Nitrous oxide
From Freepedia
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General |
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| Name | Dinitrogen oxide |
| Chemical formula | N2O |
| Appearance | Colorless gas |
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Physical |
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| Formula weight | 44.0 u |
| Melting point | 182 K (-91 °C) |
| Boiling point | 185 K (-88 °C) |
| Critical temperature | 309.6 K (36.4 °C) |
| Critical pressure | 7.245 MPa |
| Density | 1.2 g/cm3 (liquid) |
| Solubility | 0.112 g in 100g water |
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Thermochemistry |
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| ΔfH0gas | 82.05 kJ/mol |
| ΔfH0liquid | ? kJ/mol |
| ΔfH0solid | ? kJ/mol |
| S0gas, 100 kPa | 219.96 J/(mol·K) |
| S0liquid, 100 kPa | ? J/(mol·K) |
| S0solid | ? J/(mol·K) |
Safety |
| Inhalation | See main text. May cause asphyxiation without warning. |
| Skin | Hazardous when cryogenic or compressed. |
| Eyes | Hazardous when cryogenic or compressed. |
| More info | Hazardous Chemical Database |
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SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
Nitrous oxide, also known as dinitrogen oxide or dinitrogen monoxide, is a chemical compound with chemical formula N2O. Under room conditions it is a colourless non-flammable gas, with a pleasant, slightly sweet odor. It is commonly known as laughing gas due to the exhilarating effects of inhaling it, and because it can cause spontaneous laughter in some users; it's also known as NOS or nitrous because of its widespread usage in racing and motorsports. It is used in surgery and dentistry for its anaesthetic and analgesic effects. Nitrous oxide is present in the atmosphere where it acts as a powerful greenhouse gas.
Contents |
Chemistry
The structure of the nitrous oxide molecule is a linear chain of a nitrogen atom bound to a second nitrogen, which in turn is bound to an oxygen atom. It can be considered a resonance hybrid of
- <math> \mbox{N} \equiv \mbox{N}^+ - \mbox{O}^-</math> and <math>\mbox{N}^-= \mbox{N}^+= \mbox{O}\;</math>
Nitrous oxide N2O should not be confused with the other nitrogen oxides such as nitric oxide NO and nitrogen dioxide NO2.
Nitrous oxide can be used to produce nitrites by mixing it with boiling alkali metals, and to oxidize organic compounds at high temperatures.
The CAS number of nitrous oxide is 10024-97-2 and its UN number is 1070.
History
The gas was discovered by Joseph Priestley in 1772. 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 soon realised that nitrous oxide considerably dulled the sensation of pain, even if the inhaler were still semi-conscious, and so 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.
Uses
Inhalant effects — laughing gas
Nitrous oxide, N2O is a dissociative which can cause analgesia, euphoria, dizziness, flanging of sound, and in some cases, slight hallucinations and mild aphrodisiac effect. It can also result in mild nausea or lingering dizziness if too much is inhaled in too short a time.
During the 19th century, William James and many contemporaries found that inhalation of nitrous oxide resulted in a powerful spiritual/mystical experience for the user. James claimed to experience the fusing of dichotomies into a unity and a revelation of ultimate truth during the inhalation of nitrous oxide. Memory of this experience, however, quickly faded and any attempt to communicate it was difficult at best.
The drug currently enjoys moderate popularity in the American psychedelic community. It was often sold at Grateful Dead and Phish concerts, and due to some usage similarity to "crack" cocaine, it has come to be known colloquially as "hippie crack".
The recreational use of nitrous oxide is restricted in many districts. In California, for instance, inhalation of nitrous oxide "for the purpose of causing euphoria, or for the purpose of changing in any manner, one’s mental processes," is a criminal offense. (See, Cal. Pen. Code, Sec. 381b.) The Centre for Cognitive Liberty and Ethics, a nonprofit law and policy center in the United States, contends that such laws are unconstitutional "prior restraints on speech" and constitute "cognitive censorship."
Since nitrous oxide can cause dizziness, dissociation, and temporary loss of motor control, it is unsafe to inhale while standing up. Inhalation of nitrous oxide directly from a whipped cream charger or a tank poses serious health risks, as it can cause the lungs to collapse from high levels of pressure, forcing air into the chest cavity, and can cause frostbite since the gas is very cold when released. For those reasons, most recreational nitrous oxide users will discharge the gas into a balloon before inhaling.
While the pure gas itself is not toxic, death can result if it is inhaled in such a way that not enough oxygen is breathed in. Long-term use in large quantities has been associated with dangerous symptoms similar to vitamin B12 deficiency: anemia due to reduced hemopoiesis, neuropathy, tinnitus, and numbness in extremities. In chronic use it is also teratogenic, and foetotoxic. It can be habit-forming, mainly because of its short-lived effect (fewer than 60 seconds in recreational doses) and ease of access. Inhaling industrial-grade nitrous oxide is also dangerous, as it contains many impurities and is not intended for use on humans. Finally, nitrous oxide should not be confused with nitric oxide, a poisonous gas.
Medicine
Nitrous oxide is a weak general anesthetic, and is generally not used alone in anaesthesia. However, it has a very low short-term toxicity and is an excellent analgesic, so a 50/50 mixture of nitrous oxide and oxygen ("gas and air", supplied under the trade name Entonox) is commonly used during childbirth, for dental procedures, and in emergency medicine.
In general anesthesia it is often used in an 2:1 ratio with oxygen in addition to more powerful general anaesthetic agents such as sevoflurane or desflurane. Its lower solubility in blood means it has a very rapid onset and offset.
It has a MAC of 105% and a blood:gas partition coefficient of 0.46. Less that 0.004% is metabolised in humans.
It takes about 50 atmospheres in order to compress it into a liquid.
Aerosol propellant
The gas is licensed for use as a food additive, specifically as an aerosol spray propellant. Its most common uses in this context are in aerosol whipped cream canisters and as an inert gas used to displace staleness-inducing oxygen when filling packages of potato chips and other similar snack foods.
The gas is excellently 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.
Rocket motors
Nitrous oxide can be used as an oxidiser in a rocket engine. This has the advantages over other oxidisers that it is non-toxic and, due to its stability at room temperature, easy to store and relatively safe to carry on a flight.
Nitrous oxide has notably 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 hydroxy-terminated polybutadiene fuel has been used by SpaceShipOne and others. It is also notably used in amateur and high power rocketry with various plastics as the fuel. Recently an episode of MythBusters featured the building of a hybrid rocket using parafin wax as fuel, and nitrous oxide as the oxidiser.
Internal Combustion Engine
In car racing, nitrous oxide (often just "nitrous" in this context) is sometimes injected into the intake manifold (or just prior to the intake manifold) to increase power: even though the gas itself is not flammable, it delivers more oxygen than atmospheric air by breaking down at elevated temperatures, thus allowing the engine to burn more fuel and air. Additionally, since nitrous oxide is stored as a liquid, the evaporation of liquid nitrous oxide in the intake manifold causes a large drop in intake charge temperature. This results in a smaller, denser charge, and can reduce detonation, as well as increase power available to the engine.
The same technique was used during by World War II 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 specialized planes like high-altitude reconnaissance aircraft, high-speed bombers and high-altitude interceptors.
One of the major problems of using nitrous oxide in a reciprocating engine is that it can produce enough power to destroy the engine. Power increases of 100-300% are possible, and unless the mechanical structure of the engine is reinforced, most engines would not survive this kind of operation.
It is very important with nitrous oxide augmentation of internal combustion engines to maintain temperatures and fuel levels so as to prevent preignition, or detonation (sometimes referred to as knocking, pinging or pinking).
Safety
The major safety hazards of nitrous oxide come from the fact that it is a compressed liquified gas, and a dissociative anaesthetic.
While normally inert in storage and fairly safe to handle, nitrous oxide can decompose energetically and potentially detonate if initiated under the wrong circumstances. Liquid nitrous oxide acts a good solvent for many organic compounds; liquid mixtures can form somewhat sensitive explosives. Contamination with fuels has been implicated in a handful of rocketry accidents, where small quantities of nitrous / fuel mixtures detonated, triggering the explosive decomposition of residual nitrous oxide in plumbing.
Nitrous oxide in the atmosphere
Image:Major greenhouse gas trends.png Nitrogen oxides, nitrous oxide included, are greenhouse gases; nitrous oxide has 296 times the effect of carbon dioxide for producing global warming. Therefore, nitrogen oxides are a subject of efforts to curb greenhouse gas emissions, such as the Kyoto Protocol. Behind carbon dioxide and methane, nitrous oxide is the third most important gas contributing to global warming.
Nitrous oxide is naturally emitted from soils and oceans. Human activity contributes to the release of the gas through the cultivation of soil and the production and use of nitrogen fertilizers, the production of nylon, and the burning of fossil fuels and other organic matter.
Legality
Possession of nitrous oxide is illegal in most localities in the United States for the purposes of inhaling (or otherwise ingesting) if not under the care of a physician or dentist.
Nitrous oxide injection systems for automobiles is generally legal, although using your nitrous system will likely result in speeds that are in violation of other traffic laws. Some localities also require certified system components. There are many reported instances of police officers arresting drivers of vehicles equipped with nitrous oxide injection systems on the grounds that they [the driver] intend to inhale it. This is unlikely, as auto-grade nitrous oxide is mixed with hydrogen sulfide and would cause significant deleterious effects if inhaled — such arrests are made out of ignorance of the specifics of 'inhalable' nitrous oxide, or as a ploy to rid the public streets of potential illegal street racing via the misapplication of existing laws.
Neuropharmacology
Nitrous oxide (N2O) shares many pharmacological similarities with classical gaseous and intravenous anesthetics, however, as anyone who has experienced both knows, they have unquestionable differences.
Like many classical anesthetics, N2O non-competitively inhibits the NMDA receptor with high affinity and efficacy at concentrations directly proportional to its anaesthetic concentrations (Jevtovic-Todorovic et al., 1998; Mennerick et al., 1998; Yamakura & Harris, 2000). The evidence on the effect of N2O on GABA-A currents in mixed, but tends to show a lower potency potentiation (Dzoljic & Van Duijn, 1998; Mennerick et al., 1998; Yamakura & Harris, 2000). N2O like other volatile anesthetics activates twin-pore potassium channels, though weakly. These channels are largely responsible for keeping neurons at the resting (unexcited) potential (Gruss et al., 2004). Unlike many anesthetics however, N2O does not seem to effect calcium channels (Mennerick et al., 1998).
Unlike most general anesthetics, N2O seems to somehow effect the benzodiazepine receptor. In many behavioral tests of anxiety, low doses of N2O is a successful anxiolytic, however the anti-anxiety effect is partially reversed by benzodiazepine receptor antagonists, mirroring this, animals which have developed tolerance to the anxiolytic effects of benzodiazepines are partially tolerance to nitrous oxide (Czech & Green, 1992; Emmanouil et al., 1994; Quock et al., 1992). Indeed, in humans given 30% N2O, benzodiazepine receptor antagonists reduced the subjective reports of feeling “high”, but did not alter psycho-motor performance (Zacny et al., 1995).
Most interestingly, the effects of N2O seem somehow linked to the interaction between the endogenous opioid system and the descending noradrenergic system. When animals are given morphine chronically the develop tolerance to its antinociceptive (pain killing) effects, this also renders the animals tolerant to the antinocicpetive effects of N2O (Berkowitz et al., 1979). Administration of antibodies which bind and block the activity of some endogenous (not beta-endorphin) block the antinociceptive effects of N2O (Branda et al., 2000; Cahill et al., 2000). Drugs which inhibit the breakdown of endogenous opioids also potentiate the antinocicpetive effects of N2O (Branda et al., 2000). Several experiments have shows that opioid receptor antagonists applied directly to the brain block the antinocicpetive effects of N2O, but these drugs have no effect when injected into the spinal cord. Conversely alpha adrenoreceptor antagonists block the antinociceptive effects of N2O when given directly to the spinal cord, but not when applied directly to the brain (Fang et al., 1997; Guo et al., 1999; Guo et al., 1996). Indeed, alpha2B adrenoreceptor knockout mice or animals depleted in noradrenaline are nearly completely resistant to the antinociceptive effects of N2O (Sawamura et al., 2000; Zhang et al., 1999). It seems N2O-induced released of endogenous opioids causes disinhibition of brainstem noradrenergic neurons, which descend into the spinal cord and inhibit pain signaling. Exactly how N2O causes the release of opioids is still uncertain.
In conclusion N2O induces its effects through classical volatile anaethetic mechanisms like NMDA receptor antagonist, GABA-A potentation and potassium channel activation as well as novel mechanisms such as a benzodiazepine-like effect and stimulating endogenous opioid receptor.
Laughing Gas in fiction
- Laughing Gas (movie)
- Laughing Gas (novel)
- Laughing Gas is one of the main weapons used by the Batman villian, The Joker
External links
- Erowid Nitrous Oxide Vault
- The Use of Nitrous Oxide in Dentistry
- The automotive application of Nitrous Oxide
- "Subjective Effects of Nitrous Oxide" by William James
- Wiki on recreational nitrous oxide use in New Zealand
References
BERKOWITZ, B.A., FINCK, A.D., HYNES, M.D. & NGAI, S.H. (1979). Tolerance to nitrous oxide analgesia in rats and mice. Anesthesiology, 51, 309-12.
BRANDA, E.M., RAMZA, J.T., CAHILL, F.J., TSENG, L.F. & QUOCK, R.M. (2000). Role of brain dynorphin in nitrous oxide antinociception in mice. Pharmacol Biochem Behav, 65, 217-21.
CAHILL, F.J., ELLENBERGER, E.A., MUELLER, J.L., TSENG, L.F. & QUOCK, R.M. (2000). Antagonism of nitrous oxide antinociception in mice by intrathecally administered antisera to endogenous opioid peptides. J Biomed Sci, 7, 299-303.
CZECH, D.A. & GREEN, D.A. (1992). Anxiolytic effects of nitrous oxide in mice in the light-dark and holeboard exploratory tests. Psychopharmacology (Berl), 109, 315-20.
DZOLJIC, M. & VAN DUIJN, B. (1998). Nitrous oxide-induced enhancement of gamma-aminobutyric acidA-mediated chloride currents in acutely dissociated hippocampal neurons. Anesthesiology, 88, 473-80.
EMMANOUIL, D.E., JOHNSON, C.H. & QUOCK, R.M. (1994). Nitrous oxide anxiolytic effect in mice in the elevated plus maze: mediation by benzodiazepine receptors. Psychopharmacology (Berl), 115, 167-72.
FANG, F., GUO, T.Z., DAVIES, M.F. & MAZE, M. (1997). Opiate receptors in the periaqueductal gray mediate analgesic effect of nitrous oxide in rats. Eur J Pharmacol, 336, 137-41.
GRUSS, M., BUSHELL, T.J., BRIGHT, D.P., LIEB, W.R., MATHIE, A. & FRANKS, N.P. (2004). Two-pore-domain K+ channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane. Mol Pharmacol, 65, 443-52.
GUO, T.Z., DAVIES, M.F., KINGERY, W.S., PATTERSON, A.J., LIMBIRD, L.E. & MAZE, M. (1999). Nitrous oxide produces antinociceptive response via alpha2B and/or alpha2C adrenoceptor subtypes in mice. Anesthesiology, 90, 470-6.
GUO, T.Z., POREE, L., GOLDEN, W., STEIN, J., FUJINAGA, M. & MAZE, M. (1996). Antinociceptive response to nitrous oxide is mediated by supraspinal opiate and spinal alpha 2 adrenergic receptors in the rat. Anesthesiology, 85, 846-52.
JEVTOVIC-TODOROVIC, V., TODOROVIC, S.M., MENNERICK, S., POWELL, S., DIKRANIAN, K., BENSHOFF, N., ZORUMSKI, C.F. & OLNEY, J.W. (1998). Nitrous oxide (laughing gas) is an NMDA antagonist, neuroprotectant and neurotoxin. Nat Med, 4, 460-3.
MENNERICK, S., JEVTOVIC-TODOROVIC, V., TODOROVIC, S.M., SHEN, W., OLNEY, J.W. & ZORUMSKI, C.F. (1998). Effect of nitrous oxide on excitatory and inhibitory synaptic transmission in hippocampal cultures. J Neurosci, 18, 9716-26.
QUOCK, R.M., EMMANOUIL, D.E., VAUGHN, L.K. & PRUHS, R.J. (1992). Benzodiazepine receptor mediation of behavioral effects of nitrous oxide in mice. Psychopharmacology (Berl), 107, 310-4.
SAWAMURA, S., KINGERY, W.S., DAVIES, M.F., AGASHE, G.S., CLARK, J.D., KOBILKA, B.K., HASHIMOTO, T. & MAZE, M. (2000). Antinociceptive action of nitrous oxide is mediated by stimulation of noradrenergic neurons in the brainstem and activation of [alpha]2B adrenoceptors. J Neurosci, 20, 9242-51.
YAMAKURA, T. & HARRIS, R.A. (2000). Effects of gaseous anesthetics nitrous oxide and xenon on ligand-gated ion channels. Comparison with isoflurane and ethanol. Anesthesiology, 93, 1095-101.
ZACNY, J.P., YAJNIK, S., COALSON, D., LICHTOR, J.L., APFELBAUM, J.L., RUPANI, G., YOUNG, C., THAPAR, P. & KLAFTA, J. (1995). Flumazenil may attenuate some subjective effects of nitrous oxide in humans: a preliminary report. Pharmacol Biochem Behav, 51, 815-9.
ZHANG, C., DAVIES, M.F., GUO, T.Z. & MAZE, M. (1999). The analgesic action of nitrous oxide is dependent on the release of norepinephrine in the dorsal horn of the spinal cord. Anesthesiology, 91, 1401-7.
| Dissociative hallucinogens |
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{DXM} {Ketamine} {Nitrous oxide} {PCP} {Salvinorin A} |
Categories: Oxides | Nitrogen compounds | Anesthetics | Dissociatives | Greenhouse gases | Aerosol propellants | Schedule VI controlled substances | Nitrogen metabolism
