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

It was estimated, that by 2001 a total of 1,260,000 tonnes of silver have been mined throughout all human history, 69 percent in the 20th century.

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.

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.

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.

To identify silver, one can start excluding similar metals by using a magnet, gold and silver are not magnetic. 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.

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 also 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. 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".

Important uses and their introduction:

• Silver and silver salts have been central to the development of photography since its origins in the 1820s.
• Silver-mercury dental amalgams have been used for tooth restorations since the late 1830s.
• Mirrors of polished silver were used by the Egyptians in the third millennium B.C., and “silvering” of mirrors with lead, tin, or mercury was practiced in Europe before and during the Renaissance. The large-scale production of silvered glass mirrors through the chemical reduction of silver nitrate dates from Justus von Liebig’s 1835 invention of the process.
• A patent for a process for the electroplating of silver was granted in 1840; it was the first patent for the electroplating of any metal.
• Although Alessandro Volta had used silver and zinc as the electrodes of his “electric pile,” or battery, at the beginning of the 19th century, it was not until military requirements in the 1940s created a demand for high-energy-density batteries that the first two types of practical silver batteries were developed.
• Silver sleeve bearings were developed in the 1940s for use in high-performance military aircraft engines.
• Silver catalysts for the large-scale production of formaldehyde and the oxidation of ethylene are developments of the second half of the 20th century.
• Although silver was known to be an excellent conductor of electricity in the 19th century, its widespread use in switch and relay contacts and in conductors arose gradually during the 20th century.

Gold and silver in history

The relation in value of gold to silver in Asia generally in Persian times was 13 to 1 as evidenced by Herodotus (other sources speculate on 13⅓ to 1, at the time were used silver bars weighing 169 grains, ten of which passed for one gold bar of 130 grains).

By the time Charlemagne was crowned Imperator Augustus in 800, there was a chronic shortage of silver in Western Europe.

In England, the Exchequer of Henry I (reigned 1100 – 1135) usually accepted silver in discharge of debts in gold at a ratio of nine to one. In the thirteenth century a ratio of ten to one had become normal. In 1255 the ratio was a little less than ten to one.

In the second quarter of the fourteenth century has the value of silver against gold risen. In Florence had the ratio been fixed at 13.62, while in France was the ratio at 12.6. The result on Florence was immediate, and silver disappeared from circulation. In 1345, says the historian Villani, there was a great scarcity. A recoinage was attempted several times, but silver had so far disappeared in the Italian peninsula, or gold had so far increased, that the commercial ratio during the fifteenth century remained persistently low — 9.25 both in Milan and Florence. (See also the Great Bullion Famine.)

Europe was impacted by the inflow of precious metals from the New World, but it was not a dramatic price revolution. The money stock (gold and silver) increased depending on various estimates by 50 to 500% from the year 1500 over a period of 150 years (an average growth rate of the money supply somewhere between 0.3 and 3.3 percent per annum). Where many complained about rising prices, some have recognized (often ascribed to J. Bodin in 1568, but first recognized by Azpilcueta Navarro from the School of Salamanca in 1556), that the goods have not risen in value, but silver has fallen; from 1500 to 1700 it was estimated to be 1/20 of its former value.

The prices of gold and silver changed from 1701 to 1710 from about 1:15,27, to 1:14,93 in 1740-50. In Germany has the Reichstag in Regensburg (1737-38) set the ratio to 1:15,1.

Links

• Silver on Wikipedia
• Silver from the Mineralogy Database
• Silver Mineral Data
• Historical Silver Data and Charts from 1833 to the present