MICRO HEAT-FLOW CALORIMETER FOR INVESTIGATING MELTING AND PHASE TRANSITION BEHAVIOUR OF TRIGLYCERIDE CRYSTALS

A micro heat-flow calorimeter has been developed to investigate the melting and phase transition behaviour of triglyceride mixed crystals. Samples of about 1 mg can be investigated even if heating rates as low as 0·04- 0·15 deg C min-1 are used. Calibration experiments with palmitic acid show an accuracy to 1·4% in the determination of the heat of fusion. Provided that the maximum temperature difference is below 0·1 degC, the accuracy with which the 'clearpoint', i.e. the temperature at which the melting process is finished and the sample becomes optically clear, can be determined is 0·3°C. Possible effects of amount of sample, heating rate and differences in heat flow on the heat effects and clear points are also described.