Sodium nitrate (not to be confused with sodium nitrite) is a type of salt (NaNO3) which has long been used as an ingredient in explosives and in solid rocket propellants, as well as in glass and pottery enamel, and as a food preservative (such as in hot dogs), and has been mined extensively for those purposes. It is also variously known as caliche, Chile saltpeter, saltpeter, and soda niter.
The world's largest natural deposits of caliche ore were in the Atacama desert of Chile, and many deposits were mined for over a century, until the 1940s. The former Chilean saltpeter mining communities of Humberstone and Santa Laura were declared Unesco World Heritage sites in 2005.
Chile still has the largest reserves of caliche, with active mines in such locations as Pedro de Valdivia, Maria Elena and Pampa Blanca. Sodium nitrate, potassium nitrate, sodium sulphate and iodine are all obtained by the processing of caliche.
Sodium nitrate is also manufactured synthetically by reacting nitric acid with soda ash.
The compound has antimicrobial properties when used as a food preservative. It is found naturally in leafy green vegetables. It has possible health benefits for increasing oxygen to blood, as well as known health side effects in particular at high doses. Side effects include increased risk of cancer and a reduced libido (even at normal doses).
It can be used in the production of nitric acid by combining with sulphuric acid and subsequent separation through fractional distillation of the nitric acid, leaving behind a residue of sodium bisulfate.
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