Pressure of the fluid was measured with an expanded uncertainty of 0.25 kPa by means of a pressure transducer (Paroscientific model KR415-101) located within the pressure generation sub-system. A manual syringe pump with a displacement of 30 cm3 was used to raise and adjust the pressure. The apparatus was calibrated using speed of sound for n-octane at atmospheric pressure and various temperatures. The calibration procedure was through determination of ΔL ¼ L1–L2, where L1 and L2 are two different path lengths between transducer and the two reflectors. The value of ΔL as determined from measured data was 20.037 mm compared to the actual value of 20 mm. However, in each new round of experiments the instrument was recalibrated using n-octaneat T ¼ 298.15 K and P ¼ 0.1 MPa and the speed of sound under these conditions was taken as 1172.0 ms1 as reported by Peletiesetal.(2010). Uncertainty for
the measurements was about 1 ms1.