How to Purify Gold

Purifying gold

Before gold is sold on the market, it has to go through a purification process. This process is quite complex and dangerous. It needs to be done under the right circumstances and with the utmost care in safety precautions. It is not recommended to try this process unless you have experience working with harmful chemicals.

Difficulty:

Challenging

Instructions

Things You'll Need

• 2 beakers
• Hot plate
• Glass rod
• Coffee filter
• Gold ore
• Hydrochloric acid
• Formic acid
• Nitric acid
• Sodium sulfite
• Un-iodized salt
• Borax

1. Prepare your beakers. Place your gold ore into one of the beakers. In your second beaker, mix three parts hydrochloric acid to one part nitric acid. Be very careful when mixing your acids, as both are quite toxic and can be dangerous. Be sure that you are also wearing protective eye wear as well as gloves that can hold up against acid.

2. Mix your acid beaker with your ore beaker and simmer. Be careful to do this quite slowly and carefully. Once you have combined your two beakers, simmer the mixture on a hot plate until all of the nitric acid has been boiled off. If most of the liquid evaporates before the nitric acid is gone, you can add a small amount of hydrochloric acid to keep the ore covered in liquid.

3. Filter the solution. Use a strainer to filter off any of the solid that may be left from the boiling process. Do not dispose of the solid without first treating it with a solution, such as lime juice, to neutralize it. After you have strained out the solid, add equal amounts of distilled water, as there is liquid in the beaker.

4. Check for silver. Before you can extract the gold, you must first extract any silver that may be present in the ore. Slowly drop small amounts of the un-iodized salt into the mixture. This should cause little white particles of silver chloride to drop to the bottom of the container. You can then use a coffee filter to strain out the liquid from the silver particles. Set the silver aside. Be sure to keep the liquid that you have strained off because it still will contain the gold.

5. Check for gold. Put the remaining acid mixture back into a beaker. Slowly add sodium sulfite to the mixture. This will cause the gold to continue to add the sodium until the gold stops moving to the bottom of the beaker. Filter the solution again using a coffee filter. Rinse and dry the filter containing your gold.

6. Heat the gold. Now that you have your separated gold, put the filter into a clay crucible and set the filter on fire to get rid of it. Cover the gold and the filter with borax and place it in a furnace that is capable of reaching temperatures of 2,000 degrees F until the gold is smooth. Pour into a mold and let it cool.

Tips & Warnings

• These chemicals are very dangerous. Mixing them wrong or inhaling their fumes will not only hurt you, but some can even kill you if ingested. Take every precaution possible and do not attempt this process unless you are an experienced chemist or goldsmith.

References

• Newton BBS: Gold Purification

Resources

• Read this Article in Spanish