All About
Silver
Silver occurs natively and in ores such as argentite
(Ag2S) and horn silver (AgCl); lead, lead-zinc, copper, gold, and
copper-nickel ores are principal sources. Mexico, Canada, Peru,
and the U.S. are the principal silver producers in the western hemisphere.
Production
Silver is also recovered during electrolytic refining of copper.
Commercial fine silver contains at least 99.9% silver. Purities
of 99.999+% are available commercially.
Properties
Pure silver has a brilliant white metallic luster. It is a little
harder than gold and is very ductile and malleable, being exceeded
only by gold and perhaps palladium. Pure silver has the highest
electrical and thermal conductivity of all metals, and possesses
the lowest contact resistance. It is stable in pure air and water,
but tarnishes when exposed to ozone, hydrogen sulfide, or air containing
sulfur. The alloys of silver are important.
Uses
Silver jewelry is made in Mexico, U.S. & Peru primarily. Pure
silver is harder than gold but not as valuable. International codes
.999 Pure and .925 Sterling. Silver is used not only for coins and
jewelry but for dental alloys, bars, batteries and silverware.
Sterling silver is used for jewelry, silverware, etc. where appearance
is paramount. This alloy contains 92.5% silver, the remainder being
copper or some other metal. Silver is of the utmost importance in
photography, about 30% of the U.S. industrial consumption going
into this application. It is used for dental alloys. Silver is used
in making solder and brazing alloys, electrical contacts, and high
capacity silver-zinc and silver-cadmium batteries. Silver paints
are used for making printed circuits. It is used in mirror production
and may be deposited on glass or metals by chemical deposition,
electrode position, or by evaporation. When freshly deposited, it
is the best reflector of visible light known, but is rapidly tarnished
and loses much of its reflectance. It is a poor reflector of ultraviolet.
Silver fulminate, a powerful explosive, is sometimes formed during
the silvering process. Silver iodide is used in seeding clouds to
produce rain. Silver chloride has interesting optical properties
as it can be made transparent; it also is a cement for glass. Silver
nitrate, or lunar caustic, the most important silver compound, is
used extensively in photography. Silver for centuries has been used
traditionally for coinage by many countries of the world. In recent
times, however, consumption of silver has greatly exceeded the output.
Handling
While silver itself is not considered to be toxic, most of its
salts are poisonous. Exposure to silver (metal and soluble compounds,
as Ag) in air should not exceed 0.01 mg/m3, (8-hour time-weighted
average - 40 hour week). Silver compounds can be absorbed in the
circulatory system and reduced silver deposited in the various tissues
of the body. A condition, known as argyria, results with a grayish
pigmentation of the skin and mucous membranes. Silver has germicidal
effects and kills many lower organisms effectively without harm
to higher animals.
Cost
In 1939, the price of silver was fixed by the U.S. Treasury at
71 cents/troy oz., and at 90.5 cents/troy oz. in 1946. In November
1961 the U.S. Treasury suspended sales of nonmonetized silver, and
the price stabilized for a time at about $1.29, the melt-down value
of silver U.S. coins. The coinage act of 1965 authorized a change
in the metallic composition of the three U.S. subsidiary denominations
to clad or composite type coins. This was the first change in U.S.
coinage since the monetary system was established in 1792. Clad
dimes and quarters are made of an outer layer of 75% Cu and 25%
Ni bonded to a central core of pure Cu. The composition of the one-
and five-cent pieces remains unchanged. One-cent coins are 95% Cu
and 5% Zn. Five-cent coins are 75% Cu and 25% Ni. Old silver dollars
are 90% Ag and 10% Cu. Earlier subsidiary coins of 90% Ag and 10%
Cu officially were to circulate alongside the old coins; however,
in practice they have largely disappeared (Gresham's Law), as the
value of the silver is now greater than their exchange value. Silver
coins of other countries have largely been replaced with coins made
of other metals. On June 24, 1968, the U.S. Government ceased to
redeem U.S. Silver Certificates with silver. As of January 1990,
the price of silver was about $5.25/troy oz.; however, the price
has fluctuated considerably due to market instability.
For more information please see http://periodic.lanl.gov/elements/47.html
Money For Gold is a Division of
James
Diamonds National Jewelry Mfg., Inc.
42-44 Pocono Blvd. Mount Pocono PA 1-800-246-4436
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