Critical review of small sample calorimetry: improvement by auto-adaptive thermal shield control

The paper reviews measuring and data computation procedures in heat-step calorimetry, for small samples (<100 mg mass) and at low temperatures (T < 100 K) under semi-adiabatic (isoperibol) measuring condition. In conjunction with an auto-adaptive heat-shield control, a method is described how the heat losses, occurring during an isoperibol measuring cycle, are correctly taken into account in order to achieve an absolute uncertainty of C-p of 1% or lower. The basic features of the method are strictly adiabatic condition at the beginning of each heat capacity measuring point, achieved by an extremely small temperature drift of the sample, and a very constant temperature of the heat-shield during the whole measuring cycle. (C) 2002 Elsevier Science B.V. All rights reserved.