DYNAMIC INSTABILITY AND LIGHT-INDUCED SPATIAL BIFURCATION OF HGI2 AND EXTERNAL ELECTRIC-FIELD EXPERIMENTS IN 2-DIMENSIONAL GEL MEDIA

New results on two-dimensional propagation of a single red/yellow wave of mercuric iodide in gel media in batch, continuous-flow, and gel-ring reactors are reported. The influence of electrolyte concentrations, temperature, thickness of the gel, and type of the reactor on the kinetics of wave propagation has been studied. Light-induced spatial bifurcation of yellow wave into alternate yellow and red bands is observed at low pH of the gel containing mercuric chloride. Experiments to study the precipitation pattern and crystal growth on a thin film of agar-agar gel sandwiched between microslides were carried out. Rhythmicity was observed during red-wave propagation at low [KI]. A new type of continuous-flow reactor has been designed to carry out experiments in the presence of an external electric field. Transitions from yellow to red and red to yellow forms have been observed in the presence of an external electric field. A critical field intensity at 0.283 V cm-1 exists at which the yellow form changes into a red variety.