sodium chloride (NaCl)
Sodium chloride is readily soluble in water and slightly soluble in ethanol. Its solubility in water is unusual in that it changes very little with temperature. Sodium chloride crystallizes in the cube system to form face-centered cubic crystals.
HistorySalt has been used for thousands of years to preserve food (especially meat and fish). In Roman society, salt was used as currency, and soldiers were paid in salt. The Latin sal is the root for the English word "salary" and the phrase that a person is "worth their salt" means they are worth what they earn.
SourcesWhen seawater evaporates in a closed lagoon, halite and other minerals precipitate out and sink to the bottom as crystals. In this way, great beds of rock salt have been formed. When sediments containing rock salt are folded and uplifted, the beds of rock salt are exposed, and in time they dissolve away, forming brines which either percolate into the ground or the ocean, or collect in salt lakes.
Salt can be mined from halite either by traditional mining practices using heavy equipment underground, or by pumping hot water in pipes into the salt deposit, where the hot water dissolves the halite. The resulting salt water is then pumped to surface and evaporated to yield salt, a process known as solution mining. In some modern dry salt lakes, a crust of halite can be recovered by simply scraping the salt crust off the lake bottom with bulldozers or scrapers.
Much salt is produced by controlled evaporation of seawater or of brines in salt lakes. In this technique, the water is pumped or drained into shallow ponds. Solar evaporation will eventually (in an arid climate) concentrate the salt to the point where it crystallizes on the floor of the pond.
Salt is produced in many countries. The leading producers are the United States, China, Germany, India, and Canada.
Sodium chloride and lifeSodium chloride has a key role in biological systems in maintaining electrolyte balances. However, when ingested in excess, as often happens in the developed world, it can lead to high blood pressure (hypertension).
Many microorganisms cannot live in an overly salty environment. Notable exceptions are halophiles which thrive in places such as salt flats that are highly saline.
Sodium chloride in science fiction
Related category INORGANIC CHEMSITRY
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