Editing Nitrogen (section)

==Applications==
The applications of nitrogen compounds are naturally extremely widely varied due to the huge size of this class: hence, only applications of pure nitrogen itself will be considered here. Two-thirds (2/3) of nitrogen produced by industry is sold as gas and the remaining one-third (1/3) as a liquid.

===Gas{{anchor|Nitrogen_gas}}===
The gas is mostly used as a low reactivity safe atmosphere wherever the oxygen in the air would pose a fire, explosion, or oxidising hazard. Some examples include:<ref name="Greenwood409" />
* As a [[modified atmosphere]], pure or mixed with [[carbon dioxide]], to nitrogenate and preserve the freshness of packaged or bulk foods (by delaying [[Rancidification|rancidity]] and other forms of [[Redox|oxidative damage]]). Pure nitrogen as food additive is labelled in the [[European Union]] with the [[E number]] E941.<ref>{{Cite book | url = https://books.google.com/books?id=Fvm-sqd90-oC&pg=PA591 | page = 591 | title = Food Additives in Europe 2000 | isbn = 978-92-893-0829-8 | year = 2002 | last1 = Ministers | first1 = Nordic Council of | publisher = Nordic Council of Ministers | access-date = 2015-12-20 | archive-date = 2016-02-05 | archive-url = https://web.archive.org/web/20160205191759/https://books.google.com/books?id=Fvm-sqd90-oC&pg=PA591 | url-status = live }}</ref>
* In [[incandescent light bulb]]s as an inexpensive alternative to [[argon]].<ref>{{Cite book|url=https://books.google.com/books?id=W0HW8wgmQQsC&pg=PA90|isbn=978-0-85404-690-4|editor=Harding, Charlie|date=2002|publisher=Royal Society of Chemistry|location=Cambridge|title=Elements of the p Block|access-date=2020-08-24|archive-date=2021-10-01|archive-url=https://web.archive.org/web/20211001035604/https://books.google.com/books?id=W0HW8wgmQQsC&pg=PA90|url-status=live}}</ref>
* In [[Gaseous fire suppression|fire suppression systems for Information technology (IT) equipment]].<ref name="Greenwood409" />
* In the manufacture of [[stainless steel]].<ref>{{Cite book|title=High nitrogen steels: structure, properties, manufacture, applications|author=Gavriliuk, V. G.|author2=Berns, Hans|url=https://books.google.com/books?id=6eF4AfEwF4YC&pg=PA338|publisher=Springer|date=1999|isbn=978-3-540-66411-6|access-date=2020-08-24|archive-date=2021-10-01|archive-url=https://web.archive.org/web/20211001035605/https://books.google.com/books?id=6eF4AfEwF4YC&pg=PA338|url-status=live}}</ref>
* In the [[case-hardening]] of steel by [[nitriding]].<ref name="Duplex">{{cite journal|doi=10.1179/1743284715Y.0000000098|last1=Meka|first1=S. R.|last2=Chauhan|first2=A.|last3=Steiner|first3=T.|last4=Bischoff|first4=E.|last5=Ghosh|first5=P. K.|last6=Mittemeijer|first6=E. J.|year=2015|title=Generating duplex microstructures by nitriding; nitriding of iron based Fe–Mn alloy|page=1743284715Y.000|journal=Materials Science and Technology|volume=32 |issue=9 |doi-access=free}}</ref>
* In some aircraft fuel systems to reduce fire hazard (see [[inerting system]]).
* To inflate race car and aircraft [[tire]]s,<ref>{{cite web|url=http://auto.howstuffworks.com/question594.htm|title=Why don't they use normal air in race car tires?|publisher=Howstuffworks|access-date=2006-07-22|date=2001-03-16|archive-date=2011-07-12|archive-url=https://web.archive.org/web/20110712225925/http://auto.howstuffworks.com/question594.htm|url-status=live}}</ref> reducing the problems of inconsistent expansion and contraction caused by moisture and [[Redox|oxygen]] in natural air.<ref name="Greenwood409" />

Nitrogen is commonly used during sample preparation in [[chemical analysis]]. It is used to concentrate and reduce the volume of liquid samples. Directing a pressurised stream of nitrogen gas perpendicular to the surface of the liquid causes the solvent to evaporate while leaving the solute(s) and un-evaporated solvent behind.<ref>{{Cite journal|doi=10.1016/S0021-9673(01)01466-2|title=Centrifugal concentrator for the substitution of nitrogen blow-down micro-concentration in dioxin/polychlorinated biphenyl sample preparation|year=2002|author=Kemmochi, Y|journal=Journal of Chromatography A|volume=943|pages=295–97|pmid=11833649|last2=Tsutsumi|first2=K.|last3=Arikawa|first3=A.|last4=Nakazawa|first4=H.|issue=2}}</ref>

Nitrogen can be used as a replacement, or in combination with, [[carbon dioxide]] to pressurise kegs of some [[beer]]s, particularly [[stout]]s and British [[ale]]s, due to the smaller [[liquid bubble|bubbles]] it produces, which makes the dispensed beer smoother and [[beer head|headier]].<ref>{{cite book|last1=Baxter|first1=E. Denise|last2=Hughes|first2=Paul S.|title=Beer: Quality, Safety and Nutritional Aspects|date=2001|publisher=Royal Society of Chemistry|isbn=978-0-85404-588-4|page=22|url=https://books.google.com/books?id=X95O-1_x-a0C&pg=PA22|access-date=2015-06-20|archive-date=2020-03-21|archive-url=https://web.archive.org/web/20200321190342/https://books.google.com/books?id=X95O-1_x-a0C&pg=PA22|url-status=live}}</ref> A pressure-sensitive nitrogen capsule known commonly as a "[[widget (beer)|widget]]" allows nitrogen-charged beers to be packaged in [[Beverage can|cans]] and [[bottle]]s.<ref>{{cite web|url=http://recipes.howstuffworks.com/question446.htm|title=How does the widget in a beer can work?|publisher=Howstuffworks|date=2000-08-16|access-date=2008-07-30|archive-date=2007-11-02|archive-url=https://web.archive.org/web/20071102214918/http://recipes.howstuffworks.com/question446.htm|url-status=live}}</ref><ref>{{cite book| url = https://books.google.com/books?id=ogXc9xTTCVsC&pg=PA131| page = 131| title = Froth!: The Science of Beer| isbn = 978-0-8018-9569-2| last1 = Denny| first1 = Mark| date = 1 November 2009| publisher = Johns Hopkins University Press+ORM| access-date = 20 December 2015| archive-date = 5 February 2016| archive-url = https://web.archive.org/web/20160205191759/https://books.google.com/books?id=ogXc9xTTCVsC&pg=PA131| url-status = live}}</ref> Nitrogen tanks are also replacing carbon dioxide as the main power source for [[paintball gun]]s. Nitrogen must be kept at a higher pressure than CO<sub>2</sub>, making N<sub>2</sub> tanks heavier and more expensive.<ref>{{cite thesis| hdl = 1721.1/45820| last=Kennett |first=Andrew J. |title =Design of a pneumatically assisted shifting system for Formula SAE racing applications|year=2008|publisher=Dept. of Mechanical Engineering, Massachusetts Institute of Technology. | type=Thesis }}</ref>

==== Equipment ====
Some construction equipment uses pressurised nitrogen gas to help [[Hydraulics|hydraulic system]] to provide extra power to devices such as [[Breaker (hydraulic)|hydraulic hammer]].  Nitrogen gas, formed from the decomposition of [[sodium azide]], is used for the inflation of [[airbag]]s.<ref>{{cite journal | author = Betterton, E. A. | title = Environmental Fate of Sodium Azide Derived from Automobile Airbags | journal = Critical Reviews in Environmental Science and Technology | year = 2003 | volume = 33 | issue = 4 | pages = 423–58 | doi = 10.1080/10643380390245002 | bibcode = 2003CREST..33..423B | s2cid = 96404307 }}</ref>

==== Execution ====
{{see|Inert gas asphyxiation}}
As nitrogen is an asphyxiant gas in itself, some jurisdictions have considered asphyxiation by inhalation of pure nitrogen as a means of [[capital punishment]] (as a substitute for [[lethal injection]]).<ref name="Time-apr2015">{{cite news |last=Sanburn |first=Josh |url=https://time.com/3749879/nitrogen-gas-execution-oklahoma-lethal-injection/ |title=The Dawn of a New Form of Capital Punishment |magazine=[[Time (magazine)|Time]] |date=2015-04-10 |access-date=2015-04-11 |archive-date=2015-04-11 |archive-url=https://web.archive.org/web/20150411201357/http://time.com/3749879/nitrogen-gas-execution-oklahoma-lethal-injection/ |url-status=live }}</ref><ref>{{cite news |url=http://www.abc.net.au/7.30/content/2012/s3657550.htm |title=Euthanasia campaigner under scrutiny |author=Sexton, Mike |date=18 December 2012 |work=[[ABC News (Australia)|ABC]] |access-date=6 May 2013 |archive-date=7 July 2013 |archive-url=https://web.archive.org/web/20130707143023/http://www.abc.net.au/7.30/content/2012/s3657550.htm |url-status=live }}</ref><ref>{{Cite news|url=https://www.washingtonpost.com/news/post-nation/wp/2015/04/17/oklahoma-says-it-will-now-use-nitrogen-gas-as-its-backup-method-of-execution/|title=Oklahoma says it will now use nitrogen gas as its backup method of execution|last=Berman|first=Mark|date=April 17, 2015|newspaper=The Washington Post|access-date=June 22, 2019|archive-date=June 23, 2019|archive-url=https://web.archive.org/web/20190623024008/https://www.washingtonpost.com/news/post-nation/wp/2015/04/17/oklahoma-says-it-will-now-use-nitrogen-gas-as-its-backup-method-of-execution/|url-status=live}}</ref> In January 2024, [[Execution of Kenneth Eugene Smith|Kenneth Eugene Smith]] became the first person executed by nitrogen asphyxiation.<ref>{{cite web |title=Kenneth Eugene Smith executed by nitrogen hypoxia in Alabama, marking a first for the death penalty |url=https://www.cbsnews.com/news/kenneth-eugene-smith-executed-by-nitrogen-hypoxia-in-alabama/ |publisher=[[CBS News]] |date=26 January 2024}}</ref>

===Liquid===
{{main |Liquid nitrogen}}
[[File:Nitrogen.ogv|thumb|Air balloon submerged in liquid nitrogen]]
Liquid nitrogen is a [[cryogen|cryogenic liquid]] which looks like [[water]]. When insulated in proper containers such as [[dewar flask]]s, it can be transported and stored with a low rate of [[evaporation|evaporative loss]].<ref>{{Cite journal|doi=10.1007/BF01136404|title=Vessels for the storage and transport of liquid oxygen and nitrogen|author=Kaganer, M. G.|author2=Kozheurov, V.|author3=Levina, Zh. L.|name-list-style=amp|journal=Chemical and Petroleum Engineering|volume=3|issue=12|year=1967|pages=918–22|bibcode=1967CPE.....3..918K |s2cid=96762552}}</ref>
[[File:A cylinder container, containing liquid nitrogen.jpg|thumb|A container vehicle carrying liquid nitrogen]]

Like [[dry ice]], the main use of liquid nitrogen is for cooling to low temperatures. It is used in the [[cryopreservation]] of biological materials such as blood and reproductive cells ([[sperm]] and [[ovum|eggs]]). It is used in [[cryotherapy]] to remove cysts and warts on the skin by freezing them.<ref>{{cite journal|pmid=11359389|volume=144|issue=5|title=Liquid nitrogen cryotherapy of common warts: cryo-spray vs. cotton wool bud|date=May 2001|journal=Br. J. Dermatol.|pages=1006–09|author=Ahmed I|author2=Agarwal S|author3=Ilchyshyn A|author4=Charles-Holmes S|author5=Berth-Jones J|doi=10.1046/j.1365-2133.2001.04190.x|s2cid=221325640}}</ref> It is used in laboratory [[cold trap]]s, and in [[cryopump]]s to obtain lower pressures in [[vacuum pump]]ed systems. It is used to cool heat-sensitive electronics such as [[infrared detector]]s and [[X-ray detector]]s. Other uses include freeze-grinding and machining materials that are soft or rubbery at room temperature, shrink-fitting and assembling engineering components, and more generally to attain very low temperatures where necessary. Because of its low cost, liquid nitrogen is often used for cooling even when such low temperatures are not strictly necessary, such as refrigeration of food, [[freeze-branding]] livestock, freezing pipes to halt flow when valves are not present, and consolidating unstable soil by freezing whenever excavation is going on underneath.<ref name="Greenwood409" />