Recovery of Gold from Electrolytic Solutions
It is possible the recovery of gold from electrolytic solutions. This is a situation that every electro-gilder, goldsmith and jewelers have to face and the most acceptable procedure is not clear due to the complexity of the bath. The recovery methods usually employed to recover gold from exhausted or spoilt cyanide solutions are either to evaporate the solution to dryness and then melt the residue or to precipitate gold by means of an acid. The first option is generally considered by refiners of precious metals and the second option is used in manufacturing and electro-gilding places.
A third option is to extract the gold from spoilt or exhausted solutions by trying to deposit the gold onto a piece of copper or other metals by means of electric current; but this alternative is slow and not very efficient because part of the remains in the cyanide solution. In this case the cyanide solution is not entirely decomposed and continues chemically united with a portion of the gold, and this prevents the latter from being completely deposited on the copper cathode. The anode is an insoluble substance such as platinum or carbon.
The process that needs to evaporate large quantities of solution is tedious and expensive, and also requires special equipment for the performance of the operations. With small volumes of solution it is much more readily accomplished. This procedure in any case is not totally satisfactory due to for bright gilding the solutions has to be done daily and a new solution has to be made every fortnight, for they become so loaded with foreign matter that their working properties for the bright finish become impaired and a new solution is necessary to produce to right finish. Also, the rinsing waters is other aspect to consider because there are some traces of gold in the liquid clinging to the articles as they are removed from the solution to the rinsing waters, and these waters will have to be treated for the extraction of gold as well as from the solution. They increase to large bulk and the gold they contain, though small in quantity is of high value, so that it pays to consider the best means available to perform its recovery; and to evaporate all this solution would prove on account of the time required to effect it an expensive operation, and one that cannot be performed by every electro-gilder or jeweler, as the cost would be greater than the value of the gold obtained from the bulk solution. Some smelting places are used to recover the gold from cyanide solutions, evaporate the liquid in iron pans until it becomes dry.
The evaporation residue is scraped out and the melted in a crucible, and the cyanide and sodium carbonate that is present in the residue acts as the flux for the fusion of the product and this is usually found sufficient as old electro gilding solutions contain very little gold. In this way, when the dry procedure is selected no other reducing salt is needed to be added to cause the mass to become thinly fluid to allow the small particles of gold passing through it and gathering together into a button at the bottom of the crucible. Sodium cyanide and sodium carbonate are excellent reducing agents and readily melt into a thin liquid molten charge.
- Dry Method to Recover Gold from Electrolytic Solutions
- Acid Method to Recover Gold from Electro-Gilding Solutions
- Precipitation of Gold using Acids
- Gold Precipitate from Electro-Gilding Solutions
- How to Melt the Gold Precipitate from Electrolytic Solutions
- Gold Recovery from Electro-Gilding Solutions by Applying Electric Current
- Gold Recovery using the Acid Zinc Process
- The Correct Zinc Sheet to Precipitate Gold