Iron (III) oxide is a hydrated iron compound and an important element in chemistry. It is a basic anhydride and can react with acids and strong reducing agents in redox reactions.
It has a d-block status and is a relatively common element found in nature as the mineral magnetite, hematite, goethite and limonite. It is also commonly used as an alloy with carbon to form steel.
The melting point of pure iron is 1538 degrees C. Addition of carbon lowers the melting point to as low as 1130 degrees C.
There are two main phases of iron(III) oxide: the beta phase and the gamma phase. Both are formed naturally from hematite, which is the most common source of iron. The beta phase is a cubic face centered, metastable, high-temperature form. It can be prepared by reduction of hematite with carbon or by pyrolysis of a solution of iron(III) chloride.
Maghemite is a ferromagnetic mineral that occurs naturally as the iron oxide g-Fe2O3. It can be obtained by thermal dehydratation of gamma iron(III) oxide-hydroxide or by careful oxidation of iron(II,III) oxide. Ultrafine particles smaller than 10 nanometers are superparamagnetic and have applications in recording tapes.
Chemically, Fe2O3 behaves as a refractory antiflux material in a glaze melt. It can combine with alumina to stiffen and stabilize the melt. In a glaze with very low alumina content, it can act as an alkali, combining with silica.
It can fire from bluish to apple green in reduction, and in alkaline glazes, straw yellow to yellow brown. It can also be used to make red iron oxide, called rust, which is often used as an anti-corrosion pigment in paints.