Chromium(III) sulfate

Chromium(III) sulfate
IUPAC name Chromium(III) sulfate
Other names Basic chromium sulfate, chromic sulfate
Identifiers
CAS number	10101-53-8 Y,  13520-66-6 (dodecahydrate)
ChemSpider	19951509 Y
UNII	Y0C99N5TMZ Y
Jmol-3D images	Image 1
SMILES [Cr+2].[Cr+2].[O-]S(=O)(=O)[O-].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O
InChI InChI=1S/2Cr.3H2O4S/c;;3*1-5(2,3)4/h;;3*(H2,1,2,3,4)/q2*+2;;;/p-6 Y Key: LPRGTYRWAKBNSY-UHFFFAOYSA-H Y InChI=1/2Cr.3H2O4S/c;;3*1-5(2,3)4/h;;3*(H2,1,2,3,4)/q2*+2;;;/p-6 Key: LPRGTYRWAKBNSY-CYFPFDDLAG
Properties
Molecular formula	H24Cr2S3O24
Molar mass	392.16 g/mol 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°C
Boiling point	decomposes at red heat
Solubility in water	insoluble (anhydrous) soluble (hydrates)
Hazards
MSDS	MSDS
EU Index	Not listed
NFPA 704	0 1 0
Flash point	Non-flammable
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Chromium(III) sulfate usually refers to the inorganic compound with the formula Cr₂(SO₄)₃ • 12(H₂O). This consists of the hydrated sulfate salt of the metal aquo complex with the formula [Cr(H₂O)₆]³⁺, which is responsible for the purple color of this salt. It is widely used in the tanning of leather, with associated environmental damage.^{[citation needed]}

Properties

Heating chromium(III) sulfate leads to partial dehydration to give a hydrated green salt (CAS#10031-37-5) and eventually the anhydrous derivative (CAS#10101-53-8).

Production

Basic chromium sulfate is produced from chromate salts by reduction with sulfur dioxide, although other methods exist.^[1] The hydrous form may be formed by the reaction of chromium(III) oxide and sulfuric acid.

Cr₂O₃ + 3 H₂SO₄ → Cr₂(SO₄)₃ + 3 H₂O

References

1. ^ Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger (2005), "Chromium Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a07_067