The anode sludge is collected, drained and washed with distilled water from time to time and the washing from the sludge are returned to the electrolytic bath to compensate the loss of water which constantly occur due to the temperature of the electrolyte. It is important to maintain the electrolyte at a uniform level, notwithstanding the loss due to evaporation, a closed reservoir container containing fresh electrolyte is usually installed above the electrolytic cells in order to provide electrolyte. With a 16” thick anode and current density of 40 amp/ft2, the anode is consumed to approximately one-tenth of the initial weight. Then is removed, washed, remelted and employed to make new anodes.
If the hydrochloric acid is not present in the electrolyte, chlorine is released at the anodes and very little gold is dissolved. If low current density is utilized, a larger weight of gold is deposited on the cathode. However, when high current density is used, the weight deposited is not high. This situation is produced because with low current density, aurous compounds are easily treated electrolytically and with high current densities, auric compounds are partially decomposed, approximately 33% reacts and the remaining parts stay in steady state. However, operation is performed with high current densities due to when low current density is used; part of gold is precipitated in the sludge. Other reason is based in the fact that would be necessary to make heavy anodes to compensate the inefficiency of the process.
It is important to mention that the separation between anode and cathode is not more than 30 mm and there is no danger of short circuit due to metallic growths at the cathode. At the beginning of the process the electrolyte is solution of auric chloride with hydrochloric acid and the cathode deposit is not firmly adhered on the cathode surface. The deposit is less dense if the soluble impurities from the anode contain chlorides of lead, platinum and other metals.