Two types of flow calorimetric units for enthalpy of mixing measurement have been constructed. One is of the twin isoperibol type, using two silicon PTC sensors for temperature sensing. The other is of the twin conduction type, similar in fundamental structure to that of Wadsö
et al. The heat sink in the conduction type unit was arranged so as to be in thermal contact with a thermostated water bath, resulting improvement of thermal stability. The final heat exchanger was also placed on the heat sink near the flow cells, to eliminate the “flow effect”effectively. The performance of these calorimeter units has been tested and problems are discussed. Excess enthalpy of benzene+cyclohexane system and enthalpy of dilution of aqueous urea solution were measured at 298.15K, using these calorimetric units. The conduction type unit is better than the isoperibol type unit in precision and in the ease of procedure.
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