Ž . Fluid Phase Equilibria 172 2000 1–26 www.elsevier.nlrlocaterfluid Prediction of the critical locus in binary mixtures using equation of state II. Investigation of van der Waals-type and Carnahan–Starling-type equations of state Ilya Polishuk a, ) , Jaime Wisniak a , Hugo Segura b , Leonid V. Yelash c , Thomas Kraska c,1 a Department of Chemical Engineering, Ben-Gurion UniÕersity of the NegeÕ, Beer-SheÕa, Israel b Department of Chemical Engineering, UniÕersidad de Concepcion, Concepcion, Chile ´ ´ c Institute of Physical Chemistry, UniÕersity at Cologne, Cologne, Germany Received 8 November 1999; accepted 11 April 2000 Abstract The ability to predict critical lines of members of the methane–, perfluoromethane– and water–alkanes Ž . Ž . homologous series is compared for van der Waals vdW -type and Carnahan–Starling CS -type equations of state. A temperature dependent combining rule for the binary attraction parameter is discussed and employed. It is found that the appropriate choice of the adjustable parameters yields quite accurate results for both equations. A new application of global phase diagrams is proposed for the quantitative description of real mixtures. In this diagram, the boundaries of the different types of phase behavior are presented in the k – l plane. Analysis of 12 12 this diagram has allowed us to reach conclusions that cannot be obtained by a simple fit of data points. In particular, it is demonstrated that the global phase diagram’s shape defines the correlative ability of the equations. It is found that CS-type equations tend to predict a larger region of liquid–liquid immiscibility, the accuracy of the result depends on the particular experimental system. Changes in the density dependence of the attraction term of the two-parameter equations influence mostly the predicted critical volumes and not their qualitative performance. In addition, the development of a CS-type equation suitable for engineering calcula- tions is discussed. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Vapor–liquid equilibria; Liquid–liquid equilibria; Global phase diagram; Method of calculation; Equation of state; Critical state ) Corresponding author. Ž . Ž . E-mail addresses: polishyk@bgumail.bgu.ac.il I. Polishuk , kraska@stthd0.pc.uni koelnode T. Kraska . – 1 Also corresponding author. 0378-3812r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0378-3812 00 00366-6