![]() ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate. Solid zinc oxide will also dissolve in alkalis to give soluble zincates: It is nearly insoluble in water, but it will dissolve in most acids, such as hydrochloric acid: ZnO + 2 HCl → ZnCl 2 + H 2O This color change is caused by a small loss of oxygen to the environment at high temperatures to form the non-stoichiometric Zn 1+xO, where at 800 ☌, x = 0.00007. Ĭrystalline zinc oxide is thermochromic, changing from white to yellow when heated in air and reverting to white on cooling. Pure ZnO is a white powder, but in nature it occurs as the rare mineral zincite, which usually contains manganese and other impurities that confer a yellow to red color. This application was soon displaced by titanium. High-quality ZnO produced by the "French process" was added to photocopying paper as a filler. In the 1970s, the second largest application of ZnO was photocopying. In recent times, most zinc oxide was used in the rubber industry to resist corrosion. All those paintings developed cracks over the years. For example, during the late 1890s and early 1900s, some artists used zinc white as a ground for their oil paintings. Because zinc white is so "clean" it is valuable for making tints with other colors, but it makes a rather brittle dry film when unmixed with other colors. The success of zinc white paint was due to its advantages over the traditional white lead: zinc white is essentially permanent in sunlight, it is not blackened by sulfur-bearing air, it is non-toxic and more economical. In 1845, Edme-Jean Leclaire in Paris was producing the oil paint on a large scale, and by 1850, zinc white was being manufactured throughout Europe. This problem was solved by optimizing the synthesis of ZnO. Zinc white was accepted as a pigment in oil paintings by 1834 but it did not mix well with oil. The main usage of zinc oxide (zinc white) was in paints and as an additive to ointments. Around 1782 Louis-Bernard Guyton de Morveau proposed replacing lead white pigment with zinc oxide. In 1743, the first European zinc smelter was established in Bristol, United Kingdom. From India, zinc manufacture moved to China in the 17th century. įrom the 12th to the 16th century zinc and zinc oxide were recognized and produced in India using a primitive form of the direct synthesis process. Zinc oxide has also been recovered from zinc mines at Zawar in India, dating from the second half of the first millennium BC. This process was described by Dioscorides in the 1st century AD. This liberated metallic zinc as a vapor, which then ascended the flue and condensed as the oxide. The zinc oxide is thought to have been produced by heating zinc ore in a shaft furnace. The Romans produced considerable quantities of brass (an alloy of zinc and copper) as early as 200 BC by a cementation process where copper was reacted with zinc oxide. It is used as an ingredient in products such as baby powder and creams against diaper rashes, calamine cream, anti- dandruff shampoos, and antiseptic ointments. Galen suggested treating ulcerating cancers with zinc oxide, as did Avicenna in his The Canon of Medicine. Zinc oxide ointment is also mentioned by the Greek physician Dioscorides (1st century AD). The use of pushpanjan, probably zinc oxide, as a salve for eyes and open wounds, is mentioned in the Indian medical text the Charaka Samhita, thought to date from 500 BC or before. ![]() Zinc compounds were probably used by early humans, in processed and unprocessed forms, as a paint or medicinal ointment, but their composition is uncertain. Although it occurs naturally as the mineral zincite, most zinc oxide is produced synthetically. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement, lubricants, paints, sunscreens, ointments, adhesives, sealants, pigments, foods, batteries, ferrites, fire retardants, semi conductors, and first-aid tapes. ![]() It is a white powder that is insoluble in water. Zinc oxide is an inorganic compound with the formula Zn O. ![]()
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