Iron (III) oxide

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Crystal structure
Crystal structure of iron (III) oxide
__ Fe 3+      __ O 2−
Surname Iron (III) oxide
other names
  • Hematite (mineral)
  • red iron oxide
  • Diiron trioxide
  • Iron equioxide
  • Purple ore / gravel burn, residue sulfuric acid production from pyrite
  • E 172
Ratio formula Fe 2 O 3
Brief description

red to black crystals

External identifiers / databases
CAS number 1309-37-1
EC number 215-168-2
ECHA InfoCard 100.013.790
PubChem 518696
ChemSpider 14147
Wikidata Q419170
Molar mass 159.70 g mol −1
Physical state



5.24 g cm −3

Melting point

1539 ° C


almost insoluble in water

safety instructions
GHS labeling of hazardous substances
07 - Warning


H and P phrases H: 315-319-335
P: 261-305 + 351 + 338

1.5 mg m −3 (aerosol fraction)

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Iron (III) oxide is a stable oxide of iron . Among other things, it is part of the rust and causes its color. It crystallizes in the corundum structure.


It is possible to obtain red iron oxide by burning iron (III) oxide hydroxide, among other things . During this process, yellow iron oxide is heated to over 200 ° C, with the formation of water vapor.

Meaning and use

Iron (III) oxide, pure powder

Iron (III) oxide is used as a pigment and is known as iron oxide red. The hue varies between red-orange and deep red; it is also the main component of natural red earths .

Iron (III) oxide is used as a magnetizable material as a recording layer for audio tapes . Iron (III) oxide is also a component of superparamagnetic iron oxide nanoparticles , which are used as contrast media in magnetic resonance tomography and especially in molecular imaging .

It is also used in the thermite process in conjunction with aluminum :

Elemental aluminum reacts with iron (III) oxide to form elemental iron and aluminum (III) oxide .

In the early modern period it was also obtained by distilling iron sulfate (green vitriol) (caput mortuum, head of the dead) and used as red paint.


Iron (III) oxide occurs as a mineral in nature in two modifications :

See also

Web links

Commons : Ferric Oxide  - Collection of pictures, videos, and audio files

Individual evidence

  1. Entry on iron oxides. In: Römpp Online . Georg Thieme Verlag, accessed on November 10, 2014.
  2. a b c d Entry on iron (III) oxide in the GESTIS substance database of the IFA , accessed on August 3, 2007(JavaScript required) .
  3. a b Data sheet Iron (III) oxide from Sigma-Aldrich , accessed on March 29, 2011 ( PDF ).
  4. about DIN 6164 6 to 8 Kurt Wehlte : Materials and techniques of painting . Otto Maier, Ravensburg 1967, ISBN 3-473-48359-1 (previously: ISBN 3-473-61157-3 ) p. 113.
  5. ^ Heinrich Schönemann: From the history of chemistry: From the vitriols to sulfuric acid