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| Atomic Number: | 47 | Atomic Symbol: | Ag | | Atomic Weight: | 106.4 | Electron Configuration: | 2-8-18-18-1 | | Shells: | 2,8,18,18,1 | Filling Orbital: | 4d10 | | Melting Point: | 961.93oC | Boiling Point: | 2212oC | | Description: | Soft silver metal | | Uses: | Used in alloys for jewelry and in other compounds for photography.
It is also a good conductor, but expensive. |
History(Anglo-Saxon, Seolfor siolfur; L. argentum). Silver has been
known since ancient times. It is mentioned in Genesis.
SourcesSlag dumps in Asia Minor and on islands in the Aegean Sea
indicate that man learned to separate silver from lead as early as 3000 B.C.
Silver occurs native 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. 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.
Uses- The alloys of silver are important.
- 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, electrodeposition, or by evaporation.
- When freshly deposited, it is the best reflector of visible light known, but
is rapidly tarnished and loses much of its relectance.
- 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.
HandlingWhile 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/m^3, (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 greyish pigmentation of the skin and mucous
membranes.
Silver has germicidal effects and kills many lower organisms
effectively without harm to higher animals.
CoinageSilver 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.
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.
CostsSince that time, the price of silver has fluctuated widely.
As
of January 1990, the price of silver was about $5.25/troy oz.; however, the
price has fluctuated considerably due to market instability.
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