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    STUDIA CHEMIA - Issue no. 1-2 / 2001  
         
  Article:   SPECTROPHOTOMETRIC DETERMINATION OF TUNGSTEN (V) AS THIOCYANATE COMPLEX IN CERTIFIED STEEL MATERIALS.

Authors:  FRENŢIU TIBERIU, MICHAELA PONTA, EMIL CORDOŞ.
 
       
         
  Abstract:  The method is based on the photometric determination of tungsten (V)-thiocyanate complex (420 nm, absorptivity coefficient 35 l g-1 cm-1) after the reduction of W(VI) with SnCl2 and TiCl3. The method was applied to determine W in steel samples dissolved in Speacker reagent. The kinetics of the complex development and the interference of Mo on W determination were studied for ratios of Mo:W up to 2:1. The calibration curve was linear in the range 5-25 g ml1 W, with a correlation coefficient of 0.994 (n=5) and a detection limit of 1g ml-1 W. For a certified content of 17.7% W in steel, the recovery was 992% and the relative standard deviation 2% (n=5). The method allows the determination of W in the presence of Mo up to a Mo/W ratio (m/m) of 1/2.  
         
     
         
         
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