  The sound velocity in selected liquid alloys of the isomorphous Bi-Sb system
was measured as a function of temperature to a high accuracy of 0.2%. The sound
velocity temperature coefficient, dlnc/dT, at the liquidus is found to vary
non-monotonously as a function of alloy composition, with the transition from
normal to anomalous temperature dependence occurring at a composition of
approximately Bi35Sb65. Beyond this composition up to approximately Bi10Sb90
the sound velocity is found to be temperature independent over a wide range.
The deviation of the sound velocity from that expected in an ideal solution is
found to be dominated by a sub-regular interaction. The present measurements
allow the determination of the pressure dependence of the sub-regular solution
interaction parameters and are found to be consistent with high pressure
studies of the phase diagram in this system. The sound velocity is shown to be
an effective measure of the pressure dependence of the alloy interactions.
