Sodium nitrate
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| Names | |||
|---|---|---|---|
| IUPAC name
Sodium nitrate
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| Other names | |||
| Identifiers | |||
3D model (JSmol)
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| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.028.686 | ||
| E number | E251 (preservatives) | ||
PubChem CID
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| RTECS number |
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| UNII | |||
| UN number | 1498 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| NaNO3 | |||
| Molar mass | 84.9947 g/mol | ||
| Appearance | White powder or colorless crystals | ||
| Odor | sweet | ||
| Density | 2.257 g/cm3, solid | ||
| Melting point | 308 °C | ||
| Boiling point | 380 °C, decomposes | ||
| 73 g/100 mL (0°C) 91.2 g/100 mL (25 °C) 180 g/100 mL (100 °C) | |||
| Solubility | very soluble in ammonia; soluble in alcohol | ||
Refractive index (nD)
|
1.587 (trigonal) 1.336 (rhomobohedral) | ||
| Structure | |||
| trigonal and rhombohedral | |||
| Thermochemistry | |||
Std molar
entropy (S⦵298) |
116 J·mol−1·K−1[1] | ||
Std enthalpy of
formation (ΔfH⦵298) |
−467 kJ·mol−1[1] | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
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Oxidant, irritant | ||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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3236 mg/kg | ||
| Related compounds | |||
Other anions
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Sodium nitrite | ||
Other cations
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Lithium nitrate Potassium nitrate Rubidium nitrate Caesium nitrate | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium nitrate is the chemical compound with the formula NaNO3. This salt is also known as Chile saltpeter or Peru saltpeter (due to the large deposits found in each country) to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.
Sodium nitrate is a white solid which is very soluble in water. It may be used as a constituent of fertilizers, pyrotechnics and smoke bombs, glass and pottery enamels, as a food preservative and a solid rocket propellant. It has been mined extensively for these purposes.
History
The first shipment of Chile saltpeter to Europe arrived in England in 1820 or 1825, but did not find any buyers and was dumped at sea in order to avoid customs toll.[2][3] With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons[3]). Chile fought against the allies Peru and Bolivia in the War of the Pacific 1879-1884 and took over the richest deposits. In 1919, Ralph Walter Graystone Wyckoff determined its crystal structure using X-ray crystallography.
Sources
The largest accumulations of naturally occurring sodium nitrate are found in Chile and Peru, where nitrate salts are bound within mineral deposits called caliche ore.[4] For more than a century, the world supply of the compound was mined almost exclusively from the Atacama desert in northern Chile until, at the turn of the 20th century, German chemists Fritz Haber and Carl Bosch developed a process for producing ammonia from the atmosphere on an industrial scale (see Haber process). With the onset of World War I, Germany began converting ammonia from this process into a synthetic Chilean saltpeter which was as practical as the natural compound in production of gunpowder and other munitions. By the 1940s, this conversion process resulted in a dramatic decline in demand for sodium nitrate procured from natural sources.
Chile still has the largest reserves of caliche, with active mines in such locations as Pedro de Valdivia, María 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
- 2 HNO3 + Na2CO3 → 2 NaNO3 + H2O + CO2
or by mixing stoichiometric amounts of ammonium nitrate and sodium hydroxide or sodium bicarbonate.
- NH4NO3 + NaOH → NaNO3 + NH4OH
- NH4NO3 + NaHCO3 → NaNO3 + NH4HCO3
Applications
Sodium nitrate was used extensively as a fertilizer and a raw material for the manufacture of gunpowder in the late 19th century. It can be combined with iron hydroxide to make a synthetic resin.
Sodium nitrate 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.
Sodium nitrate is also a food additive used as a preservative and color fixative in cured meats and poultry; it is listed under its INS number 251 or E number E251. It is approved for use in the EU,[5] USA[6] and Australia and New Zealand.[7] Sodium nitrate should not be confused with sodium nitrite, which is also a common food additive and preservative used for example, in deli meats.
Less common applications include as an oxidizer in fireworks replacing potassium nitrate commonly found in black powder and as a component in instant cold packs.[8]
Sodium nitrate is used together with potassium nitrate and calcium nitrate for heat storage and, more recently, for heat transfer in solar power plants. A mixture of sodium nitrate, calcium nitrate and potassium nitrate is used as energy storage material in prototype plants, such as Andasol Solar Power Station and the Archimede project.
It is also used in the wastewater industry for facultative microorganism respiration. Nitrosomonas, a genus of microorganisms, consumes nitrate in preference to oxygen, enabling it to grow more rapidly in the wastewater to be treated.
Sodium Nitrate is also sometimes used by marine aquarists who utilize carbon dosing techniques. It is used to increase nitrate levels in the water and promote bacterial growth.
Health concerns
Like sodium nitrite, sodium nitrate used in foods forms small amounts of nitrosamines (N-nitroso compounds or NOCs), some of which are human carcinogens known to cause DNA damage and increased cellular degeneration. Studies have shown a link between increased levels of nitrates and increased deaths from certain diseases including Alzheimer's, diabetes mellitus and Parkinson's, possibly through the damaging effect of nitrosamines on DNA.[9] Nitrosamines, formed in cured meats containing sodium nitrate and nitrite, have been linked to gastric cancer and oesophageal cancer.[10] Sodium nitrate and nitrite are associated with a higher risk of colorectal cancer.[11] World Cancer Research Fund UK,[12] states that one of the reasons that processed meat increases the risk of colon cancer is its content of nitrate. A small amount of the nitrate added to meat as a preservative breaks down into nitrite, in addition to any nitrite that may also be added. The nitrite then reacts with protein-rich foods (such as meat) to produce NOCs. NOCs can be formed either when meat is cured or in the body as meat is digested.
Gallery
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See also
- War of the Pacific, also known as "the Saltpeter War".
Notes and references
- ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X.
- ^ S. H. Baekeland "Några sidor af den kemiska industrien" (1914) Svensk Kemisk Tidskrift, p. 140.
- ^ a b Friedrich Georg Wieck, Uppfinningarnas bok (1873, Swedish translation of Buch der Erfindungen), vol. 4, p. 473.
- ^ Stephen R. Bown, A Most Damnable Invention: Dynamite, Nitrates, and the Making of the Modern World, Macmillan, 2005, ISBN 0-312-32913-X, p. 157
- ^ UK Food Standards Agency: "Current EU approved additives and their E Numbers". Retrieved 2011-10-27.
- ^ US Food and Drug Administration: "Listing of Food Additives Status Part II". Retrieved 2011-10-27.
- ^ Australia New Zealand Food Standards Code"Standard 1.2.4 - Labelling of ingredients". Retrieved 2011-10-27.
- ^ Albert A. Robbins "Chemical freezing package" U.S. patent 2,898,744, Issue date: August 1959
- ^ De La Monte, SM; Neusner, A; Chu, J; Lawton, M (2009). "Epidemilogical trends strongly suggest exposures as etiologic agents in the pathogenesis of sporadic Alzheimer's disease, diabetes mellitus, and non-alcoholic steatohepatitis". Journal of Alzheimer's disease : JAD. 17 (3): 519–29. doi:10.3233/JAD-2009-1070. PMID 19363256.
- ^ http://ecnis.openrepository.com/ecnis/handle/10146/25215
- ^ Cross, AJ; Ferrucci, LM; Risch, A; Graubard, BI; Ward, MH; Park, Y; Hollenbeck, AR; Schatzkin, A; Sinha, R (2010). "A large prospective study of meat consumption and colorectal cancer risk: An investigation of potential mechanisms underlying this association". Cancer Research. 70 (6): 2406–14. doi:10.1158/0008-5472.CAN-09-3929. PMC 2840051. PMID 20215514.
- ^ "Why does processed meat increase bowel cancer risk?", World Cancer Research Fund (2010) accessdate 2010-03-06
Further reading
- Barnum, Dennis (2003). "Some History of Nitrates". Journal of Chemical Education. 80 (12): 1393–. doi:10.1021/ed080p1393.