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{{About||NH4+|Ammonium|other uses}}{{short description|Chemical compound of nitrogen and hydrogen}}{{Use dmy dates|date=March 2015}}{{Use British English|date=May 2012}}{{Chembox| Watchedfields = changed| verifiedrevid = 464364488| ImageFileL1 = Ammonia-3D-balls-A.png| ImageNameL1 = Ball-and-stick model of the ammonia molecule| ImageFileR1 = Ammonia-3D-vdW.png| ImageNameR1 = Space-filling model of the ammonia molecule| ImageFile2 = Ammonia-2D.svg| ImageName2 = Stereo structural formula of the ammonia molecule! Concentrationby weight (w/w)! Molarity! Concentrationmass/volume (w/v)! Classification! R-phrases| 5–10%| 2.87–5.62 mol/L| 48.9–95.7 g/L| Irritant (Xi)| {{R36/37/38}}| 10–25%| 5.62–13.29 mol/L| 95.7–226.3 g/L| Corrosive (C)| {{R34}}| >25%| >13.29 mol/L| >226.3 g/L
correct|CAS}}| PubChem = 222correct|EBI}}| ChEMBL = 1160819| ChemSpiderID = 217correct|chemspider}}| UNII = 5138Q19F1Xcorrect|FDA}}| EINECS = 231-635-3| UNNumber = 1005| KEGG = D02916correct|kegg}}| MeSHName = Ammoniacorrect|EBI}}| ChEBI = 16134| RTECS = BO0875000| SMILES = Ncorrect|chemspider}}| StdInChI = 1S/H3N/h1H3correct|chemspider}}| StdInChIKey = QGZKDVFQNNGYKY-UHFFFAOYSA-N| Beilstein = 3587154| Gmelin = 79| 3DMet = B00004}}|Section2={{Chembox Properties| Formula = NH3| MolarMass = 17.031 g/mol| Appearance = Colourless gas| Odour = strong pungent odour| Density = 0.86 kg/m3 (1.013 bar at boiling point)681.9 kg/m3 at −33.3 Â°C (liquid)BOOK,weblink 132, Systematic Inorganic Chemistry, Yost, Don M., Ammonia and Liquid Ammonia Solutions, READ BOOKS, 2007, 978-1-4067-7302-6, See also Ammonia (data page)817 kg/m3 at −80 Â°C (transparent solid)JOURNAL, 10.1080/00337577508240819, On crystalline character of transparent solid ammonia, 1975, Blum, Alexander, Radiation Effects and Defects in Solids, 24, 4, 277, | MeltingPtC = −77.73| MeltingPt_notes = (Triple point at 6.060 kPa, 195.4 K)| BoilingPtC = −33.34132.4K}}, {{convertatmabbr=on}}EDITOR-LAST=BUDAVARIPUBLISHER=MERCKISBN=978-0-911910-12-4, chloroform, diethyl ether>ether, ethanol, methanol| Solvent =| pKa = 32.5 (−33 Â°C),Perrin, D. D., Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution; 2nd Ed., Pergamon Press: Oxford, 1982. 10.5 (DMSO)| pKb = 4.75| ConjugateAcid = Ammonium| ConjugateBase = Azanide| RefractIndex = 1.3327
  • 10.07 μPa·s (25 Â°C)JOURNAL, Iwasaki, Hiroji, Takahashi, Mitsuo, Studies on the transport properties of fluids at high pressure, The Review of Physical Chemistry of Japan, 38, 1, 1968,
  • 0.276 mPa·s (−40 Â°C)}}| VaporPressure = 857.3 kPa| MagSus = −18.0·10−6 cm3/mol
}}|Section3={{Chembox Structure
Trigonal pyramid (chemistry)>Trigonal pyramidDebye>D| PointGroup = C3v}}|Section4={{Chembox ThermochemistryPUBLISHER = HOUGHTON MIFFLIN COMPANY ISBN = 978-0-618-94690-7, A22, | Entropy = 193 J·mol−1·K−1
}}|Section7={hide}Chembox Hazards
GHS05{edih}{{GHSpGHS09}}{{Sigma-Aldrichname=Ammonia|accessdate=20 July 2013}}221314400}}210273305+351+338|310}}| ExternalSDS = ICSC 0414 (anhydrous)| NFPA-H = 3| NFPA-F = 1| NFPA-R = 0| NFPA-S =| FlashPt = flammable gas| AutoignitionPtC = 651| ExploLimits = 15–28%0028}}| PEL = 50 ppm (25 ppm ACGIH- TLV; 35 ppm STEL)| LD50 = 0.015 mL/kg (human, oral)| REL = TWA 25 ppm (18 mg/m3) ST 35 ppm (27 mg/m3)| IDLH = 300 ppm7664417|Ammonia}}| LCLo = 5000 ppm (mammal, 5 min)5000 ppm (human, 5 min)}}|Section8={{Chembox Related| OtherAnions =| OtherCations = PhosphineArsineStibine| OtherFunction = HydrazineHydrazoic acid| OtherFunction_label = nitrogen hydrides| OtherCompounds = Ammonium hydroxide}}}}Ammonia is a compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a characteristic pungent smell. It is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceutical products and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water. Ammonia is named for the Ammonians, worshipers of the Egyptian god Amun, who used ammonium chloride in their rituals.WEB,weblink Ammonia, Although common in nature—both terrestrially and in the outer planets of the Solar System—and in wide use, ammonia is both caustic and hazardous in its concentrated form. It is classified as an extremely hazardous substance in the United States, and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.JOURNAL, United States Government Publishing Office, Government Printing Office, 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities,weblink 1 July 2008, 29 October 2011,weblink" title="">weblink 25 February 2012, dead, The global industrial production of ammonia in 2014 was 176 million tonnes,WEB,weblink pg. 119 – Nitrogen, USGS, 2016, 17 February 2016, a 16% increase over the 2006 global industrial production of 152 million tonnes.WEB,weblink Nitrogen, USGS, 2016, PDF, 17 February 2016, Industrial ammonia is sold either as ammonia liquor (usually 28% ammonia in water) or as pressurized or refrigerated anhydrous liquid ammonia transported in tank cars or cylinders.BOOK, R. Norris Shreve, Joseph Brink, Joseph Brink, Chemical Process Industries, 1977, 978-0-07-057145-7, 276, 4th, R. Norris Shreve, See also Gas carrier and Bottled gas.NH3 boils at {{convert|−33.34|°C|°F|3}} at a pressure of one atmosphere, so the liquid must be stored under pressure or at low temperature. Household ammonia or ammonium hydroxide is a solution of NH3 in water. The concentration of such solutions is measured in units of the Baumé scale (density), with 26 degrees Baumé (about 30% (by weight) ammonia at {{convert|15.5|°C|°F|disp=or}}) being the typical high-concentration commercial product.WEB,weblinkweblink" title="">weblink 27 November 2007, Ammonium hydroxide physical properties,

Natural occurrence

Ammonia is a chemical found in trace quantities in nature, being produced from nitrogenous animal and vegetable matter. Ammonia and ammonium salts are also found in small quantities in rainwater, whereas ammonium chloride (sal ammoniac), and ammonium sulfate are found in volcanic districts; crystals of ammonium bicarbonate have been found in Ronak guano.{{sfn|Chisholm|1911|p=861}} The kidneys secrete ammonia to neutralize excess acid.JOURNAL, 10360635, 1999, Kirschbaum, B, Sica, D, Anderson, F. P., Urine electrolytes and the urine anion and osmolar gaps., 133, 6, 597–604, 0022-2143, The Journal of Laboratory and Clinical Medicine, 10.1016/S0022-2143(99)90190-7, Ammonium salts are found distributed through fertile soil and in seawater.Ammonia is also found throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as {{convert|173|K|C F}} if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone.Shannon, Francis Patrick (1938) Tables of the properties of aqua-ammonia solutions. Part 1 of The Thermodynamics of Absorption Refrigeration. Lehigh University studies. Science and technology seriesAn ammonia-water slurry may swirl below Pluto's icy surface. Purdue University (9 November 2015) Substances containing ammonia, or those that are similar to it, are called ammoniacal.


Ammonia is a colourless gas with a characteristic pungent smell. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules; the liquid boils at {{convert|-33.3|°C|°F|2}}, and freezes at {{convert|-77.7|°C|°F|2}} to white crystals.{{sfn|Chisholm|1911|p=861}}Ammonia may be conveniently deodorized by reacting it with either sodium bicarbonate or acetic acid. Both of these reactions form an odourless ammonium salt.
Solid: The crystal symmetry is cubic, Pearson symbol cP16, space group P213 No.198, lattice constant 0.5125 nm.JOURNAL, 10.1107/S0567739479001340, The crystal structure of deuteroammonia between 2 and 180 K by neutron powder profile refinement, 1979, Hewat, A. W., Riekel, C., Acta Crystallographica Section A, 35, 4, 569, 1979AcCrA..35..569H,
Liquid: Liquid ammonia possesses strong ionising powers reflecting its high ε of 22. Liquid ammonia has a very high standard enthalpy change of vaporization (23.35 kJ/mol, cf. water 40.65 kJ/mol, methane 8.19 kJ/mol, phosphine 14.6 kJ/mol) and can therefore be used in laboratories in uninsulated vessels without additional refrigeration. See liquid ammonia as a solvent.
Solvent properties: Ammonia is miscible with water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic. The maximum concentration of ammonia in water (a saturated solution) has a density of 0.880 g/cm3 and is often known as '.880 ammonia'.
Combustion: Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-air mixtures of 15–25% air. When mixed with oxygen, it burns with a pale yellowish-green flame. At high temperature and in the presence of a suitable catalyst, ammonia is decomposed into its constituent elements. Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride; if chlorine is present in excess, then the highly explosive nitrogen trichloride (NCl3) is also formed.


The ammonia molecule has a trigonal pyramidal shape as predicted by the valence shell electron pair repulsion theory (VSEPR theory) with an experimentally determined bond angle of 106.7°.BOOK, Haynes, William M., 2013, CRC Handbook of Chemistry and Physics, 94th, CRC Press, 9781466571143, 9–26, CRC Handbook of Chemistry and Physics, The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair of electrons repel more strongly than bond pairs, therefore the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°. The nitrogen atom in the molecule has a lone electron pair, which makes ammonia a base, a proton acceptor. This shape gives the molecule a dipole moment and makes it polar. The molecule's polarity, and especially, its ability to form hydrogen bonds, makes ammonia highly miscible with water. Ammonia is moderately basic, a 1.0 M aqueous solution has a pH of 11.6 and if a strong acid is added to such a solution until the solution is neutral (pH = 7), 99.4% of the ammonia molecules are protonated. Temperature and salinity also affect the proportion of NH4+. The latter has the shape of a regular tetrahedron and is isoelectronic with methane.The ammonia molecule readily undergoes nitrogen inversion at room temperature; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the resonance frequency is 23.79 GHz, corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed.JOURNAL, 10.1103/PhysRev.45.234, Electromagnetic Waves of {{convert, 1.1, cm, 0, on, . Wave-Length and the Absorption Spectrum of Ammonia|year=1934|author=Cleeton, C. E.|journal=Physical Review|volume=45|issue=4|pages=234|first2=N. H.|last2=Williams|bibcode = 1934PhRv...45..234C }}


One of the most characteristic properties of ammonia is its basicity. Ammonia is considered to be a weak base. It combines with acids to form salts; thus with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid, ammonium nitrate, etc. Perfectly dry ammonia will not combine with perfectly dry hydrogen chloride; moisture is necessary to bring about the reaction.{{sfn|Chisholm|1911|p=862}}JOURNAL, Influence of moisture on chemical change, Baker, H. B., 1894, J. Chem. Soc., 65, 611–624, 10.1039/CT8946500611,weblink As a demonstration experiment, opened bottles of concentrated ammonia and hydrochloric acid produce clouds of ammonium chloride, which seem to appear "out of nothing" as the salt forms where the two diffusing clouds of molecules meet, somewhere between the two bottles.{{block indent|NH3 + HCl → NH4Cl}}The salts produced by the action of ammonia on acids are known as the (:Category:Ammonium compounds|ammonium salts) and all contain the ammonium ion (NH4+).{{sfn|Chisholm|1911|p=862}}Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the NH2− ion). For example, lithium dissolves in liquid ammonia to give a solution of lithium amide:{{block indent|2Li + 2NH3 → 2LiNH2 + H2}}


Like water, ammonia undergoes molecular autoionisation to form its acid and base conjugates:{{block indent|2 {{chem|NH|3}} {{eqm}} {{chem|NH|4|+}} + {{chem|NH|2|-}}}}Ammonia often functions as a weak base, so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations ({{chem|NH|4|+}}) and amide anions ({{chem|NH|2|-}}) to be present in solution. At standard pressure and temperature, K=[{{chem|NH|4|+}}][{{chem|NH|2|-}}] = 10{{su|p=−30}}


The combustion of ammonia to nitrogen and water is exothermic:{{block indent|1=4 NH3 + 3 O2 → 2 N2 + 6 H2O (g) ΔH°r = −1267.20 kJ/mol (or −316.8 kJ/mol if expressed per mol of NH3)}}The standard enthalpy change of combustion, ΔH°c, expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion: all nitrogen oxides are unstable with respect to N2 and O2, which is the principle behind the catalytic converter. Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts, a reaction of great industrial importance in the production of nitric acid:{{block indent|4 NH3 + 5 O2 → 4 NO + 6 H2O}}A subsequent reaction leads to NO2:{{block indent|2 NO + O2 → 2 NO2}}The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide), due to the relatively low heat of combustion, a lower laminar burning velocity, high auto-ignition temperature, high heat of vaporization, high toxicity, and a narrow flammability range. However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production.JOURNAL, Kobayashi, Hideaki, Hayakawa, Akihiro, Somarathne, K.D. Kunkuma A., Okafor, Ekenechukwu C., Science and technology of ammonia combustion, Proceedings of the Combustion Institute, 2019, 37, 109–133, 10.1016/j.proci.2018.09.029, The flammable range of ammonia in dry air is 15.15%-27.35% and in 100% relative humidity air is 15.95%-26.55%.BOOK, Khan, A.S., Kelley, R.D., Chapman, K.S., Fenton, D.L., Flammability limits of ammonia-air mixtures, 1995, U.S. DOE Office of Scientific and Technical Information, U.S., 215703, For studying the kinetics of ammonia combustion a detailed reliable reaction mechanism is required, however knowledge about ammonia chemical kinetics during combustion process has been challenging.JOURNAL, Shrestha, Krishna P., Seidel, Lars, Zeuch, Thomas, Mauss, Fabian, 2018-07-07, Detailed Kinetic Mechanism for the Oxidation of Ammonia Including the Formation and Reduction of Nitrogen Oxides, Energy & Fuels, 32, 10, 10202–10217, 10.1021/acs.energyfuels.8b01056, 0887-0624,

Formation of other compounds

In organic chemistry, ammonia can act as a nucleophile in substitution reactions. Amines can be formed by the reaction of ammonia with alkyl halides, although the resulting -NH2 group is also nucleophilic and secondary and tertiary amines are often formed as byproducts. An excess of ammonia helps minimise multiple substitution and neutralises the hydrogen halide formed. Methylamine is prepared commercially by the reaction of ammonia with chloromethane, and the reaction of ammonia with 2-bromopropanoic acid has been used to prepare racemic alanine in 70% yield. Ethanolamine is prepared by a ring-opening reaction with ethylene oxide: the reaction is sometimes allowed to go further to produce diethanolamine and triethanolamine.Amides can be prepared by the reaction of ammonia with carboxylic acid derivatives. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be dehydrated to amides so long as there are no thermally sensitive groups present: temperatures of 150–200 Â°C are required.The hydrogen in ammonia is susceptible to replacement by myriad substituents. When heated with sodium it converts to sodamide, NaNH2.{{sfn|Chisholm|1911|p=862}}. With chlorine, monochloramine is formed.Pentavalent ammonia is known as λ5-amine, or more commonly, ammonium hydride. This crystalline solid is only stable under high pressure and decomposes back into trivalent ammonia and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966.NEWS,weblink High pressure chemistry of hydrogenous fuels, Sterrett, K. F., Caron, A. P., Northrop Space Labs, 1966, 24 December 2009,weblink" title="">weblink 23 August 2011, dead, dmy-all,

Ammonia as a ligand

File:Tetraamminediaquacopper(II)-3D-balls.png|thumb|Ball-and-stick modelBall-and-stick modelAmmonia can act as a ligand in transition metal complexes. It is a pure σ-donor, in the middle of the spectrochemical series, and shows intermediate hard-soft behaviour. For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds. Some notable ammine complexes include tetraamminediaquacopper(II) ([Cu(NH3)4(H2O)2]2+), a dark blue complex formed by adding ammonia to a solution of copper(II) salts. Tetraamminediaquacopper(II) hydroxide is known as Schweizer's reagent, and has the remarkable ability to dissolve cellulose. Diamminesilver(I) ([Ag(NH3)2]+) is the active species in Tollens' reagent. Formation of this complex can also help to distinguish between precipitates of the different silver halides: silver chloride (AgCl) is soluble in dilute (2M) ammonia solution, silver bromide (AgBr) is only soluble in concentrated ammonia solution, whereas silver iodide (AgI) is insoluble in aqueous ammonia.Ammine complexes of chromium(III) were known in the late 19th century, and formed the basis of Alfred Werner's revolutionary theory on the structure of coordination compounds. Werner noted only two isomers (fac- and mer-) of the complex [CrCl3(NH3)3] could be formed, and concluded the ligands must be arranged around the metal ion at the (wikt:vertex|vertices) of an octahedron. This proposal has since been confirmed by X-ray crystallography.An ammine ligand bound to a metal ion is markedly more acidic than a free ammonia molecule, although deprotonation in aqueous solution is still rare. One example is the Calomel reaction, where the resulting amidomercury(II) compound is highly insoluble.{{block indent|HgCl2 + 2 NH3 →HgCl(NH2) + NH4Cl}}

Detection and determination

{{about|section=true|detection in the laboratory|detection in astronomy|#In astronomy}}

Ammonia in solution

Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution, which gives a distinct yellow colouration in the presence of the slightest trace of ammonia or ammonium salts. The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium or potassium hydroxide, the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically; or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate, (NH4)2PtCl6.{{sfn|Chisholm|1911|p=863}}

Gaseous ammonia

Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with quicklime, when the characteristic smell of ammonia will be at once apparent.{{sfn|Chisholm|1911|p=863}} Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm, and lethal above 500 ppm.(OSHA) Source: Sax, N. Irving (1984) Dangerous Properties of Industrial Materials. 6th Ed. Van Nostrand Reinhold. {{ISBN|0-442-28304-0}}. Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume.JOURNAL, Hurtado, J. L. Martinez, Lowe, C. R., Ammonia-Sensitive Photonic Structures Fabricated in Nafion Membranes by Laser Ablation, ACS Applied Materials & Interfaces, 6, 11, 2014, 8903–8908, 1944-8244, 10.1021/am5016588, 24803236,

Ammoniacal nitrogen (NH3-N)

Ammoniacal nitrogen (NH3-N) is a measure commonly used for testing the quantity of ammonium ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids. It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man-made water reserves. It is measured in units of mg/L (milligram per litre).


File:Ammoniak Reaktor BASF.jpg|thumb|upright|This high-pressure reactor was built in 1921 by BASF in Ludwigshafen and was re-erected on the premises of the University of KarlsruheUniversity of KarlsruheThe ancient Greek historian Herodotus mentioned that there were outcrops of salt in an area of Libya that was inhabited by a people called the "Ammonians" (now: the Siwa oasis in northwestern Egypt, where salt lakes still exist).Herodotus with George Rawlinson, trans., The History of Herodotus (New York, New York: Tandy-Thomas Co., 1909), vol.2, Book 4, § 181, pp. 304–305.The land of the Ammonians is mentioned elsewhere in Herodotus' History and in Pausanias' Description of Greece:
  • Herodotus with George Rawlinson, trans., The History of Herodotus (New York, New York: Tandy-Thomas Co., 1909), vol. 1, Book 2, § 42, p. 245, vol. 2, Book 3, § 25, p. 73, and vol. 2, Book 3, § 26, p. 74.
  • Pausanias with W.H.S. Jones, trans., Description of Greece (London, England: William Heinemann Ltd., 1979), vol. 2, Book 3, Ch. 18, § 3, pp. 109 and 111 and vol. 4, Book 9, Ch. 16, § 1, p. 239. The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors Dioscorides, Apicius, Arrian, Synesius, and Aëtius of Amida described this salt as forming clear crystals that could be used for cooking and that were essentially rock salt.Kopp, Hermann, Geschichte der Chemie [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, p. 237. [in German] Hammoniacus sal appears in the writings of Pliny,{{harvnb|Chisholm|1911}} cites Pliny Nat. Hist. xxxi. 39. See: Pliny the Elder with John Bostock and H. T. Riley, ed.s, The Natural History (London, England: H. G. Bohn, 1857), vol. 5, Book 31, § 39, p. 502. although it is not known whether the term is identical with the more modern sal ammoniac (ammonium chloride).{{sfn|Chisholm|1911|p=861}}WEB,weblink Sal-ammoniac, Webmineral, 7 July 2009, Pliny also mentioned that when some samples of what was purported to be natron (Latin: nitrum, impure sodium carbonate) were treated with lime (calcium carbonate) and water, the natron would emit a pungent smell, which some authors have interpreted as signifying that the natron either was ammonium chloride or was contaminated with it. See:
  • Pliny with W.H.S. Jones, trans., Natural History (London, England: William Heinemann Ltd., 1963), vol. 8, Book 31, § 46, pp. 448–449. From pp. 448–449: "Adulteratur in Aegypto calce, deprehenditur gusto. Sincerum enim statim resolvitur, adulteratum calce pungit et asperum [or aspersum] reddit odorem vehementer." (In Egypt it [i.e., natron] is adulterated with lime, which is detected by taste ; for pure natron melts at once, but adulterated natron stings because of the lime, and emits a strong, bitter odour [or: when sprinkled [(aspersum) with water] emits a vehement odour])
  • Kidd, John, Outlines of Mineralogy (Oxford, England: N. Bliss, 1809), vol. 2, p. 6.
  • Moore, Nathaniel Fish, Ancient Mineralogy: Or, An Inquiry Respecting Mineral Substances Mentioned by the Ancients: … (New York, New York: G. & C. Carvill & Co., 1834), pp. 96–97.
The fermentation of urine by bacteria produces a solution of ammonia; hence fermented urine was used in Classical Antiquity to wash cloth and clothing, to remove hair from hides in preparation for tanning, to serve as a mordant in dying cloth, and to remove rust from iron.See:
  • Forbes, R.J., Studies in Ancient Technology, vol. 5, 2nd ed. (Leiden, Netherlands: E.J. Brill, 1966), pp. 19, 48, and 65.
  • Moeller, Walter O., The Wool Trade of Ancient Pompeii (Leiden, Netherlands: E.J. Brill, 1976), p. 20.
  • Faber, G.A. (pseudonym of: Goldschmidt, Günther) (May 1938) "Dyeing and tanning in classical antiquity," Ciba Review, 9 : 277–312. Available at: Elizabethan Costume
  • Smith, William, A Dictionary of Greek and Roman Antiquities (London, England: John Murray, 1875), article: "Fullo" (i.e., fullers or launderers), pp. 551–553.
  • Rousset, Henri (31 March 1917) "The laundries of the Ancients," Scientific American Supplement, 83 (2152) : 197.
  • Bond, Sarah E., Trade and Taboo: Disreputable Professions in the Roman Mediterranean (Ann Arbor, Michigan: University of Michigan Press, 2016), p. 112.
  • Binz, Arthur (1936) "Altes und Neues über die technische Verwendung des Harnes" (Ancient and modern [information] about the technological use of urine), Zeitschrift für Angewandte Chemie, 49 (23) : 355–360. [in German]
  • Witty, Michael (December 2016) "Ancient Roman urine chemistry," Acta Archaeologica, 87 (1) : 179–191. Witty speculates that the Romans obtained ammonia in concentrated form by adding wood ash (impure potassium carbonate) to urine that had been fermented for several hours. Struvite (magnesium ammonium phosphate) is thereby precipitated, and the yield of struvite can be increased by then treating the solution with bittern, a magnesium-rich solution that is a byproduct of making salt from sea water. Roasting struvite releases ammonia vapors.
In the form of sal ammoniac (نشادر, nushadir) ammonia was important to the Muslim alchemists as early as the 8th century, first mentioned by the Persian-Arab chemist Jābir ibn Hayyān,BOOK, Haq, Syed Nomanul, Names, Natures and Things: The Alchemist Jabir Ibn Hayyan and His Kitab Al-Ahjar (Book of Stones),weblink 22 June 2010, 28 February 1995, Springer, 978-0-7923-3254-1, and to the European alchemists since the 13th century, being mentioned by Albertus Magnus.{{sfn|Chisholm|1911|p=861}} It was also used by dyers in the Middle Ages in the form of fermented urine to alter the colour of vegetable dyes. In the 15th century, Basilius Valentinus showed that ammonia could be obtained by the action of alkalis on sal ammoniac.Spiritus salis urinæ (spirit of the salt of urine, i.e., ammonium carbonate) had apparently been produced before Valentinus, although he presented a new, simpler method for preparing it in his book: Valentinus, Basilius, Vier Tractätlein Fr. Basilii Valentini … [Four essays of Brother Basil Valentine … ] (Frankfurt am Main, (Germany): Luca Jennis, 1625), "Supplementum oder Zugabe" (Supplement or appendix), pp. 80–81: "Der Weg zum Universal, damit die drei Stein zusammen kommen." (The path to the Universal, so that the three stones come together.). From p. 81: "Der Spiritus salis Urinæ nimbt langes wesen zubereiten / dieser proceß aber ist waß leichter unnd näher auß dem Salz von Armenia, … Nun nimb sauberen schönen Armenischen Salz armoniac ohn alles sublimiren / thue ihn in ein Kolben / giesse ein Oleum Tartari drauff / daß es wie ein Muß oder Brey werde / vermachs baldt / dafür thu auch ein grosen vorlag / so lege sich als baldt der Spiritus Salis Urinæ im Helm an Crystallisch … " (Spirit of the salt of urine [i.e., ammonium carbonate] requires a long method [i.e., procedure] to prepare; this [i.e., Valentine’s] process [starting] from the salt from Armenia [i.e., ammonium chloride], however, is somewhat easier and shorter … Now take clean nice Armenian salt, without sublimating all [of it]; put it in a [distillation] flask; pour oil of tartar [i.e., potassium carbonate that has dissolved only in the water that it has absorbed from the air] on it, [so] that it [i.e., the mixture] becomes like a mush or paste; assemble it [i.e., the distilling apparatus (alembic)] quickly; for that [purpose] connect a large receiving flask; then soon spirit of the salt of urine deposits as crystals in the "helmet" [i.e., the outlet for the vapors, which is atop the distillation flask] … )See also: Kopp, Hermann, Geschichte der Chemie [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, p. 243. [in German]
At a later period, when sal ammoniac was obtained by distilling the hooves and horns of oxen and neutralizing the resulting carbonate with hydrochloric acid, the name "spirit of hartshorn" was applied to ammonia.{{sfn|Chisholm|1911|p=861}}BOOK,weblink 72, Historical Studies in the Language of Chemistry, Maurice P. Crosland, Courier Dover Publications, 2004, 978-0-486-43802-3,
Gaseous ammonia was first isolated by Joseph Black in 1756 by reacting sal ammoniac (Ammonium Chloride) with calcined magnesia (Magnesium Oxide).BOOK,weblink Experiments upon magnesia alba, quick-lime, and other alcaline substances, Black, Joseph, 1893, W.F. Clay, Edinburgh, 1755, BOOK,weblink Air Pollution and Global Warming: History, Science, and Solutions, Jacobson, Mark Z., 2012-04-23, Cambridge University Press, 9781107691155, en, It was isolated again by Peter Woulfe in 1767,NEWS,weblink Woulfe's bottle, Chemistry World, 2017-07-01, en, JOURNAL, Woulfe, Peter, 1767-01-01, Experiments on the Distillation of Acids, Volatile Alkalies, &c. Shewing How They May be Condensed without Loss, and How Thereby We May Avoid Disagreeable and Noxious Fumes: In a Letter from Mr. Peter Woulfe, F. R. S. to John Ellis, Esq; F. R. S.,weblink Philosophical Transactions, en, 57, 517–536, 10.1098/rstl.1767.0052, 0261-0523, by Carl Wilhelm Scheele in 1770DOCUMENT, 1811/28946/Pictorial%20Life%20History_Scheele.pdf, Pictorial life history of the apothecary chemist Carl Wilhelm Scheele, American Institute of the History of Pharmacy, 1942, and by Joseph Priestley in 1773 and was termed by him "alkaline air".{{sfn|Chisholm|1911|p=861}}See:
  • Priestley, Joseph (1773) "Extrait d'une lettre de M. Priestley, en date du 14 Octobre 1773" (Extract of a letter from Mr. Priestley, dated 14 October 1773), Observations sur la Physique …, 2 : 389.
  • Priestley, Joseph, Experiments and Observations on Different Kinds of Air, vol. 1, 2nd ed. (London, England: 1775), Part 2, § 1: Observations on Alkaline Air, pp. 163–177.
  • Schofield, Robert E., The Enlightened Joseph Priestley: A Study of His Life and Work from 1773 to 1804 (University Park, Pennsylvania: Pennsylvania State University Press, 2004), pp. 93–94.
  • By 1775, Priestley had observed that electricity could decompose ammonia ("alkaline air"), yielding a flammable gas (hydrogen). See: Priestley, Joseph, Experiments and Observations on Different Kinds of Air, vol. 2 (London, England: J. Johnson, 1775), pp. 239–240. Eleven years later in 1785, Claude Louis Berthollet ascertained its composition.Berthollet (1785) "Analyse de l'alkali volatil" (Analysis of volatile alkali), Mémoires de l'Académie Royale des Sciences, 316–326.{{sfn|Chisholm|1911|p=861}}
The Haber–Bosch process to produce ammonia from the nitrogen in the air was developed by Fritz Haber and Carl Bosch in 1909 and patented in 1910. It was first used on an industrial scale in Germany during World War I,BOOK, Max Appl, Ammonia, in Ullmann's Encyclopedia of Industrial Chemistry, 2006, Wiley-VCH, Weinheim, 10.1002/14356007.a02_143.pub2, Ammonia, 978-3527306732, following the allied blockade that cut off the supply of nitrates from Chile. The ammonia was used to produce explosives to sustain war efforts.BOOK, Smith, Roland, Conquering Chemistry, 2001, 978-0-07-470146-1, McGraw-Hill, Sydney, Before the availability of natural gas, hydrogen as a precursor to ammonia production was produced via the electrolysis of water or using the chloralkali process.With the advent of the steel industry in the 20th century, ammonia became a byproduct of the production of coking coal.



Globally, approximately 88% (as of 2014) of ammonia is used as fertilizers either as its salts, solutions or anhydrously. When applied to soil, it helps provide increased yields of crops such as maize and wheat.JOURNAL, Lassaletta, Luis, Billen, Gilles, Grizzetti, Bruna, Anglade, Juliette, Garnier, Josette, 50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland, Environmental Research Letters, 2014, 9, 10, 105011, 10.1088/1748-9326/9/10/105011, en, 1748-9326, 2014ERL.....9j5011L, 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia and worldwide 110 million tonnes are applied each year.NEWS,weblink Anhydrous ammonia fertilizer: abundant, important, hazardous, Washington Post, David Brown, 18 April 2013, 23 April 2013,

Precursor to nitrogenous compounds

Ammonia is directly or indirectly the precursor to most nitrogen-containing compounds. Virtually all synthetic nitrogen compounds are derived from ammonia. An important derivative is nitric acid. This key material is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at {{convert|700|–|850|°C}}, ≈9 atm. Nitric oxide is an intermediate in this conversion:BOOK, Holleman, A. F., Wiberg, E., Inorganic Chemistry, Academic Press, San Diego, 2001, 978-0-12-352651-9, {{block indent|NH3 + 2 O2 → HNO3 + H2O}}Nitric acid is used for the production of fertilizers, explosives, and many organonitrogen compounds.Ammonia is also used to make the following compounds: Ammonia can also be used to make compounds in reactions which are not specifically named. Examples of such compounds include: ammonium perchlorate, ammonium nitrate, formamide, dinitrogen tetroxide, alprazolam, ethanolamine, ethyl carbamate, hexamethylenetetramine, and ammonium bicarbonate.

As a cleaner

Household ammonia is a solution of NH3 in water, and is used as a general purpose cleaner for many surfaces. Because ammonia results in a relatively streak-free shine, one of its most common uses is to clean glass, porcelain and stainless steel. It is also frequently used for cleaning ovens and soaking items to loosen baked-on grime. Household ammonia ranges in concentration by weight from 5 to 10% ammonia.WEB,weblink The Facts About Ammonia,, en-us, 2018-04-06, United States manufacturers of cleaning products are required to provide the product's material safety data sheet which lists the concentration used.WEB,weblink OSHA Hazard Communication Standard: Safety Data Sheets, OSHA,


Solutions of ammonia ranging from 16% to 25% are used in the fermentation industry as a source of nitrogen for microorganisms and to adjust pH during fermentation.

Antimicrobial agent for food products

As early as in 1895, it was known that ammonia was "strongly antiseptic ... it requires 1.4 grams per litre to preserve beef tea."BOOK,weblink Disinfection and Disinfectants: An Introduction to the Study of, Samuel Rideal, Charles Griffin and Company, London, 1895, 109, In one study, anhydrous ammonia destroyed 99.999% of zoonotic bacteria in 3 types of animal feed, but not silage.JOURNAL, 10.1016/j.ijfoodmicro.2007.11.040, Ammonia disinfection of animal feeds — Laboratory study, Tajkarimi, Mehrdad, International Journal of Food Microbiology, 122, 1–2, 2008, 23–28, 18155794, Riemann, H. P., Hajmeer, M. N., Gomez, E. L., Razavilar, V., Cliver, D. O., etal, JOURNAL, Kim, JS, Lee, YY, Kim, TH, A review on alkaline pretreatment technology for bioconversion of lignocellulosic biomass., Bioresource Technology, January 2016, 199, 42–48, 10.1016/j.biortech.2015.08.085, 26341010, Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef."weblink" title="">Evaluation of Treatment Methods for Reducing Bacteria in Textured Beef", Jensen, Jean L et al., American Society of Agricultural and Biological Engineers Annual Meeting 2009Reference Document: Antimicrobial Interventions for Beef, Dawna Winkler and Kerri B. Harris, Center for Food Safety, Department of Animal Science, Texas A&M University, May 2009, page 12Lean finely textured beef (popularly known as "pink slime") in the beef industry is made from fatty beef trimmings (c. 50–70% fat) by removing the fat using heat and centrifugation, then treating it with ammonia to kill E. coli. The process was deemed effective and safe by the US Department of Agriculture based on a study that found that the treatment reduces E. coli to undetectable levels.NEWS,weblink The New York Times, The Burger That Shattered Her Life, Michael, Moss, 3 October 2009, There have been safety concerns about the process as well as consumer complaints about the taste and smell of beef treated at optimal levels of ammonia.NEWS,weblink The New York Times, Safety of Beef Processing Method Is Questioned, Michael, Moss, 31 December 2009, The level of ammonia in any final product has not come close to toxic levels to humans.

Minor and emerging uses

Refrigeration – R717

Because of ammonia's vaporization properties, it is a useful refrigerant. It was commonly used before the popularisation of chlorofluorocarbons (Freons). Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high energy efficiency and low cost. It suffers from the disadvantage of toxicity, which restricts its domestic and small-scale use. Along with its use in modern vapor-compression refrigeration it is used in a mixture along with hydrogen and water in absorption refrigerators. The Kalina cycle, which is of growing importance to geothermal power plants, depends on the wide boiling range of the ammonia–water mixture. Ammonia coolant is also used in the S1 radiator aboard the International Space Station in two loops which are used to regulate the internal temperature and enable temperature dependent experiments.NEWS,weblink Cooling System Keeps Space Station Safe, Productive, Wright, Jerry, 2015-04-13, NASA, 2017-07-01, en, NEWS,weblink International Space Station's Cooling System: How It Works (Infographic),, 2017-07-01, The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are extremely potent and stable greenhouse gases.NEWS, Reducing Hydrofluorocarbon (HFC) Use and Emissions in the Federal Sector through SNAP,weblink 2018-12-02, The contribution to the greenhouse effect of CFCs and HFCs in current use, if vented, would match that of all CO2 in the atmosphere.{{Citation needed|date=January 2019}}

For remediation of gaseous emissions

Ammonia is used to scrub SO2 from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertilizer. Ammonia neutralizes the nitrogen oxide (NOx) pollutants emitted by diesel engines. This technology, called SCR (selective catalytic reduction), relies on a vanadia-based catalyst.WEB, 7 July 2009,weblink Diesel: Greener Than You Think, Ammonia may be used to mitigate gaseous spills of phosgene.WEB, International Programme on Chemical Safety, Phosgene: Health and Safety Guide, 1998,weblink

As a fuel

File:AmmoniacalGasEngineStreetcarARWaud.jpeg|thumb|Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred WaudAlfred WaudFile:x-15.jpg|thumb|The X-15 aircraft used ammonia as one component fuel of its rocket engineengineThe raw energy density of liquid ammonia is 11.5 MJ/L,JOURNAL, Lan, Rong, Tao, Shanwen, 28 August 2014, Ammonia as a suitable fuel for fuel cells, Frontiers in Energy Research, 2, 35, 10.3389/fenrg.2014.00035, which is about a third that of diesel. There is the opportunity to convert ammonia back to hydrogen, where it can be used to power hydrogen fuel cells or directly within high-temperature fuel cells.JOURNAL, Giddey, S., Badwal, S. P. S., Munnings, C., Dolan, M., Ammonia as a Renewable Energy Transportation Media, ACS Sustainable Chemistry & Engineering, 5, 11, 10231–10239, 10 October 2017, 10.1021/acssuschemeng.7b02219, The conversion of ammonia to hydrogen via the sodium-amide process,JOURNAL, David, William I. F., Makepeace, Joshua W., Callear, Samantha K., Hunter, Hazel M. A., Taylor, James D., Wood, Thomas J., Jones, Martin O., 2014-09-24, Hydrogen Production from Ammonia Using Sodium Amide, Journal of the American Chemical Society, 136, 38, 13082–13085, 10.1021/ja5042836, 0002-7863, 24972299, either for combustion or as fuel for a proton exchange membrane fuel cell, is possible. Conversion to hydrogen would allow the storage of hydrogen at nearly 18 wt% compared to ≈5% for gaseous hydrogen under pressure.Ammonia engines or ammonia motors, using ammonia as a working fluid, have been proposed and occasionally used.WEB
, Douglas Self
, Douglas Self
,weblink Ammonia Motors, 1 October 2007, 28 November 2010
, The principle is similar to that used in a fireless locomotive, but with ammonia as the working fluid, instead of steam or compressed air. Ammonia engines were used experimentally in the 19th century by Goldsworthy Gurney in the UK and the St. Charles Avenue Streetcar line in New Orleans in the 1870s and 1880s,BOOK, The Streetcars of New Orleans, Louis C. Hennick, Elbridge Harper Charlton, 1965, Pelican Publishing, 9781455612598, 14–16, and during World War II ammonia was used to power buses in Belgium.Ammonia is sometimes proposed as a practical alternative to fossil fuel for internal combustion engines.NEWS,weblink Ammonia as a Transportation Fuel IV, 15–16 October 2007, Norm Olson – Iowa Energy Center, dead,weblink" title="">weblink 7 February 2012, dmy, WEB, Development of new combustion strategy for internal combustion engine fueled by pure ammonia, Lee, Dongeun, Min, Hyungeun, Park, Hyunho, Song, Han Ho,weblink Seoul National University, Department of Mechanical Engineering, 2017-11-01, 2019-01-29, WEB, Ammonia as fuel for internal combustion engines?, Brohi, Emtiaz Ali,weblink Chalmers University of Technology, 2014, 2019-01-29, Its high octane rating of 120WEB,weblink Ammonia,, 3 March 2016, and low flame temperatureWEB, Characteristics of an SI Engine Using Direct Ammonia Injection, Zacharakis-Jutz, George, Kong, Song-Charng,weblink Department of Mechanical Engineering, Iowa State University, 2013, 2019-01-29, allows the use of high compression ratios without a penalty of high NOx production. Since ammonia contains no carbon, its combustion cannot produce carbon dioxide, carbon monoxide, hydrocarbons, or soot.However ammonia cannot be easily used in existing Otto cycle engines because of its very narrow flammability range, and there are also other barriers to widespread automobile usage. In terms of raw ammonia supplies, plants would have to be built to increase production levels, requiring significant capital and energy sources. Although it is the second most produced chemical, the scale of ammonia production is a small fraction of world petroleum usage. It could be manufactured from renewable energy sources, as well as coal or nuclear power. The 60 MW Rjukan dam in Telemark, Norway produced ammonia for many years from 1913, providing fertilizer for much of Europe.Despite this, several tests have been done. In 1981, a Canadian company converted a 1981 Chevrolet Impala to operate using ammonia as fuel.{{YouTube|L0hBAz6MxC4|Ammonia Powered Car}}WEB,weblink Watch 'Ammonia Fuel', 7 July 2009, Greg Vezina, In 2007, a University of Michigan pickup powered by ammonia drove from Detroit to San Francisco as part of a demonstration, requiring only one fill-up in Wyoming.WEB,weblink Welcome to NH3 Car,, Compared to hydrogen as a fuel, ammonia is much more energy efficient, and could be produced, stored, and delivered at a much lower cost than hydrogen which must be kept compressed as a cryogenic liquid.WEB,weblink He's Creating a New Fuel Out of Thin Air — for 85 Cents per Gallon, Jared, Lindzon, OZY, 26 April 2019, Rocket engines have also been fueled by ammonia. The Reaction Motors XLR99 rocket engine that powered the {{nowrap|X-15}} hypersonic research aircraft used liquid ammonia. Although not as powerful as other fuels, it left no soot in the reusable rocket engine, and its density approximately matches the density of the oxidizer, liquid oxygen, which simplified the aircraft's design.

As a stimulant

File:Meth ammonia tank Otley iowa.JPG|thumb|Anti-meth sign on tank of anhydrous ammonia, Otley, IowaOtley, IowaAmmonia, as the vapor released by smelling salts, has found significant use as a respiratory stimulant. Ammonia is commonly used in the illegal manufacture of methamphetamine through a Birch reduction.WEB,weblink Illinois Attorney General | Basic Understanding Of Meth,, 21 May 2011,weblink" title="">weblink 10 September 2010, dead, dmy-all, The Birch method of making methamphetamine is dangerous because the alkali metal and liquid ammonia are both extremely reactive, and the temperature of liquid ammonia makes it susceptible to explosive boiling when reactants are added.BOOK,weblink Occupational, Industrial, and Environmental Toxicology, Greenberg, Michael I., 2003-01-01, Elsevier Health Sciences, 978-0323013406, en,


Liquid ammonia is used for treatment of cotton materials, giving properties like mercerisation, using alkalis. In particular, it is used for prewashing of wool.JOURNAL, WÅ‚ochowicz, A., Stelmasiak, E., Change in thermal properties of wool after treatment with liquid ammonia, Journal of Thermal Analysis and Calorimetry, 26, 1, 1983, 17, 10.1007/BF01914084,

Lifting gas

At standard temperature and pressure, ammonia is less dense than atmosphere and has approximately 45-48% of the lifting power of hydrogen or helium. Ammonia has sometimes been used to fill weather balloons as a lifting gas. Because of its relatively high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast (and returned to a gas to add lift and reduce ballast).


{{see also|Ammonia fuming}}Ammonia has been used to darken quartersawn white oak in Arts & Crafts and Mission-style furniture. Ammonia fumes react with the natural tannins in the wood and cause it to change colours.Fuming white oak.

Energy carrier

In early August 2018, scientists from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) announced the success of developing a process to release hydrogen from ammonia and harvest that at ultra-high purity as a fuel for cars. This uses a special membrane. Two demonstration fuel cell vehicles have the technology, a Hyundai Nexo and Toyota Mirai. 'Carbon-free fuel': Australian hydrogen car breakthrough could go global, Lexy Hamilton-Smith, ABC News Online, 2018-08-08

Safety precautions

File:Ammiakoprovod NS.jpg|thumb|The world's longest ammonia pipeline (roughly 2400 km long),minerals year book, vol. 3 running from the TogliattiAzot plant in Russia to Odessa in UkraineUkraineThe U.S. Occupational Safety and Health Administration (OSHA) has set a 15-minute exposure limit for gaseous ammonia of 35 ppm by volume in the environmental air and an 8-hour exposure limit of 25 ppm by volume.NEWS,weblink Toxic FAQ Sheet for Ammonia, Agency for Toxic Substances and Disease Registry (ATSDR), September 2004, The National Institute for Occupational Safety and Health (NIOSH) recently reduced the IDLH (Immediately Dangerous to Life and Health, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 to 300 based on recent more conservative interpretations of original research in 1943. Other organizations have varying exposure levels. U.S. Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): continuous exposure (60 days): 25 ppm / 1 hour: 400 ppm.Ammonia, IDLH Documentation Ammonia vapour has a sharp, irritating, pungent odour that acts as a warning of potentially dangerous exposure. The average odour threshold is 5 ppm, well below any danger or damage. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death. Although ammonia is regulated in the United States as a non-flammable gas, it still meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than 13,248 L (3,500 gallons).Is Anhydrous Ammonia covered under the Hazardous Materials Safety Permit Program? from the website of the United States Department of Transportation (DOT) Household products containing ammonia (e.g. Windex) should never be used in conjunction with products containing bleach, as the resulting chemical reaction produces highly toxic fumes.NEWS,weblink Why You Shouldn't Mix Bleach and Ammonia, ThoughtCo, 2017-07-01, Liquid ammonia is dangerous because it is hygroscopic and because it can freeze flesh. See {{section link|Gas carrier|Health effects of specific cargoes carried on gas carriers}} for more information.


The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase, and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine.BOOK, Berg, JM, Tymoczko, JL, Stryer, L, Biochemistry,weblink 5th, 2002, 23.4, Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as dangerous for the environment.Ammonia is a constituent of tobacco smoke.JOURNAL, Talhout, Reinskje, Schulz, Thomas, Florek, Ewa, Van Benthem, Jan, Wester, Piet, Opperhuizen, Antoon, Hazardous Compounds in Tobacco Smoke, International Journal of Environmental Research and Public Health, 8, 12, 2011, 613–628, 1660-4601, 10.3390/ijerph8020613, 21556207, 3084482,

Coking wastewater

Ammonia is present in coking wastewater streams, as a liquid by-product of the production of coke from coal.WEB, Cutting-Edge Solutions For Coking Wastewater Reuse To Meet The Standard Of Circulation Cooling Systems,weblink, 2016-01-16, In some cases, the ammonia is discharged to the marine environment where it acts as a pollutant. The Whyalla steelworks in South Australia is one example of a coke-producing facility which discharges ammonia into marine waters.BOOK, Vasudevan Rajaram, Subijoy Dutta, Krishna Parameswaran, Sustainable Mining Practices: A Global Perspective,weblink 30 June 2005, CRC Press, 978-1-4398-3423-7, 113–,


Ammonia toxicity is believed to be a cause of otherwise unexplained losses in fish hatcheries. Excess ammonia may accumulate and cause alteration of metabolism or increases in the body pH of the exposed organism. Tolerance varies among fish species.WEB,weblink Ammonia in Groundwater, Runoff, and Streams, 3 December 2014, The Water Centre, Oram, Brian, At lower concentrations, around 0.05 mg/L, un-ionised ammonia is harmful to fish species and can result in poor growth and feed conversion rates, reduced fecundity and fertility and increase stress and susceptibility to bacterial infections and diseases.BOOK, Managing ammonia in fish ponds, Hargreaves, J.A., Southern Regional Aquaculture Center, 2004, Tucker, C.S., Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate. At concentrations exceeding 2.0 mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death.JOURNAL,weblink The Management of Ammonia Levels in an Aquaculture Environment, Sergeant, Chris, 5 February 2014, Water/Wastewater, 3 December 2014, Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/l.During winter, when reduced feeds are administered to aquaculture stock, ammonia levels can be higher. Lower ambient temperatures reduce the rate of algal photosynthesis so less ammonia is removed by any algae present. Within an aquaculture environment, especially at large scale, there is no fast-acting remedy to elevated ammonia levels. Prevention rather than correction is recommended to reduce harm to farmed fish and in open water systems, the surrounding environment.

Storage information

Similar to propane, anhydrous ammonia boils below room temperature when at atmospheric pressure. A storage vessel capable of {{convert|250|psi|MPa|abbr=on|lk=on}} is suitable to contain the liquid.Electronic Code of Federal Regulations: {{webarchive|url= |date=4 November 2011 }}. Retrieved on 22 December 2011. Ammonium compounds should never be allowed to come in contact with bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.

Household use

Solutions of ammonia (5–10% by weight) are used as household cleaners, particularly for glass. These solutions are irritating to the eyes and mucous membranes (respiratory and digestive tracts), and to a lesser extent the skin. Caution should be used that the chemical is never mixed into any liquid containing bleach, as a toxic gas may result. Mixing with chlorine-containing products or strong oxidants, such as household bleach, can lead to hazardous compounds such as chloramines.BOOK, Rizk-Ouaini, Rosette, Ferriol, Michel, Gazet, Josette, Saugier-Cohen Adad, Marie Therese, Oxidation reaction of ammonia with sodium hypochlorite. Production and degradation reactions of chloramines, Bulletin de la Societe Chimique de France, 4, 512, 2006, 10.1002/14356007.a02_143.pub2, 978-3527306732,

Laboratory use of ammonia solutions

(File:Hydrochloric acid ammonia.jpg|thumb|Hydrochloric acid sample releasing HCl fumes, which are reacting with ammonia fumes to produce a white smoke of ammonium chloride.)The hazards of ammonia solutions depend on the concentration: "dilute" ammonia solutions are usually 5–10% by weight (25% by weight. A 25% (by weight) solution has a density of 0.907 g/cm3, and a solution that has a lower density will be more concentrated. The European Union classification of ammonia solutions is given in the table.{| class="wikitable"
  • Corrosive (C)
  • Dangerous forthe environment (N){edih}| {{R34}}, {{R50}}
{{block indent|S-Phrases: {{S1/2}}, {{S16}}, {{S36/37/39}}, {{S45}}, {{S61}}.}}The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract, and these solutions should only be handled in a fume hood. Saturated ("0.880" – see #Properties) solutions can develop a significant pressure inside a closed bottle in warm weather, and the bottle should be opened with care; this is not usually a problem for 25% ("0.900") solutions.Ammonia solutions should not be mixed with halogens, as toxic and/or explosive products are formed. Prolonged contact of ammonia solutions with silver, mercury or iodide salts can also lead to explosive products: such mixtures are often formed in qualitative inorganic analysis, and should be lightly acidified but not concentrated (Anhydrous ammonia is classified as toxic (T) and dangerous for the environment (N). The gas is flammable (autoignition temperature: 651 Â°C) and can form explosive mixtures with air (16–25%). The permissible exposure limit (PEL) in the United States is 50 ppm (35 mg/m3), while the IDLH concentration is estimated at 300 ppm. Repeated exposure to ammonia lowers the sensitivity to the smell of the gas: normally the odour is detectable at concentrations of less than 50 ppm, but desensitised individuals may not detect it even at concentrations of 100 ppm. Anhydrous ammonia corrodes copper- and zinc-containing alloys, and so brass fittings should not be used for handling the gas. Liquid ammonia can also attack rubber and certain plastics.Ammonia reacts violently with the halogens. Nitrogen triiodide, a primary high explosive, is formed when ammonia comes in contact with iodine. Ammonia causes the explosive polymerisation of ethylene oxide. It also forms explosive fulminating compounds with compounds of gold, silver, mercury, germanium or tellurium, and with stibine. Violent reactions have also been reported with acetaldehyde, hypochlorite solutions, potassium ferricyanide and peroxides.

Synthesis and production

{{about|section=true|industrial synthesis|synthesis in certain organisms|#Biosynthesis}}{{See also|Ammonia production}}(File:Production of ammonia.svg|thumb|upright=1.35|right|Production trend of ammonia between 1947 and 2007)Ammonia is one of the most produced inorganic chemicals, with global production reported at 176 million tonnes in 2014. China accounted for 32.6% of that, followed by Russia at 8.1%, India at 7.6%, and the United States at 6.4%.Before the start of World War I, most ammonia was obtained by the dry distillationNEWS, 7 July 2009,weblink Nobel Prize in Chemistry (1918) – Haber-Bosch process, of nitrogenous vegetable and animal waste products, including camel dung, where it was distilled by the reduction of nitrous acid and nitrites with hydrogen; in addition, it was produced by the distillation of coal, and also by the decomposition of ammonium salts by alkaline hydroxidesNEWS, 7 July 2009, Chemistry of the Group 2 Elements – Be, Mg, Ca, Sr, Ba, Ra,weblink, such as quicklime:See {{harv|Chisholm|1911}}, page 861.{{block indent|2 NH4Cl + 2 CaO → CaCl2 + Ca(OH)2 + 2 NH3(g)}}For small scale laboratory synthesis, one can heat urea and calcium hydroxide:{{block indent|(NH2)2CO + Ca(OH)2 → CaCO3 + 2 NH3}}

Haber-Bosch process

Mass production of ammonia mostly uses the Haber–Bosch process, reacting hydrogen (H2) and nitrogen (N2) at a moderately-elevated temperature (450 Â°C) and high pressure ({{convert|100|atm}}):Atkins, P.W.; Overton, T.L.; Rourke, J.P.; Weller, M.T. and Armstrong, F.A. (2010) Shriver and Atkins Inorganic Chemistry. 5th Edi. W. H. Freeman and Company, New York. p. 383. {{ISBN|978-1-42-921820-7}}{{block indent|3 H2 + N2 → 2 NH3(g)}}This reaction is both exothermic and results in decreased entropy, meaning that the reaction is favoured at lower temperaturesSee {{harv|Clark|2013}}: "The forward reaction (the production of ammonia) is exothermic. According to Le Chatelier's Principle, this will be favoured if you lower the temperature. The system will respond by moving the position of equilibrium to counteract this – in other words by producing more heat. In order to get as much ammonia as possible in the equilibrium mixture, you need as low a temperature as possible". and higher pressures.See {{harv|Clark|2013}}: "Notice that there are 4 molecules on the left-hand side of the equation, but only 2 on the right. According to Le Chatelier's Principle, if you increase the pressure the system will respond by favouring the reaction which produces fewer molecules. That will cause the pressure to fall again. In order to get as much ammonia as possible in the equilibrium mixture, you need as high a pressure as possible. 200 atmospheres is a high pressure, but not amazingly high". This makes it difficult and expensive to achieve, as lower temperatures result in slower reaction kinetics (hence a slower reaction rate)See {{harv|Clark|2013}}: "However, 400–450°C isn't a low temperature! Rate considerations: The lower the temperature you use, the slower the reaction becomes. A manufacturer is trying to produce as much ammonia as possible per day. It makes no sense to try to achieve an equilibrium mixture which contains a very high proportion of ammonia if it takes several years for the reaction to reach that equilibrium". and high pressure requires high-strength pressure vesselsSee {{harv|Clark|2013}}: "Rate considerations: Increasing the pressure brings the molecules closer together. In this particular instance, it will increase their chances of hitting and sticking to the surface of the catalyst where they can react. The higher the pressure the better in terms of the rate of a gas reaction. Economic considerations: Very high pressures are very expensive to produce on two counts. You have to build extremely strong pipes and containment vessels to withstand the very high pressure. That increases your capital costs when the plant is built". that aren't weakened by hydrogen embrittlement. In addition, diatomic nitrogen is bound together by an exceptionally strong triple bond, which makes it rather inert.WEB, Chemistry of Nitrogen, 2019-06-05,, Compounds,weblink 2019-07-07, Both the yield and efficiency of the Haber-Bosch Process are low, meaning that ammonia produced must be continuously separated and extracted for the reaction to proceed at an appreciable pace.See {{harv|Clark|2013}}: "At each pass of the gases through the reactor, only about 15% of the nitrogen and hydrogen converts to ammonia. (This figure also varies from plant to plant.) By continual recycling of the unreacted nitrogen and hydrogen, the overall conversion is about 98%". Combined with the energy needed to produce hydrogen{{refn|group=note|Hydrogen required for ammonia synthesis is most often produced through gasification of carbon-containing material, mostly natural gas, but other potential carbon sources include coal, petroleum, peat, biomass, or waste. As of 2012, the global production of ammonia produced from natural gas using the steam reforming process was 72 percent.NEWS,weblink Ammonia, 2013-04-30, Industrial Efficiency Technology & Measures, 2018-04-06, en, Hydrogen can also be produced from water and electricity using electrolysis: at one time, most of Europe's ammonia was produced from the Hydro plant at Vemork. Other possibilities include biological hydrogen production or photolysis, but at present, steam reforming of natural gas is the most economical means of mass-producing hydrogen.}} and purified atmospheric nitrogen, ammonia production is a very energy-intensive process, consuming 1 to 2% of global energy, 3% of global carbon emissions,WEB,weblink Electrochemically-produced ammonia could revolutionize food production, Lehigh University, 2018-07-09, en, 2018-12-15, Ammonia manufacturing consumes 1 to 2% of total global energy and is responsible for approximately 3% of global carbon dioxide emissions., Lehigh University, and 3 to 5% of natural gas consumption.JOURNAL,weblink A physical catalyst for the electrolysis of nitrogen to ammonia, Science Advances, 4, 4, e1700336, Song, Yang, Hensley, Dale, Bonnesen, Peter, Liang, Liango, Huang, Jingsong, Baddorf, Arthur, Tschaplinski, Timothy, Engle, Nancy, Wu, Zili, Cullen, David, Meyer, Harry III, Sumpter, Bobby, Rondinone, Adam, 2018-05-02, Oak Ridge National Laboratory, en, 10.1126/sciadv.1700336, 29719860, 5922794, 2018-12-15, Ammonia synthesis consumes 3 to 5% of the world’s natural gas, making it a significant contributor to greenhouse gas emissions., 2018SciA....4E0336S,

Liquid ammonia as a solvent

{{See also|Inorganic nonaqueous solvent}}Liquid ammonia is the best-known and most widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of NH3 with those of water shows NH3 has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity; this is due at least in part to the weaker hydrogen bonding in NH3 and because such bonding cannot form cross-linked networks, since each NH3 molecule has only one lone pair of electrons compared with two for each H2O molecule. The ionic self-dissociation constant of liquid NH3 at −50 Â°C is about 10−33 mol2·l−2.(File:Ammonia Train.jpg|thumb|A train carrying Anhydrous Ammonia.)">

Solubility of salts{| class"wikitable"

!! Solubility (g of salt per 100 g liquid NH3)| Ammonium acetate| 253.2| Ammonium nitrate| 389.6| Lithium nitrate| 243.7| Sodium nitrate| 97.6| Potassium nitrate| 10.4| Sodium fluoride| 0.35| Sodium chloride| 157.0| Sodium bromide| 138.0| Sodium iodide| 161.9| Sodium thiocyanate| 205.5Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides, thiocyanates, metal cyclopentadienyl complexes and metal bis(trimethylsilyl)amides.JOURNAL, Neufeld, R., Michel, R., Herbst-Irmer, R., Schöne, R., Stalke, D., Chem. Eur. J., 2016, 22, 35, 12340–12346, Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M = Li, Na, K, Rb and Cs) with Ammonia, 10.1002/chem.201600833, 27457218, Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide. A saturated solution of ammonium nitrate (Divers' solution, named after Edward Divers) contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at {{convert|25|C|0|abbr=on}}.

Solutions of metals

{{See also|Solvated electron}}Liquid ammonia will dissolve the alkali metals and other electropositive metals such as magnesium, calcium, strontium, barium, europium and ytterbium. At low concentrations (

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