Iron(II) chloride (ferrous chloride)

Physical and chemical characteristics

Ferrous chloride is ionic and readily dissolves in water to give solutions containing Fe2+ and Cl- ions. The hydrated forms show characteristic coloration that can change on exposure to air as Fe2+ oxidizes to Fe3+. It forms coordination complexes with ligands and participates in redox chemistry typical of ferrous salts. Properties and data.

Preparation and reactions

Common laboratory preparation routes include reaction of elemental iron or iron metal filings with hydrochloric acid, and controlled reduction of ferric chloride. In solution Fe2+ is easily oxidized by oxygen to ferric species; it also reacts with hydrogen peroxide in Fenton-type processes to generate reactive radicals. Industrially, it can be produced or handled as the dihydrate for ease of use. Synthesis and reactions.

Uses and applications

• Water and wastewater treatment: used to precipitate and remove dissolved contaminants after oxidation.
• Chemical synthesis: source of Fe2+ in inorganic and organic transformations and as a precursor for iron-based catalysts.
• Industrial processes: employed in textile dyeing, metal finishing, and manufacture of some pigments.

Small-scale laboratory uses include acting as a reducing reagent or a starting material for coordination compounds. Typical applications.

Safety, handling and notable distinctions

Ferrous chloride is corrosive to metals and can be irritating to skin and eyes; solutions may darken on standing as oxidation occurs. It should be stored protected from air and moisture when anhydrous material is required, and handled with standard laboratory protective equipment. Important to distinguish Fe2+ (ferrous) chemistry from Fe3+ (ferric) chemistry: the two oxidation states differ in color, solubility behavior and reactivity. Safety guidance.