Zur photometrischen Bestimmung kleiner Selenmengen

Summary Selenium(IV) or selenium(VI) is reduced in hydrochloric acid solution by means of chromium(II) to hydrogen selenide, which is passed into alkaline [Fe(CN)₆]^3– solution in a stream of nitrogen to be oxidized there to selenium(IV). 6 mol of [Fe]CN₆]^4– are formed per 1 mol of selenium. The latter reacts with iron(III) in the presence of 1,10-phenanthroline or bathophenanthroline-disulphonic acid to their Fe(II) complexes. The extinction coefficient for the determination of selenium is 68030 or 135700 1 · mol^–1 · cm^–1, respectively.