To refine gold using fire, place gold scraps in a crucible, and put the crucible in a burning furnace heated to 2,000 degrees. Once the gold melts, pour it into a separate container where all of the impurities and metals float to the surface and can then be skimmed from the top.
Using fire as a form of purifying gold is one of the oldest techniques, mentioned even in the Bible. Though it is an effective method, it is not the only method. Acid and electricity are also used to purify gold. Hydrochloric and nitric acid are used to remove impurities from gold. By mixing the two acids in a beaker they create a purifying solution. Before the gold is added, they are filtered. Once the two acids are filtered and come in contact with the gold, any substances in the gold ore or other impurities are removed.
The electric Wohlwill method of purifying gold is considered the most successful and the most expensive. In this process, the gold is placed in a mixture of gold chloride and hydrochloric acid. An electric current then passes through the solution, separating the impurities from the gold, which will then settle on the bottom of the container, ready for removal.