THE SCALED PARTICLE THEORY AND THE TAIT EQUATION OF STATE

The pressure coefficient of the Tait equation of state for water has been compared to the network stress or pressure derived from the application of the scaled particle theory (SPT). The two pressures are equivalent when the mean molecular distance of closest approach, a, is around 2.8 angstrom, dropping to 2.7 angstrom as the boiling point is approached. The effect of applied pressure, to 1000 bar, was considered also and a found to be a linear function of density. The values of a are consistent with an equation derived by P. W. Bridgman, giving the thermal conductivity as a function of the sound velocity and a. Using equations derived from the scaled particle and fluctuation theories, the second parameter of the Tait equation was interpreted as the cell volume/sites ratio of a quasilattice. The equations are applicable to any liquid, and preliminary results for ethanol show equivalence of the Tait and SPT pressures for this liquid.