Iron(II) sulfide 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 and properties:
- 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.
Pedagogical uses
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 and
sulfur (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.
See also
References
- D. Vaughan, J. Craig, (1978) Mineral Chemistry of Metal Sulfides, Cambridge University Press. ISBN 0-521-21489-0
