Ferric oxide, also called by its IUPAC name iron Trihydrate or iron(III) oxide, is an inorganic compound represented by the chemical formula Fe2O3 or Fe2H6O3 <1, 2>. It is one of the most important oxides of iron, the other two being ferrosoferric oxide (Fe3O4) and ferrous oxide (FeO) respectively <3, 4>. It naturally occurs as the mineral hematite <1>.

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Ferric Oxide Identification

CAS Number1309-37-1 <2>
PubChem CID56841934 <2>
ChemSpider ID452497 <1>
ChEBICHEBI:50819 <5>
EC Number616-935-8 <2>
RTECS NumberNO7400000 <6>


Ferric Oxide Formula

Hydrated Ferric Oxide

It is a reddish-brown gelatinous compound produced upon addition of alkali to solutions containing Fe(III) salts. It is also called hydrous ferric oxide and can be chemically represented either as Fe2O3.H2O or Fe(O)OH <12>. Some common forms of the hydrated ferric oxide include red lepidocrocite that occurs externally in rusticles and orange goethite that occurs on the inside of rusticles.

How is Ferric Oxide prepared

Ferric oxide is synthesized in the laboratory through electrolysis of sodium bicarbonate solution, which acts as an inert electrolyte, and an iron anode. The electrolytic conversion of iron into hydrated iron (III) oxide is represented as:

4Fe + 3O2 + 2H2O → 4 FeO(OH)

The hydrated iron (III) oxide, thus produced, undergoes dehydration at around 200 °C to form ferric oxide <7>.

2 FeO(OH) → Fe2O3 + H2O


Ferric Iron Oxide Powder

Chemical Reactions with Other Compounds

Oxidation of Ferrous Sulfate to Ferric Sulfate

It involves oxidation of ferrous disulfide (FeS2) to ferrous sulfate (FeSO4), which is further oxidized to ferric sulfate <13>:

FeS2 + 7O+ H2O → FeSO4 + H2SO42FeSO4 + H2SO4 + O → Fe2(SO4)3 + H2O

Aluminum replaces Iron from Ferric Oxide

Aluminum and ferric oxide undergo a redox reaction by which the metal replaces iron to form aluminum oxide:

Fe2O3 + 2Al → Al2O3 + 2Fe

Properties and Characteristics of Ferric Oxide

General Properties

Molar Mass/Molecular Weight159.68820 g/mol <1, 5>

Physical Properties

Color and AppearanceReddish-brown powder <1, 8>
Melting Point1538-1566 °C, 2800-2850 °F <8, 9>
Boiling PointN/A <8>
Density5.24 g cm-3 <8>
State of matter at room temperature (solid/liquid/gas)Solid <1>
SolubilitySoluble in warm HCl, slightly soluble in H2SO4 <9>
Solubility in WaterInsoluble <9>
Magnetic Susceptibility (χ)3.586 X 10-3 emu/Oe.g <10>
Heat Capacity103.9 J/mol.K

Atomic Properties

Crystal StructureRhombohedral (α form), cubic (β and γ forms), orthorhombic (ε form) <11>


Structure of Ferric Oxide


In iron industries for producing steel and alloys <9>.Ferric oxide powder, also called jeweler’s rouge, is used for polishing lenses and metallic jewelry <14>.Its granular form is used as a filtration media for pulling out phosphates in saltwater aquariums <14>.As FDA-approved Pigment Brown 6 and Pigment Red 101, for use in cosmetics <14>.In biomedical applications, because its nanoparticles are non-toxic and biocompatible <14>.

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Is it Dangerous

Prolonged exposure to its fume or dust can result in pneumoconiosis with fever, chills, aches, shortness of breath, and cough <15>. Repeated contact with eyes can discolor it and cause permanent iron staining <15>.