TRAVELING WAVES IN THE IODATE-SULFITE AND BROMATE-SULFITE SYSTEMS

We investigated traveling fronts of the oxidation of sulfite by iodate and by bromate. Isothermal density changes (Delta rho(c)) and enthalp ies were determined, the latter being negative in both cases. The Delt a rho(c) is negative in the iodate-sulfite system but positive in the bromate-sulfite system. Double-diffusive convection was expected in th e bromate system and was observed. The effect of tube diameter and the orientation of the tube on the wave velocity and wave shape were stud ied, and a gravitational anisotropy was found in both systems. Accordi ng to the Pojman-Epstein model, only simple convection should have occ urred in the iodate-sulfite system. In fact, curved descending fronts with velocities greater than the ascending ones and ''fingering'' were observed. Several explanations were considered, including the possibi lity that the current model must be expanded to explicitly treat the e ffect of a moving interface on the stability of the fluid.