CALORIMETRY AND POTENTIOMETRY OF CHEMICAL OSCILLATIONS IN BRIGGS-RAUSCHER REACTIONS WITH SIMULTANEOUS MEASUREMENTS OF THE PRODUCED OXYGEN VOLUME

The Briggs-Rauscher reaction is known as a nonlinear and non-equilibri um chemical oscillation reaction. The reaction solution is composed of malonic acid as organic substrate, hydrogen peroxide and iodate in su lphuric acid as oxidizing agent, and manganese (II) as metal catalyst. The calorimetric behaviour, in terms of the total heat Q and the heat evolving rate q for each chemical oscillation, was followed with the use of a heat exchange calorimeter of the batch type assembled by the authors. Simultaneously, the concentration of iodide ions produced as the intermediate species was measured as the potential difference E by the common potentiometric cell incorporated in the calorimeter and th e released oxygen volume G was also observed by a simple flowmeter. Th e starting point of the peak on the curve of q against time t coincide d with that in the curve of E against t. The switching concentration o f iodide between radical and nonradical paths was calculated from lite rature values of rate constants. The heat evolving period of Q coincid ed with the period in the radical path. The curve of Q against t also coincided with that of G against t. The total volume of released oxyge n was larger than that calculated from the stoichiometric reaction for mula.