Surface tension of non-ideal binary and ternary liquid mixtures at various temperatures and p = 81.5 kPa A.A. Rafati a,⇑ , A. Bagheri a , M. Najafi b a Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran b Department of Material Engineering, Hamedan University of Technology, Hamedan, Iran article info Article history: Received 2 August 2010 Received in revised form 4 September 2010 Accepted 8 September 2010 Available online 17 September 2010 Keywords: Surface tension Correlation Prediction 1,2-Ethandiol Water Acetonitrile abstract Experimental surface tensions for binary mixtures (1,2-ethandiol + water), (1,2-ethandiol + acetonitrile), and (acetonitrile + water) at temperatures of 283.15 K, 298.15 K, and 308.15 K and the ternary mixture (1,2-ethandiol/water/acetonitrile) at 298.15 K have been measured with the Du Noüy ring tensiometer. The surface tension of the above mentioned binary and ternary systems were correlated with empirical and thermodynamic based models. The methods of Pando et al. and Ku et al. were used to correlate the ternary surface tension data. The Fu et al., Kalies et al. and Wang et al. models were also applied to predict surface tension in the ternary system. The mean average absolute deviations obtained from the compar- ison of experimental and calculated surface tension values for ternary system with three models are less than 2.4%, which leads to concluding that these models show a good accuracy in different situations in comparison with other predictive equations. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Surface tension can be considered to be the result of several phenomena that take place not only on the surface but also within the bulk region of the liquid. An understanding of the structure and specific molecular interactions of the pure compounds and their mixtures can be obtained from surface tension data. Besides, in chemical engineering, surface tension not only determines the quality of many industrial products, but also affects some impor- tant steps in production process of catalysis or adsorption [1–3]. The surface tension of liquids is determined by cohesion forces among their molecules, as a result of which the theoretical descrip- tion of surface tension is complex. Over the years, a number of theoretical, empirical and semi-empirical models have been devel- oped that are not always applicable to all types of mixtures [4].A falling liquid film evaporator is an example of a system where surface tension is very important. Surface tension gradients, the so-called Marangoni effect, provide a fluid diversion mechanism whereby films may breakdown. Film breakdown is the condition that occurs when the evaporator surface is not completely wetted by the fluid. Breakdown provides a system deficiency because the entire evaporator surface is not utilized, and thus it provides an operating limit for the system [5,6]. In the present work, we report surface tensions of the ternary system (water + acetonitrile + 1,2- ethandiol) at T = 298.15 K and the corresponding binary mixtures, i.e. (water + acetonitrile), (water + 1,2-ethandiol), and (acetoni- trile + 1,2-ethandiol) at T = (283.15, 298.15, and 308.15) K. As far as we know, no literature data are available for the selected ternary system. The binary (water + acetonitrile) system covers a large range of solvatochromic parameters (dipole character, acidity, and basicity). A few empirical and thermodynamic-based equations are avail- able to correlate the surface tension; some of them have recently proposed and are well founded on a thermodynamic basis. Li et al. proposed equations to correlate the surface tension data with the composition in the binary systems which are based on the Wilson equation for the excess Gibbs free energy [7,8]. Another two-parameter equation was developed by Fu et al. which relies the local composition concept [9]. On the other hand, empirical equations such as those from Redlich–Kister [10], Myers–Scott [11] have also been applied for the correlation of binary surface tension data. In the present paper, surface tension data of the binary mixtures are correlated with the models of Redlich–Kister (RK), Myers–Scott (MS), Fu et al. (FLW) and Wang–Chen (WCH) [12]. Also, the models of Fu et al., Wang–Chen and Kalies et al. [13] were applied for ter- nary homogeneous liquid mixtures. It was anticipated that surface tension could be predicted for the ternary system just by using the surface tension of the individual pure components and evaluated binary coefficients. 0021-9614/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2010.09.003 ⇑ Corresponding author. Tel./fax: +98 0811 8257407. E-mail addresses: rafati_aa@yahoo.com, aa_rafati@basu.ac.ir (A.A. Rafati). J. Chem. Thermodynamics 43 (2011) 248–254 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct