View source for Ammonia

{{Short description|Chemical compound}}
{{Redirect-multi|3|NH3|Ammoniac|R-717|{{chem2|NH4+}}|Ammonium|the gum ammoniac|Ammoniacum|the route in South Africa|R717 (South Africa)|other uses|NH 3 (disambiguation)|and|Ammonia (disambiguation)}}
{{Use dmy dates|date=July 2020|cs1-dates=l}}
{{Use British English|date=May 2012}}<!-- THIS ARTICLE WAS STARTED IN BRITISH SPELLING. PLEASE KEEP PER WP:ENGVAR. -->
{{Chembox
|Watchedfields = changed
|verifiedrevid = 4453674488
|ImageFileL2 = Ammonia-3D-balls-A.png
|ImageNameL2 = Ball-and-stick model of the ammonia molecule
|ImageFileR2 = Ammonia-3D-vdW.png
|ImageNameR2 = Space-filling model of the ammonia molecule
|Name = Ammonia
|ImageFile1 = Ammonia-2D.svg
|ImageSize1 = 150px
|ImageName1 = Stereo structural formula of the ammonia molecule
| ImageClass1    = skin-invert-image
|IUPACName = Ammonia<ref>{{Cite web|url=https://iupac.org/wp-content/uploads/2016/07/Red_Book_2005.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://iupac.org/wp-content/uploads/2016/07/Red_Book_2005.pdf |archive-date=2022-10-09 |url-status=live|title=Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005}}</ref>
|SystematicName = Azane
|OtherNames = {{ubli|Hydrogen nitride|R-717|R717 (refrigerant)|Amidogen|Hydrogen amine|Nitrogen hydride}}
|Section1 = {{Chembox Identifiers
|InChI = 1/H3N/h1H3
|InChIKey = QGZKDVFQNNGYKY-UHFFFAOYAF
|CASNo = 7664-41-7
|CASNo_Ref = {{cascite|correct|CAS}}
|PubChem = 222
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 1160819
|ChemSpiderID = 217
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|UNII = 5138Q19F1X
|UNII_Ref = {{fdacite|correct|FDA}}
|EINECS = 231-635-3
|UNNumber = 1005
|KEGG = D02916
|KEGG_Ref = {{keggcite|correct|kegg}}
|MeSHName = Ammonia
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 16134
|RTECS = BO0875000
|SMILES = N
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/H3N/h1H3
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = QGZKDVFQNNGYKY-UHFFFAOYSA-N
|Beilstein = 3587154
|Gmelin = 79
|3DMet = B00004}}
|Section2 = {{Chembox Properties
|Formula = {{Chem2|NH3}}
|N=1|H=3
|Appearance = Colourless gas
|Odour = Strong pungent odour
|Density = {{ubli|0.86&nbsp;kg/m<sup>3</sup> (1.013 bar at boiling point)|0.769&nbsp;kg/m<sup>3</sup> (STP)<ref>{{cite web|url=https://www.engineeringtoolbox.com/gas-density-d_158.html|title=Gases – Densities|website=The Engineering Toolbox|access-date=3 March 2016}}</ref>|0.73&nbsp;kg/m<sup>3</sup> (1.013 bar at 15&nbsp;°C)|0.6819&nbsp;g/cm<sup>3</sup> at −33.3&nbsp;°C (liquid)<ref>{{cite book|chapter-url=https://books.google.com/books?id=qPGzhL3Y50YC&pg=PA132|page=132|title=Systematic Inorganic Chemistry|last=Yost |first=Don M.|chapter=Ammonia and Liquid Ammonia Solutions|publisher=Read Books|year=2007|isbn=978-1-4067-7302-6}}</ref> See also [[Ammonia (data page)]]|0.817&nbsp;g/cm<sup>3</sup> at −80&nbsp;°C (transparent solid)<ref>{{cite journal|doi=10.1080/00337577508240819|title=On crystalline character of transparent solid ammonia|year=1975|last=Blum |first=Alexander|journal=Radiation Effects and Defects in Solids|volume=24|issue=4|page=277|bibcode=1975RadEf..24..277B }}</ref>}}
|MeltingPtC = −77.73
|MeltingPt_notes = ([[Triple point]] at 6.060&nbsp;kPa, 195.4&nbsp;K)<!-- the solid–liquid transition line is essentially vertical, meaning the melting point is the same from ~0.05 to 12+ atm -->
|BoilingPtC = −33.34<!-- Critical point 11.300 MPa, 405.5&nbsp;K see [[Ammonia (data page)]] -->
|CriticalTP = {{convert|132.4|C|K}}, {{convert|111.3|atm|kPa|abbr=on}}
|Solubility = {{ubli|530g/l(20&nbsp;°C)|320g/l(25&nbsp;°C) <ref>{{cite web |title=Ammonia|publisher=The American Chemical Society|access-date=20 March 2024|date=8 February 2021 |url=https://www.acs.org/molecule-of-the-week/archive/a/ammonia.html}}</ref>}}
|SolubleOther = soluble in [[chloroform]], [[diethyl ether|ether]], [[ethanol]], [[methanol]]
|pKa = 32.5 (−33&nbsp;°C),<ref>{{cite book |last=Perrin |first=D. D. |title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution |edition=2nd |publisher=Pergamon Press |location=Oxford |year=1982}}</ref> 9.24 (of ammonium)
|pKb = 4.75
|ConjugateAcid = [[Ammonium]]
|ConjugateBase = [[Azanide|Amide]]
|RefractIndex = 1.3327
|Viscosity = {{ubli|10.07&nbsp;µPa·s (25&nbsp;°C)<ref>{{cite journal|last1=Iwasaki|first1=Hiroji|last2=Takahashi|first2=Mitsuo|title=Studies on the transport properties of fluids at high pressure|journal=The Review of Physical Chemistry of Japan|volume=38|issue=1|year=1968}}</ref>|0.276&nbsp;mPa·s (−40&nbsp;°C)}}
|VaporPressure = 857.3&nbsp;kPa
|MagSus = {{val|-18.0|e=-6|u=cm3/mol}}
}}
|Section3 = {{Chembox Structure
|MolShape = [[Trigonal pyramid]]
|Dipole = 1.42&nbsp;[[Debye|D]]
|PointGroup = C<sub>3v</sub>
}}
|Section4 = {{Chembox Thermochemistry
|DeltaHf = −46&nbsp;kJ/mol<ref name="Zumdahl-2009">{{cite book| last = Zumdahl |first=Steven S.|title =Chemical Principles |edition=6th |publisher = Houghton Mifflin | year = 2009| isbn = 978-0-618-94690-7|page=A22}}</ref>
|Entropy = 193&nbsp;J/(mol·K)<ref name="Zumdahl-2009"/>
}}
| Section5 = {{Chembox Hazards
|GHSPictograms = {{GHS05}} {{GHS06}} {{GHS09}}
|GHSSignalWord = Danger
|HPhrases = {{H-phrases| H314 | H331 | H410}}
|PPhrases = {{P-phrases|P260 | P273 | P280 | P303 + P361 + P353 | P304 + P340 + P311 | P305 + P351 + P338 + P310}}
|GHS_ref = <ref name="SigmaAldrich">{{Sigma-Aldrich|id=294993|name=Ammonia|access-date=27 December 2021}}</ref>
|ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0414.htm ICSC 0414] ([[anhydrous]])
|NFPA-H = 3
|NFPA-F = 1
|NFPA-R = 0
|NFPA-S = COR
|FlashPtC =
|AutoignitionPtC = 651
|ExploLimits = 15.0–33.6%
|NIOSH_ref=<ref name=NIOSH>{{PGCH|0028}}</ref>
|PEL = 50&nbsp;ppm (25&nbsp;ppm [[ACGIH]]-TLV; 35&nbsp;ppm [[STEL]])
|LD50 = 350&nbsp;mg/kg (rat, oral)<ref>{{cite web|url=https://rsc.aux.eng.ufl.edu/_files/msds/153.pdf |title=Ammonia, Anhydrous Safety Data Sheet |website=University of Florida |access-date=April 19, 2024}}</ref>
|REL = TWA 25&nbsp;ppm (18&nbsp;mg/m<sup>3</sup>) ST 35&nbsp;ppm (27&nbsp;mg/m<sup>3</sup>)
|IDLH = 300&nbsp;ppm
|LC50 = {{ubl|40,300&nbsp;ppm (rat, 10&nbsp;min)|28,595&nbsp;ppm (rat, 20&nbsp;min)|20,300&nbsp;ppm (rat, 40&nbsp;min)|11,590&nbsp;ppm (rat, 1&nbsp;hr)|7338&nbsp;ppm (rat, 1&nbsp;hr)|4837&nbsp;ppm (mouse, 1&nbsp;hr)|9859&nbsp;ppm (rabbit, 1&nbsp;hr)|9859&nbsp;ppm (cat, 1&nbsp;hr)|2000&nbsp;ppm (rat, 4&nbsp;hr)|4230&nbsp;ppm (mouse, 1&nbsp;hr)<ref name=IDLH>{{IDLH|7664417|Ammonia}}</ref>}}
| LCLo = {{ubli|5000&nbsp;ppm (mammal, 5&nbsp;min)|5000&nbsp;ppm (human, 5&nbsp;min)<ref name=IDLH/>}}
}}
|Section6 = {{Chembox Related
|OtherFunction = {{ubli|[[Hydrazine]]|[[Hydrazoic acid]]}}
|OtherFunction_label = nitrogen hydrides
|OtherCompounds = {{ubli|[[Ammonium hydroxide]]|[[Phosphine]]|[[Arsine]]|[[Stibine]]|[[Bismuthine]]}}
}}
}}

'''Ammonia''' is an [[inorganic]] [[chemical compound]] of [[nitrogen]] and [[hydrogen]] with the [[chemical formula|formula]] {{Chem2|NH3|auto=1}}. A [[Binary compounds of hydrogen|stable binary hydride]] and the simplest [[pnictogen hydride]], ammonia is a colourless [[gas]] with a distinctive pungent smell. Biologically, it is a common [[nitrogenous waste]], and it contributes significantly to the [[nutrition]]al needs of terrestrial organisms by serving as a precursor to [[fertiliser]]s.<ref>{{cite web |first1=Hannah |last1=Ritchie |author-link=Hannah Ritchie |title=How many people does synthetic fertilizer feed? |url=https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed |website=Our World in Data |date=7 November 2017 |access-date=4 September 2021}}</ref> Around 70% of ammonia produced industrially is used to make fertilisers<ref>{{cite web | url=https://www.iea.org/reports/ammonia-technology-roadmap | title=Ammonia Technology Roadmap – Analysis |publisher=IEA | date=11 October 2021 }}</ref> in various forms and composition, such as [[urea]] and [[diammonium phosphate]]. Ammonia in pure form is also applied directly into the soil.

Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals.

Ammonia occurs in nature and has been detected in the interstellar medium. In many countries, it is classified as an [[List of extremely hazardous substances|extremely hazardous substance]].<ref name="Gov">{{Cite web | publisher = [[Government Printing Office]] |location=United States | title = 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities |
url = https://www.ecfr.gov/current/title-40/chapter-I/subchapter-J/part-355#Appendix-A-to-Part-355 }}
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{{CodeFedReg|40|355|prefix=App|3=A}}
-->
</ref>

Ammonia is produced biologically in a process called [[nitrogen fixation]], but even more is generated industrially by the [[Haber process]]. The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235&nbsp;million tonnes.<ref>{{cite web | url=https://www.statista.com/statistics/1065865/ammonia-production-capacity-globally/ | title=Global ammonia annual production capacity |website=Statistia}}</ref><ref>{{cite web | url=https://www.forbes.com/sites/mitsubishiheavyindustries/2021/10/29/scaling-ammonia-production-for-the-worlds-food-supply/ | title=Mitsubishi Heavy Industries BrandVoice: Scaling Ammonia Production for the World's Food Supply |date=29 October 2021 | website=[[Forbes]] }}</ref> Industrial ammonia is transported by road in [[Tank truck|tankers]], by rail in [[Tank car|tank wagons]], by sea in [[gas carrier]]s, or in [[Bottled gas|cylinders]].<ref>{{cite book |first1=R. Norris |last1=Shreve |author1-link=R. Norris Shreve |author2-link=Joseph Brink|first2=Joseph |last2=Brink |title=Chemical Process Industries |date=1977 |isbn=978-0-07-057145-7 |page=276 |publisher=McGraw-Hill |edition=4th}}</ref>

Ammonia boils at {{convert|−33.34|°C|°F|3}} at a pressure of one [[Standard atmosphere (unit)|atmosphere]], but the liquid can often be handled in the laboratory without external cooling. Household ammonia or [[ammonium hydroxide]] is a solution of ammonia in water.

== Etymology ==
[[Pliny the Elder|Pliny]], in Book XXXI of his [[Natural History (Pliny)|Natural History]], refers to a salt named ''[[Salammoniac|hammoniacum]]'', so called because of the proximity of its source to the Temple of [[Amun|Jupiter Amun]] ([[Greek language|Greek]] Ἄμμων ''Ammon'') in the Roman province of [[Crete and Cyrenaica|Cyrenaica]].<ref>{{Cite web|url=https://www.perseus.tufts.edu/hopper/text?doc=urn:cts:latinLit:phi0978.phi001.perseus-eng1:31.39|title=Pliny the Elder, The Natural History, BOOK XXXI. REMEDIES DERIVED FROM THE AQUATIC PRODUCTION, CHAP. 39. (7.)—THE VARIOUS KINDS OF SALT; THE METHODS OF PREPARING IT, AND THE REMEDIES DERIVED FROM IT. TWO HUNDRED AND FOUR OBSERVATIONS THERE UPON.|website=www.perseus.tufts.edu}}</ref> However, the description Pliny gives of the salt does not conform to the properties of [[ammonium chloride]]. According to [[Herbert Hoover]]'s commentary in his English translation of [[Georgius Agricola]]'s ''[[De re metallica]]'', it is likely to have been common sea salt.<ref>{{Cite book|title=Georgius Agricola De Re Metallica – Translated from the first Latin edition of 1556|last=Hoover|first=Herbert|publisher=Dover Publications|year=1950|isbn=978-0486600062|location=New York|page=560}}</ref> In any case, that salt ultimately gave ammonia and [[ammonium]] compounds their name.

== Natural occurrence (abiological)==
Traces of ammonia/ammonium are found in rainwater. [[Ammonium chloride]] ([[sal ammoniac]]), and [[ammonium sulfate]] are found in volcanic districts. Crystals of [[ammonium bicarbonate]] have been found in [[Patagonia]] [[guano]].{{sfn|Chisholm|1911|p=861}}

Ammonia is found throughout the [[Solar System]] on [[Mars]], [[Jupiter]], [[Saturn]], [[Uranus]], [[Neptune]], and [[Pluto]], among other places: on smaller, icy [[Minor planet|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|−100|C|F K}} 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.<ref>Shannon, Francis Patrick (1938) [http://digital.lib.lehigh.edu/eb/supp/3646/index.pdf Tables of the properties of aqua–ammonia solutions. Part 1 of The Thermodynamics of Absorption Refrigeration]. Lehigh University studies. Science and technology series</ref><ref>[http://www.purdue.edu/newsroom/releases/2015/Q4/an-ammonia-water-slurry-may-swirl-below-plutos-icy-surface.html An ammonia–water slurry may swirl below Pluto's icy surface]. Purdue University (9 November 2015)</ref> Substances containing ammonia, or those that are similar to it, are called ''ammoniacal''.<ref>{{Cite web |date=July 2023 |title=ammoniacal (adj.) |url=https://www.oed.com/dictionary/ammoniacal_adj |website=Oxford English Dictionary |doi=10.1093/OED/3565252514}}</ref>

== Properties ==
{{multiple image
 | align = left
 | width = 80
 | footer = Two visible states of NH<sub>3</sub>
 | image1 = Liquid ammonia.png
 | alt1 = Liquid ammonia
 | caption1 = Liquid NH<sub>3</sub>
 | image2 = Solid ammonia.png
 | alt2 = Solid ammonia
 | caption2 = Solid NH<sub>3</sub>
}}
Ammonia is a colourless [[gas]] with a characteristically [[pungency|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 bond]]ing between molecules. Gaseous ammonia turns to a colourless [[liquid]], which [[boiling point|boils]] at {{convert|-33.1|°C|°F|2}}, and [[melting point|freezes]] to colourless crystals{{sfn|Chisholm|1911|p=861}} at {{convert|-77.7|°C|°F|2}}. Little data is available at very high temperatures and pressures, but the [[Supercritical fluid|liquid-vapor critical point]] occurs at 405&nbsp;K and 11.35&nbsp;MPa.<ref>{{cite journal |last1=Pimputkar |first1=Siddha |last2=Nakamura |first2=Shuji |title=Decomposition of supercritical ammonia and modeling of supercritical ammonia–nitrogen–hydrogen solutions with applicability toward ammonothermal conditions |journal=The Journal of Supercritical Fluids |date=January 2016 |volume=107 |pages=17–30 |doi=10.1016/j.supflu.2015.07.032|doi-access=free }}</ref>

=== Solid ===
The crystal symmetry is cubic, [[Pearson symbol]] cP16, [[space group]] P2<sub>1</sub>3 No.198, lattice constant 0.5125&nbsp;[[Nanometre|nm]].<ref>{{cite journal|doi=10.1107/S0567739479001340 |title=The crystal structure of deuteroammonia between 2 and 180&nbsp;K by neutron powder profile refinement|year=1979|last1=Hewat|first1=A. W.|last2=Riekel|first2=C. |journal=Acta Crystallographica Section A|volume=35|issue=4|page=569|bibcode = 1979AcCrA..35..569H }}</ref>

=== Liquid ===
[[Liquid]] ammonia possesses strong [[ion]]ising powers reflecting its high [[Dielectric constant|''ε'']] of 22 at {{Convert|-35|C|F}}.<ref>{{Cite journal |last1=Billaud |first1=Gerard |last2=Demortier |first2=Antoine |date=December 1975 |title=Dielectric constant of liquid ammonia from -35 to + 50.deg. and its influence on the association between solvated electrons and cation |url=https://pubs.acs.org/doi/abs/10.1021/j100593a053 |journal=The Journal of Physical Chemistry |language=en |volume=79 |issue=26 |pages=3053–3055 |doi=10.1021/j100593a053 |issn=0022-3654}}</ref> Liquid ammonia has a very high [[Enthalpy of vaporization|standard enthalpy change of vapourization]] (23.5&nbsp;[[kJ/mol]];<ref>{{Nist|id=C7664417|name=Ammonia}}</ref> for comparison, [[Properties of water|water]]'s is 40.65&nbsp;kJ/mol, methane 8.19&nbsp;kJ/mol and [[phosphine]] 14.6&nbsp;kJ/mol) and can be transported in pressurized or refrigerated vessels; however, at [[standard temperature and pressure]] liquid anhydrous ammonia will vaporize.<ref>{{Cite web |last1=Jepsen |first1=S. Dee |last2=McGuire |first2=Kent |date=November 27, 2017 |title=Safe Handling of Anhydrous Ammonia |url=https://ohioline.osu.edu/factsheet/aex-594 |website=Ohio State University Extension}}</ref>

=== Solvent properties ===
Ammonia readily [[solubility|dissolves]] in water. In an aqueous solution, it can be expelled by boiling. The [[water|aqueous]] solution of ammonia is [[Base (chemistry)|basic]], and may be described as aqueous ammonia or [[ammonium hydroxide]].<ref>{{Cite web |date=January 12, 2017 |title=Medical Management Guidelines for Ammonia |url=https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=7&toxid=2 |website=Agency for Toxic Substances and Disease Registry}}</ref> The maximum concentration of ammonia in water (a [[saturated solution]]) has a [[specific gravity]] of 0.880 and is often known as '.880 ammonia'.<ref>{{Cite book |last=Hawkins |first=Nehemiah |url=https://books.google.com/books?id=Z14wAAAAMAAJ |title=Hawkins' Mechanical Dictionary: A Cyclopedia of Words, Terms, Phrases and Data Used in the Mechanic Arts, Trades and Sciences |date=1909 |publisher=T. Audel |pages=15 |language=en}}</ref>

{|class="wikitable mw-collapsible"
|+Thermal and physical properties of saturated liquid ammonia<ref name="Stalke, D.-2016" /><ref name="Combellas-2001" />
!Temperature<br>(°C)
!Density<br>(kg/m<sup>3</sup>)
!Specific heat<br>(kJ/(kg·K))
!Kinematic<br>viscosity<br>(m<sup>2</sup>/s)
!Thermal<br>conductivity<br>(W/(m·K))
!Thermal<br>diffusivity<br>(m<sup>2</sup>/s)
!Prandtl<br>Number
!Bulk modulus<br>(K<sup>−1</sup>)
|-
| −50
|703.69
|4.463
|4.35×10<sup>−7</sup>
|0.547
|1.74×10<sup>−7</sup>
|2.6
|
|-
| −40
|691.68
|4.467
|4.06×10<sup>−7</sup>
|0.547
|1.78×10<sup>−7</sup>
|2.28
|
|-
| −30
|679.34
|4.476
|3.87×10<sup>−7</sup>
|0.549
|1.80×10<sup>−7</sup>
|2.15
|
|-
| −20
|666.69
|4.509
|3.81×10<sup>−7</sup>
|0.547
|1.82×10<sup>−7</sup>
|2.09
|
|-
| −10
|653.55
|4.564
|3.78×10<sup>−7</sup>
|0.543
|1.83×10<sup>−7</sup>
|2.07
|
|-
|0
|640.1
|4.635
|3.73×10<sup>−7</sup>
|0.540
|1.82×10<sup>−7</sup>
|2.05
|
|-
|10
|626.16
|4.714
|3.68×10<sup>−7</sup>
|0.531
|1.80×10<sup>−7</sup>
|2.04
|
|-
|20
|611.75
|4.798
|3.59×10<sup>−7</sup>
|0.521
|1.78×10<sup>−7</sup>
|2.02
|2.45×10<sup>−3</sup>
|-
|30
|596.37
|4.89
|3.49×10<sup>−7</sup>
|0.507
|1.74×10<sup>−7</sup>
|2.01
|
|-
|40
|580.99
|4.999
|3.40×10<sup>−7</sup>
|0.493
|1.70×10<sup>−7</sup>
|2
|
|-
|50
|564.33
|5.116
|3.30×10<sup>−7</sup>
|0.476
|1.65×10<sup>−7</sup>
|1.99
|}

{|class="wikitable mw-collapsible"
|+Thermal and physical properties of ammonia ({{chem2|NH3}}) at atmospheric pressure<ref name="Stalke, D.-2016" /><ref name="Combellas-2001" />
!Temperature<br>(K)
!Temperature (°C)
!Density<br>(kg/m<sup>3</sup>)
!Specific heat<br>(kJ/(kg·K))
!Dynamic<br>viscosity<br>(kg/(m·s))
!Kinematic<br>viscosity<br>(m<sup>2</sup>/s)
!Thermal<br>conductivity<br>(W/(m·K))
!Thermal<br>diffusivity<br>(m<sup>2</sup>/s)
!Prandtl<br>Number
|-
|273
| -0.15
|0.7929
|2.177
|9.35×10<sup>−6</sup>
|1.18×10<sup>−5</sup>
|0.0220
|1.31×10<sup>−5</sup>
|0.90
|-
|323
|49.85
|0.6487
|2.177
|1.10×10<sup>−5</sup>
|1.70×10<sup>−5</sup>
|0.0270
|1.92×10<sup>−5</sup>
|0.88
|-
|373
|99.85
|0.559
|2.236
|1.29×10<sup>−5</sup>
|1.30×10<sup>−5</sup>
|0.0327
|2.62×10<sup>−5</sup>
|0.87
|-
|423
|149.85
|0.4934
|2.315
|1.47×10<sup>−5</sup>
|2.97×10<sup>−5</sup>
|0.0391
|3.43×10<sup>−5</sup>
|0.87
|-
|473
|199.85
|0.4405
|2.395
|1.65×10<sup>−5</sup>
|3.74×10<sup>−5</sup>
|0.0467
|4.42×10<sup>−5</sup>
|0.84
|-
|480
|206.85
|0.4273
|2.43
|1.67×10<sup>−5</sup>
|3.90×10<sup>−5</sup>
|0.0492
|4.74×10<sup>−5</sup>
|0.822
|-
|500
|226.85
|0.4101
|2.467
|1.73×10<sup>−5</sup>
|4.22×10<sup>−5</sup>
|0.0525
|5.19×10<sup>−5</sup>
|0.813
|-
|520
|246.85
|0.3942
|2.504
|1.80×10<sup>−5</sup>
|4.57×10<sup>−5</sup>
|0.0545
|5.52×10<sup>−5</sup>
|0.827
|-
|540
|266.85
|0.3795
|2.54
|1.87×10<sup>−5</sup>
|4.91×10<sup>−5</sup>
|0.0575
|5.97×10<sup>−5</sup>
|0.824
|-
|560
|286.85
|0.3708
|2.577
|1.93×10<sup>−5</sup>
|5.20×10<sup>−5</sup>
|0.0606
|6.34×10<sup>−5</sup>
|0.827
|-
|580
|306.85
|0.3533
|2.613
|2.00×10<sup>−5</sup>
|5.65×10<sup>−5</sup>
|0.0638
|6.91×10<sup>−5</sup>
|0.817
|}

Liquid ammonia is a 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 electron]]s. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in [[aqueous solution]]s. Comparison of the physical properties of {{chem2|NH3}} with those of water shows {{chem2|NH3}} has the lower melting point, boiling point, density, [[viscosity]], [[dielectric constant]] and [[electrical conductivity]]. These differences are attributed at least in part to the weaker hydrogen bonding in {{chem2|NH3}}. The ionic self-[[dissociation constant]] of liquid {{chem2|NH3}} at −50&nbsp;°C is about 10<sup>−33</sup>.
[[File:Ammonia Train.jpg|thumb|A train carrying anhydrous ammonia]]

{| class="wikitable"
|-
!
! Solubility (g of salt per 100&nbsp;g liquid {{chem2|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]]
| 205.5
|}

Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many [[nitrate]]s, [[nitrite]]s, [[cyanide]]s, [[thiocyanate]]s, [[Cyclopentadienyl complex|metal cyclopentadienyl complexes]] and [[metal bis(trimethylsilyl)amides]].<ref name="Stalke, D.-2016">{{cite journal|author1=Neufeld, R.|author2=Michel, R.|author3=Herbst-Irmer, R.|author4=Schöne, R.|author5=Stalke, D.|year=2016|title=Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M = Li, Na, K, Rb and Cs) with Ammonia|journal=[[Chem. Eur. J.]]|volume=22|issue=35|pages=12340–12346|doi=10.1002/chem.201600833|pmid=27457218}}</ref> 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&nbsp;mol solute per mole of ammonia and has a [[vapour pressure]] of less than 1&nbsp;bar even at {{convert|25|C|0|abbr=on}}.  However, few [[oxyanion]] salts with other cations dissolve.<ref>{{cite book|url=https://archive.org/details/cftri.2662nonaqueoussolven0000ludw/page/45/|page=45|title=Non-aqueous solvents|first1=Ludwig&nbsp;F.|last1=Audrieth|first2=Jacob|last2=Kleinberg|publisher=John Wiley & Sons|location=New York|year=1953|lccn=52-12057}}</ref>

Liquid ammonia will dissolve all of the [[alkali metal]]s and other [[electronegativity|electropositive]] metals such as [[calcium|Ca]],<ref>{{cite encyclopedia|year=2001|title=Calcium–Ammonia|encyclopedia=Encyclopedia of Reagents for Organic Synthesis|doi=10.1002/047084289X.rc003|isbn=978-0471936237|author=Edwin M. Kaiser}}</ref> [[strontium|Sr]], [[barium|Ba]], [[europium|Eu]] and [[ytterbium|Yb]] (also [[magnesium|Mg]] using an electrolytic process<ref name="Combellas-2001">{{cite journal|last1=Combellas|first1=C|last2=Kanoufi|first2=F|last3=Thiébault|first3=A|year=2001|title=Solutions of solvated electrons in liquid ammonia|journal=Journal of Electroanalytical Chemistry|volume=499|pages=144–151|doi=10.1016/S0022-0728(00)00504-0}}</ref>). At low concentrations (<0.06&nbsp;mol/L), deep blue solutions are formed: these contain metal cations and [[solvated electron]]s, free electrons that are surrounded by a cage of ammonia molecules.

These solutions are strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as [[Wiktionary:immiscible|immiscible]] phases.

==== Redox properties of liquid ammonia ====
{{See also|Redox}}
[[File:Liquid ammonia bottle.jpg|thumb|upright|Liquid ammonia bottle]]

{| class="wikitable" style="text-align:center"
!
! [[Standard electrode potential|''E''°]] (V, ammonia)
! [[Standard electrode potential|''E''°]] (V, water)
|-
| {{chem2|Li+ + e− ⇌ Li}}
| −2.24
| −3.04
|-
| {{chem2|K+ + e− ⇌ K}}
| −1.98
| −2.93
|-
| {{chem2|Na+ + e− ⇌ Na}}
| −1.85
| −2.71
|-
| {{chem2|Zn(2+) + 2 e− ⇌ Zn}}
| −0.53
| −0.76
|-
| {{chem2|2 [NH4]+ + 2 e− ⇌ H2 + 2 NH3}}
| 0.00
| —
|-
| {{chem2|Cu(2+) + 2 e− ⇌ Cu}}
| +0.43
| +0.34
|-
| {{chem2|Ag+ + e− ⇌ Ag}}
| +0.83
| +0.80
|}

The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, [[Standard electrode potential|''E''°]] ({{chem2|N2 + 6 [NH4]+ + 6 e− ⇌ 8 NH3}}), is only +0.04&nbsp;V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the [[Amide|metal amide]] and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions; although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if [[transition metal]] ions are present as possible catalysts.

=== Structure ===
[[File:NH3-Dipole-Moment.png|thumb|Molecular structure of ammonia and its three-dimensional shape. It has a net dipole moment of 1.484&nbsp;[[Debye|D]].]]
[[File:Ammonia-2D-dot-cross.svg|class=skin-invert-image|thumb|[[Dot and cross diagram|Dot and cross]] structure of ammonia]]

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°.<ref name="CRC-2013">{{cite book | editor= Haynes, William M. | year = 2013 | title = CRC Handbook of Chemistry and Physics | edition = 94th | publisher = [[CRC Press]] | isbn = 9781466571143|pages=9–26| title-link = CRC Handbook of Chemistry and Physics }}</ref> 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 [[tetrahedron|tetrahedrally]]. Three of these [[electron pair]]s are used as bond pairs, which leaves one [[lone pair]] of electrons. The lone pair repels more strongly than bond pairs; therefore, the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°.<ref name="CRC-2013"/> This shape gives the molecule a [[dipole]] moment and makes it [[Polar molecule|polar]]. The molecule's polarity, and especially its ability to form [[hydrogen bond]]s, makes ammonia highly miscible with water. The lone pair makes ammonia a [[Base (chemistry)|base]], a proton acceptor. Ammonia is moderately basic; a 1.0&nbsp;[[Molar concentration|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 ({{nowrap|1=pH = 7}}), 99.4% of the ammonia molecules are [[protonated]]. Temperature and [[salinity]] also affect the proportion of [[ammonium]] {{chem2|[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&nbsp;kJ/mol, and the [[resonance frequency]] is 23.79&nbsp;[[GHz]], corresponding to [[microwave]] radiation of a [[wavelength]] of 1.260&nbsp;cm. The absorption at this frequency was the first [[Microwave spectroscopy|microwave spectrum]] to be observed <ref name="Cleeton-1934">{{cite journal|doi=10.1103/PhysRev.45.234 |title=Electromagnetic Waves of {{convert|1.1|cm|0|abbr=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 }}</ref> and was used in the first [[maser]].

=== Amphotericity ===
One of the most characteristic properties of ammonia is its [[basicity]]. Ammonia is considered to be a weak base. It combines with [[acid]]s to form [[ammonium]] [[salt (chemistry)|salt]]s; thus, with [[hydrochloric acid]] it forms [[ammonium chloride]] (sal ammoniac); with [[nitric acid]], [[ammonium nitrate]], etc. Perfectly dry ammonia gas will not combine with perfectly dry [[hydrogen chloride]] gas; moisture is necessary to bring about the reaction.{{sfn|Chisholm|1911|p=862}}<ref>{{cite journal|title=Influence of moisture on chemical change|author=Baker, H. B. |year=1894|journal=J. Chem. Soc.|volume=65|pages= 611–624|doi=10.1039/CT8946500611|url=https://zenodo.org/record/1863586 }}</ref>

As a demonstration experiment under air with ambient moisture, opened bottles of concentrated ammonia and [[hydrochloric acid]] solutions produce a cloud of [[ammonium chloride]], which seems to appear 'out of nothing' as the salt [[aerosol]] forms where the two [[diffusion|diffusing]] clouds of reagents meet between the two bottles.
{{block indent| {{chem2|NH3 + HCl → [NH4]Cl}}}}

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]] ({{chem2|[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|protic substance]] and is capable of formation of [[amide]]s (which contain the {{chem2|NH2−}} ion). For example, [[lithium]] dissolves in [[liquid ammonia]] to give a blue solution ([[solvated electron]]) of [[lithium amide]]:
{{block indent| {{chem2|2 Li + 2 NH3 → 2 LiNH2 + H2}}}}

=== Self-dissociation ===
Like water, liquid ammonia undergoes [[molecular autoionisation]] to form its [[conjugate acid|acid and base conjugates]]:
{{block indent| {{chem2|2 NH3 ⇌ NH4+ + NH2-}}}}

Ammonia often functions as a [[weak base]], so it has some [[buffer solution|buffering]] ability. Shifts in pH will cause more or fewer [[ammonium]] cations ({{chem2|NH4+}}) and [[Azanide|amide anions]] ({{chem2|NH2-}}) to be present in [[Solution (chemistry)|solution]]. At standard pressure and temperature,
{{block indent|1= K = {{chem2|[NH4+] × [NH2-]}} = 10<sup>−30</sup>.}}

=== Combustion ===
[[File:86. Каталитичка оксидација на амонијак.ogg|thumb|right|Heated [[Chromium(III) oxide|Cr<sub>2</sub>O<sub>3</sub>]] catalyzes the combustion of a flask of ammonia.]]
Ammonia does not burn readily or sustain [[combustion]], except under narrow fuel-to-air mixtures of 15–28% ammonia by volume in air.<ref>{{cite web |title=Ammonia |url=https://pubchem.ncbi.nlm.nih.gov/source/hsdb/162#section=Flammable-Limits |website=PubChem}}</ref> When mixed with [[oxygen]], it burns with a pale yellowish-green flame. 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]] ({{chem2|NCl3}}) is also formed.

The [[combustion]] of ammonia to form nitrogen and water is [[exothermic]]:
{{block indent|1= {{chem2|4 NH3 + 3 O2 → 2 N2 + 6 H2O(g)}}, [[Standard enthalpy of reaction|Δ''H''°<sub>r</sub>]] = −1267.20&nbsp;kJ (or −316.8&nbsp;kJ/mol if expressed per mol of {{chem2|NH3}})}}

The [[standard enthalpy change of combustion]], Δ''H''°<sub>c</sub>, expressed per [[mole (unit)|mole]] of ammonia and with condensation of the water formed, is −382.81&nbsp;kJ/mol. Dinitrogen is the thermodynamic product of [[combustion]]: all [[nitrogen oxide]]s are unstable with respect to {{chem2|N2}} and {{chem2|O2}}, which is the principle behind the [[catalytic converter]]. Nitrogen oxides can be formed as [[chemical kinetics|kinetic products]] in the presence of appropriate [[catalysts]], a reaction of great industrial importance in the production of [[nitric acid]]:
{{block indent| {{chem2|4 NH3 + 5 O2 → 4 NO + 6 H2O}}}}

A subsequent reaction leads to {{chem2|NO2}}:
{{block indent| {{chem2|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|heat of vapourization]], and a narrow [[Flammability limit|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.<ref name="Kobayashi-2019">{{cite journal |last1=Kobayashi |first1=Hideaki |last2=Hayakawa |first2=Akihiro |last3=Somarathne |first3=K.D. Kunkuma A. |last4=Okafor |first4=Ekenechukwu C. |title=Science and technology of ammonia combustion |journal=Proceedings of the Combustion Institute |date=2019 |volume=37 |issue=1 |pages=109–133 |doi=10.1016/j.proci.2018.09.029 |doi-access=free |bibcode=2019PComI..37..109K }}</ref> The flammable range of ammonia in dry air is 15.15–27.35% and in 100% relative humidity air is 15.95–26.55%.<ref>{{cite book |last1=Khan |first1=A.S. |last2=Kelley |first2=R.D. |last3=Chapman |first3=K.S. |last4=Fenton |first4=D.L. |title=Flammability limits of ammonia–air mixtures |date=1995 |publisher=U.S. DOE Office of Scientific and Technical Information |location=U.S. |osti=215703 }}</ref>{{clarify|By mass, volume or mole fraction???|date=December 2022}} For studying the [[chemical kinetics|kinetics]] of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain.<ref>{{Cite journal|last1=Shrestha|first1=Krishna P.|last2=Seidel|first2=Lars |last3=Zeuch|first3=Thomas |last4=Mauss|first4=Fabian |date=2018-07-07|title=Detailed kinetic mechanism for the oxidation of ammonia including the formation and reduction of nitrogen oxides|journal=Energy & Fuels|volume=32|issue=10|pages=10202–10217 |doi=10.1021/acs.energyfuels.8b01056|s2cid=103854263|issn=0887-0624 |url=https://hal.archives-ouvertes.fr/hal-02629067/file/Shrestha_Ammonia_NOx_2018.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://hal.archives-ouvertes.fr/hal-02629067/file/Shrestha_Ammonia_NOx_2018.pdf |archive-date=2022-10-09 |url-status=live}}</ref>

=== Precursor to organonitrogen compounds ===
Ammonia is a direct or indirect precursor to most [[#Precursor to nitrogenous compounds|manufactured nitrogen-containing compounds]]. It is the precursor to nitric acid, which is the source for most N-substituted aromatic compounds.

[[Amine]]s can be formed by the reaction of ammonia with [[alkyl halide]]s or, more commonly, with [[alcohol (chemistry)|alcohol]]s:
{{block indent|{{chem2|CH3OH  +  NH3  ->  CH3NH2  +  H2O}}}}
Its ring-opening reaction with [[ethylene oxide]] give [[ethanolamine]], [[diethanolamine]], and [[triethanolamine]].

[[Amide]]s can be prepared by the reaction of ammonia with [[carboxylic acid]] and their derivatives. For example, ammonia reacts with [[formic acid]] (HCOOH) to yield [[formamide]] ({{chem2|HCONH2}}) when heated. [[Acyl chloride]]s are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the [[hydrogen chloride]] formed. [[Ester]]s and [[anhydride]]s also react with ammonia to form amides. Ammonium salts of carboxylic acids can be [[Dehydration reaction|dehydrated]] to amides by heating to 150–200&nbsp;°C as long as no thermally sensitive groups are present.

* [[Amino acid]]s, using [[Strecker amino-acid synthesis]]
* [[Acrylonitrile]], in the [[Sohio process]]
Other organonitrogen compounds include [[alprazolam]], [[ethanolamine]], [[ethyl carbamate]] and [[hexamethylenetetramine]].

=== Precursor to inorganic nitrogenous compounds ===
[[Nitric acid]] is generated via the [[Ostwald process]] by [[oxidation]] of ammonia with air over a [[platinum]] catalyst at {{convert|700|–|850|°C}}, ≈9&nbsp;atm. [[Nitric oxide]] and [[nitrogen dioxide]] are intermediate in this conversion:<ref>{{cite book|author1=Holleman, A. F. |author2=Wiberg, E. |title=Inorganic Chemistry|publisher=Academic Press|location= San Diego|year=2001|isbn=978-0-12-352651-9}}</ref>
{{block indent|{{chem2|NH3 + 2 O2 → HNO3 + H2O}}}}
Nitric acid is used for the production of [[fertiliser]]s, [[explosive]]s, and many organonitrogen compounds.

The hydrogen in ammonia is susceptible to replacement by a myriad substituents. 
Ammonia gas reacts with metallic [[sodium]] to give [[sodamide]], {{chem2|NaNH2}}.{{sfn|Chisholm|1911|p=862}}

With chlorine, [[monochloramine]] is formed.

Pentavalent ammonia is known as λ<sup>5</sup>-amine, [[nitrogen pentahydride]] decomposes spontaneously into trivalent ammonia (λ<sup>3</sup>-amine) and hydrogen gas at normal conditions. This substance was once investigated as a possible solid [[rocket fuel]] in 1966.<ref>{{cite news|url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0373800 |title=High pressure chemistry of hydrogenous fuels|author1=Sterrett, K. F.|author2=Caron, A. P.|publisher=Northrop Space Labs|year=1966|access-date=24 December 2009|archive-url=https://web.archive.org/web/20110823130932/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0373800 |archive-date=23 August 2011|url-status=dead}}</ref>

Ammonia is also used to make the following compounds:
* [[Hydrazine]], in the [[Olin Raschig process]] and the [[peroxide process]]
* [[Hydrogen cyanide]], in the [[BMA process]] and the [[Andrussow process]]
* [[Hydroxylamine]] and [[ammonium carbonate]], in the [[Raschig hydroxylamine process|Raschig process]]
* [[Urea]], in the [[Bosch–Meiser urea process]] and in [[Wöhler synthesis]]
* [[ammonium perchlorate]], [[ammonium nitrate]], and [[ammonium bicarbonate]]

[[File:Cisplatin-stereo.svg|class=skin-invert-image|thumb|[[Cisplatin]] ({{chem2|[Pt(NH3)2Cl2}}) is a widely used [[anticancer drug]].|upright=0.6]]
Ammonia is a [[ligand]] forming [[metal ammine complex]]es. For historical reasons, ammonia is named '''ammine''' in the nomenclature of [[coordination compound]]s. One notable ammine complex is [[cisplatin]] ({{chem2|Pt(NH3)2Cl2}}, a widely used anticancer drug. Ammine complexes of [[chromium]](III) formed the basis of [[Alfred Werner]]'s revolutionary theory on the structure of coordination compounds. Werner noted only two [[isomer]]s (''fac''- and ''mer''-) of the complex {{chem2|[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]].

Ammonia forms 1:1 [[adduct]]s with a variety of [[Lewis acid]]s such as [[Iodine|{{chem2|I2}}]], [[phenol]], and [[Trimethyl aluminium|{{chem2|Al(CH3)3}}]]. Ammonia is a [[hard base]] (HSAB theory) and its [[ECW model|E & C parameters]] are E<sub>B</sub> = 2.31 and C<sub>B</sub> = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by [[ECW model|C-B plots]].

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

=== Ammonia in solution ===
{{Main|Ammonia 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 hydroxide|sodium]] (NaOH) or [[potassium hydroxide]] (KOH), the ammonia evolved being absorbed in a known volume of standard [[sulfuric acid]] and the excess of acid then determined [[volumetric analysis|volumetrically]]; or the ammonia may be absorbed in [[hydrochloric acid]] and the ammonium chloride so formed precipitated as [[ammonium hexachloroplatinate]], {{chem2|[NH4]2[PtCl6]}}.{{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&nbsp;[[Parts-per notation|ppm]], and lethal above 500&nbsp;ppm by volume.<ref>(OSHA) Source: Sax, N. Irving (1984) ''Dangerous Properties of Industrial Materials''. 6th Ed. Van Nostrand Reinhold. {{ISBN|0-442-28304-0}}.</ref> 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.<ref name="Hurtado-2014">{{cite journal|last1=Hurtado|first1=J. L. Martinez|last2=Lowe|first2=C. R.|title=Ammonia-Sensitive Photonic Structures Fabricated in Nafion Membranes by Laser Ablation|journal=ACS Applied Materials & Interfaces|volume=6|issue=11|year=2014|pages=8903–8908|issn=1944-8244|doi=10.1021/am5016588|pmid=24803236}}</ref>

In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is [[ammonium chloride]] vapor) arises from the reaction between ammonia and HCl(g).<ref>{{Cite book |title=Holleman-Wiberg inorganic chemistry |date=2001 |publisher=Academic |isbn=978-0-12-352651-9 |editor-last=Holleman |editor-first=A. F. |location=San Diego, Calif. London |editor-last2=Wiberg |editor-first2=Egon |editor-last3=Wiberg |editor-first3=Nils |editor-last4=Eagleson |editor-first4=Mary |editor-last5=Brewer |editor-first5=William |editor-last6=Aylett |editor-first6=Bernhard J.}}</ref>

=== Ammoniacal nitrogen (NH<sub>3</sub>–N) ===
[[Ammoniacal nitrogen]] (NH<sub>3</sub>–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]]).

== History ==
[[File:Al-Jaahith - African Arab Naturalist - Basra - al jahiz.jpg|thumb|upright|Jabir ibn Hayyan wrote about ammonia in the 9th century]]
[[File:Ammoniak Reaktor BASF.jpg|thumb|upright|This high-pressure ammonia reactor was built in 1921 by [[BASF]] in [[Ludwigshafen]] and was re-erected on the premises of the [[University of Karlsruhe]] in Germany.]]
The ancient Greek historian [[Herodotus]] mentioned that there were [[outcrop]]s 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).<ref>Herodotus with George Rawlinson, trans., ''The History of Herodotus'' (New York, New York: Tandy-Thomas Co., 1909), vol.2, Book 4, § 181, [https://babel.hathitrust.org/cgi/pt?id=uva.x004090527;view=1up;seq=330 pp. 304–305.]</ref><ref>The land of the Ammonians is mentioned elsewhere in Herodotus' ''History'' and in [[Pausanias (geographer)|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, [https://babel.hathitrust.org/cgi/pt?id=uva.x000278335;view=1up;seq=277 p. 245], vol. 2, Book 3, § 25, [https://babel.hathitrust.org/cgi/pt?id=uva.x004090527;view=1up;seq=83 p. 73], and vol. 2, Book 3, § 26, [https://babel.hathitrust.org/cgi/pt?id=uva.x004090527;view=1up;seq=84 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 [https://babel.hathitrust.org/cgi/pt?id=mdp.39015028936014;view=1up;seq=125 111] and vol. 4, Book 9, Ch. 16, § 1, [https://babel.hathitrust.org/cgi/pt?id=mdp.39015028936030;view=1up;seq=251 p. 239.]</ref> 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]].<ref>Kopp, Hermann, ''Geschichte der Chemie'' [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, [https://archive.org/stream/geschichtederche03unse#page/236/mode/2up p. 237.] [in German]</ref> ''Hammoniacus sal'' appears in the writings of [[Pliny the Elder|Pliny]],<ref>{{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, [https://babel.hathitrust.org/cgi/pt?id=mdp.39015020434133;view=1up;seq=528 p. 502.]</ref> although it is not known whether the term is equivalent to the more modern sal ammoniac (ammonium chloride).{{sfn|Chisholm|1911|p=861}}<ref name="Webmineral">{{cite web|url=http://webmineral.com/data/Sal-ammoniac.shtml |title=Sal-ammoniac|publisher=Webmineral|access-date=7 July 2009}}</ref><ref>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. [https://archive.org/stream/naturalhistory08plinuoft#page/448/mode/2up 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, [https://books.google.com/books?id=mCU4AAAAMAAJ&pg=PA6 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), [https://archive.org/details/ancientmineralo01moorgoog/page/n103 pp. 96–97.]</ref>

The fermentation of [[urine]] by bacteria produces a [[Ammonia solution|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.<ref>See:
* Forbes, R.J., ''Studies in Ancient Technology'', vol. 5, 2nd ed. (Leiden, Netherlands: E.J. Brill, 1966), pp. [https://books.google.com/books?id=Zqg3AAAAIAAJ&pg=PA19 19], [https://books.google.com/books?id=Zqg3AAAAIAAJ&pg=PA48 48], and [https://books.google.com/books?id=Zqg3AAAAIAAJ&pg=PA65 65].
* Moeller, Walter O., ''The Wool Trade of Ancient Pompeii'' (Leiden, Netherlands: E.J. Brill, 1976), [https://books.google.com/books?id=g7wUAAAAIAAJ&pg=PA20 p. 20.]
* Faber, G.A. (pseudonym of: Goldschmidt, Günther) (May 1938) "Dyeing and tanning in classical antiquity," ''Ciba Review'', '''9''' : 277–312. Available at: [http://www.elizabethancostume.net/cibas/ciba9.html Elizabethan Costume]
* Smith, William, ''A Dictionary of Greek and Roman Antiquities'' (London, England: John Murray, 1875), article: "Fullo" (i.e., fullers or launderers), [https://babel.hathitrust.org/cgi/pt?id=hvd.hneuvp;view=1up;seq=570 pp. 551–553.]
* Rousset, Henri (31 March 1917) [https://books.google.com/books?id=WB4uWYU5V20C&pg=PA197 "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), [https://books.google.com/books?id=HIxfDQAAQBAJ&pg=PA112 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 (salt)|bittern]], a magnesium-rich solution that is a byproduct of making salt from sea water. Roasting struvite releases ammonia vapours.</ref> It was also used by [[Dentistry in ancient Rome|ancient dentists]] to wash teeth.<ref>{{Cite book |last=Lenkeit |first=Roberta Edwards |url=https://books.google.com/books?id=sapxDwAAQBAJ&dq=Teeth+whitening+ancient+Rome&pg=PA72 |title=High Heels and Bound Feet: And Other Essays on Everyday Anthropology, Second Edition |date=2018-10-23 |publisher=Waveland Press |isbn=978-1-4786-3841-4 |pages=72 |language=en}}</ref><ref>{{Cite book |last=Perdigão |first=Jorge |url=https://books.google.com/books?id=lB3KDAAAQBAJ&dq=Teeth+whitening+ancient+Rome&pg=PA170 |title=Tooth Whitening: An Evidence-Based Perspective |date=2016-08-03 |publisher=Springer |isbn=978-3-319-38849-6 |pages=170 |language=en}}</ref><ref>{{Cite book |last1=Bonitz |first1=Michael |url=https://books.google.com/books?id=EzW8BAAAQBAJ&dq=Teeth+whitening+ancient+Rome&pg=PA465 |title=Complex Plasmas: Scientific Challenges and Technological Opportunities |last2=Lopez |first2=Jose |last3=Becker |first3=Kurt |last4=Thomsen |first4=Hauke |date=2014-04-09 |publisher=Springer Science & Business Media |isbn=978-3-319-05437-7 |pages=465 |language=en}}</ref>

In the form of sal ammoniac (نشادر, ''nushadir''), ammonia was important to the [[Alchemy and chemistry in medieval Islam|Muslim alchemists]]. It was mentioned in the ''Book of Stones'', likely written in the 9th century and attributed to [[Jābir ibn Hayyān]].<ref name="Haq-1995">{{cite book|last=Haq|first=Syed Nomanul|title=Names, Natures and Things: The Alchemist Jabir Ibn Hayyan and His Kitab Al-Ahjar (Book of Stones)|url=https://books.google.com/books?id=P-70YjP0nj8C|year=1995|publisher=Springer|isbn=978-0-7923-3254-1}}</ref> It was also important to the European [[alchemists]] of the 13th century, being mentioned by [[Albertus Magnus]].{{sfn|Chisholm|1911|p=861}} It was also used by [[dye]]rs 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.<ref>''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.). [https://books.google.com/books?id=UlhcAAAAcAAJ&pg=PA81 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 vapours, which is atop the distillation flask] ...)<br />
See also: Kopp, Hermann, ''Geschichte der Chemie'' [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, [https://archive.org/stream/geschichtederche03unse#page/243/mode/2up p. 243.] [in German]
</ref> 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}}<ref>{{cite book|url=https://books.google.com/books?id=kwQQaltqByAC&pg=PA72|page=72|title=Historical Studies in the Language of Chemistry|author=Maurice P. Crosland|publisher=Courier Dover Publications|year=2004|isbn=978-0-486-43802-3}}</ref>

Gaseous ammonia was first isolated by [[Joseph Black]] in 1756 by reacting ''sal ammoniac'' ([[ammonium chloride]]) with ''calcined magnesia'' ([[magnesium oxide]]).<ref>{{Cite book|url=https://archive.org/details/b21730738|title=Experiments upon magnesia alba, quick-lime, and other alcaline substances|last=Black|first=Joseph|date=1893|publisher=W.F. Clay|location=Edinburgh|orig-year=1755}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=UeGlmU2F8_8C&pg=PA14|title=Air Pollution and Global Warming: History, Science, and Solutions|last=Jacobson|first=Mark Z.|date=2012-04-23|publisher=Cambridge University Press|isbn=9781107691155|language=en}}</ref> It was isolated again by [[Peter Woulfe]] in 1767,<ref>{{Cite news|url=https://www.chemistryworld.com/opinion/woulfes-bottle/2500114.article|title=Woulfe's bottle|work=Chemistry World|access-date=2017-07-01|language=en}}</ref><ref>{{Cite journal|last=Woulfe|first=Peter|date=1767-01-01|title=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.|journal=Philosophical Transactions|language=en|volume=57|pages=517–536|doi=10.1098/rstl.1767.0052|issn=0261-0523|bibcode=1767RSPT...57..517W|url=https://zenodo.org/record/1432252|doi-access=free}}</ref> by [[Carl Wilhelm Scheele]] in 1770<ref>{{cite book |hdl= 1811/28946/Pictorial%20Life%20History_Scheele.pdf |title= Pictorial life history of the apothecary chemist Carl Wilhelm Scheele |publisher= American Institute of the History of Pharmacy |year= 1942 |last1= Urdang |first1= George }}</ref> and by [[Joseph Priestley]] in 1773 and was termed by him 'alkaline air'.{{sfn|Chisholm|1911|p=861}}<ref>See:
* Priestley, Joseph (1773) [https://archive.org/stream/observationsetm02pari#page/388/mode/2up "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), [https://archive.org/stream/experimentsobser01prie#page/162/mode/2up 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), [https://books.google.com/books?id=qL9K2e4KIvsC&pg=PA94 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), [https://archive.org/details/b30532401_0001/page/239 pp. 239–240.]</ref> Eleven years later in 1785, [[Claude Louis Berthollet]] ascertained its composition.<ref>Berthollet (1785) [http://gallica.bnf.fr/ark:/12148/bpt6k35847/f490.item.zoom "Analyse de l'alkali volatil"] (Analysis of volatile alkali), ''Mémoires de l'Académie Royale des Sciences'', 316–326.</ref>{{sfn|Chisholm|1911|p=861}}

The production of ammonia from nitrogen in the air (and hydrogen) was invented by [[Fritz Haber]] and Robert LeRossignol. The patent was sent in 1909 (USPTO Nr 1,202,995) and awarded in 1916. Later, [[Carl Bosch]] developed the industrial method for ammonia production ([[Haber–Bosch process]]). It was first used on an industrial scale in [[Germany]] during [[World War I]],<ref name="Max Appl-2006">{{cite book|author=Max Appl |title=Ammonia, in Ullmann's Encyclopedia of Industrial Chemistry|year= 2006|publisher= Wiley-VCH|location= Weinheim|doi=10.1002/14356007.a02_143.pub2|chapter=Ammonia|isbn=978-3527306732}}</ref> following the allied blockade that cut off the supply of [[nitrate]]s from [[Chile]]. The ammonia was used to produce explosives to sustain war efforts.<ref name="Smith-2001" >{{cite book|author=Smith, Roland|title=Conquering Chemistry|year=2001|isbn=978-0-07-470146-1|publisher=McGraw-Hill|location=Sydney}}</ref> The Nobel Prize in Chemistry 1918 was awarded to Fritz Haber "for the synthesis of ammonia from its elements".

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.

== Applications ==

=== Fertiliser ===
In the US {{As of|2019|lc=y}}, approximately 88% of ammonia was used as [[fertiliser]]s either as its salts, solutions or [[anhydrous]]ly.<ref name="USGS-2020">{{cite web |url=https://pubs.usgs.gov/periodicals/mcs2020/mcs2020.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://pubs.usgs.gov/periodicals/mcs2020/mcs2020.pdf |archive-date=2022-10-09 |url-status=live |title=Mineral Commodity Summaries 2020, p. 117 – Nitrogen |publisher=[[USGS]] |year=2020 |access-date=12 February 2020}}</ref> When applied to soil, it helps provide increased yields of [[crop]]s such as [[maize]] and [[wheat]].<ref>{{cite journal |last1=Lassaletta |first1=Luis |last2=Billen |first2=Gilles |last3=Grizzetti |first3=Bruna |last4=Anglade |first4=Juliette |last5=Garnier |first5=Josette |title=50-year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland|journal=Environmental Research Letters |date=2014 |volume=9 |issue=10 |pages=105011 |doi=10.1088/1748-9326/9/10/105011 |language=en |issn=1748-9326 |bibcode=2014ERL.....9j5011L |doi-access=free}}</ref> 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia, and worldwide, 110&nbsp;million tonnes are applied each year.<ref>{{cite news|url=https://www.washingtonpost.com/national/health-science/anhydrous-ammonia-fertilizer-abundant-important-hazardous/2013/04/18/c2d4c69c-a85a-11e2-a8e2-5b98cb59187f_story.html|title=Anhydrous ammonia fertilizer: abundant, important, hazardous|newspaper=Washington Post|author=David Brown|date=18 April 2013|access-date=23 April 2013}}</ref>
Solutions of ammonia ranging from 16% to 25% are used in the [[Industrial fermentation|fermentation]] industry as a source of nitrogen for microorganisms and to adjust pH during fermentation.<ref>{{Cite web|title=Applications of Anhydrous Ammonia and Aqueous Ammonia|url=https://www.mysoreammonia.com/applications/|access-date=2022-02-02|website=www.mysoreammonia.com}}</ref>

=== Refrigeration–R717 ===
Because of ammonia's vapourization properties, it is a useful [[refrigerant]].<ref name="Max Appl-2006"/> It was commonly used before the popularisation of [[chlorofluorocarbon]]s (Freons). Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high [[Energy conversion efficiency|energy efficiency]] and low cost. It suffers from the disadvantage of toxicity, and requiring corrosion resistant components, which restricts its domestic and small-scale use. Along with its use in modern [[vapour-compression refrigeration]] it is used in a mixture along with hydrogen and water in [[absorption refrigerator]]s. 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 radiators aboard the [[International Space Station]] in loops that are used to regulate the internal temperature and enable temperature-dependent experiments.<ref>{{Cite news|url=https://www.nasa.gov/content/cooling-system-keeps-space-station-safe-productive|title=Cooling System Keeps Space Station Safe, Productive|last=Wright|first=Jerry|date=2015-04-13|work=NASA|access-date=2017-07-01|language=en|archive-date=12 January 2017|archive-url=https://web.archive.org/web/20170112183545/https://www.nasa.gov/content/cooling-system-keeps-space-station-safe-productive/|url-status=dead}}</ref><ref>{{Cite news|url=http://www.space.com/21059-space-station-cooling-system-explained-infographic.html|title=International Space Station's Cooling System: How It Works (Infographic)|work=Space.com|access-date=2017-07-01}}</ref> The ammonia is under sufficient pressure to remain liquid throughout the process. Single-phase ammonia cooling systems also serve the power electronics in each pair of solar arrays.

The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are potent and stable greenhouse gases.<ref>{{Cite news|title=Reducing Hydrofluorocarbon (HFC) Use and Emissions in the Federal Sector through SNAP|url=https://www.epa.gov/sites/production/files/2016-12/documents/epa_hfc_federal_sector.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.epa.gov/sites/production/files/2016-12/documents/epa_hfc_federal_sector.pdf |archive-date=2022-10-09 |url-status=live|access-date=2018-12-02}}</ref>

=== Antimicrobial agent for food products ===
As early as in 1895, it was known that ammonia was 'strongly [[antiseptic]] ... it requires 1.4&nbsp;grams per litre to preserve [[Broth|beef tea]] (broth).'<ref>{{cite book|url=https://archive.org/details/disinfectiondisi00rideuoft|title=Disinfection and Disinfectants: An Introduction to the Study of|author=Samuel Rideal|publisher=Charles Griffin and Company|place=London|year=1895|page=[https://archive.org/details/disinfectiondisi00rideuoft/page/109 109]}}</ref> In one study, anhydrous ammonia destroyed 99.999% of [[zoonotic bacteria]] in three types of [[compound feed|animal feed]], but not [[silage]].<ref>{{cite journal|doi=10.1016/j.ijfoodmicro.2007.11.040|title=Ammonia disinfection of animal feeds – Laboratory study|author=Tajkarimi, Mehrdad|journal=International Journal of Food Microbiology|volume=122|issue= 1–2|year=2008|pages=23–28|pmid=18155794|last2=Riemann|first2=H. P.|last3=Hajmeer|first3=M. N.|last4=Gomez|first4=E. L.|last5=Razavilar|first5=V.|last6=Cliver|first6=D. O.|display-authors=etal}}</ref><ref>{{cite journal |last1=Kim |first1=J. S. |last2=Lee |first2=Y. Y. |last3=Kim |first3=T. H. |title=A review on alkaline pretreatment technology for bioconversion of lignocellulosic biomass. |journal=Bioresource Technology |date=January 2016 |volume=199 |pages=42–48 |doi=10.1016/j.biortech.2015.08.085 |pmid=26341010|bibcode=2016BiTec.199...42K }}</ref> Anhydrous ammonia is currently used commercially to reduce or eliminate [[microbial]] contamination of [[beef]].<ref>"[https://web.archive.org/web/20110811220534/http://asae.frymulti.com/abstract.asp?aid=27245&t=2 Evaluation of Treatment Methods for Reducing Bacteria in Textured Beef]", Jensen, Jean L ''et al.'', [[American Society of Agricultural and Biological Engineers]] Annual Meeting 2009</ref><ref>''[http://haccpalliance.org/sub/Antimicrobial%20Interventions%20for%20Beef.pdf Reference 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 12</ref>
Lean 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.<ref>{{cite news | url = https://www.nytimes.com/2009/10/04/health/04meat.html | work=The New York Times | title=The Burger That Shattered Her Life | first=Michael | last=Moss | date=3 October 2009}}</ref> There have been safety concerns about the process as well as consumer complaints about the taste and smell of ammonia-treated beef.<ref>{{cite news | url = https://www.nytimes.com/2009/12/31/us/31meat.html | work=The New York Times | title=Safety of Beef Processing Method Is Questioned | first=Michael | last=Moss | date=31 December 2009}}</ref>

=== Fuel ===
[[File:AmmoniacalGasEngineStreetcarARWaud.jpeg|thumb|Ammoniacal Gas Engine [[Streetcars in New Orleans|Streetcar in New Orleans]] drawn by [[Alfred Waud]] in 1871]]
Ammonia has been used as fuel, and is a proposed alternative to fossil fuels and hydrogen. Being liquid at ambient temperature under its own vapour pressure and having high volumetric and gravimetric energy density, ammonia is considered a suitable carrier for hydrogen,<ref>{{Cite web|date=2022-02-03|title=MOL studies ammonia FSRU concept|url=https://www.offshore-energy.biz/mol-studies-ammonia-fsru-concept/|access-date=2022-02-03|website=Offshore Energy|language=en-US}}</ref> and may be cheaper than direct transport of liquid hydrogen.<ref>{{Cite web|last=Collins (l_collins)|first=Leigh|date=2022-01-27|title=SPECIAL REPORT {{!}} Why shipping pure hydrogen around the world might already be dead in the water {{!}} Recharge|url=https://www.rechargenews.com/energy-transition/special-report-why-shipping-pure-hydrogen-around-the-world-might-already-be-dead-in-the-water/2-1-1155434|access-date=2022-02-03|website=Recharge {{!}} Latest renewable energy news|language=en}}</ref>

Compared to hydrogen, ammonia is easier to store. 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 or as a cryogenic liquid.<ref name="Lan-2014" /><ref>{{cite web |last=Lindzon |first=Jared |date=27 February 2019 |title=He's Creating a New Fuel Out of Thin Air – for 85 Cents per Gallon |url=http://www.ozy.com/rising-stars/hes-creating-a-new-fuel-out-of-thin-air-for-85-cents-per-gallon/92686 |access-date=26 April 2019 |website=OZY |archive-date=26 April 2019 |archive-url=https://web.archive.org/web/20190426171820/https://www.ozy.com/rising-stars/hes-creating-a-new-fuel-out-of-thin-air-for-85-cents-per-gallon/92686 |url-status=dead }}</ref> The raw [[energy density]] of liquid ammonia is 11.5&nbsp;MJ/L,<ref name="Lan-2014">{{Cite journal|last1=Lan|first1=Rong|last2=Tao|first2=Shanwen|date=28 August 2014|title=Ammonia as a suitable fuel for fuel cells|journal=Frontiers in Energy Research|volume=2|pages=35|doi=10.3389/fenrg.2014.00035|doi-access=free}}</ref> which is about a third that of [[diesel fuel|diesel]].

Ammonia can be converted back to hydrogen to be used to power hydrogen fuel cells, or it may be used directly within high-temperature [[solid oxide fuel cell|solid oxide]] direct ammonia fuel cells to provide efficient power sources that do not emit [[greenhouse gas]]es.<ref>{{cite journal|last1=Giddey|first1=S.|last2=Badwal|first2=S. P. S.|last3=Munnings|first3=C.|last4=Dolan|first4=M.|title=Ammonia as a Renewable Energy Transportation Media|journal=ACS Sustainable Chemistry & Engineering|volume=5|issue=11|pages=10231–10239|date=10 October 2017|doi=10.1021/acssuschemeng.7b02219}}</ref><ref name="Afif-2016">{{cite journal|last1=Afif|first1=Ahmed|last2=Radenahmad|first2=Nikdilila|last3=Cheok|first3=Quentin|last4=Shams|first4=Shahriar|last5=Hyun Kim|first5=Jung|last6=Azad|first6=Abul|date=2016-02-12|title=Ammonia-fed fuel cells: a comprehensive review|url=https://www.researchgate.net/publication/294579196|journal=[[Renewable and Sustainable Energy Reviews]]|volume=60|pages=822–835|doi=10.1016/j.rser.2016.01.120|bibcode=2016RSERv..60..822A |access-date=2021-01-01}}</ref> Ammonia to hydrogen conversion can be achieved through the [[sodium amide]] process<ref name="David-2014">{{Cite journal |last1=David |first1=William I. F. |last2=Makepeace |first2=Joshua W. |last3=Callear |first3=Samantha K. |last4=Hunter |first4=Hazel M. A. |last5=Taylor |first5=James D. |last6=Wood |first6=Thomas J. |last7=Jones |first7=Martin O. |date=2014-09-24 |title=Hydrogen Production from Ammonia Using Sodium Amide |journal=Journal of the American Chemical Society |volume=136 |issue=38 |pages=13082–13085 |doi=10.1021/ja5042836 |issn=0002-7863 |pmid=24972299 |doi-access=free|bibcode=2014JAChS.13613082D }}</ref> or the catalytic decomposition of ammonia using solid catalysts.<ref>{{Cite journal |last1=Lucentini |first1=Ilaria |last2=García Colli |first2=Germán |last3=Luzi |first3=Carlos D. |last4=Serrano |first4=Isabel |last5=Martínez |first5=Osvaldo M. |last6=Llorca |first6=Jordi |date=2021-06-05 |title=Catalytic ammonia decomposition over Ni–Ru supported on CeO<sub>2</sub> for hydrogen production: Effect of metal loading and kinetic analysis |url=https://www.sciencedirect.com/science/article/pii/S0926337321000229|journal=Applied Catalysis B: Environmental |language=en |volume=286 |pages=119896 |doi=10.1016/j.apcatb.2021.119896 |bibcode=2021AppCB.28619896L |s2cid=233540470 |issn=0926-3373|hdl=2117/364129 |hdl-access=free }}</ref>
[[File:X-15.jpg|thumb|The [[X-15]] [[aircraft]] used ammonia as one component [[fuel]] of its [[rocket engine]]]]
Ammonia engines or ammonia motors, using ammonia as a [[working fluid]], have been proposed and occasionally used.<ref>{{cite web|author=Douglas Self|author-link=Douglas Self|url=http://www.douglas-self.com/MUSEUM/POWER/ammonia/ammonia.htm|title=Ammonia Motors|date=1 October 2007|access-date=28 November 2010}}</ref> 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 Streetcar Line]] in [[New Orleans]] in the 1870s and 1880s,<ref name="Elbridge Harper Charlton-1965">{{Cite book |title=The Streetcars of New Orleans |author=Louis C. Hennick |author2=Elbridge Harper Charlton |date = 1965 |publisher =Pelican Publishing |isbn=9781455612598 |pages =14–16 }}</ref> and during [[World War II]] ammonia was used to power buses in [[Belgium]].<ref name="Olson-2007" />

Ammonia is sometimes proposed as a practical alternative to [[fossil fuel]] for [[internal combustion engine]]s.<ref name="Olson-2007">{{cite news|url=http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007/Olson2_NH3.pdf |title=Ammonia as a Transportation Fuel IV |date=15–16 October 2007 |publisher=Norm Olson – Iowa Energy Center |url-status=dead |archive-url=https://web.archive.org/web/20120207092554/http://www.energy.iastate.edu/Renewable/ammonia/ammonia/2007/Olson2_NH3.pdf |archive-date=7 February 2012}}</ref><ref name="Lee-2017">{{cite web |title=Development of new combustion strategy for internal combustion engine fueled by pure ammonia |last1=Lee |first1=Dongeun |last2=Min |first2=Hyungeun |last3=Park |first3=Hyunho |last4=Song |first4=Han Ho |url=https://nh3fuelassociation.org/wp-content/uploads/2017/11/NH3-Energy-2017-Donggeun-Lee.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://nh3fuelassociation.org/wp-content/uploads/2017/11/NH3-Energy-2017-Donggeun-Lee.pdf |archive-date=2022-10-09 |url-status=live |publisher=Seoul National University, Department of Mechanical Engineering |date=2017-11-01 |access-date=2019-01-29}}</ref><ref name="Brohi-2014">{{cite web |title=Ammonia as fuel for internal combustion engines? |author=Brohi, Emtiaz Ali |url=http://publications.lib.chalmers.se/records/fulltext/207145/207145.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://publications.lib.chalmers.se/records/fulltext/207145/207145.pdf |archive-date=2022-10-09 |url-status=live |publisher=Chalmers University of Technology |year=2014 |access-date=2019-01-29}}</ref><ref>{{Cite web |last=Elucidare |date=2 February 2008 |title=Ammonia: New possibilities for hydrogen storage and transportation |url=http://www.elucidare.co.uk/news/Ammonia%20as%20H2%20carrier.pdf |url-status=live |website=Elucidare Limited|archive-url=https://web.archive.org/web/20101008200842/http://www.elucidare.co.uk:80/news/Ammonia%20as%20H2%20carrier.pdf |archive-date=8 October 2010 }}</ref> However, ammonia cannot be easily used in existing [[Otto cycle]] engines because of its very narrow [[#Combustion|flammability range]]. Despite this, several tests have been run.<ref>{{YouTube|L0hBAz6MxC4|Ammonia Powered Car}}</ref><ref>{{cite web |title=Watch 'Ammonia Fuel' |url=http://www.gregvezina.ca |access-date=7 July 2009 |publisher=Greg Vezina}}</ref><ref>{{cite web |title=Welcome to NH3 Car |url=http://www.nh3car.com/ |archive-url=https://web.archive.org/web/20071214103433/http://nh3car.com/ |url-status=usurped |archive-date=14 December 2007 |work=NH3Car.com}}</ref> Its high [[octane rating]] of 120<ref name="bris.ac.uk">{{cite web|url=http://www.chm.bris.ac.uk/motm/ammonia/Ammonia%20MOTM.htm|title=Ammonia|publisher=chm.bris.ac.uk|access-date=3 March 2016}}</ref> and low flame temperature<ref name="Zacharakis-Jutz-2013">{{cite web |title=Characteristics of an SI Engine Using Direct Ammonia Injection |last1=Zacharakis-Jutz |first1=George |last2=Kong |first2=Song-Charng |url=https://nh3fuelassociation.org/wp-content/uploads/2013/10/nh3fcx-song-charng-kong.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://nh3fuelassociation.org/wp-content/uploads/2013/10/nh3fcx-song-charng-kong.pdf |archive-date=2022-10-09 |url-status=live |publisher=Department of Mechanical Engineering, Iowa State University |year=2013 |access-date=2019-01-29}}</ref> allows the use of high compression ratios without a penalty of high [[NOx|{{NOx}}]] production. Since ammonia contains no carbon, its combustion cannot produce [[carbon dioxide]], [[carbon monoxide]], [[hydrocarbons]], or [[soot]].

Ammonia production currently creates 1.8% of global {{CO2}} emissions. 'Green ammonia' is ammonia produced by using [[green hydrogen]] (hydrogen produced by electrolysis with electricity from [[Renewable energy|renewable]] energy), whereas 'blue ammonia' is ammonia produced using [[blue hydrogen]] (hydrogen produced by steam methane reforming (= SMR) where the carbon dioxide has been captured and stored (cfr. carbon capture and storage = CCS).<ref>{{Cite web|url=https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme/green-ammonia/|title=Green ammonia &#124; Royal Society|website=royalsociety.org}}</ref>

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 oxidiser, [[liquid oxygen]], which simplified the aircraft's design.

In 2020, [[Saudi Arabia]] shipped 40 [[metric tons]] of liquid 'blue ammonia' to Japan for use as a fuel.<ref>{{Cite news|date=2020-09-27|title=Saudi Arabia Sends Blue Ammonia to Japan in World-First Shipment|url=https://www.bloomberg.com/news/articles/2020-09-27/saudi-arabia-sends-blue-ammonia-to-japan-in-world-first-shipment|access-date=2020-09-28|website=Bloomberg.com}}</ref> It was produced as a by-product by petrochemical industries, and can be burned without giving off [[greenhouse gas]]es. Its energy density by volume is nearly double that of liquid hydrogen. If the process of creating it can be scaled up via purely renewable resources, producing green ammonia, it could make a major difference in [[avoiding climate change]].<ref>{{Cite web|last1=Service|first1=Robert F.|date=2018-07-12|title=Ammonia—a renewable fuel made from sun, air, and water—could power the globe without carbon|url=https://www.science.org/content/article/ammonia-renewable-fuel-made-sun-air-and-water-could-power-globe-without-carbon|access-date=2020-09-28|website=Science {{!}} AAAS|language=en}}</ref> The company [[ACWA Power]] and the city of [[Neom]] have announced the construction of a green hydrogen and ammonia plant in 2020.<ref>{{Cite web|date=2020-09-17|title=Will Saudi Arabia build the world's largest green hydrogen and ammonia plant?|website=energypost.eu|access-date=2020-10-09|url=https://energypost.eu/will-saudi-arabia-build-the-worlds-largest-green-hydrogen-and-ammonia-plant/}}</ref>

Green ammonia is considered as a potential fuel for future container ships. In 2020, the companies [[DSME]] and [[MAN Energy Solutions]] announced the construction of an ammonia-based ship, DSME plans to commercialize it by 2025.<ref>{{Cite web|date=6 October 2020 |title=DSME gets LR AIP for ammonia-fueled 23,000 TEU boxship|website=Offshore Energy|access-date=9 October 2020|url=https://www.offshore-energy.biz/dsme-gets-lr-aip-for-ammonia-fueled-23000-teu-boxship/}}</ref> The use of ammonia as a potential alternative fuel for [[aircraft]] [[jet engine]]s is also being explored.<ref>{{cite web |url=https://aviafuture.com/index.php/2022/03/30/what-will-power-aircraft-in-the-future/#ammonia |title=What will power aircraft in the future? |date=30 March 2022 |website=Aviafuture |access-date=24 May 2022 }}</ref>

Japan intends to implement a plan to develop ammonia co-firing technology that can increase the use of ammonia in power generation, as part of efforts to assist domestic and other Asian utilities to accelerate their transition to [[carbon neutrality]].<ref>{{cite web |url=https://www.argusmedia.com/en/news/2227810-japan-to-advance-ammonia-cofiring-technology |title=Japan to advance ammonia co-firing technology |date=24 June 2021 |website=[[Argus Media]] |access-date=8 November 2021 }}</ref>
In October 2021, the first International Conference on Fuel Ammonia (ICFA2021) was held.<ref>{{cite web |url=https://icfa2021.com/en/index.html |title=First International Conference on Fuel Ammonia 2021 |date=6 October 2021 |website=ICFA |access-date=7 November 2021 |archive-date=7 November 2021 |archive-url=https://web.archive.org/web/20211107071827/https://icfa2021.com/en/index.html |url-status=dead }}</ref><ref>{{cite web |url=https://www.meti.go.jp/english/press/2021/1012_002.html |date=12 October 2021 |title=First International Conference on Fuel Ammonia Held |website=[[Ministry of Economy, Trade and Industry|METI, Japan]] |access-date=7 November 2021 }}</ref>

In June 2022, [[IHI Corporation]] succeeded in reducing greenhouse gases by over 99% during combustion of liquid ammonia in a 2,000-kilowatt-class gas turbine achieving truly {{CO2}}-free power generation.<ref>{{Cite press release |title={{CO2}}-free power generation achieved with the world's first gas turbine using 100% liquid ammonia |date=16 June 2022 |url=https://www.ihi.co.jp/en/all_news/2022/resources_energy_environment/1197938_3488.html |publisher=[[IHI Corporation]] |access-date=1 July 2022 }}</ref>
In July 2022, [[Quadrilateral Security Dialogue|Quad]] nations of Japan, the U.S., Australia and India agreed to promote technological development for clean-burning hydrogen and ammonia as fuels at the security grouping's first energy meeting.<ref>{{Cite news|date=14 July 2022 
|author=Masaya Kato |title=Quad members agree to promote hydrogen, ammonia fuel tech |url=https://www.ihi.co.jp/en/all_news/2022/resources_energy_environment/1197938_3488.html |publisher=[[The Nikkei]] |access-date=14 July 2022 }}</ref> {{As of|2022}}, however, significant amounts of {{NOx}} are produced.<ref>{{Cite web |title=On the use of ammonia as a fuel – A perspective |url=https://hal-cnrs.archives-ouvertes.fr/hal-03675905/file/2022%20NH3%20perspective.pdf}}</ref> [[Nitrous oxide]] may also be a problem as it is a "''greenhouse gas that is known to possess up to 300 times the Global Warming Potential (GWP) of carbon dioxide''".<ref>{{Cite web |title=Nitrogen Oxides as a By-product of Ammonia/Hydrogen Combustion Regimes |url=https://orca.cardiff.ac.uk/id/eprint/144277/3/ICLCA21_0206%20ed%20V3%20without%20comments.pdf}}</ref>

The [[International Energy Agency|IEA]] forecasts that ammonia will meet approximately 45% of shipping fuel demands by 2050.<ref>{{Cite news |last=Mehta |first=Amgeli |date=May 15, 2023 |title=In the voyage to net-zero, which green shipping fuel will rule the seas? |url=https://www.reuters.com/sustainability/climate-energy/voyage-net-zero-which-green-shipping-fuel-will-rule-seas-2023-05-15/ |work=Reuters}}</ref>

At high temperature and in the presence of a suitable [[catalyst]] ammonia decomposes into its constituent elements.<ref name="White-1905">{{Cite journal |last1=White |first1=Alfred H. |last2=Melville |first2=Wm. |title=The Decomposition of Ammonia at High Temperatures |date=April 1905 |url=https://pubs.acs.org/doi/abs/10.1021/ja01982a005 |journal=Journal of the American Chemical Society |language=en |volume=27 |issue=4 |pages=373–386 |doi=10.1021/ja01982a005 |bibcode=1905JAChS..27..373W |issn=0002-7863}}</ref> Decomposition of ammonia is a slightly endothermic process requiring 23&nbsp;kJ/mol (5.5&nbsp;[[kcal/mol]]) of ammonia, and yields [[hydrogen]] and [[nitrogen]] gas.

=== Other ===
==== 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 fertiliser. Ammonia neutralises the nitrogen oxide ({{NOx}}) pollutants emitted by diesel engines. This technology, called SCR ([[selective catalytic reduction]]), relies on a [[vanadia]]-based catalyst.<ref>{{cite web|access-date=7 July 2009|url=http://www.businessweek.com/bwdaily/dnflash/content/mar2008/db20080321_748642_page_3.htm |archive-url=https://web.archive.org/web/20080510094255/http://www.businessweek.com/bwdaily/dnflash/content/mar2008/db20080321_748642_page_3.htm |url-status=dead |archive-date=10 May 2008 |title=Diesel: Greener Than You Think}}</ref>

Ammonia may be used to mitigate gaseous spills of [[phosgene]].<ref>{{cite web | publisher = [[International Programme on Chemical Safety]] | title = Phosgene: Health and Safety Guide | year = 1998 | url = http://www.inchem.org/documents/hsg/hsg/hsg106.htm}}</ref>

==== Stimulant ====
[[File:Meth ammonia tank Otley iowa.JPG|thumb|Anti-[[methamphetamine|meth]] sign on tank of anhydrous ammonia, [[Otley, Iowa]]. Anhydrous ammonia is a common farm fertiliser that is also a critical ingredient in making methamphetamine. In 2005, Iowa used grant money to provide thousands of locks to prevent criminals from gaining access to the tanks.<ref>{{Cite news|url=http://thegazette.com/2009/10/06/anhydrous-ammonia-tank-locks-have-flaws |title=Anhydrous ammonia tank locks have flaws|newspaper=Cedar Rapids Gazette|date=6 October 2009}}</ref>]]
Ammonia, as the vapour 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]].<ref>{{cite web |url=http://www.illinoisattorneygeneral.gov/methnet/understandingmeth/basics.html |title=Illinois Attorney General &#124; Basic Understanding of Meth |publisher=Illinoisattorneygeneral.gov |access-date=21 May 2011 |archive-url=https://web.archive.org/web/20100910041147/http://www.illinoisattorneygeneral.gov/methnet/understandingmeth/basics.html |archive-date=10 September 2010 |url-status=dead}}</ref> 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.<ref>{{Cite book|url=https://books.google.com/books?id=NnZ23IqU4SoC&q=ammonia+birch+method+danger&pg=PA759|title=Occupational, Industrial, and Environmental Toxicology|last=Greenberg|first=Michael I.|date=2003-01-01|publisher=Elsevier Health Sciences|isbn=978-0323013406|language=en}}</ref>

==== Textile ====
Liquid ammonia is used for treatment of cotton materials, giving properties like [[mercerisation]], using alkalis. In particular, it is used for prewashing of wool.<ref>{{Cite journal|last1=Włochowicz|first1=A.|last2=Stelmasiak|first2=E.|s2cid=96930751|title=Change in thermal properties of wool after treatment with liquid ammonia|journal=Journal of Thermal Analysis and Calorimetry|volume=26|issue=1|year=1983|page=17|doi=10.1007/BF01914084}}</ref>

==== 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 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).<ref>{{cite book |last1=Horkheimer |first1=Donald |title=AIAA 5th ATIO and 16th Lighter-Than-Air Sys Tech. And Balloon Systems Conferences |chapter=Ammonia – A Solution for Airships Demanding Rapid Changes in Net Buoyancy |chapter-url=https://doi.org/10.2514/6.2005-7393|year=2005 |doi=10.2514/6.2005-7393 |isbn=978-1-62410-067-3 |access-date=27 October 2022}}</ref>

==== Fuming ====
{{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 [[tannin]]s in the [[wood]] and cause it to change colour.<ref>[http://www.woodweb.com/knowledge_base/Fuming_white_oak.html Fuming white oak]. woodweb.com</ref>

==== Safety ====
[[File:Ammiakoprovod NS.jpg|thumb|upright|The world's longest ammonia [[pipeline transport|pipeline]] (roughly 2400&nbsp;km long),<ref>minerals year book, vol. 3</ref> running from the [[TogliattiAzot]] plant in [[Russia]] to [[Odesa]] in [[Ukraine]]]]
The US [[Occupational Safety and Health Administration|Occupational Safety and Health Administration (OSHA)]] has set a 15-minute exposure limit for gaseous ammonia of 35&nbsp;ppm by volume in the environmental air and an 8-hour exposure limit of 25&nbsp;ppm by volume.<ref name="Toxic FAQ Sheet for Ammonia-2004">{{cite news|url=https://www.atsdr.cdc.gov/toxfaqs/tfacts126.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.atsdr.cdc.gov/toxfaqs/tfacts126.pdf |archive-date=2022-10-09 |url-status=live |title=Toxic FAQ Sheet for Ammonia| publisher=[[Agency for Toxic Substances and Disease Registry]] (ATSDR)|date= September 2004}}</ref> The [[National Institute for Occupational Safety and Health]] (NIOSH) recently reduced the IDLH (Immediately Dangerous to Health or Life, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 ppm to 300 ppm based on recent more conservative interpretations of original research in 1943. The 1 hour IDLH limit is still 500 ppm. Other organisations have varying exposure levels. US Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): for continuous exposure (60 days) is 25&nbsp;ppm; for exposure of 1 hour is 400&nbsp;ppm.<ref>[https://www.cdc.gov/niosh/idlh/7664417.html Ammonia], IDLH Documentation</ref>

Ammonia vapour has a sharp, irritating, pungent odor that acts as a warning of potentially dangerous exposure. The average odor threshold is 5&nbsp;ppm, well below any danger or damage. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death.<ref name="Toxic FAQ Sheet for Ammonia-2004"/> Ammonia is regulated in the US as a non-flammable gas, but it meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than {{convert|3,500|gal}}.<ref>[http://www.fmcsa.dot.gov/faq/anhydrous-ammonia-covered-under-hazardous-materials-safety-permit-program Is Anhydrous Ammonia covered under the Hazardous Materials Safety Permit Program?] from the website of the [[United States Department of Transportation]] (DOT)</ref>

Liquid ammonia is dangerous because it is [[hygroscopic]] and because it can cause [[caustic burn]]s. See {{section link|Gas carrier|Health effects of specific cargoes carried on gas carriers}} for more information.

== Toxicity ==
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 acid]]s or excreted in the urine.<ref>{{cite book |last1=Berg |first1=J. M. |last2=Tymoczko |first2=J. L. |last3=Stryer |first3=L. |title=Biochemistry |url=https://www.ncbi.nlm.nih.gov/books/NBK22450/ |edition=5th |year=2002 |section=23.4: Ammonium Ion is Converted into Urea in Most Terrestrial Vertebrates}}</ref> [[Fish]] and [[amphibian]]s 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 [[Directive 67/548/EEC|classified]] as ''"dangerous for the environment"''. Atmospheric ammonia plays a key role in the formation of [[fine particulate matter]].<ref>{{Cite journal |last1=Wang |first1=Mingyi |last2=Kong |first2=Weimeng |last3=Marten |first3=Ruby |last4=He |first4=Xu-Cheng |last5=Chen |first5=Dexian |last6=Pfeifer |first6=Joschka |last7=Heitto |first7=Arto |last8=Kontkanen |first8=Jenni |last9=Dada |first9=Lubna |last10=Kürten |first10=Andreas |last11=Yli-Juuti |first11=Taina |date=2020-05-13 |title=Rapid growth of new atmospheric particles by nitric acid and ammonia condensation |journal=Nature |language=en |volume=581 |issue=7807 |pages=184–189 |doi=10.1038/s41586-020-2270-4 |pmid=32405020 |pmc=7334196 |bibcode=2020Natur.581..184W |issn=1476-4687}}</ref>

Ammonia is a constituent of [[tobacco smoke]].<ref name="Talhout-2011">{{cite journal |last1=Talhout |first1=Reinskje |last2=Schulz |first2=Thomas |last3=Florek |first3=Ewa |last4=Van Benthem |first4=Jan |last5=Wester |first5=Piet |last6=Opperhuizen |first6=Antoon |title=Hazardous Compounds in Tobacco Smoke |journal=International Journal of Environmental Research and Public Health |volume=8 |issue=12 |year=2011 |pages=613–628 |issn=1660-4601 |doi=10.3390/ijerph8020613 |pmid=21556207 |pmc=3084482 |doi-access=free}}</ref>

=== Coking wastewater ===
Ammonia is present in coking wastewater streams, as a liquid by-product of the production of [[Coke (fuel)|coke]] from [[coal]].<ref>{{Cite web|title = Cutting-Edge Solutions For Coking Wastewater Reuse To Meet The Standard of Circulation Cooling Systems|url = http://www.wateronline.com/doc/cutting-edge-solutions-for-coking-wastewater-reuse-to-meet-the-standard-of-circulation-cooling-systems-0001|website = www.wateronline.com|access-date = 2016-01-16}}</ref> 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 that discharges ammonia into marine waters.<ref name="Rajaram-2005">{{cite book |author1=Vasudevan Rajaram |author2=Subijoy Dutta |author3=Krishna Parameswaran |title=Sustainable Mining Practices: A Global Perspective |url=https://books.google.com/books?id=5uTM2jFMzH4C&pg=PA113 |date=30 June 2005 |publisher=CRC Press |isbn=978-1-4398-3423-7 |page=113}}</ref>

=== Aquaculture ===
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.<ref name="Oram">{{Cite web|url = http://www.water-research.net/index.php/ammonia-in-groundwater-runoff-and-streams|title = Ammonia in Groundwater, Runoff, and Streams|access-date = 3 December 2014|website = The Water Centre|last = Oram|first = Brian}}</ref> At lower concentrations, around 0.05&nbsp;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.<ref>{{Cite book|title = Managing ammonia in fish ponds|last1 = Hargreaves|first1 = J.A.|publisher = Southern Regional Aquaculture Center|year = 2004|last2 = Tucker|first2 = C.S.}}</ref> Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate.<ref name="Oram" /> At concentrations exceeding 2.0&nbsp;mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death.<ref name="Oram" /><ref name="Sergeant-2014">{{Cite journal|url = http://www.pollutionsolutions-online.com/articles/water-wastewater/17/chris_sergeant/the_management_of_ammonia_levels_in_an_aquaculture_environment/1557/|title = The Management of Ammonia Levels in an Aquaculture Environment|last = Sergeant|first = Chris|date = 5 February 2014|journal = Water/Wastewater|access-date = 3 December 2014}}</ref> Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0&nbsp;mg/L.<ref name="Sergeant-2014" />

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<ref name="Sergeant-2014" /> 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.<ref>[http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr;sid=3a1341f81fbe762466a07d33da2361fb;rgn=div8;view=text;node=29%3A5.1.1.1.8.8.33.11;idno=29;cc=ecfr Electronic Code of Federal Regulations:] {{webarchive|url=https://web.archive.org/web/20111104165051/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr%3Bsid%3D3a1341f81fbe762466a07d33da2361fb%3Brgn%3Ddiv8%3Bview%3Dtext%3Bnode%3D29%3A5.1.1.1.8.8.33.11%3Bidno%3D29%3Bcc%3Decfr |date=4 November 2011 }}. Ecfr.gpoaccess.gov. Retrieved on 22 December 2011.</ref> Ammonia is used in numerous different industrial applications requiring carbon or stainless steel storage vessels. Ammonia with at least 0.2% by weight water content is not corrosive to carbon steel. {{NH3}} [[carbon steel]] construction storage tanks with 0.2% by weight or more of water could last more than 50 years in service.<ref>{{Cite web|title=Ammonia Tanks – Carbon and Stainless Steel Construction|url=https://ammoniatanks.com/|access-date=2021-06-28|website=ammoniatanks.com}}</ref> Experts warn that ammonium compounds not be allowed to come in contact with [[base (chemistry)|bases]] (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.

=== Laboratory ===
[[File:Ammonia solution (25-28%).jpg|thumb|155px|A standard laboratory solution of 28% ammonia]]
The hazards of ammonia solutions depend on the concentration: 'dilute' ammonia solutions are usually 5–10% by weight (<&nbsp;5.62&nbsp;mol/L); 'concentrated' solutions are usually prepared at >25% by weight. A 25% (by weight) solution has a density of 0.907&nbsp;g/cm<sup>3</sup>, and a solution that has a lower density will be more concentrated. The [[Directive 67/548/EEC|European Union classification]] of ammonia solutions is given in the table.

<!-- EU Index no. 007-001-01-2 -->
{| class="wikitable"
|-
! [[Concentration]]<br />by weight (w/w)
! [[Molarity]]
! [[Concentration]]<br />mass/volume (w/v)
! [[GHS pictograms]]
! [[H-phrases]]
|-
| 5–10%
| 2.87–5.62&nbsp;mol/L
| 48.9–95.7&nbsp;g/L
| {{GHS07}}
| {{H-phrases|314}}
|-
| 10–25%
| 5.62–13.29&nbsp;mol/L
| 95.7–226.3&nbsp;g/L
| {{GHS05}}{{GHS07}}
| {{H-phrases|314|335|400}}
|-
| >25%
| >13.29&nbsp;mol/L
| >226.3&nbsp;g/L
| {{GHS05}}{{GHS07}}{{GHS09}}
| {{H-phrases|314|335|400|411}}
|}

The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the [[respiratory tract]], and experts warn that these solutions only be handled in a [[fume hood]]. Saturated ('0.880'–see ''{{slink|#Properties}}'') solutions can develop a significant pressure inside a closed bottle in warm weather, and experts also warn that the bottle be opened with care. This is not usually a problem for 25% ('0.900') solutions.

Experts warn that ammonia solutions not be mixed with [[halogen]]s, as toxic and/or explosive products are formed. Experts also warn that prolonged contact of ammonia solutions with [[silver]], [[mercury (element)|mercury]] or [[iodide]] salts can also lead to explosive products: such mixtures are often formed in [[qualitative inorganic analysis]], and that it needs to be lightly acidified but not concentrated (<6%&nbsp;w/v) before disposal once the test is completed.

=== Laboratory use of anhydrous ammonia (gas or liquid) ===
<!-- EU index no. 007-001-00-5 -->
<!-- R10, 23, 34, 50; S1/2, 9, 16, 26, 36/37/39, 45, 61 -->
Anhydrous ammonia is classified as toxic ('''T''') and dangerous for the environment ('''N'''). The gas is flammable ([[autoignition temperature]]: 651&nbsp;°C) and can form explosive mixtures with air (16–25%). The [[permissible exposure limit]] (PEL) in the United States is 50&nbsp;[[Parts per million|ppm]] (35&nbsp;mg/m<sup>3</sup>), while the [[IDLH]] concentration is estimated at 300&nbsp;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&nbsp;ppm, but desensitised individuals may not detect it even at concentrations of 100&nbsp;ppm. Anhydrous ammonia corrodes [[copper]]- and [[zinc]]-containing [[alloy]]s, which makes [[brass]] fittings not appropriate for handling the gas. Liquid ammonia can also attack [[rubber]] and certain plastics.

Ammonia reacts violently with the [[halogen]]s. [[Nitrogen triiodide]], a [[primary explosive|primary]] [[high explosive]], is formed when ammonia comes in contact with [[iodine]]. Ammonia causes the explosive [[polymerisation]] of [[ethylene oxide]]. It also forms explosive [[Detonation|fulminating]] compounds with compounds of [[gold]], [[silver]], [[Mercury (element)|mercury]], [[germanium]] or [[tellurium]], and with [[stibine]]. Violent reactions have also been reported with [[acetaldehyde]], [[hypochlorite]] solutions, [[potassium ferricyanide]] and [[peroxide]]s.

== Production ==
{{about|section=true|industrial synthesis|synthesis in certain organisms|#Biosynthesis}}
{{Main|Ammonia production}}

{{Image frame  | content =
{{Graph:Chart
 | width=800
 | height=300
 | xAxisTitle=Year
 | yAxisTitle=World production in thousands of tons of fixed nitrogen
 | type=line
 |x=1950,1951,1952,1953,1954,1955,1956,1957,1958,1959,1960,1961,1962,1963,1964,1965,1966,1967,1968,1969,1970,1971,1972,1973,1974,1975,1976,1977,1978,1979,1980,1981,1982,1983,1984,1985,1986,1987,1988,1989,1990,1991,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2020
 |y1=4050,4890,5570,7300,7310,8030,8560,10810,11800,12870,13970,14810,17110,19360,21860,25000,28690,32140,35880,38780,41150,43000,46720,48440,49530,58970,61970,65830,69760,71370,76970,75870,78500,84390,90980,91570,94200,98300,99300,93700,94000,92500,91242,92000,91600,96000,101000,106000,108000,109000,106000,109000,109000,117000,121000,124000,131000,133000,130000,131000,135000,140000,143000,145000,141000,144000,142000,144000,142000,147000
|yGrid= |xGrid= 
}}
|caption = Global ammonia production 1950–2020 (expressed as fixed nitrogen in U.S. tons)<ref>{{cite web |title=Nitrogen Statistics and Information U.S. Geological Survey |url=https://www.usgs.gov/centers/national-minerals-information-center/nitrogen-statistics-and-information |website=www.usgs.gov |access-date=24 January 2023}}</ref>
}}

Ammonia has one of the highest rates of production of any inorganic chemical. Production is sometimes expressed in terms of 'fixed nitrogen'. Global production was estimated as being 160 million tonnes in 2020 (147 tons of fixed nitrogen).<ref name="U.S. National Minerals Information Center">{{cite web |title=Nitrogen (Fixed)--Ammonia (2022) |url=https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-nitrogen.pdf |website=U.S. National Minerals Information Center |access-date=24 January 2023}}</ref> China accounted for 26.5% of that, followed by Russia at 11.0%, the United States at 9.5%, and India at 8.3%.<ref name="U.S. National Minerals Information Center"/>

Before the start of [[World War I]], most ammonia was obtained by the [[dry distillation]]<ref>{{cite news|access-date=7 July 2009|url=http://nobelprize.org/chemistry/laureates/1918/press.html |title=Nobel Prize in Chemistry (1918) – Haber–Bosch process}}</ref> of nitrogenous vegetable and animal waste products, including [[camel]] [[manure|dung]], where it was [[distilled]] by the reduction of [[nitrous acid]] and [[nitrite]]s with hydrogen; in addition, it was produced by the distillation of [[coal]], and also by the decomposition of ammonium salts by [[Alkali hydroxide|alkaline hydroxides]]<ref>{{cite news|access-date=7 July 2009|title=Chemistry of the Group 2 Elements – Be, Mg, Ca, Sr, Ba, Ra|url=https://www.bbc.co.uk/dna/h2g2/A1002934|work= BBC.co.uk}}</ref> such as [[quicklime]]:{{sfn|Chisholm|1911|p=861}}
{{block indent| {{chem2|2 [NH4]Cl + 2 CaO → [[CaCl2]] + Ca(OH)2 + 2 NH3([[Gas|g]])}}}}

For small scale laboratory synthesis, one can heat [[urea]] and [[calcium hydroxide]] or [[sodium hydroxide]]:
{{block indent| {{chem2|(NH2)2CO + Ca(OH)2 → CaCO3 + 2 NH3}}}}

=== Haber–Bosch ===
{{excerpt|Haber–Bosch process}}

=== Electrochemical ===
The [[electrochemical]] synthesis of ammonia involves the reductive formation of [[lithium nitride]], which can be [[protonated]] to ammonia, given a [[proton]] source. The first use of this chemistry was reported in 1930, where lithium solutions in ethanol were used to produce ammonia at pressures of up to 1000&nbsp;bar, with ethanol acting as the proton source.<ref>{{Cite journal |last1=Fichter |first1=Fr. |last2=Girard |first2=Pierre |last3=Erlenmeyer |first3=Hans |date=1930-12-01 |title=Elektrolytische Bindung von komprimiertem Stickstoff bei gewöhnlicher Temperatur |url=https://onlinelibrary.wiley.com/doi/10.1002/hlca.19300130604 |journal=Helvetica Chimica Acta |language=en |volume=13 |issue=6 |pages=1228–1236 |doi=10.1002/hlca.19300130604}}</ref> Beyond simply mediating proton transfer to the nitrogen reduction reaction, ethanol has been found to play a multifaceted role, influencing electrolyte transformations and contributing to the formation of the solid electrolyte interphase, which enhances overall reaction efficiency<ref>{{Cite journal |last1=Bjarke Valbæk Mygind |first1=Jon |last2=Pedersen |first2=Jakob B. |last3=Li |first3=Katja |last4=Deissler |first4=Niklas H. |last5=Saccoccio |first5=Mattia |last6=Fu |first6=Xianbiao |last7=Li |first7=Shaofeng |last8=Sažinas |first8=Rokas |last9=Andersen |first9=Suzanne Z. |last10=Enemark-Rasmussen |first10=Kasper |last11=Vesborg |first11=Peter C. K. |last12=Doganli-Kibsgaard |first12=Jakob |last13=Chorkendorff |first13=Ib |date=2023-11-22 |title=Is Ethanol Essential for the Lithium-Mediated Nitrogen Reduction Reaction? |journal=ChemSusChem |language=en |volume=16 |issue=22 |pages=e202301011 |doi=10.1002/cssc.202301011 |pmid=37681646 |bibcode=2023ChSCh..16E1011B |issn=1864-5631|doi-access=free }}</ref><ref name="Lazouski-2019" /> 

In 1994, Tsuneto et al. used lithium electrodeposition in [[tetrahydrofuran]] to synthesize ammonia at more moderate pressures with reasonable [[Faradaic efficiency]].<ref>{{Cite journal |last1=Tsuneto |first1=Akira |last2=Kudo |first2=Akihiko |last3=Sakata |first3=Tadayoshi |date=1994-03-04 |title=Lithium-mediated electrochemical reduction of high pressure N2 to NH3 |url=https://dx.doi.org/10.1016/0022-0728%2893%2903025-K |journal=Journal of Electroanalytical Chemistry |language=en |volume=367 |issue=1 |pages=183–188 |doi=10.1016/0022-0728(93)03025-K |issn=1572-6657}}</ref> Subsequent studies have further explored the ethanol–tetrahydrofuran system for electrochemical ammonia synthesis.<ref name="Lazouski-2019">{{Cite journal |last1=Lazouski |first1=Nikifar |last2=Schiffer |first2=Zachary J. |last3=Williams |first3=Kindle |last4=Manthiram |first4=Karthish |date=2019-04-17 |title=Understanding Continuous Lithium-Mediated Electrochemical Nitrogen Reduction |journal=Joule |language=en |volume=3 |issue=4 |pages=1127–1139 |bibcode=2019Joule...3.1127L |doi=10.1016/j.joule.2019.02.003 |issn=2542-4351 |s2cid=107985507 |doi-access=free}}</ref><ref>{{Cite journal |last1=Andersen |first1=Suzanne Z. |last2=Čolić |first2=Viktor |last3=Yang |first3=Sungeun |last4=Schwalbe |first4=Jay A. |last5=Nielander |first5=Adam C. |last6=McEnaney |first6=Joshua M. |last7=Enemark-Rasmussen |first7=Kasper |last8=Baker |first8=Jon G. |last9=Singh |first9=Aayush R. |last10=Rohr |first10=Brian A. |last11=Statt |first11=Michael J. |date=June 2019 |title=A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements |url=https://www.nature.com/articles/s41586-019-1260-x |journal=Nature |language=en |volume=570 |issue=7762 |pages=504–508 |bibcode=2019Natur.570..504A |doi=10.1038/s41586-019-1260-x |issn=1476-4687 |pmid=31117118 |s2cid=162182383 |hdl-access=free |hdl=10044/1/72812}}</ref>

In 2020, a solvent-agnostic [[gas diffusion electrode]] was shown to improve nitrogen transport to the reactive lithium. {{chem2|NH3}} production rates of up to {{nobreak|30 ± 5 nmol/(s⋅cm<sup>2</sup>)}} and Faradaic efficiencies of up to 47.5 ± 4% at ambient temperature and 1&nbsp;bar pressure were achieved.<ref>{{Cite journal |last1=Lazouski |first1=Nikifar |last2=Chung |first2=Minju |last3=Williams |first3=Kindle |last4=Gala |first4=Michal L. |last5=Manthiram |first5=Karthish |date=2020-05-01 |title=Non-aqueous gas diffusion electrodes for rapid ammonia synthesis from nitrogen and water-splitting-derived hydrogen |url=https://www.nature.com/articles/s41929-020-0455-8 |journal=Nature Catalysis |language=en |volume=3 |issue=5 |pages=463–469 |doi=10.1038/s41929-020-0455-8 |s2cid=218495730 |issn=2520-1158}}</ref>

In 2021, it was demonstrated that ethanol could be replaced with a tetraalkyl [[phosphonium salt]].<ref name="Suryanto-2021">{{Cite journal|last1=Suryanto|first1=Bryan H. R.|last2=Matuszek|first2=Karolina|last3=Choi|first3=Jaecheol|last4=Hodgetts|first4=Rebecca Y.|last5=Du|first5=Hoang-Long|last6=Bakker|first6=Jacinta M.|last7=Kang|first7=Colin S. M.|last8=Cherepanov|first8=Pavel V.|last9=Simonov|first9=Alexandr N.|last10=MacFarlane|first10=Douglas R.|date=2021-06-11|title=Nitrogen reduction to ammonia at high efficiency and rates based on a phosphonium proton shuttle|url=https://www.science.org/doi/10.1126/science.abg2371|url-access=registration|journal=Science|language=en|volume=372|issue=6547|pages=1187–1191|doi=10.1126/science.abg2371|issn=0036-8075|pmid=34112690|bibcode=2021Sci...372.1187S|s2cid=235396282}}</ref> The study observed {{chem2|NH3}} production rates of {{nobreak|53 ± 1 nmol/(s⋅cm<sup>2</sup>)}} at 69 ± 1% Faradaic efficiency experiments under 0.5&nbsp;bar hydrogen and 19.5&nbsp;bar nitrogen [[partial pressure]] at ambient temperature.<ref name="Suryanto-2021"/> Technology based on this electrochemistry is being developed for commercial fertiliser and fuel production.<ref>{{Cite web|last=Lavars|first=Nick|date=2021-11-30|title=Green ammonia electrolysis breakthrough could finally kill Haber–Bosch|url=https://newatlas.com/energy/green-ammonia-phosphonium-production/|url-status=live|access-date=2021-12-03|website=New Atlas|language=en-US|archive-url=https://web.archive.org/web/20211130072137/https://newatlas.com/energy/green-ammonia-phosphonium-production/ |archive-date=30 November 2021 }}</ref><ref>{{Cite web|last=Blaine|first=Loz|date=2021-11-19|title=FuelPositive promises green ammonia at 60% the cost of today's gray|url=https://newatlas.com/energy/fuelpositive-green-ammonia/|url-status=live|access-date=2021-12-03|website=New Atlas|language=en-US|archive-url=https://web.archive.org/web/20211119060353/https://newatlas.com/energy/fuelpositive-green-ammonia/ |archive-date=19 November 2021 }}</ref>

In 2022, ammonia was produced via the lithium mediated process in a continuous-flow electrolyzer also demonstrating the hydrogen gas as proton source. The study synthesized ammonia at 61 ± 1% Faradaic efficiency at a current density of −6 mA/cm<sup>2</sup> at 1&nbsp;bar and room temperature.<ref name="Fu-2022">{{Cite journal| last1=Fu|first1=Xianbiao| last2=Pedersen|first2=Jakob B.| last3=Zhou|first3=Yuanyuan| last4=Saccoccio|first4=Mattia| last5=Li|first5=Shaofeng| last6=Sažinas|first6=Rokas| last7=Li|first7=Katja| last8=Andersen|first8=Suzanne Z.| last9=Xu|first9=Aoni| last10=Deissler|first10=Niklas H.| last11=Mygind|first11=Jon Bjarke Valbæk| last12=Wei|first12=Chao| last13=Kibsgaard|first13=Jakob| last14=Vesborg|first14=Peter C. K.| last15=Nørskov|first15=Jens K.| last16=Chorkendorff|first16=Ib| date=2022-02-16|title=Continuous-flow electrosynthesis of ammonia by nitrogen reduction and hydrogen oxidation|url=https://www.science.org/doi/10.1126/science.adf4403|journal=Science|language=en|volume=379|issue=6633|pages=707–712|doi=10.1126/science.adf4403|issn=|pmid=36795804|bibcode=|s2cid=}}</ref>

== Biochemistry and medicine ==
[[File:Symptoms of hyperammonemia.svg|thumb|upright=1.15|Main symptoms of hyperammonemia (ammonia reaching toxic concentrations).<ref>{{cite news|url=http://emedicine.medscape.com/article/944996-overview |title=eMedicine Specialties > Metabolic Diseases > Hyperammonemia|author= Roth, Karl S. |access-date=7 July 2009}}</ref>]]
Ammonia is essential for life.<ref>{{cite journal |title=Biochemistry, Ammonia |url=https://www.ncbi.nlm.nih.gov/books/NBK541039/#:~:text=Ammonia%20is%20loaded%20via%20glutamine,low%20concentrations%20in%20the%20liver. |website=StatPearls | date=2023 |publisher=Treasure Island| pmid=31082083 | last1=Mohiuddin | first1=S. S. | last2=Khattar | first2=D. }}</ref> For example, it is required for the formation of [[amino acid]]s and [[nucleic acid]]s, fundamental building blocks of life. Ammonia is however quite toxic. Nature thus uses carriers for ammonia. Within a cell, [[glutamate]] serves this role. In the bloodstream, [[glutamine]] is a source of ammonia.<ref>{{Lehninger4th|page=632-633}}</ref>

Ethanolamine, required for cell membranes, is the substrate for [[ethanolamine ammonia-lyase]], which produces ammonia:<ref>{{cite journal |doi=10.1074/jbc.M110.125112 |doi-access=free |title=Crystal Structures of Ethanolamine Ammonia-lyase Complexed with Coenzyme B12 Analogs and Substrates |date=2010 |last1=Shibata |first1=Naoki |last2=Tamagaki |first2=Hiroko |last3=Hieda |first3=Naoki |last4=Akita |first4=Keita |last5=Komori |first5=Hirofumi |last6=Shomura |first6=Yasuhito |last7=Terawaki |first7=Shin-Ichi |last8=Mori |first8=Koichi |last9=Yasuoka |first9=Noritake |last10=Higuchi |first10=Yoshiki |last11=Toraya |first11=Tetsuo |journal=Journal of Biological Chemistry |volume=285 |issue=34 |pages=26484–26493 |pmid=20519496 |pmc=2924083 }}</ref>
{{block indent|{{chem2|H2NCH2CH2OH  ->  NH3  +  CH3CHO}}}}

Ammonia is both a [[metabolic waste]] and a metabolic input throughout the [[biosphere]]. It is an important source of nitrogen for living systems. Although atmospheric nitrogen abounds (more than 75%), few living creatures are capable of using atmospheric nitrogen in its [[diatomic]] form, {{chem2|N2}} gas. Therefore, [[nitrogen fixation]] is required for the synthesis of amino acids, which are the building blocks of [[protein]]. Some plants rely on ammonia and other nitrogenous wastes incorporated into the soil by decaying matter. Others, such as nitrogen-fixing [[legume]]s, benefit from [[symbiotic]] relationships with [[rhizobia]] bacteria that create ammonia from atmospheric nitrogen.<ref>{{cite web|author1=Adjei, M. B. |author2=Quesenberry, K. H. |author3=Chamblis, C. G. |title=Nitrogen Fixation and Inoculation of Forage Legumes|url=http://edis.ifas.ufl.edu/AG152 |archive-url=https://web.archive.org/web/20070520075000/http://edis.ifas.ufl.edu/AG152 |archive-date=20 May 2007 |publisher=University of Florida IFAS Extension|date=June 2002}}</ref>

In humans, inhaling ammonia in high concentrations can be fatal. Exposure to ammonia can cause [[headaches]], [[edema]], impaired memory, [[seizures]] and [[coma]] as it is [[neurotoxic]] in nature.<ref>Identifying the direct effects of ammonia on the brain – PubMed</ref>

=== Biosynthesis ===
In certain organisms, ammonia is produced from atmospheric nitrogen by [[enzyme]]s called [[nitrogenase]]s. The overall process is called [[nitrogen fixation]]. Intense effort has been directed toward understanding the mechanism of biological nitrogen fixation. The scientific interest in this problem is motivated by the unusual structure of the [[active site]] of the enzyme, which consists of an {{chem2|Fe7MoS9}} ensemble.<ref>{{cite journal|last1=Igarashi|first1=Robert Y.|last2=Laryukhin|first2=Mikhail|last3=Dos Santos|first3=Patricia C.|last4=Lee|first4=Hong-In|last5=Dean|first5=Dennis R.|last6=Seefeldt|first6=Lance C.|last7=Hoffman|first7=Brian M.|title=Trapping H- Bound to the Nitrogenase FeMo-Cofactor Active Site during H2 Evolution: Characterization by ENDOR Spectroscopy|journal=Journal of the American Chemical Society|date=May 2005|volume=127|issue=17|pages=6231–6241|doi=10.1021/ja043596p|pmid=15853328|bibcode=2005JAChS.127.6231I }}</ref>

Ammonia is also a metabolic product of [[amino acid]] [[deamination]] catalyzed by enzymes such as [[Glutamate dehydrogenase 1#Function|glutamate dehydrogenase 1]]. Ammonia excretion is common in aquatic animals. In humans, it is quickly converted to [[urea]] (by [[liver]]), which is much less toxic, particularly less [[#Basicity|basic]]. This urea is a major component of the dry weight of [[urine]]. Most reptiles, birds, insects, and snails excrete [[uric acid]] solely as nitrogenous waste.

=== Physiology ===
Ammonia plays a role in both normal and abnormal animal [[physiology]]. It is [[biosynthesis]]ed through normal amino acid metabolism and is toxic in high concentrations. The [[liver]] converts ammonia to [[urea]] through a series of reactions known as the [[urea cycle]]. Liver dysfunction, such as that seen in [[cirrhosis]], may lead to elevated amounts of ammonia in the blood ([[hyperammonemia]]). Likewise, defects in the enzymes responsible for the urea cycle, such as [[ornithine transcarbamylase]], lead to [[hyperammonemia]]. Hyperammonemia contributes to the confusion and [[coma]] of [[hepatic encephalopathy]], as well as the neurological disease common in people with urea cycle defects and [[organic aciduria]]s.<ref>{{cite book|author1=Zschocke, Johannes |author2=Hoffman, Georg |title=Vademecum Metabolism|publisher= Schattauer Verlag|year= 2004|isbn=978-3794523856}}</ref>

Ammonia is important for normal animal acid/base balance. After formation of ammonium from [[glutamine]], [[α-ketoglutarate]] may be degraded to produce two [[bicarbonate]] ions, which are then available as buffers for dietary acids. Ammonium is excreted in the urine, resulting in net acid loss. Ammonia may itself diffuse across the [[Nephron|renal tubules]], combine with a hydrogen ion, and thus allow for further acid [[excretion]].<ref>{{cite book|author1=Rose, Burton|author2=Helmut Rennke|title=Renal Pathophysiology|location=Baltimore|publisher=Williams & Wilkins|year=1994|isbn=978-0-683-07354-6|url=https://archive.org/details/renalpathophysio0000rose}}</ref>

=== Excretion ===
{{Main|Excretion}}
Ammonium ions are a [[toxic]] waste product of [[metabolism]] in [[animal]]s. In fish and aquatic invertebrates, it is excreted directly into the water. In mammals, sharks, and amphibians, it is converted in the [[urea cycle]] to [[urea]], which is less toxic and can be stored more efficiently. In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into [[uric acid]], which is solid and can therefore be excreted with minimal water loss.<ref>{{cite book |last=Campbell |first=Neil A. |author-link=Neil Campbell (scientist) |author2=Jane B. Reece |title=Biology |edition=6th |year=2002 |publisher=Pearson Education, Inc |location=San Francisco |isbn=978-0-8053-6624-2 |pages=[https://archive.org/details/biologyc00camp/page/937 937–938] |chapter=44 |author2-link=Jane Reece |chapter-url=https://archive.org/details/biologyc00camp |url=https://archive.org/details/biologyc00camp/page/937 }}</ref>

== Extraterrestrial occurrence ==
[[File:Jupiter.jpg|thumb|Ammonia occurs in the [[celestial body atmosphere|atmospheres]] of the outer giant planets such as [[Jupiter]] (0.026% ammonia), [[Saturn]] (0.012% ammonia), and in the atmospheres and [[Ice giant|ices]] of [[Uranus]] and [[Neptune]].]]
Ammonia has been detected in the atmospheres of the [[giant planet]]s [[Jupiter]], [[Saturn]], [[Uranus]] and [[Neptune]], along with other gases such as [[methane]], [[hydrogen]], and [[helium]]. The interior of [[Saturn]] may include frozen ammonia crystals.<ref>Edited by Kirk Munsell. Image page credit Lunar and Planetary Institute. NASA. "[http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=166 NASA's Solar Exploration: Multimedia: Gallery: Gas Giant Interiors] {{Webarchive|url=https://web.archive.org/web/20060220100208/http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=166 |date=20 February 2006 }}". Retrieved 26 April 2006.</ref> It is found on [[Deimos (moon)|Deimos]] and [[Phobos (moon)|Phobos]]–the two [[moons of Mars]].{{citation needed|date=March 2024}}

=== Interstellar space ===
Ammonia was first detected in interstellar space in 1968, based on [[microwave]] emissions from the direction of the [[Milky Way|galactic core]].<ref>{{cite journal|author1=Cheung, A. C. |author2=Rank, D. M. |author3=Townes, C. H. |author4=Thornton, D. D. |author5=Welch, W. J. |year= 1968|title=Detection of NH<sub>3</sub> molecules in the interstellar medium by their microwave emission|journal=Phys. Rev. Lett.|volume=21|issue=25|page=1701|doi=10.1103/PhysRevLett.21.1701|bibcode=1968PhRvL..21.1701C}}</ref> This was the first [[polyatomic]] molecule to be so detected. The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of the most important molecules for studies of [[molecular cloud]]s.<ref name="Ho-1983">{{cite journal|author1=Ho, P. T. P. |author2=Townes, C. H.|year= 1983|title=Interstellar ammonia|bibcode=1983ARA&A..21..239H|journal=Annu. Rev. Astron. Astrophys.|volume= 21|issue=1|pages=239–70|doi=10.1146/annurev.aa.21.090183.001323}}</ref> The relative intensity of the ammonia lines can be used to measure the temperature of the emitting medium.

The following isotopic species of ammonia have been detected: {{chem2|NH3}},{{chem2|^{15}NH3}}, {{chem2|NH2[[Deuterium|D]]}}, {{chem2|NHD2}}, and {{chem2|ND3}}. The detection of triply [[deuterium|deuterated]] ammonia was considered a surprise as deuterium is relatively scarce. It is thought that the low-temperature conditions allow this molecule to survive and accumulate.<ref>{{cite journal|author=Millar, T. J.|s2cid=189793190|title=Deuterium Fractionation in Interstellar Clouds|journal=Space Science Reviews|volume= 106|issue=1|pages=73–86|doi=10.1023/A:1024677318645|year=2003|bibcode = 2003SSRv..106...73M }}</ref>

Since its interstellar discovery, {{chem2|NH3}} has proved to be an invaluable spectroscopic tool in the study of the interstellar medium. With a large number of transitions sensitive to a wide range of excitation conditions, {{chem2|NH3}} has been widely astronomically detected–its detection has been reported in hundreds of journal articles. Listed below is a sample of journal articles that highlights the range of detectors that have been used to identify ammonia.

The study of interstellar ammonia has been important to a number of areas of research in the last few decades. Some of these are delineated below and primarily involve using ammonia as an interstellar thermometer.

==== Interstellar formation mechanisms ====
The interstellar abundance for ammonia has been measured for a variety of environments. The [{{chem2|NH3}}]/[{{chem2|H2}}] ratio has been estimated to range from 10<sup>−7</sup> in small dark clouds<ref>{{cite journal|author=Ungerechts, H. |author2=Walmsley, C. M. |author3=Winnewisser, G. |journal=Astron. Astrophys.|volume=88|page=259|year=1980|title=Ammonia and cyanoacetylene observations of the high-density core of L-183 (L-134-N)|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-journal_query?volume=88&plate_select=NO&page=259&plate=&cover=&journal=A%2BA..|bibcode = 1980A&A....88..259U }}</ref> up to 10<sup>−5</sup> in the dense core of the [[Orion molecular cloud complex]].<ref>{{cite journal|author1=Genzel, R. |author2=Downes, D. |author3=Ho, P. T. P. |year=1982|journal=Astrophysical Journal|volume=259|page=L103|doi=10.1086/183856|title=NH<sub>3</sub> in Orion-KL – A new interpretation|bibcode=1982ApJ...259L.103G}}</ref> Although a total of 18 total production routes have been proposed,<ref>{{cite web|url=http://udfa.net/|title=The UMIST data for Astrochemistry|access-date=7 July 2009}}</ref> the principal formation mechanism for interstellar {{chem2|NH3}} is the reaction:
{{block indent| {{chem2|[NH4]+ + e− → NH3 + H}}}}

The rate constant, ''k'', of this reaction depends on the temperature of the environment, with a value of <math>5.2\times 10^{-6}</math> at 10&nbsp;K.<ref>{{cite journal|author=Vikor, L.|year=1999|journal=Astronomy and Astrophysics|volume=344|page=1027|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-journal_query?volume=344&plate_select=NO&page=1027&plate=&cover=&journal=A%2BA..|title=Branching fractions of dissociative recombination of NH4+ and NH2+ molecular ions|bibcode = 1999A&A...344.1027V|last2=Al-Khalili|first2=A.|last3=Danared|first3=H.|last4=Djuric|first4=N.|last5=Dunn|first5=G. H.|last6=Larsson|first6=M.|last7=Le Padellec|first7=A.|last8=Rosen|first8=S.|last9=Af Ugglas|first9=M.}}</ref> The rate constant was calculated from the formula {{tmath|1=k = a(T/300)^B}}. For the primary formation reaction, {{math|1=''a''&nbsp;=&nbsp;{{val|1.05e−6}}}} and {{math|1=''B'' = −0.47}}. Assuming an {{chem2|NH4+}} abundance of <math>3\times 10^{-7}</math>and an electron abundance of 10<sup>−7</sup> typical of molecular clouds, the formation will proceed at a rate of {{val|1.6e−9|u=cm<sup>−3</sup>s<sup>−1</sup>}} in a molecular cloud of total density {{val|e=5|u=cm<sup>−3</sup>}}.<ref>{{cite journal|author1=van Dishoeck, E. F. |author2=Black, J. H.|year=1986|journal=Astrophys. J. Suppl. Ser.|volume=62|pages=109–145|doi=10.1086/191135|title=Comprehensive models of diffuse interstellar clouds – Physical conditions and molecular abundances|bibcode=1986ApJS...62..109V|hdl=1887/1980|url=https://openaccess.leidenuniv.nl/bitstream/handle/1887/1980/8_352_018.pdf?sequence=1|hdl-access=free}}</ref>

All other proposed formation reactions have rate constants of between two and 13 orders of magnitude smaller, making their contribution to the abundance of ammonia relatively insignificant.<ref>{{cite web|url=http://astrochemistry.net |title=astrochemistry.net |publisher=astrochemistry.net |access-date=21 May 2011}}</ref> As an example of the minor contribution other formation reactions play, the reaction:
{{block indent| {{chem2|H2 + NH2 → NH3 + H}}}}
has a rate constant of 2.2{{e|−15}}. Assuming {{chem2|H2}} densities of 10<sup>5</sup> and [{{chem2|NH2}}]/[{{chem2|H2}}] ratio of 10<sup>−7</sup>, this reaction proceeds at a rate of 2.2{{e|−12}}, more than three orders of magnitude slower than the primary reaction above.

Some of the other possible formation reactions are:
{{block indent| {{chem2|H− + [NH4]+ → NH3 + H2}}}}
{{block indent| {{chem2|[PNH3]+ + e− → P + NH3}}}}

==== Interstellar destruction mechanisms ====
There are 113 total proposed reactions leading to the destruction of {{chem2|NH3}}. Of these, 39 were tabulated in extensive tables of the chemistry among C, N and O compounds.<ref>{{cite journal|bibcode=1980ApJS...43....1P|author1=Prasad, S. S. |author2=Huntress, W. T. |title=A model for gas phase chemistry in interstellar clouds|year=1980|journal=The Astrophysical Journal Supplement Series |volume=43|page=1 | doi=10.1086/190665|doi-access=free}}</ref> A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms:<ref name="Ho-1983"/>

{{NumBlk|:| {{chem2|NH3 + [H3]+ → [NH4]+ + H2}}|{{EquationRef|1}}}}
{{NumBlk|:| {{chem2|NH3 + HCO+ → [NH4]+ + CO}}|{{EquationRef|2}}}}

with rate constants of 4.39×10<sup>−9</sup><ref>{{cite journal|author1=Lininger, W. |author2=Albritton, D. L. |author3=Fehsenfeld, F. C. |author4=Schmeltekopf, A. L. |author5=Ferguson, E. E. |journal= J. Chem. Phys.|volume=62|page=3549|year=1975|bibcode = 1975JChPh..62.3549L |doi = 10.1063/1.430946|title=Flow–drift tube measurements of kinetic energy dependences of some exothermic proton transfer rate constants|issue=9 }}</ref> and 2.2×10<sup>−9</sup>,<ref>{{cite journal|doi=10.1016/0009-2614(77)85326-8|title=Reactions of CH<sup>+</sup><sub>n</sub> IONS with ammonia at 300&nbsp;K|year=1977|author=Smith, D.|journal=Chemical Physics Letters|volume=47|issue=1|page=145|first2=N. G.|last2=Adams|bibcode = 1977CPL....47..145S }}</ref> respectively. The above equations ({{EquationNote|1}}, {{EquationNote|2}}) run at a rate of 8.8×10<sup>−9</sup> and 4.4×10<sup>−13</sup>, respectively. These calculations assumed the given rate constants and abundances of [{{chem2|NH3}}]/[{{chem2|H2}}] = 10<sup>−5</sup>, [{{chem2|[H3]+}}]/[{{chem2|H2}}] = 2×10<sup>−5</sup>, [{{chem2|HCO+}}]/[{{chem2|H2}}] = 2×10<sup>−9</sup>, and total densities of ''n'' = 10<sup>5</sup>, typical of cold, dense, molecular clouds.<ref>{{cite journal|author1=Wooten, A. |author2=Bozyan, E. P. |author3=Garrett, D. B. |year=1980|journal=Astrophysical Journal|title=Detection of C<sub>2</sub>H in cold dark clouds|bibcode=1980ApJ...239..844W|volume=239|page=844|doi=10.1086/158168}}</ref> Clearly, between these two primary reactions, equation ({{EquationNote|1}}) is the dominant destruction reaction, with a rate ≈10,000 times faster than equation ({{EquationNote|2}}). This is due to the relatively high abundance of {{chem2|[H3]+}}.

==== Single antenna detections ====
Radio observations of {{chem2|NH3}} from the [[Effelsberg 100-m Radio Telescope]] reveal that the ammonia line is separated into two components–a background ridge and an unresolved core. The background corresponds well with the locations previously detected CO.<ref>{{cite journal|author=Wilson, T. L. |author2=Downes, D. |author3=Bieging, J. |year=1979|journal= Astronomy and Astrophysics|volume= 71|issue=3 |page= 275 |bibcode=1979A&A....71..275W|title=Ammonia in Orion }}</ref> The 25&nbsp;m [[Chilbolton Observatory|Chilbolton telescope]] in [[England]] detected radio signatures of ammonia in [[H II region]]s, HNH<sub>2</sub>O [[maser]]s, H–H objects, and other objects associated with star formation. A comparison of emission line widths indicates that turbulent or systematic velocities do not increase in the central cores of molecular clouds.<ref>{{cite journal|author=MacDonald, G. H. |author2=Little, L. T. |author3=Brown, A. T. |author4=Riley, P. W. |author5=Matheson, D. N. |author6=Felli, M. |year=1981|journal= MNRAS|volume= 195|issue=2 |page= 387 |bibcode=1981MNRAS.195..387M|title=Detection of new ammonia sources |doi=10.1093/mnras/195.2.387 |doi-access=free }}</ref>

Microwave radiation from ammonia was observed in several galactic objects including W3(OH), [[Orion (constellation)|Orion A]], [[Westerhout 43|W43]], [[Westerhout 51|W51]], and five sources in the galactic centre. The high detection rate indicates that this is a common molecule in the interstellar medium and that high-density regions are common in the galaxy.<ref>{{cite journal|author1=Morris, M. |author2=Zuckerman, B. |author3=Palmer, P. |author4=Turner, B. E. |year=1973|journal= Astrophysical Journal|volume= 186|page= 501 |bibcode=1973ApJ...186..501M|doi=10.1086/152515|title=Interstellar ammonia}}</ref>

==== Interferometric studies ====
[[Very Large Array|VLA]] observations of {{chem2|NH3}} in seven regions with high-velocity gaseous outflows revealed condensations of less than 0.1&nbsp;[[Parsec|pc]] in L1551, S140, and [[Cepheus (constellation)|Cepheus A]]. Three individual condensations were detected in Cepheus A, one of them with a highly elongated shape. They may play an important role in creating the bipolar outflow in the region.<ref>{{cite journal|author1=Torrelles, J. M. |author2=Ho, P. T. P. |author3=Rodriguez, L. F. |author4=Canto, J. |year=1985|journal= Astrophysical Journal|volume= 288|page= 595 |bibcode=1985ApJ...288..595T|doi=10.1086/162825|title=VLA observations of ammonia and continuum in regions with high-velocity gaseous outflows|s2cid=123014355 }}</ref>

Extragalactic ammonia was imaged using the VLA in [[IC 342]]. The hot gas has temperatures above 70&nbsp;K, which was inferred from ammonia line ratios and appears to be closely associated with the innermost portions of the nuclear bar seen in CO.<ref>{{cite journal|author1=Ho, P. T. P. |author2=Martin, R. N. |author3=Turner, J. L. |author4=Jackson, J. M. |year=1990|journal= Astrophysical Journal Letters|volume= 355|page= L19 |bibcode=1990ApJ...355L..19H|doi=10.1086/185728|title=VLA imaging of extragalactic ammonia – Hot gas in the nucleus of IC 342|doi-access=free}}</ref> {{chem2|NH3}} was also monitored by VLA toward a sample of four galactic ultracompact HII regions: G9.62+0.19, G10.47+0.03, G29.96-0.02, and G31.41+0.31. Based upon temperature and density diagnostics, it is concluded that in general such clumps are probably the sites of massive star formation in an early evolutionary phase prior to the development of an ultracompact HII region.<ref>{{cite journal|author1=Cesaroni, R. |author2=Churchwell, E. |author3=Hofner, P. |author4=Walmsley, C. M. |author5=Kurtz, S. |year=1994|journal= Astronomy and Astrophysics|volume= 288|page= 903 |bibcode=1994A&A...288..903C|title=Hot ammonia toward compact HII regions }}</ref>

==== Infrared detections ====
Absorption at 2.97 micrometres due to solid ammonia was recorded from interstellar grains in the [[Becklin–Neugebauer Object]] and probably in NGC 2264-IR as well. This detection helped explain the physical shape of previously poorly understood and related ice absorption lines.<ref>{{cite journal|author1=Knacke, R. F. |author2=McCorkle, S. |author3=Puetter, R. C. |author4=Erickson, E. F. |author5=Kraetschmer, W. |year=1982|journal= Astrophysical Journal|volume= 260|page= 141|bibcode=1982ApJ...260..141K|doi=10.1086/160241|title=Observation of interstellar ammonia ice|doi-access=free}}</ref>

A spectrum of the disk of Jupiter was obtained from the [[Kuiper Airborne Observatory]], covering the 100 to 300&nbsp;cm<sup>−1</sup> spectral range. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze.<ref>{{cite journal|author1=Orton, G. S. |author2=Aumann, H. H. |author3=Martonchik, J. V. |author4=Appleby, J. F. |year=1982|journal= Icarus|volume= 52|issue=1|page= 81 |bibcode=1982Icar...52...81O|doi=10.1016/0019-1035(82)90170-1|title=Airborne spectroscopy of Jupiter in the 100- to 300-cm<sup>−1</sup> region: Global properties of ammonia gas and ice haze}}</ref>

A total of 149 dark cloud positions were surveyed for evidence of 'dense cores' by using the (J,K) = (1,1) rotating inversion line of NH<sub>3</sub>. In general, the cores are not spherically shaped, with aspect ratios ranging from 1.1 to 4.4. It is also found that cores with stars have broader lines than cores without stars.<ref>{{cite journal|author=Benson, P. J. |author2=Myers, P. |year=1989|journal= Astrophysical Journal Supplement Series|volume= 71|page= 89 |bibcode=1989ApJS...71...89B|doi=10.1086/191365|title=A survey for dense cores in dark clouds|doi-access=free}}</ref>

Ammonia has been detected in the [[Draco (constellation)|Draco Nebula]] and in one or possibly two molecular clouds, which are associated with the high-latitude galactic [[infrared cirrus]]. The finding is significant because they may represent the birthplaces for the Population I metallicity B-type stars in the galactic halo that could have been borne in the galactic disk.<ref>{{cite journal|author1=Mebold, U. |author2=Heithausen, A. |author3=Reif, K.|year= 1987|journal= Astronomy and Astrophysics|volume= 180|page= 213|bibcode=1987A&A...180..213M|title=Ammonia in the galactic halo and the infrared cirrus }}</ref>

==== Observations of nearby dark clouds ====
By balancing and stimulated emission with spontaneous emission, it is possible to construct a relation between [[excitation temperature]] and density. Moreover, since the transitional levels of ammonia can be approximated by a 2-level system at low temperatures, this calculation is fairly simple. This premise can be applied to dark clouds, regions suspected of having extremely low temperatures and possible sites for future star formation. Detections of ammonia in dark clouds show very narrow lines{{snd}}indicative not only of low temperatures, but also of a low level of inner-cloud turbulence. Line ratio calculations provide a measurement of cloud temperature that is independent of previous CO observations. The ammonia observations were consistent with CO measurements of rotation temperatures of ≈10&nbsp;K. With this, densities can be determined, and have been calculated to range between 10<sup>4</sup> and 10<sup>5</sup>&nbsp;cm<sup>−3</sup> in dark clouds. Mapping of {{chem2|NH3}} gives typical clouds sizes of 0.1&nbsp;[[Parsec|pc]] and masses near 1 solar mass. These cold, dense cores are the sites of future star formation.

==== UC HII regions ====
Ultra-compact HII regions are among the best tracers of high-mass star formation. The dense material surrounding UCHII regions is likely primarily molecular. Since a complete study of massive star formation necessarily involves the cloud from which the star formed, ammonia is an invaluable tool in understanding this surrounding molecular material. Since this molecular material can be spatially resolved, it is possible to constrain the heating/ionising sources, temperatures, masses, and sizes of the regions. Doppler-shifted velocity components allow for the separation of distinct regions of molecular gas that can trace outflows and hot cores originating from forming stars.

==== Extragalactic detection ====
Ammonia has been detected in external galaxies,<ref>{{Cite journal |bibcode = 1979A&A....74L...7M|title = Detection of extragalactic ammonia|journal = Astronomy and Astrophysics|volume = 74|issue = 1|pages = L7|last1 = Martin|first1 = R. N.|last2 = Ho|first2 = P. T. P.|year = 1979}}</ref><ref>{{cite journal|title=Observations of Ammonia in External Galaxies I. NGC 253 and M 82|first1=S.|last1=Takano|first2=N.|last2=Nakai|first3=K.|last3=Kawaguchi|date=1 April 2002|journal=Publications of the Astronomical Society of Japan|volume=54|issue=2|pages=195–207|doi=10.1093/pasj/54.2.195|bibcode=2002PASJ...54..195T|doi-access=free}}</ref> and by simultaneously measuring several lines, it is possible to directly measure the gas temperature in these galaxies. Line ratios imply that gas temperatures are warm (≈50&nbsp;K), originating from dense clouds with sizes of tens of parsecs. This picture is consistent with the picture within our [[Milky Way]] galaxy{{snd}}hot dense molecular cores form around newly forming stars embedded in larger clouds of molecular material on the scale of several hundred parsecs (giant molecular clouds; GMCs).

== See also ==
{{Portal|Chemistry}}
* {{annotated link|Ammonia (data page)}}
* {{annotated link|Ammonia fountain}}
* {{annotated link|Ammonia production}}
* {{annotated link|Ammonia solution}}
* {{annotated link|Cost of electricity by source}}
* {{annotated link|Forming gas}}
* {{annotated link|Haber process}}
* {{annotated link|Hydrazine}}
* {{annotated link|Water purification}}

== References ==
{{reflist}}

=== Works cited ===
* {{cite web |title=Aqua Ammonia |url=http://www.airgasspecialtyproducts.com/Libraries/Aqua_Ammonia_Technical_Data_Manual/Physical_Properties.sflb.ashx |publisher=airgasspecialtyproducts.com |access-date=28 November 2010 |archive-url=https://web.archive.org/web/20101119084300/http://airgasspecialtyproducts.com/Libraries/Aqua_Ammonia_Technical_Data_Manual/Physical_Properties.sflb.ashx |archive-date=19 November 2010 |url-status=dead}}
* {{EB1911|wstitle=Ammonia|volume=1|pages=861–863}}
* {{cite web |url=https://chemguide.co.uk/physical/equilibria/haber.html |title=The Haber Process |last=Clark |first=Jim |date= April 2013 |orig-year= 2002 |language= en |access-date= 15 December 2018 }}

== Further reading ==
* {{cite book|editor=Bretherick, L.|title=Hazards in the Chemical Laboratory|edition=4th|location=London|publisher=Royal Society of Chemistry|year=1986|isbn=978-0-85186-489-1|oclc=16985764|url-access=registration|url=https://archive.org/details/hazardsinchemica0004unse}}
* {{Greenwood&Earnshaw2nd}}
* {{Housecroft1st}}
* {{RubberBible53rd}}
*{{Cite encyclopedia |title=Ammonia |encyclopedia=Encyclopedia of Liquid Fuels |publisher=De Gruyter |last=Schmidt |first=Eckart W. |date=2022 |pages=703–844 |doi=10.1515/9783110750287-008 |isbn=978-3-11-075028-7}}

== External links ==
{{Commons category|Ammonia}}
* [http://www.inchem.org/documents/icsc/icsc/eics0414.htm International Chemical Safety Card 0414] (anhydrous ammonia), ilo.org.
* [http://www.inchem.org/documents/icsc/icsc/eics0215.htm International Chemical Safety Card 0215] (aqueous solutions), ilo.org.
* {{PubChem|222}}
* {{cite web|url=http://www.inrs.fr/fichetox/ft16.html |title=Ammoniac et solutions aqueuses |publisher=Institut National de Recherche et de Sécurité |language=fr |url-status=dead |archive-url=https://web.archive.org/web/20101211115518/http://www.inrs.fr/fichetox/ft16.html |archive-date=11 December 2010 }}
* [http://www.ammoniaspills.org/ Emergency Response to Ammonia Fertiliser Releases (Spills)] for the Minnesota Department of Agriculture.ammoniaspills.org
* [https://www.cdc.gov/niosh/topics/ammonia National Institute for Occupational Safety and Health–Ammonia Page], cdc.gov
* [https://www.cdc.gov/niosh/npg/npgd0028.html NIOSH Pocket Guide to Chemical Hazards–Ammonia], cdc.gov
* [https://web.archive.org/web/20151030194722/http://www.mozalearn.com/Extra-Videos-Ammonia_NH3-210353 Ammonia, video]

{{Nitrogen compounds}}
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