Solvent extraction procedure for the determination of tungsten in ores

Introduction -- Procedure -- Analysis of tungsten ores -- Experimental --Acknowledgment -- References.Atomic absorption methods have not been widely used for the determination of tungsten in ores due to its low sensitivity in aqueous solutions (1). A method has now been developed for solvent extraction of tungsten, making rapid determination of tungsten at low concentrations possible. It was found that tungstates, when converted to phosphotungstates, can be effectively extracted into di-isobutyl ketone (2-6 dimethyl - 4 - heptanone) (DIBK) containing Aliquat 336 (methyl tricapryl ammonium chloride from General Mills). This system was effectively used for the extraction of gold from cyanide solutioins (2). Even in aqueous solutions, phospho-tungstates give greater sensitivity (37 µg/ml for 1% absorption) compared to simple tungstates (63 µg/ml for 1% absorption). Standard tungsten solutions for extraction studies were prepared by converting aqueous solutions of sodium tungstate to sodium phospho-tungstate by boiling with ortho phosphoric acid. A Perkin-Elmer Model 303 atomic absorption spectrophotometer was used with a nitrous oxide-acetylene flame at a wavelength of 4008.75 A