REFINING
Aqua Regia Refining | Electrolytic Gold Refining Plants
Electrolytic Silver Refining Plants
THE AQUA REGIA METHOD
The aim of the refining process is to obtain gold of a purity not less than 999,5‰ from scraps from jewelry bench work, recovered material or mining activities.
The refining technique involved in BALESTRI IMPIANTI plants is based on chemical method whereby the gold-bearing scrap is dissolved in aqua regia, a mixture formed by nitric acid and hydrochloric acid, usually in a volumetric ratio of 1:3. It was so named because it can dissolve the so-called "royal metals", or noble metals, gold and platinum.
It is important to to assay the alloy that will be refined, in order to know the quantity of silver and gold. Standard rate for the aqua regia tecnique are:
Gold (AU) not less than 650‰
Silver (AG) not more than 100‰
THE ELECTROLYSIS METHOD
The electrolytic refining technique consists in the dissolution of an impure gold anode into an electrolyte solution. Impure gold is cast into an anode, while the cathode is a thin strip of pure gold.
By passing an electric current from anode to cathode through the electrolyte solution, the anodes are gradually dissolved and the gold therein is deposited on the cathodes; any silver is precipitated as insoluble silver chloride along with any platinum metals present.
The gold-coated cathode is removed, melted and cast into bars.
Balestri Impianti designs, produces and installs chemical plant for the goldsmith industry: gold refining, silver refining, precious metal recovery, gold electrolysis, silver electrolysis, gold recovery, precious metal analysis, cupellation furnaces, partition hoods, assay, chemical brightening (bombing), emptying, hollowing, fumes scrubbing.
