It is used for sewerage treatment of industrial wastes, chloride hydrometallurgy (Silgarin process for the production of silicon), drinking water production, production of precursor for polyvinyl chloride (PVC), and copper-based metals in printed circuit boards. Iron (III) chloride is used as catalyst for the reaction of ethylene with chlorine, as a leaching agent, and as a drying reagent in certain reactions. It is a mild oxidizing agent and converts copper(I) chloride in to copper(II) chloride. As a moderately strong Lewis acid, it catalyzes chlorination of aromatic compounds and Friedel-Crafts reactions. Along with sodium iodide, it brings about reduction of organic azides to corresponding amines. It is useful in the detection of phenols and phenolic derivatives, gamma-hydroxybutyric acids, and also in Trinder spot test for detecting salicylic acids.
