Korean J. Chem. Eng., 26(3), 806-811 (2009) SHORT COMMUNICATION 806 † To whom correspondence should be addressed. E-mail: mg_kim@knu.ac.kr Excess molar volumes and molar enthalpies in the binary mixtures of {x 1 CH 3 CHClCH 2 Cl+x 2 CH 3 (CH 2 ) n− 1 OH} (n=1 to 4) at T=298.15 K Dipak Sen and Moon-Gab Kim † School of Applied Chemical Engineering, Kyungpook National University, Sangju 742-711, Korea (Received 25 August 2008  accepted 11 December 2008) Abstract−The excess molar volumes V m E and excess molar enthalpies H m E at T=298.15 K and atmospheric pressure for the binary systems {x 1 CH 3 CHClCH 2 Cl+x 2 CH 3 (CH 2 ) n−1 OH} (n=1 to 4) have been determined from density measure- ments by using a digital vibrating-tube densimeter and an isothermal calorimeter with flow-mixing cell, respectively. The 1-alkanols are methanol, ethanol, 1-propanol and 1-butanol. The V m E values of the binary mixtures increase with chain length of the 1-alkanols, resulting in entire negative V m E values for methanol, ‘S-shaped’ for ethanol, being nega- tive at low and positive at high mole fraction of 1,2-dichloropropane, and entire positive V m E values for both 1-propanol and 1- butanol. The H m E values for all systems show an endothermic effect (positive values), which exhibits a regular increase in magnitude when the number of -CH 2 - group in 1-alkanols is progressively increased and maximum values of H m E vary- ing from 741 J·mol −1 (methanol) to 1,249 J·mol −1 (1-butanol) around x 1 =0.63-0.72. The experimental results of both H m E and V m E were fitted to Redlich-Kister equation to correlate the composition dependence. The experimental H m E data were also used to test the suitability of the Wilson, NRTL, and UNIQUAC models. The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results except for the system containing methanol. Key words: Excess Molar Properties, Redlich-Kister Equation, Thermodynamic Models, 1,2-Dichloropropane, 1-Alkanols INTRODUCTION Thermo-physical properties are beneficial for characterizing the type and magnitude of molecular interaction in these mixtures, giv- ing important information in many practical problems concerning process design and simulation. In addition, knowledge of these excess molar properties can be useful in predicting the solution behavior of mixtures. This paper is part of our continuous research program based on the measurements of excess properties of binary mixtures containing 1,2-dichloropropane (1,2-DCP) [1-3], which is used as solvent for oil, fats, resin and rubber [4]. The literature offers experi- mental data of V m E and H m E for several mixtures of {1-chloroalkane+ 1-alkanols} [5,6] and { α, ω-dichloroalkane+1-butanol or 1-heptanol} [7] and only excess volume for binary mixture of {1,3-dichloro- propane+isomeric butanols} [8]. To our knowledge, no efforts, how- ever, have been made to provide V m E and H m E of these 1-alkanols: methanol, ethanol, 1-propanol, and 1-butanol with particular 1,2- DCP. The excess thermodynamic properties of mixtures containing polar and self-associated components show significant deviations from ideality due to not only the difference in molecular size and shape but also hydrogen-bonding and dipolar interaction between unlike molecules. Obviously, 1-alkanols are polar compounds with hydrophilic character and strongly self-associated by hydrogen bond through the hydroxyl group [9]. The dipole moment and dielectric constant at T=298.15 K are as follows: µ=1.69 D, ε=33.62 for meth- anol, µ =1.69 D, ε =25.0 for ethanol, µ =1.67 D, ε =22.2 for 1-pro- panol, µ=1.66 D, ε=17.8 for 1-butanol [10]. This leads to a decrease in polarity of -OH in the longer chain 1-alkanols. Likewise, 1,2- DCP is a polar compound whose dipole moment is 1.87 (D) [10] at T=298.15 K and that is self-associated by dipole-dipole interac- tion. Polarity, self-association, and hydrogen bond are the main char- acteristics of the compounds, which cause the deviation from the ideality. The aim of this paper is to collect set of values of excess prop- erties, V m E and H m E of these binary mixtures at T=298.15 K and atmo- spheric pressure over the whole concentration range. The second- ary aspect is to evaluate how chain length of 1-alknols can affect on V m E and H m E values of these mixtures by the addition of 1,2-DCP. The V m E and H m E at T=298.15 K were correlated by Redlich-Kister equation [11]. Thermodynamic models (Wilson, NRTL, and UNI- QUAC models [12-14]) based on the local-composition theory were also examined for the suitability by correlating experimental H m E data with compositions. EXPERIMENTAL SECTION 1. Materials 1,2-DCP (Fluka, >99 mass %), methanol (Aldrich, >99.9%), eth- anol (Aldrich, >99.9 %), 1-propanol (Aldrich, >99.7 %), and 1-butanol (Aldrich, >99.8%) were used without further purification but de- gassed by means of an ultrasonic bath. HPLC grade water (Fisher Scientific, >99.7%) has been used for calibration of the refracto- meter and densimeter. An analysis of the chemicals by gas chro- matography (Shimadzu, model 17A chromatograph with capillary column type, CBP-10 and FID) showed that all cases were better than 0.99 by mass fraction. The purity of the chemicals was also checked by measuring and comparing the refractive indices and densities at T=298.15 K and atmosphere pressure with their corre-