Ag
SILVER
(Anglo-Saxon Seoffor siolfur, L. argentum)
Ag at. wt. 107.870
at. no. 47
m.p. 961.93°C
b.p. 2212°C
sp. gr. 10.50 (20°C)
valence 1, 2.
Electronic configuration
| SHELL |
K |
L |
M |
N |
O |
P |
Q |
| SUB SHELL |
He |
Neon |
Argon |
Krypton |
Xenon |
Radon |
Eka-radon |
| 1s |
2s 2p |
3s 3p |
3d 4s 4p |
4d 5s 5p |
4f 5d 6s 6p |
5f 6d 7s 7p |
| Silver
|
1s22s22p63s23p63d104s24p64d105s1 |
|
|
| Symbol
|
2S½ |
Silver has been
known since ancient times. It is mentioned in Genesis. Slag
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 (AgCI); lead, lead-zinc,
copper, gold, and copper-nickel ores are principal sources.
Mexico, Canada, Peru, and the United States are the
principal silver producers in the Western Hemisphere.
Silver is also recovered during electrolytic refining of
copper. Commercial fine silver contains at least 99.90%
silver. Purities of 99.999+ % are available commercially.
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
stakle in pure air and water, but tarnishes when exposed to
ozone, hydrogen sulfide, or air containing sulfur. 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 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 eyaporation. When freshly deposited, it is the best reflector of visible light known, but it rapidly tarnishes and loses
much of its reflectance. It is a poor reflector of ultraviolet.
Silver fulminate (Ag2C2N2O2), 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. While silver itself is not con-
sidered to be toxic, most of its salts are poisonous due to
the anions present. 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.
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.
In 1939, the price of silver was fixed by the U.S. Treasury
at 71i/troy oz., and at 90.5/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 com-
posite type coins. This is 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 clad
half dollars, with an overall silver content of 40 % contain
an outer layer of 80% Ag and 20 % Cu bonded to an inner
core of about 20% Ag and 80% Cu. The U.S. Treasury has
minted, as of 1970, about 1 billion of these half dollars
and placed them into circulation. The compositioti of the
onecent and five-cent pieces as well as the silver dollar
remain unchanged. One-cent coins are 95% Cu and 5% Zn.
Fivecent coins are 75 % Cu and 25 % Ni. Standard silver
dollars are 90% Ag and 10% Cu. Earlier subsidiary c,oins of
90% Ag and 10% Cu officially are to circulate Alongside the
clad 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 coiris made of
other metals. On June 24, 1968, the U.S. Government
ceased to redeem UtS. Silver Certificates with silver. Since
that time, the price of silver has fluctuated widely, reaching
levels as high as $2/troy ounce or more.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
