Henry's constants of toluene, ethylbenzene (EtB), 1,2,4-trimethylbenzene (TMB), and hexane in di-2-ethylhexyl phthalate (DEHP), diisoheptyl phthalate (DIHP), and diisononyl phthalate (DINP) were determined experimentally applying a dynamic method, at temperatures ranging from (293.15 to 373.15) K and at 1 atm. The logarithms of Henry's constants were fitted as linear functions of the inverse of absolute temperature (thanks to equations similar to the van't Hoff equation). These equilibrium data were predicted with a mean relative deviation of 11 % by the modified UNIFAC thermodynamic model of solution.