This paper reports an isothermal microcalorimetric study of the imidazole catalysed hydrolysis of triacetin as an example of a solution phase medium term reaction. The results of this study are then discussed in context of its potential as a quantitative chemical calibrant for calorimeters, especially isothermal microcalorimeters. It will be also shown that chemical calibrants can be important for the determination of the stability of the calorimetric signal itself and hence to the consideration of location and set-up of the calorimeter The imidazole catalysed triacetin hydrolysis reaction was studied in the calorimeter over a period of up to 50 days at 298.15 K and at pH 7.09. We have determined that, under these conditions, this reaction is second order with a rate constant of 8.64 x 10(-4) +/- 1.5 x 10(-5) dm(3) mol(-1) s(-1) and an associated change in enthalpy of -95.2 +/- 1.6 kJ mol(-1). The data analysis for this reaction was performed using a new mathematical approach for the calculation of kinetic and thermodynamic parameters from calorimetric data.