Abstract: A method for refining noble metals has a silver treating process including a nitric acid leaching step of silver, a purification step of the leaching solution, an electrolytic decomposition step of silver, and a recycling step after the electrolytic decomposition, wherein in the purification step, lime is added in order to precipitate the metallic impurities, such as selenium, tellurium, bismuth, and copper, by neutralization of the leaching solution, and in the recycling step, sulfuric acid is added to the solution after electrolytic decomposition to regenerate nitric acid for recycling use by precipitation of calcium in the solution as gypsum. Preferably, the refining method has a gold recovery process, as well as the silver treating process, wherein the residue of the nitric leaching of the crude silver is dissolved by chlorination and gold is recovered from the leaching solution by solvent extraction or reductive precipitation.

Abstract: There is disclosed a continuous direct process of lead smelting comprising a step of blowing a compounded feedstock by means of an oxygen-enriched air or oxygen into a smelting zone containing a molten lead bath with a blast pressure by which the compounded feedstock can penetrate into the molten lead bath, at a temperature at which the oxidation reaction of the lead sulfide concentrate can be sustained, said feedstock containing particulate or powdered lead sulfide concentrate and a flux and further containing a fuel when oxygen-enriched air is used, whereby the lead sulfide is oxidized to form crude lead and slag; and a step of transferring the molten crude lead and the slag formed in said first step to a reduction zone, where the slag is contacted with a reducing agent so as to reduce the lead substances in the slag and return the reduced lead to the crude lead.