RI 6277 Determination Of Copper In Tungsten Metal And Tungstic Oxide

A combined solvent extract ion-spectrophotometric method for the determination of as little as 1 ppm of copper in tungsten metal or tungstic oxide has been developed and evaluated. Metallic samples are converted to tungstic oxide by treatment with hydrofluoric and nitric acids. The oxide is then dissolved in sodium hydroxide, and the copper is extracted as the colored neocuproine complex. Total elapsed time for the analysis is approximately 1-1/2 days; however, actual working time for a group of six or eight determinations is less than 4 hours. Precision at the 2-ppm level is better than 0.1 ppm.