plus remain reasonably constant when the concentration of the heptanes-plus fraction is decreased by a factor of approximately 2. The effect of a decrease in the heptanesplus fraction at the concentrations studied serves mainly to extend the pressure region over which these ratios are defined. This trend could be completely reversed with a continued decrease in the heptanes-plus concentration. Decreasing the amount of the heptanes-plus fraction in this system does have a slight effect on the equilibrium ratios of the intermediate components, ethane through hexanes; the net effect is a small increase at the higher pressures.

Using a value of zc of 0.269 (72), reduced second virial coefficients were calculated from Equation 11and compared with values read from the curve of Figure 5. The comparison is made in Table VIII. Above TR = 0.7, the agreement is within the experimental accuracy of the virial coefficients.