Prediction of Liquid Molar Volumes by Additive Methods

Liquid molar volumes of typical alcohols and hydrocarbons measured previously under atmospheric pressure at 20–70°C are complied and tabulated. An additive method by Elbro et al. was adopted to predict these liquid molar volumes. The method is found to be useful. However, it cannot be adopted to several substances because additive factors required are not available. In this study, a simple predictive method is proposed by using the expansion coefficient, β = (vb – v25)/(tb – t25). The molar volumes at 25°C, v25, and at the normal boiling point, vb, were predicted by the additive methods of Fedors and Le Bas, respectively. Liquid molar volumes at the temperature t can be predicted by v25 + β(t – 25). The present approach is found to be successful except for small molecules, such as methanol and ethanol.