Цинк оксид

Химические свойства

Zinc oxide is an amorphous, white or yellowish-white powder. It is a fine white powder that becomes yellow at temperatures above 3000℃. It is an amphoteric oxide that reacts with acids and dissolves in alkaline solution with formation of zincates. Its density and oil absorption value are 5.6 g/cm³ and 10-25 g oil/100 g ZnO, respectively.

Физические свойства

White or yellowish-white powder; odorless; bitter taste; hexagonal crystal; refractive index 2.008; density 5.606 g/cm³; melts at 1,975°C; practically insoluble in water, 1.6 mg/L at about 30°C; soluble in dilute acids, ammonia solu 990 tion, and alkali hydroxides.

Использование

zinc oxide has been used to protect, soothe, and heal the skin. Zinc oxide provides an excellent barrier to the sun and other irritants. It is somewhat astringent, anti-septic, and anti-bacterial. When used in sunscreen preparations, it provides both uVA and uVB protection, and can contribute to and/or increase SPF. At the appropriate particle size, zinc oxide is transparent in the visible light spectrum but opaque in the uVC ranges, thereby avoiding a whitening effect when incorporated into sunscreen preparations. Zinc oxide is included on the FDA’s list of approved sunscreen chemicals. It demonstrates an impressive synergistic effect when combined with organic sunscreens. Zinc oxide is also used when a white color is desired for a product. It is obtained from zinc ore, a commonly found mineral, and is relatively non-allergenic.

Подготовка

Zinc oxide is obtained as an intermediate in recovering zinc from minerals (See Zinc, Recovery). The oxide is prepared by vaporizing zinc metal and oxidation of the zinc vapors with preheated air (French process). The oxide can be produced by other processes. Another method involves roasting franklinite and other ores with coal and then oxidizing the product in air.

прикладной

ZnO is used primarily for its anti-bacterial and fungicidal properties. Also, in the United States, ZnO is regarded as a Category I skin protectant and a Category III sunscreen.

Определение

zinc oxide: A powder, white whencold and yellow when hot, ZnO; r.d.5.606; m.p. 1975°C. It occurs naturallyas a reddish orange ore zincite,and can also be made by oxidizinghot zinc in air. It is amphoteric,forming zincates with bases. It isused as a pigment (Chinese white) and a mild antiseptic in zinc ointments.An archaic name is philosopher’swool.

Общее описание

Crude zinc oxide is a yellow-gray granular solid with no odor. Zinc oxide has a specific gravity of 4.4. Zinc oxide is insoluble in water. The primary hazard is the threat posed to the environment. Immediate steps should be taken to limit its spread to the environment. Prolonged inhalation of the dust may result in metal fume fever with symptoms of chills, fever, muscular pain, nausea and vomiting.

Реакции воздуха и воды

Slowly decomposed(hydrolyzed) in water. Insoluble in water.

Профиль реактивности

ZINC OXIDE is insoluble in water. What little solubility Zinc oxide has yields aqueous solutions that are neutral in pH. Intimate mixtures of zinc oxide and chlorinated rubber with or without hydrocarbons or chlorinated solvent react violently, even explosively upon heating [Chem. Trade J., 1962, 151, 672]. Slow addition of zinc oxide to cover the surface of linseed oil varnish caused generation of heat and ignition, [Chem. Trade J., 1933, 92, 278].

Опасность

Exposure to zinc oxide fumes from welding and other operations can cause metal fume fever. Its symptoms are chills, fever, cough, and tightness in the chest.

Угроза здоровью

Exposures to zinc oxide metal fume cause several health disorders. The symptoms of toxicity include, but are not limited to, fever, chills, muscle ache, nausea, fever, dry throat, cough; lassitude (weakness, exhaustion), metallic taste, headache, blurred vision, low back pain, vomiting, malaise (vague feeling of discomfort), chest tightness, dyspnea (breathing diffi culty) and decreased pulmonary function. The overexposure to zinc oxide fumes in workplaces produce symptoms known as metal fume fever or “zinc shakes”; an acute, selflimiting condition. Chronic exposure to zinc oxide may cause respiratory tract irritation with nasopharyngitis and laryngitis.

Пожароопасность

Some may burn but none ignite readily. Containers may explode when heated. Some may be transported hot.

Сельскохозяйственное использование

Zinc oxide (ZnO) is a zinc fertilizer. It is a white powder when cold and yellow when hot, and contains approximately 78% zinc.
Zinc oxide occurs in nature as a reddish-orange colored zincite, and is made by oxidizing hot zinc in air. It is an amphoteric oxide forming zincates, by reacting with bases and zinc salts with acids. It is used as a white pigment and as a mild antiseptic in ointments. An archaic name of zinc oxide is philosopher's wool.
Foliar applications with zinc oxide reduce the foliage damage. Zinc oxide, applied by way of seed coatings, root dips or tree injections, corrects the zinc deficiency. Dipping potato seeds in 2% zinc oxide suspension overcomes zinc deficiency satisfactorily. A similar method is used for pre-plant dipping of the roots of rice seedlings.

Фармацевтические приложения

The pharmaceutical and cosmetic industries use ZnO in powders and ointments because of its bactericidal properties. It is also used to form dental cements by its reaction with eugenol.
Zinc oxide is used as a raw material for many products: stearates, phosphates, chromates, bromates, organic dithiophosphates, and ferrites (ZnO, MnO, Fe2O3). It is used as a source of zinc in animal feeds and in electrogalvanization . It is also used for desulfurizing gases.

Промышленное использование

Zinc oxide has many uses. By far the most important is in the rubber industry. Almost half the world’s ZnO is used as an activator for vulcanization accelerators in natural and synthetic rubber. The reactivity of the ZnO is a function of its specific surface area, but is also influenced by the presence of impurities such as lead and sulfates. The ZnO also ensures good durability of the vulcanized rubber, and increases its thermal conductivity. The ZnO content is usually 2–5%.
In paints and coatings, zinc oxide is no longer the principal white pigment, although its superb white color is used by artists. It is used as an additive in exterior paints for wood preservation. It is also utilized in antifouling and anticorrosion paints [2.82]. It improves film formation, durability, and resistance to mildew (having a synergistic effect with other fungicides) because it reacts with acidic products of oxidation and can absorb UV radiation.
In the field of glass, ceramics, and enamels, ZnO is used for its ability to reduce thermal expansion, to lower the melting point, and to increase chemical resistance. It can also be used to modify gloss or to improve opacity.

Использование в материалах

The highest purity material is calcined with additives such as Bi2O3 and used in the manufacture of varistors. The photoconducting properties of ZnO are used in photoreproduction processes. Doping with alumina causes a reduction in electrical resistance; hence, it can be used in the coatings on the master papers for offset reproduction.
Zinc oxide is used as a catalyst in organic syntheses (e.g., of methanol), often in conjunction with other oxides. It is present in some adhesive compositions.

Профиль безопасности

Moderately toxic to humans by ingestion. Poison experimentally by intraperitoneal route. An experimental teratogen. Other experimental reproductive effects. Human systemic effects by inhalation of freshly formed fumes: metal fume fever with chills, fever, tightness of chest, cough, dyspnea, and other pulmonary changes. Mutation data reported. A s h and eye irritant. Has exploded when mixed with chlorinated rubber. Violent reaction with Mg, linseed oil. When heated to decomposition it emits toxic fumes of ZnO. See also ZINC COMPOUNDS.

Возможный контакт

Zinc oxide is primarily used as a white pigment in rubber formulations and as a vulcanizing aid. It is also used as an antiinflammatory agent; in photo copying; paints, chemicals, ceramics, lacquers, and varnishes; as a filler for plastic; in cosmetics; pharmaceuticals, and calamine lotion. Exposure may occur in the manufacture and use of zinc oxide and products, or through its formation as a fume when zinc or its alloys are heated. HC may have been used as a Choking/Pulmonary Agent.

Канцерогенность

In general, genotoxic studies have not found evidence for mutagenicity of zinc.

Перевозки

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required.

Несовместимости

Incompatible with linseed oil, magnesium. Contact with chlorinated rubber (@ 215C) may cause a violent reaction. Slowly decomposed by water.