Extraction of zinc and lead from their sulfides

Abstract From the Canadian patent

Sulfidic ores of lead or zinc such as galena or sphalerite are smelted under vacuum in the absence of CO2 and oxygen with a flux consisting of solid NaOH or KOH to free the lead or zinc as free metal and to form sodium or potassium disulfides which are used as flux in smelting additional sulfidic ores to liberate more metal and form still higher polysulfides of sodium or potassium also usable as flux up to the pentasulfide form. By the process of the invention, substantially complete use is made of the sulfur atoms initially combined with the lead or zinc to remove the sulfur combined with said metals. Potassium hydroxide its lower sul-, fur content polysulfides can be reconstituted by …