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The reaction of bromate, sulfite, and ferrocyanide ions in a continuous stirred tank reactor (CSTR) exhibits sustained oscillations at temperatures of 20, 30, and 40 O C . The oscillations, the behavior in a closed (batch) system, and the observed bistability in a CSTR are all in excellent agreement with simulations using a nine-step mechanism in which the reaction of BrO,-with Fe(CN)6& plays a key role. The relationship between the present system and the 'mixed Landolt" oscillator, in which bromate is replaced by iodate, is discussed. IntroductionWith the Belousov-Zhabotinskii (BZ) reaction serving as the prototype, bromate oscillators3 have played a dominant role in the study of chemical oscillation. They have provided a fruitful ground for mechanistic studies starting with the classic FieldKoros-Noyes (FKN) mechanism4 and have also served as prime examples of how, given a general mechanistic understanding of the parent system, one may generate new oscillators by well-chosen modifications of an existing oscillating r e a c t i~n .~Here we investigate the reaction of bromate, sulfite, and ferrocyanide ions. The present system is derived from the iodatesulfite-ferrocyanide oscillator recently discovered by Edblom, OrbBn, and Epstein (EOE)6 by replacing the iodate ion of that "mixed Landolt" reaction by bromate. As anticipated, we do indeed obtain oscillatory behavior in a continuous stirred tank reactor (CSTR), though that behavior differs from that of the iodate system in several unforeseen ways. We have also studied the mechanism for this system and find that it must depart significantly from that p r o p o~e d~.~ for the analogous iodate reaction

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The kinetics of decomposition of aqueous chlorous acid has been reinvestigated at pH 0.7-1.9, ionic strength 1.0 M (HSO 4 -/SO 4 2-), and temperature 25.0 ( 0.1°C. Optical absorbances were collected in the 240-450 nm wavelength range for up to ∼90% decomposition for time series lasting as long as 2 days. The number of absorbing species was investigated by matrix rank analysis; no absorbing intermediate was formed in significant concentration during the decomposition. Of the many mechanistic models tested, the one that fit best included the following reactive intermediates: HOCl, explains the variation in stoichiometric ratio as well as the maximum observed in the initial rate of ClO 2 formation as a function of pH. The kinetics of chlorous acid decomposition cannot be quantitatively fit through the last stages of the reaction without postulating a first-order decomposition. Scission of chlorous acid to give short-lived hydroxyl and chlorine-(II) monoxide is a plausible route for this process. A set of best-fit and literature-derived parameters is presented for the complete mechanism.