Medium of monetary exchange. Pure gold is too soft for ordinary use and is typically hardened by alloying with silver, copper, or other metals. In various countries, gold, and its many alloys, are most often used in jewelry, coinage and as a standard for monetary exchange. The gold content of jewellery alloys is measured in carats (k), pure gold being designated as 24k. It is, however, more commonly sold in lower measurements of 22k, 18k, 14k and 10k. A lower "k" indicates a higher percent of silver, copper or other base metals in the alloy, copper being the more commonly used base metal. Fourteen carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Eighteen carat gold containing 25% copper is found in some antique jewelry and has a distinct, though not dominant, copper cast, creating an attractively warm color. When alloyed with silver alone, 18 carat gold appears yellow-green in color. White 18 carat gold can be made with 17.3% nickel, 5.5% zinc and 2.2% copper and is silver in appearance. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals (World Gold Council), but the palladium alloys are more expensive than those using nickel. High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver.
Gold coins intended for circulation from 1526 into the 1930s were typically a standard 22k alloy called crown gold, for hardness. Modern collector/investment bullion coins (which do not require good mechanical wear properties) are typically 24k, although the American Gold Eagle and British gold sovereign continue to be made at 22k, on historical tradition. Until recently, the Canadian Gold Maple Leaf coin contained the highest purity gold of any popular bullion coin, at 99.99% (.9999 fine). However, several other 99.99% pure gold coins are currently available, including Australia's Gold Kangaroos (first appearing in 1986 as the Australian Gold Nugget, with the kangaroo theme appearing in 1989), the several coins of the Australian Lunar Calendar series, and the Austrian Philharmonic. In 2006, the U.S. Mint began production of the American Buffalo gold bullion coin also at 99.99% purity.
Other uses:
In medieval times, gold was often seen as beneficial for the health, in the belief that something that rare and beautiful could not be anything but healthy. Even some modern esotericists and forms of alternative medicine assign metallic gold a healing power. Some gold salts do have anti-inflammatory properties and are used as pharmaceuticals in the treatment of arthritis and other similar conditions. However, only salts and radioisotopes of gold are of pharmacological value, as elemental (metallic) gold is inert to all chemicals it encounters inside the body.
Gold leaf, flake or dust is used on and in some gourmet foodstuffs, notably sweets and drinks as decorative ingredient.[2] Gold flake was used by the nobility in Medieval Europe as a decoration in foodstuffs and drinks, in the form of leafs, flakes or dust, either to demonstrate the host's wealth or in the honest belief that something that valuable and rare must be beneficial for one's health.
Gold solder is used for joining the components of gold jewellery by high-temperature hard soldering or brazing. If the work is to be of hallmarking quality, gold solder must match the carat weight of the work, and alloy formulae are manufactured in most industry-standard carat weights to colour match yellow and white gold. Gold solder is usually made in at least three melting-point ranges referred to as Easy, Medium and Hard. By using the hard, high-melting point solder first, followed by solders with progressively lower melting points, goldsmiths can assemble complex items with several separate soldered joints.
Goldwasser (German: "Goldwater") is a traditional herbal liqueur produced in Gdańsk, Poland and Schwabach, Germany and contains flakes of gold leaf. There are also some expensive (~$1000) cocktails which contain flakes of gold leaf. However, since metallic gold is inert to all body chemistry, it adds no taste nor has it any other nutritional effect and leaves the body unaltered.
Dentistry. Gold alloys are used in restorative dentistry, especially in tooth restorations, such as crowns and permanent bridges. The gold alloys' slight malleability facilitates the creation of a superior molar mating surface with other teeth and produces results that are generally more satisfactory than those produced by the creation of porcelain crowns. The use of gold crowns in more prominent teeth such as incisors is favored in some cultures and discouraged in others.
Gold can be made into thread and used in embroidery.
Gold is ductile and malleable, meaning it is able to be drawn into very thin wire and can be beaten into very thin sheets known as gold leaf.
Gold produces a deep, intense red color when used as a coloring agent in glass.
In photography, Gold toners are used to shift the colour of silver bromide black and white prints towards brown or blue tones, or to increase their stability. Used on sepia-toned prints, gold toners produce red tones. Kodak publish formulae for several types of gold toners, which use gold as the chloride (Kodak, 2006)
Electronics. The concentration of free electrons in gold metal is 5.90×1022 cm-3. Gold is highly conductive to electricity, and has been used for electrical wiring in some high energy applications (silver is even more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the Manhattan Project's atomic experiments, but large high current silver wires were used in the calutron isotope separator magnets in the project.
Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments (including resistance to non-chlorinated acids) has led to its widespread industrial use in the electronic era as a thin layer coating electrical connectors of all kinds, thereby ensuring good connection. For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and USB cables. The benefit of using gold over other connector metals such as tin in these applications, is highly debated. Gold connectors are often criticized by audio-visual experts as unnecessary for most consumers and seen as simply a marketing ploy. However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain computers, communications equipment, spacecraft, jet aircraft engines) remains very common, and is unlikely to be replaced in the near future by any other metal.
Besides sliding electrical contacts, gold is also used in electrical contacts because of its resistance to corrosion, electrical conductivity, ductility and lack of toxicity.[3] Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts.
Colloidal gold (Colloidal sols of gold nanoparticles) in water are intensely red - colored, and can be made with tightly-controlled particle sizes up to a few tens of nm across. Colloidal gold is used in research applications in medicine, biology and materials science. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells (Faulk and Taylor 1979). In ultrathin sections of tissues viewed by electron microscopy, the immunogold labels appear as extremely dense round spots at the position of the antigen (Roth et al. 1980). Colloidal gold is also the form of gold used as gold paint on ceramics prior to firing.
Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. The coating, which is usually applied by sputtering with an argon plasma, has a triple role in this application. Gold's very high electrical conductivity drains electrical charge to earth, and its very high density provides stopping power for electrons in the SEM's electron beam, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases the spatial resolution of the image. Gold also produces a high output of secondary electrons when irradiated by an electron beam, and these low-energy electrons are the most commonly-used signal source used in the scanning electron microscope.
Many competitions, and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner.
As gold is a good reflector of both infrared and visible light, it is used for the protective coatings on many artificial satellites and in infrared protective faceplates in thermal protection suits and astronauts' helmets.
White gold (an alloy of gold with platinum, palladium, nickel, and/or zinc) serves as a substitute for platinum.
Green gold (a gold/silver alloy) is used in specialized jewelry while gold alloys with copper are more standard, ranging from a pale yellow with little copper all the way to a deep pink with more copper (rose gold).
Blue gold can be made by alloying with iron
Purple gold can be made by alloying with aluminum (done rarely except in specialized jewelry)
Gold is used as the reflective layer on some high-end CDs.
The isotope gold-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.[citation needed]
Gold can be used in food and has the E Number 175
........................................................
(source : wikipedia.org)
Gold coins intended for circulation from 1526 into the 1930s were typically a standard 22k alloy called crown gold, for hardness. Modern collector/investment bullion coins (which do not require good mechanical wear properties) are typically 24k, although the American Gold Eagle and British gold sovereign continue to be made at 22k, on historical tradition. Until recently, the Canadian Gold Maple Leaf coin contained the highest purity gold of any popular bullion coin, at 99.99% (.9999 fine). However, several other 99.99% pure gold coins are currently available, including Australia's Gold Kangaroos (first appearing in 1986 as the Australian Gold Nugget, with the kangaroo theme appearing in 1989), the several coins of the Australian Lunar Calendar series, and the Austrian Philharmonic. In 2006, the U.S. Mint began production of the American Buffalo gold bullion coin also at 99.99% purity.
Other uses:
In medieval times, gold was often seen as beneficial for the health, in the belief that something that rare and beautiful could not be anything but healthy. Even some modern esotericists and forms of alternative medicine assign metallic gold a healing power. Some gold salts do have anti-inflammatory properties and are used as pharmaceuticals in the treatment of arthritis and other similar conditions. However, only salts and radioisotopes of gold are of pharmacological value, as elemental (metallic) gold is inert to all chemicals it encounters inside the body.
Gold leaf, flake or dust is used on and in some gourmet foodstuffs, notably sweets and drinks as decorative ingredient.[2] Gold flake was used by the nobility in Medieval Europe as a decoration in foodstuffs and drinks, in the form of leafs, flakes or dust, either to demonstrate the host's wealth or in the honest belief that something that valuable and rare must be beneficial for one's health.
Gold solder is used for joining the components of gold jewellery by high-temperature hard soldering or brazing. If the work is to be of hallmarking quality, gold solder must match the carat weight of the work, and alloy formulae are manufactured in most industry-standard carat weights to colour match yellow and white gold. Gold solder is usually made in at least three melting-point ranges referred to as Easy, Medium and Hard. By using the hard, high-melting point solder first, followed by solders with progressively lower melting points, goldsmiths can assemble complex items with several separate soldered joints.
Goldwasser (German: "Goldwater") is a traditional herbal liqueur produced in Gdańsk, Poland and Schwabach, Germany and contains flakes of gold leaf. There are also some expensive (~$1000) cocktails which contain flakes of gold leaf. However, since metallic gold is inert to all body chemistry, it adds no taste nor has it any other nutritional effect and leaves the body unaltered.
Dentistry. Gold alloys are used in restorative dentistry, especially in tooth restorations, such as crowns and permanent bridges. The gold alloys' slight malleability facilitates the creation of a superior molar mating surface with other teeth and produces results that are generally more satisfactory than those produced by the creation of porcelain crowns. The use of gold crowns in more prominent teeth such as incisors is favored in some cultures and discouraged in others.
Gold can be made into thread and used in embroidery.
Gold is ductile and malleable, meaning it is able to be drawn into very thin wire and can be beaten into very thin sheets known as gold leaf.
Gold produces a deep, intense red color when used as a coloring agent in glass.
In photography, Gold toners are used to shift the colour of silver bromide black and white prints towards brown or blue tones, or to increase their stability. Used on sepia-toned prints, gold toners produce red tones. Kodak publish formulae for several types of gold toners, which use gold as the chloride (Kodak, 2006)
Electronics. The concentration of free electrons in gold metal is 5.90×1022 cm-3. Gold is highly conductive to electricity, and has been used for electrical wiring in some high energy applications (silver is even more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the Manhattan Project's atomic experiments, but large high current silver wires were used in the calutron isotope separator magnets in the project.
Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments (including resistance to non-chlorinated acids) has led to its widespread industrial use in the electronic era as a thin layer coating electrical connectors of all kinds, thereby ensuring good connection. For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and USB cables. The benefit of using gold over other connector metals such as tin in these applications, is highly debated. Gold connectors are often criticized by audio-visual experts as unnecessary for most consumers and seen as simply a marketing ploy. However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain computers, communications equipment, spacecraft, jet aircraft engines) remains very common, and is unlikely to be replaced in the near future by any other metal.
Besides sliding electrical contacts, gold is also used in electrical contacts because of its resistance to corrosion, electrical conductivity, ductility and lack of toxicity.[3] Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts.
Colloidal gold (Colloidal sols of gold nanoparticles) in water are intensely red - colored, and can be made with tightly-controlled particle sizes up to a few tens of nm across. Colloidal gold is used in research applications in medicine, biology and materials science. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells (Faulk and Taylor 1979). In ultrathin sections of tissues viewed by electron microscopy, the immunogold labels appear as extremely dense round spots at the position of the antigen (Roth et al. 1980). Colloidal gold is also the form of gold used as gold paint on ceramics prior to firing.
Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. The coating, which is usually applied by sputtering with an argon plasma, has a triple role in this application. Gold's very high electrical conductivity drains electrical charge to earth, and its very high density provides stopping power for electrons in the SEM's electron beam, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases the spatial resolution of the image. Gold also produces a high output of secondary electrons when irradiated by an electron beam, and these low-energy electrons are the most commonly-used signal source used in the scanning electron microscope.
Many competitions, and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner.
As gold is a good reflector of both infrared and visible light, it is used for the protective coatings on many artificial satellites and in infrared protective faceplates in thermal protection suits and astronauts' helmets.
White gold (an alloy of gold with platinum, palladium, nickel, and/or zinc) serves as a substitute for platinum.
Green gold (a gold/silver alloy) is used in specialized jewelry while gold alloys with copper are more standard, ranging from a pale yellow with little copper all the way to a deep pink with more copper (rose gold).
Blue gold can be made by alloying with iron
Purple gold can be made by alloying with aluminum (done rarely except in specialized jewelry)
Gold is used as the reflective layer on some high-end CDs.
The isotope gold-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.[citation needed]
Gold can be used in food and has the E Number 175
........................................................
(source : wikipedia.org)
(source : kitco.com)
No comments:
Post a Comment