Silver

Everything You Need To Know About Silver

Silver is an element. The Latin name for silver is argentum. The symbol of silver is Ag, derived from the Latin word argentum. The literal meaning of argentum is shiny. It also means white. The element silver is a metal. It is white, soft and lustrous. Silver has the highest thermal and electrical conductivity among metals. It is also the most reflective metal. Native silver is the free elemental form of the metal. It is found in its pure state in the crust of the Earth. Silver is also found in alloys of other metals, including gold, and minerals like chlorargyrite and argentite. While silver is mined in abundance in many parts of the world, most of what is produced is actually a byproduct of refining copper, lead, zinc and gold.

History of Silver

Silver is one of the few metals considered precious, not for its physical and chemical properties but due to its sheer value. It is less precious than diamond and gold, but dearer than bronze, copper and iron. Silver has been a precious metal for most of recorded history. It has been used to make coins and jewelry for millennia. The contemporary use of silver is much more diverse. It is used in distinct applications such as solar panels and water filtration systems, electrical conductors and window coatings. Solutions or compounds of silver, such as silver nitrate, are used in microbiocides and disinfectants.

Prehistoric humans did not know the modern periodic table. They knew several elements, of which only seven were metals. These are often referred to as the antique metals or metals of antiquity. Since these prehistoric times were not as well documented as the last two thousand years, it is unclear when and how silver was first discovered, and by whom. Three metals of antiquity are found in their pure form in nature. These are copper, gold and silver. Prehistoric humans did not have to know metallurgy or possess knowledge about ores, refining and other aspects of chemistry to work with copper, gold and silver. There is of course evidence of prehistoric humans being deft at working with ores, which is how the different ages evolved.

Copper, gold and silver were used as forms of money. They replaced the archaic barter system in several ancient civilizations. Copper led to the fascinating expansion in metallurgy due to its high structural strength. Silver did not have such an impact because of its poor structural strength. It found use in ornaments and was treasured for its monetary value. An interesting fact about silver and gold is their respective abundance. Natural gold is more abundant than native silver. This is the primary reason for silver being considerably more expensive than the yellow metal in Egypt for centuries.

Silver is more abundant than gold, but it did not become evident until a process called cupellation became popular. Cupellation is a method of extraction. Native silver is pure and found in its natural state. Silver is also found in ores. These ores are subjected to cupellation and silver is extracted. The method dates back several millennia. There is evidence to prove that silver was extracted from ores containing lead as far back as six thousand years ago. However, this knowledge remained confined to the regions of Aegean Sea, Sardinia and Asia Minor or Anatolia. There is also evidence that silver was being produced, mined in natural reserves and extracted from ores, in India, Japan and China around four to six thousand years ago. Lack of documentation and records make it impossible to understand their methods of production, extraction and refinement.

The Phoenicians brought silver to Europe. The renowned traders straddled the Mediterranean and regions in West Asia. They had amassed so much silver that they chose to replace the lead in the anchors of their ships with the metal. Silver became the obvious choice of metal for coins for both Greeks and Romans.  The silver mines of Laurium were one of the factors that contributed to the glorious rise of Athens. The abundance and hence steady supply of silver maintained the stability of the currency and subsequently the economy of the Roman Empire. By the end of the first millennium, silver was being mined in several regions of Europe, including central and northern parts, the Mediterranean, Bohemia, Erzgebirge, Saxony, Alsace, Silesia, the Lahn region, Hungary, Siegerland, Norway, Salzburg, Steiermark and the southern sections of the Black Forest.

The new world ushered in another era of silver mining and production. The Americas had rich deposits of the metal, both in its native or pure form and in ores. Silver was already being mined in the Americas before the Columbian age of discovery. The Spanish, the Portuguese, the French and the English brought their knowledge and resources to boost the production of the metal. The largest producers of silver in the new world were Peru, Chile and Bolivia. Another country with one of the largest natural reserves of silver in the world actually derived its name from the Latin word for the metal. Argentina is named after the metal argentum. Today, silver is produced abundantly in North America, especially Canada, Nevada in the United States and Mexico. Siberia, Australia, Poland and Peru continue to be major producers of silver in the world.

Properties of Silver

Silver is highly ductile. It can be shaped into the form of a wire, as thin as an atom. The chemical and physical properties of silver are similar to those of gold and copper. Silver has forty seven electrons. The soft metal is also malleable. Gold is more malleable than silver though. The most striking physical quality of silver is its luster. The white metal looks brilliant after it is polished. Silver is highly conductive, both thermally and electrically. Silver is more conductive than copper. The latter is preferred for wires and other products because of the low cost. Silver is not a financially viable material to make conductive materials or products meant for widespread use. The metal is preferred in radio frequency engineering, especially for very high frequency or VHF.

Silver is the least resistant metal when it comes in contact with other metallic elements. It can form alloys with gold, copper and zinc. Silver can crystalize. Natural or native silver has two isotopes, excluding the unstable ones. These are 107Ag and 109Ag. 107Ag is more abundant. More than 51% of natural or native silver is 107Ag. The metal has twenty eight radioisotopes. 105Ag is the most stable radioisotope of the metal with a half-life of seven and a half days. 112Ag is also stable and has a half-life of just over three hours. There are several nuclear isomers. 108mAg is the most stable nuclear isomer of silver. It has a half-life of four hundred and eighteen years. 110mAg and 106mAg are also stable isomers.

Silver is an unreactive element. It finds a place way towards the bottom in the electrochemical series. It has the least first ionization energy. The metal shows no reaction with air. This was the reason why alchemists regarded it as one of the noble metals. Silver does react to sulfur. It tends to get tarnished and forms black silver sulfide. Silver does not respond to halogens, excluding fluorine gas. The metal is invulnerable to non-oxidizing acids but gets dissolved when exposed to or treated with hot concentrated sulfuric acid. Concentrated nitric acid too has the same effect. The metal reacts to hydrogen peroxide and can quickly dissolve in cyanide solutions.

Silver suffers from three kinds of deterioration. It gets tarnished, forms silver chloride when immersed in salt water for a long period of time and react with oxygen or nitrate ions. Silver is white but silver chloride is yellowish when fresh and purplish when exposed to light. There are many oxidation states of the metal. The most common and stables ones are silver nitrate, silver fluoride and potassium tetrafluoroargentate.

Uses of Silver

The most common applications of silver are jewelry and kitchenware. Both industries are massive. Silver jewelry is very popular in almost every culture in the world. Silverware or utensils such as knives, forks and spoons along with the use of the metal in some crockery is equally popular. Silver is a preferred material for kitchenware due to its antibacterial quality. However, it should be noted that silverware is essentially plated with the metal. Silverware is not made entirely of the metal, or with its purest form. Silver is also used to plate glass in mirrors and vacuum flasks.

The metal is of immense significance in medicine. Silver is used in dressings for its antibiotic property. Medical devices make use of this metal for the very same reason. Compounds of silver are used to dress wounds and to cure external infections. Silver is used in urinary catheters, endotracheal breathing tubes, some implants and topical drugs.

Many electronics contain silver. The metal is used for electrodes and conductors. Foils made of or containing silver are used in vacuum tubes, semiconductor devices and circuits. It is of great utility in radio frequency, especially very high and higher frequencies. Cavity filters, printed circuits and antennas used for radio frequency have silver paints. Silver in its powdered form and alloys is used as electrodes and layers in conductors. Ceramic capacitors also use silver.

Silver is used for the purpose of brazing alloys. These can braze different metals and metallic materials, such as cobalt, copper alloys, nickel and steel. It can also braze precious metals. The white metal can increase the workability and resistance to corrosion of different materials, including tin, zinc, cadmium, phosphorus, manganese and palladium. The metal is used in many types of chemical equipment. Silver is a catalyst and is hence used in oxidation processes. It is one of the finest catalysts, which is why very little is needed even for some of the larger processes.

Silver is highly photosensitive. Silver halides are widely used in photography. Digital photography does not use silver or any of its compounds. Silver nitrate is at the crux of black; white traditional photography, development and tuning of photos, color photography that includes special dyes; sensitizers and the bleaching process. The scope of this application has shrunk in recent times due to the paradigm shift to digital photography. Silver nanoparticles are used in conductive inks that are used in printed electronics. They are an integral component of antifungal and antibacterial medicines. Silver nanoparticles are also used in cosmetics and pigments.

Native silver, which is the purest form of the metal, is used in food color. Silver foil is used for decorative purposes on dishes and other utensils, especially in some parts of Asia. Dragee made of or containing silver is used in cakes and cookies, among other desserts. Photochromic lenses use silver halides. Films made of silver chloride find use in radiation detectors. Silver ions can desalinate seawater and hence are used during rescues. Colloidal silver disinfects swimming pools. Crystals of silver iodide play a role in cloud seeding that triggers rain.

Toxicity of Silver

Silver is not a heavy metal. It is a transition metal, as are gold and copper. Silver is not toxic. However, the metal should not be ingested. The human digestive system is not capable of metabolizing silver. If any of it is at all absorbed, it gets converted to silver compounds. These compounds are insoluble. While native silver or the pure form does not pose any toxicity to humans, its nitrate and fluoride compounds are harmful. The caustic nature of these compounds results in tissue damage. If consumed, they can cause diarrhea, gastroenteritis, cramps, respiratory arrest and paralysis. Blood pressure may plummet as well.

Continuous exposure to and ingestion of silver in any form, such as salts that are given to animals, lead to complications and can have serious effects on health. Animals given regular doses of silver salts have anemia, liver necrosis, slow growth and degeneration of kidneys and the liver. A large dose of silver or its compounds can cause pigmentation in the human eyes, mucous membranes and skin.

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