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Iron Oxide

Iron Oxide

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Amongst the wide variety of chemical compounds produced naturally or artificially, iron oxides are one of the most widespread. They are chemical compounds that contain iron and oxygen. They also exist as oxyhydroxides, and there are sixteen of them. These oxides assist in many biological and geological processes and are very useful as iron ores, catalysts and pigments.

Iron oxides exist in three different compositions which include: iron (II) oxide (wustite, FeO), Iron (II, III) oxide (magnetite, Fe3O4) and Iron (III) oxide (hematite, Fe2O3). Out of these three oxides, iron (III) oxide, also known as ferric oxide is common, iron (II) oxide is rare, and Fe3O4 occurs naturally.


Iron oxide can be hydrated to form other solutions. For example, the addition of soluble iron (III) produces a gelatinous precipitate, red-brown in colour. This precipitate is written as Fe2O3.H2O or Fe(O)OH, and when it is further heated, its water of hydration disappears. The remaining Fe2O3, when exposed to a temperature of about 1670K becomes a black compound, Fe3O4 (magnetite) which is the second form of iron oxides.

One common reaction used on Fe2O3 is the carbothermal reduction. The product of this reaction gives iron usually used to make steel.

2Fe2O3 + 3C 4Fe + 3CO2

Another reaction is the exothermic thermite reaction in which aluminium is made to react with Fe2O3 giving a product used for welding thick metals, e.g. Train tract rails. It is also used in making weapons and sculptures.


Iron oxide has a wide range of applications. When it is refined into very fine powder, it serves as a cosmetic and is used to polish metallic jewelry, as well as lenses. In this form, it is referred to as “rouge” and also a contributory factor in the fine appearance of gold. It is also used to give knives and other tools a good razor edge. When in granular form, it is used as a phosphate remover in aquariums. Also, they are used in audio tapes due to their ferromagnetic properties.

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