Potassium Chloride KCl

Preparation

(i) It occurs naturally, mainly as carnallite, KCl.MgCl₂.6H₂O from which it is extracted by fractional crystallization.

(ii) Besides NaCl and chlorides and sulphates of calcium and magnesium, sea water also contains KCl. In fact, sea water is the main source of KCl. Sea water is evaporated to dryness and then KCl is obtained from it by fractional crystallization. A plant to obtain KCl from sea water has been set up on a semi−commercial scale in Kandla (Gujrat state).

(iii) It can also be obtained from sylvine, which is a mixture of NaCl and KCl. The hot concentrated solution of sylvine is allowed to cool when KCl being less soluble crystallizes out first leaving behind NaCl in the solution.

Properties

(i) It is a colourless, crystalline solid which melts at 1063 K.

(ii) It is soluble in water and its solubility increases with rise in temperature

Uses

(i) The chief use of KCl is as a fertilizer.

(ii) It is also used for the preparation of many other salts of potassium such as KNO₃, K₂SO₄, K₂CO₃, KOH etc.