Sodium nitrate is the
chemical compound with the
formula NaNO
3. This
salt, also known as "Chile saltpeter" or "Peru saltpeter" (to distinguish it from ordinary saltpeter,
potassium nitrate), is a white solid which is very soluble in
water. The mineral form is also known as
nitratine or
soda niter.
Sodium nitrate is used as an ingredient in
fertilizers, pyrotechnics, as a
food preservative, and as a
solid rocket propellant, as well as in
glass and
pottery enamels; the compound has been mined extensively for those purposes.
The mining of South American saltpeter was such a profitable business that
Chile fought against the allies
Peru and
Bolivia and took over the richest deposits in the
War of the Pacific. 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, when its value declined dramatically in the first decades of the twentieth century (see
Haber process).
Chile still has the largest reserves of caliche, with active mines in such locations as Pedro de Valdivia, Maria Elena and Pampa Blanca, and there it used to be called "white gold". Sodium nitrate,
potassium nitrate,
sodium sulfate and
iodine are all obtained by the processing of caliche. The former Chilean saltpeter mining communities of
Humberstone and Santa Laura were declared Unesco World Heritage sites in 2005.
Sodium nitrate is also synthesized industrially by neutralizing
nitric acid with
soda ash.
Applications
Sodium nitrate was used extensively as a fertilizer and a raw material for the manufacture of gunpowder in the late nineteenth century. Sodium nitrate has
antimicrobial properties when used as a
food preservative. It is found naturally in
leafy green vegetables. It can also be combined with iron hydroxide to make a resin.
Sodium nitrate should not be confused with the related compound,
sodium nitrite.
It can be used in the production of
nitric acid by combining it with
sulfuric acid and subsequent separation through
fractional distillation of the nitric acid, leaving behind a residue of
sodium bisulfate. Hobbyist gold refiners use sodium nitrate to make a hybrid
aqua regia that dissolves gold and other metals.
Less common applications include its use as a substitute oxidizer used in fireworks as a replacement for
potassium nitrate commonly found in
black powder and as a component in instant cold packs.
Because sodium nitrate can be used as a
Phase Change Material it may be used for
heat transfer in
solar power plants.
It is also used in the wastewater industry for the faculative microrganisms respiration. The growth of
nitrosomines will use the nitrate instead of oxygen to breath easier.
See also
Notes and references
