Article: Calcium chloride

Calcium chloride
3155-200px-calcium-chloride-calcium-chloride.jpg
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 [10043-52-4], anhydrous
[10035-04-8], dihydrate
[25094-02-4], 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

3156-75px-nfpa-704-svg-calcium-chloride.png

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R-phrases R36
S-phrases S2, S22, S24
RTECS number EV9800000, anhydrous
EV9810000, dihydrate
EV9830000, hexahydrate
Supplementary data page
Structure & properties n, εr, 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)
Infobox disclaimer and references

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.
  • (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.

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