Oscillatory reaction of bromate-gallic acid: A calorimetric and potentiometric study on inhibitory effects of salts

The B-Z oscillatory reaction between potassium bromate and gallic acid tin the presence of sulphuric acid and ferroin indicator) has been calorimetric ally and potentiometrically studied in the presence of electrolytes, partic ularly chloride and nitrate salts of potassium, sodium, barium, strontium a nd calcium. The reaction has been studied at different concentrations of ea ch electrolyte. The frequency of oscillations and total enthalpy of oscilla tion have shown dependence on the concentration of electrolytes. At concent rations below 10(-7) equiv dm(-3), the electrolytes cannot inhibit the osci llatory reaction. At higher concentrations, both the frequency and enthalpy of oscillation decrease; the process is totally suppressed at electrolyte concentration > 10(-4) equiv dm(-3). Among the electrolytes studied, sodium salts (both chloride and nitrate) have shown maximum inhibitory effect. Th e oscillatory behaviour of the reaction probed by the potentiometric method has a general agreement with the calorimetric study. The effects of the el ectrolytes on the damping coefficients of the oscillatory process with decl ining amplitudes have been calculated and compared.