Silver (Ag)has been known since prehistoric times. The ancient Hebrews knew it by a name meaning pale. The Greeks called it a name meaning shining. The name silver comes from the Old English word sealfor. The chemical symbol Ag comes from its Latin name, argentum.
Properties
Silver is a Third Transition Metal. Its atomic weight is 107.870, and its atomic number is 47. It melts at 961.95° C and boils at 2,212° C.
Silver is not changed by moisture, dryness, alkalis, or vegetable acids, but sulfur, or air that contains sulfur, will cause silver to turn black. Silver is harder than gold, but softer than copper. It can be hammered out into sheets so thin that it would take 100,000 of them to make a stack 1 inch high. Silver can also be drawn out into wires finer than human hair. It is the best conductor of heat and electricity among the metals, but its high cost usually prohibits its use in electrical conductors.
Sources
Pure silver is mined chiefly in Mexico and Peru; the provinces of British Columbia and Ontario in Canada; the state of New South Wales in Australia; Russia; and Arizona, Idaho, and Montana in the United States. Canada, Mexico, Peru, and Russia produce over half the world's supply of silver.
The most important of
the silver ores are called sulfides, or ores
containing sulfur. The richest ore mineral of silver is
called argentite, which is made up of two parts
of silver to one part of sulfur. The other sulfides are
more complex and are found chiefly in Mexico, Peru,
Bolivia, Chile, and Idaho. Light ruby silver
contains arsenic, sulphur, and silver. Dark ruby
silver contains antimony, sulphur, and silver. Brittle
silver is made up of the same combining elements as
dark ruby silver. Other important silver ores include horn
silver, which contains chlorine and silver, and hessite,
a compound of silver and tellurium. Galena, the chief ore
of lead, often carries silver. In most of the
silver-production countries of Europe, silver is found in
lead ores. There is a valuable lead mine in the Coeur
d'Alene district of Idaho, where silver is mined in large
quantities. Silver occurs with copper in the Butte district of Montana. A famous
silver-copper mine is also located in Mansfeld, Germany.
Silver can also be found alloyed with other metals,
including gold, mercury, and copper.
Uses
Pure silver is too soft to stand up under constant wear, so it is usually mixed with copper to form an alloy before it is made into commercial articles. This alloy is used to make coins, jewelry, and tableware. Sterling silver contains at least 92½ per cent silver. Silver plate is made by coating base metals with pure silver or silver alloy by electrolysis.
In the laboratory, silver has many uses. One of its most important chemical compounds is called silver nitrate, which is made by dissolving silver in nitric acid. Silver nitrate is widely used in photography, silver plating, and indelible ink. Silver chloride is made by adding hydrochloric acid to a solution of silver. It is then combined with silver bromide for use in various chemical processes of photography. Silver fulminate -- which contains nitrogen, carbon, hydrogen, and oxygen in addition to silver -- is a violent explosive.
The Robinson Library
Science.--Chemistry.--Inorganic Chemistry.--Chemical Elements.
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