Gold: historical information
Gold has always fascinated people and gold is certainly one of the very first metals known. Nobody knows who picked up a gold nugget first but it would have been because it was shiny. Gold was highly valued from from the earliest recorded times in history. It seems that the Egyptians developed gold smelting some 5600 years ago (about 3600 BC) using clay blowpipes to heat the smelter contents. Egyption inscriptions dating back to 2600 BC describe gold. Gold workers from Mesopotamia (known now as Iraq) made one of the earliest known pieces of gold jewellery in about 2600 BC. Gold is mentioned several times in the Old Testament. Tutankhamun's funeral mask is one of the most iconic gold pieces known. It was made around 1223 BC and is a stunning piece of ancient gold craftsmanship.
The first use of gold in dentistry as the Etruscans (an ancient Italian civilisation from an area corresponding now to Tuscany) begin securing substitute teeth with gold wire, and with astonishing skill. This was as early as 700-600 BC. Apparently Etruscan craftsmen made gold dental bridges for women so that they could show display their wealth and status. Some women had their incisors removed so that they could be fitted with the gold prosthetics. The Etruscans probably learned dentistry from the Egyptians, Phoenicians, and Greeks but took the art much further. Many specimens of Etruscan dental fittings are to be found in Italian and other museums.
The dental work illustrated above from the 7th century BC is a fine Etruscan specimen. Gold loops were fitted over the remaining natural teeth, set in place, and maintained by solder. The patient's missing teeth were replaced by either the teeth of human beings and on occasion the tooth of an ox.
Bio-compatibility, malleability and corrosion resistance make gold valuable even today in dental applications.
Colloidal gold has been used since Roman times to colour glass shades of yellow, red, or violet. Melting gold powder into glass diffuses gold nanoparticles into the glass, these refract light, giving the glass a luminous red glow. THe precise colour depends upon the form of the colloidal gold. Faraday (1857) recognised that the colour is due to the minute size of the gold particles and called the sample he made 'activated gold'. In 1898 Richard Adolf Zsigmondy prepared the first colloidal gold in dilute solution. Today, colloidal gold is made by the addition of reducing agents to dilute solutions of Au(III) (the auric ion). One famous form is that made by the use of tin dichloride (SnCl2) as reducing agent. This is a very stable form of colloidal gold and is known as the "Purple of Cassius". It is suitable for colouring ceramics and glasses, and in addition is a good test for Au(III). The form that Faraday studied was made using phosphorus to reduce gold chloride.
Colloidal gold has been used since Ancient Roman times to colour glass intense shades of yellow, red, or mauve, depending on the concentration of gold,
Gold is one of the elements which has an alchemical symbol, shown below (alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold).
Hallmarking practice established The world's first "hallmarking" system was established at Goldsmith's Hall in London in 1300 AD. London's Assay Office is still there. THe purpose of the hallmarking system is to determine and guarantee the quality of precious metals such as gold.
Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for gold is shown below. [See History of Chemistry, Sir Edward Thorpe, volume 1, Watts & Co, London, 1914.]
Gold has been the basis of many currencies over the centuries and so for economic reasons, among others, the possession of gold was or is restricted in some countries. Notably, private ownership of gold (apart from as jewellery and coins) was banned between 1933 and 1975. In 1422 the Venice Mint made ("struck") 1.2 million gold ducats using 4.26 metric tonnes of gold. These small coins (each about 3.5 g) were popular perhaps because they were easy to make and are highly transportable. In 1717 Great Britain moved to a pure gold standard. The British government linked the currency to gold at a fixed rate (77 shillings, ten and a half pennies per ounce of gold).
The Californian Gold Rush of 1848+1855 started on 24 January 1848 when gold was found by James W. Marshall at Sutter's Mill, in Coloma, California. Although attempts were made to keep the discovery quiet, news leaked out and the result was the migration of 300,000 people to California from the United States and beyond. The New York Herald was the first East Coast newspaper to report the discovery of gold and on 5 December 1848, President James Polk confirmed the discovery in an address to Congress. The gold-seekers were called the "Forty-niners" and often had a very hard time. Prospectors retrieved the gold from streams and riverbeds using low-technology methods such as panning. More sophisticated methods of gold recovery were eventually developed. Gold worth tens of billions of US dollars (2010 equivalent price) was extracted. Some became wealthy but many finished with little profit and a lot of heartache. Today, the forty-niners name lives on in the name of the San Francisco 49ers, an American football team in California.
Some years later in 1885 the South African Gold Rush began. An Australian miner, George Harrison, found gold on Langlaagte farm near Johannesburg while digging to build a house. South Africa became the source of almost one-half of the world's gold.
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