Chromium(III) sulfate usually refers to the inorganic compounds with the formula Cr2(SO4)3.x(H2O), where x can range from 0 to 18. Additionally, ill-defined but commercially important "basic chromium sulfates" are known. These salts are usually either violet or green solids that are soluble in water. It is commonly used in tanning leather.
Three chromium(III) sulfates are well characterized:
Anhydrous chromium(III) sulfate, Cr2(SO4)3, (CAS #10101-53-8) is a violet solid that dissolves in water upon addition of a reducing agent, which generates chromium(II) sulfates.
Hydrated chromium(III) sulfate, Cr2(SO4)3·18H2O, (CAS #13520-66-6) is a violet solid that readily dissolves in water to give the metal aquo complex, [Cr(H2O)6]3+. The formula of this compound can be written more descriptively as [Cr(H2O)6]2(SO4)3·6H2O. Six of the eighteen water molecules in this formula unit are water of crystallization.
Hydrated chromium(III) sulfate, Cr2(SO4)3·15(H2O), (CAS #10031-37-5) is a green solid that also readily dissolves in water. It is obtained by heating the 18-hydrate material above 70 °C. Further heating yields the anhydrous sulfate.
A variety of other chromium(VI) sulfates are known, but also contain hydroxide or oxide ligands. Most important commercially is basic chromium sulfate, which is thought to be [Cr2(H2O)6(OH)4]SO4 (CAS#39380-78-4).[2] It results from the partial neutralization of the hexahydrates. Other chromium(III) hydroxides have been reported.[3]
Structure of Cr(SO4)(H2O)(OH), showing the CrO6 coordination sphere typical of many chromium(III) compounds.
Production
The most useful source of chromium(III) sulfate are the Cr(III) wastes from the chromate oxidation of various organic compounds. Anthroquinone and quinone are produced on large scale by treatment of anthracene and phenol with chromic acid. A chromium(III) oxide coproduct is generated which is readily extracted into sulfuric acid. Evaporation of these acidic solutions affords the hydrate salt described above. The hydrated salts of chromium sulfate can also be produced, albeit impure, by extraction of various other chromium compounds, but these routes are not economically viable.. Extraction of chromite ore with sulfuric acid in the presence of some chromate gives solutions of chromium(III) sulfate contaminated with other metal ions. Similarly, dissolution of chrome alloys gives chromium sulfate together with ferrous sulfate.[citation needed]
Basic chromium(III) sulfate
Basic chromium sulfate is produced from chromate salts by reduction with sulfur dioxide, although other methods exist.[4][5] The reduction could formally be written:
Na2Cr2O7 + 3 SO2 + H2O → Cr2(SO4)3 + 2 NaOH
Since 33% of the anion charges are due to hydroxy ions the basicity is 33% (but in tanning jargon it is known as 33% reduced). Products with higher basicities, e.g. 42% or 50% may be obtained by the addition of sodium carbonate, these are often used in combination with sodium formate. The sodium sulfate is often left in the technical product since it is inert with respect to the tanning process. It is important to fully reduce the hexavalent chromium to trivalent since the hexavalent is more likely to cause health problems for tanners and leather consumers.[citation needed]
Natural occurrence
Pure chromium(III) sulfate, both in anhydrous and hydrous form, is as yet (2020) unknown among mineral species. There are 3 complex minerals being, in part, Cr(III) sulfates: bentorite, reddingtonite, and ptnisite.[6][7][8][9]
^Covington, A. D.; Lampard, G. S.; Menderes, O.; Chadwick, A. V.; Rafeletos, G.; O'Brien, P. "Extended X-ray absorption fine structure studies of the role of chromium in leather tanning" Polyhedron 2001, volume 20, 461–466. doi:10.1016/S0277-5387(00)00611-2
^Riou, A.; Bonnin, A. (1982). "Structure de l'Hydroxysulfate de Chrome monohydrate". Acta Crystallographica B. 24 (5): 1968–38. doi:10.1107/S0567740881005001.
^Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger. "Chromium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_067.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
^CW Harland; J Simpson. "Chromium sulfate tanning powder" (PDF). Farmers Fertiliser Ltd - a subsidiary of Fernz Corporation Ltd.
chromium, sulfate, usually, refers, inorganic, compounds, with, formula, where, range, from, additionally, defined, commercially, important, basic, chromium, sulfates, known, these, salts, usually, either, violet, green, solids, that, soluble, water, commonly,. Chromium III sulfate usually refers to the inorganic compounds with the formula Cr2 SO4 3 x H2O where x can range from 0 to 18 Additionally ill defined but commercially important basic chromium sulfates are known These salts are usually either violet or green solids that are soluble in water It is commonly used in tanning leather Chromium III sulfate NamesIUPAC name Chromium III sulfateOther names Basic chromium sulfate chromic sulfateIdentifiersCAS Number 10101 53 8 Y15244 38 9 decahydrate Y10031 37 5 pentadecahydrate Y13520 66 6 octadecahydrate N3D model JSmol Interactive imageChEBI CHEBI 53471ChemSpider 23304 YECHA InfoCard 100 030 217EC Number 233 253 2PubChem CID 24930UNII Y0C99N5TMZ Y8Q759N78CX decahydrate YE4T8TU3LE8 pentadecahydrate YUN number 2240 3077CompTox Dashboard EPA DTXSID20890642InChI InChI 1S 2Cr 3H2O4S 12H2O c 3 1 5 2 3 4 h 3 H2 1 2 3 4 12 1H2 q2 3 p 6 NKey ANNXSSGQVXBUEI UHFFFAOYSA H NInChI 1 2Cr 3H2O4S 12H2O c 3 1 5 2 3 4 h 3 H2 1 2 3 4 12 1H2 q2 3 p 6Key ANNXSSGQVXBUEI CYFPFDDLALSMILES Cr 3 Cr 3 O S O O O O S O O O O S O O O O O O O O O O O O O O OPropertiesChemical formula Cr2 SO4 3 12H2OMolar mass 392 16 g mol 608 363 g mol dodecahydrate 716 45 g mol octadecahydrate Appearance reddish brown crystals anhydrous purple crystals hydrated Density 3 10 g cm3 anhydrous 1 86 g cm3 pentadecahydrate 1 709 g cm3 octadecahydrate Melting point 90 CBoiling point gt 700 C decomposes to chromic acid Solubility in water insoluble anhydrous soluble hydrated Solubility soluble in alcohol practically insoluble in acidMagnetic susceptibility x 11 800 10 6 cm3 molHazardsGHS labelling PictogramsSignal word WarningHazard statements H314 H317 H332 H334 H335 H340 H350 H373 H412Precautionary statements P201 P202 P260 P261 P264 P271 P272 P273 P280 P281 P285 P301 P330 P331 P302 P352 P303 P361 P353 P304 P312 P304 P340 P304 P341 P305 P351 P338 P308 P313 P310 P312 P314 P321 P333 P313 P342 P311 P363 P403 P233 P405 P501NFPA 704 fire diamond 100Flash point Non flammableNIOSH US health exposure limits PEL Permissible TWA 1 mg m3 1 REL Recommended TWA 0 5 mg m3 1 IDLH Immediate danger 250 mg m3 1 Safety data sheet SDS MSDSRelated compoundsOther cations Aluminium sulfateRelated double salts Chrome alumExcept where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Chromium III sulfates 2 Production 2 1 Basic chromium III sulfate 3 Natural occurrence 4 ReferencesChromium III sulfates EditThree chromium III sulfates are well characterized Anhydrous chromium III sulfate Cr2 SO4 3 CAS 10101 53 8 is a violet solid that dissolves in water upon addition of a reducing agent which generates chromium II sulfates Hydrated chromium III sulfate Cr2 SO4 3 18H2O CAS 13520 66 6 is a violet solid that readily dissolves in water to give the metal aquo complex Cr H2O 6 3 The formula of this compound can be written more descriptively as Cr H2O 6 2 SO4 3 6H2O Six of the eighteen water molecules in this formula unit are water of crystallization Hydrated chromium III sulfate Cr2 SO4 3 15 H2O CAS 10031 37 5 is a green solid that also readily dissolves in water It is obtained by heating the 18 hydrate material above 70 C Further heating yields the anhydrous sulfate A variety of other chromium VI sulfates are known but also contain hydroxide or oxide ligands Most important commercially is basic chromium sulfate which is thought to be Cr2 H2O 6 OH 4 SO4 CAS 39380 78 4 2 It results from the partial neutralization of the hexahydrates Other chromium III hydroxides have been reported 3 Structure of Cr SO4 H2O OH showing the CrO6 coordination sphere typical of many chromium III compounds Production EditThe most useful source of chromium III sulfate are the Cr III wastes from the chromate oxidation of various organic compounds Anthroquinone and quinone are produced on large scale by treatment of anthracene and phenol with chromic acid A chromium III oxide coproduct is generated which is readily extracted into sulfuric acid Evaporation of these acidic solutions affords the hydrate salt described above The hydrated salts of chromium sulfate can also be produced albeit impure by extraction of various other chromium compounds but these routes are not economically viable Extraction of chromite ore with sulfuric acid in the presence of some chromate gives solutions of chromium III sulfate contaminated with other metal ions Similarly dissolution of chrome alloys gives chromium sulfate together with ferrous sulfate citation needed Basic chromium III sulfate Edit Basic chromium sulfate is produced from chromate salts by reduction with sulfur dioxide although other methods exist 4 5 The reduction could formally be written Na2Cr2O7 3 SO2 H2O Cr2 SO4 3 2 NaOHSince 33 of the anion charges are due to hydroxy ions the basicity is 33 but in tanning jargon it is known as 33 reduced Products with higher basicities e g 42 or 50 may be obtained by the addition of sodium carbonate these are often used in combination with sodium formate The sodium sulfate is often left in the technical product since it is inert with respect to the tanning process It is important to fully reduce the hexavalent chromium to trivalent since the hexavalent is more likely to cause health problems for tanners and leather consumers citation needed Natural occurrence EditPure chromium III sulfate both in anhydrous and hydrous form is as yet 2020 unknown among mineral species There are 3 complex minerals being in part Cr III sulfates bentorite reddingtonite and ptnisite 6 7 8 9 References Edit a b c NIOSH Pocket Guide to Chemical Hazards 0141 National Institute for Occupational Safety and Health NIOSH Covington A D Lampard G S Menderes O Chadwick A V Rafeletos G O Brien P Extended X ray absorption fine structure studies of the role of chromium in leather tanning Polyhedron 2001 volume 20 461 466 doi 10 1016 S0277 5387 00 00611 2 Riou A Bonnin A 1982 Structure de l Hydroxysulfate de Chrome monohydrate Acta Crystallographica B 24 5 1968 38 doi 10 1107 S0567740881005001 Gerd Anger Jost Halstenberg Klaus Hochgeschwender Christoph Scherhag Ulrich Korallus Herbert Knopf Peter Schmidt Manfred Ohlinger Chromium Compounds Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a07 067 a href Template Cite encyclopedia html title Template Cite encyclopedia cite encyclopedia a CS1 maint multiple names authors list link CW Harland J Simpson Chromium sulfate tanning powder PDF Farmers Fertiliser Ltd a subsidiary of Fernz Corporation Ltd Bentorite Redingtonite Putnisite List of Minerals 21 March 2011 Retrieved from https en wikipedia org w index php title Chromium III sulfate amp oldid 1077911102, wikipedia, wiki, book, books, library,
