Micro heat-flow calorimeter for investigating the 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.