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Silver 1000 oz t (~31 kg) bullion bar
Silver is a very ductile, 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 has 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).[2][3][4] An exception to this is in radio-frequency engineering, particularly at VHF and higher frequencies, where silver plating to improve electrical conductivity of parts, including wires, is widely employed. Another notable exception is in high-end audio cables, where manufacturers claim that scaling copper conductors by 6% achieves slightly better results.[citation needed]
Among metals, pure silver has the highest thermal conductivity (the nonmetal diamond and superfluid helium II are higher) and one of the highest optical reflectivities.[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, the latter forming 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.
[edit] Tags:Cu,5,D,Na,De,M,Stable,It,Latin,Electrical Conductivity,Gold,Copper,Conductors,Ductile,Malleable,Coinage Metal,Polish,Electromagnets,Uranium,World War Ii,High-end Audio Cables,Thermal Conductivity,Diamond,Superfluid,Reflectivities,Contact Resistance,Latent Image,Tarnishes,Ozone,Hydrogen Sulfide,Hydrochloric Acid,Ph, | ||||||||||||||||||||||||||
| Isotopes | ||||||||||||||||||||||||||
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Main article: Isotopes of silver
Naturally occurring silver is composed of two stable isotopes, 107Ag and 109Ag, with 107Ag being the most abundant (51.839% natural abundance). Silver's isotopes are almost equal in abundance, something which is rare in the periodic table. Silver's atomic weight is 107.8682(2) g/mol.[7][8] Twenty-eight radioisotopes have been characterized, 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. This element has numerous meta states, the most stable being 108mAg (t1/2 = 418 years), 110mAg (t1/2 = 249.79 days) and 106mAg (t1/2 = 8.28 days). All of the remaining radioactive isotopes have half-lives that are less than an hour, and the majority of these have half-lives that are less than three minutes.
Isotopes of silver range in relative atomic mass from 93.943 (94Ag) to 126.936 (127Ag);[9] 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 palladium-to-silver ratio to yield measurable variations in 107Ag abundance. Radiogenic 107Ag was first discovered in the Santa Clara meteorite in 1978.[10] The discoverers suggest the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd–107Ag correlations observed in bodies that have clearly been melted since the accretion of the solar system must reflect the presence of unstable nuclides in the early solar system.[11]
[edit] Tags:Cadmium,/,Period,Iso,Half-life,Dm,Syn,Pd,Isotopes,Atomic Weight,Mol,Radioisotopes,Relative Atomic Mass,Decay Mode,Electron Capture,Beta Decay,Decay Products,Palladium,Iron,Radiogenic,Santa Clara,Nucleosynthetic,Accretion,Solar System, | ||||||||||||||||||||||||||
| Compounds | ||||||||||||||||||||||||||
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Silver metal dissolves readily in nitric acid (HNO3) to produce silver nitrate (AgNO3), a transparent crystalline solid that is photosensitive and readily soluble in water. Silver nitrate is used as the starting point for the synthesis of many other silver compounds, as an antiseptic, and as a yellow stain for glass in stained glass. Silver metal does not react with sulfuric acid, which is used in jewelry-making to clean and remove copper oxide firescale from silver articles after silver soldering or annealing. However, silver reacts readily with sulfur or hydrogen sulfide H2S to produce silver sulfide, a dark-colored compound familiar as the tarnish on silver coins and other objects. Silver sulfide also forms silver whiskers when silver electrical contacts are used in an atmosphere rich in hydrogen sulfide.
4 Ag + O2 + 2 H2S → 2 Ag2S + 2 H2O
Cessna 210 equipped with a silver iodide generator for cloud seeding
Silver chloride (AgCl) is precipitated from solutions of silver nitrate in the presence of chloride ions, and the other silver halides used in the manufacture of photographic emulsions are made in the same way, using bromide or iodide salts. Silver chloride is used in glass electrodes for pH testing and potentiometric measurement, and as a transparent cement for glass. Silver iodide has been used in attempts to seed clouds to produce rain.[6] Silver halides are highly insoluble in aqueous solutions and are used in gravimetric analytical methods.
Silver oxide (Ag2O), produced when silver nitrate solutions are treated with a base, is used as a positive electrode (anode) in watch batteries. Silver carbonate (Ag2CO3) is precipitated when silver nitrate is treated with sodium carbonate (Na2CO3).[12]
2 AgNO3 + 2 OH− → Ag2O + H2O + 2 NO3−
2 AgNO3 + Na2CO3 → Ag2CO3 + 2 NaNO3
Silver fulminate (AgONC), a powerful, touch-sensitive explosive used in percussion caps, is made by reaction of silver metal with nitric acid in the presence of ethanol (C2H5OH). Other dangerously explosive silver compounds are silver azide (AgN3), formed by reaction of silver nitrate with sodium azide (NaN3)[13], and silver acetylide, formed when silver reacts with acetylene gas.
Latent images formed in silver halide crystals are developed by treatment with alkaline solutions of reducing agents such as hydroquinone, metol (4-(methylamino)phenol sulfate) or ascorbate, which reduce the exposed halide to silver metal. Alkaline solutions of silver nitrate can be reduced to silver metal by reducing sugars such as glucose, and this reaction is used to silver glass mirrors and the interior of glass Christmas ornaments. Silver halides are soluble in solutions of sodium thiosulfate (Na2S2O3) which is used as a photographic fixer, to remove excess silver halide from photographic emulsions after image development.[12]
Silver metal is attacked by strong oxidizers such as potassium permanganate (KMnO4) and potassium dichromate (K2Cr2O7), and in the presence of potassium bromide (KBr), these compounds are used in photography to bleach silver images, converting them to silver halides that can either be fixed with thiosulfate or redeveloped to intensify the original image. Silver forms cyanide complexes (silver cyanide) that are soluble in water in the presence of an excess of cyanide ions. Silver cyanide solutions are used in electroplating of silver.[12]
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| Applications | ||||||||||||||||||||||||||
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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 to 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.
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| Currency | ||||||||||||||||||||||||||
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Main articles: Silver coin and Silver standard
Silver, in the form of electrum (a gold–silver alloy), was coined to produce money 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 pound sterling (£) reflects the fact it originally represented the value of one troy pound of sterling silver; other historical currencies, such as the French livre, have similar etymologies. During the 19th century, the bimetallism that prevailed in most countries was undermined by the discovery of large deposits of silver in the Americas; fearing a sharp decrease in the value of silver and thus the currency, most states switched to a gold standard by 1900. In the Spanish language, Plata means both silver and money.
The 20th century saw a gradual movement to fiat currency, with most of the world monetary system losing its link to precious metals after Richard Nixon took the United States dollar off the gold standard in 1971; the last currency backed by gold was the Swiss franc, which became a pure fiat currency on 1 May 2000. During this same period, silver gradually ceased to be used in circulating coins; the United States minted its last circulating silver coin in 1969.
The Royal Canadian Mint still makes many silver coins with various dollar denominations. Silver is used as a currency by many individuals, and is legal tender in the state of Utah.
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| Jewelry and silverware | ||||||||||||||||||||||||||
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Silver plate with goddess Minerva from the Hildesheim Treasure, 1st century BC
File:Royal Military College of Canada truth duty valour collar pin (1920–53) in silver (3 lugs).jpg
Royal Military College of Canada truth duty valour Collar pin (1920–53) in silver (3 lugs)
Main articles: jewelry and silversmith
Jewelry 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 90.0% fine silver can be marketed as "silver" (thus frequently stamped 900). Sterling silver (stamped 925) 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.
Silver is a constituent of almost all colored carat gold alloys and carat gold solders, giving the alloys paler color and greater hardness.[14] White 9 carat gold contains 62.5% silver and 37.5% gold, while 22 carat gold contains up to 91.7% gold and 8.4% silver or copper or a mixture of both.[14]
Historically, the training and guild organization of goldsmiths included silversmiths as well, and the two crafts remain largely overlapping. Unlike blacksmiths, silversmiths do not shape the metal while it is red-hot, but instead, work it at room temperature with gentle and carefully-placed hammer blows. The essence of silversmithing is to take a flat piece of metal and to transform it into a useful object using different hammers, stakes and other simple tools.[15]
While silversmiths specialize in, and principally work silver, they also work with other metals, such as gold, copper, steel, and brass. They make jewelry, silverware, armor, vases, and other artistic items. Because silver is such a malleable metal, silversmiths have a large range of choices with how they prefer to work the metal. Historically, silversmiths are mostly referred to as goldsmiths, which was usually the same guild. In the western Canadian silversmith tradition, guilds do not exist; however, mentoring through colleagues becomes a method of professional learning within a community of craftspeople.[16]
Silver is much cheaper than gold, though still valuable, and so is very popular with jewelers who are just starting out and cannot afford to make pieces in gold, or as a practicing material for goldsmith apprentices. Silver has also become very fashionable, and is used frequently in more artistic jewelry pieces.
Traditionally, silversmiths mostly made "silverware" (cutlery, table flatware, bowls, candlesticks and such). Only in more recent times has silversmithing become mainly work in jewelry, as much less solid silver tableware is now handmade.
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| Dentistry | ||||||||||||||||||||||||||
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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.
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| Photography and electronics | ||||||||||||||||||||||||||
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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 2007, of the 907 million ounces of silver in supply, just 117.6 million ounces (13%) were consumed by the photographic sector, about 50% of the amount used in photography in 1998. By 2010 the supply had increased by about 10% to 1056.8 million ounces of which 72.7 million ounces were used in the photographic sector, a decline of 38% compared with 2007.[17]
Some electrical and electronic products use silver for its superior conductivity, even when tarnished. The primary example of this is in high quality RF connectors. The increase in conductivity is also taken advantage of in RF engineering at VHF and higher frequencies, where conductors often cannot be scaled by 6%, due to tuning requirements, e.g.cavity filters. As an additional example, printed circuits and RFID antennas can be made using silver paints,[6][18] and computer keyboards use silver electrical contacts. Silver cadmium oxide is used in high voltage contacts because it can withstand arcing.
Some manufacturers produce audio connector cables, speaker wires, and power cables using silver conductors, which have a 6% higher conductivity than ordinary copper ones of identical dimensions, but cost very much more. Though debatable, many hi-fi enthusiasts believe silver wires improve sound quality.[citation needed]
Small devices, such as hearing aids and watches, commonly use silver oxide batteries due to their long life and high energy to weight ratio. Another usage is high-capacity silver-zinc and silver-cadmium batteries.
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| Mirrors and optics | ||||||||||||||||||||||||||
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Mirrors which need superior reflectivity for visible light are commonly 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 along with other optically tranparent layers are applied to glass creating low-e coatings used in high performance insulated glazing or IGU. The amount of silver used per window is quite small being on the order of 10 to 15 nanometers thick[19]. But the amount of silver coated glass world wide is is hundreds of millions of square meters per year leading to silver consumption on the order of 10 cubic meters or 100 metric tons/year. Silver color seen in architectural glass and tinted windows on vehicles is produced by sputtered chrome, stainless steel or other alloys. Silver is seldom used as the reflector in telescope mirrors where aluminum is generally prefered being cheaper and less susceptible to tarnishing and corrosion [20] Silver is the reflective coating of choice for solar reflectors.[21]
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| Other industrial and commercial applications | ||||||||||||||||||||||||||
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This Yanagisawa A9932J alto saxophone has a solid silver bell and neck with solid phosphor bronze body. The bell, neck and key-cups are extensively engraved. It was manufactured in 2008.
Silver and silver alloys are used in the construction of high quality musical wind instruments of many types.[22] Flutes, in particular, are commonly constructed of silver alloy or silver plated, both for appearance and for the frictional surface properties of silver.[23]
Silver's catalytic properties make it ideal for use as a catalyst in oxidation reactions, for example, Tags: | ||||||||||||||||||||||||||
stable - more infolatin - more infocopper - more infoconductors - more infohydrogen sulfide - more infocadmium - more infohalf-life - more infoisotopes - more infopalladium - more infosolid - more infojewelry - more infoalloy - more info
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