Zinc
Zinc is a chemical element with the symbol Zn. It is a low-melting metal
that
belongs to Group IIb (zinc group) of the periodic table. The atomic
number of
zinc is 30. With an atomic weight of 65.39, zinc makes up an
average of 65 grams
of every ton of Earth's crust, which makes it a little
more abundant than
copper. The melting point of zinc is 420 degrees Celsius
and its boiling point
is 907 degrees Celsius (Britannica Online). Zinc is the
second most common trace
metal, after iron, that is found naturally in the
human body. It is also the
third most used nonferrous metal (after aluminum
and copper), of which the U.S.
consumes more than one million metric tons
annually (American Zinc Association).
According to the U.S. Bureau of
Mines, the average person will use 730 pounds of
zinc in his or her lifetime.
Metallic zinc appeared much later in history than
the other common metals.
"The Ancient Egyptians were the first to use zinc
although they did so
unintentionally! They made their brass from copper ores
that were
contaminated with zinc" (Knapp, 4). There is some evidence that
the Greeks
knew of zinc's existence. They called it pseudargyras, or "false
silver," but
they had no method of producing it in quantity. The Romans
produced
considerable quantities of brass, an alloy of zinc and copper, as early
as
200 B.C. The metallurgists of India seem to have isolated the
individual
metal as early as the 13th century; and by the 16th century, China
had achieved
large-scale production. In the West, commercial zinc production
got under way by
the middle of the 18th century in England under the
leadership of William
Champion (Britannica Online). The first complete
study of zinc was published in
1746 by Sigismund Marggraf, a German
chemist (World Book). Canada is the leading
producer of zinc followed by
Australia, China, Peru, the U.S. and Mexico. In the
U.S., mine production
comes mostly from Alaska, Tennessee, New York, and
Missouri (World
Almanac, 151). There are 47 tons of zinc in one cubic mile of
seawater. Zinc
deposits occur in two quite different ways: first, as
hydrothermal or contact
metamorphic deposits, and second, as sedimentary
deposits. Zinc was used as a
component of brass until the 18th century. More
than 50% of production is
consumed in the preparation of alloys for die-cast
products, and in
anticorrosion treatment of iron and steel (Skinner, 19). A
large share of the
zinc produced today is used for galvanizing iron and steel
(that is, coating
them with zinc to make them rustproof). For many purposes,
zinc is simply
flattened into sheets called "rolled zinc." These
sheets are used in the
manufacture of many roofing products, refrigerator
linings, and printing
plates. The compounds of zinc have numerous uses. Because
of its high heat
conductivity, zinc oxide is used in rubber as a heat
dissipater. It is also
used in the making of cosmetics, plastics, skin
ointments, and soaps. Zinc
sulfate is used in weed killers. Zinc sulfide has
been used in X-ray screens
and in luminous dials for clocks and watches
(Compton's Encyclopedia). Zinc
is also used in electric batteries and is
required for the normal growth and
healing of plants and animals. Zinc can also
be combined with other metals to
form many other alloys (mixtures). For example,
brass is an alloy of copper
and zinc. Bronze is copper, tin, and zinc. And
nickel silver is copper,
nickel, and zinc (World Book). The following statistics
are stated in the
U.S. Geological survey, U.S. Dept. of the Interior. As of
mid-1996, the world
mineral reserve for zinc was 330 million metric tons. U.S.
Zinc
Production, 1950-95 (in thousand metric tons) 1950 565,516 1989
275,883
1960 395,013 1990 515,355 1965 554,429 1991 517,804 1970 484,560
1992 523,440
1975 425,792 1993 488,283 1980 317,103 1994 570,162 1985
226,545 1995 601,000 In
1950 the total production of zinc was 565,515
thousand metric meters. The
estimated total reserves for 1950 was 85,000,000
metric tons, but that was
before the enormous amount of native zinc was
discovered in Australia (Skinner,
62). In the year 2000, the projected
total of zinc production is 550,000
thousand metric meters and the total
world reserve will be at an estimated
320,500,000 metric tons. In the
year 2050, I expect the total production of zinc
to be around significantly
greater than it was 100 years from then. From
examining the chart above, I
have come to the conclusion that the world reserve
will not be that greatly
affected (considering the increasing amount of
technology that is available
to us and the large amount of the total reserves
today). The mineral zinc has
not been over mined since its existence, and I do
not expect it to be
completely exhausted by the year 2050. I think that in the
year 2050 the
world is going to be completely different as we know it. I expect
the
downfall of computers to be solved by then and a huge increase in
the
industrial development. Hence, creating a greater demand for all
resources
including zinc.
Bibliography
Knapp, Brian;
Zinc,Cadium,and Mercury. New York: Atlantic Europe Publishing
Company
Limited, 1996. Rosenbaum, Garvin; World Without Plenty. Skokle,
Ill:
National Textbook Co.,1975. Skinner, Brian; Earth Resources. New
Jersey:
Prentice Hall Inc., 1969. Matthews, Robert; Beyond 2000.
Providence, RH: Global
Dynamics Press, 1989. The World Almanac. United
States: K-III Reference
Corporation, 1996. "Zinc" Compton's Encyclopedia
Online.
*"http://www.optonline.com/comptons/ceo* "Zinc group
elements"
Encyclopedia Britannica Online.
*http://www.members.eb.com/bol/* "American
Zinc Association"
*http://www.org/zincfacts.html "World Book"
http://
medusa.fs.altip.oclc.org/