ams 4 silver

SILVER - PRADEEP, RUPESH, SOUMITRA AND YASHWANTH, WS 2014/15 1

ARGENTUM / SILVER

ADVANCE MATERIAL SCIENCE , WS 2014/15

Group 4 – Pradeep Tadinada, Rupesh Busanaboyina, Soumitra Shah, Yashwanth Reddy Kuntla.

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CONTENTS

Introduction Properties Production Manufacturing Costs Applications

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INTRODUCTION Silver or Argentum is one of the oldest known metal to humankind.

Classified by chemists as both transition metal and a precious metal due to its various properties.

Silver has one of the most desirable properties of any metal known.

Silver is used for making electronic device components, jewellery, utensils and also was used extensively as currency.

Top 3 Producers of Silver – Mexico, Peru and China.

Top 3 Reserve Holders of Silver – Peru, Poland and Chile.

# Source – Royal Society of Chemistry 2005

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PROPERTIES Element Silver (Ag), Group 11, Atomic number 47, d-block.

Relative atomic mass 107.868, Density 10.5 g/cm3.

Silver has melting point of 961.78⁰C, Boling point 2132⁰C.

Relative Scarcity, malleability for easy shaping, ductile, lustrous, corrosion resistance and excellent conductor of heat and electricity.

Silver is a very inactive metal. Does not react with oxygen in air under normal circumstances. But Silver does react with sulphur and sulphur compounds present in air.

Product of reaction gives silver sulphide (Ag2S), A black compound which is also called as tarnish. Thus the silverware needs polishing.

Also silver does not react with water, acids, or many other compounds. But silver burns in powder form.

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Various silver compounds undergo chemical changes when exposed to light. Similarly the sparing solubility of silver compounds, has conditioned the use of silver in the laboratory as a reagent.

Metallic silver has the property of passing into the colloidal condition, which leads to silver exhibiting different colours as per condition of process. Also, in this form the silver cannot conduct electricity.

Silver is not attacked by diluted acids except nitric acid, which dissolves silver and forms silver nitrate. The same thing happens on reaction with boiling sulphur, which gives silver sulphide.

Silver has highest thermal conductivity among metals and resistance to sparks and combustion.

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PRODUCTION Source

Silver is a rare element. Found in nature in free state and in combination.

Mostly available in complex polymetallic ores containing lead, copper and zinc. With silver having the least concentration.

The principal ores are – argentite, Ag2S; dyscrasite,Ag2Sb to Ag6Sb; hessite, Ag2Te; horn-silver, AgCl; stephanite, 5Ag2S,Sb2S3; pyrargyrite, 3Ag2S,Sb2S3; proustite, 3Ag2S,As2S3; stromeyerite, Ag2S,Cu2S; polybasite, 9(Ag2S,Cu2S),Sb2S3,As2S3; fahlore, a complex sulphide of silver, arsenic, and antimony; the bromide and iodide; and amalgams of varying composition.

Silver is a permanent constituent of living organisms.

Silver nuggets(in natural form) are found at many places all over the earth with the famous one being Silver pavement 30 meters long and 18 meters high.

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Methods The most basic step to produce silver from ore is ore

enrichment by flotation and gravitational separation.

The further extraction process of silver depends on the concentration of other metals (zinc, copper and lead) in the ore and pyrometallurgical or hydrometallurgical .

The production of silver was classified into three main divisions

Amalgamation (Patio Process), employed in countries with fuel scarcity.

Lixiviation (Cyanide Process)

Smelting, Metal is extracted from metallic lead or copper.

Silver is also recovered during electrolytic refining in AgNO3 solution. This process is used commercially and gives fine silver with 99.99% purity.

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PATIO PROCESS This process was invented by Bartolome de Medina New Spain

Mexico, in 1554. This method replaced the traditional method of smelting to extract silver from ore.

The process involved mixing of crushed fine silver ore, salt, copper sulphide and water. The resultant silver sulphide is added with mercury to form an amalgamation. Silver was later obtained by distillation and then refined using cupellation.

Ag2S + CuCl2 = 2AgCl + CuS; Ag2S + 2FeCl3 = 2AgCl + 2FeCl2 + S; 2Ag3AsS3 + 3CuCl2 = 6AgCl + 8CuS + As2S3; 2AgCl + 2Hg = 2HgCl + 2Ag.

This process requires from a fortnight to a month. After this process many different improved processes where

implemented for enriched/fine silver.09-01-2015


SILVER LIXIVIATION (CYANIDE PROCESS) This method was mostly used due to low cost of operation for

lower-grade silver ores.

The process involves dissolving of silver from the ore by an aqueous solution of salt, and then precipitated as metal or sulphide.

Cyanide process is one of the most important of the lixiviation methods and its application has been increased recently in Mexico, as the bulk of Mexican ore consists of argentite Ag2S.

The ore is very finely crushed with cyanide solution in a stamp-mill, and the sludge produced submitted to agitation and aeration in contact with cyanide solution.

The liquid is separated from the ore by the aid of mechanical filters, and the silver precipitated from the clear solution by addition of zinc in the form of dust or shavings.

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SILVER LIXIVIATION (CYANIDE PROCESS) The product is smelted with nitre, and is sometimes refined by

blowing air through the molten mass.

Another lixiviation processes are also used which depend on the ore available and content of the other elements present.

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SMELTING Smelting is applied to argentiferous lead and copper ores, silver is

concentrated in the lead or copper produced.

In this process lead and copper is extracted from the ore step by step by applying the different method. In the end from the sludge silver and gold(if available) are obtained by refining.

Refining is done by cupellation after each step. This is effected by oxidising the ore in a reverberatory furnace which are of different types as per different regions.

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MANUFACTURING OF SILVER COINS

Steps of Production

1. Melt

2. Extrude

3. Blank

4. Burnish

5. Strike

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Melt:

99.9 % pure silver is melted at 20000F

then poured into cylindrical pillets

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Extrude:

The cylindrical Billet is forced through

an Extruder to create a long , thin strip.

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Blank:

Silver Blanks are punched from the

silver strips then Blanks are weighed

for the Required size and Shape.

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Burnish:

Blanks are polished to a shine before striking.

Press:

The Unique coin Design is Etched in to the Die

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Cloud Seeding

Cloud Seeding is the attempt to change the amount or type of Precipitation that falls from the clouds.

Silver Iodide is the most common material used for Cloud seeding.

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Preparation of Silver Iodide:

Silver iodide is prepared by reaction of an iodide solution with a solution of silver ions and then it forms a Reaction of a yellowish solid quickly precipitates .

The solid is a mixture of the two principal phases. Dissolution of the AgI in hydroiodic acid , followed by dilution with water precipitates β-AgI

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Alternatively, dissolution of AgI in a solution of concentrated silver nitrate followed by dilution affords α-AgI, If the preparation is not conducted in the absence of sunlight, the solid darkens rapidly, the light causing the reduction of ionic silver to metallic. The photosensitivity varies with sample purity.

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APPLICATIONS Silver as sterling silver is used for jewellery, silverware,

electrical contacts and the like.

Silver is of the upmost importance in photography (where approximately 30% of the U.S. Industrial consumption goes into this application).

Dental alloys.

Coinage.

Silver is used in the making of solder and brazing alloys and electrical contacts.

High capacity silver-zinc and silver-cadmium batteries.

It can be deposited on glass or metals by chemical deposition, electrodeposition, or by evaporation to make mirrors.

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As paint it is used for making printed circuits and other electronic applications.

High-powered explosives.

Silver iodide is used for seeding clouds to produce rain.

Silver chloride is used as cement for glasses.

Silver nitrate (the most important silver compound) is used extensively in photography. It is used also for silvering mirrors, for silver-plating, in indelible inks, in medicine and for the production of other silver chemicals.

Silver sulphide is used for inlaying in metal work and in self-resetting circuits breakers.

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SILVER IN HEALTH CARE Silver ions are also starting to be added to water purification

systems in hospitals, community water systems, pools and spas.

Silver also eradicates Legionnaires’ disease, which is caused by buildup in pipes, connections and water tanks.

Silver has a variety of uses in the health industry.

For example, silver sulfadiazine is a very powerful compound used to treat burns, and silver is sometimes used in tooth fillings and as a biocide. The use of silver in the health industry is increasing, particularly as a biocide.

COIN AGE Silver was one of the earliest metals used to make coins. The

Romans used silver in this way as early as 269 BC (more than 2000 years ago).

Mexico is the only country today that uses silver in its circulating coinage.

Ancient India had considerable trade links with the Middle East, Europe (Greece and Rome) as well as China.

By the time of Pliny, the Roman historian, Roman trade with India was thriving, and indeed creating a balance of payments problem for the Roman Empire.

Roman coins found in India

SILVER IN TECHNOLOGY

It is used in many electrical applications, including switches, contacts and fuses. Silver is used in household switch contacts. Microwaves, dishwashers, TVs, telephones, toys and computers all contain silver. A typical washing machine contains 16 silver contacts!

Silver is an excellent conductor of heat, so one of its uses is in the rear-window defrosters of cars. The tiny silver/ceramic lines conduct heat onto the glass, clearing frost, ice and condensation.

Sterling silver is an alloy of 92.5% silver and 7.5% copper. Sterling silver is tougher than pure silver, so it can be used to make cutlery, serving trays and other ornaments and decorative tableware. It is also used to make high quality musical instruments such as flutes.

NANO SCIENCE AgNPs have been used extensively as anti-bacterial agents in

the health industry, food storage, textile coatings and a number of environmental applications.

As anti-bacterial agents, AgNPs were applied in a wide range of applications from disinfecting medical devices and home appliances to water treatment

The cotton fibers containing AgNPs exhibited high antibacterial activity against Escherichia coli

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REFERENCES Kholoud M.M. Abou El-Noura, Ala’a Eftaihab, Abdulrhman Al-Warthan, Synthesis and

applications of silver nanoparticles,Volume 3, Issue 3, July 2010, Pages 135–140

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131772/

https://www.silverinstitute.org/site/silver-in-technology/

http://www.australianminesatlas.gov.au/education/down_under/silver/used.html

http://www.rbi.org.in/currency/museum/c-ancient.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131772/

https://www.silverinstitute.org/site/silver-in-technology/

http://www.australianminesatlas.gov.au/education/down_under/silver/used.html





SILVER - PRADEEP, RUPESH, SOUMITRA AND YASHWANTH, WS 2014/15 2809-01-2015

ams 4 silver

Science

silver pradeep

introduction silver

use of silver

silver burns

metallic silver

silver sulphide ag2s

various silver compounds

complex sulphide of