Iron(II) sulfate

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Iron(II) sulfate


Systematic name	Iron(II) sulfate
Other names	ferrous sulfate green vitriol copperas melanterite szomolnokite
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)
CAS number	[7720-78-7] (heptahydrate)
Appearance	blue/green or white crystals
Crystal structure	monoclinic
Density	1.898 g/cm³
Solubility (water)	Soluble
Melting point	64°C
Boiling point	90°C (becomes FeSO₄·H₂O)
Disclaimer and references

Iron(II) sulfate is the chemical compound with the formula (Fe S O₄). Also known as ferrous sulfate (or ferrous sulphate), iron(II) sulfate is most commonly encountered as the heptahydrate, blue-green color.

1 Hydrates
2 Production
3 Uses
4 References
5 External links

[edit] Hydrates

Iron(II) sulfate can be found in various states of hydration and several of these forms exist in nature.

FeSO₄·H₂O (mineral: szomolnokite)
FeSO₄·4H₂O
FeSO₄·5H₂O (mineral: siderotil)
FeSO₄·7H₂O (mineral: melanterite)

At 90°C, the heptahydrate loses water of hydration to form the colourless monohydrate, which is also called green vitriol, copperas.

[edit] 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 waste product. Iron(II) sulfate is prepared commercially by oxidation of pyrite or by treating iron with sulfuric acid. It is used in the manufacture of inks, most notably iron gall ink, which was commonly used during the time of the American Revolution, in wool dyeing as a mordant, and in water purification as a substitute for aluminium sulfate.

[edit] Uses

Ferrous sulfate is also an additive found in various foods, including the enriched corn meal that serves as a key ingredient in Cheetos^[1].

Ferrous sulfate is also used to treat iron-deficiency anemia. Side effects of therapy may include nausea and epigastric abdominal discomfort after taking iron. These side effects can be minimized by taking ferrous sulfate at bedtime.

Ferrous sulfate can also be used to color concrete. It is best used for newly cured concrete. Mix with water until saturated and spray onto concrete. The color will range from yellow to rust.

Two different methods for the direct application of indigo 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 the insoluble form of indigo onto the fabric, the indigo was oxidized in a sequence of baths of ferrous sulfate. The china blue process could make sharp designs, but it could not produce the dark hues.

Ferrous sulfate (then known as green vitriol) was also used in the Middle Ages to make iron gall ink for use in writing.

In horticulture it is used as a lawn conditioner and moss killer, traditionally referred to as sulphate of iron or copperas.

In the second half of the 19th century Ferrous Sulfate was also used as a photographic developer for Collodion process images.

Woodworkers use ferrous sulfate solutions to color maple wood a silvery hue.