Zinc

Zinc is strong and easy to mold, so it is alloyed with many other metals to form brass (with copper), nickel silver, typewriter metal, commercial bronze, spring brass, German silver, soft solder, aluminum solder, etc.   It is used to produce die castings for the automotive, electrical and hardware industries.   An alloy of 78% zinc and 22% aluminum, called Prestal, is almost as strong as steel and as easy to mold as plastic.   Zinc is used to galvanize other metals, such as iron, to prevent corrosion.   Zinc oxide is used to make paints, rubber products, cosmetics, medicines, floor coverings, plastics, printing ink, soap, storage batteries, textiles, electrical equipment, and other products.   Zinc sulfide is used to make luminous dials, X-ray and TV screens, and fluorescent lights. ^{Lide 4-34}

Zinc is essential to life.   In 1939, the Russian-born British biochemist, David Keilin, showed that a small amount of zinc was necessary for the working of the enzyme carbonic anhydrase, which is life-essential. ^{Asimov 610}   Since that time, zinc has been found in about 100 enzymes.   Sources: meat, liver, eggs, poultry, seafood, milk, whole grains, raw seeds, brewer's yeast.   Humans show no deficiency. ^{Brody 187, Netzer 803} Tests show that zinc-deficient animals need 50% more food to gain the same weight as an animal supplied with sufficient zinc. ^{Lide 4-34}

In plants, zinc is a component of the many plant enzymes.   It is essential to carbohydrate metabolism, protein synthesis and stem growth.   Deficient plants have mottled leaves with irregular chlorotic areas.   Zinc deficiency leads to iron deficiency, causing similar symptoms.   This can occur in eroded soils where the pH range of 5.5 - 7.0.   Lowering the pH can make zinc more available, but excessive zinc is toxic.^{Morgan n.p.}

Zinc was known to the ancients and in 13th century India, but was discovered in Europe by Margraaf in 1746.   Zinc ores are sphalerite or blende (sulfide), smithsonite (carbonate), calamine (silicate), and franklinite (zinc, manganese, iron oxide).   Zinc is isolated by roasting the ores to form the oxide and then reducing the oxide with coal or carbon and finally distilling the metal. ^{Lide 4-34}