SILVER

Silver is one of the earliest known metals. 
Silver has no known physiologic or biologic function, though colloidal silver is widely sold in health food stores. 
Silver has high thermal and electrical conductivity and resists oxidation in air that is devoid of hydrogen sulfide.

CAS:    7440-22-4
MF:    Ag
MW:    107.87
EINECS:    231-131-3

Synonyms
Silver conductive coating, Sheet resistance 0.015 ohms/square in./mil (25μm);Silver, Hard;Silver nanoparticles, 10nm, supplied in 2mM citrate, conjugated to Protein A;Silver shot, 1 to 3mm (0.04 to 0.1 in.);Silver wire, 2.0mm (0.08 in.) dia., Annealed, Temper: soft;Silver wire, 0.05mm (0.002 in.) dia.;Silver wire gauze;Silver foil, 0.05mm (0.002 in.) thick, Annealed, Temper: soft

A transition metal that occurs native and as the sulfide (Ag2S) and chloride (AgCl). 
Silver is extracted as a by-product in refining copper and lead ores.
Silver darkens in air due to the formation of silver sulfide. 
Silver is used in coinage alloys, tableware, and jewelry. 
Silver compounds are used in photography. 
Symbol: Ag; m.p. 961.93°C; b.p. 2212°C; r.d. 10.5 (20°C); p.n. 47; r.a.m. 107.8682.
Symbol Ag. 
A white lustroussoft metallic transition element; a.n.47; r.a.m. 107.87; r.d. 10.5; m.p.961.93°C; b.p. 2212°C. 

Silver occurs as theelement and as the minerals argentite(Ag2S) and horn silver (AgCl). 
Silver isalso present in ores of lead and copper,and is extracted as a by-productof smelting and refining these metals.
The element is used in jewellery,tableware, etc., and silver compoundsare used in photography.
Chemically, silver is less reactivethan copper. 
A dark silver sulphideforms when silver tarnishes in air becauseof the presence of sulphurcompounds. 
Silver(I) ionic salts exist(e.g. AgNO3, AgCl) and there are anumber of silver(II) complexes.
Silver is a noble metal, extensively used in SERS, photocatalysis and solar cells. 
The surface of silver can be functionalized to attain specific properties such as biocompatibility and vapor selectivity of sensors.
Iodized silver foils and thin films find potential use as SERS-active metal substrates.
Cu substrates laminated with Ag foils, have compatible coefficient of thermal expansion (CTE), to be used for electronic packaging. 

Porous ZnO nanoplates deposited on silver foil with tunable hydrophobicity may be fabricated.
Silver is a chemical element; it has symbol Ag (from Latin argentum 'silver') and atomic number 47. 
A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal.
Silver 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 precious metal, commonly sold and marketed beside gold and platinum.
Silver metal is used in many bullion coins, sometimes alongside gold: while it is more abundant than gold, Silver is much less abundant as a native metal. 
Its purity is typically measured on 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. 
In terms of scarcity, silver is the most abundant of the big three precious metals, platinum, gold, and silver; among these, platinum is the rarest, with around 139 troy ounces of silver mined for every one of platinum.

Other than in currency and as an investment medium (coins and bullion), silver is used in solar panels, water filtration, jewellery, ornaments, high-value tableware and utensils (hence the term "silverware"), in electrical contacts and conductors, in specialised mirrors, window coatings, in catalysis of chemical reactions, as a colorant in stained glass, and in specialised confectionery. 
Silver's compounds are used in photographic and X-ray film. 
Dilute solutions of silver nitrate and other silver compounds are used as disinfectants and microbiocides (oligodynamic effect), added to bandages, wound-dressings, catheters, and other medical instruments.

Silver Chemical Properties
Melting point: 960 °C(lit.)
Boiling point: 2212 °C(lit.)
density: 1.135 g/mL at 25 °C
vapor density: 5.8 (vs air)
vapor pressure: 0.05 ( 20 °C)
refractive index: n20/D 1.333
Fp: 232 °F
storage temp.: 2-8°C
solubility: H2O: soluble
form: wool
color: Yellow
Specific Gravity: 10.49
PH: 0.5 (20°C in H2O)
Odor: Odorless
resistivity: 1-3 * 10^-5 Ω-cm (conductive paste) &_& 1.59 μΩ-cm, 20°C
Water Solubility: insoluble
Electrical Conductivity: 6.2× 107S/m
Thermal Conductivity: 430 W/(m·K)
Sensitive: Light Sensitive
Merck: 13,8577
Exposure limits: TLV-TWA (metal dusts and fumes) 0.1 mg/m3 (ACGIH), 0.01 mg/m3 (MSHA and OSHA), soluble compounds 0.01 mg/m3 (AIGIH).
Stability: Stable. Substances to be avoided include strong acids and strong bases, tartaric acid, oxalic acid. Blackened by contact with ozone, hydrogen sulfide, sulfur. Powder is highly flammable.
Cosmetics Ingredients Functions: SLIP MODIFIERDEODORANTSKIN CONDITIONING - MISCELLANEOUS ANTIMICROBIAL COLORANT
InChI: 1S/Ag
InChIKey: BQCADISMDOOEFD-UHFFFAOYSA-N
Modulus of Elasticity: 71.0 GPa, Typical of CP silver.
Poissons Ratio: 0.37
Shear Modulus: 26.0 GPa, calculated
Hardness, Vickers: 25, Annealed
CAS DataBase Reference: 7440-22-4(CAS DataBase Reference)
NIST Chemistry Reference: Silver(7440-22-4)
EPA Substance Registry System: Silver (7440-22-4)

The metal silver is described as a white, lustrous solid. 
In its pure form it has the highest thermal and electrical conductivity and lowest contact resistance of all metals. 
With the exception of gold, silver is the most malleable metal.
Silver (symbol Ag) is one of the basic elements present in the earth's crust. 
Silver is rare, but occurs naturally in the environment as a soft, “silver”-colored metal or as a white powdery compound (silver nitrate). 
Metallic silver and silver alloys are used to make jewelry, eating utensils, electronic equipment, and dental fillings. 
Nanoparticles of silver have been developed into meshes, bandages, and clothing as an antibacterial. 

Silver is used in photographic materials, electric and electronic products, brazing alloys and solders, electroplated and sterling ware, as a catalyst, and in coinage. 
Silver is alloyed with many other metals to improve strength and hardness and to achieve corrosion resistance.
Silver is a white lustrous metal that is extremely ductile and malleable. 
Silver does not oxidize in O2 by heating. 
Silver becomes Ag2O3 in O3 and black Ag2S3 in S2 and H2S. 
Silver is soluble in HNO3 and concentrated H2SO4. 
Silver is not soluble in alkali.

Elemental silver has a face-centered cubic crystal structure. 
Silver is a white metal, softer than copper and harder than gold.
When molten, silver is luminescent and occludes oxygen, but the oxygen is released upon solidification. 
As a conductor of heat and electricity, silver is superior to all other metals. 
Silver is soluble in HNO3 containing a trace of nitrate; soluble in hot 80% H2SO4; insoluble in HCl or acetic acid; tarnished by H2S, soluble sulfides and many sulfur-containing organic substances (e.g., proteins); not affected by air or H2O at ordinary temperatures, but at 200 C, a slight film of silver oxide is formed; not affected by alkalis, either in solution or fused. There are two stable, naturally occurring isotopes, 107Ag and 109Ag. 
In addition, there are reported to be 25 less stable isotopes, ranging in half-life from 5 seconds to 253 days.

Physical properties    
Silver is located in group 11 (IB) of period 5, between copper (Cu) above it in period 4 andgold (Au) below it in period 6. 
Thus, silver’s chemical and physical properties are somewhatsimilar to these two group 11 partners.
Silver is a soft, while, lustrous metal that can be worked by pounding, drawing througha die, rolling, and so forth. 
Silver is only slightly harder than gold. 
Silver is insoluble in water, but it will dissolve in hot concentrated acids. 
Freshly exposed silver has a mirror-like shine thatslowly darkens as a thin coat of tarnish forms on its surface (from the small amount ofnatural hydrogen sulfide in the air to form silver sulfide, AgS). 
Of all the metals, silver isthe best conductor of heat and electricity. 
This property determines much of its commercialusefulness. 
Its melting point is 961.93°C, its boiling point is 2,212°C, and its density is10.50 g/cm3.

Characteristics    
Silver is somewhat rare and is considered a commercially precious metal with many uses.
Pure silver is too soft and usually too expensive for many commercial uses, and thus it isalloyed with other metals, usually copper, making it not only stronger but also less expensive.
The purity of silver is expressed in the term “fitness,” which describes the amount of silverin the item. 
Fitness is just a multiple of 10 times the silver content in an item. 
For instance,sterling silver should be 93% (or at least 92.5%) pure silver and 7% copper or some othermetal. 
The fitness rating for pure silver is 1000. 

Therefore, the rating for sterling silver is 930,and most sliver jewelry is rated at about 800. 
This is another way of saying that most silverjewelry is about 20% copper or other less valuable metal.
Many people are fooled when they buy Mexican or German silver jewelry, thinking theyare purchasing a semiprecious metal.
These forms of “silver” jewelry go under many names,including Mexican silver, German silver, Afghan silver, Austrian silver, Brazilian silver, Nevadasilver, Sonara silver, Tyrol silver, Venetian silver, or just the name “silver” with quotes aroundit. 
None of these jewelry items, under these names or under any other names, contain anysilver. 
These metals are alloys of copper, nickel, and zinc.

History    
Silver is one of the oldest metals, known since ancient times. 
Silver is a precious metal worldwide, used in ornaments, coins, and utensils. 
The symbol Ag for this element is derived from the Latin word, argentum. 
Silver occurs in nature in native form, commonly associated with gold. 
Silver is found in most lead and copper ores. 
The principal mineral of silver is argentite, Ag2S [1332-04-3]. 
Some other silver minerals include pyrargyrite, Ag3SbS3 [15123-77-0]; proustite, Ag3AsS3 [15152-58-4]; polybasite, Ag16Sb2S11 [53810-31-4]; cerargyrite, AgCl [14358-96-4]; stephanite, Ag5SbS4 [1302-12-1]; and tetrahedrite, Cu3(AsSb)S3. 
Abundance of silver in the earth’s crust is estimated to be 0.075 mg/kg and its average concentration in sea water is 0.014 µg/L.

Uses    
Silver and its alloys and compounds have numerous applications. 
As a precious metal, silver is used in jewelry. 
Also, one of its alloys, sterling silver, containing 92.5 weight % silver and 7.5 weight % copper, is a jewelry item and is used in tableware and decorative pieces. 
The metal and its copper alloys are used in coins. 
Silver-copper brazing alloys and solders have many applications. 
They are used in automotive radiators, heat exchangers, electrical contacts, steam tubes, coins, and musical instruments.
Some other uses of silver metal include its applications as electrodes, catalysts, mirrors, and dental amalgam. 
Silver is used as a catalyst in oxidation-reductions involving conversions of alcohol to aldehydes, ethylene to ethylene oxide, and ethylene glycol to glyoxal.

Silver has a multitude of uses and practical applications both in its elemental metallic formand as a part of its many compounds. 
Its excellent electrical conductivity makes it ideal for usein electronic products, such a computer components and high-quality electronic equipment.
Silver would be an ideal metal for forming the wiring in homes and transmission lines, if it weremore abundant and less expensive.
Metallic silver has been used for centuries as a coinage metal in many countries. 
The amount of silver now used to make coins in the United States has been reduced drastically byalloying other metals such as copper, zinc, and nickel with silver.
Silver is used as a catalyst to speed up chemical reactions, in water purification, and inspecial high-performance batteries (cells). 

Silver's high reflectivity makes it ideal as a reflectivecoating for mirrors.
Several of its compounds were not only useful but even essential for the predigital photographicindustry. 
Several of the silver salts, such as silver nitrate, silver bromide, and silverchloride, are sensitive to light and, thus, when mixed with a gel-type coating on photographicfilm or paper, can be used to form light images. 
Most of the silver used in the United Statesis used in photography.
Photochromic (transition) eyeglasses that darken as they are exposed to sunlight have asmall amount of silver chloride imbedded in the glass that forms a thin layer of metallic silverthat darkens the lens when struck by sunlight. 
This photosensitive chemical activity is thenreversed when the eyeglasses are removed from the light. 
Silver reversal results from asmall amount of copper ions placed in the glass. 
This reaction is repeated each time the lensesare exposed to sunlight.

This malleable white metal is found as argentite (Ag2S) and horn silver (AgCl) or in lead and copper ore. 
Copper plates coated with a thin layer of elemental silver and fumed with iodine were used by Niépce and Daguerre. 
Aside from the heliograph and physautotype, silver halide compounds were the basis of all photographic processes used in the camera and most of the printing processes during the 19th century.
For coinage, most frequently alloyed with copper or gold; for manufacture of tableware, mirrors, jewelry, ornaments; for electroplating; for making vessels and apparatus used in manufacture of medicinal chemicals, in processing foods and beverages, in handling organic acids; as catalyst in hydrogenation and oxidation processes; as ingredient of dental alloys. 
Has been used for purification of drinking water because of toxicity to bacteria and lower forms of life. 
Some salts used in photography.
Silver is a precious metal, used in jewelryand ornaments Other applications includeits use in photography, electroplating, dentalalloys, high-capacity batteries, printed circuits,coins, and mirrors.
Silver is stable in air, and it is utilized in reflecting mirrors. 
The film vacuum evaporated on a quartz plate with the thickness of 2–55 nm shows the transmittance maximum at λ: 321.5 nm and works as a narrow band filter.

Jewellery and 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; 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.

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.

Medicine
Main article: Medical uses of silver
In medicine, silver is incorporated into wound dressings and used as an antibiotic coating in medical devices. 
Wound dressings containing silver sulfadiazine or silver nanomaterials are used to treat external infections. 
Silver is also used in some medical applications, such as urinary catheters (where tentative evidence indicates it reduces catheter-related urinary tract infections) and in endotracheal breathing tubes (where evidence suggests it reduces ventilator-associated pneumonia).
The silver ion is bioactive and in sufficient concentration readily kills bacteria in vitro. 
Silver ions interfere with enzymes in the bacteria that transport nutrients, form structures, and synthesise cell walls; these ions also bond with the bacteria's genetic material. 
Silver and silver nanoparticles are used as an antimicrobial in a variety of industrial, healthcare, and domestic application: for example, infusing clothing with nanosilver particles thus allows them to stay odourless for longer.
Bacteria can develop resistance to the antimicrobial action of silver.
Silver compounds are taken up by the body like mercury compounds, but lack the toxicity of the latter. 
Silver and its alloys are used in cranial surgery to replace bone, and silver–tin–mercury amalgams are used in dentistry.
Silver diammine fluoride, the fluoride salt of a coordination complex with the formula [Ag(NH3)2]F, is a topical medicament (drug) used to treat and prevent dental caries (cavities) and relieve dentinal hypersensitivity.

Electronics
See also: Copper-clad aluminium wire
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 RF, VHF, and higher frequencies, particularly in tuned circuits such as cavity filters where conductors cannot be scaled by more than 6%. 
Printed circuits and RFID antennas are made with silver paints, Powdered silver and its alloys are used in paste preparations for conductor layers and electrodes, ceramic capacitors, and other ceramic components.

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.

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.

Catalysis
Silver metal is a good catalyst for oxidation reactions; in fact it is somewhat too good for most purposes, as finely divided silver tends to result in complete oxidation of organic substances to carbon dioxide and water, and hence coarser-grained silver tends to be used instead. 
For instance, 15% silver supported on α-Al2O3 or silicates is a catalyst for the oxidation of ethylene to ethylene oxide at 230–270 °C. 
Dehydrogenation of methanol to formaldehyde is conducted at 600–720 °C over silver gauze or crystals as the catalyst, as is dehydrogenation of isopropanol to acetone. 
In the gas phase, glycol yields glyoxal and ethanol yields acetaldehyde, while organic amines are dehydrated to nitriles.

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 print toning.
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.
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.

Nanoparticles
Main article: Silver nanoparticle
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.
They are also used medicinally in antibacterials and antifungals in much the same way as larger silver particles.
In addition, according to the European Union Observatory for Nanomaterials (EUON), silver nanoparticles are used both in pigments, as well as cosmetics.

Pharmaceutical Applications    
The name silver is derived from the Saxon word ‘siloflur’, which has been subsequently transformed into the German word ‘Silabar’ followed by ‘Silber’ and the English word ‘silver’. Romans called the element ‘argentum’, and this is where the symbol Ag derives from.
Silver is widely distributed in nature. 
It can be found in its native form and in various ores such as argentite (Ag2S), which is the most important ore mineral for silver, and horn silver (AgCl). 
The principal sources of silver are copper, copper–nickel, gold, lead and lead–zinc ores, which can be mainly found in Peru, Mexico, China and Australia.
Silver has no known active biological role in the human body, and the levels of Ag+ within the body are below detection limits. 
The metal has been used for thousands of years mainly as ornamental metal or for coins.
Furthermore, silver has been used for medicinal purposes since 1000 BC. 
Silver was known that water would keep fresh if it was kept in a silver pitcher; for example, Alexander the Great (356–323 BC) used to transport his water supplies in silver pitchers during the Persian War. 
A piece of silver was also used, for example, to keep milk fresh, before any household refrigeration was developed. 
In 1869, Ravelin proved that silver in low doses acts as an antimicrobial. 
Around the same time, the Swiss botanist von Ngeli showed that already at very low concentration Ag+ can kill the green algae spirogyra in fresh water. 
This work inspired the gynaecologist Crede to recommended use of AgNO3 drops on new born children with conjunctivitis.

Production Methods    
Many processes are known for recovery of silver from its ores. 
These depend mostly on the nature of the mineral, its silver content, and recovery of other metals present in the ore. 
A few processes are briefly outlined below.
Silver is usually extracted from high-grade ores by three common processes that have been known for many years. 
These are amalgamation, leaching, and cyanidation. 
In one amalgamation process, ore is crushed and mixed with sodium chloride, copper sulfate, sulfuric acid, and mercury, and roasted in cast iron pots. 
The amalgam is separated and washed. 
Silver is separated from its amalgam by distillation of mercury.
In the cyanidation process the ore is crushed and roasted with sodium chloride and then treated with a solution of sodium cyanide. 
Silver forms a stable silver cyanide complex, [Ag(CN)2]–. Adding metallic zinc to this complex solution precipitates silver. 
Several leaching processes are known. 

One such process, known as the Patera process, developed in the mid 19th century, involves roasting ore with sodium chloride followed by leaching with sodium thiosulfate solution. 
Silver 834 SILVERis precipitated as silver sulfide, Ag2S, by adding sodium sulfide to the leachate. 
In the Clandot process, leaching is done with ferric chloride solution. 
Addition of zinc iodide precipitates silver iodide, AgI. 
AgI is reduced with zinc to obtain silver.
The above processes are applied for extraction of silver from high-grade ores.
However, with depletion of these ores, many processes were developed subsequently to extract silver from low-grade ores, especially lead, copper, and zinc ores that contain very small quantities of silver.
Low grade ores are concentrated by floatation. 
The concentrates are fed into smelters (copper, lead, and zinc smelters). 
The concentrates are subjected to various treatments before and after smelting including sintering, calcination, and leaching. 
Copper concentrates are calcined for removal of sulfur and smelted in a reverberatory furnace to convert into blister copper containing 99 wt% Cu. 
The blister copper is fire-refined and cast into anodes. 

The anodes are electrolytically refined in the presence of cathodes containing 99.9% copper. 
Insoluble anode sludges from electrolytic refining contain silver, gold, and platinum metals. 
Silver is recovered from the mud by treatment with sulfuric acid. 
Base metals dissolve in sulfuric acid leaving silver mixed with any gold present in the mud. Silver is separated from gold by electrolysis.
Lead and zinc concentrates can be treated in more or less the same manner as copper concentrates. 
Sintering lead concentrates removes sulfur and following that smelting with coke and flux in a blast furnace forms impure lead bullion. 
The lead bullion is drossed with air and sulfur and softened with molten bullion in the presence of air to remove most impurities other than silver and gold. 
Copper is recovered from the dross and zinc converts to its oxide and is recovered from blast furnace slag. 
The softened lead obtained above also contains some silver. 
The silver is recovered by the Parkes Process. 
The Parkes process involves adding zinc to molten lead to dissolve silver at temperatures above the melting point of zinc. 
On cooling, zinc-silver alloy solidifies, separating from the lead and rising to the top. 

The alloy is lifted off and zinc is separated from silver by distillation leaving behind metallic silver.
The unsoftened lead obtained after the softening operation contains silver in small but significant quantities. 
Such unsoftened lead is cast into anode and subjected to electrolytic refining. 
The anode mud that is formed adhering to these anodes is removed by scraping. 
Silver contains bismuth, silver, gold, and other impurity metals. 
Silver is obtained from this anode mud by methods similar to the extraction of anode mud from the copper refining process discussed earlier.
If the low–grade ore is a zinc mineral, then zinc concentrate obtained from the flotation process is calcined and leached with water to remove zinc. 
Silver and lead are left in leach residues. 
Residues are treated like lead concentrates and fed into lead smelters. 
Silver is recovered from this lead concentrate by various processes described above.

Health Hazard    
The acute toxicity of silver metal is low. 
The acute toxicity of soluble silver compounds depends on the counterion and must be evaluated case by case. 
For example, silver nitrate is strongly corrosive and can cause burns and permanent damage to the eyes and skin.
Chronic exposure to silver or silver salts can cause a local or generalized darkening of the mucous membranes, skin, and eyes known as argyria. 
The other chronic effects of silver compounds must be evaluated individually.