Friday, July 31, 2009

Occurrence and extraction

History

The symbol for the Moon has been used since ancient times to represent silver.

The word "silver" appears in Anglo-Saxon in various spellings such as seolfor and siolfor. A similar form is seen throughout the Teutonic languages (compare Old High German silabar and silbir). The chemical symbol Ag is from the Latin for "silver", argentum (compare Greek άργυρος, árgyros), from the Indo-European root *arg- meaning "white" or "shining". Silver has been known since ancient times. It is mentioned in the book of Genesis, and slag heaps found in Asia Minor and on the islands of the Aegean Sea indicate that silver was being separated from lead as early as the 4th millennium BC using surface mining.[6]

In the Gospels, Jesus' disciple Judas Iscariot is infamous for having taken a bribe of thirty coins of silver from religious leaders in Jerusalem to turn Jesus Christ over to the Romans.

Set aside certain circumstances,[clarification needed] Islam permits Muslim men to wear silver jewelry. Muhammad himself wore a silver signet ring.

[edit] Occurrence and extraction

Main article: Silver mining
Silver ore with Lincoln cent for scale
Time trend of silver production

Silver is found in native form, alloyed with gold or combined with sulfur, arsenic, antimony or chlorine in ores such as argentite (Ag2S), horn silver (AgCl), and pyrargyrite (Ag3SbS3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru, Mexico, China, Australia, Chile, Poland and Serbia.[6] Peru and Mexico have been mining silver since 1546 and are still major world producers. Top silver-producing mines are Proaño / Fresnillo (Mexico), Cannington (Queensland, Australia), Dukat (Russia), Uchucchacua (Peru) and Greens Creek mine (Alaska).[30]

The metal can also be produced during the electrolytic refining of copper and by the application of the Parkes process on lead metal obtained from lead ores that contain small amounts of silver. Commercial-grade fine silver is at least 99.9% pure silver, and purities greater than 99.999% are available. In 2007, Peru was the world's top producer of silver, closely followed by Mexico, according to the British Geological Survey.

[edit] Price

Main articles: Silver as an investment and Silver standard
Silver output in 2005

As of October 2008 silver is about 1/75th the price of gold by mass.[31] Silver once traded at 1/6th to 1/12th the price of gold, prior to the Age of Discovery and the discovery of great silver deposits in the Americas, including Peru, Mexico and the United States, such as the vast Comstock Lode in Virginia City, Nevada, USA. This then resulted in the debate over cheap Free Silver to benefit the agricultural sector, which was among the most prolonged and difficult in that country's history[clarification needed] and dominated public discourse during the latter decades of the nineteenth century.

Over the last 100 years the price of silver and the gold/silver price ratio have fluctuated greatly due to competing industrial and store-of-value demands. In 1980 the silver price rose to an all-time high of US$49.45 per troy ounce. By December 2001 the price had dropped to US$4.15 per ounce, and in May 2006 it had risen back as high as US$15.21 per ounce. In March 2008 silver reached US$21.34 per ounce.[32]

The price of silver is important in Judaic Law. The lowest fiscal amount that a Jewish court, or Beth Din, can convene to adjudicate a case over is a shova pruta (value of a Babylonian pruta coin). This is fixed at 1/8 of a gram of pure, unrefined silver, at market price.

[edit] Precautions

Silver plays no known natural biological role in humans, and possible health effects of silver are a subject of dispute. Silver itself is not toxic but most silver salts are, and some may be carcinogenic. Silver and compounds containing silver (like colloidal silver) can be absorbed into the circulatory system and become deposited in various body tissues leading to a condition called argyria which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Although this condition does not otherwise harm a person's health, it is disfiguring and usually permanent. Argyria is rare, and mild forms are sometimes mistaken for cyanosis.[6]

[edit] See also

[edit] References

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  6. ^ a b c d e f g C. R. Hammond (2000). The Elements, in Handbook of Chemistry and Physics 81th edition. CRC press. ISBN 0849304814. 
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  10. ^ Rudolf Meyer, Josef Köhler, Axel Homburg (2007). Explosives. Wiley-VCH. p. 284. ISBN 3527316566. http://books.google.com/books?id=ATiYCfo1VcEC&pg=PA284&dq=%22silver++fulminate%22&lr=&num=100&as_brr=3. 
  11. ^ a b "Gold Jewellery Alloys > Utilise Gold. Scientific, industrial and medical applications, products ,suppliers from the World Gold Council". Utilisegold.com. 2000-01-20. http://www.utilisegold.com/jewellery_technology/colours/colour_alloys/. Retrieved on 2009-04-05. 
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  18. ^ "Antibacterial effects of silver". http://www.saltlakemetals.com/Silver_Antibacterial.htm. 
  19. ^ Chang TW, Weinstein L (December 1975). "Prevention of herpes keratoconjunctivitis in rabbits by silver sulfadiazine". Antimicrob. Agents Chemother. 8 (6): 677–8. PMID 1211919. PMC: 429446. http://aac.asm.org/cgi/pmidlookup?view=long&pmid=1211919. 
  20. ^ Atiyeh BS, Costagliola M, Hayek SN, Dibo SA (March 2007). "Effect of silver on burn wound infection control and healing: review of the literature". Burns : journal of the International Society for Burn Injuries 33 (2): 139–48. doi:10.1016/j.burns.2006.06.010. PMID 17137719. 
  21. ^ a b Lo SF, Hayter M, Chang CJ, Hu WY, Lee LL (August 2008). "A systematic review of silver-releasing dressings in the management of infected chronic wounds". Journal of clinical nursing 17 (15): 1973–85. doi:10.1111/j.1365-2702.2007.02264.x. PMID 18705778. 
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  27. ^ Wadhera A, Fung M (2005). "Systemic argyria associated with ingestion of colloidal silver". Dermatology online journal 11 (1): 12. PMID 15748553. http://dermatology.cdlib.org/111/case_reports/argyria/wadhera.html. 
  28. ^ Slawson RM, Van Dyke MI, Lee H, Trevors JT (January 1992). "Germanium and silver resistance, accumulation, and toxicity in microorganisms". Plasmid 27 (1): 72–9. doi:10.1016/0147-619X(92)90008-X. PMID 1741462. 
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  32. ^ "Silver Cash daily plot". Barchart.com. http://charts3.barchart.com/chart.asp?sym=SIY0&data=A&jav=adv&vol=Y&evnt=adv&grid=Y&code=BSTK&org=stk&fix=.

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