The influence of molybdenum on thiocyanate spectrophotometric determination of tungsten was investigated. The error in determination of tungsten in molybdate-tungstate mixed solution was stated through analysing the absorbance-wavelength spectrogram of the thiocyanate colour solution. The results show that the determination error of tungsten > 17% to the solution with Mo/WO_3 (mass concentration ratio) > 3, as a result of the overlap of absorption peak of Mo-SCN~- and W-SCN~- complex. A calibration method was proposed, through which the determination error of tungsten was less than 5% to the solution with Mo/WO_3 < 15.
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