Cadmium chloride

Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl2•H2O and the hemipenahydrate CdCl2•2.5H2O.[2]

Cadmium chloride
Ball-and-stick model of cadmium chloride
Ball-and-stick model of cadmium chloride
Cadmium chloride in polyhedron shape
Cadmium chloride in polyhedron shape
Cadmium chloride hemipentahydrate
Names
IUPAC name
Cadmium dichloride
Other names
Cadmium(II) chloride
Identifiers
3D model (JSmol)
3902835
ChEBI
ChemSpider
ECHA InfoCard 100.030.256
EC Number
  • 233-296-7
  • (hemipentahydrate): 813-696-3
912918
KEGG
RTECS number
  • EV0175000
UNII
UN number 2570
  • InChI=1S/Cd.2ClH/h;2*1H/q+2;;/p-2 checkY
    Key: YKYOUMDCQGMQQO-UHFFFAOYSA-L checkY
  • InChI=1/Cd.2ClH/h;2*1H/q+2;;/p-2
    Key: YKYOUMDCQGMQQO-NUQVWONBAG
  • (hemipentahydrate): InChI=1S/2Cd.4ClH.5H2O/h;;4*1H;5*1H2/q2*+2;;;;;;;;;/p-4
    Key: DZVRGWYMCGLNKJ-UHFFFAOYSA-J
  • (monohydrate): InChI=1S/Cd.2ClH.H2O/h;2*1H;1H2/q+2;;;/p-2
    Key: OISMQLUZKQIKII-UHFFFAOYSA-L
  • [Cd+2].[Cl-].[Cl-]
  • (hemipentahydrate): O.O.O.O.O.[Cl-].[Cl-].[Cl-].[Cl-].[Cd+2].[Cd+2]
  • (monohydrate): O.[Cl-].[Cl-].[Cd+2]
Properties
CdCl2
Molar mass 183.31 g·mol−1
Appearance White solid, hygroscopic
Odor Odorless
Density 4.047 g/cm3 (anhydrous)[1]
3.26 g/cm3 (monohydrate)
3.327 g/cm3 (Hemipentahydrate)[2]
Melting point 568 °C (1,054 °F; 841 K) [2]
Boiling point 964 °C (1,767 °F; 1,237 K) [2]
Hemipentahydrate:
79.5 g/100 mL (−10 °C)
90 g/100 mL (0 °C)
Monohydrate:
119.6 g/100 mL (25 °C)[2]
134.3 g/100 mL (40 °C)
134.2 g/100 mL (60 °C)
147 g/100 mL (100 °C)[3]
Solubility Soluble in alcohol, selenium(IV) oxychloride, benzonitrile
Insoluble in ether, acetone[1]
Solubility in pyridine 4.6 g/kg (0 °C)
7.9 g/kg (4 °C)
8.1 g/kg (15 °C)
6.7 g/kg (30 °C)
5 g/kg (100 °C)[1]
Solubility in ethanol 1.3 g/100 g (10 °C)
1.48 g/100 g (20 °C)
1.91 g/100 g (40 °C)
2.53 g/100 g (70 °C)[1]
Solubility in dimethyl sulfoxide 18 g/100 g (25 °C)[1]
Vapor pressure 0.01 kPa (471 °C)
0.1 kPa (541 °C)[2]
−6.87·10−5 cm3/mol[2]
Viscosity 2.31 cP (597 °C)
1.87 cP (687 °C)[1]
Structure
Rhombohedral, hR9 (anhydrous)[4]
Monoclinic (hemipentahydrate)[3]
R3m, No. 166 (anhydrous)[4]
3 2/m (anhydrous)[4]
a = 3.846 Å, c = 17.479 Å (anhydrous)[4]
α = 90°, β = 90°, γ = 120°
Thermochemistry
74.7 J/mol·K[2]
115.3 J/mol·K[2]
−391.5 kJ/mol[2]
−343.9 kJ/mol[2]
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard[5]
Danger
H301, H330, H340, H350, H360, H372, H410[5]
P210, P260, P273, P284, P301+P310, P310[5]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
4
0
0
Lethal dose or concentration (LD, LC):
94 mg/kg (rats, oral)[1]
60 mg/kg (mouse, oral)
88 mg/kg (rat, oral)[6]
NIOSH (US health exposure limits):
PEL (Permissible)
 [1910.1027] TWA 0.005 mg/m3 (as Cd)[7]
REL (Recommended)
 Ca[7]
IDLH (Immediate danger)
 Ca [9 mg/m3 (as Cd)][7]
Safety data sheet (SDS) External MSDS
Related compounds
Other anions
 Cadmium fluoride
Cadmium bromide
Cadmium iodide
Other cations
 Zinc chloride
Mercury(II) chloride
Calcium chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Structure

Anhydrous

Anhydrous cadmium chloride forms a layered structure consisting of octahedral Cd2+ centers linked with chloride ligands. Cadmium iodide, CdI2, has a similar structure, but the iodide ions are arranged in a HCP lattice, whereas in CdCl2 the chloride ions are arranged in a CCP lattice.[8][9]

Hydrates

The anhydrous form absorbs moisture from the air to form various hydrates. Three of these hydrates have been examined by X-ray crystallography.

Crystallographic data for the 3 hydrates of cadmium chloride
Compound CdCl2·H2O[10] CdCl2·2.5H2O[11] CdCl2·4H2O[12]
Molar mass (g/mol) 201.33 228.36 255.38
Crystal Structure Orthorhombic Monoclinic Orthorhombic
Space Group Pnma P21/n P212121
Lattice constant a (Å) 9.25 9.21 12.89
Lattice constant b (Å) 3.78 11.88 7.28
Lattice constant c (Å) 11.89 10.08 15.01
β 93.5°
Density (g/cm3) 3.26 2.84 2.41
Comment Interconnected CdCl3(H2O) octahederons Distorted trans-[CdCl2(H2O)4] octahedrons

Chemical properties

Cadmium chloride dissolves well in water and other polar solvents. It is a mild Lewis acid.[8]

CdCl2 + 2 Cl− → [CdCl4]2−

Solutions of equimolar cadmium chloride and potassium chloride give potassium cadmium trichloride.[13] With large cations, it is possible to isolate the trigonal bipyramidal [CdCl5]3− ion.

Cadmium metal is soluble in molten cadmium chloride, produced by heating cadmium chloride above 568 °C. Upon cooling, the metal precipitates.[14]

Preparation

Anhydrous cadmium chloride can be prepared by the reaction of hydrochloric acid and cadmium metal or cadmium oxide.[14]

Cd + 2 HCl → CdCl2 + H2

The anhydrous salt can also be prepared from anhydrous cadmium acetate using hydrogen chloride or acetyl chloride.[15]

Industrially, it is produced by the reaction of molten cadmium and chlorine gas at 600 °C.[14]

The monohydrate, hemipentahydrate, and tetrahydrate can be produced by evaporation of the solution of cadmium chloride at 35, 20, and 0 °C respectively. The hemipentahydrate and tetrahydrate release water in air.[10][11][12]

Uses

Cadmium chloride is used for the preparation of cadmium sulfide, used as "cadmium yellow", a brilliant-yellow stable inorganic pigment.[14]

CdCl
2 + H
2S → CdS + 2 HCl

In the laboratory, anhydrous CdCl2 can be used for the preparation of organocadmium compounds of the type R2Cd, where R is an aryl or a primary alkyl. These were once used in the synthesis of ketones from acyl chlorides:[16]

CdCl
2 + 2 RMgX → R
2Cd + MgCl
2 + MgX
2
R
2Cd + 2R'COCl → 2R'COR + CdCl
2

Such reagents have largely been supplanted by organocopper compounds, which are much less toxic.

Cadmium chloride is also used for photocopying, dyeing and electroplating.

Like all cadmium compounds, CdCl
2 is highly toxic and appropriate safety precautions must be taken when handling it.

References
  1. Anatolievich, Kiper Ruslan. "cadmium chloride". chemister.ru. Retrieved 2014-06-25.
  2. Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
  3. Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). New York: D. Van Nostrand Company. p. 169.
  4. "Cadmium Chloride - CdCl2". chem.uwimona.edu.jm. Mona, Jamaica: The University of the West Indies. Retrieved 2014-06-25.
  5. Sigma-Aldrich Co., Cadmium chloride. Retrieved on 2014-05-23.
  6. "Cadmium compounds (as Cd)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  7. NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH).
  8. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
  9. A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
  10. H. Leligny; J. C. Monier (1974). "Structure cristalline de CdCl2.H2O" [Crystal structure of CdCl2.H2O]. Acta Crystallographica B (in French). 30 (2): 305–309. doi:10.1107/S056774087400272X.
  11. H. Leligny; J. C. Monier (1975). "Structure de CdCl2.2,5H2O" [Structure of CdCl2.2,5H2O]. Acta Crystallographica B (in French). 31 (3): 728–732. doi:10.1107/S056774087500369X.
  12. H. Leligny; J. C. Monier (1979). "Structure de dichlorure de cadmium tétrahydraté" [Structure of cadmium dichloride tetrahydrate]. Acta Crystallographica B (in French). 35 (3): 569–573. doi:10.1107/S0567740879004179.
  13. F. Wagenknecht; R. Juza (1963). "Potassium cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1095.
  14. Karl-Heinz Schulte-Schrepping; Magnus Piscator (2000). "Cadmium and Cadmium Compounds". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). p. 472. doi:10.1002/14356007.a04_499. ISBN 9783527306732.
  15. F. Wagenknecht; R. Juza (1963). "Cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. pp. 1093–4.
  16. J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
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