My Saved Article
| Atomic Number: | 30 | Atomic Symbol: | Zn | | Atomic Weight: | 65.38 | Electron Configuration: | 2-8-18-2 | | Shells: | 2,8,18,2 | Filling Orbital: | 3d10 | | Melting Point: | 419.58oC | Boiling Point: | 907oC | | Uses: | galvanizing other metals, in alloys, solder, cosmetics &
pigments |
History(German 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 percent 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 Andreas Marggraf of Germany in 1746, who showed that it could be
obtained by reducing calamine with charcoal.
SourcesThe principal ores of zinc are sphalerite (sulfide), smithsonite
(carbonate), calamine (silicate), and franklinite (zine, manganese, iron oxide).
One method of zinc extraction involves roasting its ores to form the oxide and
reducing the oxide with coal or carbon, with subsequent distillation of the
metal.
IsotopesNaturally occurring zinc contains five stable isotopes. Sixteen
other unstable isotopes are recognized.
PropertiesZinc is a bluish-white, lustrous metal. It is brittle at
ordinary temperatures but maleable 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.
It exhibits superplasticity. Neither zinc nor zirconium
is ferromagnetic; but ZrZn2 exhibits ferromagnetism at temperatures below 35 K.
It has unusual electrical, thermal, optical, and solid-state properties that
have not been fully investigated.
UsesThe 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, which are used
extensively by the automotive, electrical, and hardware industries. An alloy
called Prestal(R), consisting of 78 percent zinc and 22 percent aluminum, is reported to be almost as strong as steel and as
easy to mold as plastic. The alloy said to be so moldable that it can be molded
into form using inexpensive ceramics or cement die casts.
Zinc is also used extensively to galvanize other metals such as iron to prevent corrosion. Zinc oxide is a unique and very
useful material for 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. 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 percent more food to gain the same weight as
an animal supplied with sufficient zinc.
HandlingZinc 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. Where zinc oxide is encountered, recommendations include
providing good ventilation to avoid concentration exceeding 5 mg/m^3,
(time-weighted over an 8-hour exposure, 40-hour work week).
CostsThe price of zinc was roughly $0.70/lb in January 1990.
|
|
|