A procedure for the calculation of enthalpy changes from continuoustitration calorimetric experiments

Abstract

An isoperibolic titration calorimeter has been modified to perform continuous-titration measurements. In order to take into account the unavoidable time-lag in the response of the sensor element to temperature changes, the process of heat transfer inside the calorimeter has been schematized. A calculation procedure, based on this model, allows the interpretation of the experimental data and the determination of enthalpies of reaction. The method has been tested by measurement of the heat of ionization of water and the heat of protonation of aminotris (hydroxymethyl) methane at 298 K. The results are in good agreement with previously reported data. The stepwise enthalpies of protonation of the phosphate ion in 0.15 mol dm^–3 NaCl at 298 K have also been determined.