Metallurgy Interview Question:

How can you separate gold from mercury?

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1. Gold (Au) and mercury (Hg) are two separate metals. Therefore, from pure mercury you cannot extract Gold.

2. Amalgamation is better suited to ores in which the gold occurs in the free and cores state. Fine particles of Gold are better treated by Cyanidation.

3. Gold dissolves in aqua regia. Aqua Regia is a mixture of hydrochloric acid and nitric acid. It can dissolve gold, which single acids alone cannot do. Here we see that each of the acids separately has no effect on the gold but a mixture of the two dramatically reacts with the gold. To three samples of gold are added (1) concentrated hydrochloric acid (2) concentrated hydrochloric and concentrated nitric acids and (3) concentrated nitric acid. The gold reacts only with the concentrated acid mixture which is referred to as aqua regia (royal water)".
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