SynopsisGel permeation chromatography, using polystyrene gel and tetrahydrofuran as solvent, has been applied to hydroxybenzopheriones, esters of salicylic acid, alkylphenols, alkylated methylenediphenols, and phenol-formaldehyde condensation products. The difference between the calculated molecular volume of these phenolic compounds and that obtained by actual determination with GPC has been ascribed to tetrahydrofuran solvation of the phenolic hydroxyl group. Furthermore, it has become clear that THF solvation is affected by the steric hmdrance of ortho-substituted phenol and by inactivation of the phenolic hydroxyl group resulting from internal hydrogen bonding.