Spectrophotometric Determination of Tetrathionate by Its Oxidation with Iodate.

概要

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The conditions under which tetrathionate is oxidized stoichiometrically to sulfate by iodate have been established by investigating the reaction rate of tetrathionate with iodate in a medium containing varying amounts of sulfuric acid at room temperature and 40 °C. Tetrathionate reacted with iodate with a tetrathionate: iodate mole ratio of 3 : 7 under the conditions of the usual procedure. After a complete reaction, the iodine, formed from excess iodate by the addition of iodide, was spectrophotometrically measured as triiodide. A 14-fold chemical amplification was achieved for the determination of tetrathionate by using the proposed method, compared with the conventional methods via the sulfitolysis and cyanolysis of tetrathionate. A linear calibration graph with a negative slope was obtained over the concentration range 2.5×10−7–2.5×10−5 mol dm−3 tetrathionate (0.5–56 μg of S4O62− in 10 cm3); the relative standard deviation was 0.42% at the 1.5×10−5 mol dm−3 tetrathionate level.
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