TEMPERATURE CALIBRATION ON COOLING USING LIQUID-CRYSTAL PHASE-TRANSITIONS

Temperature calibration in heating and cooling mode is necessary in the case of power compensated differential scanning calorimeters for the accuracy in the temperature to be better thn 0.5 K on cooling. The smectic A to nematic transition of biphenyles fulfils the conditions required for verifying the symmetry of the temperature calibration in heating and cooling modes at at least one temperature. That is to say, there is a negligible supercooling of that transition combined with high thermal stability and reproducibility and a well defined determination of the transition temperature. 4-Cyano-4'-octyl-biphenyl is recommended for verifying the linearity of the temperature correction for heating and cooling rates in the case of power compensated DSC. The procedure for testing and correcting of apparative asymmetries is given.