DOUBLE-DIFFUSIVE CONVECTION IN TRAVELING WAVES IN THE IODATE-SULFITE SYSTEM EXPLAINED

Keresztessy et al. investigated traveling fronts of the oxidation of s ulfite by iodate and determined that the isothermal density changes (D elta rho(c)) and enthalpy were both negative. According to the Pojman- Epstein model, only simple convection should occur in this case unless two species have significantly different diffusion coefficients. In f act, curved descending fronts with velocities greater than the ascendi ng ones and ''fingering'' were observed. We have found that the diffus ion coefficient of sulfuric acid is sufficiently larger than those of the other species to cause double-diffusive convection. We confirmed t his by performing experiments with layers of solutions composed of com ponents of the reactive system. Thus, the Pojman-Epstein model is uphe ld.