SYSTEMATIC DESIGN OF CHEMICAL OSCILLATORS .67. EXPERIMENTAL AND MODELING STUDY OF OSCILLATIONS IN THE CHLORINE DIOXIDE IODINE MALONIC-ACID REACTION

At pH 0.5-5.0, a closed system containing an aqueous mixture of chlorine dioxide, iodine, and a species such as malonic acid (MA) or ethyl acetoacetate, which reacts with iodine to produce iodide, shows periodic changes in the light absorbance of I3-. This behavior can be modeled by a simple scheme consisting of three component reactions: (1) the reaction between MA and iodine, which serves as a continuous source of I-; (2) the reaction between CIO2- and I-, which acts as a source of CIO2-; and (3) the self-inhibited reaction of chlorite and iodide that kinetically regulates the system. The fast component reaction between chlorine dioxide and iodide ion was studied by stopped-flow spectrophotometry. The rate law is-[CIO2*]/dt = 6 × 103 (M-2 s-1)[CIO2][I-). A two-variable model obtained from the empirical rate laws of the three component reactions gives a good description of the dynamics of the system. The oscillatory behavior results not from autocatalysis but from the self-inhibitory character of the chlorite-iodide reaction. © 1990, American Chemical Society. All rights reserved.