Thermodynamic Data from DSC Experiments

The versatility of the DSC method and the high speed of the experiments have costs in terms of accuracy. For example, the best accuracy in the determination of heat capacities of solids by DSC is typically 1% [3,248-250], at least one order of magnitude worse than the accuracy of the corresponding measurements by adiabatic calorimetry [251]. This accuracy loss may, however, be acceptable for many purposes, because DSC experiments are much faster and require much smaller samples than adiabatic calorimetry experiments. In addition, they can be performed at temperatures significantly above ambient, which are outside the normal operating range of most adiabatic calorimeters. 

Let us first address the question of the accurate measurement of the temperature of the sample in DSC experiments [252-255], As illustrated in figure 12.4, the programmed temperature, Tp, usually varies linearly with the time t, and can 

The most widely recommended calibration method for dynamic DSC operation involves the determination of the extrapolated onset temperature for the fusion of several standard substances, using various heating rates [255,256], 

As mentioned, the calorimetric applications of DSC involve the conversion of a peak area into the energy associated with a chemical reaction or with a physical process (e.g., fusion, vaporization). Because the trace of the peak does not by itself define an area, an appropriate baseline must be found. The complexities of the baseline construction and their influence on the measurement of heat by 

To our knowledge, the question of the standard state corrections in DSC experiments has never been addressed. These corrections may in general be negligible, because most studies only involve condensed phases and are performed at pressures not too far from atmospheric. This may not be the case if, for example, a decomposition reaction of a solid compound that generates a gas is studied in a hermetically closed crucible, or high pressures are applied to the sample and reference cells. The strategies for the calculation of standard state corrections in calorimetric experiments have been illustrated in chapter 7 for combustion calorimetry. 

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