GOLD METAL

History

noreply@blogger.com (Azam Mohd) — Wed, 09 Sep 2009 10:35:00 +0000

Gold has been known and highly valued since prehistoric times. It may have been the first metal used by humans and was valued for ornamentation and rituals. Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was "more plentiful than dirt" in Egypt. Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. The earliest known map is known as the Turin Papyrus Map and shows the plan of a gold mine in Nubia together with indications of the local geology. The primitive working methods are described by Strabo and included fire-setting. Large mines also occurred across the Red Sea in what is now Saudi Arabia.

The legend of the golden fleece may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah) and is included with the gifts of the magi in the first chapters of Matthew New Testament. The Book of Revelation 21:21 describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC. From 6th or 5th century BC, Chu (state) circulated Ying Yuan, one kind of square gold coin.

Electronics

noreply@blogger.com (Azam Mohd) — Tue, 08 Sep 2009 10:32:00 +0000

* 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. Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts.
* Fine gold wires are used to connect semiconductor devices to their packages through a process known as wire bonding.

As gold chemical compounds

Gold is attacked by and dissolves in alkaline solutions of potassium or sodium cyanide, and gold cyanide is the electrolyte used in commercial electroplating of gold onto base metals and electroforming. Gold chloride (chloroauric acid) solutions are used to make colloidal gold by reduction with citrate or ascorbate ions. Gold chloride and gold oxide are used to make highly-valued cranberry or red-colored glass, which, like colloidal gold suspensions, contains evenly-sized spherical gold nanoparticles.

Food and drink

noreply@blogger.com (Azam Mohd) — Mon, 07 Sep 2009 12:13:00 +0000

* Gold can be used in food and has the E Number 175.

* Gold leaf, flake or dust is used on and in some gourmet foods, notably sweets and drinks as decorative ingredient. Gold flake was used by the nobility in Medieval Europe as a decoration in food and drinks, in the form of leaf, flakes or dust, either to demonstrate the host's wealth or in the belief that something that valuable and rare must be beneficial for one's health.

* Goldwasser (English: Goldwater) is a traditional herbal liqueur produced in Gdansk, 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.

Industry

# Gold solder is used for joining the components of gold jewelry 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 formulas are manufactured in most industry-standard carat weights to color 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.

# Gold can be made into thread and used in embroidery.

# Gold is ductile and malleable, meaning it can 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 cranberry glass.

# In photography, gold toners are used to shift the color 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 published formulas for several types of gold toners, which use gold as the chloride (Kodak, 2006).

# As gold is a good reflector of electromagnetic radiation such as infrared and visible light as well as radio waves, it is used for the protective coatings on many artificial satellites, in infrared protective faceplates in thermal protection suits and astronauts' helmets and in electronic warfare planes like the EA-6B Prowler.

# Gold is used as the reflective layer on some high-end CDs.

# Automobiles may use gold for heat insulation. McLaren uses gold foil in the engine compartment of its F1 model.

# Gold can be manufactured so thin that it appears transparent. It is used in some aircraft cockpit windows for de-icing or anti-icing by passing electricity through it. The heat produced by the resistance of the gold is enough to deter ice from forming.

Medicine

noreply@blogger.com (Azam Mohd) — Thu, 03 Sep 2009 11:06:00 +0000

Medicine

* 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. [8] 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.
* In modern times injectable gold has been proven to help to reduce the pain and swelling of rheumatoid arthritis and tuberculosis.[8][9]

* 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.

* Colloidal gold preparations (suspensions of gold nanoparticles) in water are intensely red-colored, and can be made with tightly-controlled particle sizes up to a few tens of nanometers across by reduction of gold chloride with citrate or ascorbate ions. 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.

* The isotope gold-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.

Jewelry

noreply@blogger.com (Azam Mohd) — Tue, 01 Sep 2009 11:51:00 +0000

Jewelry

Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color. Eighteen carat gold containing 25% copper is found in antique and Russian jewelry and has a distinct, though not dominant, copper cast, creating rose gold. Fourteen carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police, as well as other, badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminium, although rarely done except in specialized jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry. Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. White gold alloys can be made with palladium or nickel. White 18 carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper 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. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects.

Gold - Medium Of Monetary Exchange

noreply@blogger.com (Azam Mohd) — Mon, 31 Aug 2009 07:35:00 +0000

Gold - Medium Of Monetary Exchange

In various countries, gold was used as a standard for monetary exchange, but this practice has been abandoned with the rise of fiat currency. The last country to back their money with gold was Switzerland, which backed 40% of its value until it joined the International Monetary Fund in 1999. [6] Pure gold is too soft for ordinary use and is typically hardened by alloying with copper or other base metals. The gold content of gold alloys is measured in carats (k), pure gold being designated as 24k.

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, the British gold sovereign and the South African Krugerrand continue to be made at 22k, on historical tradition. The special issue Canadian Gold Maple Leaf coin contains the highest purity gold of any bullion coin, at 99.999% (.99999 fine). The popular issue Canadian Gold Maple Leaf coin has a purity of 99.99%. 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.

Gold was used as a medium of monetary exchange throughout history. At the beginning of World War I the warring nations went onto a fractional gold standard, inflating their currencies to finance the war effort. After World War II gold was replaced by a system of convertible currency following the Bretton Woods system. Many holders of gold in storage (as bullion coin or bullion) hold it as a hedge against inflation or other economic disruptions. (The ISO currency code of gold bullion is XAU).

Color of gold

noreply@blogger.com (Azam Mohd) — Sun, 30 Aug 2009 06:46:00 +0000

Color of Gold

The color of pure gold is metallic yellow. Gold, caesium and copper are the only metallic elements with a natural color other than gray or white. The usual gray color of metals depends on their "electron sea" that is capable of absorbing and re-emitting photons over a wide range of frequencies. Gold reacts differently, depending on subtle relativistic effects that affect the orbitals around gold atoms.

Common colored gold alloys such as rose gold can be created by the addition of various amounts of copper and silver, as indicated in the diagram above. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys. Less commonly, addition of manganese, aluminium, iron, indium and other elements can produce more unusual colors of gold for various applications.

Gold Characteristics

noreply@blogger.com (Azam Mohd) — Sun, 30 Aug 2009 06:42:00 +0000

Gold Characteristics

Gold is the most malleable and ductile of all metals; a single gram can be beaten into a sheet of 1 square meter, or an ounce into 300 square feet. Gold leaf can be beaten thin enough to become translucent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red.

Gold readily creates alloys with many other metals. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Gold is a good conductor of heat and electricity and reflects infra red radiation strongly. Chemically, it is unaffected by air, moisture and most corrosive reagents, and is therefore well-suited for use in coins and jewelry and as a protective coating on other, more reactive, metals. However, it is not chemically inert. Free halogens will react with gold, and aqua regia dissolves it via formation of chlorine gas which attacks gold to form the chloraurate ion. Gold also dissolves in alkaline solutions of potassium cyanide and in mercury, forming a gold-mercury amalgam.

Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated out as gold metal by adding any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate.

High quality pure metallic gold is tasteless; in keeping with its resistance to corrosion (it is metal ions which confer taste to metals).

In addition, gold is very dense, a cubic meter weighing 19300 kg. By comparison, the density of lead is 11340 kg/m³, and that of the densest element, osmium, is 22610 kg/m³.

GOLD

noreply@blogger.com (Azam Mohd) — Sun, 30 Aug 2009 06:34:00 +0000

Gold

Gold is a chemical element with the symbol Au (Latin: aurum) and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is dense, soft, shiny and the most malleable and ductile pure metal known. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. It is one of the coinage metals and formed the basis for the gold standard used before the collapse of the Bretton Woods system in 1971.

At the end of 2006, it was estimated that all the gold ever mined totaled 158,000 tonnes. This can be represented by a cube with an edge length of just 20.2 meters. Modern industrial uses include dentistry and electronics, where gold has traditionally found use because of its good resistance to oxidative corrosion and excellent quality as a conductor of electricity.

Chemically, gold is a transition metal and can form trivalent and univalent cations upon solvation. Compared with other metals, pure gold is more chemically unreactive, but it is attacked by aqua regia (a mixture of acids), forming chloroauric acid, and by alkaline solutions of cyanide but not by single acids such as hydrochloric, nitric or sulfuric acids. Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Since gold is insoluble in nitric acid which will dissolve silver and base metals, this is exploited as the basis of the gold refining technique known as "inquartation and parting". Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term "acid test", referring to a gold standard test for genuine value.

AMAZING FACTS ABOUT GOLD

noreply@blogger.com (Azam Mohd) — Sun, 30 Aug 2009 02:46:00 +0000

We admire and desire gold, there is certainly no doubt about that. However, we don't know much about it. In addition, what we do know is very little. Read the mentioned facts below and be honest with yourself when asking how many of these you already knew.

1. All seven continents have gold buried beneath their crusts.

2. The production of gold is minimal. Since ancient times, more steel is produced per hour than gold .

3. The melting point of gold is 1064.43 centigrade.

4. Gold never rusts, as it is inert.

5. It is believed that most of the earth's gold (almost 80%) is still buried underground.

6. As per a medical study in France carried out during the twentieth century, gold is an effective treatment for rheumatoid arthritis.

7. Gold is edible, and is put into fruit, jelly snacks, coffee, and tea in some Asian countries. Even Europeans are known to put gold leaf in bottles of liquor.

8. John Deason and Richard Oates of Australia found the largest nugget of gold in 1869. The nugget weighed 2248 ounces of pure gold and was 10 by 25 inches. The most amusing thing is that it was found only two inches below the ground's surface.

9. Due to gold being inert, it does not cause skin irritations. You should remember this, and if your gold jewellery causes skin irritations, then it is probably not pure gold.

10. One cubic foot of gold weighs half a ton.

11. The largest gold bar weighs 200 Kg.

12. Olympic gold medals are not pure gold. They used to be, until 1912.

13. As per a Greek myth, gold was a dense combination of water and sunlight.

14. King Ferdinand of Spain coined an immortal saying in 1511, "Get gold humanely if possible, but at all hazards get gold."

15. Gold and copper were the first metals to be discovered by men in 5000BC.

16. What is harder to find: a one-ounce gold nugget or a five-carat diamond? A one-ounce gold nugget is harder to find.

17. In every cubic mile of seawater, there are 25 tons of gold. There are 10 billion tons of gold in the oceans.

18. Only 88000 tons of gold have been mined from the earth since records were kept.

19. It is harder to win a major state lottery than it is to find gold.

20. A carat was actually a unit of weight based on the carob bean, and used by Middle East's ancient merchants.

21. The carat is still used as a measure of weight for gemstones.

22. The Egyptian civilizations were the first to use gold for jewellery.

23. Most cell phones, computers, calculators, television, and other electronic items contain gold.

24. Gold is the only precious metal that is yellow or golden in colour.

25. 90% of the gold has been discovered in the earth's surface in deserts, mountains, tropical climates, and Arctic regions.