FLOTATION-SPECTROPHOTOMETRIC DETERMINATION OF GOLD IN GOLD ORE, ANODIC SLIME AND CYCLONE DUST USING IODIDE AND METHYLENE-BLUE

Gold in dilute hydrochloric acid and in the presence of an excess of iodide reacts with Methylene Blue (MB) giving a sparingly soluble ion associate [(MB+)(AuI2-)]. The ion associate is separated in a form of precipitate when an aqueous solution is shaken with cyclohexane. Gold is quantitatively floated at 1.5x10(-4) mol l-1 MB and above 1.5X10(-3) mol l-1 KI. The ion associate [(MB+)(I3-)] is floated simultaneously. Methanolic solutions of the ion associates separated obey Beer's law up to 1.0 mug Au in 1 ml. A molar absorptivity (epsilon) equals to 1.9X10(5) l mol-1 cm-1 (lambda(max) = 660 nm); a relative standard deviation (s(r)) is 1.5-1.8 %. Gold (at the level 10(-3)-10(-5) %) in ore, anodic slime and cyclone dust was determined with the developed method. The samples of gold ore and cyclone dust were preliminary treated with HF and HNO3; of anodic slime with H2SO4, HNO3 and CH3COONH4. Gold was extracted by ethyl acetate after dissolving in aqua regia.