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Ozone: Properties, Toxicity, and Applications
Common methods for ozone generation are ultraviolet radiation, silent electric arc discharge and electrolysis. The unltraviolct radiation technique is used only when relatively low concentrations arc required, c. g. for environmental study. The electrolysis of water is not widely used because of its low cfficicncy. So far, the action of silent electric discharge on oxygen is the most common method for the production of ozone. It gives a yield of 6% by weight of ozone.
When high purity or quantity of ozone is desired, it is possible to use liquid ozone. The ozone-oxygen mixture from one of the above methods is passed through a vessel at liquid oxygen temperature (-183°C). Because of the large difference in the vapour pressure of ozone and oxygen, oxygen is pumped off from the mixture whereas ozone is liquefied. Liquid ozone is then vaporized from the conccntrated system for further use.
Ozone is a colourlcss gas with characteristic odour which is detectable by nose and provides a warning of toxic exposure. The ozone molcculc is non-linear with a bond angle of 116°. In contrast to oxygen, gaseous ozone is diamagnctic and possesses four resonance structures with (III) and (IV) accounting for its clectrophilic nature.
0* 0- 0 0 Л / / /
-о 0 0 0- 4) о- -о 0♦ I II III IV
Mechanistic studies of the biological effect of ozone are of particular interest. Vitamin E prolongs the life of rats exposed to ozone. This is based on the observation that the vitamin E-dcplctcd group undergoes a more significant change than the vitamin E-supplcmcntcd group in the fatty acid composition of total lung lipid. Therefore vitamin E, the biological antioxidant, provides protection from ozone toxicity.
Ozone is a particularly destructive substance to rubber and other elastomers.
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