Wohlwill process

Abstract: PROBLEM TO BE SOLVED: To produce specific high purity gold by obtaining electrodeposited gold by a Wohlwill process using gold of specific purity as a raw plate for anode and subjecting the electrodeposited gold to vacuum melting to obtain primarily cast gold, then subjecting this primarily cast gold again to vacuum melting thereby obtaining secondarily cast gold. SOLUTION: The electrodeposited gold is obtd. by the Wohlwill process using the gold of purity 99.99% as the raw plate for anode. The electrodeposited gold is then vacuum melted to obtain the cast gold and this cast gold is vacuum melted again, by which the high purity gold of the purity >=99.9999% is produced. The electrolytic refining by the Wohlwill process is executed with 60 to 100 kg/m Au as an electrolyte, 50 to 200kg/m HCI, 60 to 85 deg.C as electrolytic temp., 200 to 900 A/m as a current density, 0.2 to 1.0 V as a cell voltage and a rolled gold plate as cathode. As a result, an impurity content decreases down to about 10 ppm. The impurity content may be decreased down the <1 ppm by two times of vacuum melting and casting of this electrodeposited gold, by which the high purity gold of the purity 99.9999% may be obtd. The melting temp. is preferably kept at 1,100 to 1,250 deg.C and the vacuum degree at <=80 Torr.