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Nitrous oxide is also an [[Air pollution|atmospheric pollutant]], with a concentration of 333 [[Parts-per notation|parts per billion]] (ppb) in 2020, increasing at 1 ppb annually.<ref name="agage" /><ref name="noaaesrl" /> It is a major scavenger of [[ozone layer|stratospheric ozone]], with an impact comparable to that of [[chlorofluorocarbon|CFCs]].<ref name="sciozo"/> About 40% of human-caused emissions are [[Greenhouse gas emissions from agriculture#Nitrous oxide emissions|from agriculture]],<ref name="HTian">{{cite journal |last1=Tian |first1=Hanqin |last2=Xu |first2=Rongting |last3=Canadell |first3=Josep G. |last4=Thompson |first4=Rona L. |last5=Winiwarter |first5=Wilfried |last6=Suntharalingam |first6=Parvadha |last7=Davidson |first7=Eric A. |last8=Ciais |first8=Philippe |last9=Jackson |first9=Robert B. |last10=Janssens-Maenhout |first10=Greet |date=October 2020 |title=A comprehensive quantification of global nitrous oxide sources and sinks |url=https://www.nature.com/articles/s41586-020-2780-0 |url-status=bot: unknown |journal=Nature |language=en |volume=586 |issue=7828 |pages=248–256 |bibcode=2020Natur.586..248T |doi=10.1038/s41586-020-2780-0 |issn=1476-4687 |pmid=33028999 |hdl=1871.1/c74d4b68-ecf4-4c6d-890d-a1d0aaef01c9 |s2cid=222217027 |archive-url=https://web.archive.org/web/20201203131716/https://www.nature.com/articles/s41586-020-2780-0 |archive-date=3 December 2020 |access-date=2020-11-09|hdl-access=free }}</ref><ref name=":0">{{cite journal |author=Thompson, R. L. |author2=Lassaletta, L. |author3=Patra, P. K. |title=Acceleration of global N<sub>2</sub>O emissions seen from two decades of atmospheric inversion |journal=Nat. Clim. Change |year=2019 |volume=9 |issue=12 |pages=993–998 |doi=10.1038/s41558-019-0613-7|bibcode=2019NatCC...9..993T |s2cid=208302708 |url=http://pure.iiasa.ac.at/id/eprint/16173/2/N2O_paper_SI_revision2_v1.docx|hdl=11250/2646484 |hdl-access=free }}</ref> as nitrogen fertilisers are digested into nitrous oxide by soil micro-organisms.<ref>{{Cite web |date=2021-12-13 |title=Reduce nitrous oxide emissions |url=https://www.agmatters.nz/goals/reduce-nitrous-oxide/ |access-date=2024-04-01 |website=Ag Matters |language=en}}</ref> As the third most important [[greenhouse gas]], nitrous oxide substantially contributes to [[global warming]].<ref name="ipccar5">{{cite book |url=https://www.ipcc.ch/report/ar5/wg1/ |contribution= Chapter 8 |title=AR5 Climate Change 2013: The Physical Science Basis |pages=677–678}}</ref><ref name="physorg">{{cite news |title=Nitrous oxide emissions pose an increasing climate threat, study finds |language=en |work=phys.org |url=https://phys.org/news/2020-10-nitrous-oxide-emissions-pose-climate.html |access-date=2020-11-09}}</ref> Reduction of emissions is an important goal in the [[politics of climate change]].<ref>{{Cite web |last=Mundschenk |first=Susanne |date=3 August 2022 |title=The Netherlands is showing how not to tackle climate change {{!}} The Spectator |url=https://www.spectator.co.uk/article/the-netherlands-is-showing-how-not-to-tackle-climate-change |access-date=2022-08-28 |website=www.spectator.co.uk |language=en}}</ref>
== Discovery and early use ==
The gas was first synthesised in 1772 by English [[Natural philosophy|natural philosopher]] and chemist [[Joseph Priestley]] who called it ''dephlogisticated nitrous air'' (see [[phlogiston theory]])<ref name="Nitrous Oxide pioneers">{{cite journal|last=Keys|first=T.E.|year=1941|title=The Development of Anesthesia|journal=Anesthesiology|volume=2|issue=5|pages=552–574|bibcode=1982AmSci..70..522D|doi=10.1097/00000542-194109000-00008|s2cid=73062366|doi-access=free}}</ref> or ''inflammable nitrous air''.<ref>{{cite journal|last1=McEvoy|first1=J. G.|title=Gases, God and the balance of nature: a commentary on Priestley (1772) 'Observations on different kinds of air'|journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|date=6 March 2015|volume=373|issue=2039|page=20140229|doi=10.1098/rsta.2014.0229|pmc=4360083|pmid=25750146|bibcode=2015RSPTA.37340229M}}</ref> Priestley published his discovery in the book [[Experiments and Observations on Different Kinds of Air|''Experiments and Observations on Different Kinds of Air (1775)'']], where he described how to produce the preparation of "nitrous air diminished", by heating iron filings dampened with [[nitric acid]].<ref name="Joseph Priestley">{{cite web |year=1776|title=Experiments and Observations on Different Kinds of Air |website=Erowid |url=http://www.erowid.org/chemicals/nitrous/nitrous_journal1.shtml |author=Priestley J}}</ref>
[[File:Laughing_gas_Rumford_Davy.jpg|upright=1.4|thumb|"Living Made Easy": A satirical print from 1830 depicting [[Humphry Davy]] administering a dose of laughing gas to a woman|left]]
The first important use of nitrous oxide was made possible by [[Thomas Beddoes]] and [[James Watt]], who worked together to publish the book ''Considerations on the Medical Use and on the Production of Factitious Airs (1794)''. This book was important for two reasons. First, James Watt had invented a novel machine to produce "[[factitious airs]]" (including nitrous oxide) and a novel "breathing apparatus" to inhale the gas. Second, the book also presented the new medical theories by Thomas Beddoes, that [[tuberculosis]] and other lung diseases could be treated by inhalation of "Factitious Airs".<ref name="Drug discovery" />
[[File:Anaesthesia exhibition, 1946 Wellcome M0009908.jpg|thumb|right|Sir [[Humphry Davy]]'s ''Researches chemical and philosophical: chiefly concerning nitrous oxide'' (1800), pages 556 and 557 (right), outlining potential anaesthetic properties of nitrous oxide in relieving pain during surgery]]
The machine to produce "Factitious Airs" had three parts: a furnace to burn the needed material, a vessel with water where the produced gas passed through in a spiral pipe (for impurities to be "washed off"), and finally the gas cylinder with a gasometer where the gas produced, "air", could be tapped into portable air bags (made of airtight oily silk). The breathing apparatus consisted of one of the portable air bags connected with a tube to a mouthpiece. With this new equipment being engineered and produced by 1794, the way was paved for [[clinical trial]]s,{{Clarify|date=April 2011}} which began in 1798 when Thomas Beddoes established the ''"[[Pneumatic Institution]] for Relieving Diseases by Medical Airs"'' in [[Hotwells]] ([[Bristol]]). In the basement of the building, a large-scale machine was producing the gases under the supervision of a young Humphry Davy, who was encouraged to experiment with new gases for patients to inhale.<ref name="Drug discovery" /> The first important work of Davy was examination of the nitrous oxide, and the publication of his results in the book: ''Researches, Chemical and Philosophical (1800)''. In that publication, Davy notes the analgesic effect of nitrous oxide at page 465 and its potential to be used for surgical operations at page 556.<ref name="Humphry Davy">{{cite book|url=https://books.google.com/books?id=jhUAAAAAQAAJ|title=Researches, chemical and philosophical –chiefly concerning nitrous oxide or dephlogisticated nitrous air, and its respiration|publisher=Printed for J. Johnson|year=1800|author=Davy H}}</ref> Davy coined the name "laughing gas" for nitrous oxide.<ref>{{cite book|last1=Hardman|first1=Jonathan G.|title=Oxford Textbook of Anaesthesia|date=2017|publisher=Oxford University Press|page=529|isbn=978-0-19-964204-5}}</ref>
Despite Davy's discovery that inhalation of nitrous oxide could relieve a conscious person from pain, another 44 years elapsed before doctors attempted to use it for [[Anesthesia|anaesthesia]]. The use of nitrous oxide as a [[Recreational drug use|recreational drug]] at "laughing gas parties", primarily arranged for the [[Social class in the United Kingdom#Upper class|British upper class]], became an immediate success beginning in 1799. While the effects of the gas generally make the user appear stuporous, dreamy and sedated, some people also "get the giggles" in a state of euphoria, and frequently erupt in laughter.<ref name="Illicit drugs">{{cite web|url=http://www.druglibrary.org/schaffer/Library/studies/cu/CU43.html|title=Consumers Union Report on Licit and Illicit Drugs, Part VI – Inhalants and Solvents and Glue-Sniffing|year=1972|author=Brecher EM|work=Consumer Reports Magazine|access-date=18 December 2013}}</ref>
One of the earliest commercial producers in the U.S. was [[George Poe]], cousin of the poet [[Edgar Allan Poe]], who also was the first to liquefy the gas.<ref name="wp">{{cite news|url=https://pqasb.pqarchiver.com/washingtonpost_historical/access/243050292.html?dids=243050292:243050292&FMT=ABS&FMTS=ABS:FT&date=FEB+03%2C+1914&author=&pub=The+Washington+Post&desc=GEORGE+POE+IS+DEAD&pqatl=google|title=George Poe is Dead|date=3 February 1914|newspaper=Washington Post|access-date=29 December 2007|archive-date=1 March 2013|archive-url=https://web.archive.org/web/20130301050848/http://pqasb.pqarchiver.com/washingtonpost_historical/access/243050292.html?dids=243050292:243050292&FMT=ABS&FMTS=ABS:FT&date=FEB+03%2C+1914&author=&pub=The+Washington+Post&desc=GEORGE+POE+IS+DEAD&pqatl=google}}</ref>
==Chemical properties and reactions==
Nitrous oxide is a colourless gas with a faint, sweet odour.
Nitrous oxide supports combustion by releasing the [[Coordinate covalent bond|dipolar bonded]] oxygen radical, and can thus relight a glowing [[Splint (laboratory equipment)|splint]].
{{chem|N|2|O}} is inert at room temperature and has few reactions. At elevated temperatures, its reactivity increases. For example, nitrous oxide reacts with {{chem|link=Sodium amide|NaNH|2}} at {{convert|187|C}} to give {{chem|link=Sodium azide|NaN|3}}:
:{{chem2|2 NaNH2 + N2O -> NaN3 + NaOH + NH3 }}
This reaction is the route adopted by the commercial chemical industry to produce [[azide]] salts, which are used as detonators.<ref name="InorgChem">{{cite book|title=Inorganic Chemistry|url=https://archive.org/details/inorganicchemist00hous_159|url-access=limited|publisher=Pearson|year=2008|isbn=978-0-13-175553-6|edition=3rd|page=[https://archive.org/details/inorganicchemist00hous_159/page/n502 464]|chapter=Chapter 15: The group 15 elements|author1=Housecroft, Catherine E.|author2=Sharpe, Alan G.}}</ref>
==Mechanism of action==
The pharmacological [[mechanism of action]] of inhaled {{chem|N|2|O}} is not fully known. However, it has been shown to directly modulate a broad range of [[ligand-gated ion channel]]s, which likely plays a major role. It moderately blocks [[NMDA receptor|NMDAR]] and [[CHRNB2|β{{ssub|2}}-subunit]]-containing [[nicotinic acetylcholine receptor|nACh channels]], weakly inhibits [[AMPA receptor|AMPA]], [[kainate receptor|kainate]], [[GABAA-rho receptor|GABA{{ssub|C}}]] and [[5-HT3 receptor|5-HT{{ssub|3}} receptors]], and slightly potentiates [[GABAA receptor|GABA{{ssub|A}}]] and [[glycine receptor]]s.<ref name="pmid11020766">{{cite journal|vauthors=Yamakura T, Harris RA |title=Effects of gaseous anaesthetics nitrous oxide and xenon on ligand-gated ion channels. Comparison with isoflurane and ethanol |journal=Anesthesiology |volume=93 |issue=4 |pages=1095–101 |year=2000 |pmid=11020766 |doi=10.1097/00000542-200010000-00034|s2cid=4684919 |doi-access=free }}</ref><ref name="pmid9822732">{{cite journal |vauthors=Mennerick S, Jevtovic-Todorovic V, Todorovic SM, Shen W, Olney JW, Zorumski CF |title=Effect of nitrous oxide on excitatory and inhibitory synaptic transmission in hippocampal cultures |journal=Journal of Neuroscience |volume=18 |issue=23 |pages=9716–26 |year=1998 |pmid=9822732 |pmc=6793274 |doi=10.1523/JNEUROSCI.18-23-09716.1998 }}</ref> It also has been shown to activate [[Two-pore-domain potassium channel|two-pore-domain {{chem|K|+}} channels]].<ref name="pmid14742687">{{cite journal |vauthors=Gruss M, Bushell TJ, Bright DP, Lieb WR, Mathie A, Franks NP |title=Two-pore-domain K<sup>+</sup> channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane |journal=Molecular Pharmacology |volume=65 |issue=2 |pages=443–52 |year=2004 |pmid=14742687 |doi=10.1124/mol.65.2.443|s2cid=7762447 }}</ref> While {{chem|N|2|O}} affects several ion channels, its anaesthetic, [[hallucinogenic]] and [[euphoriant]] effects are likely caused mainly via inhibition of NMDA receptor-mediated currents.<ref name="pmid11020766" /><ref name="pmid17352529">{{cite journal|vauthors=Emmanouil DE, Quock RM |title=Advances in Understanding the Actions of Nitrous Oxide |journal=Anesthesia Progress |volume=54 |issue=1 |pages=9–18 |year=2007 |pmid=17352529 |pmc=1821130 |doi=10.2344/0003-3006(2007)54[9:AIUTAO]2.0.CO;2}}</ref> In addition to its effects on ion channels, {{chem|N|2|O}} may act similarly to [[nitric oxide]] (NO) in the central nervous system.<ref name="pmid17352529" /> Nitrous oxide is 30 to 40 times more soluble than nitrogen.
The effects of inhaling sub-anaesthetic doses of nitrous oxide may vary unpredictably with settings and individual differences;<ref>{{Cite journal|last1=Atkinson|first1=Roland M.|last2=Green|first2=J. DeWayne|last3=Chenoweth|first3=Dennis E.|last4=Atkinson|first4=Judith Holmes|date=1979-10-01|title=Subjective Effects of Nitrous Oxide: Cognitive, Emotional, Perceptual and Transcendental Experiences|journal=Journal of Psychedelic Drugs|volume=11|issue=4|pages=317–330|doi=10.1080/02791072.1979.10471415|pmid=522172}}</ref><ref>{{Cite journal|last1=Walker|first1=Diana J.|last2=Zacny|first2=James P.|date=2001-09-01|title=Within- and between-subject variability in the reinforcing and subjective effects of nitrous oxide in healthy volunteers|journal=Drug and Alcohol Dependence|volume=64|issue=1|pages=85–96|doi=10.1016/s0376-8716(00)00234-9|pmid=11470344}}</ref> however, Jay (2008)<ref name="Mike Jay 22–25">{{Cite journal|vauthors=Jay M |date=2008-09-01|title=Nitrous oxide: recreational use, regulation and harm reduction|journal=Drugs and Alcohol Today|volume=8|issue=3|pages=22–25|doi=10.1108/17459265200800022}}</ref> suggests that it reliably induces the following states and sensations:
* Intoxication
* Euphoria/dysphoria
* Spatial disorientation
* Temporal disorientation
* Reduced pain sensitivity
A minority of users also experience uncontrolled vocalisations and muscular spasms. These effects generally disappear minutes after removal of the nitrous oxide source.<ref name="Mike Jay 22–25"/>
===Anxiolytic effect===
In behavioural tests of [[anxiety]], a low dose of {{chem|N|2|O}} is an effective [[anxiolytic]]. This anti-anxiety effect is associated with enhanced activity of GABA{{ssub|A}} receptors, as it is partially reversed by [[GABAA receptor|benzodiazepine receptor]] [[receptor antagonist|antagonists]]. Mirroring this, animals that have developed tolerance to the anxiolytic effects of [[benzodiazepine]]s are partially tolerant to {{chem|N|2|O}}.<ref name="emmanouil">{{cite journal|title=Nitrous oxide anxiolytic effect in mice in the elevated plus maze: mediation by benzodiazepine receptors |vauthors=Emmanouil DE, Johnson CH, Quock RM |journal=Psychopharmacology |volume=115 |issue=1–2 |pages=167–72 |year=1994 |doi=10.1007/BF02244768 |pmid=7862891|s2cid=21652496 }}</ref> Indeed, in humans given 30% {{chem|N|2|O}}, benzodiazepine receptor antagonists reduced the subjective reports of feeling "high", but did not alter [[psychomotor learning|psychomotor]] performance.<ref name="zacny">{{cite journal|title=Flumazenil may attenuate some subjective effects of nitrous oxide in humans: a preliminary report |vauthors=Zacny JP, Yajnik S, Coalson D, Lichtor JL, Apfelbaum JL, Rupani G, Young C, Thapar P, Klafta J |journal=Pharmacology Biochemistry and Behavior |volume=51 |issue=4 |pages=815–9 |year=1995 |doi=10.1016/0091-3057(95)00039-Y |pmid=7675863|s2cid=39068081 }}</ref><ref>{{Cite journal |last=Gillman |first=Mark Akfred |date=2022 |title=What is better for psychiatry: Titrated or fixed concentrations of nitrous oxide? |journal=Front. Psychiatry |volume=13 |issue=773190 |pages=460–3|doi=10.3389/fpsyt.2022.773190 |pmid=36072452 |pmc=9441863 |doi-access=free }}</ref>
===Analgesic effect===
The analgesic effects of {{chem|N|2|O}} are linked to the interaction between the [[Opioid#Endogenous opioids|endogenous opioid]] system and the descending [[Norepinephrine|noradrenergic]] system. When animals are given morphine chronically, they develop tolerance to its pain-killing effects, and this also renders the animals tolerant to the analgesic effects of {{chem|N|2|O}}.<ref>{{cite journal|title=Tolerance to nitrous oxide analgesia in rats and mice |vauthors=Berkowitz BA, Finck AD, Hynes MD, Ngai SH |journal=Anesthesiology |volume=51 |issue=4 |pages=309–12 |year=1979 |doi=10.1097/00000542-197910000-00006 |pmid=484891|s2cid=26281498 |doi-access=free }}</ref> Administration of [[antibodies]] that bind and block the activity of some endogenous opioids (not [[Beta-Endorphin|β-endorphin]]) also block the antinociceptive effects of {{chem|N|2|O}}.<ref name="branda">{{cite journal|title=Role of brain dynorphin in nitrous oxide antinociception in mice |vauthors=Branda EM, Ramza JT, Cahill FJ, Tseng LF, Quock RM |journal=Pharmacology Biochemistry and Behavior |volume=65 |pages=217–21 |year=2000 |doi=10.1016/S0091-3057(99)00202-6 |pmid=10672972 |issue=2|s2cid=1978597 }}</ref> Drugs that inhibit the breakdown of endogenous opioids also potentiate the antinociceptive effects of {{chem|N|2|O}}.<ref name="branda" /> Several experiments have shown that opioid receptor antagonists applied directly to the brain block the antinociceptive effects of {{chem|N|2|O}}, but these drugs have no effect when injected into the [[spinal cord]].
Apart from an indirect action, nitrous oxide, like morphine <ref>Gillman M.A. [1986a]. Minireview: Analgesic [sub anaesthetic] nitrous oxide interacts with the endogenous opioid system : A review of the evidence. Life Sciences 39: 1209-1221</ref> also interacts directly with the endogenous opioid system by binding at opioid receptor binding sites.<ref>(Daras, C., Cantrill, R. C., Gillman, M. A. [1983]. 3[H]-Naloxone displacement: evidence for nitrous oxide as an opioid agonist. European Journal of Pharmacology 89: 177-8.</ref><ref>Ori, C., Ford-Rice, F., London, E. D. [1989]. Effects of nitrous oxide and halothane on mu and kappa opioid receptors in guinea-pig brain. Anesthesiology 70: 541-544.)</ref>
Conversely, [[alpha-2 adrenergic receptor|α{{ssub|2}}-adrenoceptor]] antagonists block the pain-reducing effects of {{chem|N|2|O}} when given directly to the spinal cord, but not when applied directly to the brain.<ref name="guo">{{cite journal|title=Nitrous oxide produces antinociceptive response via alpha2B and/or alpha2C adrenoceptor subtypes in mice |vauthors=Guo TZ, Davies MF, Kingery WS, Patterson AJ, Limbird LE, Maze M |journal=Anesthesiology |volume=90 |issue=2 |pages=470–6 |year=1999 |pmid=9952154 |doi=10.1097/00000542-199902000-00022|doi-access=free }}</ref> Indeed, [[alpha-2B adrenergic receptor|α{{ssub|2B}}-adrenoceptor]] knockout mice or animals depleted in [[norepinephrine]] are nearly completely resistant to the antinociceptive effects of {{chem|N|2|O}}.<ref>{{cite journal|title=Antinociceptive action of nitrous oxide is mediated by stimulation of noradrenergic neurons in the brainstem and activation of [alpha]{{ssub|2B}} adrenoceptors |vauthors=Sawamura S, Kingery WS, Davies MF, Agashe GS, Clark JD, Koblika BK, Hashimoto T, Maze M |journal=J. Neurosci. |volume=20 |issue=24 |pages=9242–51 |year=2000 |pmid=11125002 |pmc=6773006 |doi=10.1523/JNEUROSCI.20-24-09242.2000 }}</ref> Apparently {{chem|N|2|O}}-induced release of endogenous opioids causes disinhibition of [[brainstem]] noradrenergic neurons, which release norepinephrine into the spinal cord and inhibit pain signalling.<ref name="pmid10781114">{{cite journal|vauthors=Maze M, Fujinaga M |title=Recent advances in understanding the actions and toxicity of nitrous oxide |journal=Anaesthesia |volume=55 |issue=4 |pages=311–4 |year=2000 |pmid=10781114 |doi=10.1046/j.1365-2044.2000.01463.x|s2cid=39823627 |doi-access=free }}</ref> Exactly how {{chem|N|2|O}} causes the release of endogenous opioid peptides remains uncertain.
==Production==
Various methods of producing nitrous oxide are used.<ref name=CatalysisToday2005>{{cite journal |last1=Parmon |first1=V. N. |last2=Panov |first2=G. I. |last3=Uriarte |first3=A. |last4=Noskov |first4=A. S. |title=Nitrous oxide in oxidation chemistry and catalysis application and production |journal=Catalysis Today |volume=100 |issue=2005 |pages=115–131|doi=10.1016/j.cattod.2004.12.012|year=2005 }}</ref>
===Industrial methods===
[[File:Nitrous oxide production.png|thumb|Nitrous oxide production]]
Nitrous oxide is prepared on an industrial scale by carefully heating [[ammonium nitrate]]<ref name=CatalysisToday2005 /> at about 250 °C, which decomposes into nitrous oxide and water vapour.<ref>{{cite book|last=Holleman |first=A. F. |author2=Wiberg, E. |title=Inorganic Chemistry |publisher=Academic Press |location=San Diego |year=2001 |isbn=978-0-12-352651-9}}</ref>
:{{chem2 | NH4NO3 -> 2 H2O + N2O }}
The addition of various [[phosphate]] salts favours formation of a purer gas at slightly lower temperatures. This reaction may be difficult to control, resulting in [[detonation]].<ref>{{cite web|url=http://www.sanghioverseas.com/nitrous_oxide_gas_plants/nitrous_oxide_gas_plants.htm |publisher=Sanghi Organization |title=Nitrous oxide plant |access-date=18 December 2013 |archive-url=https://web.archive.org/web/20131127131246/http://sanghioverseas.com/nitrous_oxide_gas_plants/nitrous_oxide_gas_plants.htm |archive-date=27 November 2013 }}</ref>
===Laboratory methods===
The decomposition of ammonium nitrate is also a common laboratory method for preparing the gas. Equivalently, it can be obtained by heating a mixture of [[sodium nitrate]] and [[ammonium sulfate]]:<ref>[http://chemistry.tutorvista.com/inorganic-chemistry/nitrogen-family.html "Nitrogen Family"] {{Webarchive|url=https://web.archive.org/web/20141021035916/http://chemistry.tutorvista.com/inorganic-chemistry/nitrogen-family.html |date=21 October 2014 }}. chemistry.tutorvista.com</ref>
:{{chem2 | 2 NaNO3 + (NH4)2SO4 -> Na2SO4 + 2 N2O + 4 H2O }}
Another method involves the reaction of urea, nitric acid and sulfuric acid:<ref>[https://www.erowid.org/archive/rhodium/chemistry/nitrous.html "Preparation of Nitrous Oxide from Urea, Nitric Acid and Sulfuric Acid"].</ref>
:{{chem2 | 2 (NH2)2CO + 2 HNO3 + H2SO4 -> 2 N2O + 2 CO2 + (NH4)2SO4 + 2 H2O }}
Direct oxidation of ammonia with a [[manganese dioxide]]-[[Bismuth(III) oxide|bismuth oxide]] catalyst has been reported:<ref>{{cite journal|vauthors=Suwa T, Matsushima A, Suziki Y, Namina Y |title= Manufacture of Nitrous Oxide by the Catalytic Oxidation of Ammonia|journal= The Journal of the Society of Chemical Industry, Japan|volume=64|issue=11|pages= 1879–1888|year=1961|doi=10.1246/nikkashi1898.64.11_1879|doi-access=free}}</ref> cf. [[Ostwald process]].
:{{chem2 | 2 NH3 + 2 O2 -> N2O + 3 H2O }}
[[Hydroxylammonium chloride]] reacts with [[sodium nitrite]] to give nitrous oxide. If the nitrite is added to the hydroxylamine solution, the only remaining by-product is salt water. If the hydroxylamine solution is added to the nitrite solution (nitrite is in excess), however, then toxic higher oxides of nitrogen also are formed:
:{{chem2 | NH3OHCl + NaNO2 -> N2O + NaCl + 2 H2O }}
Treating {{chem|HNO|3}} with {{chem|SnCl|2}} and HCl also has been demonstrated:
:{{chem2 | 2 HNO3 + 8 HCl + 4 SnCl2 -> 5 H2O + 4 SnCl4 + N2O }}
[[Hyponitrous acid]] decomposes to N{{ssub|2}}O and water with a [[half-life]] of 16 days at 25 °C at pH 1–3.<ref name="Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier {{ISBN|0-12-352651-5}}</ref>
:{{chem2 | H2N2O2 -> H2O + N2O }}
==Atmospheric occurrence==
[[File:N2O mm.png|thumb|upright=1.2|Nitrous oxide (N<sub>2</sub>O) measured by the Advanced Global Atmospheric Gases Experiment ([http://agage.mit.edu/ AGAGE]) in the lower atmosphere ([[troposphere]]) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in [[Parts-per notation|parts-per-billion]].]]
[[File:HATS Nitrous Oxide concentration.png|thumb|right|Nitrous oxide atmospheric concentration since 1978]]
[[File:HATS Nitrous Oxide growth rate.png|thumb|right|Annual growth rate of atmospheric nitrous oxide since 2000]]
[[File:Global Nitrous Oxide Budget 2020.png|thumb|Earth's nitrous oxide budget from the [[Global Carbon Project]] (2020)<ref>{{cite web |url=https://www.globalcarbonproject.org/nitrousoxidebudget/index.htm |title={{chem|N|2|O}} Budget |publisher=Global Carbon Project |access-date=2020-11-09}}</ref>]]
Nitrous oxide is a [[Atmospheric chemistry#Atmospheric composition|minor component of Earth's atmosphere]] and is an active part of the planetary [[nitrogen cycle]]. Based on analysis of air samples gathered from sites around the world, its [[concentration]] surpassed 330 [[Parts-per notation|ppb]] in 2017.<ref name="agage">{{cite web |url=https://agage2.eas.gatech.edu/data_archive/data_figures/monthly/pdf/N2O_mm.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://agage2.eas.gatech.edu/data_archive/data_figures/monthly/pdf/N2O_mm.pdf |archive-date=2022-10-09 |url-status=live |title=Nitrous Oxide (N2O) Mole Fraction |publisher=Massachusetts Institute of Technology |access-date=2021-02-15}}</ref> The growth rate of about 1 ppb per year has also accelerated during recent decades.<ref name="noaaesrl">{{cite web |url=https://www.esrl.noaa.gov/gmd/ccgg/trends_n2o/ |title=Trends in Atmospheric Nitrous Oxide |publisher=National Oceanic and Atmospheric Administration / Earth System Research Laboratories |access-date=2021-02-15}}</ref> Nitrous oxide's atmospheric abundance has grown more than 20% from a base level of about 270 ppb in 1750.<ref name="tar">{{cite book |url=https://www.ipcc.ch/report/ar3/wg1/|contribution= Chapter 6 |title=TAR Climate Change 2001: The Scientific Basis |page=358}}</ref>
Important atmospheric properties of {{chem|N|2|O}} are summarized in the following table:
{| class="wikitable"
! Property
! Value
|-
| [[Ozone depletion potential]] (ODP)
| 0.017<ref name=Ravishankara>{{Citation|url=https://www.sciencemag.org/content/suppl/2009/08/27/1176985.DC1/Ravishankara.SOM.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.sciencemag.org/content/suppl/2009/08/27/1176985.DC1/Ravishankara.SOM.pdf |archive-date=2022-10-09 |url-status=live|title=Supporting Online Material for - Nitrous Oxide (N<sub>2</sub>O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century|last1=Ravishankara|first1=A. R.|last2=Daniel|first2=John S.|last3=Portmann|first3=Robert W.|date=2009-08-27|journal= Science |volume=326|issue=5949|pages=123–125|doi=10.1126/science.1176985|pmid=19713491|bibcode=2009Sci...326..123R|s2cid=2100618}}</ref> ([[Trichlorofluoromethane|CCl<sub>3</sub>F]] = 1)
|-
| [[Global warming potential]] (GWP: 100-year)
| 273<ref name="ar5">{{cite book |url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials |title=US Environmental Protection Agency |date=12 January 2016 |page= |language=English |contribution=}}</ref> ([[Carbon dioxide|CO<sub>2</sub>]] = 1)
|-
| [[Greenhouse gas#Atmospheric lifetime|Atmospheric lifetime]]
| 116 ± 9 years<ref name="ar6"/>
|-
|}
In 2022 the IPCC reported that: "The human perturbation of the natural nitrogen cycle through the use of synthetic fertilizers and manure, as well as nitrogen deposition resulting from land-based agriculture and fossil fuel burning has been the largest driver of the increase in atmospheric N2O of 31.0 ± 0.5 ppb (10%) between 1980 and 2019."<ref name="ar6">{{Cite report |title=Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks |url=https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-5/ |access-date=2023-05-06 |website=www.ipcc.ch |language=en}}</ref>
===Emissions by source===
17.0 (12.2 to 23.5) million tonnes total annual average nitrogen in {{chem|N|2|O}} was emitted in 2007–2016.<ref name="ar6"/> About 40% of {{chem|N|2|O}} emissions are from humans and the rest are part of the natural [[nitrogen cycle]].<ref>{{Cite web |last=US EPA |first=OAR |date=2015-12-23 |title=Overview of Greenhouse Gases |url=https://www.epa.gov/ghgemissions/overview-greenhouse-gases |access-date=2023-05-04 |website=www.epa.gov |language=en}}</ref> The {{chem|N|2|O}} emitted each year by humans has a greenhouse effect equivalent to about 3 billion tonnes of carbon dioxide: for comparison humans emitted 37 billion tonnes of actual carbon dioxide in 2019, and methane equivalent to 9 billion tonnes of carbon dioxide.<ref>{{Cite web |title={{!}} Greenhouse Gas (GHG) Emissions {{!}} Climate Watch |url=https://www.climatewatchdata.org/ghg-emissions?breakBy=gas&end_year=2019&gases=n2o&start_year=1990 |access-date=2023-05-04 |website=www.climatewatchdata.org}}</ref>
Most of the {{chem|N|2|O}} emitted into the atmosphere, from natural and anthropogenic sources, is produced by [[microorganism]]s such as [[denitrifying bacteria]] and [[fungus|fungi]] in soils and oceans.<ref name="Sloss1992">{{cite book|last=Sloss |first=Leslie L. |title=Nitrogen Oxides Control Technology Fact Book |url=https://books.google.com/books?id=--C_JAU7W8QC&pg=PA6 |year=1992 |publisher=William Andrew |isbn=978-0-8155-1294-3 |page=6}}</ref> Soils under natural vegetation are an important source of nitrous oxide, accounting for 60% of all naturally produced emissions. Other natural sources include the oceans (35%) and atmospheric chemical reactions (5%).<ref name="inputs">U.S. Environmental Protection Agency (2010), "[https://nepis.epa.gov/Exe/ZyPDF.cgi/P100717T.PDF?Dockey=P100717T.PDF Methane and Nitrous Oxide Emissions from Natural Sources]". Report EPA 430-R-10-001.</ref> [[Wetland]]s can also be [[Greenhouse gas emissions from wetlands|emitters of nitrous oxide]].<ref name=":4">{{Cite journal |last=Bange |first=Hermann W. |date=2006 |title=Nitrous oxide and methane in European coastal waters |url=https://linkinghub.elsevier.com/retrieve/pii/S0272771406002496 |journal=Estuarine, Coastal and Shelf Science |language=en |volume=70 |issue=3 |pages=361–374 |bibcode=2006ECSS...70..361B |doi=10.1016/j.ecss.2006.05.042}}</ref><ref name=":3">{{cite journal |last1=Thompson |first1=A. J. |last2=Giannopoulos |first2=G. |last3=Pretty |first3=J. |last4=Baggs |first4=E. M. |last5=Richardson |first5=D. J. |date=2012 |title=Biological sources and sinks of nitrous oxide and strategies to mitigate emissions |journal=Philosophical Transactions of the Royal Society B |volume=367 |issue=1593 |pages=1157–1168 |doi=10.1098/rstb.2011.0415 |pmc=3306631 |pmid=22451101}}</ref> Emissions from thawing [[permafrost]] may be significant, but as of 2022 this is not certain.<ref name="ar6" />
The main components of anthropogenic emissions are fertilised agricultural soils and livestock manure (42%), runoff and leaching of fertilisers (25%), biomass burning (10%), fossil fuel combustion and industrial processes (10%), biological degradation of other nitrogen-containing atmospheric emissions (9%) and human [[sewage]] (5%).<ref name="denman">K. L. Denman, G. Brasseur, et al. (2007), "Couplings Between Changes in the Climate System and Biogeochemistry". In ''Fourth Assessment Report of the Intergovernmental Panel on Climate Change'', Cambridge University Press.</ref><ref>{{Cite book |url=http://www.fao.org/docrep/010/a0701e/a0701e00.HTM |title=Livestock's long shadow: Environmental issues and options |publisher=Fao.org |author1=Steinfeld, H. |author2=Gerber, P. |author3=Wassenaar, T. |author4=Castel, V. |author5=Rosales, M. |author6=de Haan, C. |access-date=2 February 2008 |year=2006}}</ref><ref name="epaUpdated">{{cite web|url=https://www3.epa.gov/climatechange/ghgemissions/gases/n2o.html |title=Overview of Greenhouse Gases: Nitrous Oxide |publisher=U.S. Environmental Protection Agency |access-date=31 March 2016|date=23 December 2015 |url-status=live |archive-url= https://web.archive.org/web/20160812082641/https://www.epa.gov/ghgemissions/overview-greenhouse-gases |archive-date=12 August 2016 }}</ref><ref name="epa">{{cite web |url= http://www.epa.gov/nitrousoxide/sources.html |title=Nitrous Oxide: Sources and Emissions |publisher=U.S. Environmental Protection Agency |access-date=2 February 2008 |year=2006 |archive-url= https://web.archive.org/web/20080116204312/http://www.epa.gov/nitrousoxide/sources.html |archive-date=16 January 2008}}</ref><ref>IPCC. 2013. Climate change: the physical basis (WG I, full report). p. 512.</ref> Agriculture enhances nitrous oxide production through soil cultivation, the use of nitrogen [[Fertilizer|fertilisers]] and animal waste handling.<ref>{{Cite journal|last1=Thompson|first1=R. L.|last2=Lassaletta|first2=L.|last3=Patra|first3=P. K.|last4=Wilson|first4=C. |last5=Wells|first5=K. C.|last6=Gressent|first6=A.|last7=Koffi|first7=E. N.|last8=Chipperfield|first8=M. P.|last9=Winiwarter|first9=W. |last10=Davidson|first10=E. A.|last11=Tian|first11=H.|display-authors=3|date=2019-11-18|title=Acceleration of global N 2 O emissions seen from two decades of atmospheric inversion|journal=Nature Climate Change|language=en|volume=9|issue=12 |pages=993–998|doi=10.1038/s41558-019-0613-7|issn=1758-6798|bibcode=2019NatCC...9..993T|s2cid=208302708|hdl=11250/2646484|hdl-access=free}}</ref> These activities stimulate naturally occurring bacteria to produce more nitrous oxide. Nitrous oxide emissions from soil can be challenging to measure as they vary markedly over time and space,<ref>{{cite journal |last1=Molodovskaya |first1=Marina |last2=Warland |first2=Jon |last3=Richards |first3=Brian K. |last4=Öberg |first4=Gunilla |last5=Steenhuis |first5=Tammo S. |title=Nitrous Oxide from Heterogeneous Agricultural Landscapes: Source Contribution Analysis by Eddy Covariance and Chambers |journal=Soil Science Society of America Journal |date=2011 |volume=75 |issue=5 |page=1829 |doi=10.2136/SSSAJ2010.0415|bibcode=2011SSASJ..75.1829M }}</ref> and the majority of a year's emissions may occur when conditions are favorable during "hot moments"<ref>{{cite journal | last1 = Molodovskaya | first1 = M. | last2 = Singurindy | first2 = O. | last3 = Richards | first3 = B. K. | last4 = Warland | first4 = J. S. | last5 = Johnson | first5 = M. | last6 = Öberg | first6 = G. | last7 = Steenhuis | first7 = T. S. | year = 2012 | title = Temporal variability of nitrous oxide from fertilized croplands: hot moment analysis | journal = Soil Science Society of America Journal | volume = 76 | issue = 5| pages = 1728–1740 | doi = 10.2136/sssaj2012.0039 | bibcode = 2012SSASJ..76.1728M | s2cid = 54795634 }}</ref><ref>{{cite journal |last1=Singurindy |first1=Olga |last2=Molodovskaya |first2=Marina |last3=Richards |first3=Brian K. |last4=Steenhuis |first4=Tammo S. |title=Nitrous oxide emission at low temperatures from manure-amended soils under corn (Zea mays L.) |journal=Agriculture, Ecosystems & Environment |date=July 2009 |volume=132 |issue=1–2 |pages=74–81 |doi=10.1016/j.agee.2009.03.001|bibcode=2009AgEE..132...74S }}</ref> and/or at favorable locations known as "hotspots".<ref>{{cite journal | last1 = Mason | first1 = C.W. | last2 = Stoof | first2 = C.R. | last3 = Richards | first3 = B.K. | last4 = Das | first4 = S. | last5 = Goodale | first5 = C.L. | last6 = Steenhuis | first6 = T.S. | year = 2017 | title = Hotspots of nitrous oxide emission in fertilized and unfertilized perennial grasses on wetness-prone marginal land in New York State | journal = Soil Science Society of America Journal | volume = 81 | issue = 3| pages = 450–458 | doi = 10.2136/sssaj2016.08.0249 | bibcode = 2017SSASJ..81..450M }}</ref>
Among industrial emissions, the production of nitric acid and [[adipic acid]] are the largest sources of nitrous oxide emissions. The adipic acid emissions specifically arise from the degradation of the [[nitrolic acid]] intermediate derived from the nitration of cyclohexanone.<ref name="denman"/><ref>{{cite journal|title=Abatement of N{{ssub|2}}O emissions produced in the adipic acid industry|author1=Reimer R. A. |author2=Slaten C. S. |author3=Seapan M. |author4=Lower M. W. |author5=Tomlinson P. E. | journal = Environmental Progress| year = 1994| volume = 13| issue = 2| pages = 134–137| doi = 10.1002/ep.670130217|bibcode=1994EnvPr..13..134R }}</ref><ref>{{cite journal|title=Abatement of N{{ssub|2}}O emissions produced in the adipic acid industry|author1=Shimizu, A. |author2=Tanaka, K. |author3=Fujimori, M. | journal = Chemosphere – Global Change Science| year = 2000| volume = 2| issue = 3–4| pages = 425–434| doi = 10.1016/S1465-9972(00)00024-6|bibcode=2000ChGCS...2..425S}}</ref>
===Biological processes===
Microbial processes that generate nitrous oxide may be classified as [[nitrification]] and [[denitrification]]. Specifically, they include:
* aerobic autotrophic nitrification, the stepwise oxidation of [[ammonia]] ({{chem|NH|3}}) to [[nitrite]] ({{chem|NO|2|−}}) and to [[nitrate]] ({{chem|NO|3|−}})<!-- (Kowalchuk and Stephen, 2001)-->
* anaerobic heterotrophic denitrification, the stepwise reduction of {{chem|NO|3|−}} to {{chem|NO|2|-}}, [[nitric oxide]] (NO), {{chem|N|2|O}} and ultimately {{chem|N|2}}, where facultative anaerobe bacteria use {{chem|NO|3|−}} as an electron acceptor in the respiration of organic material in the condition of insufficient oxygen ({{chem|O|2}})<!-- (Knowles, 1982)-->
* nitrifier denitrification, which is carried out by autotrophic {{chem|NH|3}}-oxidising bacteria and the pathway whereby ammonia ({{chem|NH|3}}) is oxidised to nitrite ({{chem|NO|2|−}}), followed by the reduction of {{chem|NO|2|-}} to nitric oxide (NO), {{chem|N|2|O}} and molecular nitrogen ({{chem|N|2}})<!-- (Webster and Hopkins, 1996; Wrage et al., 2001)-->
* heterotrophic nitrification<!-- (Robertson and Kuenen, 1990)-->
* aerobic denitrification by the same heterotrophic nitrifiers<!-- (Robertson and Kuenen, 1990) -->
* fungal denitrification<!-- (Laughlin and Stevens, 2002) -->
* non-biological chemodenitrification<!-- (Chalk and Smith, 1983; Van Cleemput and Baert, 1984; Martikainen and De Boer, 1993; Daum and Schenk, 1998; Mørkved et al., 2007)-->
These processes are affected by soil chemical and physical properties such as the availability of mineral nitrogen and [[organic matter]], acidity and soil type, as well as climate-related factors such as soil temperature and water content. <!--(Mosier, 1994; Bouwman, 1996; Beauchamp, 1997; Yamulki et al. 1997; Dobbie and Smith, 2003; Smith et al. 2003; Dalal et al. 2003) -->
The emission of the gas to the atmosphere is limited greatly by its consumption inside the cells, by a process catalysed by the enzyme [[nitrous-oxide reductase|nitrous oxide reductase]].<ref>{{cite book|author1=Schneider, Lisa K. |author2=Wüst, Anja |author3=Pomowski, Anja |author4=Zhang, Lin |author5=Einsle, Oliver |chapter=No Laughing Matter: The Unmaking of the Greenhouse Gas Dinitrogen Monoxide by Nitrous Oxide Reductase |year=2014|title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment|pages =177–210| volume =14 |series=Metal Ions in Life Sciences |editor=Kroneck, Peter M. H. |editor2=Sosa Torres, Martha E. |publisher= Springer|doi=10.1007/978-94-017-9269-1_8|pmid=25416395|isbn=978-94-017-9268-4}}</ref>
==Uses==
Line 163 ⟶ 287:
Also, cooking spray, made from various oils with [[lecithin]] [[emulsifier]], may use nitrous oxide [[propellant]], or alternatively food-grade [[ethanol|alcohol]] or [[propane]].
=== Anaesthesis ===
{{Further|Nitrous oxide (medication)}}
The first time nitrous oxide was used as an [[anaesthetic]] drug in the treatment of a patient was when dentist [[Horace Wells]], with assistance by [[Gardner Quincy Colton]] and [[John Mankey Riggs]], demonstrated insensitivity to pain from a [[dental extraction]] on 11 December 1844.<ref name="Discovery of Wells">{{Cite journal|year=1933|title=The Discoverer of Anæsthesia: Dr. Horace Wells of Hartford.|journal=The Yale Journal of Biology and Medicine|volume=5|issue=5|pages=421–430|pmc=2606479|pmid=21433572|last1=Erving|first1=H. W.}}</ref> In the following weeks, Wells treated the first 12 to 15 patients with nitrous oxide in [[Hartford, Connecticut]], and, according to his own record, only failed in two cases.<ref name="Horace Wells">{{cite book|url=https://books.google.com/books?id=exNtlBi8T4EC|title=A history of the discovery, of the application of nitrous oxide gas, ether, and other vapours, to surgical operations|publisher=J. Gaylord Wells|year=1847|author=Wells H}}</ref> In spite of these convincing results having been reported by Wells to the medical society in [[Boston]] in December 1844, this new method was not immediately adopted by other dentists. The reason for this was most likely that Wells, in January 1845 at his first public demonstration to the medical faculty in Boston, had been partly unsuccessful, leaving his colleagues doubtful regarding its efficacy and safety.<ref name="Discovery of anaesthesia">{{cite journal|year=2007|title=The discovery of modern anaesthesia-contributions of Davy, Clarke, Long, Wells and Morton|url=http://www.ijaweb.org/text.asp?2007/51/6/472/61183|journal=Indian J Anaesth|volume=51|issue=6|pages=472–8|vauthors=Desai SP, Desai MS, Pandav CS}}</ref> The method did not come into general use until 1863, when Gardner Quincy Colton successfully started to use it in all his "Colton Dental Association" clinics, that he had just established in [[New Haven, Connecticut|New Haven]] and [[New York City]].<ref name="Drug discovery" /> Over the following three years, Colton and his associates successfully administered nitrous oxide to more than 25,000 patients.<ref name="use in dentistry" /> Today, nitrous oxide is used in dentistry as an anxiolytic, as an adjunct to [[Local anesthetic|local anaesthetic]].
Nitrous oxide was not found to be a strong enough anaesthetic for use in major surgery in hospital settings, however. Instead, [[diethyl ether]], being a stronger and more potent anaesthetic, was demonstrated and accepted for use in October 1846, along with [[chloroform]] in 1847.<ref name="Drug discovery" /> When [[Joseph Thomas Clover]] invented the "gas-ether inhaler" in 1876, however, it became a common practice at hospitals to initiate all anaesthetic treatments with a mild flow of nitrous oxide, and then gradually increase the anaesthesia with the stronger ether or chloroform. Clover's gas-ether inhaler was designed to supply the patient with nitrous oxide and ether at the same time, with the exact mixture being controlled by the operator of the device. It remained in use by many hospitals until the 1930s.<ref name="use in dentistry" /> Although hospitals today use a more advanced [[anaesthetic machine]], these machines still use the same principle launched with Clover's gas-ether inhaler, to initiate the anaesthesia with nitrous oxide, before the administration of a more powerful anaesthetic.
===As a patent medicine===
Colton's popularisation of nitrous oxide led to its adoption by a number of less than reputable [[Quackery|quacksalvers]], who touted it as a cure for [[tuberculosis|consumption]], [[Mycobacterial cervical lymphadenitis|scrofula]], [[catarrh]] and other diseases of the blood, throat and lungs. Nitrous oxide treatment was administered and licensed as a [[patent medicine]] by the likes of [[C. L. Blood]] and Jerome Harris in Boston and Charles E. Barney of Chicago.<ref name="alleged">{{cite news|url=https://www.newspapers.com/clip/3461701/alleged_forgery/|title=Alleged Forgery|date=1877-09-28|page=8|author=<!--Staff writers; no byline.-->|newspaper=[[The Inter Ocean]]|access-date=2015-10-26}}</ref><ref name="man">{{cite news|url=https://www.newspapers.com/clip/3461943/dr_blood_and_the_sawtelles/|title=A Man of Ominous Name|date=1890-02-19|author=<!--Staff writers; no byline.-->|newspaper=[[The Inter Ocean]]|access-date=2015-10-26}}</ref>
===Medical===
Line 242 ⟶ 377:
There also have been incidents where nitrous oxide decomposition in plumbing has led to the explosion of large tanks.<ref name="Munke" />
==Environmental impact==
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