Double-diffusive convection in traveling waves in the iodate-sulfite system explained

Keresztessy et al. investigated traveling fronts of the oxidation of sulfite by iodate and determined that the isothermal density changes (Delta 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 fact, curved descending fronts with velocities greater than the ascending ones and ''fingering'' were observed. We have found that the diffusion coefficient of sulfuric acid is sufficiently larger than those of the other species to cause double-diffusive convection. We confirmed this by performing experiments with layers of solutions composed of components of the reactive system. Thus, the Pojman-Epstein model is upheld.