Zinc
Zinc is a metal of major importance in our modern world. The symbol for zinc is Zn and its atomic weight is 65.37. Zinc is derived from the Greek word Zink, meaning metal. Zinc first appeared in the Middle Ages in India as well as China. Extraction of zinc, however, did not occur until the 1740's. Being the 25th most abundant element, Zinc is widely spread throughout nature.
Zinc Normally appears dull gray in color due to an oxide or carbonate coating, but when polished has a bluish white luster. The element is quite brittle at room temperature but moderately hard. It is a descent conductor of electricity. Pure zinc has a boiling point of 419.5 degrees Celsius. The physical characteristics of zinc can be generic but the chemical characteristics are much more unique.
Zinc is part of the d block of the periodic table. It resides in the 4th period, 12th group. It has an electron configuration of 1s22s22p63s23p64s23d10. The metal acts as a good reduction agent and therefore has many laboratory applications. Zinc dissolves in aqueous acid and bases, forming hydrogen gas and zinc ions. Compounds are only formed from zinc in the +2 Oxidation State.
To produce zinc a miner must first mine either sulfide or carbonate ores. They are then concentrated by selective sedimentation and allowed to roast in air to form the oxide, ZnO. From here there are two processes by which the manufacturer may recover the metal from the oxide. First the pyrometallurical process may be used. In this procedure the oxide and carbon, in the form of coal, are mixed and heated to a high temperature. The carbon then reduces the oxide to metal, which is then distilled from the tank. In the second process, hydrometallurical, the purest zinc can be formed. First the ore is treated with sulfuric acid to make a solution of zinc sulfate. The pH is adjusted to remove impurities and then the metal is recovered using electrolytic reduction.
Zinc is an extremely important element. Its main purpose is galvanization, but is also used in alloys and medicines. When steel and iron are coated with zinc it prevents rusting and corrosion. Zinc reacts this way because it is a stronger reducing agent. As long as zinc is in contact with iron it will only acts as an electrical conductor to transfer electrons from zinc to oxygen. The best know zinc alloy is brass, a mixture between copper and anywhere from 3-45% zinc. Zinc is also used as a die-casting alloy consisting of 96% zinc, 4% aluminum, and trace amounts of magnesium. The most widely used zinc compounds are the oxide, the sulfide, and the chloride. The oxide is a rubber tire reiforcer, a white paint pigment, a ceramic glaze, and an opaque base in cosmetics. The sulfide is used as a phosphor in cathode ray tubes and fluorescent lamps as well as a white pigment. The chloride is useful as a soldering flux, a dry-cell battery electrolyte, and a wood preservative.
Zinc is an essential trace element in plant and animal life and is of very low toxicity in its ordinary compounds. A zinc deficiency in the human diet produces anemia and slows growth. Contemporarily, zinc is also being used in cold medicines and lozenges.