Ozone highly poisonous gas (from Encarta Encyclopedia)

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Ozone

Ozone (Greek ozein, " to smell " ), allotropic form of oxygen having

three atoms in each molecule, formula O3. It is a pale blue, highly

poisonous gas with a strong odor. Ozone boils at -111.9° C

(-169.52°

F), melts at -192.5° C (-314.5° F), and has a specific gravity

of

2.144. Liquid ozone is a deep blue, strongly magnetic liquid. Ozone

is formed when an electric spark is passed through oxygen. The

presence of ozone causes a detectable odor near electrical machinery.

The commercial method of preparation consists of passing cold, dry

oxygen through a silent electrical discharge. Ozone is much more

active chemically than ordinary oxygen and is a better oxidizing

agent. It is used in purifying water, sterilizing air, and bleaching

certain foods. Ozone formed in the atmosphere from nitrogen oxides

and organic gases emitted by automobiles and industrial sources,

however, is a health hazard, and it may cause serious crop damage in

some areas. In 1998, the United States Environmental Protection

Agency (EPA) implemented a new air rule designed to curb nitrogen

oxides released by coal-fired electric power plants. Nitrogen oxides

combine with volatile organic compounds to form ozone, which is

believed to cause respiratory ailments such as bronchitis and asthma

(see Acid Rain; Environment).