Abstract:
We report experiments with novel features in periodic precipitation (Liesegang banding), in Mg(OH)2 systems. Experiments in the absence of an electric field yield a set of white rings consistent with the 1D observations reported in the literature. Concerted field experiments (in a positive field) widen the span of the pattern. Above a critical field strength, no bands are observed. This is wave annihilation, typical of chemical wave electric field interaction phenomena. The reversed (negative) field experiments produce a succession of white rings of unpredictably variable thickness, and unusual time sequence. The electric field plays an important role in taming the irregularity of the rings into an almost perfect circular symmetry. © 2010 Elsevier B.V. All rights reserved.