A rate law model for the explanation of complex pH oscillations in the thioureaiodatesulfite flow system

In a continuous flow stirred tank reactor (CSTR), the reaction of thioureaiodatesulfite (TuIS) exhibits a rich variety of complex oscillations in pH. The transitions from 1 n type oscillations to 1 3 , 1 2 type and simple oscillations were observed on decreasing the flow rate gradually in small steps at 30.2 C and 20.5 C, respectively. The transitions from 1 n type oscillations to 1 0 1 4 , 1 0 1 3 type and simple oscillations were observed as well on increasing the temperature in small steps at a given flow rate. Based on the analogous iodatesulfitethiosulfate system a simple empirical rate law model is suggested to give a sound agreement between the experimental and simulated results on the complex oscillatory behaviour. A possible explanation of the emergence of the simple empirical rate law model from the mechanism of the individual reactions of the TuIS system is also discussed. A simple rate law model is presented that accounts for the experimentally observed complex pH oscillations in the thioureaiodatesulfite system.