Gold element periodic table11/7/2023 ![]() Gold therapy, or chrysotherapy, from the Greek word for gold, chrysos, began in 1927 when gold sodium thiomalate (myocrisin) was used to treat tuberculosis (TB). Today gold is part of the medical armoury against rheumatoid arthritis. When this was shaken with oil of rosemary, they assumed some of gold passed into the oil, which they separated and the oil, aurum potabile, was prescribed as a cure-all. ![]() In the 13th century they found that gold would dissolve in a mixture of concentrated nitric and hydrochloric acids which they called aqua regia ('king of waters'). However, not all their efforts were wasted. Medieval alchemists were famous for their futile attempts to turn base metals into gold. Gold electroplating can produce a film microns thick which is used to coat electrical connectors and printed circuit boards, to protect their copper components and improve solderability. They have also been applied to the windows of some large buildings to reflect the heat of the Sun. Thin coatings of gold are used as lubricants in aerospace applications where there are high temperatures, high vacuum, or high radiation exposure. Pure gold is soft and malleable and one gram - the size of a grain of rice - can be beaten into a gold film covering one square metre. Today industry prefers '990' gold which is 99 per cent gold with 1 per cent titanium, which is a tougher alloy. Traditionally gold was measured in carats - pure gold is 24 carats 18 carat gold is 75 per cent gold and 9 carat gold is 38 per cent gold, the other metal generally being copper. Today gold is extracted from its ores using sodium cyanide which forms a water-soluble ion, Au(CN) 4. While some chemists tried to extract the metal from these waters, including the Nobel prize-winning chemist, Fritz Haber, all failed to do it economically. In contrast, the world's oceans contain more than 10 million tonnes of gold. Over the past 500 years around 100 000 tonnes of gold have been mined from its ores - equivalent to a cube of side 17 m. ![]() The gold was garnered from river sediment using mercury, which was distilled off. Ancient goldsmiths created beautiful items, and Etruscan dentists, who preceded the Romans, made gold bridges for false teeth. The first pure gold coins were minted in Lydia (modern Turkey) during the rule of King Croesus, from 561-547 BC. From ancient times gold has been a sign of wealth.
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