Sodium chloride , is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs as the mineral halite. In its edible form, common 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. Another major application of sodium chloride is de-icing of roadways in sub-freezing weather.
Uses In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.
Chemical functions Salt is used, directly or indirectly, in the production of many chemicals, which consumes most of the world's production.
Chlor-alkali industry
It is the starting point for the chloralkali process, the industrial process to produce chlorine and sodium hydroxide, according to the chemical equation:
2 NaCl
+ 2 H 2 O → electrolysis Cl 2
+ H 2
+ 2 NaOH {\displaystyle {\ce {2NaCl{}+2H2O->[{\text{electrolysis}}]Cl2{}+H2{}+2NaOH}}}
This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include PVC thermoplastics production, disinfectants, and solvents. Sodium hydroxide is extensively used in many different industries enabling production of paper, soap, aluminum, and more.
Soda-ash industry Sodium chloride is used in the Solvay process to produce sodium carbonate and calcium chloride. Sodium carbonate, in turn, is used to produce glass, sodium bicarbonate, and dyes, as well as a myriad of other chemicals. In the Mannheim process, sodium chloride is used for the production of sodium sulfate and hydrochloric acid.
Miscellaneous industrial uses Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. It is used to flocculate and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum. Salt is also used to increase the curing of concrete in cemented casings. 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 increase yield in dyebaths and make the colors look sharper. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes. For use in the pulp and paper industry, it is used to manufacture sodium chlorate, which is then reacted with sulfuric acid and a reducing agent such as methanol to manufacture chlorine dioxide, a bleaching chemical that is widely used to bleach wood pulp. In tanning and leather treatment, salt is added to animal hides to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides. In rubber manufacture, salt is used to make buna, neoprene, and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified latex made from chlorinated butadiene. Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load.
Water softening
Hard water contains calcium and magnesium ions that interfere with action of soap and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use ion-exchange resins to remove ions that cause the hardness. These resins are generated and regenerated using sodium chloride.
Road salt
The second major application of salt is for deicing and anti-icing of roads, both in grit bins and spread by winter service vehicles. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated solution of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For deicing, mixtures of brine and salt are used, sometimes with additional agents such as calcium chloride and/or magnesium chloride. The use of salt or brine becomes ineffective below −10 °C (14 °F).
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