Iron(II,III) oxide

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Iron(II, III) oxide
Magnetite sample
IUPAC name
Iron(II) iron(III) oxide
Other names
Black iron oxide, ferroso ferric oxide, ferrous ferric oxide, iron(II,III) oxide, iron(II) diiron(III) oxide, lodestone, magnetite, rust
Molar mass 231.533 g/mol
Appearance Black solid
Odor Odorless
Density 5.0 g/cm3
Melting point 1,597 °C (2,907 °F; 1,870 K) (decomposition)
Boiling point Decomposes
Solubility Reacts with acids, halogens
Insoluble in organic solvents
Vapor pressure ~0 mmHg
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
5,000 mg/kg (rat, oral)
Related compounds
Related compounds
Iron(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Iron(II,III) oxide, also known as ferrous ferric oxide, black iron oxide, or mineral magnetite, is an iron oxide with the chemical formula Fe3O4.



Magnitite can be calcinated in air to yield iron(III) oxide:

2 Fe3O4 + ½ O2 → 3 Fe2O3

Iron(II,III) oxide can also be used as source of iron oxide in thermite reactions.


Iron(II,III) oxide is a black compound, insoluble in water, but reacts with acids. It is ferrimagnetic and an electrical conductor.


Black iron oxide is available as pigment in pottery shops and can be cheaply purchased.

Purer magnetite can be bought online from chemical suppliers.

It also occurs naturally as the mineral magnetite.


There are several ways to prepare magnetite. One method involves the reduction of nitrobenzene with metallic iron and water, in the presence of iron(II) chloride, process that reduces the nitrobenzene to aniline. It can also be done by precipitating iron(II) salts as hydroxides, then carefully oxidizing the resulting iron(II) hydroxide at controlled pH.

Black iron oxide can also be prepared by oxidizing iron(II) hydroxide with water, in an oxygen-free medium.

3 Fe(OH)2 → Fe3O4 + H2 + 2 H2O

This process is known as Schikorr reaction.

Another method of producing this oxide is burning iron wire in oxygen.

3 Fe + 2 O2 → Fe3O4

This reaction may also give other iron oxides.




Black iron oxide is not particularly toxic, unless large amounts are consumed. Inhalation of finely powdered magnetite may lead to lung conditions.


Iron(II,III) oxide should be stored in closed containers, away from acidic vapors. Any clean plastic container can be used.


As iron(II,III) oxide occurs naturally, it is not harmful to the environment and can be useful as an iron supplement for soil.


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