Using thermoanalytical data Part 4. Processing of DTA/DSC curves to calculate reaction enthalpy and kinetic parameters. An application to calcium oxalate

With regard to single step reactions, a new approach to the processing of DTA/DSC curves is presented, taking into account the heat transfer into the instrument. It is an extension of a previous physical model, that allowed the calculation of true kinetic parameters from TG curves. The peak area can be properly calculated as well as the degree of reaction, this also being suitable for kinetic parameters calculation. Through numerical simulations, other methods for DTA/DSC curve processing are discussed with respect to that proposed. By TG and DTA, the true kinetic parameters have been finally determined for the second and third steps of the thermal decomposition of CaC2O4.H2O, to complete previously reported data for the first dehydration step. The agreement of the results with isothermal experiments seems to indicate a way to escape from the dichotomy between isothermal and non-isothermal kinetics. Several other approaches to non isothermal kinetics are reviewed and discussed. The software developed is also briefly described.