A GENERAL EQUATION OF STATE FOR DENSE FLUIDS

A general equation of state, originally proposed for compressed solids by Parsafar and Mason, has been successfully applied to dense fluids. The equation was tested with experimental data for 13 fluids, includi ng polar, nonpolar, saturated and unsaturated hydrocarbons, strongly h ydrogen bonded, and quantum fluids. This equation works well for densi ties larger than the Boyle density rho(B) [1/rho(B) = T(B)dB(2)(T-B)/d T, where B-2(T-B) is the second virial coefficient at the Boyle temper ature, at which B-2 = 0] and for a wide temperature range, specificall y from the triple point to the highest temperature for which the exper imental measurements have been reported. The equation is used to predi ct some important known regularities for dense fluids, like the common bulk modulus and the common compression points, and the Tait-Murnagha n equation. Regarding the common points, the equation of state predict s that such common points are only a low-temperature characteristic of dense fluids, as verified experimentally. It is also found that the t emperature dependence of the parameters of the equation of state diffe rs from those given for the compressed solids. Specifically they are g iven by A(i)(T) = a(i) + b(i)T + c(i)T(2) - d(i)T ln(T).