Calcium chloride
Calcium chloride (or Calcium dichloride, Calcium(II) chloride).

Chemical formula : CaCl2 (anhydrous)
(Cl = 63,89 %, Ca = 36,11 %, )
Molar mass = 110,984 ± 0,008 g·mol-1

The anhydrous salt is a very hygroscopic white powder.
It is deliquescent; it can accumulate enough water in its crystal lattice to form a solution.

Calcium chloride crystallizes from water to form three different hydrates:

It is mainly obtained from chalk (calcium carbonate formed).
For example it may be prepared by reacting calcium carbonate [CaCO3] and hydrochloric solution [HCl] acid:

CaCO3 + 2 HCl >>> CaCl2 + H2O + CO2

Calcium chloride can be produced directly from limestone, but large amounts are also produced as a by product of the Solvay process.

This is a very hygroscopic material should be stored in tightly closed containers. It is prized for its exothermic qualities.
It behaves like a typical halide salt, in particular with a good electrical conductivity in the liquid state and ionic chemical bonds.

In water treatment, it is used by injection in the form of water solutions (saturated or not).

The most widely used commercial solutions are:

  1. 33% or 17.7 g / L (density 1.33 - crystallization temperature - 30 ° C)
  2. 42% or 34.1 g / L (density 1.41 - crystallization temperature + 18 ° C of )

Main Features :

Anhydrous form
% CaCl2
>96 %
Volumetric mass density (20°C)   
2150 kg/m3
Melting point
Solubility at 20°C
745 g/L

Solubility of anhydrous calcium chloride in water (soft) depending on the temperature (CaCl2 g / kg of H2O):

The dissolution process is exothermic and above 60 °C can be reached rapidly.
Due to its very hygroscopic nature, it can be used to dry the air, gas or other body fluids (or seeds).
When it absorbs water or water vapor of the substance to be dried, it is transformed into brine:

CaCl2 + 2 H2O >>> CaCl2.2H2O

A formulation for water treatment.
Injection of 11.1 mg of CaCl2 in 1 liter of pure water, calcium hardness (calcium) increases by 4 mg/L of calcium (or 1°F).

Standard products used for the production of drinking water: French Official Bulletin - Calcium chloride


Calcium chloride is irritating. It should be handled with gloves. It is relatively safe to handle, but it should not be ingested, it reacts exothermically with water, it can cause burning of the mouth or esophagus.

Sources : personal and Wikipedia, the free encyclopedia.

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