A sheet of pure copper (99.9% pure) is placed on the other side of the tank which acts as the cathode (the negatively charged electrode). When the power is turned on, the copper sulfate poured into the tank acts as an electrical conductor that allows the copper to pass from the positively charged anode to the negatively charged electrode and the copper particles slowly accumulate on the cathode (see diagram on page 5). . Approximately 14 days later the anode disappears since the copper has been deposited on the cathodes making 99.9% copper. The impurities that were on the anode do not become ions in the copper sulfate but rather fall out as a viscous material containing small amounts of gold and silver. These precious metals are extracted and allow the by-products to be used more efficiently rather than thrown away. Thanks to the fact that copper is very unreactive, the metal remains pure for a very long time.