sodium nitrate

sodium nitrate

sodium nitrate, chemical compound, NaNO3, a colorless, odorless crystalline compound that closely resembles potassium nitrate (saltpeter or niter) in appearance and chemical properties. It is soluble in water, alcohol, and liquid ammonia. Sodium nitrate is also called soda niter or Chile saltpeter. It is found naturally in large deposits in arid regions of Chile, Peru, Argentina, and Bolivia as caliche, a crude, impure nitrate rock or gravel. Natural deposits are the major source of sodium nitrate; it is also obtained in small amounts as a byproduct of chlorine production by the nitrosyl chloride process, in which sodium chloride (common salt) is reacted with nitric acid. Sodium nitrate is used in making potassium nitrate, fertilizers, and explosives. It was formerly an important raw material for the production of nitric acid.
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, also known as "Chile 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 nitre.

Sodium nitrate is used as an ingredient in fertilizers, pyrotechnics, as a food preservative, and as a solid rocket propellants, as well as in glass and pottery enamels; the compound has been mined extensively for those purposes.

The mining of Chile saltpeter was such a profitable business that three nations, Chile, Peru, and Bolivia fought 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. 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.

Sodium nitrate should not be confused with the related compound, sodium nitrite. The presence of sodium nitrite in food is controversial due to the development of nitrosamines when the food, primarily bacon, is cooked at high temperatures. Its usage is carefully regulated in the production of cured products; in the United States, the concentration in finished products is limited to 200 ppm, and is usually lower. In about 1970, it was found that the addition of ascorbic acid inhibited nitrosamine production. U.S. manufacturing of cured meats now requires the addition of 500 ppm of ascorbic acid or erythorbic acid, a cheaper isomer. The nitrate compound itself is not harmful, however, and is among the antioxidants found in fresh vegetables.

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.

Notes and references

Further reading

  • Dennis W. Barnum. (2003). "Some History of Nitrates." Journal of Chemical Education. v. 80, p. 1393-. link

External links

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