title: Determination of cobalt and zinc in highpurity niobium, tantalum, molybdenum and tungsten metals by atomicabsorption spectrophotometry after separation by extraction.
abstract: A method for determining 0.0005-0.05% of cobalt and zinc in high-purity niobium, tantalum, molybdenum and tungsten metals by atomic-absorption spectrophotometry is described. After sample dissolution, cobalt and zinc are separated simultaneously from the matrix materials by chloroform extraction of their thiocyanatediantipyrylmethane ion-association complexes, at pH 3.25, from a citric acid medium approximately 1.2M in sodium thiocyanate. Interference from copper is eliminated with thiourea. Large amounts of iron interfere under the recommended conditions, but moderate amounts may be present in the sample solution without causing appreciable error in the results. Phosphorus (as orthophosphate) interferes in the extraction of cobalt from tungsten solutions. Moderate amounts of other impurities do not interfere in the proposed method.
authors.affiliation: Mineral Sciences Division, Department of Energy, Mines and Resources, Mines Branch, Ottawa 4, Ontario, Canada.
authors.forename: E M
authors.initials: EM
authors.lastname: Donaldson
authors.forename: D J
authors.initials: DJ
authors.lastname: Charette
authors.forename: V H
authors.initials: VH
authors.lastname: Rolko