Practical and theoretical consideration of flow-through microcalorimetry: determination of “thermal volume” and its flow rate dependence

The results have recently been reported of a preliminary study into the base catalysed hydrolysis of methyl paraben as a test and reference reaction for flow-through microcalorimeters. The values quoted for the rate constant and the molar enthalpy change are (3.15±0.11)×10−4 s−1 and −50.5±4.3 kJ mol−1, respectively. The present paper explains the results of further studies of the methyl paraben reaction and also describes some practical and theoretical considerations of flow microcalorimetric experiments. It is shown that experimental design (sample and reference arrangements) has a significant impact upon the derived data. Particular attention is paid to the theoretical range of values for the molar enthalpy change and the rate constant, for reactions that could be studied successfully by flow calorimetry.