Sodium Chloride

Halite (sodium chloride) comes from the Greek halos, meaning "salt" and lithos meaning "rock," and is in fact, better known as rock salt. Halite is called an evaporate because it is formed by the evaporation of saline water in partially enclosed basins. It is very common worldwide, deposited in solid underground masses, and as a dissolved solution in oceans and many arid-region inland lakes. has lots of salt; it contains an average of 2.6% (by weight) NaCl, or 26 million metric tons per cubic kilometre.

Whenever seawater evaporates, several different minerals come out of solution, starting with the carbonate mineral calcite, then gypsum, then halite. In places where evaporation happens repeatedly, halite beds can be 1,000 meters thick.

Halite is a soft mineral that flows easily under pressure. At depths of as little as 3 kilometres, it begins to rise through the rocks above it in cylindrical plugs called salt domes.

Every day, each of the earth's 5.9 billion inhabitants uses salt. Annual salt production has increased over the past century from 10 million tons to over 200 million tons today. Nearly 100 nations have salt producing facilities ranging from primitive solar evaporation to advanced, multi-stage evaporation in salt refineries.

Structure

This structure shows the halite, or rock-salt structure. The white spheres represent the larger chloride ions and the smaller red spheres represent the sodium ions. In this structure the chloride ions form a face-centred cubic array, with the sodium ions residing inside the octahedral holes.

Sodium chloride are . It consists of tightly through ionic bonding of the and chloride ions. The is often used as an of crystalline structure. It can be . It varies in colour from colourless, when pure, to white, grey or brownish, typical of rock salt (halite). Chemically, it is ...

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Structure

Purity of rock salt produced varies depending on the type of salt (evaporated, rock, solar) and on the source. Rock salt typically ranges between 95% and 99% NaCl, and mechanically evaporated salt and solar salt normally exceed 99% NaCl. Evaporated salt made with purified brine has the highest purity, in some cases 99.99% NaCl.

Uses

Food seasoning
For road safety in the winter months to melt snow and ice
For water softeners
For medicinal purposes
Primary ore for both sodium and chlorine

The greatest single use for salt is as a feedstock for the production of chemicals. The chlor-alkali industry uses salt, primarily as salt in brine from captive brine wells, to produce chlorine and caustic soda. Demand for salt in to produce chemicals fell from 25 million metric tons in 1974 to a low of 16.7 million metric tons in 1992. However, chemical use rebounded in 1994 to 18.4 million metric tons. Much of the decreased demand for chlorine was attributed to environmental concerns about dioxins. Salt is also used to make sodium chlorate and metallic sodium by electrolysis and, sodium sulphate and hydrochloric acid by reacting with sulphuric acid.

All animals, humans included, require both sodium and chloride for life and health. Since the body cannot manufacture either, they are "essential" nutrients. While developed countries dedicate most of their salt to chemical production, developing countries often use most of their salt for human and animal nutrition. Sodium is an essential nutrient, a mineral that the body cannot manufacture itself but which is required . Because of , several interacting mechanisms guard against under-consumption of salt and its threat to your body's nerves and muscles and interference with the which adjusts intra- and extra-cellular pressures. If your salt intake varies widely, these mechanisms activate to assure that , maintaining a relatively constant . , too, is essential to good health. It preserves acid-base balance in the body, aids potassium absorption, supplies the essence of digestive stomach acid, and enhances the ability of the blood to carry carbon dioxide from respiring tissues to the lungs.

Livestock, poultry and other animals do not always receive adequate amounts of sodium and chloride from forages and other feeds. They need supplemental salt as part of a nutritionally balanced diet to remain healthy, disease free, and to achieve optimum growth and reproduction rates. Because animals have a natural, definitive appetite for salt - they will eat only a certain amount - it is used to ensure adequate intake of less palatable nutrients and as a means of limiting feed intake. Salt can be mixed with feed or fed free-choice, and is an excellent carrier for trace minerals, It is produced plain or as trace mineralised salt, in 50 lb blocks, smaller spools, and as loose salt, commonly known as mixing salt.