Silver is a rare and valuable metal that has been considered precious since ancient times. It is also highly resistant to oxidation and corrosion, which makes it a noble metal, even if it is more reactive than gold. It is very valuable for electrical purposes, because it is the best conductor of heat and electricity of all metals. Silver is found in many medical and consumer products, since it is not toxic and has an antiseptic effect. It has always been used in jewellery, mirrors and other precious items, due to its attractive shiny appearance. This metal is also very ductile and malleable, so it can be easily tuned into sheets or wires that have many industrial applications. The film and photographic industry also used silver for its excellent photosensitivity.
Silver is cheaper than gold because it is more common and doesn't have the same chemical properties. It is known for the very easy processing: it can be used in alloys, flattened into printable sheets, worked into wires, ground as a powder, turned into paste or shaved into flakes. It can be used as a catalyst, as a colloid or as a salt after reacting with other compounds. It has always been considered to be a symbol of wealth and status in the manufacture of jewellery or coins but it is also a very important industrial metal.
Silver is a metal with the chemical symbol Ag and the atomic number 47. Like many elements, its name comes from an ancient Latin word, in this case "argentum". Many people wear silver jewellery or use items made from this metal, so it is one of the best known elements. It is also present in the myths and beliefs of many cultures of the world. Many mining operations focus on the extraction and refining of silver because this metal is not only used for ornamental purposes but is also very important in industry.
This metal has been considered to be precious since ancient times and humans have actually discovered it very early. Items made from silver are commonly found by archeologists, these range from jewellery to weapons or armour plates. Even if silver is not as soft as gold, it's a very ductile metal. It forms alloys with other metals, especially copper, and it is easy to work with. Pure silver reacts quickly with air, so old objects normally have a green or black color. The tarnish layer is easily removed, making the metal attractive once again. However, it is lustrous and shiny when new and has excellent electric and thermal conductivity.
Since it is not very reactive, silver can sometimes be found in pure metallic from in nature. However, in most deposits it is mixed with other metals, in particular gold or copper. A process of refining separates these metals and they can be used in industry. Many minerals also include silver, combined with other elements. One if the most useful compounds of silver is the nitrate, which has wide industrial applications, from the production of antiseptics to photography.
Modern industry makes heavy use of both metallic silver and some of its salts. Some of the compounds can be highly poisonous, even if pure silver is not, so careful handling is required. In order to avoid ingesting or inhaling these chemicals, people who work with silver salts should always wear gloves and eye protection. Silver processing is also highly dangerous because chemicals that contain toxic lead can produce poisonous fumes.
Since silver has a high value, it has been used heavily in the production of coins. While silver coins are no longer used as currency by most states, they are still produced by national banks as special commemorative issues for collectors. However, silver jewellery remains as popular as ever due to the high quality and reasonable price. It can be found all over the world, from simple silver rings to real masterpieces that include this noble metal.
Prehistoric humans knew how to extract seven metals and silver is one of them. As a result, the story of its discovery has been lost forever. Copper, silver and gold, which are all metals from group 11, are often found in nature in pure form. As a result, early humans probably used them as a very primitive form of currency in the exchange of goods. Copper was one of the first metals used in metallurgy but silver could not serve the same purpose since it is not as durable. It was more valuable as money or in the production of ornaments. Elemental silver is actually rarer in nature than pure gold, because it is more chemically reactive. Its rarity made it valuable in ancient times, the fifteenth century BC it was more expensive than gold in ancient Egypt. Egyptians might have been the first to heat mixtures of silver and gold with salt in order to purify the two metals, since the silver chloride that results from the reaction can be separated.
When humans discovered the cupellation technique that allowed silver extraction from ores, the metal became more common and its price dropped. Starting in the 4th millennium BC, the separation of silver from lead became possible, as proven by slag heaps discovered by archaeologists in the Aegean Islands, Asia Minor and other locations in the Mediterranean Sea. At the start of the Chalcolithic era, Sardinia was one of the most important silver extraction regions in the world. However, the technique propagated very slowly to other areas. Historians believe that silver was also produced by ancient Asian civilizations in China, India and Japan, but there is no actual evidence.
There are many uses for both silver and some of its compounds. Of all metals, silver is the best at conducting both heat and electricity. It is a prime material for the production of circuit boards, solder or electrical contacts. While silver reflects visible light better than any metal, mirrors made from it will tarnish unless protected by a layer of coating. Historically, one of the main uses for silver was the production of coinage. Today, coins are usually made from common metals. An alloy with a content of 92.5%, known as sterling silver, is widely used to produce jewellery and silver decorative items. Silver is also included in batteries with high capacity, combined with either zinc or cadmium. AgNO3, or silver nitrate, is needed in the photo industry due to its sensitivity to light, while rain can be triggered using silver iodide in the clouds.
Many medicinal items are also manufactured from silver, because it is not toxic and can be handled safely. It is found as an ingredient in many products because of its natural antiseptic effect, examples include creams, wound dressings, or antibiotic coating. Silver sulfadiazine or silver nanomaterials have also been used against external infections, but there is not enough clinical evidence at the moment to prove the effectiveness of these treatments. Endotracheal breathing tubes coated with silver might reduce the risk of ventilator-associated pneumonia, according to the results of some studies. There is however enough evidence that in vitro bacteria are killed by concentrated silver ions (Ag+), which have bioactive properties.
Besides medical items, silver and its particles are also used in various industrial or home objects, due to the lack of toxicity and proven antibacterial effects.
A number of important medicines include silver. Silver sulfadiazine is used in the treatment of external burns and it's considered such an effective antiseptic that WHO lists it among the essential drugs.
Warts and corns can be eliminated using silver nitrate, which is produced through the reaction of silver and nitric acid. It is usually applied using a pencil that has the active caustic substance on its end.
Using catheters can cause urinary tract infections, so urologists use Silver Coat Foley catheters in order to prevent them. Silver Coat is actually a patented technology owned by Canadian company Covalon, which is very active in medical research.
Conventional x-ray films still rely on silver halides as the image receptors used in radiology. While newer technologies have been available for a long time, this obsolete type of x-ray is still found in some poor countries.
Due to its antiseptic effect, silver can reduce the risk of infection when added to wound dressings or bandages. Various ointments and gels used to treat minor wounds also have a content of silver.
Surgical implants can cause serious infections. The risk can greatly be reduced by coating the implants and medical prostheses with a silver layer. These are inserted in order to repair various bones such as the tibia, femur or knee joints.
Newborn babies often suffer from pink eyes, which is actually the eye infection conjunctivitis. The condition is treated today with erythromycin and other modern antibiotics but eye drops based on silver nitrate have been used for a very long time.
Ingesting silver diamine fluoride can greatly reduce the risk of dental cavities. This compound seems to be particularly effective when administered to kids.
In the early 1900's, Reuben Ottenberg was the first to notice that silver is very well suited for closing open wounds. Surgeons have used the metal in sutures and needles ever since.
SMART-HIP is a patented type of hip joint implant that is based on bearing coated with silver. Silver's ability of self-lubrication reduces friction and makes the implants last longer, while the antiseptic effect of the metal prevents infections.
The transmission of light through windows can be controlled by adding silver to the polyester sheets that are used to manufacture them. Due to the same effect, silver is also often applied on windshields. It helps them repulse more solar light than other conventional materials that can serve as coating.
Since silver reduces friction and is highly resistant to heat, the engine bearings of cars are coated with silver through electroplating.
This metal is also suited for metal work, especially in soldering or brazing. The pipes needed for water transport, air conditioning or heating systems can be connected through silver soldering at the joints.