How to extract gold from alloy using nitric acid

Written by sean lancaster
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How to extract gold from alloy using nitric acid
Nitric acid dissolves gold alloys used in jewellery, leaving behind purified gold. (Sam Robinson/Photodisc/Getty Images)

Gold jewellery is made from gold alloys, which have differing amounts of gold in them depending on the carat rating. Recycling gold becomes big business when the price of gold rises on the world markets. If you sell gold items to a recycler, the recycler usually extracts the gold from the mixed alloy to obtain purified gold. Nitric acid is often used to extract the gold. This causes a chemical reaction that can create dangerous fumes. Therefore, take extreme care if using this technique and only work in a well-ventilated area.

Skill level:

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Things you need

  • Beaker
  • Gold alloy, granulated
  • Nitric acid
  • Hotplate
  • Funnel
  • Filter paper

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  1. 1

    Place granulated gold alloy in a beaker. Add nitric acid. Stir the contents and allow the alloy to react with the nitric acid. The nitric acid will dissolve the common metals used to alloy with gold.

  2. 2

    Heat the solution on a hotplate set on low to help dissolve the alloy metals. Add more nitric acid periodically as it evaporates or as signs of a reaction cease. The chemical reaction will create bubbles as the alloy metals dissolve.

  3. 3

    Allow the solution to cool when the digestion is complete. The beaker will contain small beads of gold.

  4. 4

    Pour off the majority of the acid, then filter the remaining contents of the beaker through a funnel equipped with filter paper. The gold particles will remain in the filter paper.

  5. 5

    Rinse the gold particles with hot water a few times to clear away any remaining sludge.

Tips and warnings

  • Work in a well-ventilated area to avoid inhaling dangerous fumes.
  • Always wear safety glasses.
  • Do not allow nitric acid to come into contact with your skin.
  • Do not breathe the nitric acid fumes.
  • Small amounts of nitric acid diluted with a large amount of water can be poured down a sink, unless prohibited by local health and safety regulations. Larger amounts of nitric acid must be neutralised before disposal.

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