Abstract: Anew oscillating system. 3,4-dihydroxybenzoic acid-BrO₃--Fe(phen)₃²⁺-H₂SO₄system was studied in detail. The role of bromide ion in the oscillation was investigated. The initial addition of bromide ion to the system produced a variety of phenomena depending on the initial bromide concentration. In certain range concentration of bromide, the system displays two types of oscillating waves, one is a low-frequency oscillating wave and the other is a high-frequency oscillating wave. Both of these oscillations are controlled by bromide ions. When bromide concentration is lower than 2. 3 ×10^-3mol/L, only low-frequency oscillating wave appears, and when bromide concentration is more than 2. 9×10^-3mol/L, only high-frequency oscillating wave appears. The role of bromide in this system was analyzed and the mechanism of bromide in the oscillation was proposed.

Key words: 3,4-Dihydroxybenzoic acid, Belousov-Zhabotinsky(BZ) reaction, Oscillating frequency