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zinc oxide,chemical compound, ZnO, that is nearly insoluble in water but soluble in acids or alkalies. It occurs as white hexagonal crystals or a white powder commonly known as zinc white. Zinc white is used as a pigment in paints; less opaque than lithopone, it remains white when exposed to hydrogen sulfide or ultraviolet light. It is also used as a filler for rubber goods and in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. Because it absorbs ultraviolet light, zinc oxide can be used in ointments, creams, and lotions to protect against sunburn. Crystalline zinc oxide exhibits the piezoelectric effect, is luminescent, and is light sensitive. Zinc oxide occurs in nature as the mineral zincite. Zinc peroxide, ZnO2· 1-2H2O, is a white to yellow powder used in antiseptic ointments.
ZnO, a colorless crystalline compound, with a density of 5.7 g/cm3. Zinc oxide yellows upon roasting and does not melt; it sublimes at temperatures above 1800°C. It is insoluble in water. It is an amphoteric compound, dissolving in acids with the formation of the corresponding salts, as well as in alkalies and aqueous solutions of ammonia. Zinc oxide is encountered in nature as the mineral zincite (see). It is produced commercially by burning zinc vapor in the presence of air; zinc oxide is collected from the resultant smoke by cloth filters or other types of filters.
Zinc oxide is used in the rubber industry as an activator of vulcanization of many rubbers or as a vulcanizing agent of some rubbers, for example, chloroprene rubber. In the chemical industry, it is used as a catalyst for the synthesis of methanol and as a white paint pigment. It is also used in the production of perfumeries, cosmetics, and drugs (in the form of ointments, pastes, and powders for various skin conditions).
Zinc oxide powder is slightly toxic; its maximum permissible concentration in the air at places of work is 6 mg/m3.
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N. N. SEVRIUKOV