Calcium chloride

Calcium chloride
General
Systematic name	calcium chloride
Other names	calcium(II) chloride, calcium dichloride
Molecular formula	CaCl₂
Molar mass	110.99 g/mol, anhydrous 147.02 g/mol, dihydrate 182.04 g/mol, tetrahydrate 219.08 g/mol, hexahydrate
Appearance	white or colourless solid
CAS number	anhydrous ^*," target="_blank" >tetrahydrate [7774-34-7, hexahydrate
Properties
Density and phase	2.15 g/cm³, anhydrous 0.835 g/cm³, dihydrate 1.71 g/cm³, hexahydrate
Solubility in water	74.5 g/100 ml (20 °C)
In ethanol In acetone In acetic acid	soluble
Melting point	772 °C (anhydrous)
Boiling point	>1600 °C
Vapour Pressure	11 hPa
Structure
Coordination geometry	octahedral, 6-coordinate
Crystal structure	deformed rutile
Hazards
MSDS	External MSDS
EU classification	Irritant (Xi)
NFPA 704
R-phrases
S-phrases	, ,
RTECS number	EV9800000, anhydrous EV9810000, dihydrate EV9830000, hexahydrate
Supplementary data page
Structure & properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	calcium fluoride calcium bromide calcium iodide
Other cations	magnesium chloride strontium chloride
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Chemical infobox

Calcium chloride is a chemical compound of calcium and chlorine. It is highly soluble in water and it is deliquescent. It is a salt that is solid at room temperature, and it behaves as a typical ionic halide. It has several common applications such as brine for refrigeration plants, ice and dust control on roads, and in cement. It can be produced directly from limestone, but large amounts are also produced as a by-product of the Solvay process. Because of its hygroscopic nature, it must be kept in tightly-sealed containers.

Chemical properties

Calcium chloride can serve as a source of calcium ions in solution, for instance for precipitation because many calcium compounds are insoluble:

3 CaCl₂(aq) + 2 K₃PO₄(aq) → Ca₃(PO₄)₂(s) + 6 KCl(aq)

Molten CaCl₂ can be electrolysed to give calcium metal:

CaCl₂(l) → Ca(s) + Cl₂(g)

Preparation

Calcium chloride is a by-product of the Solvay process used for the manufacture of sodium carbonate. It can also be produced by the action of hydrochloric acid on calcium carbonate | CaCO₃(s) + 2 HCl → CaCl₂(aq) + H₂O(l) + CO₂(g)

Uses

Millions of tonnes of calcium chloride are produced in the US alone, and in 1990 its bulk price there was $182 per tonne. It has a variety of applications:

Because it is strongly hygroscopic, it can be used to dry air as well as other gases and organic liquids. In the process, it is converted to a brine as it absorbs the water or water vapor from the substance to be dried:

CaCl₂ + 2 H₂O → CaCl₂·2H₂O

The dissolving process is highly exothermic and rapidly produces temperatures of around 60°C (140°F). This can result in chemical burns if humans or animals eat dry calcium chloride pellets. Small children are more susceptible to burns than adults, and calcium chloride pellets should be kept out of their reach.

Aided by the intense heat evolved during its dissolution, calcium chloride is also used as an ice-melting compound. Unlike the more-common sodium chloride (rock salt or halite), it is relatively harmless to plants and soil. It is also more effective at lower temperatures than sodium chloride. When distributed for this use, it usually takes the form of small white balls a few millimetres in diameter, called prills (see picture at top of page).

It is used in concrete mixes to help speed up the initial setting and to strengthen the concrete. However chloride ion leads to corrosion of steel rebars, so it should not be used in reinforced concrete.

It is used for dust control on some highways, as its hygroscopic nature keeps a liquid layer on the surface of the roadway, which holds dust down.

Calcium chloride tastes extremely salty and is used an ingredient in some foods, especially pickles, to give a salty taste while not increasing the food's sodium content.

Used as an additive in plastics.

Used as a drainage aid for wastewater treatment.

Aqueous Calcium Chloride is used in genetic transformation of cells by increasing the cell membrane permeability. This allows DNA fragments to enter the cell more readily.

(Tire ballast, additive in fire extinguishers, admixture with starch paste, additive to control scaffolding in blast furnaces, desiccant, brine, food processing agent, food additives, medication, additives in herbicide and pH regulating agent.

Precautions

Calcium chloride is an irritant; wear gloves and goggles to protect hands and eyes; avoid inhalation.

Although calcium chloride is relatively safe to handle, care should be taken that it is not ingested. Calcium chloride reacts exothermically with water and can burn the mouth and esophagus.

References

Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.

External links

Calcium compounds | Chlorides | Metal halides | Deliquescent substances