Ion+sulfide

Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is a chemical compound with the formula FeS. In practice, iron sulfides are often non-stoichiometric. Powdered iron sulfide is pyrophoric (i.e. will ignite spontaneously in air).


 * Forms of iron sulfide**

"Iron sulfide" exists in several distinct forms, which differ in the ratio of sulfur to iron and properties:[1]

Pyrrhotite, Fe1-xS, a mineral, which displays ferrimagnetism and crystallizes in monoclinic system. Iron metal shows ferromagnetism; iron sulfides do not. Troilite, FeS, a stoichiometric compound that adopts hexagonal symmetry. Mackinawite, Fe1+xS the least stable form of iron sulfide; mackinawite has a layered structure. Pyrite and marcasite, which are diamagnetic minerals, have the formula FeS2. Greigite (Fe3S4) a ferromagnetic species akin to magnetite (Fe3O4).




 * Chemical reactions**

Iron sulfide reacts with hydrochloric acid, releasing the pungent and very toxic hydrogen sulfide

FeS + 2 HCl → FeCl2 + H2S

FeS can be obtained by the heating of iron and sulfur:

Fe + S → FeS

Biology and biochemistry
As organic matter decays under low-oxygen (or [|hypoxic] ) conditions such as in swamps or [|dead zones] of lakes and oceans, [|sulfate-reducing bacteria] will use the [|sulfates] present in the water to oxidize the organic matter, producing [|hydrogen sulfide] as waste. Some of the hydrogen sulfide will react with metal ions in the water to produce metal sulfides, which are not water soluble. These metal sulfides, such as iron(II) sulfide, are often black or brown, leading to the color of sludge. Pyrrotite is a waste product of the // [|Desulfovibrio] // bacteria, a sulfate reducing bacteria. When eggs are cooked for a long time, the [|yolk] 's surface may turn green. This is due to iron(II) sulfide which forms as iron from the yolk meets hydrogen sulfide released from the egg white by the heat. [|[2]] This reaction occurs more rapidly in older eggs as the whites are more alkaline. [|[3]] 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 degradation of cysteine releases [|hydrogen sulfide] gas that reacts with the [|ferric] [|citrate] to produce ferrous sulfide.