Iron Oxide

Brief Overview

Iron(III) oxide or ferric oxide is an inorganic compound with the formula Fe₂O₃. It, along with iron(II) oxide (FeO) and iron(II, III) oxide (Fe₃O₄), is one of the three main oxides of iron. FeO is rare while Fe₃O₄ occurs naturally as the mineral magnetite. Fe₂O₃ is also known as the mineral hematite, which is the main source of iron for the steel industry. It is ferromagnetic, dark red to red-brown, and readily attacked by acids. Iron(III) oxide is also often known as rust, which is acidic in nature.

Manufacturing Process

Iron(III) oxide is a product of the oxidation of iron. It can be prepared in the laboratory by electrolyzing a solution of sodium bicarbonate, an inert electrolyte, with an iron anode: 4Fe + 3O₂ + 2H₂O → 4Fe(O)OH. The hydrated iron(III) oxide formed (Fe(O)OH) is dehydrated around 200 °C to yield iron(III) oxide: 2FeO(OH) → Fe₂O₃ + H₂O

Iron Industry

It is widely used as the raw material for steel and iron industries for the production of iron, steel, and many alloys. 

Pigment

Iron(III) oxide is also used as a pigment under names various names e.g. Pigment Brown 6 and Pigment Brown 7. Some of the pigments are approved by the US Food and Drug Administration (FDA) for use in cosmetics. Iron oxides are also used as pigments in dental composites alongside titanium oxides.

Polishing

The very fine powder of ferric oxide, known as “jeweler's rouge”, “red rouge”, or “rouge”, is used as the final polish on metallic jewelry and lenses, and historically in cosmetics. It is used in optics fabrication and by jewelers for the superior finish it can produce. When rouge is used to polish gold, it slightly stains the gold, which contributes to the appearance of the finished piece. Rouge is sold as a powder, paste, laced on polishing cloths, or solid bar (with a wax or grease binder).