Traveling waves in an extended reactor, whose width cannot be neglected, represent a three-dimensional (3D) reaction-diffusion-convection system. We investigate the effects of buoyancy-driven convection in such a setting. The 3D waves traveled through horizontal layers of the iodate–arsenous acid (IAA) reaction solution containing excess of arsenous acid. The depth of the reaction solution was the examined parameter. An increase in the intensity of buoyancy-driven flow caused an increase of the traveling wave velocities. Convection distorted the front of the chemical waves. For layers deeper than $h>13$ mm, heat release became smaller than heat production causing the emergence of Rayleigh-Bénard convection cells. At the interface, a dependency of wave shape on solution depth was observed. For $h<7$ mm, the waves adopted a stable $\mathsf{V}$-like shape, while for $h>13$ mm a parabolic shape dominated. For $7<h<13$ mm, both shapes were realized with the same probability. Finally, an intermittent switch between stoichiometric regimes is observed as an unexpected effect of the buoyancy-driven convection. The switch is expressed by iodine enrichment in the product. Hence, the experiments demonstrate that the buoyancy-driven convective flow can cause long-lived, but nevertheless transient, changes in the chemical composition by inducing a local transition between different regimes of the IAA reaction.

• Received 1 July 2011

DOI:https://doi.org/10.1103/PhysRevE.85.036303