Thermodynamic properties of fluids are generally calculated from the P
VT relations through equations of state. The majority of existing equa
tions of state require the critical properties or intermolecular poten
tial energy parameters as their input data. In many cases, such proper
ties are neither available nor they can be accurately estimated. One a
ccessible and accurately measurable property of substances is the velo
city of sound. In this report a method is introduced through which one
can predict the PVT behavior of fluids using the velocity of sound da
ta. A general mathematical relationship, c2 = c2 hs + - V2/M integral-
infinity/T (partial derivative 2T/partial derivative V2) s (partial de
rivative s/partial derivative T) V dT expressing the velocity of sound
, c, in terms of the hard-core velocity of sound, C(hs), and thermodyn
amic properties is derived. One may use this equation to extract PVT d
ata from cVT data, or vice versa. As an example the virial coefficient
s, the Lennard-Jones intermolecular potential parameters, and the cons
tants of the van der Waals equation of state for a number of pure flui
ds are calculated using the velocity of sound data. Utility of this me
thod is particularly attractive for such compounds as heavy hydrocarbo
ns, unstable fluids, and newly designed molecules for which intermolec
ular parameters and critical properties are not available.