Volumetric behavior of the binary systems benzene–cyclohexane and benzene–2,2,4-trimethyl-pentane at temperatures 293.15–323.15 K

Densities of the binary system benzene–cyclohexane at several temperatures (293.15–323.15 K) and at atmospheric pressure were measured using a vibrating-tube densimeter in a static mode. Excess molar volumes were calculated from the densities and correlated using the second-order Redlich–Kister equation. Present data were compared with those determined previously by pycnometric measurements; a fair agreement of the old and new data sets was found. Also comparison with previously presented experimental data of other authors was proved with a good agreement. In order to test ability of the cubic equations and the standard mixing and combining rules to correlate/predict the concentration dependence of the excess volume, Peng–Robinson equation of state was successfully applied to the present data. Close similarity of characteristic parameters of benzene and cyclohexane prevents to discern among mixing rules available in literature and those proposed within this paper. Thus, another binary system, i.e. benzene–2,2,4-trimethylpentane was investigated in the temperature range 293.15–323.15 K. Peng–Robinson constants of the components of this system differ in their magnitude and thus allow to study the effect of different combining rules. It was found that the considered two combining rules with slightly different correction constants k12 yielded very similar V m E dependencies on the concentration.