Abstract: The thermal pressure coefficients and internal pressures of ethanol＋nhexane liquid mixtures have been measured at different temperatures and compositions.These experimental data are corrected with modified van der Waals model proposed in our previous work.From the parameter of this model B/A2 ,a formula describing the relationship between the dissociation degree of selfassociation and the composition of ethanol in the mixture is obtained.Based on this formula,a model is designed for the mixing of alcohols and hydrocarbons and the equation which can be satisfactorily used to describe the variation of excess enthalpies with the composition are established.It can clearly display the contributions of the physical and chemical action to the excess enthalpies.

Key words: Mixtures of ethanol and nhexane, Internal pressure, Modified van der Waals′ model, Dissociation of selfassociation, Excess enthalpy