Nitrous Oxide (N2O)

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Nitrous Oxide (N2O)


Nitrous oxide—also called by various names such as hyponitrous acid anhydride, dinitrogen oxide, nitrogen monoxide, and factitious air—is the chemical compound represented as N2O; that is, composed of two atoms of nitrogen (N) and one atom of oxygen (O). Under normal temperatures and pressures, nitrous oxide is a non-flammable, colorless, and almost odorless gas that has a mildly sweet odor and taste. Besides nitrous oxide, the other oxides of nitrogen (gaseous mixtures of nitrogen and oxygen) are nitric oxide (NO), nitrogen dioxide (NO2), and nitrogen pentoxide (N2O5).

In nature, nitrous oxide is found in trace amounts within Earth's atmosphere due to the chemical reactions between nitrogen and oxygen. It is considered a greenhouse gas, with a regarded impact on global warming third to that of carbon dioxide (CO2) and methane (CH4). In addition, nitrous oxide is artificially produced by heating solid ammonium nitrate (NH4NO3).

Historical Background and Scientific Foundations

English chemist Joseph Priestley (1733–1804) discovered nitrous oxide in 1772. Later, English chemist Humphry Davy (1778–1829) described its physiological effect on humans, named it nitrous oxide, and nicknamed it laughing gas, after observing people's reactions to inhaling it during experiments.

Nitrous oxide was used within the medical and dental professions as a weak anesthetic (painkiller). Because it causes minor hallucinations and temporary dulling of the senses, it is sometimes used as a recreational drug. Although generally legal, nitrous oxide, when used to intoxicate, is a misdemeanor offense in most U.S. states.


AEROSOL: Particles of liquid or solid dispersed as a suspension in gas.

OZONE: An almost colorless, gaseous form of oxygen with an odor similar to weak chlorine. A relatively unstable compound of three atoms of oxygen, ozone constitutes, on average, less than one part per million (ppm) of the gases in the atmosphere. (Peak ozone concentration in the stratosphere can get as high as 10 ppm.) Yet ozone in the stratosphere absorbs nearly all of the biologically damaging solar ultraviolet radiation before it reaches Earth's surface, where it can cause skin cancer, cataracts, and immune deficiencies, and can harm crops and aquatic ecosystems.

PROPELLANT: Gas or liquid ejected by a rocket or other vehicle to make the vehicle move in the opposite direction.

STRATOSPHERE: The region of Earth's atmosphere ranging between about 9 and 30 mi (15 and 50 km) above Earth's surface.

ULTRAVIOLET RADIATION: The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5% of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition.

In the food industry, nitrous oxide is used as a propellant in food aerosol containers such as whipped cream and in snack food packages. In the dairy business, nitrous oxide prevents bacteria from growing inside dairy products. In the aerospace field, nitrous oxide, often called nitrous, is used as an oxidizer in rocket motors, while, in automobile racing, it is injected into fuel lines to increase the speed of vehicles.

Impacts and Issues

Nitrous oxide is primarily produced by humans with regard to agriculture, specifically by animal wastes, cultivation, and fertilizers. Secondarily, nitrous oxide is produced by industry, such as in the manufacture of nylon and nitric acid, and the burning of fossil fuels.

Nitrous oxide is produced naturally on land by bacteria in soils and in the water, especially in oceans. Having been found in the atmosphere for millions of years, nitrous oxide is a primary mechanism to control ozone in the stratosphere. Thus, its presence is a major reason why the amount of ozone, which helps to keep harmful ultraviolet radiation away from humans, has decreased over recent times.

Nitrous oxide is one of the major greenhouse gases. Even though its concentration in Earth's atmosphere is less than that of carbon dioxide—another major greenhouse gas—it has more mass per volume than carbon dioxide. Overall, only carbon dioxide and methane contribute more to global warming than does nitrous oxide. Consequently, nitrous oxide is included in efforts to reduce its negative effects on the global environment.

See Also Aerosols; Agriculture: Contribution to Climate Change; Atmospheric Pollution; Carbon Dioxide (CO2); Global Warming; Greenhouse Effect; Greenhouse Gases; Methane; Sink.



Keeling, R. F., ed. The Atmosphere. Boston, MA: Elsevier, 2006.

Li, Jie Jack. Laughing Gas, Viagra, and Lipitor: The Human Stories Behind the Drugs We Use. New York: Oxford University Press, 2006.

Paarmann, Carlene. Pain Control for Dental Practitioners: An Interactive Approach. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams and Wilkins, 2008.

Reay, David S., et al., eds. Greenhouse Gas Sinks. Cambridge, MA: CABI, 2007.

Seinfeld, John H. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. Hoboken, NJ: John Wiley, 2006.

Web Sites

“Nitrous Oxide.” Occupational Safety and Health Administration, U.S. Department of Labor. < recognition.html> (accessed November 21, 2007).

William Arthur Atkins