What is the decomposition of Fe3O4

Iron oxides

Iron oxides. Ferrous oxide, black compound ("Wustite phase") of the composition Fe, which always has an iron deficit compared to the formula FeO0,9O to Fe0,95O, obtained by oxidizing iron with oxygen or water vapor above 566 ° C. This oxide is stable above 566 ° C, metastable at room temperature and can be obtained in the laboratory as a pyrophoric powder by thermal decomposition of iron (II) oxalate in a vacuum: FeC2O4 → FeO + CO + CO2.

Iron (II, III) oxide, Fe3O4, most stable iron oxide, deep black, ferromagnetic compound with inverse spinel structure (FeIIFe2IIIO4); D. 5.18 g cm-3, M.p. 1538 ° C (b.). Fe3O4 is achieved by passing steam over iron below 566 ° C according to 3 Fe + 4 H2O → Fe3O4 + 4 H.2 or produced by vigorous annealing of iron (III) oxide and is also produced as a "hammer blow" when the iron parts that spring off during the forging of iron are burned. Fe comes in nature3O4 in large deposits as magnetite (magnetic iron stone) and forms a very popular raw material for iron and steel production. It is used as an electrode material for chlor-alkali electrolysis, as a glass coloring and polishing agent, as a filler and, under the names iron oxide black or iron black, as a pigment.

Ferric oxide, Fe2O3, dimorphic compound, D. 5.12 to 5.24 g cm-3, M.p. 1565 ° C. Occurring in nature as hematite in various forms, is α-Fe2O3 the permanent form (rhombohedral, paramagnetic), while the cubic crystallizing γ-Fe2O3 with careful oxidation of Fe3O4 according to 2 Fe3O4 + O2 → 3 feet2O3 is formed and when heated to> 300 ° C in α-Fe2O3 transforms. α-Fe2O3 can also be obtained by heating iron (III) oxide hydrate or iron (III) salts of volatile acids. When heated to> 1200 ° C in air, Fe goes2O3 with elimination of oxygen in Fe3O4 above. Fe2O3 is used in large quantities as a pigment under the names iron oxide red or iron red. Annealed Fe2O3 is very hard, so it can be used as a polishing agent for glass, metal and precious stones (polishing red).

The o. A. Iron oxide pigments and iron oxide yellow (iron hydroxide) are very resistant and have excellent fastness properties. They are suitable for all binders, also as a coloring additive for cement, building materials and plastics, in ceramics and in the graphic arts industry. Iron oxide red is also of great importance for anti-rust coatings on steel structures and ship hulls.