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Oxidation reaction: The oxidant reacts with impurities such as copper, lead, zinc, iron to form a metal oxide, and reacts with sulfur to form a gas.
6Cu+2NaNO 3 â•Cu 2 O+Na 2 O+2NO
3Me+2NaNO 3 â• 3MeO+Na 2 O+2NO
(The above formula uses saltpeter as oxidant and Me as Zn, Pb, Fe, etc.)
S+2NaNO 3 ╠Na 2 O+2NO+SO 3 ↑
Slag formation reaction: the slagging flux reacts with the metal oxide to form slag.
mMeO+nSiO 2 â• mMeO nSiO 2
mMeO+nNa 2 B 4 O 7 â• mMeO nNa 2 O 2nB 2 O 3
(In the above formula, respectively of silica sand and a boron slagging flux)
Since the slag density is only 2 to 3 g / cm 3, the density ratio of gold and silver (gold 19.32 g / cm 3, 10.5 g of silver / cm3) is much lower, the process of smelting slag will float in the upper layer is excluded.
The basic principle of pyrometallurgy
Fire refining is gold and the gold flux material (oxidizing agent and slagging) are mixed, then placed fire Alchemy furnace smelting at a temperature of 1200 ~ 1350 ℃ to obtain gold and silver alloy. Smelting, impurities such as copper, lead and zinc flux (flux slag and oxidizing agent) and generating slag oxidation reaction: