Sodium chloride's Uses And Preparation

Sodium chloride, also known as salt, common salt, table salt or halite, is an ionic compound with the formula NaCl, representing equal proportions of sodium and chlorine. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms. In the form of edible or table salt it is commonly used as a condiment and food preservative. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses. A second major consumer of sodium chloride is de-icing of roadways in sub-freezing weather.

1. Uses of Sodium chloride 

As the major ingredient in edible salt, Sodium chloride is commonly used as a condiment and food preservative. Sodium chloride can manufacture pulp and paper, to setting dyes in textiles and fabric, to producing soaps, detergents, and other bath products. Sodium chloride is sometimes used as a cheap and safe desiccant because of its hygroscopic properties.

Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. Road salt ends up in fresh water bodies and could harm aquatic plants and animals by disrupting their osmoregulation ability. The industrial uses of salt include, in descending order of quantity consumed, various applications, oil and gas exploration, textiles and dyeing, pulp and paper, metal processing, tanning and leather treatment, and rubber manufacture. It is used to flocculate and increase the density of the drilling fluid to overcome high downwell gas pressures.

In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, to promote “salting out” of dyestuff precipitates, and to blend with concentrated dyes to standardize them. In metal processing, salt is used in concentrating uranium ore into uranium oxide (yellow cake). It also is used in processing aluminium, beryllium, copper, steel and vanadium. In the pulp and paper industry, salt is used to bleach wood pulp. It also is used to make sodium chlorate. In rubber manufacture, salt is used to make buna, neoprene and white rubber types.

2. Preparation of Sodium chloride

Salt is currently mass-produced by evaporation of seawater or brine from other sources, such as brine wells and salt lakes, and by mining rock salt, called halite. Using sold salt dissoves in distilled water. The mixture is boiled after addition of sodium hydroxide, then is stored overnight and filtered. You should keep filtrate clean and then cool down it simultaneously put into pure HCl gas to make the mixture saturated. After that, crystal of Sodium chloride will separate out. There are also three methods of Sodium chloride production and purification: brine solution, rock salt mining, and the open pan or grainer process:

To produce Sodium chloride from brine, water is pumped into the salt deposit and the saturated salt solution containing 26% salt, 73.5% water, and 0.5% impurities, is removed. Hydrogen sulfide is removed by aeration, and oxidation with chlorine. Calcium (Ca2+), magnesium (Mg2+), and iron (Fe3+) are precipitated as the carbonates using soda ash and are removed in a settling tank. The brine solution can be sold directly or it can be evaporated to give salt of 99.8% purity.

Rock salt is produced from deep mines so that the salt is taken directly from the deposit. Salt obtained by this method is 98.5 to 99.4% pure.

In the open pan or grainer salt method, hot brine solution is held in an open pan approximately 4 to 6 meters wide, 45 to 60 meters long, and 60 cm deep at 96°C. Flat, pure sodium chloride crystals form on the surface and fall to the bottom and are raked to a centrifuge, separated from the brine, and dried. A purity of 99.98% is obtained. A vacuum pan system is also available.