Ozone
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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). |
