Silver

Silver

Overview
Silver is a metallic chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 Ag ' onMouseout='HidePop("74934")' href="http://www.absoluteastronomy.com/topics/Indo-European">Indo-European
Indo-European
Indo-European may refer to:* Indo-European languages** Aryan race, a 19th century and early 20th century term for those peoples who are the native speakers of Indo-European languages...

 root *arg- for "grey" or "shining") and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 47.
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Silver is a metallic chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the chemical symbol
Chemical symbol
A chemical symbol is a 1- or 2-letter internationally agreed code for a chemical element, usually derived from the name of the element, often in Latin. Only the first letter is capitalised...

 Ag ' onMouseout='HidePop("74934")' href="http://www.absoluteastronomy.com/topics/Indo-European">Indo-European
Indo-European
Indo-European may refer to:* Indo-European languages** Aryan race, a 19th century and early 20th century term for those peoples who are the native speakers of Indo-European languages...

 root *arg- for "grey" or "shining") and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 47. A soft, white, lustrous transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...

, it has the highest electrical conductivity of any element and the highest thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....

 of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 with gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 and other metals, and in minerals such as argentite
Argentite
Argentite was primarily treated as a mineral belonging to the galena group, cubic silver sulfide , occasionally found as uneven cubes and octahedra, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic lustre. All these forms are structurally not argentite, but...

 and chlorargyrite
Chlorargyrite
Chlorargyrite is the mineral form of silver chloride . Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric - hexoctahedral crystal class. Typically massive to columnar in occurrence it also has been found as colorless to...

. Most silver is produced as a byproduct of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

, and zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 refining
Refining
Refining is the process of purification of a substance or a form. The term is usually used of a natural resource that is almost in a usable form, but which is more useful in its pure form. For instance, most types of natural petroleum will burn straight from the ground, but it will burn poorly...

.

Silver has long been valued as a precious metal
Precious metal
A precious metal is a rare, naturally occurring metallic chemical element of high economic value.Chemically, the precious metals are less reactive than most elements, have high lustre, are softer or more ductile, and have higher melting points than other metals...

, and it is used to make ornaments, jewelry, high-value tableware, utensils (hence the term silverware
Silver (household)
Household silver or silverware includes dishware, cutlery and other household items made of sterling, Britannia or Sheffield plate silver. The term is often extended to items made of stainless steel...

), and currency coin
Coin
A coin is a piece of hard material that is standardized in weight, is produced in large quantities in order to facilitate trade, and primarily can be used as a legal tender token for commerce in the designated country, region, or territory....

s. Today, silver metal is also used in electrical contacts and conductors
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...

, in mirrors and in catalysis
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 of chemical reactions. Its compounds are used in photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

, and dilute silver nitrate solutions and other silver compounds are used as disinfectants and microbiocides. While many medical antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...

 uses of silver have been supplanted by antibiotics, further research into clinical potential continues.

Characteristics



Silver is a very ductile
Ductility
In materials science, ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized...

, malleable (slightly harder than gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

), monovalent coinage metal, with a brilliant white metallic luster that can take a high degree of polish
Polishing
Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action, leaving a surface with a significant specular reflection In some materials polishing is also able to reduce diffuse reflection to...

. 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
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 (mainly because of the wartime shortage of copper). 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.

Among metals, pure silver has the highest thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....

 (the nonmetal diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...

 and superfluid
Superfluid
Superfluidity is a state of matter in which the matter behaves like a fluid without viscosity and with extremely high thermal conductivity. The substance, which appears to be a normal liquid, will flow without friction past any surface, which allows it to continue to circulate over obstructions and...

 helium II are higher) and one of the highest optical reflectivities
Reflectivity
In optics and photometry, reflectivity is the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength...

. (Aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 slightly outdoes silver in parts of the visible spectrum, and silver is a poor reflector of ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 light). Silver also has the lowest contact resistance
Contact resistance
The term contact resistance refers to the contribution to the total resistance of a material which comes from the electrical leads and connections as opposed to the intrinsic resistance, which is an inherent property, independent of the measurement method...

 of any metal. Silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

s are photosensitive and are remarkable for their ability to record a latent image
Latent image
A latent image on photographic film is an invisible image produced by the exposure of the film to light. When the film is developed, the area that was exposed darkens and forms a visible image...

 that can later be developed
Photographic developer
In the processing of photographic films, plates or papers, the photographic developer is a chemical that makes the latent image on the film or print visible. It does this by reducing the silver halides that have been exposed to light to elemental silver in the gelatine matrix...

 chemically. Silver is stable in pure air and water, but tarnish
Tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish; it...

es when it is exposed to air or water containing ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

 or hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

, the latter forming a black layer of silver sulfide
Silver sulfide
Silver sulfide, Ag2S, is the sulfide of silver. This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in all solvents, but is degraded by strong acids. Silver sulfide features a covalent bond, as it is made up of...

 which can be cleaned off with dilute hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

. The most common oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

 of silver is +1 (for example, silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...

: AgNO3); in addition, +2 compounds (for example, silver(II) fluoride
Silver(II) fluoride
Silver fluoride is a chemical compound with the formula AgF2. It is a rare example of a silver compound. Silver is usually present in its +1 oxidation state. It is used as a fluorinating agent.-Preparation:...

: AgF2) and the less common +3 compounds (for example, potassium tetrafluoroargentate: K[AgF4] ) are known.

Isotopes



Naturally occurring silver is composed of two stable isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

s, 107Ag and 109Ag, with 107Ag being the most abundant (51.839% natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...

). Silver's isotopes are almost equal in abundance, something which is rare in the periodic table. Silver's atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

 is 107.8682(2) g/mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...

.
Twenty-eight radioisotopes have been characterized, the most stable being 105Ag with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 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
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

 from 93.943 (94Ag) to 126.936 (127Ag); the primary decay mode before the most abundant stable isotope, 107Ag, is electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...

 and the primary mode after is beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

. The primary decay product
Decay product
In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...

s before 107Ag are palladium
Palladium
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...

 (element 46) isotopes, and the primary products after are cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

 (element 48) isotopes.

The palladium isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 107Pd decays by beta emission to 107Ag with a half-life of 6.5 million years. Iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

s 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
Santa Clara, California
Santa Clara , founded in 1777 and incorporated in 1852, is a city in Santa Clara County, in the U.S. state of California. The city is the site of the eighth of 21 California missions, Mission Santa Clara de Asís, and was named after the mission. The Mission and Mission Gardens are located on the...

 meteorite in 1978. The discoverers suggest the coalescence and differentiation of iron-cored small planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s may have occurred 10 million years after a nucleosynthetic event. 107Pd–107Ag correlations observed in bodies that have clearly been melted since the accretion
Accretion (astrophysics)
In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc. Accretion discs are common around smaller stars or stellar remnants...

 of the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 must reflect the presence of unstable nuclides in the early solar system.

Compounds


Silver metal dissolves readily in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

  to produce silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...

 , 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
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

, and as a yellow stain for glass in stained glass
Stained glass
The term stained glass can refer to coloured glass as a material or to works produced from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant buildings...

. Silver metal does not react with sulfuric acid, which is used in jewelry-making to clean and remove copper oxide firescale
Firescale
Firescale, also known as firestain, is a red or purple stain that appears on mixtures of silver and copper, such as sterling silver. At high temperatures, oxygen mixes with the copper to form cuprous oxide and then cupric oxide...

 from silver articles after silver soldering
Brazing
Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux...

 or annealing
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...

. However, silver reacts readily with sulfur or hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

  to produce silver sulfide
Silver sulfide
Silver sulfide, Ag2S, is the sulfide of silver. This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in all solvents, but is degraded by strong acids. Silver sulfide features a covalent bond, as it is made up of...

, a dark-colored compound familiar as the tarnish on silver coin
Silver coin
Silver coins are possibly the oldest mass produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks. Their silver drachmas were popular trade coins....

s and other objects. Silver sulfide also forms silver whiskers when silver electrical contacts are used in an atmosphere rich in hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

.
4 Ag + O2 + 2 H2S → 2 Ag2S + 2 H2O

Silver chloride
Silver chloride
Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water . Upon illumination or heating, silver chloride converts to silver , which is signalled by greyish or purplish coloration to some samples...

  is precipitated from solutions of silver nitrate in the presence of chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

 ions, and the other silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...

s used in the manufacture of photographic emulsion
Photographic emulsion
Photographic emulsion is a light-sensitive colloid, such as gelatin, coated onto a substrate. In silver-gelatin photography, the emulsion consists of silver halide crystals suspended in gelatin, and the substrate may be glass, plastic film, paper or fabric....

s are made in the same way, using bromide
Bromide
A bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...

 or iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

s. Silver chloride is used in glass electrode
Glass electrode
A glass electrode is a type of ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion. It is an important part of the instrumentation for chemical analysis and physico-chemical studies. In modern practice, widely used membranous ion-selective electrodes are part...

s for pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 testing and potentiometric measurement, and as a transparent cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

 for glass. Silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...

 has been used in attempts to seed clouds
Cloud seeding
Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...

 to produce rain. Silver halides are highly insoluble in aqueous solutions and are used in gravimetric analytical
Wet chemistry
Wet chemistry is a term used to refer to chemistry generally done in the liquid phase. It is also known as bench chemistry because many of the tests performed are done at a lab bench.-Materials:...

 methods.

Silver oxide , produced when silver nitrate solutions are treated with a base, is used as a positive electrode (anode
Anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....

) in watch batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

. Silver carbonate
Silver carbonate
Silver carbonate is the chemical compound with the formula Ag2CO3. Silver carbonate is yellow but typical samples are grayish due to the presence of elemental silver. It is poorly soluble in water, like most transition metal carbonates. Silver carbonate is used as a reagent in organic synthesis...

  is precipitated when silver nitrate is treated with sodium carbonate .
2 AgNO3 + 2 OH- → Ag2O + H2O + 2 NO3-
2 AgNO3 + Na2CO3 → Ag2CO3 + 2 NaNO3

Silver fulminate
Silver fulminate
Silver fulminate is an explosive, ionic, fulminic acid salt of silver.Silver fulminate is a primary explosive that has very little practical value due to its extreme sensitivity to impact, heat, pressure and electricity...

 , a powerful, touch-sensitive explosive used in percussion cap
Percussion cap
The percussion cap, introduced around 1830, was the crucial invention that enabled muzzleloading firearms to fire reliably in any weather.Before this development, firearms used flintlock ignition systems which produced flint-on-steel sparks to ignite a pan of priming powder and thereby fire the...

s, is made by reaction of silver metal with nitric acid in the presence of ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

 . Another dangerously explosive silver compound is silver azide
Silver azide
Silver azide is the chemical compound with the formula AgN3. This colorless solid is a well-known explosive.-Structure and chemistry:Silver azide can be prepared by treating an aqueous solution of silver nitrate with sodium azide...

 , formed by reaction of silver nitrate with sodium azide .

Latent image
Latent image
A latent image on photographic film is an invisible image produced by the exposure of the film to light. When the film is developed, the area that was exposed darkens and forms a visible image...

s formed in silver halide crystals are developed by treatment with alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

ne solutions of reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...

s such as hydroquinone
Hydroquinone
Hydroquinone, also benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, having the chemical formula C6H42. Its chemical structure, shown in the table at right, has two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid...

, metol
Metol
Metol is the chemical compound with the name monomethyl-p-aminophenol hemisulfate. It is a developing agent used in black & white photographic developers...

 (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 sugar
Reducing sugar
A reducing sugar is any sugar that either has an aldehyde group or is capable of forming one in solution through isomerisation. This functional group allows the sugar to act as a reducing agent, for example in the Tollens' test or Benedict's test.-Chemistry:...

s such as glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

, and this reaction is used to silver glass mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...

s and the interior of glass Christmas ornament
Christmas ornament
Christmas ornaments are decorations that are used to festoon a Christmas tree.Ornaments take many different forms, from a simple round ball to highly artistic designs...

s. Silver halides are soluble in solutions of sodium thiosulfate
Sodium thiosulfate
Sodium thiosulfate , also spelled sodium thiosulphate, is a colorless crystalline compound that is more familiar as the pentahydrate, Na2S2O3•5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.”...

  which is used as a photographic fixer
Photographic fixer
Photographic fixer is a chemical or a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leaving behind the reduced metallic silver...

, to remove excess silver halide from photographic emulsions after image development.

Silver metal is attacked by strong oxidizers such as potassium permanganate
Potassium permanganate
Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...

  and potassium dichromate , and in the presence of potassium bromide
Potassium bromide
Potassium bromide is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the United States. Its action is due to the bromide ion...

 , these compounds are used in photography to bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...

 silver images, converting them to silver halides that can either be fixed with thiosulfate
Thiosulfate
Thiosulfate is an oxyanion of sulfur. The prefix thio indicates that thiosulfate ion is a sulfate ion with one oxygen replaced by a sulfur. Thiosulfate occurs naturally and is produced by certain biochemical processes...

 or redeveloped to intensify the original image. Silver forms cyanide
Cyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 complexes (silver cyanide
Silver cyanide
Silver cyanide is the chemical compound with the formula AgCN. This white solid forms upon treatment of solutions containing Ag+ with cyanide. This precipitation step is used in some schemes to recover silver from solution...

) that are soluble in water in the presence of an excess of cyanide ions. Silver cyanide solutions are used in electroplating
Electroplating
Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...

 of silver.

Applications


Many well known uses of silver involve its precious metal
Precious metal
A precious metal is a rare, naturally occurring metallic chemical element of high economic value.Chemically, the precious metals are less reactive than most elements, have high lustre, are softer or more ductile, and have higher melting points than other metals...

 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
COinS
ContextObjects in Spans, commonly abbreviated COinS, is a method to embed bibliographic metadata in the HTML code of web pages. This allows bibliographic software to publish machine-readable bibliographic items and client reference management software to retrieve bibliographic metadata. The...

 and investment bars) or make objects symbolic of high social or political rank.

Currency



Silver, in the form of electrum
Electrum
Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. It has also been produced artificially. The ancient Greeks called it 'gold' or 'white gold', as opposed to 'refined gold'. Its color ranges from pale to bright yellow, depending on the...

 (a gold-silver alloy), was coined to produce money around 700 BC by the Lydia
Lydia
Lydia was an Iron Age kingdom of western Asia Minor located generally east of ancient Ionia in the modern Turkish provinces of Manisa and inland İzmir. Its population spoke an Anatolian language known as Lydian....

ns. 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
ISO 4217
ISO 4217 is a standard published by the International Standards Organization, which delineates currency designators, country codes , and references to minor units in three tables:* Table A.1 – Current currency & funds code list...

 XAG. The name of the pound sterling
Pound sterling
The pound sterling , commonly called the pound, is the official currency of the United Kingdom, its Crown Dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands, British Antarctic Territory and Tristan da Cunha. It is subdivided into 100 pence...

 (£) reflects the fact it originally represented the value of one troy pound of sterling silver; other historical currencies, such as the French livre
French livre
The livre was the currency of France until 1795. Several different livres existed, some concurrently. The livre was the name of both units of account and coins.-Etymology:...

, have similar etymologies. During the 19th century, the bimetallism
Bimetallism
In economics, bimetallism is a monetary standard in which the value of the monetary unit is defined as equivalent both to a certain quantity of gold and to a certain quantity of silver; such a system establishes a fixed rate of exchange between the two metals...

 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
Gold standard
The gold standard is a monetary system in which the standard economic unit of account is a fixed mass of gold. There are distinct kinds of gold standard...

 by 1900.

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
Richard Nixon
Richard Milhous Nixon was the 37th President of the United States, serving from 1969 to 1974. The only president to resign the office, Nixon had previously served as a US representative and senator from California and as the 36th Vice President of the United States from 1953 to 1961 under...

 took the United States dollar
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....

 off the gold standard in 1971; the last currency backed by gold was the Swiss franc
Swiss franc
The franc is the currency and legal tender of Switzerland and Liechtenstein; it is also legal tender in the Italian exclave Campione d'Italia. Although not formally legal tender in the German exclave Büsingen , it is in wide daily use there...

, 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.

Jewelry and silverware



Jewelry and silverware are traditionally made from sterling silver
Sterling silver
Sterling silver is an alloy of silver containing 92.5% by mass of silver and 7.5% by mass of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925....

 (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. Britannia silver
Britannia silver
Britannia silver is an alloy of silver containing 95.84% silver, with the balance usually copper.This standard was introduced in England by Act of Parliament in 1697 to replace sterling silver as the obligatory standard for items of "wrought plate"...

 is an alternative, hallmark
Hallmark
A hallmark is an official mark or series of marks struck on items made of precious metals — platinum, gold, silver and in some nations, palladium...

-quality standard containing 95.8% silver, often used to make silver tableware and wrought plate. With the addition of germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

, the patented modified alloy Argentium Sterling silver
Argentium sterling silver
Argentium Sterling silver is a modern sterling silver alloy which modifies the traditional alloy by replacing some of the copper with the metalloid germanium...

 is formed, with improved properties, including resistance to firescale
Firescale
Firescale, also known as firestain, is a red or purple stain that appears on mixtures of silver and copper, such as sterling silver. At high temperatures, oxygen mixes with the copper to form cuprous oxide and then cupric oxide...

.

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
Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...

 (for a bright, shiny look) or gold.

Silver is a constituent of almost all colored carat gold alloys
Colored gold
While pure gold is yellow in color, colored gold can be developed into various colors. These colors are generally obtained by alloying gold with other elements in various proportions....

 and carat gold solders, giving the alloys paler color and greater hardness. 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. The more copper added, the more "orange" the gold becomes. Rose Gold (stamped 375 or 9K, can be stamped 9c) was very popular in the UK in the late 19th century.

Historically, the training and guild organization of goldsmith
Goldsmith
A goldsmith is a metalworker who specializes in working with gold and other precious metals. Since ancient times the techniques of a goldsmith have evolved very little in order to produce items of jewelry of quality standards. In modern times actual goldsmiths are rare...

s 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 hammer
Hammer
A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head,...

s, stakes and other simple tools,.

While silversmiths specialize in, and principally work, silver, they also work with other metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

s, such as gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, and brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

. They make jewelry, silverware
Silver (household)
Household silver or silverware includes dishware, cutlery and other household items made of sterling, Britannia or Sheffield plate silver. The term is often extended to items made of stainless steel...

, 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 goldsmith
Goldsmith
A goldsmith is a metalworker who specializes in working with gold and other precious metals. Since ancient times the techniques of a goldsmith have evolved very little in order to produce items of jewelry of quality standards. In modern times actual goldsmiths are rare...

s, which was usually the same guild
Guild
A guild is an association of craftsmen in a particular trade. The earliest types of guild were formed as confraternities of workers. They were organized in a manner something between a trade union, a cartel, and a secret society...

. 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.

Silver is much cheaper than gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, 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
Silver (household)
Household silver or silverware includes dishware, cutlery and other household items made of sterling, Britannia or Sheffield plate silver. The term is often extended to items made of stainless steel...

" (cutlery
Cutlery
Cutlery refers to any hand implement used in preparing, serving, and especially eating food in the Western world. It is more usually known as silverware or flatware in the United States, where cutlery can have the more specific meaning of knives and other cutting instruments. This is probably the...

, 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.

Dentistry


Silver can be alloyed with mercury, tin and other metals at room temperature to make amalgams
Amalgam (chemistry)
An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore.The...

 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
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...

. 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 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%.

Some electrical and electronic products use silver for its superior conductivity, even when tarnished. The primary example of this is in high quality RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 connectors. The increase in conductivity is also taken advantage of in RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 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
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 and RFID antennas can be made using silver paints, and computer keyboards use silver electrical contacts. Silver cadmium oxide is used in high voltage contacts because it can withstand arcing
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...

.

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.

Small devices, such as hearing aids and watches, commonly use silver oxide batteries
Silver-oxide battery
A silver oxide battery , not to be confused with a similar but different silver–zinc battery, which is a secondary cell, is a primary cell with relatively very high energy/weight ratio. They are costly due to the high price of silver...

 due to their long life and high energy to weight ratio. Another usage is high-capacity silver-zinc
Silver-oxide battery
A silver oxide battery , not to be confused with a similar but different silver–zinc battery, which is a secondary cell, is a primary cell with relatively very high energy/weight ratio. They are costly due to the high price of silver...

 and silver-cadmium batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

.

Mirrors and optics


Mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...

s which need superior reflectivity for visible light are made with silver as the reflecting material in a process called silvering
Silvering
Silvering is the chemical process of coating glass with a reflective substance. When glass mirrors first gained widespread usage in Europe during the 16th century, most were made of an amalgam of tin and mercury, but by the 19th century mirrors were commonly made through a process by which silver...

, though common mirrors are backed with aluminium. Using a process called sputtering
Sputtering
Sputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of 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. Silver is the reflective coating of choice for solar reflectors.

Other industrial and commercial applications


Silver and silver alloys are used in the construction of high quality musical wind instruments of many types. Flutes, in particular, are commonly constructed of silver alloy or silver plated, both for appearance and for the frictional surface properties of silver.

Silver's catalytic properties make it ideal for use as a catalyst in oxidation reactions, for example, the production of formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

 from methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 and air by means of silver screens or crystallite
Crystallite
Crystallites are small, often microscopic crystals that, held together through highly defective boundaries, constitute a polycrystalline solid. Metallurgists often refer to crystallites as grains.- Details :...

s containing a minimum 99.95 weight-percent silver. Silver (upon some suitable support) is probably the only catalyst available today to convert ethylene
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

 to ethylene oxide
Ethylene oxide
Ethylene oxide, also called oxirane, is the organic compound with the formula . It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape . This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered...

 (later hydrolyzed to ethylene glycol
Ethylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...

, used for making polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

s)— an important industrial reaction. It is also used in the Oddy test
Oddy test
The Oddy test is a procedure created at the British Museum by conservation scientist Andrew Oddy in 1973, in order to test materials for safety in and around art objects....

 to detect reduced sulfur compounds and carbonyl sulfides.

Because silver readily absorbs free neutrons, it is commonly used to make control rods to regulate the fission chain reaction
Nuclear chain reaction
A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...

 in pressurized water nuclear reactors
Pressurized water reactor
Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...

, generally in the form of an alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 containing 80% silver, 15% indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

, and 5% cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

.

Silver is used to make solder
Solder
Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...

 and brazing
Brazing
Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux...

 alloys, and as a thin layer on bearing surfaces can provide a significant increase in galling resistance and reduce wear under heavy load, particularly against steel.

Medical


Silver ions and silver compounds show a toxic effect on some bacteria, viruses, algae and fungi, typical for heavy metals like lead or mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

, but without the high toxicity to humans normally associated with these other metals. Its germicidal effects kill many microbial organisms in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

, but testing and standardization of silver products is difficult.

Hippocrates
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

, the "father of medicine", wrote that silver had beneficial healing and antidisease properties, and the Phoenicians stored water, wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

, and vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 in silver bottles to prevent spoiling. In the early 20th century, people would put silver coins in milk bottles to prolong the milk's freshness. Its germicidal effects increased its value in utensils and as jewellery. The exact process of silver's germicidal effect is still not entirely understood, although theories exist. One of these is the oligodynamic effect
Oligodynamic effect
The oligodynamic effect was discovered in 1893 by the Swiss Karl Wilhelm von Nägeli as a toxic effect of metal ions on living cells, algae, molds, spores, fungi, viruses, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations...

, which explains the effect on microorganisms, but would not explain antiviral effects.

Silver is widely used in topical gels and impregnated into bandages because of its wide-spectrum antimicrobial activity. The antimicrobial properties of silver stem from the chemical properties of its ionized form, Ag+. This ion forms strong molecular bonds with other substances used by bacteria to respire
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...

, such as molecules containing sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

. When the Ag+ ion forms a complex with these molecules, they are rendered unusable by the bacteria, depriving them of necessary compounds and eventually leading to their death.

Silver compounds were used to prevent infection in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 before the advent of antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s. Silver nitrate solution use continued, then was largely replaced by silver sulfadiazine cream (SSD cream), which generally became the "standard of care" for the antibacterial and antibiotic treatment of serious burns until the late 1990s. Now, other options, such as silver-coated dressings (activated silver dressings), are used in addition to SSD cream. However, the evidence for the effectiveness of such silver-treated dressings is mixed, and although the evidence is promising, it is marred by the poor quality of the trials used to assess these products. Consequently, a systematic review
Systematic review
A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine...

 by the Cochrane Collaboration
Cochrane Collaboration
The Cochrane Collaboration is a group of over 28,000 volunteers in more than 100 countries who review the effects of health care interventions tested in biomedical randomized controlled trials. A few more recent reviews have also studied the results of non-randomized, observational studies...

 (published in 2008) found insufficient evidence to recommend the use of silver-treated dressings to treat infected wounds.

There has been renewed interest in silver as a broad-spectrum antimicrobial agent. One application has silver being used with alginate, a naturally occurring biopolymer
Biopolymer
Biopolymers are polymers produced by living organisms. Since they are polymers, Biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed...

 derived from seaweed, in a range of products designed to prevent infections as part of wound
Wound
A wound is a type of injury in which skin is torn, cut or punctured , or where blunt force trauma causes a contusion . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.-Open:...

 management procedures, particularly applicable to burn
Burn (injury)
A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation or friction. Most burns affect only the skin . Rarely, deeper tissues, such as muscle, bone, and blood vessels can also be injured...

 victims. In 2007, a company introduced a glass product they claimed had antibacterial properties by coating the glass with a thin layer of silver. In addition, in 2007 the U.S. Food and Drug Administration (FDA) approved an endotracheal breathing tube with a fine coat of silver for use in mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...

, after studies found it reduced the risk of ventilator-associated pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

.

Another example uses the known enhanced antibacterial action of silver by applying an electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

. In 2009, the antibacterial action of silver electrodes was found to be greatly improved if the electrodes were covered with silver nanorods
Silver Nano
Silver Nano is a trademark name of an antibacterial technology which uses silver nanoparticles in washing machines, refrigerators, air conditioners, air purifiers and vacuum cleaners introduced by Samsung in April 2003....

. The University of Missouri
University of Missouri
The University of Missouri System is a state university system providing centralized administration for four universities, a health care system, an extension program, five research and technology parks, and a publishing press. More than 64,000 students are currently enrolled at its four campuses...

 has found silver nanoparticles threaten benign bacteria which extract ammonia from sewage treatment
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...

 systems. A serious concern is the eventual spread of the toxin into rivers, streams, lakes and ultimately the oceans. A note of caution is sounded by Martin A. Philbert, professor of toxicology at the University of Michigan, Ann Arbor. "In the context of environmental health, the scientific community will have to pay close attention to those physicochemical properties of engineered nanomaterials that defeat or circumvent normal cellular processes and lend themselves to indiscriminate penetration of biological barriers, tissues, and cellular systems."

Silver is commonly used in catheters. Silver alloy catheters are more effective than standard catheters for reducing bacteriuria
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...

 in adults having short term catheterisation in hospitals. This meta-analysis clarifies discrepant results among trials of silver-coated urinary catheters by revealing silver alloy catheters are significantly more effective in preventing urinary tract infections than are silver oxide catheters. Though silver alloy urinary catheters cost about $6 more than standard urinary catheters, they may be worth the extra cost, since catheter-related infection is a common cause of nosocomial infection and bacteremia.

Various silver compounds, devices to make homeopathic solutions and colloidal silver suspensions are sold as remedies for numerous conditions. Although most colloidal silver
Colloidal silver
The medical uses of silver include its incorporation into wound dressings to treat external infections, and its use as an antiseptic and disinfectant in medical appliances...

 preparations are harmless, there are cases where excessive consumption led to argyria
Argyria
Argyria is a condition caused by improper exposure to chemical forms of the element silver, silver dust, or silver compounds. The most dramatic symptom of argyria is that the skin becomes blue or bluish-grey colored. Argyria may be found as generalized argyria or local argyria...

 over a period of months or years. High consumption doses of colloidal silver can result in coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...

, pleural edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...

, and hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...

.

Clothing


Silver inhibits the growth of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 on clothing, such as socks, so is added to reduce odor
Odor
An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also commonly called scents, which can refer to both pleasant and unpleasant odors...

s and the risk of bacterial and fungal infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

. It is incorporated into clothing or shoes either by integrating silver nanoparticles
Silver nanoparticles
Silver nanoparticles are nanoparticles of silver, i.e. silver particles of between 1 nm and 100 nm in size. While frequently described as being 'silver' some are composed of a large percentage of silver oxide due to their large ratio of surface-to-bulk silver atoms.-Synthesis:There are...

 into the polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 from which yarns are made or by coating yarns with silver. The loss of silver during washing varies between textile technologies, and the resultant effect on the environment is not yet fully known.

History


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. The word "silver" appears in Anglo-Saxon
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 in various spellings such as seolfor and siolfor. A similar form is seen throughout the Germanic languages
Germanic languages
The Germanic languages constitute a sub-branch of the Indo-European language family. The common ancestor of all of the languages in this branch is called Proto-Germanic , which was spoken in approximately the mid-1st millennium BC in Iron Age northern Europe...

 (compare Old High German
Old High German
The term Old High German refers to the earliest stage of the German language and it conventionally covers the period from around 500 to 1050. Coherent written texts do not appear until the second half of the 8th century, and some treat the period before 750 as 'prehistoric' and date the start of...

 silabar and silbir). The chemical symbol Ag is from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for "silver", argentum (compare Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 άργυρος, árgyros), from the Indo-European
Indo-European
Indo-European may refer to:* Indo-European languages** Aryan race, a 19th century and early 20th century term for those peoples who are the native speakers of Indo-European languages...

 root *arg- meaning "white" or "shining". Silver has been known since ancient times. Mentioned in the book of Genesis, slag heaps found in Asia Minor
Asia Minor
Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

 and on the islands of the Aegean Sea
Aegean Sea
The Aegean Sea[p] is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...

 indicate silver was being separated from lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 as early as the 4th millennium
4th millennium BC
The 4th millennium BC saw major changes in human culture. It marked the beginning of the Bronze Age and of writing.The city states of Sumer and the kingdom of Egypt were established and grew to prominence. Agriculture spread widely across Eurasia...

 BC using surface mining.

The stability of the Roman currency
Roman currency
The Roman currency during most of the Roman Republic and the western half of the Roman Empire consisted of coins including the aureus , the denarius , the sestertius , the dupondius , and the as...

 relied to a high degree on the supply of silver bullion, which Roman miners
Roman metallurgy
Metals and metal working had been known to the people of modern Italy since the Bronze Age. By 86 BC, Rome had already expanded to control an immense expanse of the Mediterranean...

 produced on a scale unparalleled before the discovery of the New World. Reaching a peak production of 200 t per year, an estimated silver stock of 10,000 t circulated in the Roman economy
Roman economy
The history of the Roman economy covers the period of the Roman Republic and the Roman Empire.Recent research has led to a positive reevaluation of the size and sophistication of the Roman economy within the constraints generally imposed on agricultural societies in the preindustrial age.- Gross...

 in the middle of the second century AD, five to ten times larger than the combined amount of silver available to medieval Europe
Early Middle Ages
The Early Middle Ages was the period of European history lasting from the 5th century to approximately 1000. The Early Middle Ages followed the decline of the Western Roman Empire and preceded the High Middle Ages...

 and the Caliphate around 800 AD.

Recorded use of silver to prevent infection dates to ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 and Rome
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

; it was rediscovered in the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, when it was used for several purposes, such as to disinfect water and food during storage, and also for the treatment of burns and wounds as wound dressing. In the 19th century, sailors on long ocean voyages would put silver coin
Coin
A coin is a piece of hard material that is standardized in weight, is produced in large quantities in order to facilitate trade, and primarily can be used as a legal tender token for commerce in the designated country, region, or territory....

s in barrels of water and wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 to keep the liquid potable. Pioneers in America used the same idea as they made their journey from coast to coast. Silver solutions were approved in the 1920s by the US Food and Drug Administration for use as antibacterial agents.

In the Gospels, Jesus' disciple Judas Iscariot
Judas Iscariot
Judas Iscariot was, according to the New Testament, one of the twelve disciples of Jesus. He is best known for his betrayal of Jesus to the hands of the chief priests for 30 pieces of silver.-Etymology:...

 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.

In certain circumstances, Islam permits Muslim men to wear silver jewelry. Muhammad
Muhammad
Muhammad |ligature]] at U+FDF4 ;Arabic pronunciation varies regionally; the first vowel ranges from ~~; the second and the last vowel: ~~~. There are dialects which have no stress. In Egypt, it is pronounced not in religious contexts...

 himself wore a silver signet ring .

World War II


During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, the short supply of copper led to the substitution of silver in many industrial applications. The United States government loaned out silver from its massive reserve located in the West Point vaults to a wide range of industrial users. One very important use was for bus bars for new aluminum plants needed to make aircraft. During the war many electrical connectors and switches were silver plated. Another use was aircraft master rod bearings and other types of bearings. Since silver can replace tin in solder at a lower volume, a large amount of tin was freed up for other uses by substituting government silver. Silver was also used as the reflector in searchlights and other types of lights. One high-tech use of silver was for conductors at Oak Ridge National Laboratory
Oak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...

 used in calutrons to isolate uranium as part of the Manhattan project. (After the war ended the silver was returned to the vaults.) Silver was used in nickels
Nickel (United States coin)
The nickel is a five-cent coin, representing a unit of currency equaling five hundredths of one United States dollar. A later-produced Canadian nickel five-cent coin was also called by the same name....

 during the war to save that metal for use in steel alloys.

Occurrence and extraction



Silver is found in native form, as an alloy with gold (electrum
Electrum
Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. It has also been produced artificially. The ancient Greeks called it 'gold' or 'white gold', as opposed to 'refined gold'. Its color ranges from pale to bright yellow, depending on the...

), and in ores containing sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

 or chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

. Ores include argentite
Argentite
Argentite was primarily treated as a mineral belonging to the galena group, cubic silver sulfide , occasionally found as uneven cubes and octahedra, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic lustre. All these forms are structurally not argentite, but...

 (Ag2S), chlorargyrite
Chlorargyrite
Chlorargyrite is the mineral form of silver chloride . Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric - hexoctahedral crystal class. Typically massive to columnar in occurrence it also has been found as colorless to...

 (AgCl) which includes horn silver, and pyrargyrite
Pyrargyrite
Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonide, Ag3SbS3. Known also as dark red silver ore or ruby silver, it is an important source of the metal....

 (Ag3SbS3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 and Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...

. Peru, Bolivia and Mexico have been mining silver since 1546, and are still major world producers. Top silver-producing mines are Cannington (Australia), Fresnillo (Mexico), San Cristobal (Bolivia), Antamina (Peru), Rudna (Poland), and Penasquito (Mexico). Top near-term mine development projects through 2015 are Pascua Lama (Chile), Navidad (Argentina), Jaunicipio (Mexico), Malku Khota (Bolivia), and Hackett River (Canada).

The metal is primarily produced through electrolytic
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 copper refining, gold, nickel and zinc refining, and by application of the Parkes process
Parkes process
The Parkes process is a pyrometallurgical industrial process for removing silver from lead, during the production of bullion. It is an example of liquid-liquid extraction....

 on lead metal obtained from lead ores that contain small amounts of silver. Commercial-grade fine silver is at least 99.9% pure, and purities greater than 99.999% are available. In 2010, Peru was the top producer of silver (4,000 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s or 18% of the world's total), closely followed by Mexico (3,500 t) and China (3,000 t).

Price



At an April 2011 price of about $49 USD per troy ounce, silver is about 1/30th the price of gold. The ratio has varied from 1/15 to 1/100 in the past 100 years.

In 1980, the silver price rose to a peak for modern times of US$49.45 per troy ounce
Troy ounce
The troy ounce is a unit of imperial measure. In the present day it is most commonly used to gauge the weight of precious metals. One troy ounce is nowadays defined as exactly 0.0311034768 kg = 31.1034768 g. There are approximately 32.1507466 troy oz in 1 kg...

 (TO) due to market manipulation
Market manipulation
Market manipulation describes a deliberate attempt to interfere with the free and fair operation of the market and create artificial, false or misleading appearances with respect to the price of, or market for, a security, commodity or currency...

 of Nelson Bunker Hunt
Nelson Bunker Hunt
Nelson Bunker Hunt is an American oil company executive. He is best known as a former billionaire whose fortune collapsed after he and his brother William Herbert Hunt tried but failed to corner the world market in silver. He is also a successful thoroughbred horse breeder.-Personal:Hunt was born...

 and Herbert Hunt
Herbert Hunt
Herbert J. Hunt was an English writer and translator.He was educated at Lichfield Cathedral Choir School, the Lichfield Grammar School and Magdalen College...

 inflation adjusted to 2011 this is approximately U$D150 per troy ounce. Some time after Silver Thursday
Silver Thursday
Silver Thursday was an event that occurred in the silver commodity markets on Thursday, 27 March 1980. A steep fall in silver prices led to panic on commodity and futures exchanges.-Background:...

, the price was back to $10/TO. From 2001 to 2010, the price moved from $4.37 to $20.19 (Average London US$/oz). According to the Silver Institute, silver's recent gains have greatly stemmed from a rise in investor interest and an increase in fabrication demand. In late April 2011, silver reached an all-time high of $49.76/TO.

In earlier times, silver has commanded much higher prices. In the early 15th century, the price of silver is estimated to have surpassed $1200 per ounce, based on 2011 dollars. The discovery of massive silver deposits in the New World during the succeeding centuries has caused the price to diminish greatly.

The price of silver is important in Judaic law. The lowest fiscal
Fiscal policy
In economics and political science, fiscal policy is the use of government expenditure and revenue collection to influence the economy....

 amount a Jewish court, or Beth Din
Beth din
A beth din, bet din, beit din or beis din is a rabbinical court of Judaism. In ancient times, it was the building block of the legal system in the Biblical Land of Israel...

, 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. In a Jewish tradition, still continuing today, on the first birth-day of a first-born son, the parents pay the price of five pure-silver coins to a Kohen. Today, the Israel mint fixes the coins at 117 grams of silver. The Kohen will often give those silver coins back as a gift for the child to inherit.

Human exposure and consumption


Silver plays no known natural biological role in humans, and possible health effects of silver are a disputed subject. Silver itself is not toxic, but most silver salts are, and some may be carcinogenic. Silver and compounds containing it (such as colloidal silver
Colloidal silver
The medical uses of silver include its incorporation into wound dressings to treat external infections, and its use as an antiseptic and disinfectant in medical appliances...

) can be absorbed into the circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 and become deposited in various body tissues, leading to argyria
Argyria
Argyria is a condition caused by improper exposure to chemical forms of the element silver, silver dust, or silver compounds. The most dramatic symptom of argyria is that the skin becomes blue or bluish-grey colored. Argyria may be found as generalized argyria or local argyria...

, which results in a blue-grayish pigmentation of the skin, eyes, and mucous membrane
Mucous membrane
The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s. 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
Cyanosis
Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface being low on oxygen. The onset of cyanosis is 2.5 g/dL of deoxyhemoglobin. The bluish color is more readily apparent in those with high hemoglobin counts than it is...

.

Monitoring exposure


Overexposure to silver can occur in workers in the metallurgical industry, persons taking silver-containing dietary supplements, patients who have received silver sulfadiazine treatment and individuals who accidentally or intentionally ingest silver salts. Silver concentrations in whole blood, plasma, serum or urine may be measured to monitor for safety in exposed workers, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage.

Use in food


Silver is used in food coloring, it has the E174
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 designation, and is approved in the European Union. The amount of silver in the coating of dragée or as in cookie decoration is minuscule.
The safety of silver for use in food is disputed. Traditional Indian dishes sometimes include the use of decorative silver foil known as vark
Vark
Vark, Varak, Varakh or Varkh, Varq is any foil / layer of very pure, typically silver, used for garnishing Indian sweets. The silver is edible, though flavorless. Large quantities of ingested elemental silver can cause argyria, but the use of vark is not considered harmful to the body, since the...

, and in various cultures, silver dragée are used to decorate cakes, cookies, and other dessert items. The use of silver as a food additive is not approved in the United States and Australia..

See also

  • List of silver compounds
  • Silver as an investment
    Silver as an investment
    Silver, like other precious metals, may be used as an investment. For more than four thousand years, silver has been regarded as a form of money and store of value. However, since the end of the silver standard, silver has lost its role as legal tender in many developed countries such as the...

  • Silver coin
    Silver coin
    Silver coins are possibly the oldest mass produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks. Their silver drachmas were popular trade coins....

  • Silverpoint
    Silverpoint
    Silverpoint is a traditional drawing technique first used by Medieval scribes on manuscripts.-History:A silverpoint drawing is made by dragging a silver rod or wire across a surface, often prepared with gesso or primer. Silverpoint is one of several types of metalpoint used by scribes, craftsmen...

     drawing
  • Vark
    Vark
    Vark, Varak, Varakh or Varkh, Varq is any foil / layer of very pure, typically silver, used for garnishing Indian sweets. The silver is edible, though flavorless. Large quantities of ingested elemental silver can cause argyria, but the use of vark is not considered harmful to the body, since the...

     – a pastry/confectionery decoration

External links