Rautaoksidia

Rautaoksidia (iron oxides) are a group of chemical compounds composed of iron and oxygen. They occur naturally as minerals and are also manufactured for pigments and functional materials. The best known members are hematite (Fe2O3), magnetite (Fe3O4), goethite (FeO(OH)) and ferric oxide hydrates such as ferrihydrite; wüstite (FeO) is stable mainly under reducing conditions.

Occurrence and formation: Iron oxides form by weathering and oxidation of iron-bearing minerals, by high-temperature magmatic processes, or by precipitation from iron-rich waters. Hematite and goethite are common in soils and sedimentary rocks, magnetite is widespread in crustal rocks, and ferric oxides contribute to red or brown coloration in soils.

Properties: These compounds are typically insoluble in water. They range in color from black (magnetite) to deep red (hematite) and yellow-brown (goethite). Magnetite shows ferrimagnetic properties; hematite is weakly magnetic; many iron oxides are paramagnetic or antiferromagnetic at varying temperatures.

Uses: They are used as pigments (red, brown, and black iron oxides) in paints, plastics, and ceramics. They are ores of iron; magnetite and hematite are mined for iron production. In technology, ferrites derived from iron oxides are used in electronics and catalysis; nanoscale iron oxides are studied for medical imaging and therapy.

Safety: Handling iron oxide powders requires standard industrial hygiene to avoid inhalation hazards; generally low acute toxicity but dust can irritate the lungs.