Silver is one of the Noble / Precious Metals, well known and diffused since ancient times. It is also defined a Coinage Metal, together with Gold and Copper. Used in coins, silverware, jewelry, electronics, medicine, chemical production, photography and more.. The chemical element silver is a transition metal.
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What is Silver?
A lustrous white, ductile, malleable metallic element, occurring both uncombined and in ores such as argentite, having the highest thermal and electrical conductivity of the metals, but its greater cost has prevented it from being widely used for electrical purposes. Silver is one of the scarcest elements. Most silver used today is obtained from its ores, including argentite. The leading producers are Mexico, USA, Russia, Australia and Canada. Silver is prepared in various ways depending upon the nature of its occurrence but especially in connection with the refining of lead and copper. It is highly valued for jewelry, tableware, and other ornamental use and is used in coinage, photography, dental and soldering alloys, electrical contacts, and printed circuits. The Atomic Number of this element is 47 and the Element Symbol is Ag.
info source: http://www.elementalmatter.info/element-silver.htm
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How does Silver form?
Many of the metals that are so important to us, such as gold, silver, copper, lead, zinc, are present in the Earth’s crust only in very small amounts. Silver is present as only about 5 parts in a million.
Apart from gold, which is special, the other metals form compounds with sulphur, called sulphides. Deep in the Earth’s crust, where it is very hot, salty water circulates and dissolves these metals, collecting them up and concentrating them in the hot brine. The brine can be as hot as 350°C. Sometimes, on the sea floor, this brine comes up through the surface out of holes we call vents. When the hot brine comes into contact with the cold sea water the metal sulphides cannot stay dissolved and precipitate onto the sea floor as various minerals. Copper is precipitated as chalcopyrite (copper sulphide), lead as galena (lead sulphide), and zinc as sphalerite (zinc sulphide). Silver precipitates as a mixture with the other sulphides.
info and image source: http://www.australianminesatlas.gov.au/education/down_under/silver/formed.html
What are the main types of Silver?
With a variety of purity levels and uses, there are a number of different types of silver. Here are just several:
- Fine Silver has a .999 level of purity, so it’s also known as pure Silver. While particularly lustrous.
- Sterling Silver is an alloy that contains a mixture of 92.5% pure Silver and 7.5% of another metal, usually Copper. In order to be called Sterling Silver, the metal must possess at least 92.5% pure Silver, but the other components can vary. When mix
ed with copper, Sterling Silver will tarnish and may firescale.
- Silver Foil is a thin layer of Fine Silver placed over a base metal. Also known as Silver Tone, Silver Plate is often considered the most cost effective alternative to the more expensive forms of solid silver.
What are the stage of Silver working?
- Mining And Concentrating
Silver-bearing ores are mined by open-pit or underground methods and then are crushed and ground. Since virtually all the ores are sulfides, they are amenable to flotation separation, by which a 30- to 40-fold concentration of mineral values is usually achieved. Of the three major types of mineralization, lead concentrates contain the most silver and zinc concentrates the least.
- Extraction And Refining
The specific extractive metallurgy processes applied to a silver-bearing mineral concentrate depend on whether the major metal is copper, zinc, or lead.
- From copper concentrates
The smelting and converting of copper sulfide concentrates result in a “blister” copper that contains 97 to 99 percent of the silver present in the original concentrate. Upon electrolytic refining of the copper, insoluble impurities, called slimes, gradually accumulate at the bottom of the refining tank. These contain the silver originally present in the concentrate but at a much higher concentration; The silver obtained by electrolysis usually has a purity of three-nines fine; on occasion it may be four-nines fine, or 99.99 percent silver.
- From lead concentrates
Lead concentrates are first roasted and then smelted to produce a lead bullion from which impurities such as antimony, arsenic, tin, and silver must be removed. Silver is removed by the Parkes process, which consists of adding zinc to the molten lead bullion. The noble silver and gold remain in the elemental form, while the lead oxidizes and is removed.
- From zinc concentrates
Zinc concentrates are roasted and then leached with sulfuric acid to dissolve their zinc content, leaving a residue that contains lead, silver, and gold—along with 5 to 10 percent of the zinc content of the concentrates. This is processed by slag fuming, a process whereby the residue is melted to form a slag through which powdered coal or coke is blown along with air. The zinc is reduced to the metallic form and is vaporized from the slag, while the lead is converted to the metallic form and dissolves the silver and gold.
- From scrap
Approximately 60 percent of all silver produced is used in the photographic industry, and the metal can be recycled from spent photographic processing solutions and photographic film. The solutions are processed on-site electrolytically, while film is burned and the ashes leached to extract the silver content.
What are Silver characteristics?
Silver is considered to be non-toxic. However, most silver salts are poisonous and some may be carcinogenic.
Silver is a soft, ductile, malleable, lustrous metal. It has the highest electrical and thermal conductivity of all metals.
Silver is stable in oxygen and water, but tarnishes when exposed to sulfur compounds in air or water to form a black sulfide layer.
info source: http://www.chemicool.com/elements/silver.html
How was Silver used throughout history?
Silver’s history is long. The first evidence of silver mining dates back to 3000 B.C., in Turkey and Greece, according to the RSC. Ancient people even figured out how to refine silver. They heated the silver ore and blew air over it, a process called cupellation. The silver does not react to the air, but the base metals such as lead and copper oxidize and separate from the precious metal.
Silver forms in star explosions called supernovae, as does gold. A study published in September 2012 in the journal Astronomy and Astrophysics found that smaller stars that explode produce silver, while larger stars produce gold.
Silver really exploded on Earth, however, when Europeans landed on the New World in 1492. Spanish conquerors discovered that South America was home to rich veins of silver and silver ore, and they mined that wealth enthusiastically; according to the Silver Institute, an industry trade group, 85 percent of the silver produced worldwide came from Bolivia, Peru and Mexico between 1500 and 1800.
Silver played a big role in making early photography possible. Silver nitrate (silver combined with nitrogen and oxygen molecules) was used on photographic plates in the first, clunky cameras, according to the RSC, because it reacts to light by turning black — enabling photographers to capture an instant of light. Even with the rise of digital cameras, silver remains part of the traditional photographic process.
info source: http://www.livescience.com/37040-silver.html
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Where can we find Silver today?
Sterling silver contains 92.5% silver. The rest is copper or some other metal. It is used for jewellery and silver tableware, where appearance is important.
Silver is used to make mirrors, as it is the best reflector of visible light known, although it does tarnish with time. It is also used in dental alloys, solder and brazing alloys, electrical contacts and batteries. Silver paints are used for making printed circuits.
Silver bromide and iodide were important in the history of photography, because of their sensitivity to light. Even with the rise of digital photography, silver salts are still important in producing high-quality images and protecting against illegal copying. Light-sensitive glass (such as photochromic lenses) works on similar principles. It darkens in bright sunlight and becomes transparent in low sunlight.
Silver has antibacterial properties and silver nanoparticles are used in clothing to prevent bacteria from digesting sweat and forming unpleasant odours. Silver threads are woven into the fingertips of gloves so that they can be used with touchscreen phones.
info source: http://www.rsc.org/periodic-table/element/47/silver