FeCl36H2O

FeCl3·6H2O, commonly called iron(III) chloride hexahydrate, is a hydrated inorganic salt of iron in the +3 oxidation state. It forms pale yellow to yellow-brown crystals that are highly hygroscopic and readily dissolve in water to give strongly acidic solutions. The compound has a molar mass of about 270.3 g/mol.

In the solid, iron(III) is coordinated by three chloride ligands and six water molecules, giving the hexahydrate structure. When dissolved, Fe3+ ions interact with water to form hydrolyzed ferric species, which can lead to the formation of ferric hydroxide precipitates under certain conditions, imparting a brown color to solutions or suspensions.

Preparation and stability: FeCl3·6H2O is typically produced by dissolving iron or iron-containing materials in chlorine gas to form iron(III) chloride, followed by crystallization from water to yield the hexahydrate. It can also be obtained by hydration of anhydrous FeCl3. The hexahydrate is stable under ordinary conditions but readily loses water upon heating, eventually converting to anhydrous FeCl3.

Uses: The hexahydrate is widely employed as a coagulant in water and wastewater treatment, where it helps remove suspended solids and some contaminants. It also serves as a Lewis acid catalyst in various organic reactions, including Friedel–Crafts acylations and polymerization processes. Additionally, FeCl3·6H2O is used as a copper etchant in printed circuit board manufacture and in certain analytical and laboratory procedures.

Safety: FeCl3·6H2O is corrosive to skin and eyes and should be handled with appropriate personal protective equipment. It can cause irritation and burns upon contact and releases acidic fumes when heated. It should be stored in a tightly closed container away from bases and reducing agents.