The batch pressure-response cell provides flexible and accurate means of assessing the kinetics in heterogeneous gas-liquid reactions. A new model is derived to determine the kinetics of reactions of general (n,m) order using binary gas phase. This model has an important feature that allows the determination of the reaction order with respect to the gas-phase reactant and the rate constant from a single set of pressure vs. time data through a simple two-parameter estimation routine. Gas mixing was introduced via a simple modification of the liquid-phase magnetic stirrer to reduce the gas-phase mass-transfer resistance to negligible levels and the parameter estimation problem to only two factors. The heterogeneous cobalt catalyzed sulfite oxidation reaction at low partial pressures of oxygen using a nitrogen-oxygen mixture was tested to verify, the validity of the model. The predicted kinetics were remarkably close to those values in the literature, yielding apr oxygen order of 1.98 +/- 0.02, which is taken to be second order in oxygen.