An allotropic, triatomic form of oxygen, O₃; a faintly blue, irritating gas with a characteristic pungent odor, but at -112 degrees C it condenses to a blue magnetic liquid. It occurs in minute quantities in the air near the Earth's surface and in larger quantities in the stratosphere as a product of the action of ultraviolet light of short wavelengths on ordinary oxygen. Ozone is generated usually in dilute form by a silent electric discharge in oxygen or air. It decomposes to oxygen (as when heated) and it is a stronger oxidizing agent than oxygen. Used chiefly in disinfection and in deodorization (such as in water purification and in air conditioning), in oxidation and bleaching (such as in the treatment 2230 of industrial wastes), and in ozonolysis (such as in the manufacture of azelaic acid from oleic acid).