ironIII

Iron(III), also called ferric iron, denotes iron in the +3 oxidation state, symbol Fe3+. In chemistry, ferric denotes compounds containing Fe3+. In aqueous solution, Fe3+ forms the hexaaquairon(III) ion [Fe(H2O)6]3+, which progressively hydrolyzes as pH increases to yield various iron(III) hydroxide species.

Ferric compounds are typically less soluble and tend to form oxides and hydroxides rather than simple salts. The most common ferric oxides are hematite (Fe2O3) and goethite (FeO(OH)); ferrihydrite (Fe5HO8·4H2O) is a poorly crystalline, transient form that can act as a precursor to more stable oxides. The color of ferric compounds ranges from yellow to brown to reddish, often imparting rust-like appearances.

In nature and industry, iron(III) minerals are widespread and constitute major iron ore resources. Ferric oxides are important pigments and catalysts. Iron(III) salts such as ferric chloride (FeCl3), ferric nitrate (Fe(NO3)3), and ferric sulfate (Fe2(SO4)3) are commonly used as Lewis acids, oxidizing agents, or precursors in synthesis and materials processing.

Biologically, ferric iron is essential in trace amounts for many organisms, being transported and stored by proteins such as transferrin and ferritin. In aqueous environments, Fe3+ can participate in redox chemistry, including Fenton reactions when reduced to Fe2+, which can generate reactive oxygen species. Safety considerations for iron(III) salts include irritation of skin and eyes and potential gastrointestinal effects if ingested; standard chemical hygiene practices are advised.