Chromium (III) potassium sulfate dodecahydrate

Structural formula
General
Surname	Chromium (III) potassium sulfate dodecahydrate
other names	Chrome alum; Chromium Potassium Sulphate; Potassium Chromium (III) Sulphate Dodecahydrate;
Molecular formula	KCr (SO 4 ) 2 • 12 H 2 O
Brief description	odorless dark purple crystalline powder
External identifiers / databases
EC number	616-539-5
ECHA InfoCard	100.107.249
PubChem	24596
Wikidata	Q27279646
properties
Molar mass	499.25 g mol −1
Physical state	firmly
density	1.83 g cm −3 (20 ° C)
Melting point	89 ° C
solubility	easily in water (250 g l −1 at 25 ° C)
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 315-319
	P: 302 + 352-305 + 351 + 338
Toxicological data	> 3500 mg kg −1 ( LD 50 , rat , oral )
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Chromium (III) potassium sulfate dodecahydrate (also chromium alum , chromium potassium sulfate or potassium chromium (III) sulfate dodecahydrate ) is a crystalline compound consisting of the elements chromium , potassium , sulfur and oxygen , with the hydrate additionally hydrogen . The compound belongs to the group of alums . An anhydrous chromium (III) potassium sulfate is also known.

Potassium aluminum alum doped with chromium: rhombic dodecahedron surfaces are indicated along the edges of the octahedron.
The same crystal with a view of the triangular surfaces ...
... and from above.

Extraction and presentation

pure potassium chrome alum

Chromium potassium sulfate is obtained from the reaction of potassium dichromate and sulfuric acid. The reducing agent used is ethanol in excess, which is oxidized to acetaldehyde .

{\ displaystyle {\ ce {K2Cr2O7 + 3CH3CH2OH + 4H2SO4 + 5H2O -> 2KCr (SO4) 2.12H2O + 3CH3CHO}}}

use

Chromium (III) dodecahydrate -kaliumsulfat becomes the tanning of leather used. Since it forms well-formed large crystals from aqueous solution very easily, it is often used for crystal growth .

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on chrome alum in the GESTIS substance database of the IFA , accessed on February 18, 2017(JavaScript required) .
↑ External identifiers or database links to chromium (III) potassium sulfate anhydrate : CAS number: 10141-00-1, EC number: 233-401-6 , ECHA InfoCard: 100.030.352 , GESTIS substance database : 3690 , PubChem : 61489 , ChemSpider : 19968602 , Wikidata : Q425240 .
^ DV West, Q. Huang, HW Zandbergen, TM McQueen, RJ Cava: Structural disorder, octahedral coordination and two-dimensional ferromagnetism in anhydrous alums. in: Journal of Solid State Chemistry , 181 (10), 2008, pp. 2768-2775, doi: 10.1016 / j.jssc.2008.07.006 .
↑ Jander / Blasius: Inorganic Chemistry ll Quantitative Analysis & Preparations . Ed .: Eberhard Schweda. 16th edition. Hirzel Verlag, Stuttgart, ISBN 978-3-7776-2133-3 .

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on chrome alum in the GESTIS substance database of the IFA , accessed on February 18, 2017(JavaScript required) .

[2] External identifiers or database links to chromium (III) potassium sulfate anhydrate : CAS number: 10141-00-1, EC number: 233-401-6 , ECHA InfoCard: 100.030.352 , GESTIS substance database : 3690 , PubChem : 61489 , ChemSpider : 19968602 , Wikidata : Q425240 .

[3] DV West, Q. Huang, HW Zandbergen, TM McQueen, RJ Cava: Structural disorder, octahedral coordination and two-dimensional ferromagnetism in anhydrous alums. in: Journal of Solid State Chemistry , 181 (10), 2008, pp. 2768-2775, doi: 10.1016 / j.jssc.2008.07.006 .

[4] Jander / Blasius: Inorganic Chemistry ll Quantitative Analysis & Preparations . Ed .: Eberhard Schweda. 16th edition. Hirzel Verlag, Stuttgart, ISBN 978-3-7776-2133-3 .