Thermal oscillations in the bromate – oxalic acid – MnSO4 – H2SO4 – acetone system: A calorimetric study

The oscillatory reaction of potassium bromate, oxalic acid, and MnSO4 in the presence of acetone in aq H2SO4 solutions has been studied calorimetrically at different concentrations of substrates. Acetone and oxalic acid have been found to accelerate the reaction by increasing the oscillation frequency. On the other hand, MnSO4 has a retarding effect; the frequency of oscillation decreases systematically with increasing concentration of MnSO4. Potassium bromate shows mixed behavior in this respect. The total heat evolved during the reaction per mol of oxalic acid consumed has been evaluated, which can be used to calculate the concentrations of the various reactants at different stages of the reaction. The effects of different electrolytes (KCl, NaCl, BaCl2, CaCl2, SrCl2, NaBr, NaI, KNO3, NaNO3, and Ca(NO3)2) and solvents (dimethylformamide, 1,4-dioxane, acetonitrile, and tetrahydrofuran) on the extents of oscillation and the enthalpy change for the process have been also examined.Key words: Belousov–Zhabotinsky reaction, oscillatory reaction, oxalic acid, calorimetry, acetone.