Patty Osten, age 11, of Phoenix, Arizona, for his question:
What are the uses of zinc?
Pale, bluish white zinc shows its face on so called tin roofs and galvanized metal buckets, but most of its duties are done behind the scenes where it is unrecognizable. There is zinc in a bulky auto engine and zinc in the delicate wheels of a watch. More of the dull metal is hidden in glossy white paints and even in the medicine kit.
Zinc is a rather heavy metallic element which has the rough touch of iron but un¬like iron, zinc will not rust in the air. Zinc is not as strong or plentiful as iron, and it is more practical to use iron and steel for most outdoor construction, even though it must be rust proofed. But rustless zinc can be used for small outdoor structures, and sheets of zinc may be rolled out to make roofs. We use a process called galvanizing to make our limited supplies of zinc stretch even further.
Steel car. be used to make a sturdy bucket but it soon rusts away. If the bucket is dipped into molten zinc it gets a coating of rustproof metal to protect it. The bucket is galvanized steel. Electrolysis is another method for galvanizing rust¬prone metals with zinc. Sheets of steel and other metals are placed in chemical baths and an electric current covers them with thin shields of zinc, atom by atom.
We can see the zinc in roofs and rain spouts, in dies for cutting shapes and metal blocks for printing letters. But most of the zinc in our everyday lives is invisible. It is combined with other elements or alloyed with other metals. Compounds and alloys cause an element to change its appearance and its nature. The U.S. mines more than half a million tons of zinc a year and about half of it is molded, rolled and galvanized.
Most of the rest is melted with copper and other metals to make brass and bronze. These zinc alloys are shiny and hard but the zinc color is hidden. Glossy yellow brass may be 30% zinc and 70% copper. Handsome red brass has less zinc. Sturdier brass alloys containing concealed zinc, copper and other ingredients are used to make bearings and other hard working machine parts for cars, boats and planes. When lead is added, a brass alloy can be machine cut to make the delicate wheels that keep a watch ticking. When you go on a trip, zinc and its alloys help print the timetable, get you there and get you there on time.
More zinc works hidden behind the scenes in chemical compounds such as zinc oxide and zinc sulfate. Molecules of zinc and oxygen form a snowy white substance used to make paints and cement for filling tooth cavities. This zinc oxide is also used in powdery cosmetics and as a filler in rubber goods. Zinc and sulfur form a white crystal compound. Both zinc oxide and zinc sulfate are used in soothing germicide ointments.
Zinc gave a big boost to human progress in the past, though nobody suspected this until about 300 years ago. Nature's zinc deposits are concealed in ores with other minerals, often with copper. And copper was the first metal our ancestors learned to smelt. Historians suspect that zinc was present in their copper ores and without know¬ing how or why, they produced bronze and brass alloys that were harder and more useful than either copper or zinc.