THE MOLAR HEAT-CAPACITIES OF (BENZENE PLUS TETRACHLOROMETHANE), (BENZENE PLUS TRICHLOROMETHANE), (BENZENE PLUS ACETONE) AND (ACETONE PLUS TRICHLOROMETHANE)

Using a high-temperature flow calorimeter, we determined the molar hea t capacities at constant pressure C-p,C-m of four binary mixtures at t hree different temperatures (410.3, 514.7, and 630.6) K and various co mpositions. The binaries investigated are: (benzene + tetrachlorometha ne), (benzene + trichloromethane), (benzene + acetone), and (acetone trichloromethane). At T = 630.6 K, all these mixtures showed ideal ga s behavior, i.e. heat capacity additivity. However, excess heat capaci ties were found at lower temperatures, particularly in (Lewis base + a cidic proton) and (non-polar + polar) binary systems, such as (acetone + trichloromethane), (benzene + acetone), and (benzene + trichloromet hane), but no significant excess heat capacities were detected in (non -polar + non-polar) systems. The excess heat capacity can be attribute d to intermolecular interaction between unlike molecules. The heat cap acities of the binary mixtures considered in the experiment were also calculated using both cubic (van der Waals)-type and virial-type equat ions of state: PR EOS and truncated virial EOS, respectively. The two EOSs gave comparable results. However, there are some statistically si gnificant biases between the calculated results and experimental value s in systems containing a polar component. This may be due to the limi tations of the mixing rules used in the calculation. (C) 1997 Academic Press Limited.