Using a high-temperature flow calorimeter, we determined the molar heat capacities at constant pressure C-p,C-m of four binary mixtures at three different temperatures (410.3, 514.7, and 630.6) K and various compositions. The binaries investigated are : (benzene + tetrachloromethane), (benzene + trichloromethane), (benzene + acetone), and (acetone + trichloromethane). At T = 630.6 K, all these mixtures showed ideal gas behavior, i.e. heat capacity additivity. However, excess heat capacities were found at lower temperatures, particularly in (Lewis base + acidic proton) and (non-polar + polar) binary systems, such as (acetone + trichloromethane), (benzene + acetone), and (benzene + trichloromethane), but no significant excess heat capacities were detected in (non-polar + non-polar) systems. The excess heat capacity can be attributed to intermolecular interaction between unlike molecules. The heat capacities of the binary mixtures considered in the experiment were also calculated using both cubic (van der Waals)-type and virial-type equations of state : PR EOS and truncated virial EOS, respectively. The two EOSs gave comparable results. However, there are some statistically significant biases between the calculated results and experimental values in systems containing a polar component. This may be due to the limitations of the mixing rules used in the calculation.