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)
PubChem	24930
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 to chromic acid
Solubility in water	insoluble (anhydrous) soluble (hydrated)
Solubility	soluble in alcohol practically insoluble in acid
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. The hydrous form may be formed by the reaction of chromium(III) oxide and sulfuric acid.

Cr₂O₃ + 3 H₂SO₄ → Cr₂(SO₄)₃ + 3 H₂O