Mechanism of the oscillatory decomposition of hydrogen peroxide in the presence of iodate ion, iodine etc.

Abstract

Various mechanisms are constructed with the aid of information on associated reactions and tested in the light of the theory of two-variable oscillating reactions as well as by means of computer simulations. Reactions were run mainly at [HClO₄]₀= 0.035 to 0.080, [KIO₃]₀= 0.40, and [H₂O₂]₀= 0.30 mol l.^–1 and compared with computer results for a promising mechanism. Agreement is so good with respect to the induction period, the pulses of [I^–] and the rate of O₂ evolution, the abrupt decrease in [I₂] etc. for one to conclude the mechanism to be plausible. The plausible mechanism contains HIO₂, HIO, I^–, H₂I₂O₃, and H₃I₃O₅ as intermediates and the second-order back-activation step 2HlO₂+ HIO + H₂O₂→ 3HIO₂+ H₂O as the key step for the oscillation, which results from the sequence of HIO₂+ HIO ⇌ H₂I₂O₃, H₂I₂O₃⇌ H₃I₃O₅, and H₃I₃O₅+ H₂O₂→ 3HIO₂+ H₂O. The oscillation source of the mechanism has been found to be in conformity with the Brusselator.