Wohlwill

Wohlwill commonly refers to the Wohlwill process, an electrochemical method for refining gold. Named after the German electrochemist Emil Wohlwill, the process was developed in the late 19th century and has become a standard technique in the gold refining industry for achieving exceptionally high purity.

Principle and procedure: The refining cell uses an anode of impure gold and a cathode of pure gold. The electrolyte is a concentrated solution of chloroauric acid (gold chloride) in hydrochloric acid. On application of electric current, gold from the anode dissolves as AuCl4− and is deposited on the cathode as high-purity gold. Impurities either dissolve into the electrolyte or remain as insoluble anode slime at the bottom. The method can yield gold of about 99.999% purity (five nines). The process is typically slower and more expensive than other refining methods, but it produces superior purity.

Applications and significance: The Wohlwill process is widely used by major gold refiners to produce high-purity bullion and materials for electronics, dentistry, and investment. It is often employed for final refining after initial purification by other methods, such as the Miller process, which is faster and cheaper but yields lower purity. The Wohlwill process remains a benchmark for achieving the highest available gold purity.