Iodometric Determination of Major Amount of Selenium in Complex Se-bearing Materials

Iodometry was applied to the determination of major amount of selenium in complex Se-bearing materials and optimum conditions for the determination were studied. The sample was dissolved in HNO3 and fumed with H2SO4. The salts were dissolved in HCl. Selenium ion in the solution was reduced to elementary state by hydroxylamine hydrochloride in the presence of tartaric acid at 70 ℃ for 1 h and aged for 1.5 h. After filtering, the elementary selenium was dissolved with HCl at 90 ℃ for 5 min. Suitable acidity of the solution for iodometric titration was found between 0.2-0.5 mol·L-1 (in HCl). The mode of stepwise-addition of KI solution was adopted and titration with Na2S2O3 standard solution was carried out after each addition of KI solution until no blue color of the starch indicator appeared. Content of Se in the sample was calculated from the volume of Na2S2O3 standard solution consumed.