ZINC
- Atomic Number: 30
- Atomic Symbol: Zn
- Atomic Weight: 65.38
- Electron Configuration: -8-18-2
History:
-
(Ger. Zink, of obscure origin) Centuries before zinc was recognized
as a distinct element, zinc ores were used for making brass.
Tubal-Cain, seven generations from Adam, is mentioned as being an
"instructor in every artificer in brass and iron." An alloy
containing 87% zinc has been found in prehistoric ruins in
Transylvania. Metallic zinc was produced in the 13th century A.D. in
India by reducing calamine with organic substances such as wool. The
metal was rediscovered in Europe by Marggraf in 1746, who showed that
it could be obtained by reducing calamine with charcoal. The
principal ores of zinc are sphalerite (sulfide), smithsonite
(carbonate), calamine (silicate), and franklinite (zine, manganese,
iron oxide). Zinc can be obtained by roasting its ores to form the
oxide and by reduction of the oxide with coal or carbon, with
subsequent distillation of the metal. Other methods of extraction
are possible. Naturally occurring zinc contains five stable
isotopes. Sixteen other unstable isotopes are recognized. Zinc is a
bluish-white, lustrous metal. It is brittle at ordinary temperatures
but malleable at 100 to 150C. It is a fair conductor of electricity,
and burns in air at high red heat with evolution of white clouds of
the oxide. The metal is employed to form numerous alloys with other
metals. Brass, nickel silver, typewriter metal, commercial bronze,
spring bronze, German silver, soft solder, and aluminum solder are
some of the more important alloys. Large quantities of zinc are used
to produce die castings, used extensively by the automotive,
electrical, and hardware industries. An alloy called Prestal(R),
consisting of 78% zinc and 22% aluminum is reported to be almost as
strong as steel but as easy to mold as plastic. It is said to be so
plastic that it can be molded into form by relatively inexpensive die
casts made of ceramics and cement. It exhibits superplasticity.
Zinc is also used extensively to galvanize other metals such as iron
to prevent corrosion. Neither zinc nor zirconium is ferromagnetic;
but ZrZn2 exhibits ferromagnetism at temperatures below 35 K. Zinc
oxide is a unique and very useful material to modern civilization.
It is widely used in the manufacture of paints, rubber products,
cosmetics, pharmaceuticals, floor coverings, plastics, printing inks,
soap, storage batteries, textiles, electrical equipment, and other
products. It has unusual electrical, thermal, optical, and
solid-state properties that have not been fully investigated.
Lithopone, a mixture of zinc sulfide and barium sulfate, is an
important pigment. Zinc sulfide is used in making luminous dials,
X-ray and TV screens, and fluorescent lights. The chloride and
chromate are also important compounds. Zinc is an essential element
in the growth of human beings and animals. Tests show that
zinc-deficient animals require 50% more food to gain the same weight
as an animal supplied with sufficient zinc. Zinc is not considered
to be toxic, but when freshly formed ZnO is inhaled a disorder known
as the oxide shakes or zinc chills sometimes occurs. It is
recommended that where zinc oxide is encountered good ventilation be
provided to avoid concentration exceeding 5 mg/m^3, (time-weighted
over an 8-hour exposure, 40-hour work week). The price of zinc was
roughly $0.70/lb in January 1990.
Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond
Copyright ©1995-1998
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