Iron(III) oxide

Iron(III) oxide is an inorganic compound with the chemical formula Fe2O3. It is one of several iron oxides, the most common of which is iron(II,III) oxide (Fe3O4), which contains both Fe(II) and Fe(III) ions. Iron(III) oxide is also known as ferric oxide and is a reddish-brown solid that is insoluble in water. It occurs naturally as the mineral hematite, which is mined as the main ore of iron. It is used in various applications, from pigments in paints and cosmetics to catalysts in the synthesis of ammonia.

Properties

Iron(III) oxide is an amphoteric oxide, meaning it can react with both acids and bases. When heated with acids, it forms iron(III) salts, and when treated with alkaline solutions, it can yield iron(III) hydroxide. It is insoluble in water but dissolves readily in hydrochloric acid and sulfuric acid, forming corresponding iron(III) salts.

Synthesis

Iron(III) oxide can be synthesized in the laboratory by thermal decomposition of iron(III) hydroxide or iron(III) nitrate:

• 2 Fe(NO3)3 → 2 Fe2O3 + 6 NO2 + O2
• 2 Fe(OH)3 → Fe2O3 + 3 H2O

Commercially, it is produced on a large scale by the thermal decomposition of iron(III) sulfate.

Applications

Pigments

Iron(III) oxide is widely used as a pigment. Its natural form, hematite, gives a reddish color and is used in red ochre. Synthetic iron(III) oxide pigments are used in coatings, paints, and colored concretes.

Catalysis

It serves as a catalyst in the Haber-Bosch process for ammonia synthesis and in the water-gas shift reaction, which is essential for hydrogen production.

Magnetic Recording

Iron(III) oxide has been used in magnetic recording media, although it has largely been replaced by cobalt-modified iron oxides and other materials.

Health and Safety

While iron(III) oxide is not considered highly toxic, inhalation of its dust or fumes can cause irritation of the respiratory tract. In the workplace, exposure limits are set to ensure worker safety.

Environmental Impact

Iron(III) oxide is a naturally occurring mineral and is not regarded as harmful to the environment. However, mining and processing activities can have environmental impacts, including habitat destruction and water pollution.

See Also

• Iron
• Oxide
• Hematite
• Magnetite
• Rust