Chromium(III) hydroxide

Chromium(III) hydroxide is a gelatinous green inorganic compound with the chemical formula Cr(OH)3. It is a polymer with an undefined structure and low solubility. It is amphoteric, dissolving in both strong alkalis and strong acids.[2]

In alkali: Cr(OH)3 + OHCrO
2
+ 2 H2O
In acid: Cr(OH)3(OH2)3 + 3 H+Cr(OH
2
)3+
6
Chromium(III) hydroxide
Names
IUPAC name
Chromium(3+) hydroxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.013.781
RTECS number
  • GB2670000
UNII
Properties
Cr(OH)3
Molar mass 103.02 g/mol
Appearance green, gelatinous precipitate
Density 3.11 g/cm3
insoluble
Hazards
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]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

It is used as a pigment, as a mordant, and as a catalyst for organic reactions.[3]

It is manufactured by adding a solution of ammonium hydroxide to a solution of chromium salt.

Pure Cr(OH)3 is as yet (2020) unknown among the mineral species. However, three natural polymorphs of the oxyhydroxide, CrO(OH), are known: bracewellite, grimaldiite and guyanaite.[4][5][6][7]

References

  1. NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).
  2. Rai, Dhanpat; Sass, Bruce M.; Moore, Dean A. "Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide" Inorganic Chemistry 1987, volume 26, pp. 345-9. doi:10.1021/ic00250a002
  3. Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Chromium". Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 1081–1095. ISBN 3-11-007511-3.
  4. https://www.mindat.org/min-748.html
  5. https://www.mindat.org/min-1750.html
  6. https://www.mindat.org/min-1783.html
  7. https://www.ima-mineralogy.org/Minlist.htm
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