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Zoingeroing (talk | contribs) Changed the purity resulting from the Miller process to 99.5%, which is the figure stated by https://doi.org/10.1002%2F14356007.a12_499 and by Miller process |
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{{Short description|Industrial procedure used to refine gold}}
The '''Wohlwill process''' is an industrial-scale chemical procedure used to refine [[gold]] to the highest degree of purity (99.999%).<ref name=":0">{{Ullmann |doi=10.1002/14356007.a12_499|title=Gold, Gold Alloys, and Gold Compounds|year=2000|last1=Renner|first1=Hermann|last2=Schlamp|first2=Günther|last3=Hollmann|first3=Dieter|last4=Lüschow|first4=Hans Martin|last5=Tews|first5=Peter|last6=Rothaut|first6=Josef|last7=Dermann|first7=Klaus|last8=Knödler|first8=Alfons|last9=Hecht|first9=Christian|last10=Schlott|first10=Martin|last11=Drieselmann|first11=Ralf|last12=Peter|first12=Catrin|last13=Schiele|first13=Rainer|isbn=3527306730}}</ref> The process was invented in 1874 by [[Emil Wohlwill]]. This [[electrochemistry|electrochemical]] process involves using a cast gold [[ingot]], often called a [[Doré bar]], of 95%+ gold to serve as an [[anode]]. Lower percentages of gold in the anode will interfere with the reaction, especially when the contaminating metal is silver or one of the [[platinum group]] elements. The [[cathode]]s for this reaction are small sheets of pure (24k) gold sheeting or stainless steel. Current is applied to the system, and [[electricity]] travels through the [[electrolyte]] of [[chloroauric acid]]. Gold and other metals are dissolved at the anode, and pure gold (coming through the chloroauric acid by ion transfer) is plated onto the gold cathode. When the anode is dissolved, the cathode is removed and melted or otherwise processed in the manner required for sale or use. The resulting gold is 99.999% pure, and of higher purity than gold produced by the other common [[refining]] method, the [[Miller process]], which produces gold of 99.
For industrial gold production the Wohlwill process is necessary for highest purity gold applications. When lower purity gold is required, refiners often utilize the Miller process for its relative ease and quicker turnaround times and because it does not require a large inventory of gold, in the form of chloroauric acid.<ref name=r1/><ref name=r2/>
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