Iron(III) oxide



Iron(III) oxide
Other names Ferric oxide
Hematite
Identifiers
CAS number 1317-60-8
[1309-37-1
[1309-37-1] (Iron Oxide Red)&c=0&v= 1317-60-8
[1309-37-1]
[1309-37-1] (Iron Oxide Red)]
Properties
Molecular formula O3
Molar mass 159.69 g/mol
Appearance red-brown solid
Density 5.24 g/cm3, solid
Melting point

1566 °C (1838 K) decomp.

Solubility in water insoluble
Structure
Crystal structure rhombohedral
Thermochemistry
Std enthalpy of
formation ΔfHo298 		−825.50 kJ/mol
Hazards
EU classification not listed
Flash point non-flammable
Related Compounds
Other anions Iron(II) sulfide
Other cations Iron(II) oxide
Iron(II,III) oxide
Ruthenium(IV) oxide
Osmium(IV) oxide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Iron(III) oxide — also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply O3.

Different forms

  • Alpha phase: rhombohedric, the most common form. Occurs naturally as the mineral ferromagnetic. It is easy to prepare using both thermal decomposition and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e.g. pressure, particle size, and magnetic field intensity.
  • Beta phase: cubic face centered, iron(III) chloride solution, or thermal decomposition of iron(III) sulfate.
  • Gamma phase: cubic, metastable, converts to the alpha phase at high temperatures. Occurs naturally as the mineral Ferrimagnetic. Ultrafine particles smaller than 10 nanometers are superparamagnetic. Can be prepared by thermal dehydratation of gamma iron(III) oxide-hydroxide, careful oxidation of iron(II,III) oxide. The ultrafine particles can be prepared by thermal decomposition of iron(III) oxalate.
  • Epsilon phase: rhombic, shows properties intermediate between alpha and gamma. So far has not been prepared in pure form; it is always mixed with the alpha phase or gamma phases. Material with a high proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. The epsilon phase is metastable, transforming to the alpha phase at between 500–750 °C. Can also be prepared by oxidation of iron in an sol-gel precipitation from iron(III) nitrate.
  • Other phases: high pressure, amorphous [1]

Uses

Iron(III) oxide is often used in magnetic storage, for example in the magnetic layer of floppy disks. These consist of a thin sheet of PET film, coated with iron(III) oxide. The particles can be magnetised to represent binary data. MICR (Magnetic Ink Character Recognition) also uses iron(III) oxide compounds, suspended in an ink which can be read by special scanning hardware.

A very fine powder of ferric oxide is known as jeweller's rouge, red rouge, or simply rouge. It is used to put the final polish on metallic jewellery and lenses, and historically as a cosmetic.

Rouge cuts slower than some modern polishes, such as wax or grease binder). Other polishing compounds are also often called "rouge", even when they do not contain iron oxide. Jewelers remove the residual rouge on jewelry by use of ultrasonic cleaning.

Iron(III) oxide is used in the production of pure iron in a blast furnace. Iron(III) oxide is also used in an extremely exothermic reaction called a thermite reaction.[1]

2 Al + O3

Iron(III) oxide is also used as a Food and Drug Administration (FDA)-approved for use in cosmetics.

ferrofluids. [2]it is found of mars

See also

General references

N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.

References

  1. ^ Adlam & Price, Higher School Certificate Inorganic Chemistry, Leslie Slater Price, 1945.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Iron(III)_oxide". A list of authors is available in Wikipedia.