Nitrous oxide (NYE-truss OX-side) is also known as
dinitrogen oxide, dinitrogen monoxide, nitrogen monoxide,
and laughing gas. It is a colorless, nonflammable gas with a
sweet odor. Its common name of laughing gas is derived from
the fact that it produces a sense of light-headedness when
inhaled. The gas is widely used as an anesthetic, a substance
that reduces sensitivity to pain and discomfort.
Nitrous oxide was probably first produced by the English
chemist and physicist Robert Boyle (1627–1691), although he
did not recognize the new compound he had found. Credit for
the discovery of nitrous oxide is, therefore, usually given to
the English chemist Joseph Priestley (1733–1804), who produced
the gas in 1772 and named it ‘‘nitrous air.’’ Other early
names used for the gas include ‘‘gaseous of azote’’ (nitrogen)
and ‘‘oxide of speton.’’ The most complete experiments on the
gas were conducted by the English chemist and physicist Sir
Humphry Davy (1778–1829), who tested nitrous oxide on
himself and his friends. He found that the gas could lessen
pain and discomfort and provided a sense of relaxation and
well-being. Before long, doctors were making use of Davy’s
discovery by using nitrous oxide as an anesthetic.
The public found other uses for the gas as well. During
the Victorian period in England, members of the upper class
often held laughing gas parties at which people gathered to
inhale nitrous oxide as a recreational drug, rather than for
any therapeutic purpose. In the United States, the showman
P. T. Barnum (1810–1891) created a sideshow exhibit in which
people were invited to test the effects of inhaling nitrous
oxide. After seeing a demonstration of this kind, the American
dentist Horace Wells (1815–1848) first used nitrous oxide
as an anesthetic on his patients.
In 1868, the American surgeon Edmund Andrews (1824–
1904) extended the use of nitrous oxide as an anesthetic for
his surgical patients. He mixed the gas with oxygen to
ensure that patients received enough oxygen while receiving
the anesthetic. The gas is still widely used by dentists as a
safe and relatively pleasant way of helping patients endure
the discomfort of drilling and other dental procedures.
The most common commercial method of producing
nitrous oxide involves the controlled heating of ammonium
nitrate (NH4NO3). The compound decomposes to form nitrous
oxide and water. The reaction is essentially the same one
originally used by Priestley in 1772. Although an efficient
means of producing the gas, the reaction must be carried out
with extreme care as ammonium nitrate has a tendency to
decompose explosively when heated. Nitrous oxide can also
be produced by the decomposition of nitrates (compounds
containing the NO3 radical), nitrites (compounds containing
the NO2) radical, or nitriles (compounds containing the CH
radical).
Nitrous oxide is best known and most widely used as an
anesthetic. Its use is limited primarily to dental procedures
and minor surgeries. Dentists favor nitrous oxide as an anesthetic
because the gas does not make patients completely
unconscious and does not require an anesthesiologist to
administer it. Nitrous oxide works as an anesthetic by blocking
neurotransmitter receptors in the brain, preventing pain
messages from being transmitted.
Nitrous oxide is also used as a fuel additive in racing
cars, in which case it is often referred to as nitro. The gas is
injected into the intake manifold where it mixes with air and
fuel vapors. Since it breaks down at the high temperatures in
the car’s engine, it provides additional oxygen to increase the
efficiency with which the fuel burns. During World War II,
pilots used nitrous oxide for a similar purpose in their airplanes.
Some additional uses of nitrous oxide include:
• As a propellant in food aerosols;
• For the detection of leaks;
• As a packaging gas for potato chips and other snack
foods, preventing moisture from making the product
become stale;
• In the preparation of other nitrogen compounds; and
• As an oxidizing agent for various industrial processes.
Nitrous oxide is safe to use in moderate amounts under
controlled conditions. Some people use the compound as a
recreational drug, however, hoping to get a ‘‘high’’ from inhaling
it. One risk of this practice is that the inhalation of
nitrous oxide may reduce the amount of oxygen a person
receives. Also, some long-term health effects, such as anemia
(low red blood cell count) and neuropathy (damage to the
nerves), have been associated with excessive use of the compound.
The use of nitrous oxide for recreational purposes is a
crime in some states.
