Laboratoire de Chimie des matériaux The experimental Redlich-kister Q for the ratio ∆η/x1,(1-x1) of the viscosities deviations for DMA (1) + FA (2) mixtures against mole fraction x1 in DMA. Redlich-Kister function Q for the ratio ∆Ea/x1(1- x1) of the deviation energy for DMA (1) + FA (2) mixtures against mole fraction x1 in DMA. Correlation between energy of activation(Ea) and of viscosity for DMA (1) + FA (2) mixtures versus molar fraction x1 in DMA.. C o n c l u s i o n Redlich-kister function of excess molar volume for DMA (1) + FA (2) mixtures in the temperature range versus molar fraction x1 in DMA. Excess molar volume for DMA (1) + FA (2) mixtures versus molar fraction in DMA. On the temperature-dependence of viscosity and excess molar volume in formamide + N,N-dimethylacetamide liquid mixtures Z. Barhoumi (1),* N. Ouerfelli (1), Debashis Das (2), N. Amdouni (1). (1) Unité de Recherche Physico-Chimie des Matériaux, Département de Chimie, Faculté des Sciences de Tunis, (FST), Campus Universitaire, 2092 El Manar Tunisie. (2) Department of Chemistry, Dinhata College, Dinhata, 736135 Cooch-Behar, West Bengal, India. * e-mail : barhoumi.zina@yahoo.com (Barhoumi Zina ). Société Chimique de Tunisie 41èmes Journées de Calorimétrie et d’Analyse Thermique 14 - 16 Mai 2010 - Hôtel Eldorador Ksar Rouge, Tozeur – Tunisie. INTRODUCTION Dynamic viscosity (η = ρ.n) were obtained from the density (ρ)and kinematic viscosity(n) measurements using DMA-4500 digital vibrating tube densitometer and an Ubbelohde-type viscometer in the temperature range (298.15 to 318.15 K) in dimethylacetamide (DMA) + formamide (FA) binary liquid mixtures over the entire range of mole fraction. Deviation properties of mixtures surplus is the difference between the actual value of a large property and the value which it would have if the system behaved linearly, and are therefore useful in the study of molecular interactions and arrangements. For the case where the property, including various methods of correlation equations Arrhenius equations Redlich-Kister equation and Herráez were applied to evaluate the experimental data, polynomials excess mole fraction for each fixed temperature and the Arrhenius equation as-cons reciprocal absolute temperature (1/T) at each fixed composition. We note that the reduction of the Redlich-Kister function Qη,T (x1) = Δη/(x1x2) gives more information than the difference in viscosity. Similarly, the reduced molar volume on Redlich (VEx), as well as viscosity deviations in viscosity (Δη) and derived properties of liquid mixtures containing amide which constitute an important tool in the interpretation of complex molecules biological interest. The results were fitted with Redlich-Kister polynomials against mole fraction for each fixed temperature and the Arrhenius equation, as the temperature at each fixed composition using KaleidaGraph 4.1 soft. Excees viscosities for DMA (1) + FA (2) mixtures at different temperatures against mole fraction x1 in DMA. V ex=x1M1(1/ρmix-1/ρ1)+x2M2(1/ρmix-1/ρ2) QV=Vex/(x1x2) ∆η=ηmix-(x1η1+x2η2)) DENSITY AND VISCOSITY MEASUREMENTS Ap hp 20.589°C 0.9876 Densitometer Thermostated bath Quartz Thermometer Mercury Thermometer Measurement cell Schott Gerate Logarithm of viscosity versus 1/T for DMA (1) + FA (2) mixtures Qη=∆η/x1x2 Energy activation and B for viscous flow Ea against mole fraction x1 of DMA. for DMA (1) + FA (2) mixtures The experimental Herraéz exponent polynomials Pexp,T(x1) for DMA (1) + FA (2) mixtures versus mole fraction x1 of DMA. Pexp,T(x1)=ln(ηexp-η2/η1-η2)/lnx1 QEa=∆Ea/x1x2 VEx excess molar volume is negative for the entire composition with a minimum of approximately 55% (mole) of dimethylacetamide in the range of temperature, viscosity deviations are positive over the entire range of composition with a maximum around 30% (mole) in the temperature range, the VEx and Δη indicate a strong molecular interaction between formamide and dimethylacetamide due to hydrogen bonds, It is found that the temperature dependence of viscosity can be fitted with an Arrhenius equation as η=B.exp (Ea/RT), Redlich Kister can not represent appropriately composition dependence of viscosity, We note that Qη function reduction Redlich-Kister, T (x1) = Δη / (x1x2) gives more information than the difference in viscosity, the same way, the reduced relative Qrel,η Redlich-Kister function Qrel,η,T(x1) = Qη,T(x1) / η has opportunity to eliminate the effect of the temperature of the possible release of other phenomena log (viscosity), 1/T, where T is in degrees Kelvin, is linear, the slope of such a plot gives a kind of activation energy for viscous flow, the flow of energy Ea activation increases with the mole fraction x1 in dimethylacetamide and rises to a maximum of 20 kJ.mol-1 x1 (formamide) = 0.66 showing a mutual preferential solvation (2FA and 1DMA), over the polynomial Herráez used in the viscosity can be used as a test-type interaction potential predominant at infinite dilution, B0 as shown in the equation at infinite dilution (in dimethyl formamide or formamide in dimethylacetamide) limit the exponent values Herráez polynomial can be calculated by P(xi = 0) = B0 ; far from universal exponent 0.5 and it describes the inter-dominated solute-solvent at infinite dilution,