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Iron(III) oxide in a vial. Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe 2 O 3.It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry.
Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe 3 O 4.It occurs in nature as the mineral magnetite.It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe 2 O 3) which also occurs naturally as the mineral hematite.
Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite. [3] [4] One of several iron oxides, it is a black-colored powder that is sometimes confused with rust, the latter of which consists of hydrated iron(III) oxide (ferric oxide).
Iron is stored in many organisms in the form of ferritin, which is a ferrous oxide encased in a solubilizing protein sheath. [ 10 ] Species of bacteria , including Shewanella oneidensis , Geobacter sulfurreducens and Geobacter metallireducens , use iron oxides as terminal electron acceptors .
Ferric iodide, a black solid, is not stable in ordinary conditions, but can be prepared through the reaction of iron pentacarbonyl with iodine and carbon monoxide in the presence of hexane and light at the temperature of −20 °C, with oxygen and water excluded. [13] Complexes of ferric iodide with some soft bases are known to be stable compounds.
For elements that have multiple allotropes, the reference state usually is chosen to be the form in which the element is most stable under 1 bar of pressure. One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation. [2]
Some through all four oxygen atoms, some with two oxygen atoms. Half of the water is lattice water , being situated between chains of Fe oxalates. Mössbauer spectrum of Fe 2 (C 2 O 4 ) 3 · 4 H 2 O exhibits an isomer shift of 0.38 mm/s and a quadrupole splitting of 0.40 mm/s, suggesting a high spin Fe 3+ in octahedral coordination.
The reduction of two water protons is accompanied by the production of molecular hydrogen (H 2), and; the loss of two water molecules from the iron(II) and iron(III) hydroxides giving rise to its dehydration and to the formation of a thermodynamically more stable phase iron(II,III) oxide.