PHOTOINDUCED BIFURCATION BETWEEN STEADY AND OSCILLATORY STATES IN THEFE(CN)(6)(4-)-H2O2 REACTION IN A FLOW REACTOR

The photoinduced bifurcation structure in the Fe(CN)(6)(4-)-H2O2-H2SO4 system in a continuous-flow stirred tank reactor has been determined. The photo-induced transition between the low-pH steady state and the oscillatory state shows a hysteresis, similarly to the dark reaction r eported previously. The action spectrum for the photoinhibition of osc illations suggests that the primary light absorber in the visible regi on is Fe(CN)(6)(3-), similarly to the photoinduction of oscillations r eported previously, while in the UV region Fe(CN)(6)(4-) is also activ e. The primary photochemical processes are shown to be the following: Fe(CN)(6)(4-) + H2O reversible arrow(h upsilon) Fe(CN)(5)H2O3- + CN- a nd Fe(CN)(6)(3-) + H2O reversible arrow(h upsilon) Fe(CN)(5)H2O2- + CN -. The state diagram spanned by the irradiation light power and the fl ow rate as external control parameters is presented, on the-basis of w hich the mechanism of oscillations is discussed qualitatively.