The Partial Molal Volumes of Normal Chain Alcohols in Water–Ethanol Mixtures at 25 °C

The partial molal volumes (\barV0) of n-alcohols (RmOH, m=1–7) at an infinitely dilute concentration in water–ethanol mixtures of various compositions have been determined by means of dilatometry. The \barV0 value does not depend on the concentration of the solute alcohol within the region studied in any composition of the solvent mixtures. The excess volume, the difference between \barV0 and the molal volume (V0), is negative and is at a minimum in water-rich mixtures (<16 wt% ethanol) for all of the alcohols studied. On the other hand, in the moderate composition range the excess volumes for R4OH and higher alcohols are positive and reach a maximum distinct from the disappearance of the maximum for R3OH and lower alcohols. The volumetric contribution of a methylene group (\barVme) to \barV0 was separately evaluated. From the results, a linear relation was found between \barV0 and the alkyl chain length of the alcohols in the mixtures of 0–8 and 55–100 wt% ethanol, while in the mixtures the relationship ...