Chromium (III) chloride

Crystal structure
__ Cr 3+      __ Cl -
General
Surname	Chromium (III) chloride
other names	Chromium trichloride
Ratio formula	CrCl 3
Brief description	red-violet shiny leaves (anhydrous) green (hexahydrate)
External identifiers / databases
CAS number 10025-73-7 (anhydrous) 10060-12-5 (hexahydrate) EC number 233-038-3 ECHA InfoCard 100.030.023 PubChem 24808 ChemSpider 23193 DrugBank DB09129 Wikidata Q411885
properties
Molar mass	158.35 g mol −1 (anhydrous) 266.41 g mol −1 (hexahydrate)
Physical state	firmly
density	2.87 g cm −3
Melting point	1152 ° C (anhydrous) 80–83 ° C (hexahydrate)
solubility	anhydrous: sparingly soluble in water and ethanol Hexahydrate: 590 g / l in water
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 290-302-317-411 P: 273-280
Toxicological data	1870 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) chloride is the chromium salt of hydrochloric acid with the empirical formula CrCl ₃ . With water of hydration, it also crystallizes as chromium (III) chloride hexahydrate (CrCl ₃  · 6 H ₂ O).

Extraction and presentation

Chromium (III) chloride can be obtained by reacting chromium with chlorine.

${\displaystyle \mathrm {2\ Cr+3\ Cl_{2}\longrightarrow 2\ CrCl_{3}} }$

The anhydrous compound is accessible in the laboratory from the hexahydrate via its reaction with thionyl chloride or the chlorination of freshly produced chromium (III) oxide with carbon tetrachloride at 620 ° C:

${\displaystyle {\ce {CrCl3 * 6 H2O + 6 SOCl2 -> CrCl3 + 6 SO2 + 12 HCl}}}$

${\displaystyle {\ce {Cr2O3 + 3 CCl4 ->2 CrCl3 + 3 COCl2}}}$

properties

• 

  Chromium (III) chloride anhydrous

• 

  The hexahydrate [CrCl ₂ (H ₂ O) ₄ ] Cl · 2H ₂ O

It forms crystalline layer structures in which Van der Waals forces occur between the layers . The salt, which forms shiny red-violet crystals, is insoluble in water in its pure form and hardly soluble in ethanol . Only in the presence of traces of chromium (II) chloride (CrCl ₂ ) (or another reducing agent) is a catalytically dissolving process in water possible with strong heat emission. In solution, differently colored hydratisomeric aqua complexes can form, for example dark green dichlorotetraaquachrome (III) chloride, light green chloropentaaquachrome (III) chloride or violet hexaaquachrome (III) chloride. The following equilibria are established between these complexes:

${\displaystyle {\rm {[CrCl_{2}(H_{2}O)_{4}]Cl\rightleftarrows [CrCl(H_{2}O)_{5}]Cl_{2}\rightleftarrows [Cr(H_{2}O)_{6}]Cl_{3}}}}$

Manufacturing

Chromium (III) chloride can be synthesized from metallic chromium in a stream of chlorine at 600 ° C. Production from chromium (III) oxide and carbon in a chlorine stream above 1200 ° C is also possible.

use

Chromium (III) chloride is used as catalyst for the preparation of other chromium compounds, the chromium plating in the electroplating and waterproofing impregnation used.

Web links

Commons : Chromium (III) Chloride  - Collection of Pictures, Videos, and Audio Files

Individual evidence

1. ↑ ^{a b c} Entry on chromium chlorides. In: Römpp Online . Georg Thieme Verlag, accessed on May 29, 2013.
2. ^ ^{A b c d} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1573.
3. ↑ ^{a b c d e f g h} Entry on chromium (III) chloride in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
4. ↑ Georg Brauer (ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1481.
5. ^ Alfred R. Pray: Anhydrous metal chlorides . In: Therald Moeller (Ed.): Inorganic Syntheses . tape 5 . McGraw-Hill, Inc., 1957, pp. 153-156 (English).
6. ↑ A. Vavoulis et al .: Anhydrous chromium (III) chloride . In: Eugene G. Rochow (Ed.): Inorganic Syntheses . tape 6 . McGraw-Hill Book Company, Inc., 1960, pp. 129-132 (English).
7. ^ ^{A b} E. Riedel, C. Janiak: Inorganic Chemistry . 8th edition. de Gruyter, 2011, ISBN 3-11-022566-2 , p. 813 f .