EXCESS MOLAR VOLUMES OF CARBOXYLIC ACID MIXTURES: BINARY MIXTURES OF FORMIC, ACETIC, PROPIONIC, n-PENTANOIC AND ISO-PENTANOIC ACIDS AT 298. 15 K.

Systematic measurements of density were performed in six binary mixtures of carboxylic acids. Derived from the densities the excess molar volumes V**E are always positive, with the exception of the formic acid plus acetic acid system where V**E is negative for x less than 0. 75 and positive for mixtures rich in formic acid. The extremal values of V**E are about minus 0. 06 and plus 0. 02 cm**2 mol** minus **1. As a rule, the excess molar volume curves are slightly asymmetrical with respect to composition having the maximal values of about 0. 15 cm**3 mol** minus **1 in the formic acid plus propionic acid system; 0. 10 cm**3 mol** minus **1 in the acetic acid plus propionic acid system; 0. 35 cm**3 mol** minus **1 in the acetic acid plus n-pentanoic acid system; 0. 65 and 0. 62 cm**3 mol** minus **1 in the systems of n-pentanoic and iso-pentanoic acids with formic acid. A qualitative interpretation of the presented results is given taking into account almost complete dimerization of carboxylic acids and the formation of mixed dimers of these acids.