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| Iron(II) sulfate | |
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-sulfate-heptahydrate-sample.jpg) |
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| Other names | ferrous sulphate; green vitriol; iron vitriol; copperas; melanterite; szomolnokite |
| Identifiers | |
| CAS number | [7720-78-7] |
| Properties | |
| Molecular formula | FeSO4·H2O; FeSO4·4H2O; FeSO4·5H2O; FeSO4·7H2O |
| Molar mass | 151.908 g/mol (anhydrous); 169.923 g/mol (monohydrate); 224.120 g/mol (tetrahydrate); 242.135 g/mol (pentahydrate); 278.05 g/mol (heptahydrate) |
| Appearance | blue/green or white crystals |
| Density | 1.898 g/cm³ |
| Melting point |
64°C |
| Boiling point |
90°C (becomes FeSO4·H2O) |
| Solubility in other solvents | Soluble |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Iron(II) sulfate or ferrous sulfate is the chemical compound with the formula (FeSO4). It is most commonly encountered as the blue-green heptahydrate. Known since ancient times as copperas, the alchemical symbol for iron (II) sulfate is represented by unicode symbol U+26A8: ⚨.[1]
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Hydrates
Iron(II) sulfate can be found in various states of hydration, and several of these forms exist in nature.
- FeSO4·H2O (mineral: szomolnokite, relatively rare)
- FeSO4·4H2O (mineral: rozenite, white, relatively common, may be dehydratation product of melanterite)
- FeSO4·5H2O (mineral: siderotil, relatively rare)
- FeSO4·6H2O (mineral: ferrohexahydrite, relatively rare)
- FeSO4·7H2O (mineral: melanterite, blue, relatively common)
At 90°C, the heptahydrate loses water to form the colorless monohydrate, also called green vitriol or copperas. In its anhydrous, crystalline state, its standard enthalpy of formation is ΔfH°solid = -928.4 kJ.mol-1 and its standard molar entropy is S°solid = 107.5 J.K-1.mol-1. All mentioned mineral forms are connected with oxidation zones of Fe-bearing (pyrite, marcasite, chalcopyrite etc.) ore beds and related environments (like coal fire sites). Many undergo rapid dehydratation and sometimes oxidation.
Production
In the finishing of steel prior to plating or coating, the steel sheet or rod is passed through pickling baths of sulfuric acid. This treatment produces large quantities of iron(II) sulfate as a by-product. Another source of large amounts results from the production of titanium dioxide from ilmenite via the sulfate process. Ferrous sulfate is also prepared commercially by oxidation of pyrite, or by treating iron with sulfuric acid.[2]
Uses
Industrially, ferrous sulfate is mainly used as a precursor to other iron compounds. It is a reducing agent, mostly for the reduction of chromate in cement.
Nutritional supplement
Together with other iron compounds, ferrous sulfate is used to fortify foods and to treat iron-deficiency anemia. Copperas was given indiscriminately by untrained persons to slaves in the 18th and 19th centuries for various ailments.
Colorant
Ferrous sulfate was used in the manufacture of inks, most notably iron gall ink, which was used from the middle ages until the American Revolution. It also finds use in wool dyeing as a mordant.
Two different methods for the direct application of indigo dye were developed in England in the eighteenth century and remained in use well into the nineteenth century. One of these, known as china blue, involved iron(II) sulfate. After printing an insoluble form of indigo onto the fabric, the indigo was reduced to leuco-indigo in a sequence of baths of ferrous sulfate (with reoxidation to indigo in air between immersions). The china blue process could make sharp designs, but it could not produce the dark hues of other methods.
Ferrous sulfate can also be used to stain concrete a yellowish rust color.[3]
Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue.
Other uses
In horticulture it is used as a lawn conditioner and moss killer.
In the second half of the 19th century, ferrous sulfate was also used as a photographic developer for Collodion process images.
Ferrous sulfate is sometimes added to the cooling water flowing through the brass tubes of a turbine condenser. It forms an erosion-resistant, protective coating on the inside of the tube.
It has been applied for the purification of water by flocculation and for phosphate removal in municipal and industrial sewage treatment plants to prevent eutrophication of surface water bodies.
See also
- Iron(III) sulfate, the other common simple sulfate of iron.
- Ammonium iron(II) sulfate, a common double salt of ammonium sulfate with iron(II) sulfate.
References
- ^ "U+26A8 VERTICAL MALE WITH STROKE SIGN". Retrieved on 2008-03-06.
- ^ Egon Wildermuth, Hans Stark, Gabriele Friedrich, Franz Ludwig Ebenhöch, Brigitte Kühborth, Jack Silver, Rafael Rituper “Iron Compounds” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, Wienheim, 2005.
- ^ How To Stain Concrete with Iron Sulfate
External links
- "Product Information". Chemical Land21 (January 10th, 2007).
