Chromium(III) sulfate

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Chromium(III) sulfate
Chromium(III) sulfate.jpg
Cr(III)(aq)6)sulfate.svg
Names
IUPAC name
Chromium(III) sulfate
Other names
Basic chromium sulfate, chromic sulfate
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.217 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-253-2
PubChem CID
UNII
UN number 2240 3077
  • 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 X mark.svgN
    Key: ANNXSSGQVXBUEI-UHFFFAOYSA-H X mark.svgN
  • InChI=1/2Cr.3H2O4S.12H2O/c;;3*1-5(2,3)4;;;;;;;;;;;;/h;;3*(H2,1,2,3,4);12*1H2/q2*+3;;;;;;;;;;;;;;;/p-6
    Key: ANNXSSGQVXBUEI-CYFPFDDLAL
  • anhydrous:[Cr+3].[Cr+3].[O-]S(=O)(=O)[O-].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O
  • dodecahydrate:[OH2+][Cr-3]([OH2+])([OH2+])([OH2+])([OH2+])[OH2+].[OH2+][Cr-3]([OH2+])([OH2+])([OH2+])([OH2+])[OH2+].[O-]S(=O)(=O)[O-].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O
Properties
Cr2(SO4)3 • 12H2O
Molar mass 392.16 g/mol
608.363 g/mol (dodecahydrate)

716.45 g/mol (octadecahydrate)

Appearancereddish-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 °C
Boiling point >700 °C (decomposes to chromic acid)
insoluble (anhydrous)
soluble (hydrated)
Solubility soluble in alcohol
practically insoluble in acid
+11,800·10−6 cm3/mol
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Warning
H314, H317, H332, H334, H335, H340, H350, H373, H412
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, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Flash point Non-flammable
NIOSH (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) MSDS
Related compounds
Other cations
Aluminium sulfate
Related double salts
Chrome alum
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.

Contents

Chromium(III) sulfates

Three chromium(III) sulfates are well characterized:

A variety of other chromium(III) 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). [3] It results from the partial neutralization of the hexahydrates. Other chromium(III) hydroxides have been reported. [4]

Structure of solid Cr(SO4)(H2O)(OH), showing the CrO6 coordination sphere typical of many chromium(III) compounds. Color code: red = O, yellow = S, dark blue = Cr. EntryWithCollCode26550.png
Structure of solid Cr(SO4)(H2O)(OH), showing the CrO6 coordination sphere typical of many chromium(III) compounds. Color code: red = O, yellow = S, dark blue = Cr.

Production

Chromium(III) sulfate are commonly obtained from the wastes of chromate oxidations of various organic compounds. Anthraquinone and quinone are produced on large scale by the x treatment of respectively anthracene and phenol with chromic acid. A chromium(III) oxide byproduct is generated, which is readily extracted into sulfuric acid. Evaporation of these acidic solutions affords salts if hydrate chromium(III) sulfate. 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(III) sulfate together with ferrous sulfate. [5]

Basic chromium(III) sulfate

Basic chromium sulfate is produced from chromate salts by reduction with sulfur dioxide, although other methods exist. [5] [6] 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.

Natural occurrence

Three complex minerals that are in part Cr(III) sulfates: bentorite, reddingtonite, and putnisite. [7] [8] [9] [10]

References

  1. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).
  2. Dahmen, Thomas; Gruehn, Reginald (1993) [16 Dec 1991]. "Beiträge zum thermischen Verhalten von Sulfaten IX. Einkristallstrukturverfeinerung der Metall(III)-sulfate Cr2(SO4)3 und Al2(SO4)3" [Contributions to the thermal dynamics of sulfates IX: Single-crystal refinement of the metal(III) sulfates Cr2(SO4)3 and Al2(SO4)3](PDF). Zeitschrift für Kristallographie (in German). 204. Munich: R. Oldenbourg Verlag: 57–65.
  3. 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
  4. Riou, A.; Bonnin, A. (1982). "Structure de l'Hydroxysulfate de Chrome monohydrate". Acta Crystallographica B. 24 (5): 1968–38. doi: 10.1107/S0567740881005001 .
  5. 1 2 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. ISBN   978-3-527-30673-2.
  6. CW Harland; J Simpson. "Chromium sulfate tanning powder" (PDF). Farmers Fertiliser Ltd - a subsidiary of Fernz Corporation Ltd. Archived from the original (PDF) on 2018-01-27. Retrieved 2016-08-04.
  7. "Bentorite".
  8. "Redingtonite".
  9. "Putnisite".
  10. "List of Minerals". 21 March 2011.