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Silver
has long been valued as 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 dilute silver nitrate solutions and other silver compounds are
used as disinfectants
and microbiocides. While many medical antimicrobial
uses of silver have been supplanted by antibiotics,
further research into clinical potential continues.
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Characteristics
Silver
is a very ductile
and malleable
(slightly harder than gold)
monovalent 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 tendency to tarnish have
prevented it from being widely used in place of copper for electrical purposes.
Despite this, 13,540 tons were used in the electromagnets
used for enriching uranium during World War
II (mainly because of the wartime shortage of copper).[1][2]
Another notable exception is in high-end audio cables.[3]
Among
metals, pure silver has the highest thermal conductivity[4]
(the non-metal diamond
and superfluid
helium II
are higher) and one of the highest optical reflectivity.[5]
(Aluminium
slightly outdoes silver in parts of the visible spectrum, and silver is a poor
reflector of ultraviolet light). Silver also has the lowest contact resistance of any metal. Silver
halides are photosensitive and are remarkable for their ability to
record a latent image that can later be developed chemically. Silver is stable in
pure air and water, but tarnishes when it is exposed to air or water containing ozone or hydrogen
sulfide to form a black layer of silver
sulfide which can be cleaned off with dilute hydrochloric
acid.[6]
The most common oxidation state of silver is +1 (for example, silver
nitrate: AgNO3); in addition, +2 compounds (for example, silver(II) fluoride: AgF2) and the
less common +3 compounds (for example, potassium tetrafluoroargentate: K[AgF4]
) are known.
Creation
Silver
is created via the long S-process in low-medium mass stars (.6 -> 10 solar
masses). This takes thousands of years to do.
Applications
Many
well known uses of silver involve its precious
metal properties, including currency, decorative items and mirrors. The
contrast between the appearance of its bright white color in contrast with
other media makes it very useful to the visual arts. It has also long been used
to confer high monetary value as objects (such as silver coins and investment
bars) or make objects symbolic of high social or political rank.
Currency
Main articles: Silver coin and Silver
standard
Silver,
in the form of electrum
(a gold-silver alloy), was coined to produce money in around 700 BC by the
Lydians. Later,
silver was refined and coined in its pure form. Many nations used silver as the
basic unit of monetary value. In the modern world, silver bullion has the ISO currency code
XAG. The name of the United Kingdom monetary unit "pound"
(£) reflects the fact that it originally represented the value of one troy pound
of sterling silver. In the 1800s, many nations, such as the United
States and Great Britain, switched from silver to a gold
standard of monetary value, then in the 20th century to fiat
currency.
Jewelry and silverware
Main articles: jewellery and silversmith
Jewellery
and silverware are traditionally made from sterling
silver (standard silver), an alloy of 92.5% silver with 7.5% copper. In the
US, only an alloy consisting of at least 92.5% fine silver can be marketed as
"silver" (thus frequently stamped 925). Sterling silver is harder
than pure silver, and has a lower melting point (893 °C) than either pure
silver or pure copper.[6]
Britannia
silver is an alternative hallmark-quality standard containing 95.8% silver, often
used to make silver tableware and wrought plate. With the addition of germanium,
the patented modified alloy Argentium Sterling Silver is formed, with
improved properties including resistance to firescale.
Sterling
silver jewelry is often plated with a thin coat of .999 fine silver to
give the item a shiny finish. This process is called "flashing".
Silver jewelry can also be plated with rhodium (for a
bright, shiny look) or gold.
Dentistry
Silver
can be alloyed with mercury, tin and other metals at room temperature to make amalgams that are widely used for dental
fillings. To make dental amalgam, a mixture of powdered silver and
other metals is mixed with mercury to make a stiff paste that can be adapted to
the shape of a cavity. The dental amalgam achieves initial hardness within
minutes but sets hard in a few hours.
Photography and electronics
Photography
used 30.98% of the silver consumed in 1998 in the form of silver nitrate and
silver halides.
In 2001, 23.47% was used for photography, while 20.03% was used in jewelry,
38.51% for industrial uses, and only 3.5% for coins and medals. The use of
silver in photography has rapidly declined, due to the lower demand for
consumer color film from the advent of digital technology, since in 2007 of the
894.5 million ounces of silver in supply, just 128.3 million ounces
(14.3%) were consumed by the photographic sector, and the total amount of
silver consumed in 2007 by the photographic sector compared to 1998 is just
50%.[17]
Some
electrical and electronic products use silver for its superior conductivity,
even when tarnished. For example, printed circuits can be made using silver
paints,[6]
and computer keyboards use silver electrical contacts. Some high-end audio
hardware (DACs, preamplifiers,
etc.) are fully silver-wired, which is believed to cause the least loss of
quality in the signal. Silver cadmium oxide is used in high voltage contacts
because it can withstand arcing.
Mirrors and optics
Mirrors which need
superior reflectivity for visible light are made with silver as the reflecting
material in a process called silvering, though common mirrors are backed with aluminium.
Using a process called sputtering, silver (and sometimes gold) can be applied to
glass at various thicknesses, allowing different amounts of light to penetrate.
Silver is usually reserved for coatings of specialized optics, and the
silvering most often seen in architectural glass and tinted windows on vehicles
is produced by sputtered aluminium, which is cheaper and less susceptible to
tarnishing and corrosion.[19]
Silver is the reflective coating of choice for solar reflectors.[20]
Medicinal
Main article: Medical uses of silver
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 are normally associated with these other metals. Its germicidal effects
kill many microbial organisms in vitro, but testing and standardization of silver
products is difficult.[23]
Hippocrates,
the "father of medicine",[2
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
coins in milk bottles to prolong the milk's freshness.[25]
Its germicidal effects increased its value in utensils and as jewelery. The exact
process of silver's germicidal effect is still not entirely understood,
although theories exist. One of these is the oligodynamic effect, which explains the effect
on microorganisms but would not explain antiviral effects.
PRICE
$15.50/TROY OZ
For more information:
mobile: +2348039721941
contact person: emeaba uche
e-mail: emeabau@yahoo.com
website: www.franchiseminerals.com
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