In smelting, base metal impurities are oxidised and absorbed, leaving the precious metals to be poured into ingot moulds. Smelted gold is then refined. Refining Several refining processes are used in Australia chlorination, electrolytic and aqua regia. The gas reacts with silver and any remaining base metals to form chlorides, bubbles of which rise to the surface of the molten bullion and are removed. The molten, refined gold is cast into bars.
Silver remains on the anode.
The cathodes are melted and cast. In the third process the unrefined bullion is dissolved in aqua regia and silver is precipitated as silver chloride. Sulphur dioxide gas is passed through the remaining solution and gold is precipitated as a fine metallic powder. The gold is then melted and cast. Uses Gold has long been a medium of exchange and investment.