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

Abstract

The B-Z oscillatory reaction between potassium bromate and gallic acid (in the presence of sulphuric acid and ferroin indicator) has been calorimetrically and potentiometrically studied in the presence of electrolytes, particularly chloride and nitrate salts of potassium, sodium, barium, strontium and calcium. The reaction has been studied at different concentrations of each electrolyte. The frequency of oscillations and total enthalpy of oscillation have shown

dependence on the concentration of electrolytes. At concentrations below 10^-7 equiv dm^-3, the electrolytes cannot inhibit the oscillatory 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. The oscillatory behaviour of the reaction

probed by the potentiometric method has a general agreement with the calorimetric study. The effects of the electrolytes on the damping coefficients of the oscillatory process with declining amplitudes have been calculated and

compared.