A RELATIONSHIP BETWEEN EXCESS VOLUMES AND ENTHALPIES

A relationship between excess volumes and enthalpies is presented which could be useful in the application of excess volume data to thermodynamic solution modelling. The treatment was derived for systems which have solid phases which are nearly pure in one component; it predicts that composition derivatives of partial molar excess volumes and enthalpies are proportional to each other by the ratio of the heat of fusion to the volume change on fusion of the non-dilute species. The method has been used to estimate excess enthalpies from excess volume data for a wide variety of systems at 25°C. It gives qualitatively correct results when literature values of Δh0f/Δυ0f are used, and more accurate results with effective Clapeyron ratios (Δh/Δυ)EFF. The relationship can also explain sign differences between excess volumes and enthalpies as well as asymmetric and S-shaped curves. © 1990.