Excess Molar Enthalpies for the Binary and Ternary Mixtures of Cyclohexane, Tetrahydropyran, and Piperidine at 308.15 K and Atmospheric Pressure: Experimental Measurements and Correlations Farid B. Belaribi,* ,†,‡,§ Ghe ´nima Boukais-Belaribi, †,‡,§ Amir H. Mohammadi, ‡ and Dominique Richon* ,‡ Laboratoire de Thermodynamique et Mode ´lisation Mole ´culaire, Faculte ´ de Chimie, Universite ´ des Sciences et de la Technologie Houari Boumediene, BP 32 El Alia, 16111 Bab Ezzouar, Alge ´rie, and MINES ParisTech, CEP/TEP, Centre Energe ´tique et Proce ´de ´s, 35 Rue Saint Honore ´, 77305 Fontainebleau, France Excess molar enthalpies for the binary and ternary mixtures of cyclohexane, tetrahydropyran, and piperidine have been measured using a Calvet microcalorimeter at 308.15 K and atmospheric pressure. All of the binary and ternary systems show endothermic behavior. The experimental binary results are correlated using the Redlich-Kister equation. The excess molar enthalpies for the ternary mixture are correlated using the Cibulka equation. The capability of an artificial neural network algorithm to model these data is finally studied. Introduction Excess thermodynamic properties of liquid mixtures are of great interest to conveniently design industrial processes and also to provide useful information on the molecular interactions required for optimizing thermodynamic models. In comparison with the experimental data reported in the literature for binary systems, the experimental data for ternary mixtures remain quite scarce. Cyclic ethers and amines represent two particularly interesting families of molecules for the purpose of testing models. Some hexacyclic aliphatic compounds, such as piperi- dine, tetrahydropyran, 1,4-dioxane, and cyclohexane, which are of very similar size and shape, differ in only one functional group (NH, O, CH 2 ) and are therefore of interest to study excess molar enthalpies of their binary and ternary mixtures. In our previous papers, 1,2 we have reported experimental excess molar enthalpies for binary and ternary mixtures of cyclohexane, with cyclic ethers (tetrahydropyran and 1,4-dioxane). In this com- munication, we continue our previous study 2 and report experimental excess molar enthalpies at 308.15 K and atmo- spheric pressure, for the binary and ternary mixtures of cyclohexane with tetrahydropyran (a cyclic monoether) and piperidine (a self-associated secondary cyclic amine). Few excess molar enthalpy data, for these binary systems, have been reported in the literature, at (293.15 to 298.15) K. 3-7 To our knowledge, there is no other literature data on the excess molar enthalpy of the ternary mixture. Our experimental data have been measured using a Calvet microcalorimeter. The Redlich- Kister equation 8 is used to correlate the experimental binary data. The experimental ternary data are correlated using the Cibulka equation. 9 The capability of artificial neural network (ANN) algorithm 10 as an alternative method to model these (binary and ternary) data is finally investigated. Experimental Section Materials. Purities and suppliers of materials are provided in Table 1. Experimental Apparatus and Procedure. The experimental enthalpy data were measured at atmospheric pressure by means of a flow calorimeter (Calvet microcalorimeter, model C80, Setaram, Lyon, France). The temperature was maintained constant at (308.15 ( 0.02) K. The mixtures were prepared by mass using a Mettler PE 160 balance (precision of ( 0.1 mg), ensuring a probable uncertainty in the mole fraction less than 10 -4 . The apparatus and procedures were tested by determining excess enthalpies for the standard system benzene + cyclohex- ane, and the results were found to differ by less than 3 % from those of Marsh. 11 In our study of the ternary system, the excess molar enthalpy H m,12+3 E was determined for several pseudobinary mixtures in which component 3 (piperidine) was added to binary mixtures of components 1 (cyclohexane) and 2 (tetrahydropyran). For this purpose, binaries with fixed mole ratios, x 1 /x 2 , were prepared by mass. The excess molar enthalpy H m,123 E of the ternary mixture was then obtained from the relationship H m,123 E ) H m,12+3 E + (1 - x 3 )H m,12 E (1) where x 3 is the mole fraction of piperidine and H m,12 E is the excess molar enthalpy of the particular binary mixture. Results and Discussion The experimental excess molar enthalpies, for binary mixtures of cyclohexane, tetrahydropyran, and piperidine, are reported in Table 2 and plotted in Figure 1 along with some available literature data, at (283.15, 293.15, and 298.15) K, 3-6 for * Corresponding authors. E-mail: farid.belaribi@mines-paristech.fr and f_belaribi@yahoo.com (F.B.B.); dominique.richon@mines-paristech.fr (D.R.). Tel./Fax: +(213) 21 248008 (F.B.B.). Tel.: +(33) 1 64 69 49 65 (D.R.). Fax: +(33) 1 64 69 49 68 (D.R.). † Universite ´ des Sciences et de la Technologie Houari Boumediene. ‡ CEP/TEP, Centre Energe ´tique et Proce ´de ´s. § On sabbatical leave. Table 1. Purities and Suppliers of Materials chemical CAS number supplier purity (GC) cyclohexane 110-89-4 Merck > 0.99 tetrahydropyran 142-68-7 Fluka > 0.99 piperidine 110-89-4 Merck > 0.99 J. Chem. Eng. Data 2010, 55, 303–307 303 10.1021/je900347f CCC: $40.75  2010 American Chemical Society Published on Web 09/16/2009