Measurement and prediction of (solid + liquid) equilibria of (alkanediamine + biphenyl) mixtures Kamel Khimeche a,b , Abdallah Dahmani b, * a Ecole Militaire Polytechnique EMP, BP 17 Bordj-el-Bahri , Alger, Algeria b Laboratoire de Thermodynamique et de Mode ´lisation Mole ´culaire, Faculte ´ de Chimie, USTHB, BP. 32 El-Alia, 16111 Bab-Ezzouar, Alger, Algeria Received 19 September 2005; received in revised form 18 November 2005; accepted 11 December 2005 Available online 20 February 2006 Abstract Diamines represent, besides many technically important classes of substance, a particularly interesting family of molecules for the purpose of testing group-contribution models. A differential scanning calorimetry (DSC) was used to determine binary (solid + liquid) phase equilibria for {diamines NH 2 –(CH 2 ) n – NH 2 (n = 6, 8, 9, and 12) + biphenyl} mixtures. Results obtained with this technique are compared with those predicted by modified UNIFAC (Larsen and Gmehling) and DISQUAC models. It was found out that all the systems are eutectic and deviations were observed between experimental and predicted SLE. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Diamines; Polyaromatics; SLE; UNIFAC model; DISQUAC model 1. Introduction The number of organic materials that are being sepa- rated and or purified by crystallization in industrial scale operations is increasing rapidly because of the low energy consumption of such processes and the possibility of obtaining products with higher purity than can be achieved by other conventional separation operations. Unfortu- nately, for complex molecules like biological products, the data of SLE equilibria are very scarce. Alkane-a,x-diamines NH 2 –(CH 2 ) n –NH 2 are an impor- tant class of compounds in different fields of industry and particularly in the synthesis of a number of polymers. They are also thought to act as biochemical model compounds [1–4]. Thermodynamic properties and structural details of some alkane-a,x-diamines have been investigated [4–7]. Of the methods of measuring SLE, it was shown that differential scanning calorimetry (DSC) is a rapid and sen- sitive technique, broadly used for the characterization of any kind of phase change [8–11]. Following our systematic study of the thermodynamic properties of mixtures of tertiary diamines with n-heptane, or cyclohexane [12–14], and primary diamines with ben- zene, or toluene [15], and (solid + liquid) equilibrium of diamines with n-alkanes [16], it seemed interesting to test the application of DSC to the determination of SLE of complex systems including polyaromatics and alkane-a,x- diamines. In this work the results obtained in a study of the ther- modynamic properties of mixtures containing biphenyl and alkanediamines are reported. A complete data obtained by differential scanning calorimeter (DSC) of (solid + liquid) equilibria (SLE) for {biphenyl + diamines NH 2 –(CH 2 ) n – NH 2 (n = 6, 8, 9, and 12)} systems are compared with those predicted by modified UNIFAC (Larsen and Gmehling) and DISQUAC models. These models are employed with the major objective to extensively investigate their validity 0021-9614/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2005.12.004 * Corresponding author. Tel.: +213 62 42 99 93/20 24 46 43; fax: +213 21 24 73 11. E-mail address: abdahmani@yahoo.fr (A. Dahmani). www.elsevier.com/locate/jct J. Chem. Thermodynamics 38 (2006) 1192–1198