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For nitrates in medicine, see Nitrovasodilator.
Ball-and-stick model of the nitrate ion
CAS number 14797-55-8
PubChem 943
Jmol-3D images Image 1
Molecular formula NO
Molar mass 62.0049 g mol-1
Infobox references

Nitrate is a polyatomic ion with the molecular formula NO3 and a molecular mass of 62.0049 g/mol. Nitrates also describe the organic functional group RONO2. These nitrate esters are a specialized class of explosives.


The nitrate ion. The net charge of the whole ion is 1.

The anion is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of -1. This results from a combination formal charge in which each of the three oxygens carries a −23 charge, whereas the nitrogen carries a 1+ charge, all these adding up to formal charge of the polyatomic nitrate ion. This arrangement is commonly used as an example of resonance. Like the isoelectronic carbonate ion, the nitrate ion can be represented by resonance structures:

Canonical resonance structures for the nitrate ion


The nitrate ion with the partial charges shown

Almost all inorganic nitrate salts are soluble in water at standard temperature and pressure. A common example of an inorganic nitrate salt is potassium nitrate (saltpeter). A rich source of inorganic nitrate in the human body comes from diets rich in leafy green foods, such as spinach and arugula. It is now believed that dietary nitrate in the form of plant-based foods is converted in the body to nitric oxide which reduces hypertension. Anti-hypertensive diets, such as the DASH diet, typically elevates nitric oxide levels which is first reduced to nitrite in the saliva, as detected in saliva testing, prior to forming nitric oxide.


Nitrate salts are found naturally on earth as large deposits, particularly of Nitratine, a major source of sodium nitrate.

Nitrites are produced by a number of species of nitrifying bacteria, and the nitrate compounds for gunpowder (see this topic for more) were historically produced, in the absence of mineral nitrate sources, by means of various fermentation processes using urine and dung. Nitrates are found in man-made fertilizers.


Table tennis balls are made from celluloid, an organic nitrate.







Nitrate toxicosis can occur through enterohepatic metabolism of nitrate to nitrite being an intermediate.[2] Nitrites oxidize the iron atoms in hemoglobin from ferrous iron (2+) to ferric iron (3+), rendering it unable to carry oxygen.[3] This process can lead to generalized lack of oxygen in organ tissue and a dangerous condition called methemoglobinemia. Although nitrite converts to ammonia, if there is more nitrite than can be converted, the animal slowly suffers from a lack of oxygen.[4]

Human health effects[edit]


Some adults can be more susceptible to the effects of nitrates than others. The methemoglobin reductase enzyme may be under-produced or absent in certain people that have an inherited mutation.[8] Such individuals cannot break down methemoglobin as rapidly as those that do have the enzyme, leading to increased circulating levels of methemoglobin (the implication being that their blood is not as oxygen-rich). Those with insufficient stomach acid[8] (including some vegetarians and vegans) may also be at risk. It is the increased consumption of green, leafy vegetables that typically accompany these types of diets may lead to increased nitrate intake. A wide variety of medical conditions, including food allergies, asthma,[9] hepatitis, and gallstones may be linked with low stomach acid; these individuals may also be highly sensitive to the effects of nitrate.

Methemoglobinemia can be treated with methylene blue, which reduces ferric iron (3+) in affected blood cells back to ferrous iron (2+).[10]

Marine toxicity[edit]

Sea surface nitrate from the World Ocean Atlas.

In freshwater or estuarine systems close to land, nitrate can reach high levels that can potentially cause the death of fish. While nitrate is much less toxic than ammonia,[11] levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species.[12] However, in light of inherent problems with past protocols on acute nitrate toxicity experiments, the extent of nitrate toxicity has been the subject of recent debate.[13]



Category  %NO3  %NO3-N  %KNO3 Effects
1 <0.5 <0.12 <0.81 Generally safe for beef cattle and sheep
2 0.5-1.0 0.12-0.23 0.81-1.63 Caution - some subclinical symptoms may appear in pregnant horses, sheep and beef cattle
3 1.0 0.23 1.63 High nitrate problems - death losses and abortions can occur in beef cattle and sheep
4 <1.23 <0.28 <2.00 Maximum safe level for horses. Do not feed high nitrate forages to pregnant mares

The values above are on a dry (moisture free) basis.

Nitrate overview[edit]

Nitrate formation with elements of the periodic table.

LiNO3 Be(NO3)2 B(NO3)3 C N O F Ne
KNO3 Ca(NO3)2 Sc(NO3)3 Ti V Cr(NO3)3 Mn(NO3)2 Fe(NO3)3 Co(NO3)2, Co(NO3)3 Ni(NO3)2 Cu(NO3)2 Zn(NO3)2 Ga(NO3)3 Ge As Se Br Kr
RbNO3 Sr(NO3)2 Y Zr Nb Mo Tc Ru Rh Pd(NO3)2 AgNO3 Cd(NO3)2 In Sn Sb Te I Xe
CsNO3 Ba(NO3)2 Hf Ta W Re Os Ir Pt Au Hg2(NO3)2, Hg(NO3)2 Tl(NO3)3 Pb(NO3)2 Bi(NO3)3 Po At Rn
La Ce Pr Nd Pm Sm Eu Gd(NO3)3 Tb Dy Ho Er Tm Yb Lu

See also[edit]


  1. ^ Wolfgang Laue, Michael Thiemann, Erich Scheibler, Karl Wilhelm Wiegand "Nitrates and Nitrites" in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_265
  2. ^ "Nitrate and Nitrite Poisoning: Introduction". The Merck Veterinary Manual. Retrieved 2008-12-27. 
  3. ^ Kim-shapiro, D. B.; Gladwin, M. T.; Patel, R. P.; Hogg, N. (2005). "… between nitrite and hemoglobin: the role of nitrite in hemoglobin-mediated hypoxic vasodilation". Journal of Inorganic Biochemistry 99 (1): 237–246. doi:10.1016/j.jinorgbio.2004.10.034. PMID 15598504. 
  4. ^ Stoltenow, Charlie and Greg Lardy (May 2008). "Nitrate Poisoning of Livestock". North Dakota State University. pp. 1–4. Retrieved October 30, 2013. 
  5. ^ T. M. Addiscott & N. Benjamin 2004 "Nitrate and human health"
  6. ^ A. A. Avery "Infant Methemoglobemia - reexamining the role of drinking water nitrates"
  7. ^ Marschner H 1999 Mineral nutrition of higher plants. Academic Press, London. 889
  8. ^ a b "Q&A: Nitrate in Drinking Water" (in (English), (Spanish)). Washington State Department of Health. DOH-331-214. Retrieved 9 June 2013. 
  9. ^ "GERD and Asthma". Retrieved September 2, 2009. 
  10. ^ "Methemoglobinemia". The New York Times. Retrieved 31 October 2013. 
  11. ^ Romano, N.; Zeng, C. (2007). "Acute toxicity of sodium nitrate, potassium nitrate and potassium chloride and their effects on the hemolymph composition and gill structure of early juvenile blue swimmer crabs (Portunus pelagicus, Linnaeus 1758) (Decapoda, Brachyura, Portunidae)". Environmental Toxicology and Chemistry 26: 1955–1962. doi:10.1897/07-144r.1. 
  12. ^ Sharpe, Shirlie. "Nitrates in the Aquarium". Retrieved October 30, 2013. 
  13. ^ Romano N., Zeng, C. (2007). "Effects of potassium on nitrate mediated changes to osmoregulation in marine crabs". Aquatic Toxicology 85 (3): 202–208. doi:10.1016/j.aquatox.2007.09.004. PMID 17942166. 
  14. ^ "Nitrate Risk in Forage Crops - Frequently Asked Questions". Agriculture and Rural Development. Government of Alberta. Retrieved October 30, 2013. 

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