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E251 (Sodium nitrate)

CAS Number:7631-99-4
Molecule Formula:NaNO3
Molecular Weight:84.99

E251 (Sodium nitrate) is the chemical compound with the formula NaNO3.
This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile)to distinguish it from ordinary saltpeter, potassium nitrate.
The mineral form is also known as nitratine, nitratite or soda niter.
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E251 (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-
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.
With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons).
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-
The largest accumulations of naturally occurring E251 (Sodium nitrate) are found in Chile and Peru, where nitrate salts are bound within mineral deposits called caliche ore.
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.
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 E251 (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.
E251 (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.

-Computed Properties-
Molecular Weight   84.995
Hydrogen Bond Donor Count   0
Hydrogen Bond Acceptor Count   3
Rotatable Bond Count   0
Exact Mass   84.97758714
Monoisotopic Mass   84.97758714
Topological Polar Surface Area   62.9 Å²
Heavy Atom Count   5
Formal Charge   0
Complexity   18.8
Isotope Atom Count   0
Defined Atom Stereocenter Count   0
Undefined Atom Stereocenter Count   0
Defined Bond Stereocenter Count   0
Undefined Bond Stereocenter Count   0
Covalently-Bonded Unit Count   2
Compound Is Canonicalized   Yes

-Synthesis-
E251 (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

-Physical properties-
Colorless crystalline solid; saline taste; trigonal, and rhombohedrals structure; density 2.257g/cm3; refractive index 1.587 (trigonal) and 1.336 (rhombohedral); melts at 308°C; decomposes at 380°C; specific conductance 95 μmhos/cm at 300°C; viscosity 2.85 centipoise at 317°C; very soluble in water 92.1 g/100 mL at 25°C and 180 g/100 mL at 100°C; very soluble in liquid ammonia; soluble in alcohol.

-Characteristics-
PSA： 68.88
XLogP3： 0.2841
Appearance： White or yellow solid
Density： 2.26 g/cm3
Melting Point： 308 °C
Boiling Point： 380 °C
Refractive Index： 1.3404
Water Solubility： H2O: 900 g/L (20 °C)
Storage Conditions： Do not store near combustible materials. Store in a tightly closed container. Store in a cool, dry, well-ventilated area away from incompatible substances.
Toxicity： oral - rat LD50: 1267 mg / kg; cavity - mouse LD50: 175 mg / kg
Explosive limit： Explodes when heated to over 1000 deg C.
Odor： Odorless
Taste： Saline, slightly bitter taste
PH： Aq soln is neutral
Experimental Properties： Dissolved in water temp of soln is lowered; deliquesces in moist air|Liquid Molar volume = 0.044616 cu m/kmol|Heat of formation = -4.6785X10+8 J/kmol|Heat of fusion at 580.15 deg K = 1.4602X10+7 J/kmol|For more Other Experimental Properties (Complete) data for E251 (Sodium nitrate) (8 total), please visit the HSDB record page.
Air and Water Reactions： Soluble in water.
Reactive Group： Nitrate and Nitrite Compounds, Inorganic
Reactivity Alerts： Explosive
Reactivity Profile： A mixture of E251 (Sodium nitrate) and sodium hypophosphite constitute a powerful explosive [Mellor 8, Supp. 1:154 1964].
E251 (Sodium nitrate) and aluminum powder mixtures have been reported to be explosive,[Fire, 1935, 28, 30].
The nitrate appears to be incompatible with barium thiocyanate, antimony, arsenic trioxide/iron(II) sulfate, boron phosphide, calcium-sodium alloy, magnesium, metal amidosulfates, metal cyanides, powdered charcoal, peroxyformic acid, phenol/trifluoroacetic acid, sodium, sodium nitrite/sodium sulfide, sodium phosphinate, sodium thiosulfate, tris( cyclopentadienyl)cerium, and even wood [Bretherick 5th ed., 1995].

-Uses-
Most E251 (Sodium nitrate) is used in fertilizers, where it supplies a water soluble form of nitrogen.
Its use, which is mainly outside of the Western World, 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 E251 (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.
E251 (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, US and Australia and New Zealand.
E251 (Sodium nitrate) should not be confused with sodium nitrite, which is also a common food additive and preservative used, for example, in deli meats.
E251 (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.
Examples of the applications of E251 (Sodium nitrate) used for thermal energy storage include solar thermal power technologies and direct steam generating parabolic troughs.
E251 (Sodium nitrate) is used in a steel coating process in which it forms a surface magnetite layer.

-Health concerns-
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.
Nitrosamines, formed in cured meats containing E251 (Sodium nitrate) and nitrite, have been linked to gastric cancer and esophageal cancer.
E251 (Sodium nitrate) and nitrite are associated with a higher risk of colorectal cancer.
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.

However, several things complicate the otherwise straightforward understanding of "nitrates in food raise your risk of cancer": Commonly consumed plants are well known to be rich sources of nitrates.
In fact, exposure of nitrates from plants may even be higher than meat for most people.
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, and typically not consumed as part of a nutritious, balanced diet with high fiber, vitamins, minerals, and the like. Nitrates are key intermediates and effectors in the primary vasculature signaling which is necessary for all mammals to survive.
E251 (Sodium nitrate) is the oldest known nitrogenous fertilizer.
It is a white, shiny crystal available in nature as Chilean saltpeter or Chilean nitrate.
E251 (Sodium nitrate) is manufactured by two methods. In the first, known as the Guggenheim method, the fertilizer is extracted from a mined product, called caliche, mined mostly in Chile; hence the name (Chilean saltpeter or Chilean nitrate).
The caliche is dissolved in warm water and then cooled to 0°C to produce E251 (Sodium nitrate) crystals, which are circulated through heat exchangers.
The circulation keeps the crystals suspended, to finally form pellets. Caliche mined in Chile, contains E251 (Sodium nitrate) (8 to 20%), potassium and magnesium nitrates and salts like borates, sulphates and chlorides. Approximately, one ton of E251 (Sodium nitrate) of 99% purity is obtained from 10 tons of caliche. E251 (Sodium nitrate) is shipped in airtight containers. The pellets are also coated to impart free-flowing characteristics.
E251 (Sodium nitrate) is also manufactured from nitric acid and soda ash, using salt and oyster shells.
Nitric acid is reacted with soda ash forming E251 (Sodium nitrate) solution.
Most water is removed by evaporation and the rest is heated to a high temperature and sprayed through nozzles.

E251 (Sodium nitrate) solidifies as pellets while coming through the nozzles.
E251 (Sodium nitrate) fertilizer is water-soluble. It contains 16% nitrogen and about 26% sodium.
Plants absorb most of the nitrogen in a nitrate form and E251 (Sodium nitrate) is a commonly preferred fertilizer, although the nitrogen content of E251 (Sodium nitrate) is lesser than that in many other inorganic nitrogen fertilizers.
E251 (Sodium nitrate) has a neutralizing effect on soil acidity because of its inherent basic residual effect.
Its neutralizing value is 0.82 kg of calcium carbonate equivalent to 0.45 kg of E251 (Sodium nitrate).
The field crops which benefit most from E251 (Sodium nitrate) application are sugar beet and cotton.
If applied excessively, E251 (Sodium nitrate) can damage the soil structure by reducing the flocculation.
But normal applications of 100 to 200 kg of fertilizer/hectare/year do not affect the soil structure.

-Toxicity-
ADI 0~3.7 mg/kg (NO3-meter, but do not apply to the baby younger than 3 months FAO/WHO, 2001). LD50 1100～2000mg/kg (rats, through the mouth).
Accordance to the stipulations of GB 2760-86, it can be used in hair color agent and in meat products, the maximum amount is 0.5 g/kg; residues be calculated by sodium nitrite, meat canned must not exceed 0.05 g/kg, meat products shall not be more than 0.03 g/kg.
Infants younger than six months are particularly sensitive to nitrate, do not be used for baby food. HACSG (EC child protection group) suggestions restriction for infants and young children food.
Dust can irritate the lungs and skin. E251 (Sodium nitrate) has the characteristic of reduction to sodium nitrite in body, often resulting in formation of denaturation of hemoglobin, drinking water containing 50~100 RNG/L E251 (Sodium nitrate), denaturation of hemoglobin in the blood rise significantly. Workers operate the production must wear work clothes, protective masks, latex gloves and other labor insurance supplies, in case of dust suction and protect respiratory and skin. Production equipment should be closed and the workshop ventilation is good.

-Content Analysis-
GB 1891-86 method
Principle:
Boiling nitrate and nitrogen alloy (45A150; u5Zn) in strong alkaline solution results in releasing of hydrogen, which reduces nitrogen nitrate (or other nitrogen compounds) to ammonia.
Absorption ammonia with excess sulfuric acid then titration with standard alkali solution.

Reagent and Solution :
Preparation of mixed indicating liquid: Dissolve 0.12 g of methyl red and 0.12 g of methylene blue in 100 ml 95% ethanol solution.
Nitrogen alloy is smashed to pass through a screen of 20 meshes, and the content of alloy can pass through a screen of 80 meshes should not exceed 20%.
Dissolve 14 g (Accurate to 0.0002 g) of fully blended sample in water with a beaker, then transfer into 500 ml volumetric flask, dilute to scale and shake to be a backup.
Use the distillation unit as shown. Draw 50 ml of 0.5 mol/L sulfuric acid solution using straw into 500 ml conical flask, then add 50 ml of water.
Draw 50 ml of prepared liquid sample through a straw into a 1000 ml flat-bottomed distillation flask, then add 7.5 g nitrogen alloy, and 150 ml of water along the wall of bottle.
Join the distillation unit according to the figure, and make the tube 4 hit the end of the bottom of the bottle.
Add 70 ml of sodium hydroxide solution (300 g/L solution) in distillation bottle 1 quickly, immediately insert rubber stopper, reaction after 20 min at room temperature, micro heat 10 min, then high temperature distillation.
After boiling 50~60 min, and obtain about 270 ml of solution in bottle (residual liquid product is about a third of the initial volume), down the conical flask, leave the tip of the tube 4 out of the liquid level inside the conical flask solution, then wash pipe 4 with water, stop heating.
Blank experiment was carried out at the same time under the same conditions in addition to the water replacement of liquid sample.

In the formula, c-concentration of standard sodium hydroxide solution (0.5 mol/L)
Vo-Blank consumption volume of NaOH standard solution, ml;
V-Sample consumption volume of NaOH standard solution, ml;
m-The quality of sample, g;
z-water content measured by the standard, %;
z,-Sodium nitrite content measured by the standard, %;
0.08499-Millimoles quality of sodium nitrite, g;
1.232-The coefficient of sodium nitrite to E251 (Sodium nitrate).

The difference between the two parallel determination results should not be greater than 0.3%. Take the arithmetic mean as the determination results of parallel determination results.
The difference between the different laboratory determination results is not greater than 0.5%.
Notice: Before testing the sample, verification using replacement of potassium nitrate with the same method. Calculation method is as follows.
In the formula, G-The quality of the benchmark potassium nitrate, g;
0.10111-millimoles quality of potassium nitrate, g.
If several analysis results of potassium nitrate were between 99.95%~100.05%, the test equipment is regarded in good condition (at least to be between 99.80%~100.10%).
FAO/WHO method
Accurately weight 0.4 g of sample which has been dried at 105oC for 4 h into a 500 ral round bottom flask, then add 300 ml water. Add 3 g of Devardas alloy powder and 15 ml of 40% sodium hydroxide solution, join the splash ball and condenser on the flask. Stewing for 2h. Use a bottle containing50 ml of 0.1 mol/L sulfate acid to collect 250 ml of distillate, add three drops of methyl red-methylene blue test solution (TS-150), use 0~mol/L sodium hydroxide titration excess sulfuric acid. Blank experiment was carried out at the same time. Every mL0.1 mol/L equivalent to 8.5 mg sulfate E251 (Sodium nitrate) (NaNO3).

-Production Method-

Absorption method:
Bubble the exhaust derived from nitric acid production (contain NO + NO2 0.5%~1.5%) into the bottom of absorption tower, use soda solution with a relative density of 1.240~1.3 and temperature of 25~60 oC spraying from the top of the tower to absorption nitrous oxide in gas, and then obtain the neutralizer.
Add neutralizing liquid and nitric acid into converter, sodium nitrite will transform into E251 (Sodium nitrate), the conversion temperature is between 90~105 oC, stirring with air at the same time.
Using soda solution to neutralize the free acid in converted solution, keeping the alkalinity below 0.3 g/L, in atmospheric evaporation to solution the boiling point of 123~123 oC, through cooling crystallization, centrifugal separation, drying, E251 (Sodium nitrate) is obtained.
Na2CO3+NO+NO2→2NaNO2+CO2↑
Na2CO3+2NO2→NaNO2+NaNO3+CO2↑
3NaNO2+2HNO3→3NaNO3+H2O+2NO↑
Nitrogen gas released from oxidation reaction process can be returned to nitric acid production system to make nitric acid.

Double decomposition method:
Mix 50%~52% of calcium nitrate, sodium sulfate and calcium nitrate solution cycle solution into a stirring reactor, reaction was conducted in the 50~55 oC under stirring for 3~4 h, filter the plaster through vacuum filter, and further filter to remove impurities, remove plaster after been washed with water, wash water merged with the filtrate, part of them return to diluted slurry reactor, and part of them been evaporation and concentration, through cooling crystallization, centrifugal separation and drying, E251 (Sodium nitrate) is obtained.
Ca(NO3)2+Na2SO4→2NaNO3+CaSO4↓

Direct extraction method:
The E251 (Sodium nitrate) ore is broken to a certain size, use fresh water or brine to spray heap leaching, then get a certain concentration of E251 (Sodium nitrate) brine, cooling to separate mirabilite, send brine to evaporation pans tan, until E251 (Sodium nitrate) alum (Na2SO4, NaNO3·H2O) crystal appeared, after filtering, the by-produc of sodium chloride brine continue insolation evaporation to get semi-finished products contained E251 (Sodium nitrate) alum. Melt the semi-finished product with a certain amount of brine (or crystallization mother liquor), after been filtered to remove impurities, filtrated the cooling crystallization, centrifugal separation, drying, E251 (Sodium nitrate) is obtained.

Conversion method:
Sodium nitrite concentration and dilute nitric acid mother liquor are sent into the tower, through steam heating and ventilation with compressed air mixing, then transform into E251 (Sodium nitrate) solution, add soda solution until slightly alkaline solution, then through purification, filtration, removal of arsenic and heavy metals, evaporation and concentration, cooling crystallization, centrifugal separation, drying, the food grade E251 (Sodium nitrate) is obtained.
3NaNO2+2HNO3→3NaNO3+H2O+2NO↑

-Synonyms-
E251 (Sodium nitrate)
7631-99-4
Chile saltpeter
Cubic niter
Nitrate of soda
Soda niter
Sodium saltpeter
Nitrate, sodium
Nitrate de sodium
Nitric acid, sodium salt
Nitric acid monosodium salt
Sodium(I) nitrate (1:1)
sodium;nitrate
Nitric acid sodium salt (1:1)
UNII-8M4L3H2ZVZ
MFCD00011119
8M4L3H2ZVZ
Chili Saltpeter
15621-57-5
CHEMBL1644698
CHEBI:63005
Na (N O3)
E251 (Sodium nitrate)(DOT)
Caswell No. 781
sodiumnitrate
Chile salpeter
Saltpeter (Chile) (VAN)
Nitrate de sodium [French]
CCRIS 558
HSDB 726
NaNO3
EINECS 231-554-3
NSC 77390
UN1498
EPA Pesticide Chemical Code 076104
Natrum nitricum
DSSTox_CID_937
E251 (Sodium nitrate) (NaNO3)
EC 231-554-3
sodium trioxidonitrate(1-)
DSSTox_RID_75877
DSSTox_GSID_20937
E251 (Sodium nitrate), ACS reagent
INS NO.251
E251 (Sodium nitrate), LR, >=98%
DTXSID6020937
INS-251
E251 (Sodium nitrate), ACS reagent grade
E251 (Sodium nitrate), analytical standard
E251 (Sodium nitrate), AR, >=99.5%
Tox21_202595
AKOS015902552
AKOS025243988
E251 (Sodium nitrate), BioXtra, >=99.0%
E251 (Sodium nitrate), beads, 1-2 mm, 98%
E251 (Sodium nitrate), containing in the dry state more than 16,3 per cent by weight of nitrogen
NCGC00260143-01
E251 (Sodium nitrate) [UN1498] [Oxidizer]
E251
E251 (Sodium nitrate), ACS reagent, >=99.0%
CAS-7631-99-4
E251 (Sodium nitrate), 99.999% (metals basis)
E251 (Sodium nitrate), BioUltra, >=99.0% (T)
E-251
E251 (Sodium nitrate), ReagentPlus(R), >=99.0%
E251 (Sodium nitrate), 99.995% trace metals basis
E251 (Sodium nitrate), SAJ first grade, >=99.0%
E251 (Sodium nitrate), JIS special grade, >=99.0%
Q184373
E251 (Sodium nitrate), >=99.0%, plant cell culture tested
E251 (Sodium nitrate), anhydrous, 99.995% trace metals basis
Nitrogen and oxygen isotopes in nitrate, NIST(R) RM 8569
E251 (Sodium nitrate), puriss. p.a., ACS reagent, reag. ISO, >=99.5%
E251 (Sodium nitrate), meets analytical specification of FCC, E251, 99.0-100.5%
E251 (Sodium nitrate), p.a., ACS reagent, reag. ISO, reag. Ph. Eur., 99%
E251 (Sodium nitrate), anhydrous, free-flowing, Redi-Dri(TM), ReagentPlus(R), >=99%