Electrical calibration and testing of calorimeters with simulated, time-variable reaction power

For calorimetric investigations where the reconstruction of the real heat-flow rate during the experiment is required, the usual electrical calibration with constant power is often not sufficient. However, the use of a chemical calibration is limited by the number of suitable and certified reactions showing a known dynamics of the heat-flow rate. Therefore, a computer controlled electrical calibration unit was developed capable of duplicating any simulated reaction power-time curve in the calorimetric cell. The calibration unit consists of a universal simulation software with an interface to a programmable precision current supply connected to the calibration heater inside the calorimetric vessel. The reliability of the electrical calibration was proved with a continuous titration calorimeter using different recommended test reactions (TRIS+HCl, dilution of aqueous KCl, NaCl and urea solutions).

In order to test the electrical calibration procedure in the dynamic mode the heat-flow rate of a first-order equilibrium reaction during a continuous titration experiment was simulated. It is demonstrated that the combination of simulation software and electrical calibration hardware provides a very close adaptation of calibration and experiment, allows a more reliable estimation of experimental uncertainties, simplifies the verification of complex data analysis procedures and opens up new possibilities for the optimization of experimental parameters.