II) Sulfide – Hazmap.nlm.nih.gov
8. Iron(II) Sulfide – Mccsd.net