An isothermal scanning calorimeter controlled by linear pressure variations from 0.1 to 400 MPa. Calibration and comparison with the piezothermal technique

Abstract

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.