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Sodium nitrate

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Not to be confused with sodium nitrite, sodium nitride, or nitratine.
Sodium nitrate
Names
IUPAC name
Sodium nitrate
Other names
Peru saltpeter
Soda niter
cubic niter
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.028.686 Edit this at Wikidata
EC Number
  • 231-554-3
E number E251 (preservatives)
RTECS number
  • WC5600000
UNII
UN number 1498
  • InChI=1S/NO3.Na/c2-1(3)4;/q-1;+1 checkY
    Key: VWDWKYIASSYTQR-UHFFFAOYSA-N checkY
  • InChI=1/NO3.Na/c2-1(3)4;/q-1;+1
    Key: VWDWKYIASSYTQR-UHFFFAOYAL
  • [Na+].[O-][N+]([O-])=O
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 (586 °F; 581 K)
Boiling point 380 °C (716 °F; 653 K) decomposes
73 g/100 g water (0 °C)
91.2 g/100 g water (25 °C)[1][2]
180 g/100 g water (100 °C)
Solubility very soluble in ammonia, hydrazine
soluble in alcohol
slightly soluble in pyridine
insoluble in acetone
−25.6·10−6 cm3/mol
1.587 (trigonal)
1.336 (rhombohedral)
Viscosity 2.85 cP (317 °C)
Structure
trigonal and rhombohedral
Thermochemistry
93.05 J/(mol K)
116 J/(mol K)[3]
−467 kJ/mol[3]
−365.9 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Harmful (Xn)
Oxidant (O)
GHS labelling:
GHS07: Exclamation markGHS03: Oxidizing
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
1
0
0
OX
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
3236 mg/kg
Safety data sheet (SDS) ICSC 0185
Related compounds
Other anions
 Sodium nitrite
Other cations
 Lithium nitrate
Potassium nitrate
Rubidium nitrate
Caesium nitrate
Related compounds
 Sodium sulfate
Sodium chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Sodium nitrate is the chemical compound with the formula NaNO
3. This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile)[4][5] 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 deliquescent solid very soluble in water. It is a readily available source of the nitrate anion (NO3−), which is useful in several reactions carried out on industrial scales for the production of fertilizers, pyrotechnics, smoke bombs and other explosives, glass and pottery enamels, food preservatives (esp. meats), and solid rocket propellant. It has been mined extensively for these purposes.

History

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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] Chile fought the War of the Pacific (1879–1884) against the allies Peru and Bolivia and took over their richest deposits of saltpeter. In 1919, Ralph Walter Graystone Wyckoff determined its crystal structure using X-ray crystallography.

Occurrence

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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 in Chile and Peru, where nitrate salts are bound within mineral deposits called caliche ore.[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 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 Valdivia, María Elena and Pampa Blanca, and there it used to be called white gold.[4][5] 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.

Synthesis

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Sodium nitrate is also synthesized industrially by neutralizing nitric acid with sodium carbonate or sodium bicarbonate:

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

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

HNO3 + NaOH → NaNO3 + H2O

or by mixing stoichiometric amounts of ammonium nitrate and sodium hydroxide, sodium bicarbonate or sodium carbonate:

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

Uses

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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 the pH of the soil. Another major use is as a complement to ammonium nitrate in 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

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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,[11] US[12] and Australia and New Zealand.[13] Sodium nitrate should not be confused with sodium nitrite, which is also a common food additive and preservative used, for example, in deli meats.

Thermal storage

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Sodium nitrate has also been investigated as a phase-change material for 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 include solar thermal power technologies and direct steam generating parabolic troughs.[14]

Steel coating

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Main article: Black oxide

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

Health concerns

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Studies have shown a link between increased levels of nitrates and increased deaths from certain diseases including Alzheimer's disease, diabetes mellitus, stomach cancer, and Parkinson's disease: possibly through the damaging effect of nitrosamines on 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 to gastric cancer and esophageal cancer.[18] Sodium nitrate and nitrite are associated with a higher risk of colorectal 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 of colon cancer and 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 produce carcinogenic NOCs (nitroso compounds). 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

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References

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  1. ^ Haynes, William M. (2016-06-22). CRC Handbook of Chemistry and Physics. CRC Press. ISBN 978-1-4987-5429-3.
  2. ^ "Sodium nitrate". PubChem. Retrieved 11 June 2021.
  3. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 978-0-618-94690-7.
  4. ^ a b "The Nitrate Towns of Chile". Atlas Obscura. Retrieved 27 May 2019.
  5. ^ a b Mutic, Anja (26 October 2012). "The ghost towns of northern Chile". Washington Post. Retrieved 27 May 2019.
  6. ^ S. H. Baekeland "Några sidor af den kemiska industrien" (1914) Svensk Kemisk Tidskrift, p. 140.
  7. ^ a b Friedrich Georg Wieck, Uppfinningarnas bok (1873, Swedish translation of Buch 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, ISBN 0-312-32913-X, p. 157.
  9. ^ Arias, Jaime (24 Jul 2003). On the Origin of Saltpeter, Northern Chile Coast. International Union for Quaternary Research. Archived from the original on 4 March 2016. Retrieved 19 Aug 2018.
  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. ISBN 978-3527306732.
  11. ^ UK Food Standards Agency: "Current EU approved additives and their E Numbers". Retrieved 2011-10-27.
  12. ^ US Food and Drug Administration: "Listing of Food Additives Status Part II". Food and Drug Administration. Retrieved 2011-10-27.
  13. ^ Australia New Zealand Food Standards Code"Standard 1.2.4 – Labelling of ingredients". Retrieved 2011-10-27.
  14. ^ a b Bauer, 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. ISSN 0195-928X. S2CID 54513228.
  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. ISSN 0040-6031.
  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. PMC 4551511. PMID 19363256.
  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. PMC 4087738. PMID 16865769.
  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. PMC 2840051. PMID 20215514.
  20. ^ "The Associations between Food, Nutrition and Physical Activity and the Risk of Colorectal Cancer", Archived 2019-07-26 at the Wayback Machine World 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. ISSN 1436-6207. PMC 3489477. PMID 21626413.

Further reading

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