A simple method of estimating liquid densities at moderately high temperature and pressure was obtained from the existing theories for liquids. For pure liquids the smoothed potential cell model was used in conjunction with the empirical equation for saturated liquid densities and the method was extended to the binary mixtures by the use of the average potential model.
The results of sample calculation show that the deviation of estimated values from experiments is about 1 % up to 700 psia and about 5 % at 4,500 psia for pure liquids. It is about 4 % for binary mixture of C₃H₈+C₆H₆. These are comparable with the deviations of other methods.
The main advantage of the present method is that it requires only two constants which can be obtained from two saturated liquid densities which are easy to obtain experimentally. No knowledge on the densities of high pressure is required beforehand as is the case with other methods based on the principle of corresponding states. It is not a correlation method of data, but a prediction method of unknown data.