Iron(III) chloride 446457 224555743 2008-07-09T11:41:50Z Soppsuppe 7447395 I have mentioned other important industrial application :''Iron chloride redirects here. For Iron(II) chloride, see [[Iron(II) chloride]].'' {{chembox new <!-- infobox --> | ImageFile = Iron(III)_chloride_hexahydrate.jpg | ImageSize = 200px | ImageFileL1 = Iron-trichloride-sheet-3D-polyhedra.png | ImageSizeL1 = 150px | ImageFileR1 = Iron-trichloride-sheets-stacking-3D-polyhedra.png | ImageSizeR1 = 150px | IUPACName = Iron(III) chloride | OtherNames = ferric chloride<br/>iron trichloride<br/>[[molysite]] (mineral)<br/>Flores martis | Section1 = {{Chembox Identifiers | Abbreviations = | CASNo = 7705-08-0 | CASNos = <br/>hexahydrate:&nbsp;{{CASREF|CAS=10025-77-1}} | EINECS = | PubChem = | SMILES = | InChI = | RTECS = LJ9100000 | MeSHName = | ChEBI = | KEGG = | ATCCode_prefix = | ATCCode_suffix = | ATC_Supplemental =}} | Section2 = {{Chembox Properties | Formula = FeCl<sub>3</sub> | MolarMass = 162.2&nbsp;g&middot;mol<sup>-1</sup> | MolarMass_notes = <br/>hexahydrate:&nbsp;270.3&nbsp;g·mol<sup>−1</sup> | Appearance = green-black by reflected light; purple-red by transmitted light<br/>hexahydrate: yellow solid<br/> aq. solutions: brown | Density = 2.80&nbsp;g·cm<sup>−3</sup><br/>40% solution: 1.4&nbsp;g·ml<sup>−1</sup> | MeltingPtC = 306 | Melting_notes = | BoilingPtC = 315 | Boiling_notes = partial decomposition to FeCl<sub>2</sub>+Cl<sub>2</sub> | Solubility = 92&nbsp;g/100&nbsp;ml (20&nbsp;°C) | SolubleOther = 63&nbsp;g/100&nbsp;ml (18&nbsp;°C)<br/>highly soluble<br/>83&nbsp;g/100&nbsp;ml<br/> highly soluble | Solvent = [[acetone]]<br/>[[Methanol]]<br/>[[Ethanol]]<br/>[[Diethyl ether]] | pKa = | pKb = | Viscosity = 40%&nbsp;solution: 12&nbsp;c[[Poise|P]]}} | Section5 = {{Chembox Structure | CrystalStruct = [[hexagonal]] | SpaceGroup = | Coordination = [[octahedral]] | LattConst_a = | LattConst_b = | LattConst_c = | LattConst_alpha = | LattConst_beta = | LattConst_gamma = | MolShape = | OrbitalHybridisation = | Dipole = }} | Section7 = {{Chembox Hazards | EUClass = | EUIndex = | MainHazards = Very corrosive | NFPA-H = 3 | NFPA-F = | NFPA-R = 1 | NFPA-O = | RPhrases = {{R22}}, {{R34}} | SPhrases = {{S26}}, {{S28}} | RSPhrases = | FlashPt = | Autoignition = | ExploLimits = | PEL = }} | Section15 = {{Chembox Related | OtherAnions = [[Iron(III) fluoride]]<br/>[[Iron(III) bromide]] | OtherCations = [[Iron(II) chloride]]<br/>[[Manganese(II) chloride]]<br/>[[Cobalt(II) chloride]]<br/>[[Ruthenium(III) chloride]] | OtherFunctn = [[Iron(II) sulfate]]<br/>[[Aluminium chloride|Polyaluminium chloride]] | Function = [[coagulant]]s | OtherCpds = }} }} '''Iron(III) chloride''', [[Generic name|generically]] called '''ferric chloride''', is an industrial scale commodity [[chemical compound]], with the formula FeCl<sub>3</sub>. 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. When dissolved in water, iron(III) chloride undergoes [[hydrolysis]] and gives off heat in an [[exothermic]] reaction. The resulting brown, acidic, and [[corrosion|corrosive]] solution is used as a [[coagulant]] in [[sewage treatment]] and [[water treatment|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]]. == Chemical and physical properties == Iron(III) chloride has a relatively low melting point and boils at around 315&nbsp;°C. The vapour consists of the dimer Fe<sub>2</sub>Cl<sub>6</sub> (compare [[aluminium chloride]]) which increasingly dissociates into the monomeric FeCl<sub>3</sub> (D<sub>3h</sub> [[symmetry group|point group]] [[molecular symmetry]]) at higher temperature, in competition with its reversible decomposition to give [[iron(II) chloride]] and [[chlorine]] gas.<ref>{{cite book | last = Holleman | first = A.F. | coauthors = Wiberg, E. | title = Inorganic Chemistry | publisher = Academic Press | location = San Diego | year = 2001 | id = ISBN 0-12-352651-5}}</ref> ===Reactions=== Iron(III) chloride is a moderately strong [[Lewis acid]], forming [[adduct]]s with [[Lewis base]]s such as [[triphenylphosphine oxide]], e.g. FeCl<sub>3</sub>(OPPh<sub>3</sub>)<sub>2</sub> where Ph = [[phenyl]]. Iron(III) chloride reacts with other [[chloride]] salts to give the yellow [[tetrahedral]] FeCl<sub>4</sub><sup>−</sup> ion. Salts of FeCl<sub>4</sub><sup>−</sup> in [[hydrochloric acid]] can be extracted into [[diethyl ether]]. When heated with [[iron(III) oxide]] at 350&nbsp;°C, iron(III) chloride gives iron oxychloride, a layered solid and [[intercalation]] host. :FeCl<sub>3</sub> + Fe<sub>2</sub>O<sub>3</sub> → 3&nbsp;FeOCl In the presence of base, alkali metal [[alkoxide]]s react to give the [[dimer]]ic complexes: :2 FeCl<sub>3</sub> + 6 [[Ethanol|C<sub>2</sub>H<sub>5</sub>OH]] + 6 NH<sub>3</sub> → (Fe(OC<sub>2</sub>H<sub>5</sub>)<sub>3</sub>)<sub>2</sub> + 6 [[Ammonium chloride|NH<sub>4</sub>Cl]] [[Oxalic acid|Oxalate]]s react rapidly with aqueous iron(III) chloride to give [Fe(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]<sup>3−</sup>. Other [[carboxylate]] salts form complexes, e.g. [[Citric acid|citrate]] and [[tartaric acid|tartrate]]. Iron(III) chloride is a mild [[Redox|oxidising agent]], for example capable of oxidising [[copper(I) chloride]] to [[copper(II) chloride]]. Reducing agents such as [[hydrazine]] convert iron(III) chloride to complexes of iron(II). ===Structure=== Iron(III) chloride adopts the [[bismuth(III) iodide|BiI<sub>3</sub>]] structure, which features [[octahedral]] Fe(III) centres interconnected by two-coordinate chloride ligands. == Preparation and production == Anhydrous iron(III) chloride may be prepared by union of the elements:<ref>{{cite journal | first = B.R. | last = Tarr | title = Anhydrous Iron(III) Chloride | journal = Inorganic Syntheses | volume = 3 | pages = 191&ndash;194 | year = 1950 | doi = 10.1002/9780470132340.ch51}}</ref> :2&nbsp;Fe([[solid|s]]) + 3&nbsp;Cl<sub>2</sub>([[Gas|g]]) → 2&nbsp;FeCl<sub>3</sub>(s) Solutions of iron(III) chloride are produced industrially both from iron and from ore, in a closed-loop process. #Dissolving pure [[iron]] in a solution of iron(III) chloride<br/>Fe(s) + 2&nbsp;FeCl<sub>3</sub>(aq) → 3&nbsp;FeCl<sub>2</sub>(aq) #Dissolving [[iron ore]] in [[hydrochloric acid]]<br/>Fe<sub>3</sub>O<sub>4</sub>(s) + 8&nbsp;HCl(aq) → FeCl<sub>2</sub>(aq) + 2&nbsp;FeCl<sub>3</sub>(aq) + 4&nbsp;H<sub>2</sub>O #Upgrading the [[iron(II) chloride]] with [[chlorine]]<br/>2&nbsp;FeCl<sub>2</sub>(aq) + Cl<sub>2</sub>(g) → 2&nbsp;FeCl<sub>3</sub>(aq) Alternatively, iron(II) chloride can be oxidised with [[sulfur dioxide]]: :32&nbsp;FeCl<sub>2</sub> + 8&nbsp;SO<sub>2</sub> + 32&nbsp;HCl → 32&nbsp;FeCl<sub>3</sub> + S<sub>8</sub> + 16&nbsp;H<sub>2</sub>O Like many other hydrated metal chlorides, hydrated iron(III) chloride can be converted to the anhydrous salt by refluxing with [[thionyl chloride]].<ref>{{cite journal | title = Anhydrous Metal Chlorides | first = Alfred R. | last = Pray | coauthors = Richard F. Heitmiller, Stanley Strycker | journal = [[Inorganic Syntheses]] | volume = 28 | pages = 321&ndash;323 | doi = 10.1002/9780470132593.ch80 | year = 1990}}</ref> The hydrate cannot be converted to anhydrous iron(III) chloride by only heat, as instead HCl is evolved and [[iron oxychloride]] forms. == Uses == ===Industrial=== In industrial application, iron(III) chloride is used in [[sewage treatment]] and [[water treatment|drinking water production]].<ref name=wtcbrochure">{{cite book | title = Water Treatment Chemicals | url = http://www.basechemicals.com/NR/rdonlyres/ACEEFEE2-EB7D-4A36-B52F-E7B27BFBF87E/20148/AkzoWTCBrochureENG.pdf | publisher = [[Akzo Nobel|Akzo Nobel Base Chemicals]] | year = 2007 | accessdate = 2007-10-26}}</ref> In this application, FeCl<sub>3</sub> in slightly basic water reacts with the [[hydroxide]] ion to form a [[Flocculation|floc]] of iron(III) hydroxide, or more precisely formulated as FeO(OH)<sup>-</sup>, that can remove suspended materials. :Fe<sup>3+</sup> + 4 OH<sup>−</sup> → Fe(OH)<sub>4</sub><sup>−</sup> → FeO(OH)<sub>2</sub><sup>−</sup>·H<sub>2</sub>O In industrial application also as leaching agent in chloride hydrometallurgi. Ref. Separation and Purification Technology 51 (2006) pp 332-337. For example in the production of Si from FeSi. (Silgrain process).Ref. Chem. Eng. Sci. 61 (2006) pp 229-245. Another important application of iron(III) chloride is etching [[copper]] in two-step [[redox]] reaction to [[copper(I) chloride]] and then to [[copper(II) chloride]] in the production of [[printed circuit boards]].<ref>{{cite book | first = N.N. | last = Greenwood | coauthors = A. Earnshaw | title = Chemistry of the Elements | edition = 2nd ed. | publisher = [[Butterworth-Heinemann]] | location = Oxford | year = 1997}}</ref> :FeCl<sub>3</sub> + Cu → FeCl<sub>2</sub> + CuCl :FeCl<sub>3</sub> + CuCl → FeCl<sub>2</sub> + CuCl<sub>2</sub> 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 [[polyvinyl chloride|PVC]]. :H<sub>2</sub>C=CH<sub>2</sub> + Cl<sub>2</sub> → ClCH<sub>2</sub>CH<sub>2</sub>Cl ===Laboratory use=== In the laboratory iron(III) chloride is commonly employed as a [[Lewis acid]] for [[catalyst|catalysing]] reactions such as [[chlorination]] of [[aromatic compound]]s 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: [[Image:FeCl3 Friedel-Crafts.gif|400px|Iron(III) chloride as a catalyst]] 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.<ref>{{cite book | first = B.S. | last = Furnell | coauthors = et al. | title = Vogel's Textbook of Practical Organic Chemistry | edition = 5th edition | publisher = [[Longman]]/[[Wiley]] | location = New York | year = 1989}}</ref> 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. ===Other uses=== * 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 nickel]]s 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 often used to etch the [[widmanstatten pattern]] in Iron [[Meteorites]] . * 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 used in veterinary practice to treat overcropping of an animal's claws, particularly when the overcropping results in bleeding. * Iron(III) chloride reacts with cyclopentadienylmagnesium bromide in one preparation of [[ferrocene]], a metal-sandwich complex.<ref>{{cite journal | first = T.J. | last = Kealy | title = A New Type of Organo-Iron Compound | journal = Nature | volume = 168 | pages = 1040 | year = 1951 | doi = 10.1038/1681039b0}}</ref> * Iron(III) chloride is sometimes used in the technique of [[Raku|Raku Firing]] as an additive during the reduction process, turning a pottery piece a burnt orange color due to the iron content present in the reducing atmosphere. ==Safety== Iron(III) chloride is toxic, highly corrosive and acidic. The anhydrous material is a powerful dehydrating agent. == See also == * [[iron(II) sulfate]] * [[aluminium chloride]] ==References== {{reflist}} == Further reading == # ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990. # ''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960. # D. Nicholls, ''Complexes and First-Row Transition Elements'', Macmillan Press, London, 1973. # A.F. Wells, '''Structural Inorganic Chemistry'', 5th ed., Oxford University Press, Oxford, UK, 1984. # J. March, ''Advanced Organic Chemistry'', 4th ed., p. 723, Wiley, New York, 1992. # ''Handbook of Reagents for Organic Synthesis: Acidic and Basic Reagents'', (H. J. Reich, J. H. Rigby, eds.), Wiley, New York, 1999. [[Category:Chlorides]] [[Category:Iron compounds]] [[Category:Metal halides]] [[Category:Coordination compounds]] [[Category:Deliquescent substances]] [[ar:كلوريد حديد ثلاثي]] [[cs:Chlorid železitý]] [[de:Eisen(III)-chlorid]] [[es:Cloruro de hierro (III)]] [[fr:Chlorure de fer (III)]] [[id:Besi(III) klorida]] [[nl:IJzer(III)chloride]] [[ja:塩化鉄(III)]] [[pl:Chlorek żelaza(III)]] [[pt:Percloreto de ferro]] [[ru:Хлорид железа (III)]] [[fi:Ferrikloridi]] [[sv:Järnklorid]] [[zh:三氯化铁]]