Measurements of the liquid-liquid coexistence curves of {(1 − x) dimethyl carbonate + x pentadecane} and {(1 − x) dimethyl carbonate + x heptadecane} in the critical region

Abstract

The liquid-liquid coexistence curves in a temperature range of about 10 K from the upper consolute critical temperature for binary solutions of {dimethyl carbonate + pentadecane} and {dimethyl carbonate + heptadecane} have been precisely measured. The upper consolute mole fraction xc of n-alkane and the upper consolute temperature Tc were determined to be xc = 0.210, Tc = 312.234 K for {dimethyl carbonate + pentadecane} and xc = 0.183, Tc = 320.496 K for {dimethyl carbonate + heptadecane}, respectively. From the data collected in the near critical point, the critical exponent β was deduced and shown to be consistent well with its theoretical value for the 3-D Ising universality class. The dependences of critical properties on the chain length of n-alkane for a series of {dimethyl carbonate + n-alkane} binary solutions were investigated. Furthermore, it was found that the asymmetric behaviors of the coexistence curve could be well described by the complete scaling theory. The contribution of the heat capacity related term to the asymmetric behaviors of the coexistence curves was discussed.