Silver
Silver is a metallic chemical element with the chemical symbol Ag (Latin: argentum) and atomic number 47. It is a precious metal, and it is used to make ornaments, jewelry, high-value tableware, utensils (hence the term silverware), and currency coins. Today, silver metal is also used in electrical contacts and conductors, in mirrors and in catalysis of chemical reactions. Its compounds are used in photographic film and silver compounds are used as disinfectants and microbiocides. It has been known since earliest human history. Silver objects dated as old as 3400 B.C. have been found in Egypt.
Production
Silver can occur as a free metal, but much less often than gold or copper. Most of the rich ores have been mined by now, today its content in mined ores ranges from about a few thousandths of an ounce per ton of ore to 100 ounces per ton. Silver is most commonly produced as a by-product of mining for other metals.
The largest producers of silver in the world are Mexico, Peru, the United States, Canada, Poland, Chile, and Australia. In the United States, silver is produced at about 76 mines in 16 states. The largest state producers are Nevada, Idaho, and Arizona. These three states account for about two-thirds of all the silver mined in the United States.[1]
Properties
Silver is a soft, white metal with a shiny surface. It is very ductile and malleable. It conducts heat and electricity better than any other metal. It also reflects light very well.[2]
Silver is a very inactive metal. It does not react with oxygen in the air under normal circumstances, but it reacts slowly with sulfur compounds in the air. The product of this reaction is silver sulfide, a black tarnish that develops over time on silverware and other silver-plated objects. Silver does not react readily with water, acids, or many other compounds. It does not burn except as silver powder.[1]
To identify silver, one can start excluding similar metals by using a magnet, gold and silver are not magnetic. [3] Another method is to either drop a coin on the floor or to strike it with a pencil. The resulting sound should be of a higher frequency similar to a bell, and will resonate for longer than is perhaps expected. If a dull sound is heard then the coin is likely only to be a base metal coated in silver plating; this requires experience and offers no guarantee. Testing the conductivity (e.g. by placing a part of an item into ice and observe it quickly going cold) is also a hint, but does not reveal plated items. More reliable methods require a chemical reaction, that creates the black sulfide tarnish (by lighting a match against the silver object; or using a special brand of mustard with sulfur). Using commercial testing kits or nitric acid is more reliable, but destructive in nature, use with care.[4]
Applications
One way silver is used is in alloys with gold. Gold is highly desired for coins and jewelry. But it is much too soft to use in its pure form. Adding silver to gold, however, makes an alloy that is much stronger and longer lasting. Most "gold" objects today are actually alloys, often alloys of silver and gold. Silver compounds are used to make photographic film.
Another important use of silver is in electrical and electronic equipment. It is the most desirable metal due to its high conductivity, but in most cases are used metals like copper or aluminum because they are less expensive. Silver is used where cost is secondary, like in aircraft, satellites and spacecraft. It is also used in specialized batteries, including silver-zinc and silver-cadmium batteries. It can be used for mirrors and reflectors.
Silver is also used in dental amalgams, which are non-toxic and do not break down or react with other materials very readily.[1] Silver has antibacterial and antifungal effects without harm to higher animals. It has numerous medicinal applications, especially in wounds and burns treatment. It was historically used to prevent the spoiling of water (Pioneers of the American West would place silver coins in their casks) and other liquids. Today, water tanks on ships and airplanes are often "silvered". [5]
References
- ↑ 1.0 1.1 1.2 Chemistry Explained. Silver (as chemical) and Silver (as element). Referenced 2010-01-10.
- ↑ Webelements. "Silver", referenced 2010-01-10.
- ↑ "Is gold magnetic?", The Van, University of Illinois Physics Department, referenced 2010-01-17.
- ↑ See "How to test for pure silver" by Tim Harry; "Is it Silver?" by Sheryl Gross Shatz; or "How to Identify Pure Silver by Roberrific. Referenced 2010-01-17.
- ↑ Salt Lake Metals. "The Antibacterial Effects of Silver and it's compounds", referenced 2010-01-10.
External links
- Silver on Wikipedia
- Silver from the Mineralogy Database
- Silver Mineral Data
- Historical Silver Data and Charts from 1833 to the present