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Sodium nitrate

From Wikipedia, the free encyclopedia
Not to be confused withsodium nitriteor [[:sodium niter
cubic niter]].

Sodium nitrateis thechemical compoundwith theformulaNaNO
3.Thisalkali metal nitratesaltis also known asChile saltpeter(large deposits of which were historically mined inChile)[4][5]to distinguish it from ordinary saltpeter,potassium nitrate.The mineral form is also known asnitratine,nitratite or sodaniter.

Sodium nitrate is a whitedeliquescentsolid very soluble inwater.It is a readily available source of thenitrateanion (NO3−), which is useful in several reactions carried out on industrial scales for the production offertilizers,pyrotechnics,smoke bombsand otherexplosives,glassandpotteryenamels,food preservatives(esp. meats), andsolid rocket propellant.It has been mined extensively for these purposes.

History[edit]

The first shipment of saltpeter to Europe arrived in England from Peru in 1820 or 1825, right after that country's independence from Spain, but did not find any buyers and was dumped at sea in order to avoid customs toll.[6][7]With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons).[7]Chilefought theWar of the Pacific(1879–1884) against the alliesPeruandBoliviaand took over their richest deposits of saltpeter. In 1919,Ralph Walter Graystone Wyckoffdetermined itscrystalstructure usingX-ray crystallography.

Occurrence[edit]

Advertisement for the product
Advertisement for sodium nitrate fertilizer from Chile on a wall of a village in the Algarve area of Portugal
Mines of Chile, green is sodium nitrate area

The largest accumulations of naturally occurring sodium nitrate are found inChileandPeru,wherenitratesalts are bound within mineral deposits calledcalicheore.[8]Nitrates accumulate on land through marine-fog precipitation and sea-spray oxidation/desiccation followed by gravitational settling of airborne NaNO3,KNO3,NaCl, Na2SO4,and I, in the hot-dry desert atmosphere.[9]El Niño/La Niña extreme aridity/torrential rain cycles favor nitrates accumulation through both aridity and water solution/remobilization/transportation onto slopes and into basins; capillary solution movement forms layers of nitrates; pure nitrate forms rare veins. For more than a century, the world supply of the compound was mined almost exclusively from theAtacamadesert in northern Chile until, at the turn of the 20th century, German chemistsFritz HaberandCarl Boschdeveloped a process for producingammoniafrom the atmosphere on an industrial scale (seeHaber process). With the onset ofWorld War I,Germany began converting ammonia from this process into a syntheticChilean saltpeter,which was as practical as the natural compound in production ofgunpowderand 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 ofcaliche,with active mines in such locations asValdivia,María Elenaand Pampa Blanca, and there it used to be calledwhite gold.[4][5]Sodium nitrate,potassium nitrate,sodium sulfateandiodineare all obtained by the processing of caliche. The former Chilean saltpeter mining communities ofHumberstone and Santa Laurawere declaredUNESCO World Heritage sitesin 2005.

Synthesis[edit]

Sodium nitrate is also synthesized industrially by neutralizingnitric acidwithsodium carbonateorsodium bicarbonate:

2 HNO3+ Na2CO3→ 2 NaNO3+ H2O + CO2
HNO3+ NaHCO3→ NaNO3+ H2O + CO2

or also by neutralizing it withsodium hydroxide(however, this reaction is very exothermic):

HNO3+ NaOH → NaNO3+ H2O

or by mixing stoichiometric amounts ofammonium nitrateandsodium hydroxide,sodium bicarbonateorsodium carbonate:

NH4NO3+ NaOH → NaNO3+ NH4OH
NH4NO3+ NaHCO3→ NaNO3+ NH4HCO3
2NH4NO3+ Na2CO3→ 2NaNO3+ (NH4)2CO3

Uses[edit]

Most sodium nitrate is used in fertilizers, where it supplies a water-soluble form of nitrogen. Its use, which is mainly outside of high-income countries, is attractive since it does not alter thepHof the soil. Another major use is as a complement toammonium nitratein explosives. Molten sodium nitrate and its solutions with potassium nitrate have good thermal stability (up to 600 °C) and high heat capacities. These properties are suitable for thermally annealing metals and for storing thermal energy in solar applications.[10]

Food[edit]

Sodium nitrate is also afood additiveused as a preservative and color fixative in cured meats and poultry; it is listed under itsINS number251 orE numberE251. It is approved for use in the EU,[11]US[12]and Australia and New Zealand.[13]Sodium nitrate should not be confused withsodium nitrite,which is also a common food additive and preservative used, for example, in deli meats.

Thermal storage[edit]

Sodium nitrate has also been investigated as aphase-change materialfor thermal energy recovery, owing to its relatively high melting enthalpy of 178 J/g.[14][15]Examples of the applications of sodium nitrate used for thermal energy storage includesolar thermal powertechnologies and direct steam generatingparabolic troughs.[14]

Steel coating[edit]

Main article:Black oxide

Sodium nitrate is used in a steel coating process in which it forms a surface ofmagnetitelayer.[16]

Health concerns[edit]

Studies have shown a link between increased levels of nitrates and increased deaths from certain diseases includingAlzheimer's disease,diabetes mellitus,stomach cancer,andParkinson's disease:possibly through the damaging effect ofnitrosamineson DNA; however, little has been done to control for other possible causes in the epidemiological results.[17]Nitrosamines, formed in cured meats containing sodium nitrate and nitrite, have been linked togastric cancerandesophageal cancer.[18]Sodium nitrate and nitrite are associated with a higher risk ofcolorectal cancer.[19]

Substantial evidence in recent decades, facilitated by an increased understanding of pathological processes and science, exists in support of the theory that processed meat increases the risk ofcolon cancerand that this is due to the nitrate content. 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 producecarcinogenicNOCs (nitrosocompounds). NOCs can be formed either when meat is cured or in the body as meat is digested.[20]

However, several things complicate the otherwise straightforward understanding that "nitrates in food raise the risk of cancer". Processed meats have no fiber, vitamins, or phytochemical antioxidants, are high in sodium, may contain high fat, and are often fried or cooked at a temperature sufficient to degrade protein into nitrosamines. Nitrates are key intermediates and effectors in the primary vasculature signaling which is necessary for all mammals to survive.[21]

See also[edit]

References[edit]

  1. ^Haynes, William M. (2016-06-22).CRC Handbook of Chemistry and Physics.CRC Press.ISBN978-1-4987-5429-3.
  2. ^"Sodium nitrate".PubChem.Retrieved11 June2021.
  3. ^abZumdahl, Steven S. (2009).Chemical Principles 6th Ed.Houghton Mifflin Company. p. A23.ISBN978-0-618-94690-7.
  4. ^ab"The Nitrate Towns of Chile".Atlas Obscura.Retrieved27 May2019.
  5. ^abMutic, Anja (26 October 2012)."The ghost towns of northern Chile".Washington Post.Retrieved27 May2019.
  6. ^S. H. Baekeland "Några sidor af den kemiska industrien" (1914)Svensk Kemisk Tidskrift,p. 140.
  7. ^abFriedrich Georg Wieck,Uppfinningarnas bok(1873, Swedish translation ofBuch der Erfindungen),vol. 4, p. 473.
  8. ^Stephen R. Bown,A Most Damnable Invention: Dynamite, Nitrates, and the Making of the Modern World,Macmillan, 2005,ISBN0-312-32913-X,p. 157.
  9. ^Arias, Jaime (24 Jul 2003).On the Origin of Saltpeter, Northern Chile Coast.International Union for Quaternary Research. Archived fromthe originalon 4 March 2016.Retrieved19 Aug2018.
  10. ^Laue, Wolfgang; Thiemann, Michael; Scheibler, Erich; Wiegand, Karl (2000). "Nitrates and Nitrites".Ullmann's Encyclopedia of Industrial Chemistry.Weinheim: Wiley-VCH.doi:10.1002/14356007.a17_265.ISBN978-3527306732.
  11. ^UK Food Standards Agency:"Current EU approved additives and their E Numbers".Retrieved2011-10-27.
  12. ^US Food and Drug Administration:"Listing of Food Additives Status Part II".Food and Drug Administration.Retrieved2011-10-27.
  13. ^Australia New Zealand Food Standards Code"Standard 1.2.4 – Labelling of ingredients".Retrieved2011-10-27.
  14. ^abBauer, Thomas; Laing, Doerte; Tamme, Rainer (2011-11-15). "Characterization of Sodium Nitrate as Phase Change Material".International Journal of Thermophysics.33(1): 91–104.doi:10.1007/s10765-011-1113-9.ISSN0195-928X.S2CID54513228.
  15. ^ICTAC Working Group; Sabbah, R.; et al. (1999-06-14)."Reference materials for calorimetry and differential thermal analysis".Thermochimica Acta.331(2): 93–204.doi:10.1016/S0040-6031(99)00009-X.ISSN0040-6031.
  16. ^Fauzi, Ahmad Asyraf Bin Ahmad (2014).Production of Magnetite Thin Film Over Steel Substrate Using Hot Alkaline Nitrate Blackening Method.Universitat Politècnica de Catalunya. Escola Politècnica Superior d'Enginyeria de Vilanova i la Geltrú. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, 2014 (Grau en Enginyeria Mecànica).
  17. ^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.17(3): 519–29.doi:10.3233/JAD-2009-1070.PMC4551511.PMID19363256.
  18. ^Jakszyn, Paula; Gonzalez, Carlos-Alberto (21 Jul 2006)."Nitrosamine and related food intake and gastric and oesophageal cancer risk: a systematic review of the epidemiological evidence".World Journal of Gastroenterology.12(27): 4296–4303.doi:10.3748/wjg.v12.i27.4296.PMC4087738.PMID16865769.
  19. ^Cross, AJ; Ferrucci, LM; Risch, A; et al. (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.PMC2840051.PMID20215514.
  20. ^"The Associations between Food, Nutrition and Physical Activity and the Risk of Colorectal Cancer",Archived2019-07-26 at theWayback MachineWorld Cancer Research Fund (2010)
  21. ^Machha, Ajay; Schechter, Alan N. (August 2011)."Dietary nitrite and nitrate: a review of potential mechanisms of cardiovascular benefits".European Journal of Nutrition.50(5): 293–303.doi:10.1007/s00394-011-0192-5.ISSN1436-6207.PMC3489477.PMID21626413.

Further reading[edit]

External links[edit]

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