Used for sewage treatment and drinking water production to remove impurities and odors. The standard chemical for etching printed circuit boards (PCBs) to remove excess copper. Acts as a catalyst in the production of PVC (vinyl) and in Friedel-Crafts reactions. Used in chloridizing metal ores and as an etching agent for stainless steel. Historically used as a hemostatic agent (to stop bleeding) and in some veterinary applications.

Its primary role is as a coagulant and etchant. Aggregates small particles into larger clumps for removal in liquids. Acts as a powerful Lewis acid catalyst in organic chemistry.

Iron(III) chloride anhydrous (FeCl3) is a highly acidic inorganic salt. Appears as dark green to black crystals (looks reddish-purple in reflected light). Extremely hygroscopic it absorbs moisture from the air to turn into a syrupy liquid. Dissolves in water through a highly exothermic reaction (releases significant heat).