Refining gold to highest degree always require two step purification. It is virtually impossible to refine gold to 99.99% and better quality in a single step when your starting material is less then 95% purity, regardless what different manufacturers are claiming. In real life most of the time gold from low grade feed material will be refined to 98% - 99.5%, depending on composition.
For high purity refining Wohlwill process is used as a second step. With feed material over 98% this protocol is capable to provide 99999 purity.
For refining to 99999 purity we are offering two step gold refining systems that will produce extremely high grade gold, where first step is carried out in our regular REFINEIT system, and for second step Wohlwill process system is used.