Silver is one of the Noble / Precious Metals, well known and diffused since ancient times. It is also defined as a Coinage Metal, together with Gold and Copper. Used in coins, silverware, jewellery, electronics, medicine, chemical production, photography and more… The chemical element silver is a transition metal.
What is Silver?
Silver is a chemical element, more specifically a metal. It is very malleable and ductile. It has the highest electrical and thermal conductivity of all metal. Silver is one of the scarcest elements. Most silver used today is obtained from its ores, including argentite. The leading producers are Mexico, the 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 jewellery, tableware, and other ornamental uses and is employed in coinage, photography, dental and soldering alloys, electrical contacts, and printed circuits. Its Atomic Number is 47 and its Element Symbol is Ag. Silver is stable in oxygen and water but tarnishes when exposed to sulfur compounds in air or water to form a black sulfide layer.
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.
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 seafloor, this brine comes up through the surface out of holes called vents. When the heated brine reaches the cold seawater, the metal sulphides separated and precipitate onto the seafloor as various minerals. Copper precipitated as chalcopyrite (copper sulphide), lead as galena (lead sulphide) and zinc as sphalerite (zinc sulphide). Silver precipitates as a combination with the other sulphides.
What are the main types of Silver?
With a variety of purity levels and uses, there are several 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. To be called Sterling Silver, the metal must possess at least 92.5% pure Silver, but the other components can vary. When mixing with copper, Sterling Silver will tarnish and produce firescale.
- Silver Foil is a thin layer of Fine Silver plated 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 a 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 per cent 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 per cent silver.
- From lead concentrates
Lead concentrates are first roasted and then smelted to produce 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 per cent 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. Zinc is converted into the metallic form and vaporized from the slag, while lead is transformed into the metallic form and dissolves the silver and gold.
- From scrap
Approximately 60 per cent 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 the film is burned and the ashes leached to extract the silver content.
How was Silver used throughout history?
The first evidence of silver mining dates back to 3000 B.C., in Turkey and Greece. Ancient people even figured out how to refine silver, through a process called cupellation. Silver does not react to 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 small stars that explode produce silver, while larger stars produce gold. Spanish conquerors arrived in the New World in 1492 and they 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 per cent 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.
Where can we find Silver today?
Sterling silver contains 92.5% silver. The remaining is copper or another metal. It’s used for jewellery and silver tableware, where appearance is vital.
Silver is employed in creating mirrors because it is that the best reflector of light known, although it does tarnish with time. it’s also utilized in dental alloys, solder and brazing alloys, electrical contacts and batteries. Silver paints are used for creating printed circuits.
Silver bromide and iodide were important within the history of photography, due to their sensitivity to light. Even with digital photography development, 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 employed in clothing to forestall bacteria from digesting sweat and forming unpleasant odours. Silver threads are woven into the fingertips of gloves so they’ll be used with touchscreen phones.
Info source: http://www.rsc.org/periodic-table/element/47/silver