| Sodium nitrate | |
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Sodium nitrate |
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| Identifiers | |
| CAS number | 7631-99-4 |
| PubChem | 24268 |
| ChemSpider | 22688 |
| UNII | 8M4L3H2ZVZ |
| UN number | 1498 |
| ChEMBL | CHEMBL1644698 |
| RTECS number | WC5600000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | NaNO3 |
| Molar mass | 84.9947 g/mol |
| Appearance | White powder or colorless crystals with sweet smell |
| Density | 2.257 g/cm3, solid |
| Melting point |
308 °C |
| Boiling point |
380 °C decomp. |
| Solubility in water | 730 g/L (0°C) 921 g/L (25 °C) 1800 g/L (100 °C) |
| Solubility | very soluble in ammonia; soluble in alcohol |
| Refractive index (nD) | 1.587 (trigonal) 1.336 (rhomobohedral) |
| Structure | |
| Crystal structure | trigonal and rhombohedral |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−468 kJ/mol |
| Standard molar entropy S |
117 J·mol−1 K−1 |
| Hazards | |
| MSDS | ICSC 0185 |
| EU Index | Not listed |
| Main hazards | Oxidant, irritant |
| NFPA 704 |
0
1
0
OX
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| Flash point | Non-flammable |
| LD50 | 3236 mg/kg |
| Related compounds | |
| Other anions | Sodium nitrite |
| Other cations | Lithium nitrate Potassium nitrate Rubidium nitrate Caesium nitrate |
| Related compounds | Sodium sulfate Sodium chloride |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, 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, is a white solid which is very soluble in water. The mineral form is also known as nitratine, nitratite or soda niter.
Sodium nitrate 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.
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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.[1][2] With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons[2]). 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.
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.[3] 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
or by mixing stoichiometric amounts of ammonium nitrate and sodium hydroxide or sodium bicarbonate.
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 resin.
Sodium nitrate should not be confused with the related compound, sodium nitrite. Sodium nitrate in the brine gives cooked corned beef its classic reddish color (without it corned beef comes out gray), and it kills botulism spores. Nitrate is actually changed to nitrite by bacterial action during processing and storage and nitrate itself has no effect on meat color.
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 as an oxidizer in fireworks replacing potassium nitrate commonly found in black powder and as a component in instant cold packs.[4]
Sodium nitrate is used together with potassium nitrate and Calcium nitrate for heat storage and, more recently, for heat transfer in solar power plants.
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 a food additive used as a preservative and colour 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]
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.
Like sodium nitrite, sodium nitrate forms nitrosamines – 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.[8] Nitrosamines, formed in cured meats containing sodium nitrate and nitrite, have been linked to gastric cancer and oesophageal cancer.[9] Sodium nitrate and nitrite are associated with a higher risk of colorectal cancer.[10] World Cancer Research Fund UK,[11] 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 N-nitroso compounds (NOCs). Some types of NOCs are known to cause cancer. NOCs can be formed either when meat is cured or in the body as meat is digested.