Gold

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Category: transition metal

Atomic number: 79

Colour: metallic yellow (or ‘gold’)

Melting point: 1,064°C (1,948°F)

Boiling point: 2,856°C (5,173°F)

First identified: ancient civilizations

Along with copper and silver, the elements above it in the periodic table, gold was known to the earliest civilizations. It was being used as jewellery and money at least 5,000 years ago. Gold can be found in nuggets (the largest ever found was in Australia in the 1860s, weighing in at over 70 kilograms) or in tinier pieces. You can, for instance, gather it from water by sieving rock – gold, being the heaviest metal, will always sink to the bottom. A large amount of gold was gathered using primitive methods. Tutankhamen’s tomb contained over 100 kilograms of gold artefacts. The metal is chemically unreactive (although it will dissolve in aqua regia), soft enough to be cut with a knife and highly malleable, so it can be shaped with a hammer (24-carat gold is pure gold, while lower carats indicate alloys, which are slight harder).

Each year, we mine about 1,500 tons of gold (mostly from Russia and South Africa), and the global stock continues to be recycled and reused. Beaten into thin sheets, it can be used to electroplate other metals; for instance, in cheap gold jewellery or as a protection for electrical connectors. Computer chips often contain gold wires, which are used to make circuits. Gold is also used in alloys for dental fillings, and it is a catalyst in the production of PVA glue.

The Riches of the Ocean

After the First World War, Germany was required to make punitive reparations payments. The patriotic Nobel Prize-winning scientist, Fritz Haber, hatched an audacious plan to recoup the money by gathering particles of gold from seawater, using a combination of massive centrifuges and electrochemical methods. He estimated that a ton of seawater would yield 65 milligrams of metal particles, which would have made the plan economically viable. However, the true amount of gold in seawater is closer to 0.004 milligrams per ton, and when he recalculated this correctly, the scheme had to be abandoned, to his great sorrow.

The US Federal Reserve Bank in New York contains about 7,000 tons of gold bullion, belonging to various countries. It is worth something in the region of $500 billion and is the largest repository of gold in the world.