Iron(III) chloride

Iron(III) chloride is an inorganic compound with formula FeCl₃, consisting of iron in the +3 oxidation state and chloride ions. It is used in water treatment, metal etching, and chemical synthesis.

Lewis acid: A chemical species that accepts an electron pair to form a covalent bond. Iron(III) chloride accepts electron pairs from substrates in reactions such as aromatic chlorination.
Coagulation (water treatment): A water-treatment process that destabilizes fine particles so they aggregate and can be removed. Iron(III) chloride supplies iron species that help particles aggregate before settling or filtration.
Iron: A chemical element with symbol Fe and atomic number 26, widely used in alloys and biological systems. Iron(III) chloride contains iron in its +3 oxidation state.
Iron(II) chloride: An iron chloride with formula FeCl₂, containing iron in the +2 oxidation state. Its lower iron oxidation state gives it different redox behavior and stoichiometry.
Hydrolysis: A reaction in which a substance reacts with water, often breaking bonds or changing ionic composition. Dissolved iron(III) chloride hydrolyzes, producing acidic solutions and iron-containing species.
Flocculation: The aggregation of small particles into larger clusters called flocs. Hydrolysis products from iron(III) chloride promote flocs that can be separated from water.
Chloride: The anion Cl⁻, formed when a chlorine atom gains one electron. Three chloride ions balance the charge of each iron(III) ion in FeCl₃.
Iron(III) sulfate: An iron(III) salt with formula Fe₂(SO₄)₃, used in water treatment and other applications. It can supply iron(III) for treatment while replacing chloride with sulfate.
Ferric chloride test: A qualitative chemical test in which iron(III) ions form colored complexes with certain compounds, especially phenols. The colored complexes provide a familiar analytical use of aqueous iron(III) chloride.
Printed circuit board: An electronic board whose conductive pathways are formed on an insulating substrate. Iron(III) chloride can etch exposed copper when fabricating circuit-board traces.

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