Densities, excess molar volumes and partial molar volumes of the binary mixtures of acetic acid + alkanol (C 1 –C 4 ) at 298.15 K Hossein A. Zarei Department of Chemistry, Faculty of Science, Bu-Ali Sina University, Hamadan, Iran Received 13 January 2006; accepted 15 April 2006 Available online 7 July 2006 Abstract Densities (ρ) of the binary mixtures of acetic acid with methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol and butan-2-ol have been measured at temperature 298.15 K and ambient pressure (815 hPa) as a function of composition using an Anton Paar model DMA 4500 oscillating densimeter. The excess molar volume (V m E ), partial molar volume ( V i ) and excess partial molar volumes ( V i E ) of the binary mixtures were calculated from the density data. The excess molar volumes were correlated with the Redlich−Kister equation. The excess molar volumes are negative for methanol, ethanol, propan-1-ol, propan-2-ol and butan-1-ol. They are positive for butan-2-ol and an inversion of sign in V m E is observed for butan-2-ol around 0.9 mol fraction of acetic acid. The results obtained in this work were interpreted in terms of intermolecular interaction between like and unlike molecules, difference in size and shape of unlike molecules and the steric hindrance caused by increased methylation. © 2006 Elsevier B.V. All rights reserved. Keywords: Densities; Excess molar volume; Acetic acid; Alkanol 1. Introduction The excess properties of binary liquid mixtures are important to understand and interpret the nature of interaction between the molecules of the mixtures [1–4]. These properties result from experimental measurements or correlations. Developing accu- rate correlation requires accurate experimental measurements to ensure that the equation represents the correct physical behavior of the measured property. This paper reports on the densities (ρ), excess molar volume (V m E ), partial molar volume ( V i ) and excess partial molar volumes ( V i E ) of the binary mixtures of acetic acid with methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol and butan-2-ol at ambient pressure (815 hPa) and temperature (298.15 K). By extrapolation of the excess partial molar volumes to infinite dilution, limiting excess partial molar volumes ( V i E,0 ) are also obtained. These values are interesting from a theoretical point of view since at infinite dilution the only interactions present are solute–solvent interactions. Some of our results of excess molar volume were compared with literature values [5–7]. 2. Experimental 2.1. Materials The pure components were high purity grade reagents from Merck. The purity grades of pure components specified by the manufacturer are given in Table 1. The purity of components was checked by comparing their measured Journal of Molecular Liquids 130 (2007) 74 – 78 www.elsevier.com/locate/molliq Table 1 Densities (ρ), refractive indices (n D 25 ) and stated purity of the pure components at temperature 298.15 K and ambient pressure (815 hPa) and comparison with literature Component Purity (mass fraction) ρ/(g cm − 3 ) n D 25 Experimental Literature Experimental Literature Acetic acid 0.998 1.04376 1.04365 [7] 1.3703 1.3698 [8] Methanol 0.995 0.78654 0.78664 [8] 1.3270 1.32652 [8] Ethanol 0.998 0.78515 0.78504 [8] 1.3595 1.35941 [8] Propan-1-ol 0.998 0.79953 0.79954 [12] 1.3833 1.38370 [8] Propan-2-ol 0.995 0.78090 0.78085 [9] 1.3751 1.3752 [8] Butan-1-ol 0.998 0.80579 0.80576 [10] 1.3974 1.3973 [8] Butan-2-ol 0.99 0.80248 0.80239 [11] 1.3955 1.3950 [8] E-mail address: zareih@basu.ac.ir . 0167-7322/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molliq.2006.04.009