FeCl3

Ferric chloride, with the chemical formula FeCl3, is an inorganic compound of iron in the +3 oxidation state. The anhydrous solid is a reddish-brown, highly hygroscopic material, while the most common form encountered is the hexahydrate FeCl3·6H2O, an orange-brown crystalline solid. In water, FeCl3 forms strongly acidic solutions containing the hexaaquairon(III) ion [Fe(H2O)6]3+, which hydrolyzes to give Fe(OH)3 and HCl, producing characteristic yellow to brown solutions.

Preparation and properties

FeCl3 is typically produced commercially by chlorinating iron metal or iron oxides with chlorine gas at elevated temperatures: 2 Fe + 3 Cl2 → 2 FeCl3. In aqueous media, ferric chloride behaves as a Lewis acid and readily forms various coordination complexes. The compound is used in solution or as hydrates in laboratory and industrial processes, and it readily hydrolyzes upon exposure to moisture.

Uses

Ferric chloride has diverse applications. It is widely used as an etchant for copper in printed circuit board processing, as a coagulant and phosphate remover in water and wastewater treatment, and as a catalyst in organic synthesis, including Friedel–Crafts reactions and certain oxidation or coupling processes. In some textile and pigment applications, ferric chloride serves as a mordant or pigment precursor.

Safety and handling

FeCl3 is corrosive and irritant to skin, eyes, and the respiratory system. Aqueous solutions are strongly acidic and can cause chemical burns. It can react vigorously with reducing agents and organic materials, and releases hydrochloric acid upon hydrolysis. It should be stored in a tightly sealed, dry container; handle with appropriate PPE to avoid moisture contact and inhalation of dust or fumes.