Sep 29, 2018

How did gold processing give rise to the term ‘acid test’

How did gold processing give rise to the term ‘acid test’ Cyanide heap leach gold mining

A total of 186,700 tonnes of gold exists above ground, as of 2015.[7]

The world consumption of new gold produced is about 50 per cent in jewellery, 40 per cent in investments, and 10 per cent in industry.[8]

Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion.

Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test.

Gold also dissolves in alkaline solutions of cyanide, which are used in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction.

Gold’s high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices (its chief industrial use).

Gold is also used in infrared shielding, colored-glass production, gold leafing, and tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine. As of 2016, the world’s largest gold producer by far was China with 450 tonnes per year.[9]

In the past, a gold standard was often implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after 1971.

(courtesy Wikipedia)

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