Densities, Viscosities, and Refractive Indices of Binary Mixtures of Methyl Ethyl Ketone + Pentanol Isomers at Different Temperatures Mohammad Almasi and Hossein Iloukhani* Department of Physical Chemistry, Faculty of Chemistry, University of Bu-Ali Sina, Hamedan 65174, I. R. Iran Densities, viscosities, and refractive indices of mixing of methyl ethyl ketone with 1-pentanol, 2-pentanol, and 3-pentanol have been measured as a function of composition range at temperatures (298.15, 308.15, and 318.15) K and ambient pressure. Excess molar volumes V m E , viscosity deviations Δη, and refractive index deviations Δn D were calculated and correlated by the Redlich-Kister-type function to derive the coefficients and estimate the standard error. From the experimental data, partial molar volumes, V j m,i , and partial molar volumes at infinite dilution, V j m,i 0 , were also calculated. The latter values are interesting from a theoretical point of view since at infinite dilution the only interactions present are solute-solvent interactions. The effect of temperature and -OH group position of pentanol isomers on the excess molar volumes, viscosity, and refractive index deviations of its mixtures with methyl ethyl ketone is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. Introduction It is well-known that the thermodynamic properties of liquid mixtures depend on the way in which molecules of pure solvents are associated during the mixing process. From this point of view, a study of the thermomechanical behavior of solvent mixtures should provide an important source of structural information at the microscopic level. Properties such as density, viscosity, and refractive index deviation of pure chemicals and of their binary liquid mixtures over the whole composition range measured at several temper- atures are useful for a full understanding of their thermodynamic and transport properties as well as for practical chemical engineering purposes. On the other hand, excess thermodynamic functions and deviations of nonthermodynamic ones of binary liquid mixtures are fundamental for understanding of the interactions between molecules in these types of mixtures, particularly when polar components are involved. These func- tions have also been used as a qualitative and quantitative guide to predict the extent of complex formation in this kind of mixtures. 1–3 Excess and deviation properties of binary mixtures are complex properties because they depend not only on solute- solute, solvent-solvent, and solute-solvent interactions but also on the structural effects arising from interstitial accommodation. Knowledge of several properties at different temperatures is required for engineering design and for subsequent operations. 4 The main purpose of the preceding papers of this series 5,6 was to provide a set of thermodynamic data for the analysis and characterization of molecular interactions in binary liquid mixtures containing alkanols with nitrils and ketones. In continuation with these investigations, the present paper reports the excess molar volumes, viscosity, and refractive index deviations for methyl ethyl ketone + 1-pentanol, methyl ethyl ketone + 2-pentanol, and methyl ethyl ketone + 3-pentanol at temperatures (298.15, 308.15, and 318.15) K, with the aim of analyzing the influence of temperature and -OH group of pentanol isomers upon the aforementioned excess properties. Experimental Section Chemicals. Methyl ethyl ketone, 1-pentanol, 2-pentanol, and 3-pentanol were purchased from Merck with mass fraction higher than 99 % and used without further purifications. The purity of reagents was checked by comparing the measured densities, viscosities, and refractive indices at 298.15 K with those reported in the literature. 5,7–13 The results are in good agreement with values found in the literature and reported in Table 1. Apparatus and Procedure. The density of the pure com- pounds and mixtures was measured by an Anton Parr DMA 4500, provided with automatic viscosity correction. The uncer- tainty of the density measurements was estimated to be ( 1 · 10 -5 g · cm -3 . The apparatus was calibrated once a day with dry air and bidistillated water. The temperature in the cell was regulated to ( 0.01 K with a solid state thermostat. Viscosities were measured with an Ubbleohde viscometer with an uncer- tainty of ( 2 · 10 -3 mPa · s. The equation for viscosity, according to Poiseuille’s law, is η )F(kt - c/ t) (1) were k and c are the viscometer constants and t and are the efflux time and dynamic viscosity, respectively. The k and c * To whom correspondence should be addressed. E-mail: iloukhani@basu.ac.ir. Tel./fax: +98 0811 8271061. Table 1. Experimental and Literature Values of Densities G, Viscosities η, and Refractive Indices n D of Methyl Ethyl Ketone, 1-Pentanol, 2-Pentanol, and 3-Pentanol, at T ) 298.15 K F η g · cm -3 mPa · s n D compd exptl lit. exptl lit. exptl lit. methyl ethyl ketone 0.79976 0.7999 a 0.391 0.3855 b 1.3750 1.3769 c 1-pentanol 0.81085 0.81083 d 3.540 3.5344 c 1.4068 1.4078 d 2-pentanol 0.80530 0.80540 d 3.478 3.478 e 1.4032 1.4044 f 3-pentanol 0.81579 0.81552 g 4.625 4.598 h 1.4071 1.4079 d a From ref 7. b From ref 8. c From ref 9. d From ref 11. e From ref 5. f From ref 10. g From ref 12. h From ref 13. J. Chem. Eng. Data 2010, 55, 3918–3922 3918 10.1021/je901067c  2010 American Chemical Society Published on Web 06/02/2010