AN ISOTHERMAL SCANNING CALORIMETER CONTROLLED BY LINEAR PRESSURE VARIATIONS FROM 0.1-MPA TO 400-MPA - CALIBRATION AND COMPARISON WITH THE PIEZOTHERMAL TECHNIQUE

An isothermal scanning calorimeter controlled by linear pressure variations is described for the pressure range 0.1-400 MPa at temperatures from 303 to 573 K. The rate of pressure variations can be as low as 0.002 MPa/s over the whole pressure range. The functioning of the instrument was tested by measuring the coefficient of thermal expansivity of liquid n-hexane, with calibration performed with gaseous nitrogen and by measuring the coefficient of thermal expansivity of benzene with calibration performed with liquid n-hexane. The results are compared with literature results obtained by the piezothermal technique and with results obtained in the present instrument by the use of a pressure stepwise scanning mode. An example of an investigation of an isothermal solid-to-liquid transition in benzene is also given.