QUENCHING OF OSCILLATIONS IN THE PERMANGANATE-HYDROXYLAMINE REACTION

Perturbation experiments on small-amplitude oscillations of the MnO4-- NH2OH-H3PO4 system are reported. We show that the oscillations arise f rom a stable stationary state by a supercritical (i.e. continuous) Hop f bifurcation, and demonstrate that the oscillations can be quenched ( temporarily stopped) by addition of small amounts of either of the spe cies Mn2+, OH-, or colloidal MnO2 at specific phases. Characteristic t imes exceeding two hours are observed for the return to the limit cycl e oscillations from successful quenchings. Remarkably, this is more th an 40 times the residence time of the flow system. The work is the fir st part of a study aiming at developing a model of the complicated per manganate oscillator, including a determination of the rate constants of the reactions taking place.