EXPLANATION OF THE LONG-LIVED OSCILLATIONS IN THE CHLORITE ION-IODIDEION-MALONIC ACID SYSTEM

Long-lived oscillations in the chlorite ion-iodide ion-malonic acid sy stem and in its derivatives, ClO2-I-2-malonic acid and ClO2-Cl--iodoma lonic acid systems, are shown to proceed according to a general type c hlorite-controlled mechanism. The slow reduction of ClO2 serves as a c ontinuous source of ClO2-. The moderately fast equilibrium between iod omalonic acid and a reactive intermediate (R) maintains a steady conce ntration of R at around 10(-6) M during a significant part of the osci llatory cycle. Autocatalytic oxidation of R with ClO2- takes place acc ording to the general model of chlorite-based oscillators. The key to the oscillation is that, at a critical value of [ClO2-],the autocataly tic oxidation becomes faster than the equilibrium and both R and ClO2- are used up, Model calculations as well as experiments in a semibatch reactor have verified this explanation. A dual effect (inhibition-ind uction) of Cl- on oscillations suggests that ICI or I-2 can be the cru cial intermediate.