Kinetics of the Reduction of Selenious Acid by Sulfur Dioxide. II. Reduction in Acidic Solution with Sulfuric Acid

Abstract

Abstract (1) The reduction of selenious acid in sulfuric acid by sulfur dioxide is a reversible reaction, because the reaction has an equilibrium and the process of the reaction is in good accordance with the equation which expressed mathematically the reversible reaction, that is, −d(a−p)⁄dt=dp⁄dt=k2(a−p)2−k2′p2 (2) Up to the present time the rate constant k2 of the forward reaction was derived by substitution of the experimental data for xmin the following equation, k 2={2.303xm⁄2a(xm−1)t}×log[(x−xm)⁄{(2xm−1)x−xm}] The general equation for k2, which does not depend on xm, has been obtained as follows, k 2′=2.054×1015×[H+]2×exp(−E⁄RT)(E=22.5 kcal.⁄mol.) The rate constant k2′ of the reverse reaction can be calculated by k 2′=2.413×10−11×{1⁄(a2[H+]2)}×exp(−E⁄RT) (E=−8.06kcal.⁄mol.) (3) It has not previously been reported that α selenium is dissolved in dilute sulfuric acid (below 85% by weight), as shown by the present experimental procedure. (4) The results obtained from this study are useful in the recovery and refinining of selenium. Then application to the recovery and refining of selenium will be expressed in another succeeding paper.