The advent of coinage required methods to remove impurities from the gold. Gold parting as a process was invented specifically to remove silver. Ĭupellation removes gold and silver from mixtures containing lead and other metals, but silver cannot be separated from gold by this process alone. The metals are separated by distillation. The Acidless Separation (ALS) has been investigated to pre-refine doré and jewelry alloys even when there is high silver content, which is normally a problem for existing chemical pre-refinement processes. Affination is a largely obsolete process of removing silver from gold using concentrated sulfuric acid. Silver can be dissolved selectively by boiling the mixture with 30% nitric acid, a process sometimes called inquartation. Īlternative methods exist for parting gold. This procedure is used on a very large industrial scale and has a large set up cost due to the amount of gold that needs to be permanently dissolved in the electrolyte. Silver forms an insoluble chloride slime and copper and platinum form soluble chlorides that are removed. Gold is dissolved at the anode, and pure gold, traveling through the acid by ion transfer, is plated onto the cathode. It is an electrolytic process using pure gold for the cathode (or titanium as a starter cathode) and chloroauric acid (gold chloride-hydrochloric acid) as the electrolyte this is made by dissolving gold with chlorine gas in the presence of hydrochloric acid. Invented by Emil Wohlwill in 1874, the Wohlwill process produces the highest purity gold (99.999%).Impurities in the gold form chlorides, which form a slag that floats on the molten gold. The process involves blowing a stream of chlorine through molten gold. The Miller process affords gold up to 99.5% purity.They both start with relatively pure gold. The alloy of gold and silver is called electrum. Gold and silver are often extracted from the same ores and are chemically similar and therefore difficult to separate. Gold parting is the separating of gold from silver (and other metallic impurities).

Metal electrum