There are actually a few different methods of refining gold. Depending upon the quantity of gold you are working with and the desired level of purity, the two most common methods for refining gold are the use of high temperature flame and the use of chemicals to refine the gold.
Refining with flame is one of the oldest methods of refining metals. Mentioned even in the bible, refining by fire is the preferable method for larger quantities of gold. In ancient times, this form of refining involved a craftsman sitting next to a hot fire with molten gold in a crucible being stirred and skimmed to remove the impurities or dross that rose to the top of the molten metal. With flames reaching temperatures in excess of 1000 degrees Celsius, this job was definitely a dangerous occupation for the gold refiner. The tradition remains largely untouched today with the exception of a few advancements in safety and precision.
The second method of refining gold involves the use of chemicals. Strong acids are used to dissolve the impurities in the gold ore and afterwards, are neutralized and washed away, taking the impurities with them. The resulting product is a muddy substance that is almost pure gold (99.999% or 24K). This muddy substance is dried until it is a powdered residue and then heated with a torch or other source of heat to melt the gold powder into useable gold. The acids used for this process are Nitric acid and Hydrochloric acid.
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