Liquid Saturation Density from Simple Equations of State

Several simple equations of state, requiring only two input properties, have been studied in order to determine the liquid saturation density of 144 fluids of different kinds. This study includes old and new simple modifications of the van der Waals equation of state, and the Carnahan–Starling–Yelash–Kraska and Carnahan–Starling–Dieterici equations. The new simple modifications of the van der Waals equation give better overall results than some other more complex proposed equations, especially near the critical point. The recent equation proposed by Eslami including the boiling temperature and density as input parameters was also checked, and was found not to reproduce the critical point, but to give excellent results at intermediate or low temperatures. As a reference, the behavior of the well-known Soave– Redlich–Kwong and Peng–Robinson equations, and the more recent expression proposed by Mohsen-Nia et al. that requires three input parameters were also checked. The latter does not improve the accuracy of the Peng–Robinson equation, and very simple van-der-Waals type equations give better overall results.