ironoxide

Iron oxide refers to a class of inorganic compounds composed of iron and oxygen. The term encompasses several stoichiometries, including iron(II) oxide (FeO), iron(III) oxide (Fe2O3), and iron(II,III) oxide (Fe3O4). These oxides occur in nature as minerals such as hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH). Iron oxides are characterized by multiple oxidation states of iron, which influence their color, magnetic properties, and stability. Among them, Fe3O4 is ferrimagnetic and mixed-valence, while Fe2O3 is common in the red-brown pigments found in soils and rocks.

Formation and properties: Iron oxides form through oxidation of elemental iron or iron-containing minerals in air and water. Rust is the hydrated product of iron(III) oxide, often written as Fe2O3·nH2O. FeO is relatively unstable at room temperature and tends to convert to Fe3O4 or Fe2O3. Colors vary from black (Fe3O4) to red-brown (Fe2O3) and gray (FeO). Magnetite (Fe3O4) is ferrimagnetic and is used in magnetic applications, whereas hematite is weakly magnetic and widely used as a pigment.

Applications and occurrence: Iron oxides are extensively used as pigments, providing red, brown, yellow, and black colors in paints, plastics, cosmetics, and coatings. They serve as catalysts in chemical reactions, and iron oxide nanoparticles are employed in data storage, environmental remediation, and magnetic resonance imaging as contrast agents. In metallurgy, hematite ores are reduced to metallic iron in smelting processes.

Safety and handling: Iron oxides are generally of low acute toxicity, but fine powders can irritate the respiratory tract and eyes. Occupational exposure to iron oxide dust is monitored in some industries, and standard safety practices apply to handling and disposal of oxide powders.