Encyclopedia:
Silver,
Mercury (element),
Talk:Silver,
Silver Surfer,
Silver Star,
Silver age,
Silver Jubilee,
Colloidal silver,
Tactical frivolity,
Forgotten Silver
Silver (
IPA: ) is a
chemical element with the symbol
Ag ). A soft white lustrous
transition metal, it has the highest electrical and thermal conductivity of any metal and occurs in
minerals and in free form. This metal is used in
coins,
jewelry,
tableware,
photography, and in mirrors.
Notable characteristics
left|thumb|A nugget of silverSilver is a very ductile and malleable (slightly harder than
gold) univalent
coinage metal with a brilliant white metallic luster that can take a high degree of
polish. It has the highest
electrical conductivity of all metals, even higher than
copper, but its greater cost and tarnishability has prevented it from being widely used in place of copper for electrical purposes.
Pure silver also has the highest
thermal conductivity, whitest color, the highest optical
reflectivity (although it is a poor reflector of
ultraviolet light), and the lowest contact resistance of any metal. Silver halides are photosensitive and are remarkable for the effect of light upon them. This metal is stable in pure air and water, but does tarnish when it is exposed to
ozone,
hydrogen sulfide, or air containing
sulfur. The most common
oxidation state of silver is +1 (for example,
silver nitrate; AgNO
3); a few +2 (for example,
silver(II) fluoride; AgF
2) and +3 compounds (for example,
silver(III) persulfate; Ag
2(SO
5)
3) are also known.
Applications
The principal use of silver is as a
precious metal. Its salts, especially
silver nitrate and silver
halides, are also widely used in photography (which is the largest single end use of silver).
Some other uses for silver are as follows:
*Electrical and electronic products, which need silver's superior conductivity, even when tarnished. For example, printed circuits are made using silver paints, and computer keyboards use silver electrical contacts. Silver (silver cadmium oxide) is also used in high voltage contacts because it can minimize any
arcing.
*
Mirrors which need superior reflectivity for visible light are made with silver as the reflecting material in a process called
silvering. Common mirrors are backed with
aluminium.
*Many high end
musical instruments are made with silver, which benefit from a higher tone quality.
*Silver has been coined to produce money since
700 BC by the
Lydians, in the form of
electrum. Later, silver was refined and coined in its pure form. The words for "silver" and "money" are the same in at least 14 languages.
*The metal is chosen for its beauty in the manufacture of jewelry and silverware, which are traditionally made from the silver alloy known as
Sterling silver, which is 92.5% silver and usually alloyed with copper. The name of United Kingdom monetary unit 'Pound' originally had the value of one troy pound of sterling silver.
*Silver is also used in medals, denoting second place.
*The malleability, non-toxicity and beauty of silver make it useful in dental alloys for fittings and fillings.
*Silver's catalytic properties make it ideal for use as a
catalyst in oxidation reactions; for example, the production of
formaldehyde from
methanol and air by means of silver screens or
crystallites containing a minimum 99.95
weight-percent silver. Silver (upon some suitable support) is probably the only catalyst available today to convert
ethylene to
ethylene oxide (later hydrolyzed to
ethylene glycol, used for making
polyesters)—a very important industrial reaction.
*
Oxygen dissolves in silver relatively easily compared to other gases present in air. Attempts have been made to construct silver
membranes of only a few
monolayers thickness. Such a membrane could be used to filter pure oxygen from air.
*Used to make
solder and brazing alloys,
electrical contacts, and high capacity silver-
zinc and silver-
cadmium batteries.
*
Silver sulfide, also known as
Silver Whiskers, is formed when silver
electrical contacts are used in an atmosphere rich in
hydrogen sulfide.
*
Silver fulminate is a powerful
explosive.
*
Silver chloride can be made transparent and is used as a
cement for glass.
*
Silver chloride is also a widely used electrode for
pH testing and
potentiometric measurement.
*
Silver iodide has been used in attempts to seed
clouds to produce rain.
*
Silver oxide is used as a positive electrode (
cathode) in watch batteries.
*
Colloidal silver is a possible antibacterial / antibiotic treatment espoused in alternative medicine, also notorious for causing
argyria.
*
Silver nitrate (liquid) was a standard of care but was largely replaced by
silver sulfadiazine cream (SSD Cream) which was generally the "standard of care" for the antibacterial/antibiotic treatment of serious burns until the late 1990's. Now, other options such as silver coated dressings (activated silver dressings) are used in addition to SSD cream, and may present advantages such as pain reduction and capacity for treatment at home.
*Silver is often used in modern
horror fiction as a weapon against certain
supernatural entities, especially
werewolves, who are sometimes described as being burned by silver.
History
left|thumb|75px|Alchemical symbol for silverSilver (from
Anglo-Saxon seolfor, compare
Old High German silabar; Ag is from the Latin
argentum) 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.
Silver has been used for thousands of years for
ornaments and
utensils, for
trade, and as the basis for many
monetary systems. Its value as a
precious metal was long considered second only to
gold. In
Ancient Egypt and
Medieval Europe, it was often more valuable than gold.
Judas Iscariot is infamous for having, according to the
New Testament, taken a bribe of thirty pieces of silver from religious leaders in
Jerusalem to turn
Jesus Christ over to the Romans.
Associated with the
moon, as well as with the sea and various lunar
goddesses, the metal was referred to by alchemists by the name
luna. One of the
alchemical symbols for silver is a
crescent moon with the open part on the left (see picture, left).
The metal
mercury was thought of as a kind of silver, though the two elements are chemically unrelated; its Latin and
English names,
hydrargyrum ("watery silver") and
quicksilver, respectively, reflect this history.
In
heraldry, the
argent, in addition to being shown as silver (this has been shown at times with real silver in official representations), can also be shown as white. Occasionally, the word "silver" is used rather than argent; sometimes this is done across-the-board, sometimes to avoid repetition of the word "argent" in blazon.
Europeans found a huge amount of silver in the
New World in
Zacatecas and
Potosí, which triggered a period of inflation in Europe. The conquistador
Pizarro was said to have resorted to having his horses shod with silver horseshoes due to the metal's abundance, in contrast to the relative lack of iron in
Peru. Silver, which was extremely valuable in
China, became a global commodity, contributing to the rise of the
Spanish Empire. The rise and fall of its value affected the world market.
The
Rio de la Plata was named after silver (in
Spanish,
plata), and in turn lent the meaning of its name to
Argentina.
Silver mining was a driving force in the settlement of western North America, with major booms for silver and associated minerals (primarily lead) in the galena ore silver is most commonly found in. Notable
"silver rushes" were in
Colorado,
Nevada,
Cobalt, Ontario ,
California and the
Kootenay region of British Columbia, notably in the
Boundary and
"Silvery Slocan". The largest silver ore deposits in the United States were discovered at the
Comstock Lode in Virginia City, Nevada, in 1859.
Occurrence and extraction
thumb|left|Silver ore (Lincoln cent is shown for scale)Main|Silver
Silver is found in native form, combined with
sulfur,
arsenic,
antimony, or
chlorine and in various ores such as
argentite (Ag
2S) and
horn silver (Ag
Cl).
The principal sources of silver are
copper, copper-
nickel,
gold,
lead and lead-
zinc ores obtained from
Canada,
Cobalt, Ontario,
Mexico (historically
Batopilas),
Peru,
Australia and the
United States.
This metal is also produced during the
electrolytic refining of copper. Commercial grade fine silver is at least 99.9% pure silver and purities greater than 99.999% are available.
Mexico is the world's largest silver producer. According to the Secretary of Economics of Mexico, it produced 80,120,000
troy ounces (2492
metric tons) in 2000, about 15% of the annual production of the world.
Price
thumb|right|143px|[Johnson Matthey silver bullion bar]
main|Silver as an investment|Silver
Silver is currently about 1/50th the price of gold by mass, and approximately 70 times more valuable than
copper. Silver did once trade 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, most notably the vast
Comstock Lode in
Virginia City,
Nevada, USA. This then resulted in the debate over cheap
Free Silver to benefit the agricultural sector was among the most prolongued and difficult in that country's history 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 has 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 fallen to US$4.15 per ounce, and in May 2006 it had risen back as high as US$15.21 per ounce.
As of 2006, current silver prices (and most other metal prices) have been rather volatile, for example quickly dropping from the May high of US$15.21 per ounce to a June low of US$9.60 per ounce before rising back above US$12 per ounce by August.
[cite web | url=http://charts3.barchart.com/chart.asp?sym=SIY0&data=A&jav=adv&vol=Y&evnt=adv&grid=Y&code=BSTK&org=stk&fix=|publisher=Barchart.com | title=Silver Cash daily ]Isotopes
Naturally occurring silver is composed of the two stable
isotopes
107Ag and
109Ag with
107Ag being the more abundant (51.839%
natural abundance). Twenty-eight
radioisotopes have been characterised with the most stable being
105Ag with a
half-life of 41.29 days,
111Ag with a half-life of 7.45 days, and
112Ag with a half-life of 3.13 hours.
All of the remaining
radioactive isotopes have half-lifes that are less than an hour and the majority of these have half lifes that are less than 3 minutes. This element also has numerous
meta states with the most stable being
108mAg (
t* 418 years),
110mAg (
t* 249.79 days) and
106mAg (
t* 8.28 days).
Isotopes of silver range in
atomic weight from 93.943
u (
94Ag) to 123.929 u (
124Ag). The primary
decay mode before the most abundant stable isotope,
107Ag, is
electron capture and the primary mode after is
beta decay. The primary
decay products before
107Ag are
palladium (element 46) isotopes and the primary products after are
cadmium (element 48) isotopes.
The palladium
isotope 107Pd decays by beta emission to
107Ag with a half-life of 6.5 million years.
Iron meteorites are the only objects with a high enough
Pd/Ag ratio to yield measurable variations in
107Ag abundance.
Radiogenic 107Ag was first discovered in the
Santa Clara meteorite in
1978.
The discoverers suggest that the coalescence and differentiation of iron-cored small
planets may have occurred 10 million years after a
nucleosynthetic event.
107Pd versus Ag correlations observed in bodies, which have clearly been melted since the
accretion of the
solar system, must reflect the presence of live short-lived nuclides in the early solar system.
In medicine
Hippocrates, the father of modern medicine, wrote that silver had beneficial healing and anti-disease properties, and the Phoenicians used to store water, wine, and vinegar in silver bottles to prevent spoiling. In the early 1900s people would put
silver dollars in milk bottles to prolong the milk's freshness. Silver compounds were used successfully to prevent infection in
World War I before the advent of
antibiotics.
The widespread use of silver went out of fashion with the development of modern antibiotics. However, recently there has been renewed interest in silver as a broad spectrum antimicrobial. In particular, it is being used with alginate, a naturally occurring
biopolymer derived from seaweed, in a range of
silver alginate products designed to prevent infections as part of
wound management procedures, particularly applicable to
burn victims. In addition, Samsung has introduced washing machines with a final rinse containing silver ions to provide several days of antibacterial protection in the clothes.
[cite web | title=Samsung laundry featuring SilverCare Technology | publisher=Samsung | url=http://www.samsung.com/PressCenter/PressRelease/PressRelease.asp?seq=20060213_0000233684 | accessdate=2006-05-20 ] Additionally, Kohler has introduced a line of toilets that have silver ions embedded in the porcelain to kill germs.
Health 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 harm a person's health, it is disfiguring and usually permanent. Argyria is rare and mild forms are sometimes mistaken for
cyanosis.
Silver-ions and silver compounds show a toxic effect on some bacteria, viruses, algae and fungi typical for heavy metals like
lead or
mercury, but without the high toxicity to humans that is normally associated with them. Its germicidal effects kills many microbial organisms
in vitro (i.e. in a
test tube or a
petri dish). The exact process by which this is done is still not well understood, although several different theories exist. One of these is a process generally known for heavy metals called the
oligodynamic effect, which goes a long way explaining the effect on microbial lifeforms but does not explain certain antiviral functions.
Alternative medicine
Today, various kinds of silver compounds, or devices to make solutions or
colloids containing silver, are sold as remedies for a wide variety of diseases. Although mostly harmless, some people using these home-made solutions use far too much and develop
argyria over a period of months or years, and several have been documented in the last few years in the medical literature, including one possible case of coma associated with a high intake of silver (see medical references). It is strongly advised to notify a doctor when taking silver as a form of self-medication.
In food
In India, foods can be found decorated with a thin layer of silver, known as
Varak. Silver as a food additive is given the
E number E174 and classed as a
food coloring. It is used solely for external decoration, such as on
chocolate confectionery, in the covering of
dragées and the decoration of sugar-coated flour confectionery. In
Australia, it is banned as a food additive.
Superstition
Because of the mysticism surrounding silver's
lunar associations, as well as the aesthetic qualities of the white, reflective metal that cause it to be associated with purity, silver in European
Folklore has long been traditionally believed to be an antidote to various maladies and fictional
monsters. Notably, silver was believed to be a repellant against
vampires (this primarily originates from its holy connotations; also, mirrors were originally polished silver, and as such, vampires allegedly cannot be seen in them because they are wicked) and it was believed that a
werewolf, in his bestial form, could only be killed by a weapon or bullet made of silver, and was equally effective against vampires, as described in Eastern European folklore. This has given rise to the term "
silver bullet," which is used to describe things that very effectively deal with one specific problem.
Notes
References
*
http://periodic.lanl.gov/elements/47.html Los Alamos National Laboratory – SilverSee also
*
Precious metal*
Silver as an investment*
Silver coin*
Silver standard*
Silver compounds*
Colloidal silverExternal links
Spoken
*
http://www.webelements.com/webelements/elements/text/Ag/index.html WebElements.com – Silver*
http://minerals.usgs.gov/minerals/pubs/commodity/silver/ Silver Statistics and Information,
USGS publications on the worldwide production of silver
*
http://www.silverinstitute.org The Silver Institute A silver industry website
*
http://www.theodoregray.com/PeriodicTable/Elements/047/index.html A collection of silver items Samples of silver
Publications on health effects
*
http://dermatology.cdlib.org/111/case_reports/argyria/wadhera.html Systemic argyria associated with ingestion of colloidal silver*
http://www.neurology.org/cgi/content/full/62/8/1408 Myoclonic status epilepticus following repeated oral ingestion of colloidal silver*
http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=185946 Specific Inactivation of Herpes Simplex Virus by Silver Nitrate at Low Concentrations and Biological Activities of the Inactivated Virus*
http://www.pubmedcentral.gov/pagerender.fcgi?artid=429446&pageindex=1 Prevention of Herpes Keratoconjunctivitis in Rabbits By Silver SulfadiazineCategory:Chemical elementsCategory:Transition metalsCategory:Precious metals ar:فضةast:Platazh-min-nan:Ag (goân-sò͘)bs:Srebrobg:Среброca:Platacs:Stříbroco:Argentucy:Arian (elfen)da:Sølvde:Silberet:Hõbees:Plataeo:Arĝentofa:نقرهfr:Argent (métal)ga:Airgead (dúil)gd:Airgead (meatailt)ko:은hy:Արծաթhr:Srebroio:Arjentoid:Perakis:Silfurit:Argentohe:כסף (יסוד)ka:ვერცხლიku:Zîvla:Argentumlv:Sudrabslb:Sëlwerlt:Sidabrasli:Zèlverjbo:rijnohu:Ezüstmi:Kawatams:Logam peraknl:Zilverja:銀no:Sølvnn:Sølvoc:Argentug:كۈمۈشnds:Sülverpl:Srebropt:Prataro:Argintru:Сереброscn:Argentusimple:Silversk:Striebrosl:Srebrosr:Среброsh:Srebrofi:Hopeasv:Silverta:வெள்ளிtt:Kömeşth:เงิน (ธาตุ)vi:Bạctg:Нуқраtr:Gümüşuk:Сріблоuz:Kumushzh-yue:銀zh:銀
