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<!-- [[File:Liquidnitrogen.jpg|thumb|Liquid nitrogen]] |
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[[File:Liquid-nitrogen-demo-freeside-atlanta.webm|thumb|A demonstration of liquid nitrogen at the Freeside maker space in Atlanta, Georgia during the Online News Association conference in 2013]] |
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[[Image:Nitrogen ice cream 0020.jpg|thumb|Students preparing homemade [[ice cream]] with a [[Cryogenic storage dewar|dewar]] of liquid nitrogen]] |
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'''Liquid nitrogen'''—'''LN<sub>2</sub>'''—is [[nitrogen]] in a liquid state at low temperature. Liquid nitrogen has a boiling point of about {{convert|-196|C|F K|0}}. It is produced industrially by [[fractional distillation]] of [[liquid air]]. It is a colorless, mobile [[liquid]] whose [[viscosity]] is about one tenth that of [[acetone]] (i.e. roughly one thirtieth that of room temperature water). Liquid nitrogen is widely used as a [[coolant]]. |
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== Physical properties == |
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The diatomic character of the N<sub>2</sub> molecule is retained after [[liquefaction]]. The weak [[van der Waals interaction]] between the N<sub>2</sub> molecules results in little interatomic attraction. This is the cause of nitrogen's unusually low [[boiling point]].<ref>{{cite journal|author1=Henshaw, D. G. |author2=Hurst, D. G. |author3= Pope, N. K. |year=1953|title= Structure of Liquid Nitrogen, Oxygen, and Argon by Neutron Diffraction|journal= Physical Review|volume=92|issue=5 |pages= 1229–1234|doi=10.1103/PhysRev.92.1229|bibcode=1953PhRv...92.1229H}}</ref> |
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The temperature of liquid nitrogen can readily be reduced to its freezing point {{convert|-210|C|F K|0}} by placing it in a vacuum chamber pumped by a [[vacuum pump]].<ref name=Umrath>{{cite journal|author=Umrath, W. |year=1974|title= Cooling bath for rapid freezing in electron microscopy|journal= Journal of Microscopy |volume=101|pages= 103–105|doi=10.1111/j.1365-2818.1974.tb03871.x|s2cid=96286845}}</ref> Liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in an insulating layer of nitrogen gas bubbles. This effect, known as the [[Leidenfrost effect]], occurs when any liquid comes in contact with a surface which is significantly hotter than its boiling point. Faster cooling may be obtained by plunging an object into a slush of liquid and [[solid nitrogen]] rather than liquid nitrogen alone.<ref name=Umrath/> |
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==Handling== |
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As a [[cryogenic]] fluid that rapidly [[freezing|freezes]] living tissue, its handling and storage require [[thermal insulation]]. It can be stored and transported in [[Cryogenic storage dewar|vacuum flasks]], the temperature being held constant at 77 K by slow boiling of the liquid. Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks. The development of pressurised super-insulated vacuum vessels has enabled liquid nitrogen to be stored and transported over longer time periods with losses reduced to 2% per day or less.<ref>[http://www.aspenycap.org/files/CryogenicGases.pdf DATA BOOK for Cryogenic Gases and Equipment] {{Webarchive|url=https://web.archive.org/web/20140517152825/http://www.aspenycap.org/files/CryogenicGases.pdf |date=2014-05-17}}. aspenycap.org</ref> |
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==Uses== |
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Liquid nitrogen is a compact and readily transported source of dry nitrogen gas, as it does not require pressurization. Further, its ability to maintain temperatures far below the [[freezing point]] of water, [[specific heat]] of 1040[[joule|j]]⋅kg<sup>-1</sup>[[kelvin|⋅k]]<sup>-1</sup> and [[heat of vaporization]] of 200kj⋅kg<sup>-1</sup> makes it extremely useful in a wide range of applications, primarily as an open-cycle [[refrigerant]], including: |
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*in [[cryotherapy]] for removing unsightly or potentially [[skin cancer|malignant]] skin lesions such as [[wart]]s and [[actinic keratosis]] |
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*to store cells at low temperature for laboratory work |
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*in [[cryogenics]] |
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*in a [[cryophorus]] to demonstrate rapid freezing by [[evaporation]] |
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*as a backup nitrogen source in [[hypoxic air fire prevention system]]s |
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*as a source of very dry [[nitrogen]] gas |
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*for the immersion, freezing, and transportation of food products |
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*for the [[cryopreservation]] of [[blood]], reproductive cells ([[sperm]] and [[ovum|egg]]), and other [[biology|biological]] samples and materials |
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**to preserve tissue samples from surgical excisions for future studies |
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**to facilitate [[cryoconservation of animal genetic resources]] |
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*to freeze water and oil pipes in order to work on them in situations where a valve is not available to block fluid flow to the work area; this method is known as a cryogenic isolation |
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*for [[cryonics|cryonic preservation]] in hopes of future reanimation |
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*for [[shrink-fitting]] machinery parts together |
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*as a coolant |
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**for [[Charge-coupled device#Use in astronomy|CCD]] cameras in [[astronomy#Optical astronomy|astronomy]] |
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**for a [[high-temperature superconductor]] to a temperature sufficient to achieve [[superconductivity]] |
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**to maintain a low temperature around the primary [[liquid helium]] cooling system of high-field [[superconducting magnet]]s used in e.g. [[Nuclear magnetic resonance spectroscopy|nuclear magnetic resonance spectrometers]] and [[magnetic resonance imaging]] systems |
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**for [[vacuum pump]] traps and in [[rotovap|controlled-evaporation processes]] in chemistry |
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**as a component of [[cooling bath]]s used for very low temperature reactions in chemistry |
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**to increase the sensitivity of [[infrared homing]] seeker heads of missiles such as the [[Strela 3]] |
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**to temporarily shrink mechanical components during machine assembly and allow improved [[interference fit]]s |
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**for [[computers]] and extreme [[overclocking]]<ref>{{cite book|title = The Book of Overclocking: Tweak Your PC to Unleash Its Power|first = Scott|last = Wainner|author2 = Richmond, Robert|pages = [https://archive.org/details/bookofoverclocki0000wain/page/44 44]|isbn = 1-886411-76-X|publisher = No Starch Press|year = 2003|url-access = registration|url = https://archive.org/details/bookofoverclocki0000wain/page/44}}</ref> |
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**for simulation of space background in vacuum chamber during [[spacecraft]] thermal testing<ref>{{cite book|title = Satellite Thermal Control for System Engineers|author = Karam, Robert D. |page = 89|isbn = 1-56347-276-7|publisher = AIAA|year = 1998}}</ref> |
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**to control the temperature of [[mass concrete]], injected to precool [[concrete]] mixes during delivery <ref name="ACI" >ACI Committee 207 – Report on Cooling and |
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Insulating Systems for |
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Mass Concrete</ref> |
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*in food preparation, such as for making ultra-smooth [[ice cream]].<ref>[http://www.101cookbooks.com/archives/001366.html Liquid Nitrogen Ice Cream Recipe] {{Webarchive|url=https://web.archive.org/web/20091220011539/http://www.101cookbooks.com/archives/001366.html |date=2009-12-20 }}, March 7, 2006</ref> See also [[molecular gastronomy]]. |
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*in container inerting and pressurisation by injecting a controlled amount of liquid nitrogen just prior to sealing or capping<ref>[http://www.vacuumbarrier.com/Articles/LiquidNitrogenDosing.html Liquid nitrogen – how to dose effectively] {{Webarchive|url=https://web.archive.org/web/20130616102617/http://www.vacuumbarrier.com/Articles/LiquidNitrogenDosing.html |date=2013-06-16 }}, June 19, 2012</ref><ref>[http://www.chartdosers.com/products/dosing.html Chart Dosers Dosing Products] {{Webarchive|url=https://web.archive.org/web/20130304185941/http://www.chartdosers.com/products/dosing.html |date=2013-03-04 }}, June 19, 2012</ref> |
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*as a cosmetic novelty giving a smoky, bubbling "cauldron effect" to drinks. See [[liquid nitrogen cocktail]]. |
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*as an energy storage medium<ref>{{Cite web |title=Liquid air 'offers energy storage hope' |author=Harrabin, Roger |date=2 October 2012 |publisher=BBC |url=https://www.bbc.co.uk/news/science-environment-19785689 |access-date=22 June 2018 |archive-date=16 February 2019 |archive-url=https://web.archive.org/web/20190216013326/https://www.bbc.co.uk/news/science-environment-19785689 |url-status=live }}</ref><ref>{{Cite web |title=Frozen Air Batteries Could Store Wind Energy for Peak Demand |author=Markham, Derek |date=October 3, 2012 |work=Treehugger |publisher=Discovery Communications |url=http://www.treehugger.com/wind-technology/liquid-air-battery-could-provide-renewable-energy-storage.html |access-date=October 22, 2012 |archive-date=November 5, 2012 |archive-url=https://web.archive.org/web/20121105082357/http://www.treehugger.com/wind-technology/liquid-air-battery-could-provide-renewable-energy-storage.html |url-status=live }}</ref> |
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*in [[Freeze brand|freeze branding cattle]]<ref>{{cite web |title=Freeze-branding cattle |first= Ted G. |last= Dyer |date= February 2010|url=http://extension.uga.edu/publications/files/pdf/C%20904_2.PDF }}{{Dead link|date=November 2020}}</ref> |
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* In [[tunnel construction]] to stabilize unstable and loose terrains, liquid nitrogen injected into soil to freeze the water present in the soil. With increased [[bearing capacity]] and [[Permeability (Earth sciences) | impermeability]], the improved ground will not collapse during excavation and subsequent works.<ref>{{Cite web |title=Soil Freezing |url=https://bauerfoundations.com/en/construction_methods/soil-freezing/}}</ref> |
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===Culinary=== |
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{{see also|Ice cream#Cryogenics}} |
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The culinary use of liquid nitrogen is mentioned in an 1890 recipe book titled ''Fancy Ices'' authored by [[Agnes Marshall]],<ref name=BBCMag-2012-10-09>{{cite news |url=https://www.bbc.co.uk/news/magazine-19870668 |work=BBC News |title=Who What Why: How dangerous is liquid nitrogen? |date=9 October 2012 |access-date=9 October 2012 |archive-date=9 October 2012 |archive-url=https://web.archive.org/web/20121009185738/http://www.bbc.co.uk/news/magazine-19870668 |url-status=live}}</ref> but has been employed in more recent times by restaurants in the preparation of frozen desserts, such as ice cream, which can be created within moments at the table because of the speed at which it cools food.<ref name=BBCMag-2012-10-09/> The rapidity of chilling also leads to the formation of smaller ice crystals, which provides the dessert with a smoother texture.<ref name=BBCMag-2012-10-09/> The technique is employed by chef [[Heston Blumenthal]] who has used it at his restaurant, [[The Fat Duck]], to create frozen dishes such as egg and bacon ice cream.<ref name=BBCMag-2012-10-09/><ref name=Telegraph-2012-10-09>{{cite news|first=Harry |last=Wallop |url=https://www.telegraph.co.uk/health/9594206/The-dark-side-of-liquid-nitrogen-cocktails.html |archive-url=https://web.archive.org/web/20121010134217/http://www.telegraph.co.uk/health/9594206/The-dark-side-of-liquid-nitrogen-cocktails.html |url-status=dead |archive-date=10 October 2012 |title=The dark side of liquid nitrogen cocktails |newspaper=The Daily Telegraph |date=9 October 2012 |access-date=12 October 2012}}</ref> Liquid nitrogen has also become popular in the preparation of [[Liquid nitrogen cocktail|cocktail]]s because it can be used to quickly chill glasses or freeze ingredients.<ref name=Newsbeat-2012-10-08/> It is also added to drinks to create a smoky effect, which occurs as tiny droplets of the liquid nitrogen come into contact with the surrounding air, condensing the vapour that is naturally present.<ref name=Newsbeat-2012-10-08>{{cite news |last=Gladwell |first=Amy |url=http://www.bbc.co.uk/newsbeat/19866191 |work=Newsbeat |title=Teenager's stomach removed after drinking cocktail |publisher=BBC |date=9 October 2012 |access-date=9 October 2012 |archive-date=9 October 2012 |archive-url=https://web.archive.org/web/20121009015001/http://www.bbc.co.uk/newsbeat/19866191 |url-status=live}}</ref> |
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==History== |
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Nitrogen was first liquefied at the [[Jagiellonian University]] on 15 April 1883 by Polish physicists [[Zygmunt Wróblewski]] and [[Karol Olszewski]].<ref>{{cite book|url=https://books.google.com/books?id=8SKrWdFLEd4C&pg=PA249|page=249|title=A Short History of the Progress of Scientific Chemistry in Our Own Times|author=Tilden, William Augustus|publisher=BiblioBazaar, LLC|year=2009|isbn=978-1-103-35842-7|access-date=2016-02-28|archive-date=2013-12-31|archive-url=https://web.archive.org/web/20131231162459/http://books.google.com/books?id=8SKrWdFLEd4C&pg=PA249|url-status=live}}</ref> |
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==Safety== |
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[[File:Liquid Nitrogen Tank.JPG|thumb|Filling a liquid nitrogen [[Dewar flask|Dewar]] from a storage tank]] |
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Because the liquid-to-gas [[expansion ratio]] of nitrogen is 1:694 at {{Convert|20|C|F|0}}, a tremendous amount of force can be generated if liquid nitrogen is vaporized in an enclosed space. In an incident on January 12, 2006 at [[Texas A&M University]], the pressure-relief devices of a tank of liquid nitrogen were malfunctioning and later sealed. As a result of the subsequent pressure buildup, the tank failed catastrophically. The force of the explosion was sufficient to propel the tank through the ceiling immediately above it, shatter a reinforced concrete beam immediately below it, and blow the walls of the laboratory 0.1–0.2 m off their foundations.<ref>{{cite web|title = Investigative Report on Chemistry 301A Cylinder Explosion|author = Mattox, Brent S.|publisher = Texas A&M University|format = reprint|url = http://ucih.ucdavis.edu/docs/chemistry_301a.pdf|archive-url = https://web.archive.org/web/20081031073557/http://ucih.ucdavis.edu/docs/chemistry_301a.pdf|url-status = dead|archive-date = 2008-10-31}}</ref> In January 2021, a line carrying liquid nitrogen ruptured at a poultry processing plant in the U.S. state of Georgia, killing six people and injuring 11 others.<ref name="NYTimes_20210128">{{cite news |last1=Fausset |first1=William |last2=Levenson |first2=Michael |date=January 28, 2021 |title=6 Die After Liquid Nitrogen Leak at Georgia Poultry Plant |url=https://www.nytimes.com/2021/01/28/us/foundation-food-group-liquid-nitrogen-plant.html |url-status=live |archive-url=https://web.archive.org/web/20210129183405/https://www.nytimes.com/2021/01/28/us/foundation-food-group-liquid-nitrogen-plant.html |archive-date=January 29, 2021 |work=The New York Times}}</ref> |
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Because of its extremely low temperature, careless handling of liquid nitrogen and any objects cooled by it may result in [[cold burn]]s. In that case, special gloves should be used while handling. However, a small splash or even pouring down skin will not burn immediately because of the [[Leidenfrost effect]], the evaporating gas thermally insulates to some extent, like touching a hot element very briefly with a wet finger. If the liquid nitrogen manages to pool anywhere, it will burn severely. |
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As liquid nitrogen evaporates it reduces the [[oxygen]] concentration in the [[air]] and can act as an [[asphyxiant gas|asphyxiant]], especially in [[confined space]]s. Nitrogen is odorless, colorless, and tasteless and may produce [[asphyxia]] without any sensation or prior warning.<ref name=BCGACOPCP30>British Compressed Gases Association (2000) BCGA Code of Practice CP30. [http://www.bcga.co.uk/preview/products.php?g1=3ff921&n=2 The Safe Use of Liquid nitrogen Dewars up to 50 litres.] {{webarchive|url=https://web.archive.org/web/20070718050900/http://www.bcga.co.uk/preview/products.php?g1=3ff921&n=2 |date=2007-07-18 }} ISSN 0260-4809.</ref><ref>[http://www.csb.gov/assets/1/19/Valero_Case_Study.pdf Confined Space Entry - Worker and Would-be Rescuer Asphyxiated] {{Webarchive|url=https://web.archive.org/web/20170829054938/http://www.csb.gov/assets/1/19/Valero_Case_Study.pdf |date=2017-08-29}}, Valero Refinery Asphyxiation Incident Case Study.</ref><ref>[http://news.bbc.co.uk/2/hi/uk_news/scotland/484813.stm Inquiry after man dies in chemical leak] {{Webarchive|url=https://web.archive.org/web/20170107063950/http://news.bbc.co.uk/2/hi/uk_news/scotland/484813.stm |date=2017-01-07}}, BBC News, {{#dateformat:October 25, 1999}}.</ref> |
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[[Oxygen sensor]]s are sometimes used as a safety precaution when working with liquid nitrogen to alert workers of gas spills into a confined space.<ref name="usn">{{Cite book |title=Liquid Nitrogen – Code of practice for handling |year=2007 |publisher=Birkbeck, University of London |location=United Kingdom |url=http://www.bbk.ac.uk/so/policies/liqn2 |access-date=2012-02-08 |archive-date=2018-06-12 |archive-url=https://web.archive.org/web/20180612141434/http://www.bbk.ac.uk/so/policies/liqn2 |url-status=live }}</ref> |
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Vessels containing liquid nitrogen can [[liquid oxygen|condense oxygen]] from air. The liquid in such a vessel becomes increasingly enriched in oxygen (boiling point {{Convert|90|K|C F|sigfig=3|disp=x|; }}) as the nitrogen evaporates, and can cause violent oxidation of organic material.<ref>{{Cite web|title = Liquid Nitrogen Safety|author = Levey, Christopher G.|publisher = Thayer School of Engineering at Dartmouth|url = http://engineering.dartmouth.edu/microeng/ln2.html|access-date = 2012-06-23|archive-date = 2016-03-05|archive-url = https://web.archive.org/web/20160305020126/http://engineering.dartmouth.edu/microeng/ln2.html|url-status = live}}</ref> |
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Ingestion of liquid nitrogen can cause severe internal damage, due to freezing of the tissues which come in contact with it and to the volume of gaseous nitrogen evolved as the liquid is warmed by body heat. In 1997, a physics student demonstrating the Leidenfrost effect by holding liquid nitrogen in his mouth accidentally swallowed the substance, resulting in near-fatal injuries. This was apparently the first case in medical literature of liquid nitrogen ingestion.<ref>{{cite web|title=Student Gulps Into Medical Literature |url=http://www.wpi.edu/news/19989/nitro.html |publisher=[[Worcester Polytechnic Institute]] |access-date=11 October 2014 |date=20 January 1999 |archive-url=https://web.archive.org/web/20140222192214/http://www.wpi.edu/news/19989/nitro.html |archive-date=22 February 2014 |url-status=dead }}</ref> In 2012, a young woman in England had her stomach removed after ingesting a cocktail made with liquid nitrogen.<ref>[https://www.bbc.co.uk/news/uk-19878511 Liquid nitrogen cocktail leaves teen in hospital] {{Webarchive|url=https://web.archive.org/web/20170412232656/http://www.bbc.co.uk/news/uk-19878511 |date=2017-04-12}}, BBC News, {{#dateformat:October 8, 2012}}.</ref> |
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==Production== |
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{{main article|Air separation}} |
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Liquid nitrogen is produced commercially from the cryogenic [[distillation]] of [[liquid air|liquified air]] or from the liquefaction of pure nitrogen derived from air using [[pressure swing adsorption]]. An [[air compressor]] is used to compress filtered air to high pressure; the high-pressure gas is cooled back to ambient temperature, and allowed to expand to a low pressure. The expanding air cools greatly (the [[Joule–Thomson effect]]), and oxygen, nitrogen, and argon are separated by further stages of expansion and distillation. Small-scale production of liquid nitrogen is easily achieved using this principle.{{citation needed|date=December 2016}} Liquid nitrogen may be produced for direct sale, or as a byproduct of manufacture of liquid oxygen used for industrial processes such as [[steelmaking]]. Liquid-air plants producing on the order of tons per day of product started to be built in the 1930s but became very common after the Second World War; a large modern plant may produce 3000 tons/day of liquid air products.<ref>Almqvist, Ebbe (2003) ''History of Industrial Gases'', Springer, {{ISBN|0306472775}} p. 163</ref> |
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==See also== |
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*[[Liquefaction of gases]] |
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*[[Industrial gas]] |
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*[[Computer cooling]] |
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*[[Cryogenic nitrogen plant]] |
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*[[Liquid nitrogen engine]] |
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==References== --> |
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{{chladiva}} |
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[[Kategorie:Dusík]] |
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[[Kategorie:Chladiva]] |
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Verze z 4. 5. 2024, 18:49
