The calorimeter consists of two symmetrical thermal fluxmeters, each constructed by a series of 480 thermocouples surrounding a cylindrical hole for the measurement cells. The electric signal delivered by the difference in output voltage of the two fluxmeters is proportional to the thermal effect occuring in the cells. It is calibrated by using electrical heaters inside the cells. The temperature of the calorimeter (-190 to 200°C) can be regulated by using a cold nitrogen gas flow and electric heating.
The calorimeter can be used for the measurement of enthalpies of mixing and solution, enthalpies of vaporization, enthalpies of fusion and transition, enthalpies of reactions, enthalpies of adsorption and desorption and heat capacities. For each application suitable measurement cells are available.
For fitting interaction parameters of gE - and group contribution models, applicable for a larger temperature range, enthalpy of mixing data directly provide the temperature dependence of the activity coefficients.
Recently a series of measurements for binary systems containing N - methylacetamide or benzoic acid was performed. Whereas the flow calorimeter allows the fast and reliable measurement of hE, for all systems containing benzoic acid, naphthalene or phenol, the Tian - Calvet calorimeter was used, because neither the flow pumps nor the back pressure regulator of the flow calorimeter can be applied at elevated temperatures to keep the substances in the liquid state. The data are used to derive appropriate parameters of gE- models and the mod. UNIFAC (Do) group contribution model. With the help of these data and the DDB - database a revision of parameters for the acetamide group and the introduction of a new aromatic acid group is in progress.