Refining and production

The operation of refining can be performed in different ways depending on the gold content of the alloy, the securities exceeding 700 ° / ° ° been done by an attack with aqua regia.

The rods are subjected to hone initially melted in the crucible, then the molten metal is poured into a tank of water where it solidifies in the form of flakes. These are placed in a tank and dissolved with aqua regia (a mixture of hydrochloric acid and nitric acid in a 3:1 ratio), at the beginning of cold and followed by heating, this operation takes about three hours.

After the reaction the whole is left to cool, and then the liquid is filtered under vacuum and poured into a tank where, under a hood, the precipitation of gold is carried out by addition of bisulfite.? The mechanical ventilation hood is essential for the evacuation of sulfur dioxide that develops during the operation of reduction of gold chloride, such operations must always be carried out according to the criteria necessary for pollution abatement processes.

The part of the liquid that remains in the bottom of the vessel with the gold precipitate is filtered under vacuum. The gold remained on the filter is subjected to several washes with water and then, with a title of 999.9 ° / ° ° proceeds with the fusion to obtain an ingot.

Pure gold recovered with this system can be put back on the market and the cycle resumes.