Iron(III) chloride
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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: {{CASREF|CAS=10025-77-1}}
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| RTECS = LJ9100000
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| Section2 = {{Chembox Properties
| Formula = FeCl<sub>3</sub>
| MolarMass = 162.2 g·mol<sup>-1</sup>
| MolarMass_notes = <br/>hexahydrate: 270.3 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 g·cm<sup>−3</sup><br/>40% solution: 1.4 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 g/100 ml (20 °C)
| SolubleOther = 63 g/100 ml (18 °C)<br/>highly soluble<br/>83 g/100 ml<br/> highly soluble
| Solvent = [[acetone]]<br/>[[Methanol]]<br/>[[Ethanol]]<br/>[[Diethyl ether]]
| pKa =
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| Viscosity = 40% solution: 12 c[[Poise|P]]}}
| Section5 = {{Chembox Structure
| CrystalStruct = [[hexagonal]]
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| Coordination = [[octahedral]]
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| Section7 = {{Chembox Hazards
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| MainHazards = Very corrosive
| NFPA-H = 3
| NFPA-F =
| NFPA-R = 1
| NFPA-O =
| RPhrases = {{R22}}, {{R34}}
| SPhrases = {{S26}}, {{S28}}
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| 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 °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 °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 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 = 191–194 | year = 1950 | doi = 10.1002/9780470132340.ch51}}</ref>
:2 Fe([[solid|s]]) + 3 Cl<sub>2</sub>([[Gas|g]]) → 2 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 FeCl<sub>3</sub>(aq) → 3 FeCl<sub>2</sub>(aq)
#Dissolving [[iron ore]] in [[hydrochloric acid]]<br/>Fe<sub>3</sub>O<sub>4</sub>(s) + 8 HCl(aq) → FeCl<sub>2</sub>(aq) + 2 FeCl<sub>3</sub>(aq) + 4 H<sub>2</sub>O
#Upgrading the [[iron(II) chloride]] with [[chlorine]]<br/>2 FeCl<sub>2</sub>(aq) + Cl<sub>2</sub>(g) → 2 FeCl<sub>3</sub>(aq)
Alternatively, iron(II) chloride can be oxidised with [[sulfur dioxide]]:
:32 FeCl<sub>2</sub> + 8 SO<sub>2</sub> + 32 HCl → 32 FeCl<sub>3</sub> + S<sub>8</sub> + 16 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 = 321–323 | 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]]