Silver

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Silver, 47Ag
Silver
Appearancelustrous white metal
Standard atomic weight Ar°(Ag)
Silver in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Cu

Ag

Au
palladiumsilvercadmium
kJ/mol
Heat of vaporisation254 kJ/mol
Molar heat capacity25.350 J/(mol·K)
Vapour pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1283 1413 1575 1782 2055 2433
Atomic properties
5000 BC
Symbol"Ag": from Latin argentum
Isotopes of silver
Main isotopes[7] Decay
abun­dance half-life (t1/2) mode pro­duct
105Ag synth 41.3 d ε
105Pd
γ
106mAg synth 8.28 d ε
106Pd
γ
107Ag 51.8%
stable
108mAg synth 439 y ε
108Pd
IT
108Ag
γ
109Ag 48.2% stable
110m2Ag synth 249.86 d
β
110Cd
γ
111Ag synth 7.43 d β
111Cd
γ
 Category: Silver
| references

Silver is a

reflectivity of any metal.[8] The metal is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining
.

Silver has long been valued as a

per-mille basis; a 94%-pure alloy is described as "0.940 fine". As one of the seven metals of antiquity
, silver has had an enduring role in most human cultures.

Other than in

medical instruments
.

Characteristics

Silver is extremely ductile, and can be drawn into a wire one atom wide.[11]

Silver is similar in its physical and chemical properties to its two vertical neighbours in

d-block which has a completely consistent set of electron configurations.[12] This distinctive electron configuration, with a single electron in the highest occupied s subshell over a filled d subshell, accounts for many of the singular properties of metallic silver.[13]

Silver is a relatively soft and extremely

Silver has a brilliant, white, metallic luster that can take a high

reflectivity than aluminium at all wavelengths longer than ~450 nm.[17] At wavelengths shorter than 450 nm, silver's reflectivity is inferior to that of aluminium and drops to zero near 310 nm.[18]

Very high electrical and thermal conductivity are common to the elements in group 11, because their single s electron is free and does not interact with the filled d subshell, as such interactions (which occur in the preceding transition metals) lower electron mobility.

electromagnets in calutrons for enriching uranium, mainly because of the wartime shortage of copper.[20][21][22]

Silver readily forms

Isotopes

Naturally occurring silver is composed of two stable

u;[23][24] this value is very important because of the importance of silver compounds, particularly halides, in gravimetric analysis.[23] Both isotopes of silver are produced in stars via the s-process (slow neutron capture), as well as in supernovas via the r-process (rapid neutron capture).[25]

Twenty-eight

radioactive isotopes have half-lives of less than an hour, and the majority of these have half-lives of less than three minutes.[26]

Isotopes of silver range in

decay mode before the most abundant stable isotope, 107Ag, is electron capture and the primary mode after is beta decay. The primary decay products before 107Ag are palladium (element 46) isotopes, and the primary products after are cadmium (element 48) isotopes.[26]

The palladium

Radiogenic 107Ag was first discovered in the Santa Clara meteorite in 1978.[28] 107Pd–107Ag correlations observed in bodies that have clearly been melted since the accretion of the Solar System must reflect the presence of unstable nuclides in the early Solar System.[29]

Chemistry

Oxidation states and stereochemistries of silver[30]
Oxidation
state
Coordination
number
Stereochemistry Representative
compound
0 (d10s1) 3 Planar Ag(CO)3
1 (d10) 2 Linear [Ag(CN)2]
3 Trigonal planar AgI(PEt2Ar)2
4 Tetrahedral [Ag(diars)2]+
6 Octahedral AgF, AgCl, AgBr
2 (d9) 4 Square planar [Ag(py)4]2+
3 (d8) 4 Square planar [AgF4]
6 Octahedral [AgF6]3−

Silver is a rather unreactive metal. This is because its filled 4d shell is not very effective in shielding the electrostatic forces of attraction from the nucleus to the outermost 5s electron, and hence silver is near the bottom of the

electrochemical series (E0(Ag+/Ag) = +0.799 V).[13] In group 11, silver has the lowest first ionization energy (showing the instability of the 5s orbital), but has higher second and third ionization energies than copper and gold (showing the stability of the 4d orbitals), so that the chemistry of silver is predominantly that of the +1 oxidation state, reflecting the increasingly limited range of oxidation states along the transition series as the d-orbitals fill and stabilize.[31] Unlike copper, for which the larger hydration energy of Cu2+ as compared to Cu+ is the reason why the former is the more stable in aqueous solution and solids despite lacking the stable filled d-subshell of the latter, with silver this effect is swamped by its larger second ionisation energy. Hence, Ag+ is the stable species in aqueous solution and solids, with Ag2+ being much less stable as it oxidizes water.[31]

Most silver compounds have significant

organometallic compounds, forming linear complexes showing very low coordination numbers like 2, and forming an amphoteric oxide[33] as well as Zintl phases like the post-transition metals.[34] Unlike the preceding transition metals, the +1 oxidation state of silver is stable even in the absence of π-acceptor ligands.[31]

Silver does not react with air, even at red heat, and thus was considered by

alchemists as a noble metal, along with gold. Its reactivity is intermediate between that of copper (which forms copper(I) oxide when heated in air to red heat) and gold. Like copper, silver reacts with sulfur and its compounds; in their presence, silver tarnishes in air to form the black silver sulfide (copper forms the green sulfate instead, while gold does not react). While silver is not attacked by non-oxidizing acids, the metal dissolves readily in hot concentrated sulfuric acid, as well as dilute or concentrated nitric acid. In the presence of air, and especially in the presence of hydrogen peroxide, silver dissolves readily in aqueous solutions of cyanide.[30]

The three main forms of deterioration in historical silver artifacts are tarnishing, formation of silver chloride due to long-term immersion in salt water, as well as reaction with nitrate ions or oxygen. Fresh silver chloride is pale yellow, becoming purplish on exposure to light; it projects slightly from the surface of the artifact or coin. The precipitation of copper in ancient silver can be used to date artifacts, as copper is nearly always a constituent of silver alloys.[35]

Silver metal is attacked by strong oxidizers such as potassium permanganate (KMnO
4
) and potassium dichromate (K
2
Cr
2
O
7
), and in the presence of potassium bromide (KBr). These compounds are used in photography to bleach silver images, converting them to silver bromide that can either be fixed with thiosulfate or redeveloped to intensify the original image. Silver forms cyanide complexes (silver cyanide) that are soluble in water in the presence of an excess of cyanide ions. Silver cyanide solutions are used in electroplating of silver.[36]

The common

peroxodisulfate, and some silver(III) compounds react with atmospheric moisture and attack glass.[38] Indeed, silver(III) fluoride is usually obtained by reacting silver or silver monofluoride with the strongest known oxidizing agent, krypton difluoride.[39]

Compounds

Oxides and chalcogenides

Silver(I) sulfide

Silver and gold have rather low

peroxodisulfate to black AgO, a mixed silver(I,III) oxide of formula AgIAgIIIO2. Some other mixed oxides with silver in non-integral oxidation states, namely Ag2O3 and Ag3O4, are also known, as is Ag3O which behaves as a metallic conductor.[40]

Halides

The three common silver halide precipitates: from left to right, silver iodide, silver bromide, and silver chloride

The only known dihalide of silver is the difluoride, AgF2, which can be obtained from the elements under heat. A strong yet thermally stable and therefore safe fluorinating agent, silver(II) fluoride is often used to synthesize hydrofluorocarbons.[41]

In stark contrast to this, all four silver(I) halides are known. The

photosensitive (though the monofluoride is so only to ultraviolet light), especially the bromide and iodide which photodecompose to silver metal, and thus were used in traditional photography.[41] The reaction involved is:[42]

X + → X + e (excitation of the halide ion, which gives up its extra electron into the conduction band)
Ag+ + e → Ag (liberation of a silver ion, which gains an electron to become a silver atom)

The process is not reversible because the silver atom liberated is typically found at a

crystal defect or an impurity site, so that the electron's energy is lowered enough that it is "trapped".[42]

Other inorganic compounds

Silver crystals forming on a copper surface in a silver nitrate solution. Video by Maxim Bilovitskiy.
Crystals of silver nitrate

White

deprotection and oxidations. Ag+ binds alkenes reversibly, and silver nitrate has been used to separate mixtures of alkenes by selective absorption. The resulting adduct can be decomposed with ammonia to release the free alkene.[45]

Yellow silver carbonate, Ag2CO3 can be easily prepared by reacting aqueous solutions of sodium carbonate with a deficiency of silver nitrate.[46] Its principal use is for the production of silver powder for use in microelectronics. It is reduced with formaldehyde, producing silver free of alkali metals:[47]

Ag2CO3 + CH2O → 2 Ag + 2 CO2 + H2

Silver carbonate is also used as a

alkyl bromides into alcohols.[46]

Silver fulminate, AgCNO, a powerful, touch-sensitive explosive used in percussion caps, is made by reaction of silver metal with nitric acid in the presence of ethanol. Other dangerously explosive silver compounds are silver azide, AgN3, formed by reaction of silver nitrate with sodium azide,[48] and silver acetylide, Ag2C2, formed when silver reacts with acetylene gas in ammonia solution.[31] In its most characteristic reaction, silver azide decomposes explosively, releasing nitrogen gas: given the photosensitivity of silver salts, this behaviour may be induced by shining a light on its crystals.[31]

2 AgN
3
(s) → 3 N
2
(g) + 2 Ag (s)

Coordination compounds

Structure of the diamminesilver(I) complex, [Ag(NH3)2]+

Silver complexes tend to be similar to those of its lighter homologue copper. Silver(III) complexes tend to be rare and very easily reduced to the more stable lower oxidation states, though they are slightly more stable than those of copper(III). For instance, the square planar periodate [Ag(IO5OH)2]5− and tellurate [Ag{TeO4(OH)2}2]5− complexes may be prepared by oxidising silver(I) with alkaline

peroxodisulfate. The yellow diamagnetic [AgF4] is much less stable, fuming in moist air and reacting with glass.[38]

Silver(II) complexes are more common. Like the valence isoelectronic copper(II) complexes, they are usually square planar and paramagnetic, which is increased by the greater field splitting for 4d electrons than for 3d electrons. Aqueous Ag2+, produced by oxidation of Ag+ by ozone, is a very strong oxidising agent, even in acidic solutions: it is stabilized in phosphoric acid due to complex formation. Peroxodisulfate oxidation is generally necessary to give the more stable complexes with heterocyclic amines, such as [Ag(py)4]2+ and [Ag(bipy)2]2+: these are stable provided the counterion cannot reduce the silver back to the +1 oxidation state. [AgF4]2− is also known in its violet barium salt, as are some silver(II) complexes with N- or O-donor ligands such as pyridine carboxylates.[49]

By far the most important oxidation state for silver in complexes is +1. The Ag+ cation is diamagnetic, like its homologues Cu+ and Au+, as all three have closed-shell electron configurations with no unpaired electrons: its complexes are colourless provided the ligands are not too easily polarized such as I. Ag+ forms salts with most anions, but it is reluctant to coordinate to oxygen and thus most of these salts are insoluble in water: the exceptions are the nitrate, perchlorate, and fluoride. The tetracoordinate tetrahedral aqueous ion [Ag(H2O)4]+ is known, but the characteristic geometry for the Ag+ cation is 2-coordinate linear. For example, silver chloride dissolves readily in excess aqueous ammonia to form [Ag(NH3)2]+; silver salts are dissolved in photography due to the formation of the thiosulfate complex [Ag(S2O3)2]3−; and

diarsine complexes [Ag(L–L)2]+.[50]

Organometallic

Under standard conditions, silver does not form simple carbonyls, due to the weakness of the Ag–C bond. A few are known at very low temperatures around 6–15 K, such as the green, planar paramagnetic Ag(CO)3, which dimerizes at 25–30 K, probably by forming Ag–Ag bonds. Additionally, the silver carbonyl [Ag(CO)] [B(OTeF5)4] is known. Polymeric AgLX complexes with alkenes and alkynes are known, but their bonds are thermodynamically weaker than even those of the platinum complexes (though they are formed more readily than those of the analogous gold complexes): they are also quite unsymmetrical, showing the weak π bonding in group 11. Ag–C σ bonds may also be formed by silver(I), like copper(I) and gold(I), but the simple alkyls and aryls of silver(I) are even less stable than those of copper(I) (which tend to explode under ambient conditions). For example, poor thermal stability is reflected in the relative decomposition temperatures of AgMe (−50 °C) and CuMe (−15 °C) as well as those of PhAg (74 °C) and PhCu (100 °C).[51]

The C–Ag bond is stabilized by

chlorido(dimethyl sulfide)gold(I):[54]

Intermetallic

Different colors of silver–copper–gold alloys

Silver forms

eutectic mixture is used in vacuum brazing. The two metals are completely miscible as liquids but not as solids; their importance in industry comes from the fact that their properties tend to be suitable over a wide range of variation in silver and copper concentration, although most useful alloys tend to be richer in silver than the eutectic mixture (71.9% silver and 28.1% copper by weight, and 60.1% silver and 28.1% copper by atom).[55]

Most other binary alloys are of little use: for example, silver–gold alloys are too soft and silver–cadmium alloys too toxic. Ternary alloys have much greater importance: dental amalgams are usually silver–tin–mercury alloys, silver–copper–gold alloys are very important in jewellery (usually on the gold-rich side) and have a vast range of hardnesses and colours, silver–copper–zinc alloys are useful as low-melting brazing alloys, and silver–cadmium–indium (involving three adjacent elements on the periodic table) is useful in nuclear reactors because of its high thermal neutron capture cross-section, good conduction of heat, mechanical stability, and resistance to corrosion in hot water.[55]

Etymology

The word silver appears in

Paleo-Hispanic origin, pointing to the Basque form zilharr as an evidence.[58]

The chemical symbol Ag is from the

Proto-Indo-European root *h₂erǵ- (formerly reconstructed as *arǵ-), meaning 'white' or 'shining'. This was the usual Proto-Indo-European word for the metal, whose reflexes are missing in Germanic and Balto-Slavic.[57]

History

Silver vase, c. 2400 BC

Silver was known in prehistoric times:[59] the three metals of group 11, copper, silver, and gold, occur in the elemental form in nature and were probably used as the first primitive forms of money as opposed to simple bartering.[60] However, unlike copper, silver did not lead to the growth of metallurgy on account of its low structural strength, and was more often used ornamentally or as money.[61] Since silver is more reactive than gold, supplies of native silver were much more limited than those of gold.[60] For example, silver was more expensive than gold in Egypt until around the fifteenth century BC:[62] the Egyptians are thought to have separated gold from silver by heating the metals with salt, and then reducing the silver chloride produced to the metal.[63]

The situation changed with the discovery of

Chalcolithic period,[64]
these techniques did not spread widely until later, when it spread throughout the region and beyond.[62] The origins of silver production in India, China, and Japan were almost certainly equally ancient, but are not well-documented due to their great age.[63]

Silver mining and processing in Kutná Hora, Bohemia, 1490s

When the

discovery of the New World. Reaching a peak production of 200 tonnes per year, an estimated silver stock of 10,000 tonnes circulated in the Roman economy in the middle of the second century AD, five to ten times larger than the combined amount of silver available to medieval Europe and the Abbasid Caliphate around AD 800.[66][67] The Romans also recorded the extraction of silver in central and northern Europe in the same time period. This production came to a nearly complete halt with the fall of the Roman Empire, not to resume until the time of Charlemagne: by then, tens of thousands of tonnes of silver had already been extracted.[63]

Central Europe became the centre of silver production during the

Steiermark, Schwaz, and the southern Black Forest. Most of these ores were quite rich in silver and could simply be separated by hand from the remaining rock and then smelted; some deposits of native silver were also encountered. Many of these mines were soon exhausted, but a few of them remained active until the Industrial Revolution, before which the world production of silver was around a meagre 50 tonnes per year.[63] In the Americas, high temperature silver-lead cupellation technology was developed by pre-Inca civilizations as early as AD 60–120; silver deposits in India, China, Japan, and pre-Columbian America continued to be mined during this time.[63][68]

With the discovery of America and the plundering of silver by the Spanish conquistadors, Central and South America became the dominant producers of silver until around the beginning of the 18th century, particularly Peru, Bolivia, Chile, and Argentina:[63] the last of these countries later took its name from that of the metal that composed so much of its mineral wealth.[65] The silver trade gave way to a global network of exchange. As one historian put it, silver "went round the world and made the world go round."[69] Much of this silver ended up in the hands of the Chinese. A Portuguese merchant in 1621 noted that silver "wanders throughout all the world... before flocking to China, where it remains as if at its natural center."[70] Still, much of it went to Spain, allowing Spanish rulers to pursue military and political ambitions in both Europe and the Americas. "New World mines", concluded several historians, "supported the Spanish empire."[71]

In the 19th century, primary production of silver moved to North America, particularly Canada, Mexico, and Nevada in the United States: some secondary production from lead and zinc ores also took place in Europe, and deposits in Siberia and the Russian Far East as well as in Australia were mined.[63] Poland emerged as an important producer during the 1970s after the discovery of copper deposits that were rich in silver, before the centre of production returned to the Americas the following decade. Today, Peru and Mexico are still among the primary silver producers, but the distribution of silver production around the world is quite balanced and about one-fifth of the silver supply comes from recycling instead of new production.[63]

Symbolic role

16th-century fresco painting of Judas being paid thirty pieces of silver for his betrayal of Jesus

Silver plays a certain role in mythology and has found various usage as a metaphor and in folklore. The Greek poet

ages of man named after metals like gold, silver, bronze and iron to account for successive ages of humanity.[72] Ovid's Metamorphoses
contains another retelling of the story, containing an illustration of silver's metaphorical use of signifying the second-best in a series, better than bronze but worse than gold:

But when good Saturn, banish'd from above,
Was driv'n to Hell, the world was under

Jove
.
Succeeding times a silver age behold,
Excelling brass, but more excell'd by gold.

— Ovid, Metamorphoses, Book I, trans. John Dryden

In folklore, silver was commonly thought to have mystic powers: for example, a

witch, or other monsters.[73][74][75] From this the idiom of a silver bullet developed into figuratively referring to any simple solution with very high effectiveness or almost miraculous results, as in the widely discussed software engineering paper "No Silver Bullet."[76] Other powers attributed to silver include detection of poison and facilitation of passage into the mythical realm of fairies.[75]

Silver production has also inspired figurative language. Clear references to cupellation occur throughout the Old Testament of the Bible, such as in Jeremiah's rebuke to Judah: "The bellows are burned, the lead is consumed of the fire; the founder melteth in vain: for the wicked are not plucked away. Reprobate silver shall men call them, because the Lord hath rejected them." (Jeremiah 6:19–20) Jeremiah was also aware of sheet silver, exemplifying the malleability and ductility of the metal: "Silver spread into plates is brought from Tarshish, and gold from Uphaz, the work of the workman, and of the hands of the founder: blue and purple is their clothing: they are all the work of cunning men." (Jeremiah 10:9)[62]

Silver also has more negative cultural meanings: the idiom thirty pieces of silver, referring to a reward for betrayal, references the bribe Judas Iscariot is said in the New Testament to have taken from Jewish leaders in Jerusalem to turn Jesus of Nazareth over to soldiers of the high priest Caiaphas.[77] Ethically, silver also symbolizes greed and degradation of consciousness; this is the negative aspect, the perverting of its value.[78]

Occurrence and production

World production of silver

The abundance of silver in the Earth's crust is 0.08 

Tertiary period vulcanism.[80]

The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from

Penasquito (Mexico).[81] Top near-term mine development projects through 2015 are Pascua Lama (Chile), Navidad (Argentina), Jaunicipio (Mexico), Malku Khota (Bolivia),[82] and Hackett River (Canada).[81] In Central Asia, Tajikistan is known to have some of the largest silver deposits in the world.[83]

Silver is usually found in nature combined with other metals, or in minerals that contain silver compounds, generally in the form of

sulfides such as galena (lead sulfide) or cerussite (lead carbonate). So the primary production of silver requires the smelting and then cupellation of argentiferous lead ores, a historically important process.[84] Lead melts at 327 °C, lead oxide at 888 °C and silver melts at 960 °C. To separate the silver, the alloy is melted again at the high temperature of 960 °C to 1000 °C in an oxidizing environment. The lead oxidises to lead monoxide, then known as litharge, which captures the oxygen from the other metals present. The liquid lead oxide is removed or absorbed by capillary action into the hearth linings.[85][86][87]

Ag(s) + 2Pb(s) + O
2
(g) → 2PbO(absorbed) + Ag(l)

Today, silver metal is primarily produced instead as a secondary byproduct of

sulfuric acid and heating with lime or silica flux, before the silver is purified to over 99.9% purity via electrolysis in nitrate solution.[79]

Commercial-grade fine silver is at least 99.9% pure, and purities greater than 99.999% are available. In 2022, Mexico was the top producer of silver (6,300 tonnes or 24.2% of the world's total of 26,000 t), followed by China (3,600 t) and Peru (3,100 t).[88]

In marine environments

Silver concentration is low in seawater (pmol/L). Levels vary by depth and between water bodies. Dissolved silver concentrations range from 0.3 pmol/L in coastal surface waters to 22.8 pmol/L in pelagic deep waters.[89] Analyzing the presence and dynamics of silver in marine environments is difficult due to these particularly low concentrations and complex interactions in the environment.[90] Although a rare trace metal, concentrations are greatly impacted by fluvial, aeolian, atmospheric, and upwelling inputs, as well as anthropogenic inputs via discharge, waste disposal, and emissions from industrial companies.[91][92] Other internal processes such as decomposition of organic matter may be a source of dissolved silver in deeper waters, which feeds into some surface waters through upwelling and vertical mixing.[92]

In the Atlantic and Pacific, silver concentrations are minimal at the surface but rise in deeper waters.[93] Silver is taken up by plankton in the photic zone, remobilized with depth, and enriched in deep waters. Silver is transported from the Atlantic to the other oceanic water masses.[91] In North Pacific waters, silver is remobilized at a slower rate and increasingly enriched compared to deep Atlantic waters. Silver has increasing concentrations that follow the major oceanic conveyor belt that cycles water and nutrients from the North Atlantic to the South Atlantic to the North Pacific.[94]

There is not an extensive amount of data focused on how marine life is affected by silver despite the likely deleterious effects it could have on organisms through bioaccumulation, association with particulate matters, and sorption.[89] Not until about 1984 did scientists begin to understand the chemical characteristics of silver and the potential toxicity. In fact, mercury is the only other trace metal that surpasses the toxic effects of silver; however, the full extent of silver toxicity is not expected in oceanic conditions because of its ability to transfer into nonreactive biological compounds.[95]

In one study, the presence of excess ionic silver and silver nanoparticles caused bioaccumulation effects on zebrafish organs and altered the chemical pathways within their gills.[96] In addition, very early experimental studies demonstrated how the toxic effects of silver fluctuate with salinity and other parameters, as well as between life stages and different species such as finfish, molluscs, and crustaceans.[97] Another study found raised concentrations of silver in the muscles and liver of dolphins and whales, indicating pollution of this metal within recent decades. Silver is not an easy metal for an organism to eliminate and elevated concentrations can cause death.[98]

Monetary use

A 2004 American Silver Eagle bullion coin, minted in .999 fine silver

The earliest known coins were minted in the kingdom of Lydia in Asia Minor around 600 BC.[99] The coins of Lydia were made of electrum, which is a naturally occurring alloy of gold and silver, that was available within the territory of Lydia.[99] Since that time, silver standards, in which the standard economic unit of account is a fixed weight of silver, have been widespread throughout the world until the 20th century. Notable silver coins through the centuries include the Greek drachma,[100] the Roman denarius,[101] the Islamic dirham,[102] the karshapana from ancient India and rupee from the time of the Mughal Empire (grouped with copper and gold coins to create a trimetallic standard),[103] and the Spanish dollar.[104]

The ratio between the amount of silver used for coinage and that used for other purposes has fluctuated greatly over time; for example, in wartime, more silver tends to have been used for coinage to finance the war.[105]

Today, silver bullion has the ISO 4217 currency code XAG, one of only four precious metals to have one (the others being palladium, platinum, and gold).[106] Silver coins are produced from cast rods or ingots, rolled to the correct thickness, heat-treated, and then used to cut blanks from. These blanks are then milled and minted in a coining press; modern coining presses can produce 8000 silver coins per hour.[105]

Price

Price of silver 1968–2022

Silver prices are normally quoted in troy ounces. One troy ounce is equal to 31.1034768 grams. The London silver fix is published every working day at noon London time.[107] This price is determined by several major international banks and is used by London bullion market members for trading that day. Prices are most commonly shown as the United States dollar (USD), the Pound sterling (GBP), and the Euro (EUR).

Applications

Jewellery and silverware

Embossed silver sarcophagus of Saint Stanislaus in the Wawel Cathedral was created in main centers of the 17th century European silversmitheryAugsburg and Gdańsk[108]
17th-century silverware

The major use of silver besides coinage throughout most of history was in the manufacture of jewellery and other general-use items, and this continues to be a major use today. Examples include table silver for cutlery, for which silver is highly suited due to its antibacterial properties. Western concert flutes are usually plated with or made out of sterling silver;[109] in fact, most silverware is only silver-plated rather than made out of pure silver; the silver is normally put in place by electroplating. Silver-plated glass (as opposed to metal) is used for mirrors, vacuum flasks, and Christmas tree decorations.[110]

Because pure silver is very soft, most silver used for these purposes is alloyed with copper, with finenesses of 925/1000, 835/1000, and 800/1000 being common. One drawback is the easy tarnishing of silver in the presence of hydrogen sulfide and its derivatives. Including precious metals such as palladium, platinum, and gold gives resistance to tarnishing but is quite costly; base metals like zinc, cadmium, silicon, and germanium do not totally prevent corrosion and tend to affect the lustre and colour of the alloy. Electrolytically refined pure silver plating is effective at increasing resistance to tarnishing. The usual solutions for restoring the lustre of tarnished silver are dipping baths that reduce the silver sulfide surface to metallic silver, and cleaning off the layer of tarnish with a paste; the latter approach also has the welcome side effect of polishing the silver concurrently.[109]

Medicine

In medicine, silver is incorporated into wound dressings and used as an antibiotic coating in medical devices. Wound dressings containing

dental caries (cavities) and relieve dentinal hypersensitivity.[116]

Electronics

Silver is very important in electronics for conductors and electrodes on account of its high electrical conductivity even when tarnished. Bulk silver and silver foils were used to make vacuum tubes, and continue to be used today in the manufacture of semiconductor devices, circuits, and their components. For example, silver is used in high quality connectors for

RFID antennas are made with silver paints,[12][117] Powdered silver and its alloys are used in paste preparations for conductor layers and electrodes, ceramic capacitors, and other ceramic components.[118]

Brazing alloys

Silver-containing brazing alloys are used for brazing metallic materials, mostly cobalt, nickel, and copper-based alloys, tool steels, and precious metals. The basic components are silver and copper, with other elements selected according to the specific application desired: examples include zinc, tin, cadmium, palladium, manganese, and phosphorus. Silver provides increased workability and corrosion resistance during usage.[119]

Chemical equipment

Silver is useful in the manufacture of chemical equipment on account of its low chemical reactivity, high thermal conductivity, and being easily workable. Silver crucibles (alloyed with 0.15% nickel to avoid recrystallisation of the metal at red heat) are used for carrying out alkaline fusion. Copper and silver are also used when doing chemistry with fluorine. Equipment made to work at high temperatures is often silver-plated. Silver and its alloys with gold are used as wire or ring seals for oxygen compressors and vacuum equipment.[120]

Catalysis

Silver metal is a good catalyst for

glycol yields glyoxal and ethanol yields acetaldehyde, while organic amines are dehydrated to nitriles.[120]

Photography

Before the advent of digital photography, which is now dominant, the photosensitivity of silver halides was exploited for use in traditional film photography. The photosensitive emulsion used in black-and-white photography is a suspension of silver halide crystals in gelatin, possibly mixed in with some noble metal compounds for improved photosensitivity, developing, and tuning[clarify].

Colour photography requires the addition of special dye components and sensitisers, so that the initial black-and-white silver image couples with a different dye component. The original silver images are bleached off and the silver is then recovered and recycled. Silver nitrate is the starting material in all cases.[121]

The market for silver nitrate and silver halides for photography has rapidly declined with the rise of digital cameras. From the peak global demand for photographic silver in 1999 (267,000,000

troy ounces or 8,304.6 tonnes) the market contracted almost 70% by 2013.[122]

Nanoparticles

Nanosilver particles, between 10 and 100 nanometres in size, are used in many applications. They are used in conductive inks for printed electronics, and have a much lower melting point than larger silver particles of micrometre size.[citation needed] They are also used medicinally in antibacterials and antifungals in much the same way as larger silver particles.[114] In addition, according to the European Union Observatory for Nanomaterials (EUON), silver nanoparticles are used both in pigments, as well as cosmetics.[123][124]

Miscellanea

South Asian sweets
, with some pieces covered with shiny silver vark

Pure silver metal is used as a food colouring. It has the E174 designation and is approved in the European Union.[125] Traditional Indian and Pakistani dishes sometimes include decorative silver foil known as vark,[126] and in various other cultures, silver dragée are used to decorate cakes, cookies, and other dessert items.[127]

Colloidal silver is similarly used to disinfect closed swimming pools; while it has the advantage of not giving off a smell like hypochlorite treatments do, colloidal silver is not effective enough for more contaminated open swimming pools. Small silver iodide crystals are used in cloud seeding to cause rain.[114]

The Texas Legislature designated silver the official precious metal of Texas in 2007.[128]

Precautions

Silver
Hazards
GHS labelling:
GHS09: Environmental hazard
Warning
H410
P273, P391, P501[129]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0

Silver compounds have low toxicity compared to those of most other

colloidal silver have been observed to develop localised tumours. Parenterally admistered colloidal silver causes acute silver poisoning.[130] Some waterborne species are particularly sensitive to silver salts and those of the other precious metals; in most situations, however, silver does not pose serious environmental hazards.[130]

In large doses, silver and compounds containing it can be absorbed into the circulatory system and become deposited in various body tissues, leading to argyria, which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Argyria is rare, and so far as is known, does not otherwise harm a person's health, though it is disfiguring and usually permanent. Mild forms of argyria are sometimes mistaken for cyanosis, a blue tint on skin, caused by lack of oxygen.[130][12]

Metallic silver, like copper, is an antibacterial agent, which was known to the ancients and first scientifically investigated and named the oligodynamic effect by Carl Nägeli. Silver ions damage the metabolism of bacteria even at such low concentrations as 0.01–0.1 milligrams per litre; metallic silver has a similar effect due to the formation of silver oxide. This effect is lost in the presence of sulfur due to the extreme insolubility of silver sulfide.[130]

Some silver compounds are very explosive, such as the nitrogen compounds silver azide, silver amide, and silver fulminate, as well as silver acetylide, silver oxalate, and silver(II) oxide. They can explode on heating, force, drying, illumination, or sometimes spontaneously. To avoid the formation of such compounds, ammonia and acetylene should be kept away from silver equipment. Salts of silver with strongly oxidising acids such as silver chlorate and silver nitrate can explode on contact with materials that can be readily oxidised, such as organic compounds, sulfur and soot.[130]

See also

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External links

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