Feb 2013 Metal of the Month: Silver
Silver is a metallic chemical element with the
chemical symbol Ag. A soft, white, lustrous transition metal, it has the
highest electrical conductivity of any element and the highest thermal conductivity
of any metal. The metal occurs
naturally in its pure, free form as an alloy with gold and other metals, and in
minerals such as argentite and chlorargyrite. Most silver is produced as a
byproduct of copper, gold, lead, and zinc refining. Many well-known uses of
silver involve its precious metal properties, including currency, decorative
items, and mirrors. The contrast between its bright white color and other media
makes it very useful to the visual arts. It has also long been used to confer
high monetary value as objects such as silver coins and investment bars or make
objects symbolic of high social or political rank. Today, silver metal is also
used in electrical contacts and conductors and in catalysts of chemical
reactions. Its compounds are used in photographic film, and diluted silver
nitrate solutions. Other silver compounds are used as disinfectants. Among
metals, pure silver has a very high optical reflectivity. Silver is stable in pure air and water, but
tarnishes 
when it is exposed to air or water containing ozone or hydrogen
sulfide. Recorded use of silver to prevent infection dates to ancient Greece
and Rome. It was re-discovered in the Middle Ages, when it was used for several
purposes such as to disinfect water and food during storage and also for the
treatment of burns and wounds as wound dressing. In the 19th century, sailors
on long ocean voyages would put silver coins in barrels of water and wine to
keep the liquid potable. Pioneers in America used the same idea as they made
their journey from coast to coast. Silver solutions were approved in the 1920s
by the US Food and Drug Administration for use as antibacterial agents.
