Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others,[4] is a chemical compound, an oxide of nitrogen with the formulaN 2O. At room temperature, it is a colourless non-flammablegas, and has a slightly sweet scent and taste.[4] At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.[4]
"Living Made Easy": A satirical print from 1830 depicting Humphry Davy administering a dose of laughing gas to a woman
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".[20]
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 trials,[clarification needed] 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.[20] 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.[21] Davy coined the name "laughing gas" for nitrous oxide.[22]
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 anaesthesia. The use of nitrous oxide as a recreational drug at "laughing gas parties", primarily arranged for the 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.[23]
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.[24]
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.[25] 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.[26] 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.[27] 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 and New York City.[20] Over the following three years, Colton and his associates successfully administered nitrous oxide to more than 25,000 patients.[28] Today, nitrous oxide is used in dentistry as an anxiolytic, as an adjunct to 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.[20] 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.[28] 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.
Colton's popularisation of nitrous oxide led to its adoption by a number of less than reputable quacksalvers, who touted it as a cure for consumption, 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.[29][30]
Chemical properties and reactions
Nitrous oxide is a colourless gas with a faint, sweet odour.
Nitrous oxide supports combustion by releasing the dipolar bonded oxygen radical, and can thus relight a glowing splint.
N 2O is inert at room temperature and has few reactions. At elevated temperatures, its reactivity increases. For example, nitrous oxide reacts with NaNH 2 at 187°C (369°F) to give NaN 3:
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.[31]
The effects of inhaling sub-anaesthetic doses of nitrous oxide may vary unpredictably with settings and individual differences;[36][37] however, Jay (2008)[38] 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.[38]
Anxiolytic effect
In behavioural tests of anxiety, a low dose of N 2O is an effective anxiolytic. This anti-anxiety effect is associated with enhanced activity of GABAA receptors, as it is partially reversed by benzodiazepine receptorantagonists. Mirroring this, animals that have developed tolerance to the anxiolytic effects of benzodiazepines are partially tolerant to N 2O.[39] Indeed, in humans given 30% N 2O, benzodiazepine receptor antagonists reduced the subjective reports of feeling "high", but did not alter psychomotor performance.[40][41]
Analgesic effect
The analgesic effects of N 2O are linked to the interaction between the endogenous opioid system and the descending 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 N 2O.[42] Administration of antibodies that bind and block the activity of some endogenous opioids (not β-endorphin) also block the antinociceptive effects of N 2O.[43] Drugs that inhibit the breakdown of endogenous opioids also potentiate the antinociceptive effects of N 2O.[43] Several experiments have shown that opioid receptor antagonists applied directly to the brain block the antinociceptive effects of N 2O, but these drugs have no effect when injected into the spinal cord.
Apart from an indirect action, nitrous oxide, like morphine [44] also interacts directly with the endogenous opioid system by binding at opioid receptor binding sites.[45][46]
Conversely, α2-adrenoceptor antagonists block the pain-reducing effects of N 2O when given directly to the spinal cord, but not when applied directly to the brain.[47] Indeed, α2B-adrenoceptor knockout mice or animals depleted in norepinephrine are nearly completely resistant to the antinociceptive effects of N 2O.[48] Apparently N 2O-induced release of endogenous opioids causes disinhibition of brainstem noradrenergic neurons, which release norepinephrine into the spinal cord and inhibit pain signalling.[49] Exactly how N 2O causes the release of endogenous opioid peptides remains uncertain.
Production
Various methods of producing nitrous oxide are used.[50]
Industrial methods
Nitrous oxide production
Nitrous oxide is prepared on an industrial scale by carefully heating ammonium nitrate[50] at about 250°C, which decomposes into nitrous oxide and water vapour.[51]
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.[52]
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:[53]
2 NaNO3 + (NH4)2SO4 → Na2SO4 + 2 N2O + 4 H2O
Another method involves the reaction of urea, nitric acid and sulfuric acid:[54]
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:
NH3OHCl + NaNO2 → N2O + NaCl + 2 H2O
Treating HNO 3 with SnCl 2 and HCl also has been demonstrated:
Nitrous oxide (N2O) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-billion.Nitrous oxide atmospheric concentration since 1978Annual growth rate of atmospheric nitrous oxide since 2000Earth's nitrous oxide budget from the Global Carbon Project (2020)
Nitrous oxide is a 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 330ppb in 2017.[8] The growth rate of about 1ppb per year has also accelerated during recent decades.[9] Nitrous oxide's atmospheric abundance has grown more than 20% from a base level of about 270ppb in 1750.[58] Important atmospheric properties of N 2O are summarized in the following table:
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."[61]
Emissions by source
17.0 (12.2 to 23.5) million tonnes total annual average nitrogen in N 2O was emitted in 2007–2016.[61] About 40% of N 2O emissions are from humans and the rest are part of the natural nitrogen cycle.[62] The N 2O 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.[63]
Most of the N 2O emitted into the atmosphere, from natural and anthropogenic sources, is produced by microorganisms such as denitrifying bacteria and fungi in soils and oceans.[64] 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%).[65]Wetlands can also be emitters of nitrous oxide.[66][67] Emissions from thawing permafrost may be significant, but as of 2022 this is not certain.[61]
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%).[68][69][70][71][72] Agriculture enhances nitrous oxide production through soil cultivation, the use of nitrogen fertilisers and animal waste handling.[73] 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,[74] and the majority of a year's emissions may occur when conditions are favorable during "hot moments"[75][76] and/or at favorable locations known as "hotspots".[77]
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.[68][78][79]
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 (NH 3) to nitrite (NO− 2) and to nitrate (NO− 3)
anaerobic heterotrophic denitrification, the stepwise reduction of NO− 3 to NO− 2, nitric oxide (NO), N 2O and ultimately N 2, where facultative anaerobe bacteria use NO− 3 as an electron acceptor in the respiration of organic material in the condition of insufficient oxygen (O 2)
nitrifier denitrification, which is carried out by autotrophic NH 3-oxidising bacteria and the pathway whereby ammonia (NH 3) is oxidised to nitrite (NO− 2), followed by the reduction of NO− 2 to nitric oxide (NO), N 2O and molecular nitrogen (N 2)
heterotrophic nitrification
aerobic denitrification by the same heterotrophic nitrifiers
fungal denitrification
non-biological chemodenitrification
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.
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.[80]
Uses
Rocket motors
Nitrous oxide may be used as an oxidiser in a rocket motor. Compared to other oxidisers, it is much less toxic and more stable at room temperature, making it easier to store and safer to carry on a flight. Its high density and low storage pressure (when maintained at low temperatures) make it highly competitive with stored high-pressure gas systems.[81]
In a 1914 patent, American rocket pioneer Robert Goddard suggested nitrous oxide and gasoline as possible propellants for a liquid-fuelled rocket.[82] Nitrous oxide has been the oxidiser of choice in several hybrid rocket designs (using solid fuel with a liquid or gaseous oxidiser). The combination of nitrous oxide with hydroxyl-terminated polybutadiene fuel has been used by SpaceShipOne and others. It also is notably used in amateur and high power rocketry with various plastics as the fuel.
Nitrous oxide may also be used as a monopropellant. In the presence of a heated catalyst at a temperature of 577°C (1,071°F), N 2O decomposes exothermically into nitrogen and oxygen.[83] Because of the large heat release, the catalytic action rapidly becomes secondary, as thermal autodecomposition becomes dominant. In a vacuum thruster, this may provide a monopropellant specific impulse (Isp) up to 180 s. While noticeably less than the Isp available from hydrazine thrusters (monopropellant, or bipropellant with dinitrogen tetroxide), the decreased toxicity makes nitrous oxide a worthwhile option.
The ignition of nitrous oxide depends critically on pressure. It deflagrates at approximately 600°C (1,112°F) at a pressure of 309psi (21atmospheres).[84] At 600psi, the required ignition energy is only 6joules, whereas at 130psi a 2,500-joule ignition energy input is insufficient.[85][86]
In vehicle racing, nitrous oxide (often called "nitrous") increases engine power by providing more oxygen during combustion, thus allowing the engine to burn more fuel. It is an oxidising agent roughly equivalent to hydrogen peroxide, and much stronger than molecular oxygen. Nitrous oxide is not flammable at low pressure/temperature, but at about 300°C (572°F), its breakdown delivers more oxygen than atmospheric air. It often is mixed with another fuel that is easier to deflagrate.
Nitrous oxide is stored as a compressed liquid. In an engine intake manifold, the evaporation and expansion of the liquid causes a large drop in intake charge temperature, resulting in a denser charge and allowing more air/fuel mixture to enter the cylinder. Sometimes nitrous oxide is injected into (or prior to) the intake manifold, whereas other systems directly inject it just before the cylinder (direct port injection).
The technique was used during World War II by Luftwaffe aircraft with the GM-1 system to boost the power output of aircraft engines. 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 specialised planes such as high-altitude reconnaissance aircraft, high-speed bombers and high-altitude interceptor aircraft. It sometimes could be found on Luftwaffe aircraft also fitted with another engine-boost system, MW 50, a form of water injection for aviation engines that used methanol for its boost capabilities.
One of the major problems of nitrous oxide oxidant in a reciprocating engine is excessive power: if the mechanical structure of the engine is not properly reinforced, it may be severely damaged or destroyed. It is important with nitrous oxide augmentation of petrol engines to maintain proper and evenly spread operating temperatures and fuel levels to prevent pre-ignition (also called detonation or spark knock).[87] However, most problems associated with nitrous oxide come not from excessive power but from excessive pressure, since the gas builds up a much denser charge in the cylinder. The increased pressure and temperature can melt, crack, or warp the piston, valve, and cylinder head.
Automotive-grade liquid nitrous oxide differs slightly from medical-grade. A small amount of sulfur dioxide (SO 2) is added to prevent substance abuse.[88]
The gas is extremely soluble in fatty compounds. In pressurised aerosol whipped cream, it is dissolved in the fatty cream until it leaves the can, when it becomes gaseous and thus creates foam. This produces whipped cream four times the volume of the liquid, whereas whipping air into cream only produces twice the volume. Unlike air, nitrous oxide inhibits rancidification of the butterfat. Carbon dioxide cannot be used for whipped cream because it is acidic in water, which would curdle the cream and give it a seltzer-like "sparkle".
Extra-frothed whipped cream produced with nitrous oxide is unstable, and will return to liquid within half an hour to one hour.[89] Thus, it is not suitable for decorating food that will not be served immediately.
In December 2016, there was a shortage of aerosol whipped cream in the United States, with canned whipped cream use at its peak during the Christmas and holiday season, due to an explosion at the Air Liquide nitrous oxide facility in Florida in late August. The company prioritized the remaining supply of nitrous oxide to medical customers rather than to food manufacturing.[90]
Nitrous oxide has been used in dentistry and surgery, as an anaesthetic and analgesic, since 1844.[20] In the early days, the gas was administered through simple inhalers consisting of a breathing bag made of rubber cloth.[28] Today, the gas is administered in hospitals by means of an automated relative analgesia machine, with an anaesthetic vaporiser and a medical ventilator, that delivers a precisely dosed and breath-actuated flow of nitrous oxide mixed with oxygen in a 2:1 ratio.
Dentists use a simpler machine which only delivers an N 2O/O 2 mixture for the patient to inhale while conscious but must still be a recognised purpose designed dedicated relative analgesic flowmeter with a minimum 30% of oxygen at all times and a maximum upper limit of 70% nitrous oxide. The patient is kept conscious throughout the procedure, and retains adequate mental faculties to respond to questions and instructions from the dentist.[94]
Inhalation of nitrous oxide is used frequently to relieve pain associated with childbirth, trauma, oral surgery and acute coronary syndrome (including heart attacks). Its use during labour has been shown to be a safe and effective aid for birthing women.[95] Its use for acute coronary syndrome is of unknown benefit.[96]
In Canada and the UK, Entonox and Nitronox are used commonly by ambulance crews (including unregistered practitioners) as rapid and highly effective analgesic gas.
Fifty percent nitrous oxide can be considered for use by trained non-professional first aid responders in prehospital settings, given the relative ease and safety of administering 50% nitrous oxide as an analgesic. The rapid reversibility of its effect would also prevent it from precluding diagnosis.[97]
Aquatint depiction of a laughing gas party in the nineteenth century, by Thomas RowlandsonStreet sign indicating ban of nitrous oxide use near the Poelestraat in GroningenWhippit remnants (the small steel canisters) of recreational drug use, the Netherlands, 2017
From the 19th century, the widespread availability of the gas for medical and culinary purposes allowed for recreational use to greatly expand globally. In the UK as of 2014, nitrous oxide was estimated to be used by almost half a million young people at nightspots, festivals and parties.[99]
Widespread recreational use of the drug throughout the UK was featured in the 2017 Vice documentary Inside The Laughing Gas Black Market, in which journalist Matt Shea met with dealers of the drug who stole it from hospitals.[100]
A significant issue cited in London's press is the effect of nitrous oxide canister littering, which is highly visible and causes significant complaints from communities.[101]
Prior to 8 November 2023 in the UK, nitrous oxide was subject to the Psychoactive Substances Act 2016, making it illegal to produce, supply, import or export nitrous oxide for recreational use. The updated law prohibited possession of nitrous oxide, classifying it as a Class C drug under the Misuse of Drugs Act 1971.[102]
While nitrous oxide is understood by most recreational users to give a "safe high", many are unaware that excessive consumption may cause neurological harm which, if left untreated, can cause permanent neurological damage.[103] In Australia, recreation use became a public health concern following a rise in reports of neurotoxicity and emergency room admissions. In the state of South Australia, legislation was passed in 2020 to restrict canister sales.[104]
In 2024, under the street name, “Galaxy Gas”, nitrous oxide has exploded in popularity among young people for recreational use. Most of the popularity has been fostered through TikTok. [105]
Safety
Nitrous oxide is a significant occupational hazard for surgeons, dentists and nurses. Because the gas is minimally metabolised in humans (with a rate of 0.004%), it retains its potency when exhaled into the room by the patient, and can intoxicate the clinic staff if the room is poorly ventilated, with potential chronic exposure. A continuous-flow fresh-air ventilation system or N 2Oscavenger system may be needed to prevent waste-gas buildup.[citation needed] The National Institute for Occupational Safety and Health recommends that workers' exposure to nitrous oxide should be controlled during the administration of anaesthetic gas in medical, dental and veterinary operators.[106] It set a recommended exposure limit (REL) of 25 ppm (46mg/m3) to escaped anaesthetic.[107]
Exposure to nitrous oxide causes short-term impairment of cognition, audiovisual acuity, and manual dexterity, as well as spatial and temporal disorientation,[108] putting the user at risk of accidental injury.[38]
Nitrous oxide is neurotoxic, and medium or long-term habitual consumption of significant quantities can cause neurological harm with the potential for permanent damage if left untreated.[104][103] It is believed that, like other NMDA receptor antagonists, N 2O produces Olney's lesions in rodents upon prolonged (several hour) exposure.[109][110][111][112] However, because it is normally expelled from the body rapidly, it is less likely to be neurotoxic than other NMDAR antagonists.[113] In rodents, short-term exposure results in only mild injury that is rapidly reversible, and neuronal death occurs only after constant and sustained exposure.[109] Nitrous oxide may also cause neurotoxicity after extended exposure because of hypoxia. This is especially true of non-medical formulations such as whipped-cream chargers ("whippits" or "nangs"),[114] which contain no oxygen gas.[115]
In reports to poison control centers, heavy users (≥400 g or ≥200 L of N2O gas in one session) or frequent users (regular, i.e., daily or weekly) have developed signs of peripheral neuropathy: ataxia (gait abnormalities) or paresthesia (perception of sensations such as tingling, numbness, or prickling, mostly in the extremities). Such early signs of neurological damage indicate chronic toxicity.[116]
Nitrous oxide might have therapeutic use in treating stroke. In a rodent model, nitrous oxide at 75% by volume reduced ischemia-induced neuronal death induced by occlusion of the middle cerebral artery, and decreased NMDA-induced Ca2+ influx in neuronal cell cultures, a cause of excitotoxicity.[113]
Occupational exposure to ambient nitrous oxide has been associated with DNA damage, due to interruptions in DNA synthesis.[117] This correlation is dose-dependent[118][119] and does not appear to extend to casual recreational use; however, further research is needed to confirm the level of exposure needed to cause damage.
Inhalation of pure nitrous oxide causes oxygen deprivation, resulting in low blood pressure, fainting, and even heart attacks. This can occur if the user inhales large quantities continuously, as with a strap-on mask connected to a gas canister or other inhalation system, or prolonged breath-holding.[citation needed]
Long-term exposure to nitrous oxide may cause vitamin B12 deficiency. This can cause serious neurotoxicity if the user has preexisting vitamin B12 deficiency.[120] It inactivates the cobalamin form of vitamin B12 by oxidation. Symptoms of vitamin B12 deficiency, including sensory neuropathy, myelopathy and encephalopathy, may occur within days or weeks of exposure to nitrous oxide anaesthesia in people with subclinical vitamin B12 deficiency. Symptoms are treated with high doses of vitamin B12, but recovery can be slow and incomplete.[121] People with normal vitamin B12 levels have stores to make the effects of nitrous oxide insignificant, unless exposure is repeated and prolonged (nitrous oxide abuse). Vitamin B12 levels should be checked in people with risk factors for vitamin B12 deficiency prior to using nitrous oxide anaesthesia.[122]
Several experimental studies in rats indicate that chronic exposure of pregnant females to nitrous oxide may have adverse effects on the developing fetus.[123][124][125]
At room temperature (20°C [68°F]) the saturated vapour pressure is 50.525 bar, rising up to 72.45bar at 36.4°C (97.5°F)—the critical temperature. The pressure curve is thus unusually sensitive to temperature.[126] 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).[127] Some common building materials such as stainless steel and aluminium can act as fuels with strong oxidisers such as nitrous oxide, as can contaminants that may ignite due to adiabatic compression.[128] There also have been incidents where nitrous oxide decomposition in plumbing has led to the explosion of large tanks.[84]
Environmental impact
Global accounting of N 2O sources and sinks over the decade ending 2016 indicates that about 40% of the average 17TgN/yr (teragrams, or million metric tons, of nitrogen per year) of emissions originated from human activity, and shows that emissions growth chiefly came from expanding agriculture.[11][12]
Trends in the atmospheric abundance of long-lived greenhouse gases
Nitrous oxide has significant global warming potential as a greenhouse gas. On a per-molecule basis, considered over a 100-year period, nitrous oxide has 265 times the atmospheric heat-trapping ability of carbon dioxide (CO 2).[60] However, because of its low concentration (less than 1/1,000 of that of CO 2), its contribution to the greenhouse effect is less than one third that of carbon dioxide, and also less than methane.[129] On the other hand, since about 40% of the N 2O entering the atmosphere is the result of human activity,[68] control of nitrous oxide is part of efforts to curb greenhouse gas emissions.[130]
Most human caused nitrous oxide released into the atmosphere is a greenhouse gas emission from agriculture, when farmers add nitrogen-based fertilizers onto the fields, and through the breakdown of animal manure. Reduction of emissions can be a hot topic in the politics of climate change.[131]
Nitrous oxide is also released as a by-product of burning fossil fuel, though the amount released depends on which fuel was used. It is also emitted through the manufacture of nitric acid, which is used in the synthesis of nitrogen fertilizers. The production of adipic acid, a precursor to nylon and other synthetic clothing fibres, also releases nitrous oxide.[132]
A rise in atmospheric nitrous oxide concentrations has been implicated as a possible contributor to the extremely intense global warming during the Cenomanian-Turonian boundary event.[133]
Nitrous oxide has also been implicated in thinning the ozone layer. A 2009 study suggested that N 2O emission was the single most important ozone-depleting emission and it was expected to remain the largest throughout the 21st century.[10][134]
In India transfer of nitrous oxide from bulk cylinders to smaller, more transportable E-type, 1,590-litre-capacity tanks[135] is legal when intended for medical anaesthesia.
The Ministry of Health has warned that nitrous oxide is a prescription medicine whose sale or possession without a prescription is an offense under the Medicines Act.[136] This would seemingly prohibit all non-medicinal uses of nitrous oxide, although it is implied that only recreational use will be targeted.
In August 2015, the Council of the London Borough of Lambeth (UK) banned the use of the drug for recreational purposes, making offenders liable to an on-the-spot fine of up to £1,000.[137] In September 2023, the UK Government announced that nitrous oxide would be made illegal by the end of the year, with possession potentially carrying up to a two-year prison sentence or an unlimited fine.[138]
Possession of nitrous oxide is legal under United States federal law and is not subject to DEA purview.[139] 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 human consumption without a proper medical license. Many states have laws regulating the possession, sale and distribution of nitrous oxide. Such laws usually ban distribution to minors or limit the amount that may be sold without special license.[citation needed] For example, in California, possession for recreational use is prohibited and qualifies as a misdemeanor.[140]
General anaesthetics are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced coma that causes lack of awareness to painful stimuli, sufficient to facilitate surgical applications in clinical and veterinary practice. General anaesthetics do not act as analgesics and should also not be confused with sedatives. General anaesthetics are a structurally diverse group of compounds whose mechanisms encompass multiple biological targets involved in the control of neuronal pathways. The precise workings are the subject of some debate and ongoing research.
Inhalants are a broad range of household and industrial chemicals whose volatile vapors or pressurized gases can be concentrated and breathed in via the nose or mouth to produce intoxication, in a manner not intended by the manufacturer. They are inhaled at room temperature through volatilization or from a pressurized container, and do not include drugs that are sniffed after burning or heating.
Nitric oxide is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula. Nitric oxide is also a heteronuclear diatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding.
Nitrogen dioxide is a chemical compound with the formula NO2. One of several nitrogen oxides, nitrogen dioxide is a reddish-brown gas. It is a paramagnetic, bent molecule with C2v point group symmetry. Industrially, NO2 is an intermediate in the synthesis of nitric acid, millions of tons of which are produced each year, primarily for the production of fertilizers.
Isoflurane, sold under the brand name Forane among others, is a general anesthetic. It can be used to start or maintain anesthesia; however, other medications are often used to start anesthesia, due to airway irritation with isoflurane. Isoflurane is given via inhalation.
Sevoflurane, sold under the brand name Sevorane, among others, is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used as an inhalational anaesthetic for induction and maintenance of general anesthesia. After desflurane, it is the volatile anesthetic with the fastest onset. While its offset may be faster than agents other than desflurane in a few circumstances, its offset is more often similar to that of the much older agent isoflurane. While sevoflurane is only half as soluble as isoflurane in blood, the tissue blood partition coefficients of isoflurane and sevoflurane are quite similar. For example, in the muscle group: isoflurane 2.62 vs. sevoflurane 2.57. In the fat group: isoflurane 52 vs. sevoflurane 50. As a result, the longer the case, the more similar will be the emergence times for sevoflurane and isoflurane.
A whipped cream charger (colloquially called a whippet, nos or nang when used recreationally) is a steel cylinder or cartridge filled with nitrous oxide (N2O) that is used as a whipping agent in whipped cream. The narrow end of a charger has a foil covering that is broken to release the gas. This is usually done by a sharp pin inside the whipping siphon.
An anesthetic or anaesthetic is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.
Desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane, enflurane, and isoflurane, it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Together with sevoflurane, it is gradually replacing isoflurane for human use, except in economically undeveloped areas, where its high cost precludes its use. It has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood.
Nitrous oxide, as medical gas supply, is an inhaled gas used as pain medication, and is typically administered with 50% oxygen mix. It is often used together with other medications for anesthesia. Common uses include during childbirth, following trauma, and as part of end-of-life care. Onset of effect is typically within half a minute, and the effect lasts for about a minute.
An inhalational anesthetic is a chemical compound possessing general anesthetic properties that is delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anesthetic vaporiser and an anesthetic delivery system. Agents of significant contemporary clinical interest include volatile anesthetic agents such as isoflurane, sevoflurane and desflurane, as well as certain anesthetic gases such as nitrous oxide and xenon.
In atmospheric chemistry, NOx is shorthand for nitric oxide and nitrogen dioxide, the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone.
Denitrifying bacteria are a diverse group of bacteria that encompass many different phyla. This group of bacteria, together with denitrifying fungi and archaea, is capable of performing denitrification as part of the nitrogen cycle. Denitrification is performed by a variety of denitrifying bacteria that are widely distributed in soils and sediments and that use oxidized nitrogen compounds such as nitrate and nitrite in the absence of oxygen as a terminal electron acceptor. They metabolize nitrogenous compounds using various enzymes, including nitrate reductase (NAR), nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (NOS), turning nitrogen oxides back to nitrogen gas or nitrous oxide.
Dental anesthesia is the application of anesthesia to dentistry. It includes local anesthetics, sedation, and general anesthesia.
The Fink effect, also known as "diffusion anoxia", "diffusion hypoxia", or the "second gas effect", is a factor that influences the pO2 (partial pressure of oxygen) within the pulmonary alveoli. When water-soluble gases such as anesthetic agent N2O (nitrous oxide) are breathed in large quantities they can be dissolved in body fluids rapidly. This leads to a temporary increase in both the concentrations and partial pressures of oxygen and carbon dioxide in the alveoli.
Aerobic denitrification, or co-respiration, the simultaneous use of both oxygen (O2) and nitrate (NO−3) as oxidizing agents, performed by various genera of microorganisms. This process differs from anaerobic denitrification not only in its insensitivity to the presence of oxygen, but also in its higher potential to form nitrous oxide (N2O) as a byproduct.
Greenhouse gas emissions from wetlands of concern consist primarily of methane and nitrous oxide emissions. Wetlands are the largest natural source of atmospheric methane in the world, and are therefore a major area of concern with respect to climate change. Wetlands account for approximately 20–30% of atmospheric methane through emissions from soils and plants, and contribute an approximate average of 161 Tg of methane to the atmosphere per year.
Nitrous oxide (N2O), commonly referred to as laughing gas, along with various street names, is an inert gas which can induce euphoria, dissociation, hallucinogenic states of mind, and relaxation when inhaled. Nitrous oxide has no acute biochemical or cellular toxicity and is not metabolized in humans or other mammals. Rare deaths and injuries associated with use are due to asphyxia or accidents while under the influence, or vitamin B12 deficiency. Excessive use can lead to long-term and significant neurological and haematological toxicity.
Nitrogen-15 (15N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15N. Despite the different weights, 15N is involved in the same chemical reactions as the more abundant 14N and is therefore used to trace and quantify conversions of one nitrogen compound to another. 15N tracing is applied in biogeochemistry, soil science, environmental science, environmental microbiology and small molecule activation research.
Urine patches in cattle pastures generate large concentrations of the greenhouse gas nitrous oxide through nitrification and denitrification processes in urine-contaminated soils. Over the past few decades, the cattle population has increased more rapidly than the human population. Between the years 2000 and 2050, the cattle population is expected to increase from 1.5 billion to 2.6 billion. When large populations of cattle are packed into pastures, excessive amounts of urine soak into soils. This increases the rate at which nitrification and denitrification occur and produce nitrous oxide. Currently, nitrous oxide is one of the single most important ozone-depleting emissions and is expected to remain the largest throughout the 21st century.
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↑ Berger, Bruno (5 October 2007). "Is nitrous oxide safe?"(PDF). Swiss Propulsion Laboratory. pp.1–2. Archived(PDF) from the original on 9 October 2022. ...Self pressurizing (Vapor pressure at 20°C is ~50.1 bar...Nontoxic, low reactivity -> rel. safe handling (General safe???)...Additional energy from decomposition (as a monopropellant: ISP of 170 s)...Specific impulse doesn't change much with O/F...[page 2] N2O is a monopropellant (as H2O2 or Hydrazine...)
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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.
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