is a chemical compound
with the formula FeS. In practice, iron sulfides are often non-stoichiometric
. Powdered iron sulfide is pyrophoric
FeS can be obtained by reacting iron and sulfur.
- S8(s) + 8Fe(s) → 8FeS(s)
Forms of iron sulfide
"Iron sulfide" exists in several distinct forms which differ in the stoichiometry
- Pyrrhotite, Fe1-xS, a mineral as well as the waste product of the Desulfovibrio bacteria, pyrrhotite displays ferrimagnetism and crystallizes in monoclinic system.
- Troilite, FeS, which has similar material to pyrrhotite, but does not possess ferromagnetic properties due to stoichiometric composition and crystallizes in hexagonal system.
- Mackinawite, Fe1+xS (often written as (Fe,Ni)9S8), the least stable from of iron sulfide, mackinawite has a layered structure.
- Pyrite, mineral form of the iron disulfide (FeS2) with a gold-like appearance, making it also known as "fool's gold" (the related mineral is marcasite).
- Keilite (Fe,Mg)S was recently found in a meteorite.
Certain chemical principles are nicely illustrated using the chemistry of iron sulfides.
The methods of chemical composition
can be shown by the production of iron(II) sulfide from iron
(see equation above).
- FeS(s) + 2HCl(aq) → FeCl2 (aq) + H2S(g)
Biological and biochemical uses
The presence of ferrous sulfide as a visible black precipitate in the growth medium peptone
iron agar can be used to distinguish between microorganisms
that produce the cysteine metabolizing
enzyme cysteine desulfhydrase
and those that do not. Peptone iron agar contains the amino acid cysteine
and a chemical indicator, ferric citrate
. The catalysis
of cysteine releases hydrogen sulfide
gas that reacts with the ferric citrate to produce ferrous sulfide.
- D. Vaughan, J. Craig, (1978) Mineral Chemistry of Metal Sulfides, Cambridge University Press. ISBN 0-521-21489-0