The effect of acetone and sulfuric acid concentrations on sequential oscillations in a modified Belousov-Zhabotinsky reaction

Oscillatory reactions are reactions where it is possible to measure oscillations on the concentration of some reaction intermediates. The original Belousov-Zhabotinsky (BZ) reaction is composed of sulfuric acid, bromate, malonic acid and cerium(IV). The reaction studied in this work is a variation of the original BZ reaction, where malonic acid is substituted by acetone and oxalic acid. Chemical oscillators may have different oscillation patterns and might show an induction period or even a break between oscillations (sequential oscillations). Variations on acetone concentration1 and temperature2 may cause the appearance of sequential oscillations on this system. Herein we report the effects of changes on acetone and sulfuric acid concentrations, in batch. The concentrations of oxalic acid (0.1 M), bromate (0.02 M), and cerium(IV) (0.001 M) were fixed, while sulfuric acid and acetone concentrations were changed in the range from 1.25 M to 1.76 M and 0.20 M to 0.28 M, respectively. Sequential oscillations (Figure 1) were observed in the ranges of 1.65 M to 1.75 M sulfuric acid concentration ([acetone] = 0.20 M) and 0.22 M to 0.27 M acetone concentration ([H2SO4] = 1.50 M). Increasing further any of these concentrations make the break between the two groups of oscillations grows until it becomes an induction period. The results show also that changes on oscillations caused by shifts of sulfuric acid or acetone concentrations can be compensated by each other.