Ferric Chloride

Title: Ferric Chloride
CAS Registry Number: 7705-08-0
Additional Names: Flores martis
Molecular Formula: Cl3Fe
Molecular Weight: 162.20
Percent Composition: Cl 65.57%, Fe 34.43%
Line Formula: FeCl3
Literature References: Occurs in nature as the mineral molysite. Prepn: Tarr, Inorg. Synth. 3, 191 (1950); Pray, ibid. 5, 153 (1957); Epperson et al., ibid. 7, 163 (1963); Lieser, Elias, Z. Anorg. Allg. Chem. 316, 208 (1962); Attwood, Shelton, J. Inorg. Nucl. Chem. 26, 1758 (1964); Bardawil et al., Inorg. Chem. 3, 149 (1964). Acute toxicity: C. S. Hosking, Aust. Paediatr. J. 6, 92 (1970). Use as clinical reagent: L. Cassidei et al., Clin. Chim. Acta 90, 121 (1978).
Properties: Hexagonal, dark leaflets or plates. Red by transmitted light, green by reflected light; sometimes appears brownish-black. Very hygroscopic. Melts and volatilizes about 300°; bp ~316°; d25 2.90. Vapor density measurements show that it is dimeric at about 400° but monomeric above 750°. Dissociates at high temps to FeCl2 and Cl2. Readily absorbs water in air to form the hexahydrate. Readily sol in water, alcohol, ether, acetone; slightly sol in CS2. Practically insol in ethyl acetate. Keep well closed.
Boiling point: bp ~316°
Density: d25 2.90
Derivative Type: Hexahydrate
Properties: Brownish-yellow or orange monoclinic crystals. d 1.82. Structure: trans-[FeCl2(H2O)4]Cl.2H2O: Lind, J. Chem. Phys. 47, 990 (1967). Usually slight odor of HCl; very hygroscopic. mp ~37°. Readily sol in water, alcohol, acetone, ether; pH of 0.1 molar aq soln 2.0. Keep well closed. LD50 i.v. in mice: 0.049 mg Fe/g (Hosking).
Melting point: mp ~37°
Density: d 1.82
Toxicity data: LD50 i.v. in mice: 0.049 mg Fe/g (Hosking)
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, mucous membranes; abdominal pain, diarrhea, vomiting; possible liver damage. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 174.
Use: In photoengraving; photography; manuf of other Fe salts, pigments, ink; as catalyst in organic reactions; purifying factory effluents and deodorizing sewage; chlorination of Ag and Cu ores; as mordant in dyeing and printing textiles; oxidizing agent in dye manuf. Clinical reagent (amino acids in urine, esp in phenylketonuria).
Therap-Cat: Hexahydrate as astringent, styptic.
Therap-Cat-Vet: Styptic, astringent.
Keywords: Astringent.
Ferric Chromate(VI) Ferric Citrate Ferric Fluoride Ferric Formate Ferric Hydroxide

Iron(III) chloride
Iron(III) chloride hexahydrate.jpg
Iron-trichloride-sheet-3D-polyhedra.png Iron-trichloride-sheets-stacking-3D-polyhedra.png
CAS number 7705-08-0 YesY
10025-77-1 (hexahydrate)
PubChem 24380
ChemSpider 22792 YesY
UN number 1773 (anhydrous)
2582 (aq. soln.)
ChEBI CHEBI:30808 YesY
RTECS number LJ9100000
Jmol-3D images Image 1
Molecular formula FeCl3
Molar mass 162.2 g/mol (anhydrous)
270.3 g/mol (hexahydrate)
Appearance green-black by reflected light; purple-red by transmitted light
hexahydrate: yellow solid
aq. solutions: brown
Odor slight HCl
Density 2.898 g/cm3 (anhydrous)
1.82 g/cm3 (hexahydrate)
Melting point 306 °C (anhydrous)
37 °C (hexahydrate)
Boiling point 315 °C (anhydrous, decomp)
280 °C (hexahydrate, decomp) (partial decomposition to FeCl2 + Cl2)
Solubility in water 74.4 g/100 mL (0 °C)[1]
92 g/100 mL (hexahydrate, 20 °C)
Solubility in acetone
Diethyl ether
63 g/100 ml (18 °C)
highly soluble
83 g/100 ml
highly soluble
Viscosity 40% solution: 12 cP
Crystal structure hexagonal
Hazards[2][3][Note 1]
GHS pictograms Corr. Met. 1; Skin Corr. 1C; Eye Dam. 1Acute Tox. 4 (oral)
GHS signal word DANGER
GHS hazard statements H290, H302, H314, H318
GHS precautionary statements P234, P260, P264, P270, P273, P280, P301+312, P301+330+331, P303+361+353, P363, P304+340, P310, P321, P305+351+338
EU Index listed
NFPA 704
NFPA 704.svg
Flash point Non-flammable
Related compounds
Other anions Iron(III) fluoride
Iron(III) bromide
Other cations Iron(II) chloride
Manganese(II) chloride
Cobalt(II) chloride
Ruthenium(III) chloride
Related coagulants Iron(II) sulfate
Polyaluminium chloride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3. The colour of iron(III) chloride crystals 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 is deliquescent, forming hydrated hydrogen chloride mists in moist air. It is rarely observed in its natural form, mineral molysite, known mainly from some fumaroles.

When dissolved in water, iron(III) chloride undergoes hydrolysis and gives off heat in an exothermic reaction. The resulting brown, acidic, and corrosive solution is used as a flocculant in sewage treatment and drinking water production, and as an etchant for copper-based metals in printed circuit boards. Anhydrous iron(III) chloride is a fairly strong Lewis acid, and it is used as a catalyst in organic synthesis.