Determination of Iron, Nickel, Copper, and Cobalt in Tungsten and Tungsten Alloys

摘要

Iron, nickel, copper, and cobalt in tungsten and tungsten alloys are analyzed spectrophotometrically by taking aliquots of a hydrofluoricnitric acid solution that has been buffered to a pH of 6 by the addition of ammonium tartrate and sodium borate. No subsequent adjustment of pH is necessary for the spectrophotometric determination of the iron, copper, or cobalt. The iron is determined with ortho-phenanthroline, the nickel with dimethylglyoxime (using an ammoniacal medium for trace amounts and an ammoniacal-sodium hydroxide medium for large amounts), the copper with neocuproine, and the cobalt with nitroso-R salt. Large amounts of iron are determined titrimetrically after sodium hydroxide and ammonium hydroxide precipitations. A direct method for the gravimetric determination of large amounts of nickel in tungsten with dimethylglyoxime by use of the ammonium tartrate-sodium fluoborate buffer system is described. Copper is determined electrolytically after dissolution in hydrofluoric and nitric acids and addition of hydrogen peroxide. Large amounts of cobalt are determined potentiometrically with potassium ferricyanide. (Author)