Melvin Kennedy, age 15, of Pocatello, Idaho, for his question:
WHERE DO WE FIND ZINC?
Zinc is a shiny, bluish white metal that is important to industry. It is never found free in nature but always occurs as zinc oxide in the mineral zincite, as zinc oxide in the mineral himimorphite, as zinc carbonate in the mineral smithsonite, as a mixed oxide of zinc and iron in the mineral frankinite and as zinc sulfide in the mineral sphalerite.
The ores most commonly used as a source of zinc are smithsonite and sphalerite.
Leading zinc mining countries of the world, listed in order of their importance, are Canada, Russia, Australia, the United States and Peru.
Zinc is used as a coating applied to metals such as steel or iron to prevent them from rusting. The coated metal, called galvanized iron or steel, is used in such products as roof gutters and tank linings. Zinc is also used extensively in electric batteries.
Zinc can also be combined with other metals to form many alloys or mixtures. Bronze is copper, tin and zinc. Brass is an alloy of copper and zinc. Nickel silver is copper, nickel and zinc.
The first step in the process to transform the ores into zinc is often by subjecting them to high temperatures. The oxides are then reduced by carbon in an electric furnace, the zinc boiling and distilling in the retort in which the reduction takes place.
The zinc obtained by distillation contains small amounts of iron, arsenic, lead and cadmium and is known in metallurgy as spelter.
In another method of refining zinc, the roasted ores are leached with sulfuric acid. After the impurities have been removed, the solution is electrolyzed. Electrolytic zinc is pure and has superior qualities, such as high resistance to corrosion.
Annual mine production of zinc in the United States is about 15 percent of world production. Annual consumption of zinc in the U.S. is about 35 percent of world production.
Pure zinc is extremely brittle at ordinary temperatures, but becomes malleable between 248 and 302 degrees Fahrenheit and may be rolled into sheets between heated rollers.
Zinc is unaffected by dry air. In moist air it is oxidized and becomes coated with a carbonate film that protects it from further corrosion.
The metal melts at 787.1 degrees Fahrenheit and boils at 1,666 degrees Fahrenheit.
Zinc oxide, known as zinc white or Chinese white, is used as a pigment in paint. It is also used as a filler in rubber tires and is employed in medicine as an antiseptic ointment.
Zinc chloride is used as wood preservative and as a soldering fluid. Zinc sulfide is extremely useful in applications involving electroluminescence, photoconductivity and semi conductivity and has other electronic uses. It is employed as a prosphor for the screen of televisions tubes and in fluorescent coatings.