Zinc, also referred to in nonscientific contexts as spelter, is a
bluish-white, lustrous, diamagnetic metal, though most common commercial grades
of the metal have a dull finish. It is somewhat less dense than iron and has a
hexagonal crystal structure.
Zinc , with CAS number of
7440-66-6,
can be called Asarco L 15 ; Blue powder ; CCRIS 1582 ; Emanay zinc dust ;
Granular zinc ; Lead refinery vacuum zinc ; Rheinzink ; Merrillite .
The metal is hard and brittle at most temperatures but becomes malleable
between 100 and 150 °C. Above 210 °C, the metal becomes brittle again and can be
pulverized by beating. Zinc is a fair conductor of electricity. For a metal,
zinc has relatively low melting (419.5 °C, 787.1 F) and boiling points (907 °C).
Its melting point is the lowest of all the transition metals aside from mercury
and cadmium.
Many alloys contain zinc, including brass, an alloy of copper and zinc. Other
metals long known to form binary alloys with zinc are aluminium, antimony,
bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel,
tellurium and sodium. While neither zinc nor zirconium are ferromagnetic, their
alloy ZrZn2 exhibits ferromagnetism below 35 K.
1. History
1). Ancient use
Various isolated examples of the use of impure zinc in
ancient times have been discovered.Ornaments made of alloys that contain 80–90%
zinc with lead, iron, antimony, and other metals making up the remainder, have
been found that are 2500 years old.
2). Early studies and naming
Zinc was distinctly recognized as a metal
under the designation of Fasada in the medical Lexicon ascribed to the Hindu
king Madanapala and written about the year 1374. Smelting and extraction of
impure zinc by reducing calamine with wool and other organic substances was
accomplished in the 13th century in India.The Chinese did not learn of the
technique until the 17th century.
Some alchemists called zinc oxide lana
philosophica, Latin for "philosopher's wool".a Swiss-born German alchemist
referred to the metal as "zincum" or "zinken" in his book Liber Mineralium II,
in the 16th century. The metal was also called Indian tin, tutanego, calamine,
and spinter.
3). Isolation of the pure element
William Champion's brother, John,
patented a process in 1758 for calcining zinc sulfide into an oxide usable in
the retort process. Prior to this only calamine could be used to produce zinc.
In 1798, Johann Christian Ruberg improved on the smelting process by building
the first horizontal retort smelter. Jean-Jacques Daniel Dony built a different
kind of horizontal zinc smelter in Belgium, which processed even more
zinc.
Italian doctor Luigi Galvani discovered in 1780 that connecting the spinal
cord of a freshly dissected frog to an iron rail attached by a brass hook caused
the frog's leg to twitch.The galvanic cell and the process of galvanization were
both named for Luigi Galvani and these discoveries paved the way for electrical
batteries, galvanization and cathodic protection.
Galvani's friend, Alessandro Volta, continued researching this effect and
invented the Voltaic pile in 1800.The basic unit of Volta's pile was a
simplified galvanic cell.
The non-magnetic character of zinc and its lack
of color in solution delayed discovery of its importance to biochemistry and
nutrition. This changed in 1940 when carbonic anhydrase, an enzyme that scrubs
carbon dioxide from blood, was shown to have zinc in its active site. The
digestive enzyme carboxypeptidase became the second known zinc-containing enzyme
in 1955.
2. Uses
Zinc (CAS NO.7440-66-6) metal is most commonly used as an anti-corrosion
agent. The zinc metal was used for galvanization, which is used on chain-link
fencing, guard rails, suspension bridges, lightposts, metal roofs, heat
exchangers, and car bodies. Zinc is also used to cathodically protect metals
that are exposed to sea water from corrosion. With an electrochemical potential
of ?0.7618 volts, zinc makes a good material for the negative terminus or anode
in batteries.Powdered zinc is used in this way in alkaline batteries and sheets
of zinc metal form the cases for and act as anodes in zinc-carbon
batteries.
A widely used alloy of zinc is brass, which is useful in communication
equipment, hardware, musical instruments, and water valves. Other widely used
alloys that contain zinc include nickel silver, typewriter metal, soft and
aluminum solder, and commercial bronze.Zinc is also used in contemporary pipe
organs as a substitute for the traditional lead/tin alloy in pipes. Alloys of
primarily zinc with small amounts of copper, aluminium, and magnesium are useful
in die casting as well as spin casting, especially in the automotive,
electrical, and hardware industries.
Zinc oxide is widely used as a white pigment in paints, and as a catalyst in
the manufacture of rubber. It is also used as a heat disperser for the rubber
and acts to protect its polymers from ultraviolet radiation. Zinc chloride can
be used as a wood preservative.It is also used to make other chemicals.
Zinc
methyl (Zn(CH3)2) is used in a number of organic syntheses.Zinc sulfide (ZnS) is
used in luminescent pigments such as on the hands of clocks, X-ray and
television screens, and luminous paints.Crystals of ZnS are used in lasers that
operate in the mid-infrared part of the spectrum. Zinc sulphate is a chemical in
dyes and pigments. Zinc pyrithione is used in antifouling paints. Zinc powder is
sometimes used as a propellant in model rockets.Zinc sheet metal is used to make
zinc bars.
Zinc is included in most single tablet over-the-counter daily vitamin and
mineral supplements. Zinc gluconate glycine and zinc acetate are used in throat
lozenges or tablets to reduce the duration and the severity of cold symptoms.
Zinc lactate is used in toothpaste to prevent halitosis.
3. Production
Roasting converts the zinc sulfide concentrate produced during processing to
zinc oxide:
2ZnS + 3 O2 → 2ZnO + 2SO2
Pyrometallurgy processing reduces zinc oxide with carbon or carbon monoxide
at 950 °C (1,740 °F) into the metal, which is distilled as zinc vapor.
2 ZnO + C → 2 Zn + CO2
2 ZnO + 2CO → 2 Zn + 2 CO2
