Nitrous oxide 37441 225731623 2008-07-15T03:25:43Z Husond 1732934 Reverted edits by [[Special:Contributions/72.91.72.29|72.91.72.29]] to last version by 24.16.92.48 (using [[WP:HG|Huggle]]) {{Citations missing|article|date=July 2007}} {{cleanup-rewrite|Confusing and disorganized (repetitious)|article}} {{chembox new | ImageFile = Nitrous-oxide-3D-vdW.png | ImageSize = 150px | ImageName = Nitrous oxide - space-filling model | ImageFile1 = Nitrous-oxide-dimensions-3D-balls.png | ImageSize1 = 200px | ImageName1 = Nitrous oxide's bond lengths | ImageFile2 = Nitrous-oxide-2D-VB.png | ImageSize2 = 250px | ImageName2 = Nitrous oxide's canonical forms | IUPACName = | SystematicName = | OtherNames = | Section1 = {{Chembox Identifiers | Abbreviations = | CASNo = 10024-97-2 | EINECS = | EINECSCASNO = | PubChem = | SMILES = [N+]([O-])#N | InChI = | RTECS = | MeSHName = | ChEBI = | KEGG = | ATCCode_prefix = N01 | ATCCode_suffix = AX13 | ATC_Supplemental =}} | Section2 = {{Chembox Properties | Formula = N<sub>2</sub>O | MolarMass = 44.0128 g/mol | Appearance = colourless gas | Density = 1222.8 kg m<sup>-3</sup> (liquid)<br />1.8 kg m<sup>-3</sup> (gas STP) | MeltingPt = -90.86 °C (182.29 K) | Melting_notes = | BoilingPt = -88.48 °C (184.67 K) | Boiling_notes = | Solubility = | SolubleOther = | Solvent = | LogP = | VaporPressure = | HenryConstant = | AtmosphericOHRateConstant = | pKa = | pKb = }} | Section3 = {{Chembox Structure | CrystalStruct = | SpaceGroup = | Coordination = | LattConst_a = | LattConst_b = | LattConst_c = | LattConst_alpha = | LattConst_beta = | LattConst_gamma = | MolShape = linear | OrbitalHybridisation = | Dipole = 0.166[[Debye|D]]}} | Section4 = {{Chembox Thermochemistry | DeltaHf = +82.05 | DeltaHc = | Entropy = | HeatCapacity = }} | Section5 = {{Chembox Pharmacology | AdminRoutes = [[Inhalation]] | Bioavail = | Metabolism = 0.004% | HalfLife = 5 minutes | ProteinBound = | Excretion = [[Respiratory]] | Legal_status = Anesthetic use allowed in the [[United States]] and [[Australia]]; Recreational use often illegal on a state-by-state basis | Legal_US = | Legal_UK = | Legal_AU = | Legal_CA = | PregCat = | PregCat_AU = | PregCat_US = }} | Section6 = {{Chembox Explosive | ShockSens = | FrictionSens = | ExplosiveV = | REFactor = }} | Section7 = {{Chembox Hazards | EUClass = | EUIndex = | MainHazards = | NFPA-H = 2 | NFPA-F = 0 | NFPA-R = 0 | NFPA-O = Ox | RPhrases = {{R8}} | SPhrases = {{S38}} | RSPhrases = | FlashPt = | Autoignition = | ExploLimits = | LD50 = | PEL = }} | Section8 = {{Chembox Related | OtherAnions = | OtherCations = | OtherFunctn = | Function = | OtherCpds =[[Nitric oxide]], [[nitrogen dioxide]], [[dinitrogen trioxide]], [[dinitrogen tetroxide]], [[dinitrogen pentoxide]], [[nitric acid]], [[nitrous acid]]}} }} '''Nitrous oxide''' (aka '''laughing gas''', '''funny gas''', '''nitrogen suboxide''', or '''dinitrogen monoxide''') is a [[chemical compound]] with the [[chemical formula]] [[Nitrogen|N]]<sub>2</sub>[[Oxygen|O]]. At room temperature, it is a colorless [[Flammability|non-flammable]] [[gas]], with a pleasant, slightly sweet odor and taste. It is used in [[surgery]] and [[dentistry]] for its [[Anesthesia|anesthetic]] and [[analgesic]] effects. It is commonly known as "laughing gas" due to the euphoric effects of inhaling it, a property that has led to its recreational use as an [[inhalant]] drug. It is also used in [[Auto racing|motor racing]] as an [[Oxidizing agent|oxidizer]] to increase the power output of [[Piston engine|engines]]. == Occurrence == [[Image:Major greenhouse gas trends.png|thumb|left|200px|Greenhouse gas trends.]] ''More info on [[nitrogen oxide]]s''.<br> Nitrous oxide, unlike other oxides (apart from carbon dioxide), is a major [[greenhouse gas]]. While its radiative warming effect is substantially less than CO<sub>2</sub>, nitrous oxide's persistence in the atmosphere, when considered over a 100 year period, per unit of weight, has 310 times more impact on [[global warming]] than that per mass unit of [[carbon dioxide]] (CO<sub>2</sub>).<ref>{{cite web | url = http://www.grida.no/climate/ipcc_tar/wg1/248.htm | title = Climate Change 2001: Working Group I: The Scientific Basis : | publisher = Intergovernmental Panel on Climate Change | accessdate = 2008-02-02 | date = }}</ref> Control of nitrous oxide is part of efforts to curb greenhouse gas emissions, which is part of the [[Kyoto Protocol]]. Despite its relatively small concentration in the atmosphere, nitrous oxide is the fourth largest greenhouse gas contributor to overall global warming, behind [[carbon dioxide]], [[methane]] and water vapour. (The other nitrogen oxides contribute to global warming indirectly, by contributing to tropospheric ozone production during smog formation). Nitrous oxide is emitted by [[bacteria]] in soils and oceans, and thus has been a part of Earth's atmosphere for [[Eon (geology)| aeons]]. Agriculture is the main source of human-produced nitrous oxide: cultivating soil, the use of [[nitrogen fertilizer]]s, and animal waste handling can all stimulate naturally occurring bacteria to produce more nitrous oxide. The livestock sector (primarily cows, chickens, and pigs) produces 65% of human-related nitrous oxide. <ref>{{cite web | url = http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm | title = Livestock’s long shadow -- Environmental issues and options | publisher = | author = H. Steinfeld, P. Gerber, T. Wassenaar, V. Castel, M. Rosales, C. de Haan | accessdate = 2008-02-02 | date = 2006 }}</ref> Industrial sources make up only about 20% of all anthropogenic sources, and include the production of [[nylon]] and nitric acid, and the burning of fossil fuel in internal combustion engines. Human activity is thought to account for somewhat less than 2&nbsp;[[tera]]grams of nitrogen oxides per year, nature for over 15&nbsp;teragrams.<ref>{{cite web | url = http://www.epa.gov/nitrousoxide/sources.html | title = Sources and Emissions -- Where Does Nitrous Oxide Come From? | publisher = U. S. Environmental Protection Agency | author = | accessdate = 2008-02-02 | date = 2006 }}</ref> The global anthropogenic nitrous oxide flux is about 1&nbsp;petagram of carbon dioxide carbon-equivalents per year; this compares to 2&nbsp;petagrams of methane carbon dioxide carbon-equivalents per year, and to an atmospheric loading rate of about 3.3&nbsp;petagrams of carbon dioxide carbon-equivalents per year. Nitrous oxide reacts with [[ozone]] in the [[stratosphere]]. Nitrous oxide is the main naturally occurring regulator of stratospheric ozone. Recent research by Nobel Laureate [[Paul Crutzen]] suggests that emissions of nitrous oxide in the production of biofuels are more than enough to offset the advantages that biodiesel was hoped to have in terms of [[carbon dioxide]] emissions.<ref>{{cite journal | url = http://meteo.lcd.lu/globalwarming/Crutzen/biofuels_NO2_release_2007.pdf | title = N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels | journal = Atmos. Chem. Phys. Discuss., | author = P. J. Crutzen, A. R. Mosier, K. A. Smith, and W. Winiwarter | accessdate = 2008-02-02 | date = 2007 | volume = 7 | pages = 11191–11205 }}</ref> Carbon dioxide released during biofuel combustion is considered in fact neutral and thus its contribution as greenhouse gas neglected. The reason is that during the growing phase of the crop utilized for producing the biofuel an equal amount of carbon dioxide is sequestrated from the atmosphere. ==Manufacture== Nitrous oxide is most commonly prepared by careful heating of [[ammonium nitrate]], which decomposes into nitrous oxide and water vapor.<ref>{{cite book | last = Holleman | first = A. F. | coauthors = Wiberg, E. | title = Inorganic Chemistry | publisher = Academic Press | location = San Diego | year = 2001 | doi = | isbn = 0-12-352651-5}}</ref> One of the earliest commercial producers was [[George Poe]] in [[Trenton, New Jersey]].<ref name=wp>{{cite news |first= |last= |authorlink= |coauthors= |title=George Poe is Dead |url=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 |quote=Cousin of Famous Poet and Noted as a Scientist. Inventor of the Respirator. Also First to Liquefy Nitrous Oxide. Cadet at [[Virginia Military Institute]] at Time of [[Battle of Newmarket]]. Mentioned for the Nobel Prize for Scientific Attainment in Chemistry. Prof. George Poe, a cousin of the poet Edgar Allan Poe, a noted scientist and inventor, who had been mentioned for the Nobel prize for scientific attainment, a former resident of Washington, died in Norfolk, Virginia, yesterday of general paralysis. Prof. Poe was in his sixty-eighth year. |publisher=[[Washington Post]] |date=[[February 3]], [[1914]] |accessdate=2007-12-29 }}</ref> :NH<sub>4</sub>NO<sub>3</sub>(s) → 2 H<sub>2</sub>O(g) + N<sub>2</sub>O(g) The addition of various [[phosphate]]s favors formation of a purer gas at slightly lower temperatures. This reaction occurs between 170 - 240°C, temperatures where ammonium nitrate is a moderately sensitive [[explosive]] and a very powerful [[oxidizer]]. At temperatures much above 240&nbsp;°C the [[exothermic reaction]] may accelerate to the point of [[detonation]]. The mixture must be cooled to avoid such a disaster. In practice, the reaction involves a series of tedious adjustments to control the temperature to within a narrow range. Professionals have destroyed whole neighborhoods by losing control (of the ''temperature and pressure'' in the ammonium nitrate retorts) in commercial scale processes. Examples include the Ohio Chemical debacle in [[Montreal]], 1966 and the Air Products & Chemicals, Inc. disaster in [[Delaware City, Delaware]], 1977. Superheated steam is used to reach reaction temperature in some turnkey production plants.<ref>{{cite web | url = http://www.sanghioverseas.com/nitrous_oxide_gas_plants/nitrous_oxide_gas_plants.htm | publisher = Sanghi Organization | title = Nitrous oxide plant}}</ref> Downstream, the hot, corrosive mixture of gases must be cooled to condense the steam and filtered to remove higher oxides of nitrogen. Also ammonium nitrate smoke, in an extremely persistent colloid will likely have to be removed. The cleanup is often done in a train of 3 gas washes; namely base, acid and base again. Any significant amounts of nitric oxide (NO) may not necessarily be absorbed directly by the base (sodium hydroxide) washes. The nitric oxide impurity is sometimes chelated out with [[ferrous sulfate]], reduced with iron metal, or oxidised and absorbed in base as a higher oxide. The first base wash may (or may not) react out much of the ammonium nitrate smoke, however this reaction generates ammonia gas, which may have to be absorbed in the acid wash. The direct oxidation of [[ammonia]] may someday rival the ammonium nitrate [[pyrolysis]] synthesis of nitrous oxide mentioned above. This capital-intensive process, which originates in Japan, uses a [[manganese dioxide]]-[[bismuth oxide]] catalyst:<ref>Synthesis of Nitrous Oxide by Oxidation of Ammonia T Suwa, A Matsushima, Y Suziki, Y Namina - Kohyo Kagaku Zasshi, 1961; Showa Denka Ltd.</ref> :2 NH<sub>3</sub> + 2 O<sub>2</sub> → N<sub>2</sub>O + 3 H<sub>2</sub>O Higher oxides of nitrogen are formed as impurities. In comparison, [[catalysis|uncatalyzed]] ammonia oxidation (i.e. combustion or explosion) goes primarily to N<sub>2</sub> and H<sub>2</sub>O. Nitrous oxide can be made by heating a solution of [[sulfamic acid]] and [[nitric acid]]. A lot of gas was made this way in Bulgaria.{{Fact|date=February 2008}}<ref>Brozadzhiew & Rettos, 1975.</ref> :HNO<sub>3</sub> + NH<sub>2</sub>SO<sub>3</sub>H → N<sub>2</sub>O + H<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O There is no explosive hazard in this reaction if the mixing rate is controlled. However, as usual, toxic higher oxides of nitrogen form. Nitrous oxide is produced in large volumes as a by-product in the synthesis of [[adipic acid]]; one of the two reactants used in nylon manufacture.<ref>{{cite journal | title = Abatement of N<sub>2</sub>O emissions produced in the adipic acid industry | author = Reimer R. A.; Slaten C. S.; Seapan M.; Lower M. W.; Tomlinson P. E.; | journal = Environmental progress | year = 1994 | volume = 13 | issue = 2 | pages = 134–137 | doi = 10.1002/ep.670130217}}</ref><ref>.{{cite journal | title = Abatement of N<sub>2</sub>O emissions produced in the adipic acid industry | author = A. Shimizu, , K. Tanaka and M. Fujimori | journal = Chemosphere - Global Change Science | year = 2000 | volume = 2 | issue = 3-4 | pages = 425–434 | doi = 10.1016/S1465-9972(00)00024-6}}</ref> This might become a major commercial source, but will require the removal of higher oxides of nitrogen and organic impurities. Currently much of the gas is decomposed before release for environmental protection. Greener processes may prevail that substitute [[hydrogen peroxide]] for nitric acid oxidation; hence no generation of oxide of nitrogen by-products. [[Hydroxylammonium chloride]] can react with [[sodium nitrite]] to produce N<sub>2</sub>O as well: : NH<sub>3</sub>OH<sup>+</sup>Cl<sup>−</sup> + NaNO<sub>2</sub> → N<sub>2</sub>O + NaCl + H<sub>2</sub>O If the nitrite is added to the hydroxylamine solution, the only remaining byproduct is salt water. However, if the hydroxylamine solution is added to the nitrite solution (nitrite is in excess), then toxic higher oxides of nitrogen are also formed. == Uses == === Inhalant effects === Nitrous oxide (N<sub>2</sub>O) is a [[dissociative]] drug that can cause [[Analgesic|analgesia]], [[depersonalization]], [[derealization]], [[dizziness]], [[Euphoria (emotion)|euphoria]],and some sound distortion . <ref> AJ Giannini. Volatiles. In NS Miller (Ed.). A Comprehensive Handbook of Drug and Alcohol Addiction. NY, Marcel Dekker, 1991.</ref> ====In medicine==== Previously, nitrous oxide was typically administered by dentists through a demand-valve inhaler over the nose that only releases gas when the patient inhales through the nose; full-face masks are not commonly used by dentists, so that the patient's mouth can be worked on while the patient continues to inhale the gas. Current use involves constant supply flowmeters which allow the proportion of nitrous oxide and the combined gas flow rate to be individually adjusted. The masks still cover only the nose. Because nitrous oxide is minimally metabolized, it retains its potency when exhaled into the room by the patient and can pose an intoxicating and prolonged-exposure hazard to the clinic staff if the room is poorly ventilated. Where nitrous oxide is administered, a continuous-flow fresh-air ventilation system or nitrous-scavenging system is used to prevent waste gas buildup. Nitrous oxide is a weak general anesthetic, and so is generally not used alone in general anesthesia. In general anesthesia it is used as a carrier gas in a 2:1 ratio with oxygen for more powerful general anesthetic agents such as [[sevoflurane]] or [[desflurane]]. It has a MAC ([[minimum alveolar concentration]]) of 105% and a blood:gas partition coefficient of 0.46. Less than 0.004% is metabolised in humans. ====Recreational use==== {{Refimprove|date=July 2007}} Since the earliest uses of nitrous oxide for medical or dental purposes, it has also been used recreationally as an [[inhalant]], because it causes euphoria and slight hallucinations. Only a small number of recreational users (such as dental office workers or medical gas technicians) have legal access to pure nitrous oxide [[canister]]s that are intended for medical or dental use. Most recreational users obtain nitrous oxide from compressed gas containers which use nitrous oxide as a propellant for whipped cream or from automotive nitrous systems. Automotive nitrous available to the public sometimes has ~100 ppm [[sulfur dioxide]] and/or [[sulfur|elemental sulfur]] added to prevent recreational use/abuse{{Fact|date=February 2008}}; (not [[hydrogen sulfide]] as suggested by<ref>{{cite web | url = http://www.justsayn2o.com/nitrous.obtain.html | author = | publisher = Just Say N<sub>2</sub>O | date = | accessdate = 2008-02-02 | title = Obtaining Nitrous Oxide}}</ref>). Inhalation of such a mixture is nearly impossible after one breath due to gagging and sooner or later, involuntary clamping off of the trachea; (some with "sulfite" allergies could even die due to allergic reaction). Users typically inflate a balloon or a plastic bag with nitrous oxide and inhale the gas for its effects, or they use a whipped cream canister which upon charge releases the gas into the canister before use. Nitrous oxide expelled directly from a tank or canister would severely damage the user's lungs due to its extremely cold exiting temperature due to the sudden expansion. By allowing the gas to expand in a balloon, bag or a whipped cream canister, the final output temperature of the gas is raised immensely. While nitrous oxide is not a dangerous substance per se, recreational users typically do not mix it with air or oxygen (a 70/30 mix of nitrous oxide and oxygen, respectively (which is the same amount of oxygen in normal air) is standard procedure in a dentist's office) and thus may risk injury, or in worst case: death, from lack of oxygen ([[hypoxia (medical)|anoxia]]). Nitrous oxide, when inhaled using a home made system consisting of a mask and/or regulator, presents the highest potential danger due to the automatic, continuous application. This may in turn prevent adequate oxygen from reaching the user, rendering him unconscious, subsequently leading to death due to asphyxiation. Inhaling nitrous oxide in conjunction with an [[alkyl nitrite]] (aka [[poppers]]) is in some circles referred to as "space surfing", as the nitrous oxide acts [[Synergy|synergistically]] with the alkyl nitrite to create strong (but short-lived) euphoria, analgesia, dissociation, and in some cases, sensations of internal movement or agitation. The name also comes from the sound distorting effects of nitrous oxide, which some users compare to the sound of waves crashing on a beach (hence "surfing"). While powerful, this is a potentially dangerous combination, as the central nervous system (CNS) depressing effects of the nitrous oxide, combined with the drop in blood pressure (which is characteristic of nitrite inhalant use), may cause [[hypotension]], unconsciousness, or, in the case of extreme overdose, death. Individuals with cardiac conditions, complications arising from stroke or surgery, or chronically low blood pressure are advised not to use these two drugs simultaneously. Nitrous oxide is used as a whipping agent due to the ease with which it migrates into and out of oils; only a few seconds of rapid shaking is enough to migrate the gas into the oily cream under pressure. Due to this ability, nitrous also easily moves throughout the body, into and out of cells, because cell membranes are oil-based lipids. Prolonged inhalation of high concentrations of nitrous oxide will cause it to migrate throughout the body into sinus cavities, the digestive tract, and into fat cells. An inactive person who has breathed high concentrations for 20-30 minutes but then breathes normally will still retain the gas in his body at low doses as the gas slowly migrates back out of these internal cavities. Even after several hours of not breathing the gas, sudden rapid whole-body movements such as calisthenics causes the dissolved gas to suddenly begin migrating out of fat cells, resulting in a latent dosing effect. Nitrous oxide can be habit-forming because of its short-lived effect (generally from 0.1 - 1 minutes in recreational doses) and ease of access. Death can result if it is inhaled in such a way that too little oxygen is breathed in. While the pure gas is generally not toxic, long-term use in excessive quantities has been associated with [[vitamin B12]] deficiency [[anemia]] due to reduced [[hemopoiesis]], [[neuropathy]], [[tinnitus]], and [[numbness]] in extremities. Harmful irreversible effects that may be caused by abuse of nitrous oxide include peripheral neuropathies and limb spasms.<ref>{{cite web | publisher = National Institute on Drug Abuse | date = 2006 | title = NIDA InfoFacts: Inhalants | url = http://www.drugabuse.gov/Infofacts/Inhalants.html | accessdate = 2008-03-02}} </ref> Pregnant women should not use nitrous oxide as chronic use is [[teratogen]]ic and [[fetus|foetotoxic]]. One study in rats found that long term exposure to high doses of nitrous oxide may lead to [[Olney's lesions]].<ref name="Jevtovic-Todorovic"/> [[Image:Nitrous oxide - 10 x 8g.jpg|thumb|200px|An 8g canister of nitrous oxide intended for use as a whipped cream aerating agent]] === Aerosol propellant === The gas is approved for use as a [[food additive]] (also known as E942), specifically as an [[aerosol spray#Propellant|aerosol spray propellant]]. Its most common uses in this context are in aerosol [[whipped cream]] canisters, [[cooking spray]]s, and as an inert gas used to displace bacteria-inducing oxygen when filling packages of [[potato chips]] and other similar snack foods. The gas is extremely soluble in fatty compounds. In aerosol whipped cream, it is dissolved in the fatty cream until it leaves the can, when it becomes gaseous and thus creates foam. Used in this way, it produces whipped cream four times the volume of the liquid, whereas whipping air into cream only produces twice the volume. If air were used as a propellant, under increased pressure the oxygen would accelerate [[rancidification]] of the butterfat, while nitrous oxide inhibits such degradation. Carbon dioxide cannot be used as a propellant for whipped cream because carbon dioxide creates an acid environment in water, which would curdle the cream. However, the whipped cream produced with nitrous oxide is unstable, and will return to a more or less liquid state within half an hour to one hour. Thus, the method is not suitable for decorating food that will not be immediately served. Similarly, [[cooking spray]], which is made from various types of oils combined with [[lecithin]] (an [[emulsifier]]), may use nitrous oxide as a [[propellant]]; other propellants used in cooking spray include food-grade [[alcohol]] and [[propane]]. Users of nitrous oxide often obtain it from whipped cream dispensers that use nitrous oxide as a propellant (see above section), for recreational use as a euphoria-inducing [[inhalant]] drug. It is non-harmful in small doses, but risks due to lack of oxygen do exist (see section on "Recreational use" above). === Rocket motors === Nitrous oxide can be used as an [[oxidizing agent|oxidizer]] in a [[rocket]] motor. This has the advantages over other oxidizers that it is non-toxic and, due to its stability at room temperature, easy to store and relatively safe to carry on a flight. As a secondary benefit it can be readily decomposed to form breathing air. Its high density and low storage pressure enable it to be highly competitive with stored high-pressure gas systems. In a 1914 patent, American rocket pioneer [[Robert Goddard]] suggested nitrous oxide and gasoline as possible propellants for a liquid-fueled rocket. Nitrous oxide has been the oxidizer of choice in several [[hybrid rocket]] designs (using solid fuel with a liquid or gaseous oxidizer). The combination of nitrous oxide with [[hydroxyl-terminated polybutadiene]] fuel has been used by [[SpaceShipOne]] and others. It is also notably used in [[amateur rocketry|amateur]] and [[high power rocket]]ry with various [[plastic]]s as the fuel. An episode of ''[[MythBusters]]'' featured a hybrid rocket built using a [[paraffin]]/powdered carbon mixture as its solid fuel and nitrous oxide as its oxidizer. Nitrous oxide can also be used in a [[monopropellant rocket]]. In the presence of a heated [[catalyst]], N<sub>2</sub>O will decompose exothermically into nitrogen and oxygen, at a temperature of approximately 1300 °C. Because of the large heat release the catalytic action rapidly becomes secondary as thermal autodecomposition becomes dominant. In a vacuum thruster, this can provide a monopropellant [[specific impulse]] (''I''<sub>sp</sub>) of as much as 180s. While noticeably less than the ''I''<sub>sp</sub> available from [[hydrazine]] thrusters (monopropellant or [[Bipropellant rocket|bipropellant]] with [[Dinitrogen tetroxide|nitrogen tetroxide]]), the decreased toxicity makes nitrous oxide an option worth investigating. Because of its release of very high temperature oxygen as a monopropellant the addition of even small amounts of a fuel such as hydrogen rapidly increases the specific impulse and the high oxygen temperatures simplify ignition of the fuel. ''I''<sub>sp</sub> greater than 340 seconds can be readily achieved. Its low freezing point also eases thermal management as compared to hydrazine -- a valuable property on a spacecraft which may contain quantities of cryogenic propellant. === Internal combustion engine === {{main|Nitrous}} In vehicle [[racing]], nitrous oxide (often referred to as just "[[nitrous]]"or "nitro" in this context to differ from the acronym NOS which is the brand Nitrous Oxide Systems) is sometimes injected into the intake manifold (or prior to the intake manifold), some systems directly inject right before the cylinder (direct port injection) to increase power. The gas itself is not flammable, but it delivers more [[oxygen]] than atmospheric air by breaking down at elevated temperatures, allowing the engine to burn more fuel and air and resulting in more powerful combustion. Nitrous oxide is stored as a compressed liquid; the [[heat of vaporization|evaporation]] and expansion of liquid nitrous oxide in the [[intake manifold]] causes a large drop in intake charge temperature, resulting in a denser charge, further allowing more air/fuel mixture to enter the cylinder. The lower temperature can also reduce [[Engine knocking|detonation]]. The same technique was used during [[World War II]] by [[Luftwaffe]] aircraft with the [[GM 1]] system to boost the power output of [[aircraft engine]]s. Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to extremely high altitudes. Accordingly, it was only used by specialized planes like high-altitude [[reconnaissance aircraft]], [[schnellbomber|high-speed bombers]] and high-altitude [[interceptor aircraft|interceptors]]. One of the major problems of using nitrous oxide in a reciprocating engine is that it can produce enough power to damage or destroy the engine. Very large power increases are possible, and if the mechanical structure of the engine is not properly reinforced, the engine may be severely damaged or destroyed during this kind of operation. It is very important with nitrous oxide augmentation of [[internal combustion engine]]s to maintain proper operating temperatures and fuel levels to prevent ''preignition'', or ''detonation'' (sometimes referred to as ''knocking'' or ''pinging''). == Neuropharmacology == [[Image:N2O Medical Tanks.jpg|thumb|100px|right|Medical grade nitrous oxide tanks used in dentistry]] Nitrous oxide shares many pharmacological similarities with other inhaled anesthetics, but there are a number of differences. Nitrous oxide is relatively [[non-polar]], has a low [[molecular weight]], and high lipid solubility. As a result it can quickly diffuse into [[phospholipid]] [[cell membranes]]. Like many classical anesthetics, the exact mechanism of action is still open to some conjecture. It [[NMDA receptor antagonist|antagonizes the NMDA receptor]] at partial pressures similar to those used in general anaesthesia. The evidence on the effect of N<sub>2</sub>O on [[GABA]]-A currently is mixed, but tends to show a lower potency potentiation.<ref name="mennerick">{{cite journal | title = Effect of nitrous oxide on excitatory and inhibitory synaptic transmission in hippocampal cultures | author = Mennerick, S., Jevtovic-Todorovic, V., Todorovic, S.M., Shen, W., Olney, J.W. & Zorumski, C.F. | journal = [[Journal of Neuroscience]] | volume = 18 | issue = 23 | pages = 9716–26 | year = 1998 | url = http://www.jneurosci.org/cgi/content/abstract/18/23/9716 | doi = | pmid = 9822732 }}</ref> N<sub>2</sub>O, like other [[volatile anesthetic]]s, activates twin-pore [[potassium channel]]s, albeit weakly. These channels are largely responsible for keeping neurons at the resting (unexcited) potential.<ref name="gruss">{{cite journal | title = Two-pore-domain K<sup>+</sup> channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane | author = Gruss, M., Bushell, T.J., Bright, D.P., Lieb, W.R., Mathie, A. & Franks, N.P. | journal = Molecular Pharmacology | volume = 65 | issue = | pages = 443–52 | year = 2004 | doi = }} </ref> Unlike many anesthetics, however, N<sub>2</sub>O does not seem to affect [[calcium channel]]s.<ref name="mennerick"/> Unlike most general anesthetics, N<sub>2</sub>O appears to affect the GABA receptor. In many behavioral tests of [[anxiety]], a low dose of N<sub>2</sub>O is a successful [[anxiolytic]]. This anti-anxiety effect is partially reversed by [[benzodiazepine]] [[receptor antagonist]]s. Mirroring this, animals which have developed tolerance to the anxiolytic effects of benzodiazepines are partially tolerant to nitrous oxide.<ref name="emmanouil">{{cite journal | title = Nitrous oxide anxiolytic effect in mice in the elevated plus maze: mediation by benzodiazepine receptors | author = Emmanouil, D.E., Johnson, C.H. & Quock, R.M. | journal = Psychopharmacology | volume = 115 | issue = 1-2 | pages = 167–72 | year = 1994 | url = | doi = 10.1007/BF02244768 }}</ref> Indeed, in humans given 30% N<sub>2</sub>O, benzodiazepine receptor antagonists reduced the subjective reports of feeling “high”, but did not alter psycho-motor performance.<ref name="zacny">{{cite journal | title = Flumazenil may attenuate some subjective effects of nitrous oxide in humans: a preliminary report | author = Zacny, J.P., Yajnik, S., Coalson, D., Lichtor, J.L., Apfelbaum, J.L., Rupani, G., Young, C., Thapar, P. & Klafta, J. | journal = Pharmacology Biochemistry and Behavior | volume = 51 | issue = 4 | pages = 815–9 | year = 1995 | url = | doi = 10.1016/0091-3057(95)00039-Y | pmid = 7675863 }}</ref> The effects of N<sub>2</sub>O seem linked to the interaction between the [[Opioid#Endogenous_opioids|endogenous opioid]] system and the descending [[noradrenergic]] system. When animals are given [[morphine]] chronically they develop tolerance to its analgesic (pain killing) effects; this also renders the animals tolerant to the analgesic effects of N<sub>2</sub>O.<ref>{{cite journal | title = Tolerance to nitrous oxide analgesia in rats and mice | author = Berkowitz, B.A., Finck, A.D., Hynes, M.D. & Ngai, S.H. | journal = Anesthesiology | volume = | issue = 51 | pages = 309–12 | year = 1979 | url = | doi = 10.1097/00000542-197910000-00006 <!--Retrieved from CrossRef by DOI bot--> }}</ref> Administration of [[antibodies]] which bind and block the activity of some endogenous opioids (not [[beta-endorphin]]), also block the antinociceptive effects of N<sub>2</sub>O.<ref name="branda">{{cite journal | title = Role of brain dynorphin in nitrous oxide antinociception in mice | author = Branda, E.M., Ramza, J.T., Cahill, F.J., Tseng, L.F. & Quock, R.M. | journal = Pharmacology Biochemistry and Behavior | volume = 65 | issue = | pages = 217–21 | year = 2000 | url = | doi = 10.1016/S0091-3057(99)00202-6 }}</ref> Drugs which inhibit the breakdown of endogenous opioids also potentiate the antinociceptive effects of N<sub>2</sub>O.<ref name="branda"/> Several experiments have shown that opioid receptor antagonists applied directly to the brain block the antinociceptive effects of N<sub>2</sub>O, but these drugs have no effect when injected into the [[spinal cord]]. Conversely, alpha-[[adrenoreceptor]] antagonists block the antinociceptive effects of N<sub>2</sub>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 | author = Guo, T.Z., Davies, M.F., Kingery, W.S., Patterson, A.J., Limbird, L.E. & Maze, M. | journal = Anesthesiology | volume = 90 | issue = | pages = 470–6 | year = 1999 | pmid = 9952154 | url = http://www.anesthesiology.org/pt/re/anes/abstract.00000542-199902000-00022.htm | doi = 10.1097/00000542-199902000-00022 <!--Retrieved from CrossRef by DOI bot--> }}</ref> Indeed, alpha2B-adrenoreceptor knockout mice or animals depleted in noradrenaline are nearly completely resistant to the antinociceptive effects of N<sub>2</sub>O.<ref>{{cite journal | title = Antinociceptive action of nitrous oxide is mediated by stimulation of noradrenergic neurons in the brainstem and activation of [alpha]<sub>2B</sub> adrenoceptors | author = Sawamura, S., Kingery, W.S., Davies, M.F., Agashe, G.S., Clark, J.D., Koblika, B.K., Hashimoto, T. & Maze, M. | journal = J. Neurosci. | volume = 20 | issue = 24 | pages = 9242–51 | year = 2000 | url = http://www.jneurosci.org/cgi/content/abstract/20/24/9242 | doi = | pmid = 11125002 }}</ref> It seems N<sub>2</sub>O-induced release of endogenous opioids causes disinhibition of [[brain stem]] noradrenergic neurons, which release [[norepinephrine]] into the spinal cord and inhibit pain signaling (Maze, M. and M. Fujinaga, 2000). Exactly how N<sub>2</sub>O causes the release of opioids is still uncertain. == Safety == The major safety hazards of nitrous oxide come from the fact that it is a compressed liquified gas, an asphyxiation risk, and a [[dissociative]] [[anaesthetic]]. Exposure to nitrous oxide causes short-term decreases in mental performance, audiovisual ability, and manual dexterity.<ref> Criteria for a recommended standard: occupational exposure to waste anesthetic gases and vapors. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 77B140. </ref> A study of workers<ref> Rowland AS, Baird DD, Weinberg CR, Shore DL, Shy CM, Wilcox AJ [1992]. Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide. New Eng J Med 327(14):993B997. </ref> and several experimental animal studies<ref>Corbett TH, Cornell RG, Endres JL, Millard RI [1973]. Effects of low concentrations of nitrous oxide on rat pregnancy. Anesthesiology 39:299B301.</ref><ref>Vieira E [1979]. Effect of the chronic administration of nitrous oxide 0.5% to gravid rats. Br J Anaesth 51:283B287. </ref><ref>Vieira E, Cleaton-Jones JP, Austin JC, Moyes DG, Shaw R [1980]. Effects of low concentrations of nitrous oxide on rat fetuses. Anesth and Analgesia 59(3):175B177. </ref><ref>Vieira E, Cleaton-Jones P, Moyes D [1983]. Effects of low intermittent concentrations of nitrous oxide on the developing rat fetus. Br J Anaesth 55:67B69. </ref> indicate that adverse reproductive effects may also result from chronic exposure to nitrous oxide. The [[National Institute for Occupational Safety and Health]] recommends that workers' exposure to nitrous oxide should be controlled during the administration of anesthetic gas in medical, dental, and veterinary operatories.<ref> NIOSH Alert: Controlling Exposures to Nitrous Oxide During Anesthetic Administration. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-100 [http://www.cdc.gov/niosh/noxidalr.html]</ref> ===Chemical/physical=== At room temperature (20°C) the saturated vapour pressure is 58.5 bar, rising up to 72.45 bar at 36.4°C -- the [[critical temperature]]. The pressure curve is thus unusually sensitive to temperature.<ref>[http://encyclopedia.airliquide.com/encyclopedia.asp?LanguageID=11&CountryID=19&Formula=&GasID=55&UNNumber= Air Liquid data on Nitrous oxide]</ref> Liquid nitrous oxide acts as a good solvent for many [[organic compounds]]; liquid mixtures and may form shock sensitive explosives.{{Fact|date=August 2007}} As with many strong oxidisers, contamination of parts with fuels have been implicated in rocketry accidents, where small quantities of nitrous / fuel mixtures explode due to 'water hammer' like effects (sometimes called 'dieseling' -- heating due to [[adiabatic]] compression of gases can reach decomposition temperatures).<ref>[http://www.ukrocketman.com/rocketry/hybridukhistory.shtml vaseline triggered explosion of hybrid rocket]</ref> Some common building materials such as stainless steel and aluminum can act as fuels with strong oxidisers such as nitrous oxide, as can contaminants, which can ignite due to adiabatic compression.<ref>[http://www.airproducts.com/nr/rdonlyres/8c46596e-2f7d-4895-b12a-e54cd63e1996/0/safetygram20.pdf Safetygram 20: Nitrous Oxide<!-- Bot generated title -->]</ref> There have also been accidents where nitrous oxide decomposition in plumbing has led to the explosion of large tanks.<ref>[http://www.hobbyspace.com/AAdmin/archive/SpecialTopics/Misc/eindhoven.pdf Nitrous Oxide Trailer Rupture July 2, 2001] Report at CGA Seminar “Safety and Reliability of Industrial Gases, Equipment and Facilities”, October 15 -17, 2001, St. Louis, Missouri by Konrad Munke, LindeGas AG</ref> ===Biological=== Nitrous oxide activates the cobalamin form of vitamin B{{ssub|12}} by oxidation. Symptoms of vitamin B{{ssub|12}} deficiency, including [[sensory neuropathy]], [[myelopathy]], and [[encephalopathy]], can occur within days or weeks of exposure to nitrous oxide [[anesthesia]] in people with subclinical vitamin B{{ssub|12}} deficiency.{{Fact|date=April 2008}} Symptoms are treated with high doses of vitamin B{{ssub|12}}, but recovery can be slow and incomplete<ref> AJ Giannini. Drug Abuse. Los Angeles, Health Information Press,1999. </ref> People with normal vitamin B{{ssub|12}} levels have sufficient vitamin B{{ssub|12}} stores to make the effects of nitrous oxide insignificant, unless exposure is repeated and prolonged (nitrous oxide abuse).{{Fact|date=April 2008}} Vitamin B{{ssub|12}} levels should be checked in people with risk factors for vitamin B{{ssub|12}} deficiency prior to using nitrous oxide anesthesia. Nitrous oxide has also been shown to induce early stages of [[Olney's lesions]] in the brains of rats. However none of the lesions found were irreversible.<ref name="Jevtovic-Todorovic">{{cite journal |author=Jevtovic-Todorovic V, Beals J, Benshoff N, Olney J |title=Prolonged exposure to inhalational anesthetic nitrous oxide kills neurons in adult rat brain |journal=Neuroscience |volume=122 |issue=3 |pages=609–16 |year=2003 |pmid=14622904 | doi = 10.1016/j.neuroscience.2003.07.012 <!--Retrieved from CrossRef by DOI bot-->}}</ref> ===Thermal=== Compressed nitrous oxide is usually stored at room temperature, but as the gas expands it quickly cools to sub-zero temperatures via the [[Joule-Thomson Effect]]. A leak or unexpected release of compressed nitrous oxide can result in an immediate and severe [[burn (injury)|burn]]. == Legality == {{Globalize}} In the [[United States]], possession of nitrous oxide is legal under federal law and is not subject to [[Drug Enforcement Administration|DEA]] purview.<ref name="ccle">[http://www.cognitiveliberty.org/dll/N20_state_laws.htm Center for Cognitive Liberty and Ethics: State Laws Concerning Inhalation of Nitrous Oxide]</ref> It is, however, regulated by the [[Food and Drug Administration]] under the Food Drug and Cosmetics Act; prosecution is possible under its "misbranding" clauses, prohibiting the sale or distribution of nitrous oxide for the purpose of [[recreational drug use|human consumption]]. Many states have laws regulating the possession, sale, and distribution of nitrous oxide; but these are normally limited to either banning distribution to minors, or to setting an upper limit for the amount of nitrous oxide that may be sold without special license, rather than banning possession or distribution completely. In most jurisdictions, such as at the federal level, sale or distribution for the purpose of recreational consumption is illegal.<ref name="ccle"/> In some countries, it is illegal to have nitrous oxide systems plumbed into an engine's intake manifold. These laws are ostensibly used to prevent [[street racing]] and meet emissions standards. Laughing gas is entirely legal to possess and inhale in the United Kingdom.<ref name="legality in the UK"> [http://www.timesonline.co.uk/tol/news/uk/article1329183.ece Clubbers’ laughing gas craze claims its first life - Times Online<!-- Bot generated title -->]</ref> However it is an offence under the Medicines Act to supply it for inhalation. <ref>http://www.thesun.co.uk/sol/homepage/news/article25849.ece</ref> In [[New Zealand]], the [[New Zealand Ministry of Health|Ministry of Health]] has warned that nitrous oxide is a prescription medicine, and its sale or possession without a prescription is an offence under the Medicines Act.<ref>[http://www.beehive.govt.nz/ViewDocument.aspx?DocumentID=23487 Beehive.govt.nz - Time's up for sham sales of laughing gas]</ref> This statement would seemingly prohibit all non-medicinal uses of the chemical, though it is implied that only recreational use will be legally targeted. == History== The gas was first synthesized by English chemist and natural philosopher [[Joseph Priestley]] in 1775 [http://www.justsayn2o.com/], who called it ''phlogisticated nitrous air'' (see [[phlogiston]]). Priestley describes the preparation of "nitrous air diminished" by heating iron filings dampened with [[nitric acid]] in ''Experiments and Observations on Different Kinds of Air'', (1775). Priestley was delighted with his discovery: "I have now discovered an air five or six times as good as common air... nothing I ever did has surprised me more, or is more satisfactory."<ref>J. R. Partington, ''A Short History of Chemistry'', 3rd ed., Dover Publications, Inc., New York, New York, 1989, pp. 110-121.</ref> [[Humphry Davy]] in the 1790s tested the gas on himself and some of his friends, including the poets [[Samuel Taylor Coleridge]] and [[Robert Southey]]. They realised that nitrous oxide considerably dulled the sensation of pain, even if the inhaler were still semi-conscious. After it was publicized extensively by [[Gardner Quincy Colton]] in the United States in the 1840s, it came into use as an anaesthetic, particularly by dentists, who do not typically have access to the services of an [[anesthesiologist]] and who may benefit from a patient who can respond to verbal commands. ==References== {{reflist|2}} ==External links== *[http://www.osha.gov/SLTC/healthguidelines/nitrousoxide/recognition.html Occupational Safety and Health Guideline for Nitrous Oxide] *[http://www.vega.org.uk/video/programme/111 Paul Crutzen Interview] Freeview video of Paul Crutzen Nobel Laureate for his work on decomposition of ozone talking to Harry Kroto Nobel Laureate by the Vega Science Trust. *[http://www.npi.gov.au/database/substance-info/profiles/67.html National Pollutant Inventory - Oxide of nitrogen fact sheet] *[http://www.tsinghua.edu.cn/docsn/lxx/mainpage/a/Web/index_files/page0002.htm Nitrous Oxide Specs] Extremely thorough Nitrous Oxide Facts *[http://www.cdc.gov/niosh/topics/nitrousoxide/ National Institute for Occupational Safety and Health - Nitrous Oxide] *[http://www.erowid.org/chemicals/nitrous/nitrous.shtml Erowid article on Nitrous Oxide] {{Dissociative psychedelics}} {{E number infobox 930-949}} {{General anesthetics}} [[Category:Oxides]] [[Category:Nitrogen compounds]] [[Category:Aerosol propellants]] [[Category:Anesthetics]] [[Category:Dissociatives]] [[Category:Greenhouse gases]] [[Category:Nitrogen metabolism]] [[Category:NMDA receptor antagonists]] [[Category:Monopropellants]] [[Category:Rocket oxidizers]] [[Category:Inhalants]] [[Category:Occupational safety and health]] [[Category:vehicle modification]] [[ar:أكسيد نيتروس]] [[ca:Òxid nitrós]] [[cs:Oxid dusný]] [[da:Lattergas]] [[de:Distickstoffmonoxid]] [[es:Óxido nitroso]] [[eo:Ridgaso]] [[fr:Protoxyde d'azote]] [[gl:Óxido nitroso]] [[it:Ossido di diazoto]] [[he:חמצן דו-חנקני]] [[lt:Diazoto monoksidas]] [[hu:Dinitrogén-oxid]] [[nl:Lachgas]] [[ja:亜酸化窒素]] [[no:Dinitrogenoksid]] [[nds:Distickstoffmonoxid]] [[pl:Podtlenek azotu]] [[pt:Óxido nitroso]] [[ru:Оксид азота(I)]] [[sr:Азотсубоксид]] [[fi:Ilokaasu]] [[sv:Lustgas]] [[ur:Nitrous oxide]] [[zh-yue:笑氣]] [[zh:一氧化二氮]]