Cadmium chloride is a white crystalline compound of

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

and

chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

, with the formula CdCl₂. This salt is a

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

solid that is highly soluble in water and slightly soluble in

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

. The

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl₂•H₂O and the hemipentahydrate CdCl₂•2.5H₂O.

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

ions are arranged in a CCP lattice.N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.

Hydrates

The anhydrous form absorbs moisture from the air to form various

hydrates In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

. Three of these hydrates have been examined by

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

Chemical properties

Cadmium chloride dissolves well in water and other polar solvents. It is a mild

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

. :CdCl₂ + 2 Cl⁻ → dCl₄sup>2− Solutions of equimolar cadmium chloride and potassium chloride give potassium cadmium trichloride. With large cations, it is possible to isolate the trigonal bipyramidal dCl₅sup>3− ion. Cadmium metal is soluble in molten cadmium chloride, produced by heating cadmium chloride above 568 °C. Upon cooling, the metal precipitates.

Preparation

Anhydrous cadmium chloride can be prepared by the reaction of

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

and cadmium metal or

cadmium oxide Cadmium oxide is an inorganic compound with the formula CdO. It is one of the main precursors to other cadmium compounds. It crystallizes in a cubic rocksalt lattice like sodium chloride, with octahedral cation and anion centers. It occurs natur ...

. : Cd + 2 HCl → CdCl₂ + H₂ The anhydrous salt can also be prepared from anhydrous cadmium acetate using hydrogen chloride or acetyl chloride. Industrially, it is produced by the reaction of molten cadmium and

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

gas at 600 °C. 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.

Uses

Cadmium chloride is used for the preparation of cadmium sulfide, used as "

cadmium yellow Cadmium pigments are a class of pigments that contain cadmium. Most of the cadmium produced worldwide has been for use in rechargeable nickel–cadmium batteries, which have been replaced by other rechargeable nickel-chemistry cell varieties ...

", a brilliant-yellow stable inorganic

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

. : + → + 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 In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...

or a primary

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...

. These were once used in the synthesis of

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

s from

acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s:J. March, ''Advanced Organic Chemistry'', 4th ed., p. 723, Wiley, New York, 1992. : + 2 RMgX → + + : + 2R'COCl → 2R'COR + Such reagents have largely been supplanted by organocopper compounds, which are much less toxic. Cadmium chloride is also used for

photocopying A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopiers ...

, dyeing and

electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...

. It was used in the first experience for detecting neutrinos, the Cowan–Reines neutrino experiment. Like all cadmium compounds, is highly toxic and appropriate safety precautions must be taken when handling it.

References

External links

International Chemical Safety Card 0116

{{Chlorides Cadmium compounds Chlorides Metal halides IARC Group 1 carcinogens