In order to improve the separation of saturated hydrocarbons from unsaturated hydrocarbons in the pentanic C5 fraction, there has been performed liquid ? vapor equilibrium experimental determinations for the isoamilene ? nC5 unsaturated hydrocarbons and iC5 saturated hydrocarbons in the presence of di-propylene-glycol. The experimental results are presented under the form of y ? x system equilibrium diagrams on base without solvent.