PERIODIC CONVECTION IN THE BROMATE-SULFITE REACTION - A JUMPING WAVE

An unusual spatiotemporal phenomenon was observed in propagating front s in the bromate-sulfite system with an initial pH gradient, but not i n chlorate-sulfite nor iodate-sulfite systems. Periodic acceleration a nd deceleration of the front were observed, which appeared as a ''jump ing'' wave. An experimental method was developed to produce the pH gra dient systematically and reproducibly in a tube. The effect of the gra dient was studied. With the use of infrared and visible imaging the co mpetition between chemically and thermally induced convection was obse rved. A qualitative model is proposed that includes the effect of pH g radient and the specific mechanism of the bromate oxidation of sulfite .