Chromium(III) hydroxide

Chromium(III) hydroxide
Names
	IUPAC name Chromium(3+) hydroxide
Identifiers
CAS Number	1308-14-1 ;
3D model (JSmol)	ionic form: Interactive image; coordination form: Interactive image;
ECHA InfoCard	100.013.781
PubChem CID	14787;
RTECS number	GB2670000;
UNII	DX3N9U5Q97 ;
CompTox Dashboard (EPA)	DTXSID0051651 ;
	InChI InChI=1S/Cr.3H2O/h;3*1H2 Key: LXMQZGGLHVSEBA-UHFFFAOYSA-N;
	SMILES ionic form: [OH-].[OH-].[OH-].[Cr+++]; coordination form: O[Cr](O)O;
Properties
Chemical formula	Cr(OH)3
Molar mass	103.02 g/mol
Appearance	green, gelatinous precipitate
Density	3.11 g/cm3
Solubility in water	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

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:

{\ce {Cr(OH)3 + OH- -> CrO2- + 2 H2O}}

In acid:

{\ce {Cr(OH)3(OH2)3 + 3 H+ -> Cr(OH2)6^3+}}

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

NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).
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
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.
"Bracewellite".
"Grimaldiite".
"Guyanaite".
"List of Minerals". 21 March 2011.

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[PGCH-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

[HollemanAF-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] "Bracewellite".

[5] "Grimaldiite".

[6] "Guyanaite".

[7] "List of Minerals". 21 March 2011.