Conditions required for heat-capacity measurements using modulated-temperature calorimetry.

Modulated-temperature calorimetry, in which the same apparatus as a standard differential scanning calorimeter is used, is a powerful method for measuring heat capacities. Precise heat capacity measurements are useful, for example, to analyze anomalous behavior at the glass transition. However, owing to the periodically-modulated temperature we have to pay attention to: (1) the thickness of the sample; (2) the thermal contact resistance between the sample and the sample pan; and (3) the thermal contact resistance between the sample pan and the base plate of the apparatus. This article will illustrate the following. The thickness of a sample should be chosen so as to satisfy uniformly-modulated temperature conditions throughout a sample, and subsequently both thermal contact resistances should be reduced so that the relaxation times caused by the thermal contact resistances are adequately small in comparison with the period of modulated temperature.