Ultrasonic speed in (benzonitrile + nitrobenzene) under high pressures

Abstract Ultrasonic speeds u in {(1− x )C 6 H 5 CN + x C 6 H 5 NO 2 } were measured at temperatures of 298.15 and 303.15 K and pressures up to 100 MPa by a sing-around technique operated at a frequency of 2 MHz with an estimated error of less than ±1.8 m·s −1 . The curve of u ( x ) showed peculiar behaviour: there are clear deviations from the smoothing curve in the vicinity of x = 0.25 and x = 0.57, and a new curve corresponding to the region between these two compositions has a different composition dependence from those for lower and higher x regions. Even if the temperature and pressure are raised, the x ranges of the new curve are unchanged, but the irregularities in u ( x ) become more pronounced.