Iron(II,III) oxide
Iron(II,III) oxide, also known as magnetite, is a mixed-valence iron oxide with the chemical formula Fe3O4. It is one of the most important iron oxides, distinguished by its ferrimagnetic properties. This means it exhibits spontaneous magnetization, meaning it can be attracted to a magnet and can itself become a magnet.
Properties
- Chemical Formula: Fe3O4
- Molar Mass: 231.533 g/mol
- Appearance: Black, metallic-looking crystalline solid
- Density: 5.17 g/cm³
- Melting Point: 1597 °C (1870 K; 2907 °F)
- Solubility: Insoluble in water, soluble in concentrated acids
- Crystal Structure: Inverse spinel structure. The iron cations are present in two oxidation states: Fe(II) and Fe(III). The Fe(II) ions occupy octahedral sites within the crystal lattice, while the Fe(III) ions are distributed between octahedral and tetrahedral sites. This specific arrangement of ions contributes significantly to its magnetic properties.
- Magnetic Properties: Ferrimagnetic. It is strongly attracted to magnets and exhibits a high Curie temperature, above which it loses its ferrimagnetism.
Occurrence and Formation
Magnetite is a relatively common mineral, found widely in igneous and metamorphic rocks. It also forms in sedimentary environments, often associated with other iron oxides and minerals. It can form through various geological processes, including magmatic crystallization, hydrothermal alteration, and bacterial activity.
Uses
The unique properties of magnetite make it useful in a wide range of applications, including:
- Pigments: Used in paints and coatings due to its black color.
- Magnetic Materials: A key component in various magnetic devices, including permanent magnets, recording media, and magnetic fluids.
- Magnetic Resonance Imaging (MRI): Superparamagnetic iron oxide nanoparticles are used as contrast agents in MRI scans, enhancing the visibility of certain tissues.
- Catalysis: Used as a catalyst in various chemical reactions.
- Mineral Resource: A significant ore of iron.
Related Compounds
- Iron(II) oxide (FeO)
- Iron(III) oxide (Fe2O3) (Hematite)
Further Reading
Further information can be found in mineralogical and materials science literature.