NEW INDICATORS FOR VISUALIZING PATTERN-FORMATION IN UNCATALYZED BROMATE OSCILLATORY SYSTEMS

Many uncatalyzed bromate oscillators (UBO's) undergo oscillations in e lectrochemical potential without any observable color change in a clos ed, stirred (batch) system. We have investigated the effects of adding a wide variety of redox indicators, including diphenylamine derivativ es, azo dyestuffs, triphenylmethane derivatives, diimine chelate compl exes, and methylene blue to UBO's. We find that in many cases the indi cators make the batch oscillations strikingly visible and also allow o bservation of spatial pattern formation (concentric rings and spirals) in a thin, unstirred layer of solution. In some systems, the indicato rs act merely to make visible changes in redox potential, while in oth ers they play an active role in the chemistry, and added indicator can lengthen the duration of oscillations or regenerate oscillations or p atterns once this behavior has ceased.