If you have scraps of gold jewellery, old fillings or gold parts from electronics sitting around, you may want to refine them into pure gold bullion. Even jewellery that has gems can be refined and melted down; the gems will be removed later. Refining gold is not a labour-intensive process, but it requires a relatively long wait for the process to finish. It can also be dangerous as you will use toxic chemicals and acid. The acid bath that you use to refine your gold is sometimes referred to as Aqua Regia, or king's water. It is a mixture of hydrochloric and nitric acids that received the name aqua regia because it was used to melt down the royal metals of gold and platinum.
Gather your gold scraps and weigh them. Write down the weight in ounces. Place all of the gold into a large plastic container.
Put on your protective clothing, gloves, goggles and face mask.
Mix nitric acid and hydrochloric acid in a ratio of 1 ml of nitric acid for every 4 ml of hydrochloric acid in a large plastic bucket with millimetre measurements on the side. This mixture is known as aqua regia.
Pour the aqua regia into the gold container at a rate of 150 ml for every ounce of scrap gold you have in the container. Stir with a long-handled stirring rod. Leave the mixture to sit for more than eight hours or overnight to achieve optimal purity.
Pour the mixture, including the gold, through a fine filter into another container. It should change from a dirty brown to a clear emerald green. Filter the mixture until it turns this colour.
Add gold precipitant, such as ferrous sulphate or sodium bisulphate, to the mixture, and let it sit overnight or at least another eight hours. If gold is present, the mixture will turn purple.
Pour off the liquid until only a small amount containing the gold sludge at the bottom is left, then filter out the gold sludge to remove the remaining liquid.
Wash off the gold once again with hydrochloric acid and follow up with a water rinse. Filter and pour the gold into a mould to harden. The gold is now 99.9 per cent pure.
Gold refinement at home can be dangerous as you will need to work with chemicals and acids that produce noxious fumes. Make sure you refine the gold in a well-ventilated outdoor area if possible. Don't spend too much time near the gold while it is purifying. Wear safety clothes like gloves, goggles and thick clothes covering all of your body because the acids can burn and blister exposed skin.