What is the refining process for achieving 999 and 999.9 fine gold?
The Royal Canadian Mint, for example, uses a two-stage process to refine gold to 999 and 999.9 fine. The process begins with the Miller chlorination process, which refines the gold to 99.5% purity. Then, the Wohlwill electrolytic process is used to achieve purities of 99.99% or higher.