Size-Dependent Belousov−Zhabotinsky Oscillation in Small Beads

We examined chemical oscillations in the Belousov−Zhabotinsky (BZ) reaction with spherical ion-exchange resin beads (radius: 0.1−0.4 mm) loaded with a cationic catalyst, ferroin, in which no traveling wave appears and the oscillation is synchronized over individual beads. The period of the oscillation increases with a decrease in the size of the beads. Based on a theoretical consideration of the effect of the diffusion of active species through the surface of the bead reactor into the bulk aqueous solution, the following relationship was deduced: f /[H 2 SO 4 ] γ ∝ (1 − η/ R ) where f is the frequency (Hz) of the oscillation, R is the radius (mm) of the beads, [H 2 SO 4 ] is the concentration (mol/dm 3 ) of sulfuric acid, andγ and η are constants. This relationship was consistent with experimental results with values of γ = 1.4 and η = 7.4 × 10 -4 .