The second-interaction cross virial coefficients B/sub 1M/ are calculated for the solutes n-hexane, trans-3-hexene, benzene, 3,3-dimethylpentane, and cyclohexane with hydrogen, helium, nitrogen, carbon monoxide, carbon dioxide, argon, water, methane, ethane, carbon tetrachloride, and fluorotrichloromethane. The results are then used to evaluate the regression of In (solute specific retention volume) (V/sub g/..pi..) with carrier pressure and composition, and it is shown theoretically as well as demonstrated experimentally that retentions as well as retention order can accordingly be altered. Plots of solute V/sub g//sup 0/ or of (V/sub g/..pi..)/sup -1/ against mole fraction of the fluoroalkane mobile phase in admixture with hydrogen are found to be curved, although the curvature is slight at column pressure drops of 1.1 atm and less. The linear variation of solute capacity factors K' against partial pressure of steam + nitrogen as reported by Pretorius is thereby explained.