Sodium Chloride (Common Salt) NaCl

Sodium Chloride 

Sodium chloride is the most common of the salts of sodium. It is also called common salt or table salt or rock salt or sea salt. Sea water contains about 2.95 % sodium chloride. As a rock salt it is found at several places in England. Australia, Germany, Canada, Pakistan (Khewra−Punjab) and India (Mandi−Himachal Pradesh). It is found in land lakes (e.g., Sambhar in India, lake Elton in Russia).

Manufacture from sea water: In tropical countries like India, on the sea coasts, the sea water is allowed to dry up under summer heat in small tanks or pits. The solid crust so formed is collected.

In very cold countries, the seawater is concentrated by freezing. The concentrated solution is then evaporated in big iron pans. Sodium chloride thus obtained contains impurities like magnesium chloride, calcium chloride, etc. It is purified by passing hydrogen chloride through a saturated solution of the commercial salt. The precipitation of sodium chloride occurs due to the common ion effect.

Properties

(a) It is a white crystalline solid. It is slightly hygroscopic.

(b) Its density is 2.17 g/ml when pure. It melts at 800°C. It is soluble in water. It dissolves in water with adsorption of heat.

(c) It is insoluble in alcohol.

(d) The common salt is the starting material for the preparation of all the other sodium compounds and extraction of sodium. Sodium, sodium hydroxide and sodium carbonate are the three main materials obtained from common salt which are then used to prepare other important compounds of sodium.

Uses

(i) It is an essential constituent of food.

(ii) It is used as a preservative of food articles like fish, meat, etc.

(iii) It is used for making useful sodium compounds.

(iv) It finds application in salting out of soap and in making freezing mixtures.