chromium(III) hydroxide

{{Short description|Chemical compound (Cr(OH)3)}}

{{Chembox

| ImageFile = Chromium(III) hydroxide.svg

| ImageSize = 100

| IUPACName = Chromium(3+) hydroxide

| OtherNames =

| Section1 = {{Chembox Identifiers

| CASNo = 1308-14-1

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = DX3N9U5Q97

| PubChem = 166720

| RTECS = GB2670000

| ChemSpiderID = 145861

| SMILES = [OH-].[OH-].[OH-].[Cr+++]

| SMILES_Comment = ionic form

| SMILES1 = O[Cr](O)O

| SMILES1_Comment = coordination form

| InChI = 1S/Cr.3H2O/h;3*1H2

| InChIKey = LXMQZGGLHVSEBA-UHFFFAOYSA-N

| StdInChI =

| StdInChIKey =

}}

| Section2 = {{Chembox Properties

| Formula = {{chem2|Cr(OH)3}}

| Cr=1|O=3|H=3

| Appearance = green, gelatinous precipitate

| Density = 3.11 g/cm³

| MeltingPt =

| BoilingPt =

| Solubility =insoluble

| SolubleOther =

}}

| Section3 = {{Chembox Hazards

| MainHazards =

| FlashPt =

| AutoignitionPt =

| PEL = TWA 1 mg/m³{{PGCH|0141}}

| REL = TWA 0.5 mg/m³

| IDLH = 250 mg/m³

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Chromium(III) hydroxide is a gelatinous green inorganic compound with the chemical formula {{chem2|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.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}}

:In alkali: {{chem2|Cr(OH)3 + OH- → CrO2- + 2 H2O}}

:In acid: {{chem2|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.{{Cite book|publisher = Walter de Gruyter|year = 1985|edition = 91–100|pages = 1081–1095|isbn = 3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first = Arnold F.|last = Holleman |author2=Wiberg, Egon |author3=Wiberg, Nils|chapter = Chromium| language = German}}

It is manufactured by adding a solution of ammonium hydroxide to a solution of chromium salt.{{cn|date=September 2023}}

Pure {{chem2|Cr(OH)3}} is as yet (2020) unknown among the mineral species. However, three natural polymorphs of the chromium(III) oxide hydroxide, CrO(OH), are known: bracewellite, grimaldiite and guyanaite.{{Cite web|url=https://www.mindat.org/min-748.html|title = Bracewellite}}{{Cite web|url=https://www.mindat.org/min-1750.html|title=Grimaldiite}}{{Cite web|url=https://www.mindat.org/min-1783.html|title=Guyanaite}}{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}