Effects of the Starch Indicator on the Buoyantly Unstable Iodate‐Arsenous Acid Reaction Front

Abstract

AbstractBuoyantly unstable chemical fronts, which propagated in the iodate arsenous acid reaction system, were studied experimentally in 3D space and numerically in vertical 2D space. The fronts invaded the reaction solution from the left top corner in horizontal and vertical directions. Before the starch effects were examined condition under which friction did not influence the front propagation were found both experimentally and numerically. The critical solution depth and the critical distance between lateral walls, above which the front speed is not influenced by friction, were determined. Moreover, the results also show that the 2D simulations correspond to a vertically oriented plane placed the 3D experiments in 1/2 of the walls distance and along the x axis of the reactor. Importantly, those results also show that friction caused by the presence of solid side walls exclude pseudo 2D experiments to be compared with 2D simulations, when flow is involved. The effects of starch on the IAA fronts were studied experimentally at conditions, at which the friction did not influence the front propagation. Although the starch is used in very low concentrations as an iodine indicator, the experimental results show that starch presence strongly affects the dynamics of the liquid IAA reaction system. The presence of starch decreases the front velocity independently on the direction of the front propagation. Starch also affects the pattern formation. A possible mechanism is discussed.