13 октября, 2015 
Pokraskin 2.3.1
Introduction
Zinc oxide [1314-13-2], ZnO, Mr 81.38, was formerly used only as a white pigment, and was named zinc white (C. I. Pigment White 4), Chinese white, or flowers of zinc.
The term zinc white now denotes zinc oxide produced by the combustion of zinc metal according to the indirect or French process.
Historical Aspects: Zinc oxide has long been known as a byproduct of copper smelting. The Romans called it “cadmia” and used it as such in the production of brass. They also purified it for use in ointments by reduction followed by oxidation. In the Middle Ages, the alchemists thought that cadmia could be converted into gold.
In the mid-18th century, the German chemist Cramer discovered that cadmia could be obtained by the combustion of metallic zinc. Courtois began to produce zinc white in 1781 in France, but it was not until 1840 that industrial production was started by Leclaire (indirect or French process). The use of this white pigment spread rapidly. Zinc oxide replaced white lead because it had the advantages of being nontoxic, of not darkening in the presence of sulfurous gases, and of having better hiding power.
Around 1850, S. Wetherill of the New Jersey Zinc Company perfected a roasting furnace in which a grate was charged with coal and then covered with a mixture of zinc ore and coal. The zinc was reduced by the partial combustion of the coal and reoxidized at the furnace exit (direct or American process). These furnaces were subsequently improved but are now no longer used in Europe and America but are still in operation in China. During the second half of the nineteenth century, the use of ZnO in rubber was introduced to reduce the time needed for vulcanization. The discovery of the first organic accelerators for vulcanization in 1906 added to the importance of ZnO, which acts as an activator in these materials.
A third industrial production process exists but this wet process is less widely used.
2.3.2
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