Oxidation of thiourea by iodate: a new type of oligo-oscillatory reaction

Abstract

In the oxidation of thiourea by iodate in weakly acidic solution the concentration of iodide may exhibit several extrema. The number of extrema mainly depends on the initial ratio of the concentrations of thiourea and iodate, and is at most four. The first step of the reaction results in the formation of iodide which then reacts with iodate to give iodine. The latter oxidizes thiourea in several steps, the end products being sulphate ions, ammonium ions, and carbon dioxide. Taking into account the independently determined rate constants for the sub-systems, the change in the concentrations of iodide and iodine with time can be calculated. There is good agreement between the experimental and theoretical curves.