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Salt mounds in Salar de Uyuni, Bolivia. Photo by Wikimedian Luca Galuzzi.


1. The common name of sodium chloride (NaCl), a white substance found commonly in the earth (called rock salt) or dissolved in seawater. For many years, particularly before refrigeration, people used salt as a seasoning and also as a preservative for foods because it killed bacteria. Salt is also used to preserve hides in leather making. 2. CHEMISTRY. Any compound formed when the hydrogen in an acid is replaced by a metal or a group of elements called a positive ion. A salt is also formed as a precipitate in water when an acid and a base neutralize each other. Many minerals are salts of one kind or another.