Iron(III) chloride is the inorganic compound with the formula FeCl3. Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The color depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.
Anhydrous iron(III) chloride has the BiI3 structure, with octahedral Fe(III) centers interconnected by two-coordinate chloride ligands.
Iron(III) chloride has a relatively low melting point and boils at around 315 °C. The vapor consists of the dimer Fe2Cl6 (like aluminium chloride) which increasingly dissociates into the monomeric FeCl3 (with D3h point group molecular symmetry) at higher temperature, in competition with its reversible decomposition to give iron(II) chloride and chlorine gas.
Product Name：Iron(III) chloride
Synonyms:ferric chloride,iron trichloride,molysite (mineral),Flores martis
Grade：anhydrous
CAS number:7705-08-0
Molecular formula: FeCl3
Molar mass:162.2 g·mol-1
hexahydrate: 270.3 g·mol−1
Appearance:green-black by reflected light; purple-red by transmitted light. Hexahydrate: yellow solid. solutions: brown
Density:2.80 g·cm−3. 40% solution: 1.4 g·ml−1
Melting point: 306 °C, 579 K, 583 °F
Boiling point: 315 °C, 588 K, 599 °F (partial decomposition to FeCl2+Cl2)
Solubility in water: 92 g/100 ml (20 °C)
Solubility in acetone/Methanol/Ethanol/Diethyl ether: 63 g/100 ml (18 °C) highly soluble
83 g/100 ml highly soluble
Viscosity: 40% solution: 12 cP
Crystal structure:hexagonal
Coordination geometry: octahedral
Main hazards: Very corrosive
R-phrases :R22, R34
S-phrases:S26, S28
Industrial
In industrial application, iron(III) chloride is used in sewage treatment and drinking water production.[4] In this application, FeCl3 in slightly basic water reacts with the hydroxide ion to form a floc of iron(III) hydroxide, or more precisely formulated as FeO(OH)-, that can remove suspended materials.
Fe3+ + 4 OH− → Fe(OH)4− → FeO(OH)2−·H2O
Another important application of iron(III) chloride is etching copper in two-step redox reaction
URL:iron(iii)-chloride(fecl3)
TITLE:Iron(III) Chloride(FeCl3)
to copper(I) chloride and then to copper(II) chloride in the production of printed circuit boards.[5]
FeCl3 + Cu → FeCl2 + CuCl
FeCl3 + CuCl → FeCl2 + CuCl2
Iron(III) chloride is used as catalyst for the reaction of ethylene with chlorine, forming ethylene dichloride (1,2-dichloroethane), an important commodity chemical, which is mainly used for the industrial production of vinyl chloride, the monomer for making PVC.
H2C=CH2 + Cl2 → ClCH2CH2Cl
In the laboratory iron(III) chloride is commonly employed as a Lewis acid for catalysing reactions such as chlorination of aromatic compounds and Friedel-Crafts reaction of aromatics. It is less powerful than aluminium chloride, but in some cases this mildness leads to higher yields, for example in the alkylation of benzene:
The “ferric chloride test” is a traditional colorimetric test for phenols, which uses a 1% iron(III) chloride solution that has been neutralised with sodium hydroxide until a slight precipitate of FeO(OH) is formed.[6] The mixture is filtered before use. The organic substance is dissolved in water, methanol or ethanol, then the neutralised iron(III) chloride solution is added—a transient or permanent coloration (usually purple, green or blue) indicates the presence of a phenol or enol.
Anhydrous Iron(III) chloride is sometimes used as a drying reagent in certain reactions.
Iron(III) chloride is sometimes used by American coin collectors to identify the dates of Buffalo nickels that are so badly worn that the date is no longer visible.
Iron(III) chloride is commonly used by knife craftsmen and sword smiths to stain blades, as to give a contrasting effect to the metal, and to view metal layering or imperfections.
Iron(III) chloride is necessary for the etching of photogravure plates for printing photographic and fine art images in intaglio and for etching rotogravure cylinders used in the printing industry.
Iron(III) chloride is also used in veterinary practice to treat overcropping of an animal’s claws, particularly when the overcropping results in bleeding.
