Chemical elements
  Iron
    History of Iron
    Mineralogy
    Isotopes
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    Application
    Physical Properties
    Chemical Properties
      Iron Hydride
      Ferrous fluoride
      Aluminium pentafluoferrite
      Ferric fluoride
      Ammonium ferrifluoride
      Barium ferrifluoride
      Potassium ferrifluoride
      Sodium ferrifluoride
      Thallous ferrifluoride
      Ferrous diferrifluoride
      Ferrous monoferrifluoride
      Ferrous chloride
      Ammonium tetrachlorferrite
      Ferric chloride
      Tetrachlorferrates
      Pentachlorferrates
      Ferroso-ferric chloride
      Ferrous perchlorate
      Ferric perchlorate
      Ferrous chlorate
      Ferric chlorate
      Ferrous Oxychlorides
      Ferrous bromide
      Ferric bromide
      Ferric chloro-bromide
      Ferrous bromate
      Ferrous iodide
      Ferric iodide
      Ferric iodate
      Ferrous oxide
      Ferrous hydroxide
      Triferric tetroxide
      Ferric oxide
      Ferrous acid
      Calcium ferrite
      Cobalt ferrite
      Cupric ferrite
      Cuprous ferrite
      Magnesium ferrite
      Nickel ferrite
      Potassium ferrite
      Sodium ferrite
      Zinc ferrite
      Barium ferrate
      Strontium ferrate
      Barium perferrate
      Calcium perferrate
      Potassium perferrate
      Sodium perferrate
      Strontium perferrate
      Iron Subsulphides
      Ferrous sulphide
      Ferric sulphide
      Potassium ferric sulphide
      Sodium ferric sulphide
      Cuprous ferric sulphide
      Iron disulphide
      Ferrous sulphite
      Ferric sulphite
      Potassium ferri-tetrasulphite
      Potassium ferri-disulphite
      Potassium ferri-sulphite
      Ammonium ferri-sulphite
      Sodium ferri-disulphite
      Sodium hydrogen ferri-tetrasulphite
      Ferrous sulphate
      Ferrous copper sulphate Fe
      Ferrous ammonium sulphate
      Ferrous potassium sulphate
      Ferrous aluminium sulphate
      Basic ferrous sulphate
      Ferric sulphate
      Ammonium ferri-disulphate
      Trisodium ferri-trisulphate
      Ferric Alums
      Ferric ammonium alum
      Ferric potassium alum
      Ferric rubidium alum
      Ferroso-ferric sulphate
      Ferrous amido-sulphonate
      Ferric amido-sulphonate
      Ferrous thiosulphate
      Ferrous pyrosulphate
      Ferrous tetrathionate
      Ferric selenide
      Iron diselenide
      Iron Selenites
      Ferrous selenate
      Ferric rubidium selenium alum
      Ferric caesium selenium alum
      Ferric tellurite
      Ferrous chromite
      Ferrous chromate
      Iron nitride
      Nitro-Iron
      Ferrous nitrate
      Ferric nitrate
      Ferrous Nitroso Salts
      Potassium ferro-heptanitroso sulphide
      Sodium ferro-heptanitroso sulphide
      Ammonium ferro-heptanitroso sulphide
      Tetramethyl ammonium ferro-heptanitroso sulphide
      Ferro-dinitroso Sulphides
      Potassium ferro-dinitroso thiosulphate
      Triferro phosphide
      Diferro phosphide
      Iron monophosphide
      Iron sesqui-phosphide
      Ferrous hypophosphite
      Ferric hypophosphite
      Ferrous phosphite
      Ferric phosphite
      Ferrous orthophosphate
      Ferrous hydrogen orthophosphate
      Ferrous dihydrogen orthophosphate
      Ferric orthophosphate
      Sodium ferri-diorthophosphate
      Ammonium ferri-diorthophosphate
      Sodium ferri-triorthophosphate
      Ferric dihydrogen orthophosphate
      Acid ferric orthophosphate
      Ferrous metaphosphate
      Ferric metaphosphate
      Ferrous pyrophosphate
      Ferric pyrophosphate
      Hydrogen ferri-pyrophosphate
      Sodium ferro-pyrophosphate
      Ferrous thio-orthophosphite
      Ferrous thio-orthophosphate
      Ferrous thio-pyrophosphite
      Ferrous thio-pyrophosphate
      Iron sub-arsenide
      Iron mon-arsenide
      Iron sesqui-arsenide
      Iron di-arsenide
      Iron thio-arsenide
      Ferrous met-arsenite
      Ferric arsenite
      Ferrous ortho-arsenate
      Ferric ortho-arsenate
      Ferro mono-antimonide
      The di-antimonide
      Ferrous thio-antimonite
      Ferric ortho-antimonate
      Triferro carbide
      Diferro carbide
      Iron dicarbide
      Iron pentacarbonyl
      Diferro nonacarbonyl
      Iron tetracarbonyl
      Ferrous carbonate
      Ferrous bicarbonate
      Ferrous potassium carbonate
      Complex Iron Carbonates
      Ferrous thiocarbonate
      Ferrous thiocarbonate hexammoniate
      Ferrous cyanide
      Ferro-cyanic acid
      Aluminium ferrocyanide
      Aluminium ammonium ferrocyanide
      Ammonium ferrocyanide
      Barium ferrocyanide
      Calcium ferrocyanide
      Calcium ammonium ferrocyanide
      Cobalt ferrocyanide
      Copper ferrocyanide
      Ammonium cuproferrocyanide
      Barium cuproferrocyanide
      Lithium cuproferrocyanide
      Magnesium cuproferrocyanide
      Potassium cuproferrocyanide
      Sodium cuproferrocyanide
      Ammonium cupriferrocyanide
      Potassium cupriferrocyanide
      Potassium ferrous cupriferrocyanide
      Sodium cupriferrocyanide
      Strontium cupriferrocyanide
      Lithium ferrocyanide
      Magnesium ferrocyanide
      Magnesium ammonium ferrocyanide
      Manganese ferrocyanide
      Nickel ferrocyanide
      Potassium ferrocyanide
      Potassium aluminium ferrocyanide
      Potassium barium ferrocyanide
      Potassium calcium ferrocyanide
      Potassium cerium ferrocyanide
      Potassium magnesium ferrocyanide
      Potassium mercuric ferrocyanide
      Silver ferrocyanide
      Sodium ferrocyanide
      Sodium cerium ferrocyanide
      Strontium ferrocyanide
      Thallium ferrocyanide
      Zinc potassium ferrocyanide
      Ferricyanic acid
      Ammonium ferricyanide
      Barium ferricyanide
      Barium potassium ferricyanide
      Calcium ferricyanide
      Calcium potassium ferricyanide
      Cobalt ferricyanide
      Copper ferricyanide
      Lead ferricyanide
      Magnesium ferricyanide
      Mercuric ferricyanide
      Mercurous ferricyanide
      Potassium ferricyanide
      Sodium ferricyanide
      Strontium ferricyanide
      Zinc ferricyanide
      Ferrous hydrogen ferrocyanide
      Ferrous potassium ferrocyanide
      Prussian Blues
      Ferrous ferrocyanide
      Ferric ammonium ferrocyanide
      Nitroprussic acid
      Sodium nitroprusside
      Ammonium nitroprusside
      Barium nitroprusside
      Cobalt nitroprusside
      Nickel nitroprusside
      Potassium nitroprusside
      Carbonyl Penta-Ferrocyanides
      Carbonyl ferrocyanic acid
      Barium carbonyl ferrocyanide
      Copper carbonyl ferrocyanide
      Ferric carbonyl ferrocyanide
      Potassium carbonyl ferrocyanide
      Silver carbonyl ferrocyanide
      Sodium carbonyl ferrocyanide
      Strontium carbonyl ferrocyanide
      Uranyl carbonyl ferrocyanide
      Sodium ammonio ferrocyanide
      Potassium aquo ferrocyanide
      Potassium aquo ferricyanide
      Sodium aquo penta-ferricyanide
      Potassium sulphito ferrocyanide
      Ferrous thiocyanate
      Ferric thiocyanate
      Sodium ferrothiocyanate
      Sodium ferrithiocyanate
      Potassium ferrithiocyanate
      Iron subsilicide
      Iron monosilicide
      Iron disilicide
      Triferro disilicide
      Ferrous orthosilicate
      Ferrous magnesium orthosilicate
      Ferrous metasilicate
      Ferric silicate
      Diferro boride
      Iron monoboride
      Iron diboride
      Ferrous chlorborate
      Ferrous bromborate
    Corrosion
    Iron Salts
    PDB 101m-1aeb
    PDB 1aed-1awd
    PDB 1awp-1beq
    PDB 1bes-1c53
    PDB 1c6o-1ci6
    PDB 1cie-1cry
    PDB 1csu-1dfx
    PDB 1dgb-1dry
    PDB 1ds1-1e08
    PDB 1e0z-1ehj
    PDB 1ehk-1f5o
    PDB 1f5p-1fnp
    PDB 1fnq-1fzi
    PDB 1g08-1gnl
    PDB 1gnt-1h43
    PDB 1h44-1hdb
    PDB 1hds-1i5u
    PDB 1i6d-1iwh
    PDB 1iwi-1jgx
    PDB 1jgy-1k2o
    PDB 1k2r-1kw6
    PDB 1kw8-1lj0
    PDB 1lj1-1m2m
    PDB 1m34-1mko
    PDB 1mkq-1mun
    PDB 1muy-1n9x
    PDB 1naz-1nx4
    PDB 1nx7-1ofe
    PDB 1off-1p3t
    PDB 1p3u-1pmb
    PDB 1po3-1qmq
    PDB 1qn0-1ra0
    PDB 1ra5-1rxg
    PDB 1ry5-1smi
    PDB 1smj-1t71
    PDB 1t85-1u8v
    PDB 1u9m-1uyu
    PDB 1uzr-1vxf
    PDB 1vxg-1wri
    PDB 1wtf-1xlq
    PDB 1xm8-1y4r
    PDB 1y4t-1ygd
    PDB 1yge-1z01
    PDB 1z02-2a9e
    PDB 2aa1-2azq
    PDB 2b0z-2boz
    PDB 2bpb-2ca3
    PDB 2ca4-2cz7
    PDB 2czs-2dyr
    PDB 2dys-2ewk
    PDB 2ewu-2fwl
    PDB 2fwt-2gl3
    PDB 2gln-2hhb
    PDB 2hhd-2ibn
    PDB 2ibz-2jb8
    PDB 2jbl-2mgh
    PDB 2mgi-2o01
    PDB 2o08-2ozy
    PDB 2p0b-2q0i
    PDB 2q0j-2r1h
    PDB 2r1k-2spm
    PDB 2spn-2vbd
    PDB 2vbp-2vzb
    PDB 2vzm-2wiv
    PDB 2wiy-2xj5
    PDB 2xj6-2ylj
    PDB 2yrs-2zon
    PDB 2zoo-3a17
    PDB 3a18-3aes
    PDB 3aet-3bnd
    PDB 3bne-3cir
    PDB 3ciu-3dax
    PDB 3dbg-3e1p
    PDB 3e1q-3eh4
    PDB 3eh5-3fll
    PDB 3fm1-3gas
    PDB 3gb4-3h57
    PDB 3h58-3hrw
    PDB 3hsn-3ir6
    PDB 3ir7-3k9y
    PDB 3k9z-3l4p
    PDB 3l61-3lxi
    PDB 3lyq-3mm8
    PDB 3mm9-3n62
    PDB 3n63-3nlo
    PDB 3nlp-3o0f
    PDB 3o0r-3p6o
    PDB 3p6p-3prq
    PDB 3prr-3sel
    PDB 3sik-3una
    PDB 3unc-4blc
    PDB 4cat-4erg
    PDB 4erm-4nse
    PDB 4pah-8cat
    PDB 8cpp-9nse

Ferrous sulphide, FeS






Ferrous sulphide, FeS, occurs in nature as the mineral troilite, which is found in nodules in the majority of meteorites containing iron. When crystalline it appears to belong to the hexagonal system, and has probably been formed in the presence of excess of iron. It may be obtained by the direct union of iron and sulphur at red heat. If the iron is in the form of filings and is intimately mixed with the sulphur, the mass becomes incandescent when once the reaction has been started. Synthetic iron disulphide, heated above 700° C., is converted into ferrous sulphide.

When iron pyrites, FeS2, is heated to bright redness in the absence of air or in hydrogen, it yields ferrous sulphide. In crystalline form ferrous sulphide is produced by passing hydrogen sulphide over ferrous oxide at high temperatures or over metallic iron at dull red heat.

If iron wire is used exposed in a bundle to the hydrogen sulphide, it readily becomes encrusted with tiny crystals, silver-white in appearance when first prepared. The crystals are regarded as belonging to the hexagonal system.

The same reaction appears to take place at the ordinary temperature when iron and sulphur are brought into contact under enormous pressures, namely of the order of 6500 atmospheres. The product resembles ordinary ferrous sulphide in that it is homogeneous under the microscope, and evolves a continuous stream of hydrogen sulphide when immersed in dilute sulphuric acid.

Ferrous sulphide has a bluish black appearance, reminiscent of that of magnetic oxide, but it is not magnetic. Density 4.67. It is stable when heated in hydrogen or in the absence of air, but when heated in air it readily oxidises to ferrous sulphate, whilst at red heat all the sulphur is expelled, red ferric oxide remaining.

When exposed to steam at red heat ferrous sulphide is decomposed, yielding hydrogen, hydrogen sulphide, and ferroso-ferric oxide. Thus: -

3FeS + 4H2O = Fe3O4 + 3H2S + H2.

At higher temperatures sulphur dioxide and sulphur are also formed.

When heated in a current of chlorine, ferric chloride and sulphur chloride distil over.

When heated in a sealed tube at 150° to 200° C. with thionyl chloride, ferrous sulphide is oxidised to ferric chloride. Thus: -

6FeS + 16SOCl2 = 6FeCl3 + 8SO2 + 7S2Cl2.

Ferrous sulphide is reduced when heated with manganese, yielding metallic iron: -

FeS + Mn = MnS + Fe,

the reaction being exothermic. This reaction is of great practical importance in connection with the desulphurisation of steel. Liquid ferrous sulphide freezes at 1171° C., and melts at 1187° C. The heat of formation of ferrous sulphide from iron and sulphur has been determined as: -

[Fe] + [S] = [FeS] + 23,070 calories.
[Fe] + [S] = [FeS] + 18,800 calories.

When heated to about 130° C., both ordinary commercial ferrous sulphide and meteoric troilite undergo a polymorphic change, and, on cooling, a break in the cooling curve is observed at this point. Synthetic ferrous sulphide which does not contain any excess of free iron exhibits no such break, although with 7 per cent, of free iron the transition point is very marked at 138° C., and further addition of iron does not change it. It appears, therefore, that the excess of iron catalytically assists the change in the case of synthetic ferrous sulphide. Troilite, on the other hand, does not contain excess of iron, but possibly its carbon content behaves catalytically in an analogous manner. Ferrous sulphide, stable at ordinary temperatures, is thus known as the a variety, that above 130° C. being termed the β variety. When heated to 298° C. a second polymorphic transformation occurs.

As ordinarily prepared, ferrous sulphide readily dissolves in dilute sulphuric or hydrochloric acid, evolving hydrogen sulphide - a reaction that affords a convenient laboratory method of preparing the gas. When pure, however, ferrous sulphide dissolves extremely slowly in the cold acids. The presence of free iron acts as an accelerator of the reaction, the nascent hydrogen produced by its solution in acid effecting the reduction of the adjacent particles of ferrous sulphide to hydrogen sulphide and metallic iron.


Hydrated ferrous sulphide, FeSAq

Hydrated ferrous sulphide, FeS.Aq., is readily obtained as a bulky black precipitate on adding an alkali sulphide to a solution of a ferrous salt. If a ferric salt is employed, it is reduced to the ferrous condition with simultaneous precipitation of sulphur. Thus: -

FeCl2 + (NH4)2S = FeS + 2NH4Cl, 2FeCl3 + 3(NH4)2S = 2FeS + 6NH4Cl + S.

Hydrated ferrous sulphide is slightly soluble in water, yielding a greenish solution. From electric conductivity measurements its solubility has been calculated as 70.1×10-6 gram-molecules per litre.

Ferrous sulphide is insoluble in aqueous caustic soda or potash, although the mixture of ferrous sulphide and sulphur formed on adding ammonium sulphide to ferric chloride yields a dark green solution.

Addition of dilute acid causes the evolution of hydrogen sulphide, a ferrous salt passing into solution. For this reason ferrous sulphide cannot be completely precipitated by passage of hydrogen sulphide through a neutral solution of a ferrous salt of a mineral acid, as the reaction is reversible, according to the equation: -

FeX + H2SFeS + H2X.

In acid solution - for example, sulphuric acid - no precipitate is obtained unless the pressure of the hydrogen sulphide is increased. The greater the concentration of the acid the higher must be the pressure of the hydrogen sulphide.

Ferrous sulphide may, however, be precipitated from solutions of ferrous salts in the presence of sodium acetate - a fact that was known to Gay-Lussac - and even from ferrous acetate in the presence of acetic acid, and from solutions of iron in citric or succinic acids.

Ferrous sulphide is oxidised by acidulated hydrogen peroxide solution, yielding ferric sulphate or hydrolysed products of this salt. With ammoniacal zinc chloride no reaction occurs at the ordinary temperature, but at 160° to 170° C. in a sealed tube ferrous hydroxide and zinc sulphide are produced.

Ferrous sulphide unites with other metallic sulphides to form stable double compounds. Many of these occur in nature as minerals, a few of the more important being pyrrhotite or magnetic pyrites, 5FeS.Fe2S3; Pentlandite, 2FeS.NiS; marmatite, FeS.4ZnS; and Daubreelite, FeS.Cr2S3.

These and other more or less stable sulphides have been prepared in the laboratory. Thus 3FeS.2MnS is formed when ferrous and manganous sulphides are fused together. It melts at 1362° C., and forms solid solutions in all proportions with manganous sulphide.

FeS.Cr2S3 results on heating a mixture of iron, chromium hydroxide, and sulphur, as a black insoluble compound.

FeS.Al2S3 results when ferrous sulphide or pyrites is reduced with metallic aluminium. Thus: -

4FeS + 2Al = FeS.Al2S3 + 3Fe,
and 2FeS2 + 2Al = FeS.Al2S3 + Fe.

On melting gold and iron together in the presence of sulphur, FeS.Au2S is obtained.

A study of the freezing-point curves for mixtures of ferrous and cuprous sulphides appears to indicate the existence of three compounds, namely: -

2Cu2S.FeS, which is stable at all temperatures below the freezing- point;

3Cu2S.2FeS, which undergoes a change at 180° to 230° C., metallic copper being set free, and a product rich in sulphur remaining; 2Cu2S.5FeS, which breaks up into the first compound and free ferrous sulphide at temperatures between 500° and 600° C.

On calcining sodium thiosulphate with ferrous oxalate, Na2S.2FeS is obtained as bronze-coloured prisms. The corresponding potassium compound, K2S.2FeS, is formed on reducing potassium ferric sulphide, K2S.Fe2S3, with hydrogen; or by heating iron (1 part) with sulphur (5 parts) and potassium carbonate (5 parts). It yields needle-shaped crystals or thick tablets, resembling potassium permanganate in appearance.

Ferrous thio-antimonite, 3FeS.Sb2S3, or Fe3Sb2S6, is obtained on precipitation of a ferrous salt with potassium thio-antimonite.
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