PURPOSE:To recover gold and silver at a good yield by adding an alkali to an aq. soln. contg. thiourea compd. of gold and silver to specific pH in the presence of iron ion and separating the formed precipitate. CONSTITUTION:An alkali hydroxide and potassium carbonate or calcium carbonate are added to an aq. soln. contg. thiourea compd. of gold and silver to adjust the pH thereof to =6.5 without adding ferric sulfate or ferric chloride thereto if the substantial amt. (about 10-100 times the gold) of trivalent or vivalent iron ion exists or after adding preferably a suitable amt. of ferric fulfate or ferric chloride thereto if the soln. contains the iron ion in the smaller amt. The soln. is preferably aerated to adjust the pH to =4.0. The precipitate formed by such addition is separated by a filtering and washing method or the like by which gold is recovered directly at an actual yield of about 90-92wt% and silver at about 90-95wt%.
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