every cloud has a silver lining repair

8/2/2019 Every Cloud Has a Silver Lining Repair

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1.INTRODUCTION

Silver (Ag) is a shining white metal which occurs in nature as in ores and as a free metal. It is

an element in group 11 of transition metals in the periodic table with a mass number of 108

and atomic number of 47.

Silver is a rare but naturally occurring metal, often found deposited as a mineral ore in

association with other elements. The ores are smelted to extract silver and use for different

applications. Silver found to be the metal with highest electrical conductivity. This led the

use of silver in high-tech electric equipment. And its tensile strength can be improved with byforming alloys to suit for different application such as dental fillings and replacement for

some internal parts of our body.

With the developments in science and technology, more uses of silver has been discovered

which are around as. Pure silver is converted to other compounds and used to make

photographic film. It is utilized in electrical and electronic equipment including specialized

batteries. It is also practiced as a medicine for some diseases. For making control rods in

nuclear reactors silver rods are applied as it absorbs neutrons. In some chemical reaction it is

being used as catalyst. And its endless uses continue.

Silver forms both soluble and insoluble salts by reacting with other non-metals. Ions of silver

are formed by dissolving in water or leach from the soil. The global biogeochemical

movements of silver are characterized by releases to the atmosphere, water, and land by

natural and manmade sources, long-range transport of fine particles in the atmosphere, wet

and dry deposition, and sorption to soils and sediments. It is a mildly toxic element to our

health.

As silver has played an important role in the past, it has become a significantly material in

todays life and will continue to be a vital element for future generation.


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2.DISCOVERY OF SILVER.No one actually knows exactly who discovered the chemical element silver or when and

where it was discovered, but there is evidence that it was known to the ancients. Silver was

probably first discovered after gold and copper. Archaeologists have found silver objects

dating to about 3400 B.C. in Egypt. The earliest known large-size mines were those of

Cappadocia in eastern Anatolia. The best-known of the ancient mines were located at the

Laurium silver-lead deposit in Greece and were actively mined from 500 BC to AD 100.

About 2500 B.C. the Chaldeans used a mining process called "cupellation" to extract silver

from lead-silver ores. Today the most common silver ores found are argentite (Ag2S);cerargyrite, or "horn silver" (AgCl); proustite (3Ag2S As2S3); and pyrargyrite (Ag2S

Sb2S3).

A significant discovery of silver ore occurred in 1492, and from 1500 to 1800 Bolivia, Peru

and Mexico supplied 85% of the world's silver. Rapidly developing technology from 1876 to

1920 contributed to exploitation of new worldwide silver supplies from Australia, Central

America and Europe to Canada, the U.S. and Africa.

Today, Peru is the worlds biggest silver mining country. In 2008, global silver mine

production reached a record high value of 680.9 Moz due to the increase in production in

Bolivia, Russia and Peru. Other leading countries in silver mining are Mexico, China,

Australia and Chile. Due to its unique properties, demand of silver is increasing.


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3.PHYSICAL PROPERTIES SILVER3.1. Introduction

Silver is a soft white, lustrous metal that is extremely malleable, ductile, and has the

highest electrical and thermal conductivities of all metals. It is relatively a stable

element which does not react with moist air or dry oxygen and does not react readily

with organic acids and bases.

3.2. ConductivitySilver has the highest electrical conductivity of all the other metals. As a result it is

considered as futures interconnect material for ultra large scale integrated (ULSI)

circuit technology.

In integrated circuit technologies, with the increase in multilayer metallization the

performance limiting resistive and capacitive signal delays increase accordingly. To

solve this problem, a low resistive metal has to be used. Since silver has the lowest

resistivity of all the metal, it suit for the job.

Fig.3.1. Resistivity of pure metals


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The electrical resistivity of metal films usually decreases during an annealing

treatment. This is because surface morphology of thin film metal affects the electrical

resistivity and surface morphology changes during annealing.

In the thin metal film, rough surfaces occur at the initial stage of agglomeration

process which begins at the grain boundary. During the initial stage of agglomeration

more source of conducting electrons are provided through the thin films thus

decreasing electrical resistivity. Void and island formation occurs in the final stage

which cause the reduction of conducting area thus prevent further decrease ofresistivity of silver.

Electron migration another fear identified as a primary failure mode of interconnects

lines used in semiconductor-integrated circuits. Silver as the most conductive metal,

has a better electromigration resistance when compare with aluminum but need to be

further improved since copper has a better electronmigration resistance.

Fig.3.2. Resistivity () of a 50-nm-thick silver film independence on the annealing

temperature T.


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3.3. StrengthMost commercially used silver has a tensile strength of 170 MPa in annealed

condition and when it is 50% cold worked, tensile strength increases to 296 MPa.

Commercially pure silver has 74 GPa of modulus of elasticity.

3.3.1. Silver in AmalgamsAn important application of silvers strength is alloying with tin to form silver-tin

amalgams used for dental filling. When amalgam is used for dental filling, it is

subjected to compression. Therefore to choose the appropriate different

composition of amalgams is subjected to compression strength at different

temperature.

Composition and Homogenization of Silver-Tin Alloys

AlloyTin

Composition(%)

HomogenizationPhaseTemperature

(C)Time

(Days)A 4.00 852 1(hr) B 8.00 765 4

C 12.00 550 7 +D 16.00 672 3 E 20.00 624 4 +F 24.00 392 14 +G 26.85 392 14 H 30.85 204 10 +Sn

The most successful amalgam alloys are formed at 25-27 percent range of silver-tinsystem. Ag3Sn intermetallic compound occurs within this range containing silver,

73.15 weight percent, and tin, 26.83 weight percent.

Table 3.1: Different composition of silver-tin alloy and its homogenization with

phase.


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The results show that compressive strength increased with increase in trituration

time, until a maximum strength is obtained that was not changed by further

trituration. From this it can be considered that increased trituration increases bond

strength in amalgamation.

When the composite has and phases, it shows less strength than others. And if

and phases were combined in same alloy, the strength increased with the addition

of . The phase alloy resulted in the strongest amalgam, probably due to less

volume of matrix and greater bond strength.

Fig.3.3. Relationship of amalgam compressive strength to alloy composition.

=0.5 minute; =1.0 minute; =2.0 minutes; =3.0 minutes.


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3.4. Phase diagram (copper-silver system)In copper-silver system, three phase regions are found: , and liquid. The phase

is a solid solution rich in copper with silver as the absolute component and an FCC

crystal structure. The phase solid also has an FCC structure, but copper is thesolute. Pure copper and pure silver are also considered to be and phases,

respectively.

In this phase diagram, the solubility of each of these solid phases is limited. Any

temperature below lineBEG, only a limited concentration of silver will dissolve in

copper (for the phase), and similarly for copper in silver (for the phase). The

solubility for phase in the region labeled as CBA, increase with increase in

temperature up to a maximum point atB (8.0 wt% Ag at 779C) and decrease back

to zero at meting temperature of pure copper, pointA (1085C).

The line separating the region and + is termed as solvus line and the line

between and +L is termed as solidus line. Both these lines also exist for

Fig.3.4. coppersilver binary phases diagram.


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phase,HG and GF, respectively as shown in the figure and the maximum solubility

ofcopper occur at point G (8.8 wt% Cu at 779 C).

As silver is added to copper, the temperature at which the alloys become totally

liquid decreases along the liquidus lineAE; decreasing the melting temperature ofcopper with addition of silver. Introduction of copper also reduces the melting

temperature of silver at line the liquidus line FE. The point at these liquidus lines

meet is known as invariant point (E).

Upon cooling a liquid phase is transformed into the two solid and phases at the

temperature TE and the opposite reaction occurs upon heating. This is called

eutectic reaction.

Important properties of silver

Description Value Units

Melting point 962 C

Thermal conductivity 4.29 W/cm CCoefficient of thermal expansion 18.6 x 10-6 cm/cm C

Specific heat 0.237 J/g mol

Specific gravity 10.5

Elastic modulus 71 GPa

Tensile strength (annealed) 152 Mpa

Electrical resistivity (commercially pure) 1.59 -m

Density 10.5 g/cc


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4.CHEMICAL PROPERTIES OF CLOUD ANDSILVER

4.1. IntroductionClouds are condensed water vapor in air. But clouds are not an inert mixture.

Particles that facilitate cloud formation have various chemical compositions and

the atmospheric gases around the droplet also can modify its chemical

composition.

Silver is a transition metal. It has 47 protons and the electron configuration is

[Kr]4d105s1. The number of neutrons varies with different isotopes of silver. The

two isotopes of silver that exist are 107Ag and 109Ag. It exhibit three oxidation

states, Ag (I), Ag (II) and Ag (III) and most common ions found are Ag+ and

Ag2+.

It does not react with air or pure water in normal condition. Silver reacts with

halides and acids to form its salts. It also acts as a catalyst in some chemical

reactions.

4.2. Cloud FormationCloud is formed from the water vapor that evaporates from sea, river lakes and

other sources. These vapors condense and form droplets or ice crystals. Particles

that allow the clouds formation are called Cloud Condensation Nuclei (CCN),

which have various chemical compositions according to their origin (from

human or natural source). Since clouds are surrounded by atmospheric gases, it

can also affect the chemical composition of cloud.


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4.2.1. The particle inside the dropletThe water soluble fraction of an aerosol governs its capacity to grow into a

droplet. The chemical composition of the particles that act as CCN determines the

initial composition of the cloud droplet, as its soluble content dissolves in the

condense water.

4.2.2. The atmospheric gases around the dropletWhether a chemical species stay in the gas phase or is absorbed in the water

droplet is estimated by considering the Henrys law equilibrium: A (aq) = HA PA,

where A (aq) is the aqueous phase concentration (mol/L), PA is the partial pressure

of A in the gas phase (atm), and HA is the Henrys law coefficient of the gas

considered. Some species go back to the gas phase and migrate away from the

drop; others, once captured, remain associated with the aqueous phase unless total

evaporation occurs.

Fig. 4.1. Four main processes occur within the cloud droplet: the CCN

composition and size can change after the droplet has evaporated (1); dissolution

of soluble content of the particle (2) and aqueous reactions inside the water

droplet (3); transfers between atmospheric gases and liquid phase (4).


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4.2.3. Reactions inside the droplet.Hundreds of chemical reactions take place in the droplet. They are effective in

changing the acidity of the precipitation, which may lead to acid rain. The main

chemical species that are involved in acid rain are sulfuric and nitric acids

All this complex chemistry in which a cloud is involved modifies the cloud itself

and the atmosphere around the cloud.

4.3. Reactions of SilverSilver does not react with clean air or water under normal condition.

4.3.1. Reaction with halides.Aqueous silver reacts with elements of group VII to form its salt.

Ag+(aq) + X-(aq) = AgX(s)

By reacting with silver and halides, various precipitate will be formed.

Ion present Observation

Cl White precipitate

Br Very pale cream precipitate

I Very pale yellow precipitate

4.3.2. Reaction with acids.Silver does not react with dilute sulphuric acid. But it dissolves in hot

concentrated sulphuric acid and produces its sulphate and hydrogen gas.

H2SO4 (aq) + Ag(s) = AgSO4(s) + H2 (g)

Silver metal also dissolves in dilute or concentrated nitric acid to give silver

nitrate and nitrogen dioxide. This method is use in manufacture of silver nitrate.

Ag(s) + 2HNO3 (aq) AgNO3 (aq) + NO2 (g) + H2O (l)

Table. 4.1. Different colors silver halogens.


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4.3.3. Reactions of Silver NitrateSilver nitrate reacts with hydroxide of group 1 metals to from solid silver

hydroxide and aqueous metal nitrate.

AgNO3 (aq) + NaOH (aq) = AgOH (s) + NaNO3 (aq)

When copper metal is dipped into a solution of silver nitrate, AgNO3, silver

crystals and a blue-green solution of copper nitrate is formed.

Cu(s) + 2 AgNO3(aq) Cu (NO3)2(aq) + 2 Ag (s)

Similar reaction takes place when metals of lead or zinc are used.

4.3.4.

Reaction with water.

Silver sulphides present in soil reacts with water and produce silver metal.

3 Ag2S + 2 H2O = 6 Ag + 2 H2S + SO2

4.3.5. Decomposing of silver nitrateOn heating, silver nitrate decomposes to give silver metal.

2AgNO32Ag +2NO2 +O2

4.3.6. Reaction with organic materials.Disilver Acetylide

Silver ions react with acetylene in solution to yield the acetylide compound,

Ag2C2.

2Ag(NH3)2NO3(aq) + C2H2(aq) = Ag2C2(cr) + 2NH4NO3(aq) + 2NH3(aq)

Silver Phenylacetylide

Phenylacetylide reacts with disilver acetylide to from silver phenylacetylide.

PhCCPh(s) + Ag2C2(s) = 2PhCCAg(s)


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Silver cyanide

Potassium cyanide reacts with silver nitrate to give a white precipitate of silvercyanide.

KCN + AgNO3 = AgCN + KNO3

Solid silver fulminate reacts with nitrogen gas to give solid silver cyanide anddinitrogen oxide.

AgCNO(s) + N2(g) = AgCN(s) + N2O(g)

Solid silver cyanide reacts with ammonia gas to produce complex of ammoniumsilver cyanide.

AgCN(s) + NH3(g) = AgCNNH3(s)

Alkylsilver complex

Alkylsilver complexes can be formed by the reaction of silver nitrate with

tetraalkyllead in alcoholic solution at a low temperature.

AgNO3 + R4Pb = AgR + R3PbNO3

The yellow precipitates of the formula RAg (R = methyl, ethyl, propyl ...) werestable at -80 C for several hours, but decompose to metallic silver and gaseous

hydrocarbons upon warming to room temperature.

4AgCnH2n+1 = 4Ag0 + CnH2n+2 + (CnH2n+1)2 + CnH2n


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Properties of silver atom

Description Value Units

Density 10.5 g/cc

Atomic radius 144 pmAtomic Volume 10.3 cc/mol

Covalent Radius 134 pm

Ionic Radius 89 (+2e) 126 (+1e)

Specific Heat (@20C) 0.237 J/g mol

Fusion Heat 11.95 kJ/mol

Evaporation Heat 254.1 kJ/mol

First Ionizing Energy 730.5 kJ/molOxidation States: 2, 1

Lattice Structure: Face-Centered Cubic

Lattice Constant ( ) 4.090

Table 4.2. Properties of silver atom and silver compound.


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5. PRODUCTION OF SILVER5.1. Introduction

Slag dumps in Asia Minor and on islands in the Aegean Sea indicate that humanslearned to separate silver from lead by about 2000 BC and ever since used it for

jewelry and medium of exchange. Silver is produced from different ores and other

silver bearing compounds. Few ore bodies contain sufficient silver to justify

extraction for the silver alone. Three-fourths of all silver is produced as a by-

product of Pb, Zn, Cu, and Au mining. The most common silver-bearing

compounds are sulfides and chlorides.

5.2. Extraction of silver from lead ore using thiourea leaching solutionSilver can be extracted from silver lead ore by using thiourea [SC(NH2)2] leaching

from a pretreated Ag-Pb ore in an ammonia carbonate solution. The process of

pretreatment is carried out in a covered reactor under pure oxygen pressure.

During leaching with thiourea, silver is leached in to its solution. Silver is then

refined from this solution.

During leaching with thiourea, still some silver is not leached. This solid is treated

with Fluorosilicate solution which leaches the lead into solution, leaving silver in

it.

Fig.5.1. Principle flowsheet for processingof AgPb ore.


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5.3. Extraction from silver sulfate by electrolysisThe silver ore content subjected to leaching with HNO3. The nitric acid nitric

oxide formed is removed and solution is heated until dryness. This perocedure is

repeated with distilled water to obtain a neutral pH. NH3 is added to form silverion complexes.

Then the solution is treated with Na2SO3 and NaH2PO4. The pH of solution is then

decrease to 4.0 by adding H3PO4 solution followed by Na2S2O3 powder and

stirred. Temperature of solution is increased to 5060 C and keeps it to leach for

46 hours.

The solution is then transferred to electrolytic cell. Electrolysis is carried out usingplatinum electrode and silver that deposit on the anode is collected.

Overall reactions

During leaching

Ag2S + 4S2O2-

3 + 2SO2-

3 + 6H+ 2Ag(S2O3)

3-2 + 3S + 3H2O

During electrolysis

2Ag(S2O3)3-

2(aq) + e- Ag(s) + S2O3

2-(aq)


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6. APPLICATION OF SILVER AND SILVERCOMPOUNDS

6.1. IntroductionSilver is best known as precious metal used as jewelry and decoration in important

places. This is because of it is a rare metal which is chemically stable in normal

condition and shiny color. Other than as jewelry, there are many more uses of

silver.

6.2. Silver coinsSilver has been used as a medium of exchange since earliest recorded history, but

silver coinsthose minted by an authority either public or privatecame on the

scene in the eastern Mediterranean during 550 BC. By 269 BC, the Roman

Empire adopted silver as part of its standard coinage and it was used throughout

the trading world.

Today, other than collector's silver coins, silver bullion coins are popular among

people who desire to be cautious against currency inflation or store of value.Bullion coins are coins struck from precious metal and kept as a store of value or

an investment, rather than used in day-to-day commerce.

Description Year of introduction % purity

Canadian Silver Maple Leaf 1988 99.99%

Mexican Silver Libertad 1982 99.90%

Chinese Silver Panda 1983 99.90%

American Silver Eagle 1986 99.90%

Australian Silver Kookaburra 1990 99.90%

Australian Silver Kangaroo 1993 99.90%

British Silver Britannia 1997 95.80%

Austrian Silver Vienna Philharmonic 2008 99.90%

Russian George the Victorious 2009 99.90%

Table 6.1. Worlds most common silver bullions


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6.3. PhotographySilver-based photography is based on light striking sensitive silver-halide crystals

suspended on a film. Through use of chemical developers the differences in light

intensity form negative images which can then be processed into paper pictures byusing silver-imbedded paper. Approximately 5,000 color photographs can be

taken using one ounce of silver.

6.4. BatteryRechargeable and disposable batteries are manufactured with silver alloys as the

cathode or negative side. Silver is an expensive material to use in this application,

but it has higher efficiency when compare to batteries with other metals. The mostcommon of these batteries is the small button-shaped silver-oxide cell (used in

cameras, toys, hearing aids, watches and calculators) which is approximately 35

percent silver by weight.

In a silver-oxide cell, silver-oxide is used as the positive electrode and zinc as the

negative electrode with an alkaline electrolyte (usually sodium hydroxide or

potassium hydroxide). Inside the cell, silver ions in silver oxide reduce to solid

silver at the cathode and zinc oxidizes from metal to its ion at the anode. Thefollowing reaction takes place in the cell.

Zn + Ag2OKOH/NaOH ZnO + 2Ag

6.1. A typical silver oxide round cell.


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Due to environmental and safety concerns, silver-oxide batteries are beginning to

replace lithium-ion batteries in mobile phones and laptop computers. Silver-zinc

batteries feature a water-based chemistry and contain no lithium or flammable

liquids.

6.5. BearingSteel ball bearings electroplated with silver have greater fatigue strength and load

carrying capacity than any other type. These bearings are used in continuous,

heavy-duty applications such as in jet engines. Because steel has a poor

coefficient of friction, placing a layer of silver between the steel ball bearing and

the housing reduces friction between the two, increasing the performance andlongevity of the engine. Despite high internal temperatures, silver-coated bearings

provide superior performance and a critical margin of safety for engines. Even in

the event of an oil pump failure, silver-plated bearings provide enough lubrication

to allow a safe engine shut-down before more serious damage can occur.

6.6. Brazing and SolderingThe joining of two parts facilitated by introducing a second, low melting metal

between them is called brazing, when done at temperature above 600 C and

soldering when done at a lower temperature. During this process the parts do not

melt and produce strong, leak-tight, corrosion-resistant joint with high tensile

strength, ductility and thermal conductivity. Silver brazing alloys are used widely

in applications ranging from air-conditioning and refrigeration to electric power

distribution. It is also used in the automobile and aerospace industries.

Silver-tin solders are used for bonding copper pipe, where they not only eliminate

the use of harmful lead-based solders, but also provide the piping with silvers

natural antibacterial action. In refrigerator, silver-based bonding materials are

used to provide the ductility required for constant changes in temperature of the

cooling tubes.


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6.7. CatalystA catalyst is a substance that allows or facilitates a chemical process chemically

without involve in the reaction. Silver, because of its unique chemical properties,

has become an increasingly important catalyst for many industrial processes.

Every year over 700,000 kg of silver is being used in catalytic reactions and

approximately 90% of these are used in the production of ethylene oxide from

ethylene. Ethylene oxide is the foundation for flexible plastics such as polyester

textiles, used to make all types of clothing and a variety of specialty fabrics. It is

also used for molded items such as insulating handles for stoves, key tops for

computers, electrical control knobs, domestic appliance components, andelectrical connector housings. About 25% of ethylene oxide production is used to

manufacture antifreeze coolant for automobiles and other vehicles.

Formaldehyde, a chemical produced from methanol, is the building block of solid

plastics including adhesives, laminating resins for construction plywood and

particle board. Formaldehyde also helps to produce finishes for paper and

electronic equipment, textiles, surface coatings that resist heat and scratches,

dinnerware and buttons, casings for appliances, handles and knobs, packaging

materials, automotive parts, thermal and electrical insulating materials, toys and

many other products

Silver is a recognized powerful oxidizer. Metallurgists have long known the

unique affinity of silver with oxygen. Molten silver will hold ten times its volume

in oxygen. On freezing, the contraction of silver vigorously ejects the oxygen; a

dangerous activity known as spitting. Not all oxygen is ejected; much is retainedin the silver lattice as well as adhered to its surface.

6.8. ElectronicsBecause of silvers excellent electrical conductivity, it finds many applications in

electronics from printed circuit boards to switches and TV screens.


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Silver membrane switches, which require only a light touch, are used in buttons

on televisions, telephones, microwave ovens, childrens toys and computer

keyboards. These switches are highly reliable and last for millions of on/off

cycles. Silver is also used in conventional switches likes those used for controlling

room lights.

For printed circuit boards, used in consumer items from mobile phones to

computers, silver-based inks and films are applied to composite boards to

create electrical pathways. In similar fashion, silver-based inks produce so-called

RFID tags (radio frequency identification) antennas used in hundreds of millions

of products to prevent theft and allow easy inventory control.

Silver is also used to coat Compact Disks (CDs) and Digital Video Disks (DVDs).

In addition, silver is employed in Plasma Display Panels used in television sets

and monitors.

6.9. Medical ApplicationsSilvers anti-bacterial powers have been known for centuries and have been tested

and proven scientifically. For example, the ancient knew that water, wine orvinegar kept in silver vessels stayed fresh during long sea voyages.

Scientists have discovered that silver interrupts a bacteria cells ability to form

chemical bonds essential to its survival. These bonds produce the cells physical

structure so bacteria in the presence of silver literally fall apart. Cells in humans

and other animals have thick walls and are not disturbed by silver. Therefore,

silver prevents bacteria growth but is harmless to humans.

One of the most important uses of silver as a biocide is in hospitals and other

health care facilities because they grapple with MRSA (Methicillin-resistant

Staphylococcus aureus), a type of life-threatening Staph germ. MRSA is resistant

to almost all chemical antibiotics; therefore many hospitals are employing silver-

imbedded equipment including surgical tools, catheters, needles, stethoscopes,

furniture, door handles and even paper files.


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One of the most promising applications is in silver-imbedded bandages for burn

and wound victims. The silver ions help prevent infection but also speed healing

because the body doesnt have to focus its energy on fighting infection.

Currently were seeing a surge of applications for silver-based biocides in all

areas: industrial, commercial and consumer. New products are being introduced

almost daily. The newest trend is the use of nano-silver particles to deliver silver

ions.

6.10.Mirror and CoatingsWhen polished, silver offers nearly a perfect reflectivity which makes it ideal for

energy-efficient windows. An extremely thin, transparent coating of silver on

window panes reflects the hot, summer sun and deflects inward the rooms own

internal heat. So-called low E squared double pane windows reflect away almost

95 percent of the hot rays of the sun, offering household energy savings.

Silver halide crystals melted into the glass can change light transmission from 96

percent to 22 percent in less than 60 seconds and block at least 97 percent of the

sun's ultraviolet rays.

Another increasing use of silver is in paints. Silver ions offer an anti-bacterial

shield that keeps the coating germ and fungus free. This is particularly important

in health care facilities, jails, schools, food and beverage factories and other places

in which bacteria growth can be dangerous to health.

6.11.Solar EnergyAs the price of fossil fuels rises, scientists and engineers are more interested in

solar cells to produce electricity.

Silver paste is used in 90% of all crystalline silicon photovoltaic cells, which are

the most common types of solar cell. Photovoltaic systems are simple and provide

immediately useful power with no pollution.


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Silver is used in another way to generate electricity by reflecting and

concentrating solar energy onto collectors containing salts which are used to run

generators. In California, for example, 1,926 silver-coated mirrors reflect solar

heat onto black-coated stainless steel tubes at 300-foot tower. This heats the tubes

and the nitrate salt inside them to over 1050 F. The scalding hot salt is then

piped to boilers, turning water to steam which drives steam turbines that run

electric generators. They generate electricity to power 10,000 homes.

6.12.Water PurificationAs silver ions prevent bacteria and algae growth, silver is employing in

purification systems in hospitals, small community water systems pools etc. byusing silver in purification process, it has replaces the traditional methods of

germ-killing methods that employ harsh and dangerous chemicals.

In building water supply systems, silver ions can destroy Legionnaires disease,

which is caused by bacteria building up in pipes, connections and water tanks. In

pools and spas, silver ions, usually held in canisters within filters, are activated by

water to spread a biocide blanket to all components, keeping the water pure and

disease free.

With several different methods of water purification in the tube, often including a

charcoal filter, silvers role is to prevent the growth of bacteria and fungi that

could overwhelm the system and render it useless.

6.13.Making RainSometimes in cloudy days, it does rain. This happen because the droplets are two

small and light to fall under gravity and they are stable, that is to say they do not

become large enough to fall. Rain falls when the droplets freeze to ice so that it

will be a stable nucleus which grows by attracting water vapors from surrounding

droplets. The ice particle then grows to a size which gravity can pull it down, and

it falls as rain.


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The difficult stage in rain formation is getting the ice to nucleate it. If the water

droplets are clean, then the any nucleation catalysts. In this situation the only

nucleation agent is ice which can be formed at a very low temperature (about -40

C). Industrial dusts and smokes also do the nucleation.

Crystal of ice and crystal of silver has hexagonal structure with similar lattice

constants (H20; a = 0.452 nm, AgI; a = 0.458 nm). If silver iodide is put into super

cooled water, it can act as nucleation agent. More ice can grow on it easily, at a

low under cooling. This makes silver iodide a perfect material for artificial rain

maker.

In artificial rainmaking silver iodide, in the form of a very fine powder of crystals,

is either dusted into the cloud from a plane flying above it, or is shot into it with a

rocket from below. The powder seeds ice crystals which grow and start to fall,taking the silver iodide with them. But when it starts to fall, it leaves tiny

fragments of ice to seed next lot of crystals, thus self-catalyzing.

Fig. 6.2. Rain falls when the water droplets in clouds turn to ice. When dust

particles are present they can catalyze nucleation at temperatures quite close to

0C. This is why there is often heavy rainfall downwind of factory chimneys.


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7.SILVER IN ENVIRONMENT

7.1. IntroductionSilver and its ions are considered mildly toxic. Higher concentration of silver in

may cause danger to life in the environment.

Seawater contains approximately 2-100 ppt of silver, and the surface

concentration may be even lower. River water generally contains approximately

0.3-1 ppb of silver. The phytoplankton concentration is 0.1-1 ppm (dry mass),leading to a 104-105 bio concentration factor in seawater. In oyster tissue

concentrations of approximately 890 ppm (dry mass) were found. Dissolved in

water silver mainly occurs as Ag+ (aq), and in seawater as AgCl2 (aq).

Under normal conditions silver is water insoluble. This also applies to a number of

silver compounds, such as silver sulphide. For example, silver chloride has a

water solubility of 0.1 mg/L, maximum. Silver nitrate has a water solubility of

2450 g/L. Silver fluorides are generally water soluble, but other silver halogens

are not.

7.2. Source of SilverThe main source of silver contamination of water is silver thiosulfate complexes

in photographic developing solutions that photofinishers discard directly to

sewers. During waste treatment, most of the silver thiosulfate complexes are

converted to insoluble silver sulfide and forms some metallic silver. Silver on

suspended matter and in colloidal forms and insoluble salts ultimately settles out

in the sediments. At the water treatment plant, most of the silver is precipitated

after treatment with lime or adsorbed after treatment with alum flocculant.

Chlorination converts some silver to silver chloride or to a soluble silver chloride

complex. Aerobic biodegradation of a photoprocessing wastewater containing

1.85 mg total silver/liter did not adversely affect the activated sludge process.


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When fresh sludge and aerobically digested sludge solids is subjected to leaching

procedures, the silver concentration increases in water.

Forms of silver in atmospheric emissions are mostly silver sulfide, silver sulfate

(Ag2SO4), silver carbonate (Ag2CO3), silver halides, and metallic silver. About

50% of the silver released into the atmosphere from industrial operations is

transported more than 100 km and is eventually deposited in precipitation.

Emissions of silver from coal-fired power plants may lead to accumulations in

nearby soils. Silver in soils is largely immobilized by precipitation to insoluble

salts and by complexation or adsorption to organic matter, clays, and manganese

and iron oxides.

7.3. Effects to EnvironmentSensitive marine algae accumulates silver from water containing as little as 2 g

silver/liter (as silver nitrate) to whole-cell burdens as high as 58 mg silver/kg dry

weight. Uptake of silver by phytoplankton is rapid but proportional to silver

concentration, and inversely proportional to water salinity. Silver once integrated

with phytoplankton does not lose even if the salinity increases since it is tightlybound to the cell membrane. The ability to accumulate dissolved silver varies

widely between species. Silver accumulation is higher in marine species through

dissolved silver ions. At concentrations normally encountered in the environment,

food-chain biomagnifications of silver in aquatic systems is unlikely.

Silver inhibits enzymes for the phosphorus, sulfur, and nitrogen cycles of

nitrifying bacteria in soil thus effecting the plant growth. The concentration of

silver also can affect the germination process of the seeds. In some birds,

increasing silver concentration reduce their growth rate. In wild mammal, silver

accumulates in liver and kidneys which result in damaging the kidney.


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7.4. Health Effects of SilverSilver is not a dietary requirement for humans. The body of an adult contains

approximately 2 mg of silver. From a daily intake of 20-80 g silver,

approximately 10% is absorbed which are not health threatening. However, a

higher concentration of silver ions may be toxic due to its high affinity for sulhur

hydryl and amino groups thus the process of complexation occurs with amino

acids, nucleic acid and other compounds in the body.

Silver that ends up in the body is generally deposited in connective tissue, skin

and eyes and causes a gray to black colouring. Within 50 years, one is able to

accumulate approximately 9 mg of silver. Silver oxide is harmful uponswallowing, because it irritates the eyes, respiratory tract and skin. Silver nitrate is

much more harmful, because it is a strong oxidant. It causes corrosion and at oral

uptake it leads to vomiting, dizziness and diarrhoea.


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8.SILVER AND ISLAM8.1. Introduction

Silver as precious metal can be used in different application. It is used as

jewellery, sanitary applications and some fixtures. In Islam, these applications are

given different judgments. Therefore being a Muslim one have to follow the path

shown in Islam. In this section, I try to explain those ruling in light of Quran and

sunnah of Messenger of Allaah (peace and blessings of Allaah be upon him).

8.2.

Silver Jewellery

Silver and other kinds of jewelleries are allowed to Muslim women as adornment.

But for men there are limitations in using jewelleries. Wearing gold is haraam for

men. Men are permissible to wear rings of silver and there is nothing wrong with

it.

Anas (may Allaah be pleased with him) said: When the Prophet (peace and

blessings of Allaah be upon him) wanted to send a letter to the Romans, he wastold that they would not read any letter unless it had a seal on it, so he took a ring

of silver. It is as if I can see it shining on his hand, and engraved on it were the

words Muhammad the Messenger of Allaah. (Narrated by al-Bukhaari, 5537;

Muslim 2092).

Shaykh al-Islam (Ibn Taymiyah) was asked about men wearing silver, and he said:

As for rings of silver, this is permissible according to the consensus of the

imaams, for it was reported that the Prophet (peace and blessings of Allaah be

upon him) had a ring of silver and that his companions wore rings. This is unlike

gold rings, which are forbidden according to the consensus of the four imaams. It

was reported that the Prophet (peace and blessings of Allaah be upon him) forbade

that. As for wearing silver, there is no general statement that it is forbidden, and

no one has the right to say that it is forbidden if there is no shari evidence (daleel)

to that effect. As the Sunnah permits wearing silver rings, this is evidence thatwearing silver is permissible


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Wearing chains and adornments on the wrist and neck, and on the ears, is an

imitation of women, as this is something that is only for women and there is no

report which says that it is permissible for men to wear chains made of silver. So

it is not allowable for men to wear bracelets, earrings, anklets, or chains.

Ibn Abbaas (may Allaah be pleased with him) reported that The Messenger of

Allaah (peace and blessings of Allaah be upon him) cursed men who make

themselves look like women and women who make themselves look like men.

(Reported by al-Bukhaari, 5435).

8.3. Silver as a ValuableSilver has been mentioned in Quran as a valuable and medium of exchange. Our

Prophet Muhammad (sallalahu alaihi wa sallam) also explains the status of silver

while establishing the basics of Islamic economic system.

Ab Sad al-Khudri reported Allahs Messenger as saying: Gold for gold, silver

for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt.

(When a transaction is) like for like, payment being made on the spot, then if

anyone gives more or asks for more, he has dealt in Rib, the receiver and thegiver being equally guilty. (Sahh, Muslim)

The above Hadth of Prophet Muhammad (sallalahu alaihi wa sallam) has very

clearly established money in Islam to be either precious metals such as gold and

silver, or other commodities such as wheat, barley, dates and salt which are

commodities of regular consumption as food but which have a shelf-life.

In Quran, silver was referred as Dirham and gold as Dinar.

And they sold him for a few measly Dirhams and they did so because they

considered him to be of little worth. (Ysuf, 12:20)

In this verse of the Qurn Allah Most High has referred to money as silver

coins (Dirhams).


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There are other verses of the Quran that also refer to gold and silver as wealth.

Beautified for mankind is love of the joys (that come) from women and

offspring; and stored-up heaps of gold and silver (i.e., heaps of Dinars and

Dirhams), and horses branded (with their mark), and cattle and land. That is

comfort of the life of the world. Allah! With Him is a more excellent abode.

(le Imrn, 3:14)

O ye who believe! Lo! Many of the (Jewish) rabbis and the (Christian) monks

devour the wealth of mankind wantonly and debar (men) from the way of Allah.

They who hoard up gold and silver and spend it not (this would obviously be in

the context of use of gold and silver as money) in the way of Allah, unto them

give tidings (O Muhammad) of a painful doom. (Al-Tauba, 9:34)

"And if you wish to have (one) wife in place of another and you have given one of

them a Qintr (i.e., a treasure of gold and silver coins), then take not from it

anything; would you take it by slandering (her) and (doing her) manifest wrong?

(Al-Nis, 4:20)


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The Quran had revealed the amazing news that gold and silver would keep up

their status as objects of great value in the next world as well.

Their raiment will be fine green silk embroidered in gold. Bracelets of silver will

they wear. Their Lord will quench their thirst with a drink (sparkling) with

purity. [This verse, as well as others that follow, reveal that gold and silver will

remain precious and valuable in the hereafter as well.] (Al -Insn, 76:21)

8.4. Silver VesselsVessels of gold and silver are forbidden according to the texts of Islam and

according to scholarly consensus. It was proven that the Messenger of Allaah

(peace and blessings of Allaah be upon him) said: Do not drink from vessels of

gold and silver; do not eat from plates of gold and silver, because they are forthem in this world and for you in the Hereafter. (Saheeh, agreed upon; from the

hadeeth of Hudhayfah may Allaah be pleased with him). And it was proven that

he (peace and blessings of Allaah be upon him) said: Whoever eats and drinks

from vessels of gold and silver, is taking fire from Hell into his belly. (Saheeh,

agreed upon; from the hadeeth of Umm Salamah, may Allaah be pleased with

him; this version was narrated by Muslim).

It is not permissible to use gold and silver as vessels, whether for eating or

drinking. All of that is prohibited according to the hadeeth of the Messenger of

Allaah (peace and blessings of Allaah be upon him). It is not permissible to use

them in spoons, coffee cups or teacups; all of that is forbidden, because these are

kinds of vessels.


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8.5. Zakaah on SilverThe scholars are agreed that zakaah is obligatory on gold and silver jewellery if it

is a kind of adornment that it is haraam forbidden to use, or if it is prepared for

trading etc. But if it is a permissible kind of jewellery that is intended to be usedor loaned, such as a silver ring or womens jewellery, or things that it is permitted

to use to adorn weapons, then there is a difference of scholarly opinion as to

whether zakaah is obligatory on these things.

And those who hoard up gold and silver (Al-Kanz: the money, the Zakaah of

which has not been paid) and spend them not in the way of Allaah, announce unto

them a painful torment (al-Tawbah 9:34)

Al-Qurtubi said, in his tafseer of this aayah: Ibn Umar explained the meaning ofthis in Saheeh al-Bukhaari, when a Bedouin said to him, Tell me about the aayah

(interpretation of the meaning), And those who hoard up gold and silver. Ibn

Umar said: (It means) the one who stockpiles them and does not pay zakaah on

them woe to him. This was before (the order to pay) zakaah on them was

revealed, and when it was revealed, Allaah made it a means of purification of

wealth. (Narrated by al-Bukhaari, 2/111, taleeqan; 5/204, also taleeqan. Ibn

Maajah, 1/569-570, no. 1787. Al-Bayhaqi, 4/82).

Zakat is obligatory on

The free, adult sane Muslim, When he possesses the nisab with complete possession, and A [lunar] year has passed over it.


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Zakat Nisab

1. There is no charity [obligatory] on any [silver] less than 200 dirhams.2. Then, if it is 200 dirhams, and a [lunar] years passes over it, 5 dirhams are due

for it.

3. There is nothing due on the excess until it reaches 40 dirhams, and then 1dirham is due for it. [Similarly] for every 40 dirhams, there is 1 dirham . Abu

Yusuf and Muhammad said: Whatever exceeds 200 [dirhams] its zakat is in

proportion.

4. If the silver is dominant in silver coins, then their ruling is that of silver. But,if alloy is dominant then their ruling is that of trade goods, and its reaching

nisab is taken into account.


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9. CONCLUSION

Silver is precious metal with long history. With its discovery unknown, silver had

been used by ancient Egyptians during the time Pharaoh for decorations and

jewelries.

Silver is an important metal not because of its price or its brightness. It is important

to us due to different application its can be used and the achievement we have

made in science and technology with the help of silver. It made our life easy and

comfortable.

Because of its unique properties, silver is most preferred metal for high-tech

industries. Due to high conductivity, it is preferred to use in electronics and heat

transmitting appliance. Due to the unique chemical and biological properties, it is

perfect for medical functions. With these properties, scientists and researchers are

still trying to find more about silver.


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10. REFERENCE

1) M. F. Ashby & D. R. H. Jones: Engineering Material 2 An Introduction toMicrostructures, Processing and Designing, Second Edition, Cambridge

University, England, 1998

2) A. M. Russell, K. L. Lee: Structure Property Relation in Nonferrous Metals, AJohn Wiley & Sons, Inc., Publication, USA, 2005

3) C. E. Housecroft, & A. G. Sharpe: Inorganic Chemistry, Second Edition, PearsonEducation Limited, England, 2005

4) S. Patai & Z. Rappoport: The Chemistry of Organic Derivatives of Gold andSilver, The Hebrew University, Jerusalem, 1999

5) R.G. Gruber, E.W. Skinner and E.H. Greener: Some Physical Properties of Silver-Tin Amalgams, Journal of Dental Research, International and American

Associations for Dental Research, 2009

6) N. Shirchinnamjil, Y. Chao & F. Zhao-heng: Leaching of Silver from BoorchiAgPb Ore in Mongolia with Acidic Thiourea Solution, The Chinese Journal of

Process Engineering, Aug 2008

7) S. Ayata & H. Yildiran: A Novel Technique for Silver Extraction from SilverSulphide Ore, Ege University, Science Faculty, Chemistry Department, TURKEY,

1999

8) Imrn N. Hosein: Gold Dinar and Silver Dirham Islam and the Future of Money,Masjid Jmiah, Trinidad And Tobago, 2007

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m

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Cyanide.html

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28) 15th September 2009, http://www.silverinstitute.org/bearings.php29) 15th September 2009, http://www.silverinstitute.org/brazing_soldering.php

30)

15th

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31) 15th September 2009, http://www.silverinstitute.org/electronics.php32) 15th September 2009, http://www.silverinstitute.org/medical_applications.php33) 15th September 2009, http://www.silverinstitute.org/mirrors_coatings.php34) 15th September 2009, http://www.silverinstitute.org/solar_energy.php35) 15th September 2009, http://www.silverinstitute.org/water_purification.php36) 15th September 2009, http://support.radioshack.com/support_tutorials/batteries/bt-

siox-main.htm

37) 15th September 2009,http://en.wikipedia.org/wiki/Silver-oxide_battery38) 15th September 2009,http://nationalbullion.com/silveruses.aspx39) 15thSeptember 2009, Maqaalaat Mutanawwiah

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43) 15th September 2009,http://www.themodernreligion.com/basic/fiqh/fiqh-zakat2.html
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