Iron(II,III) oxide

Iron(II,III) oxide

Names
IUPAC name iron(II) iron(III) oxide
Other names ferrous ferric oxide, ferroso ferric oxide, iron(II,III) oxide, magnetite, black iron oxide, lodestone, rust, iron(II) diiron(III) oxide
Identifiers
CAS Number	1317-61-9 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:50821 Y
ChEMBL	ChEMBL1201867 N
ChemSpider	17215625 Y
ECHA InfoCard	100.013.889
PubChem	16211978
UNII	XM0M87F357 Y
InChI InChI=1S/3Fe.4O Y Key: SZVJSHCCFOBDDC-UHFFFAOYSA-N Y InChI=1/3Fe.4O/rFe3O4/c1-4-2-6-3(5-1)7-2 Key: SZVJSHCCFOBDDC-QXRQKJBKAR
SMILES O1[Fe]2O[Fe]O[Fe]1O2
Properties
Chemical formula	Fe3O4 FeO.Fe2O3
Molar mass	231.533 g/mol
Appearance	solid black powder
Density	5 g/cm3
Melting point	1,597 °C (2,907 °F; 1,870 K)
Refractive index (nD)	2.42
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

FeO.Fe₂O₃

Iron(II,III) oxide is the chemical compound with formula Fe₃O₄. 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 (Fe₂O₃) also known as hematite. It contains both Fe²⁺ and Fe³⁺ ions and is sometimes formulated as FeO ∙ Fe₂O₃. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment which is synthesised rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production.

Under anaerobic conditions, ferrous hydroxide (Fe(OH)₂) can be oxidized by water to form magnetite and molecular hydrogen. This process is described by the Schikorr reaction:

The well-crystallized magnetite (Fe₃O₄) is thermodynamically more stable than the ferrous hydroxide (Fe(OH)₂ ).

Magnetite can be prepared in the laboratory as a ferrofluid in the Massart method by mixing iron(II) chloride and iron(III) chloride in the presence of sodium hydroxide. Magnetite can also be prepared by the chemical co-precipitation in presence of ammonia, which consist in a mixture of a solution 0.1 M of FeCl₃·6H₂O and FeCl₂·4H₂O with mechanic agitation of about 2000 rpm. The molar ratio of FeCl₃:FeCl₂ can be 2:1; heating this solution at 70 °C, and immediately the speed is elevated to 7500 rpm and adding quickly a solution of NH₄OH (10 volume %), immediately a dark precipitate will be formed, which consists of nanoparticles of magnetite. In both cases, the precipitation reaction rely on a quick transformation of acidic hydrolyzed iron ions into the spinel iron oxide structure, by hydrolysis at elevated pH values (above ca. 10).