Studies on Volumetric and Viscometric Properties of Some Binary and Ternary Liquid Systems

Abstract

Densities and viscosities of binary mixtures of Methanol +DMF, Ethanol +DMF, n-Propanol +DMF, iso-Propanol +DMF, n-Butanol +DMF, iso-Butanol +DMF, tert-Butanol +DMF, nAmyl alcohol +DMF, iso-Amyl alcohol +DMF and ternary mixtures of n-Propanol +0.02M SDS in DMF, n-Butanol +0.02M SDS in DMF and n-Amyl alcohol +0.02M SDS in DMF have been studied over the entire range of composition (0 <X2 < 1) at 298.15- 323.15K with an interval of 5K except Methanol. Methanol system was studied at 298.15K, 303.15K and 308.15K owing to its lower boiling point. The excess molar volumes,temperatures. The values ofVEwere calculated from the densities of the mixtures at different temperature. The values of VE for all the systems are negative over the entire range of composition, showing minima at 0.6 mole fraction of Methanol, - 0.2-0.3 mole fraction of Ethanol, - 0.1-0.2 mole fraction of n-Propanol and - 0.2 mole fraction of iso-Propanol, - 0.10.2 mole fraction of n-Butanol, -0.2 mole fraction of iso-Butanol, -0.3 mole fraction of tert-Butanol, -0.2 mole fraction of n-Amyl alcohol and -0.6 mole fraction of iso-Amyl alcohol. The values of JJE for the most of studied alcohols are negative throughout the whole range of composition at lower temperature (298.15K-303.15K), but at higher temperature, it shows positive throughout the whole range of composition. The observed values of VE for the mixtures have been explained in terms of physical, chemical, and geometrical contributions. The physical interactions, that is, nonspecific interactions between the real species present in the mixture, involve mainly dispersion force giving a positive contribution. The chemical or specific intermolecular interactions result in a volume decrease and these interactions include formation of hydrogen bonds and other complex-forming interactions. The structural contributions are mostly negative and arise from several effects, especially from interstitial accommodation and changes of free volume.

The viscosity coefficients, η of all the above mixtures at all the six different temperatures have also been determined. The viscosities increase initially slowly up to -0.6 mole fraction of Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, tert-Butanol, n-Amyl alcohol and iso-Amyl alcohols and later on, the viscosity increases sharply until that of pure alcohol is reached specially at lower temperature. For Methanol, viscosity decrease slowly on continued

addition of Methanol. Viscosity decreases with rise of temperature. In pure state the viscosity of alcohols has been found to be in the order of, tert-Butanol> n-Amyl alcohol> iso-Amyl alcohol>iso-Butanol>n-Butanol> iso-Propanol> n- Propanol> Ethanol> Methanol There is a marked decrease in the viscosity with increase of temperature for all the isomeric studied alcohols. At 298.15K, viscosity is found to be in the order: tert-Butanol> iso-Butano!>n-Butanol iso-Propanol> n-Propanol, which however changes to n-Butanol >iso-Butanol> tert-Butanol n-Propanol> iso-Propano! at 323.15K. This ascribed that the branched chain isomers are less stable than linear chain isomers at higher temperature and vice versa. The η E values are found to be positive or negative, indicating that the DMF solutions of alcohols are non ideal. Excess viscosities are negative at all the temperatures over the entire range of composition for all the systems except Methanol with minima occurring between 0.6-0.9 mole fraction of n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, tert-Butanol, n-Amyl alcohol and iso-Amyl alcohol. Excess viscosity of Methanol is positive at all the temperatures over the entire range of composition and show maxima in the DMF rich region at 0.2-0.4 mole fraction of Methanol. Excess viscosity of Ethanol is negative and show minima at 0.4-0.5 mole fraction of Ethanol. The position of maxima and minima virtually does not change remarkably with the variation of temperature. The heights of the minima are in the order: tert-Butanol> n-Amyl alcohol> iso-Amyl alcohol—iso-Butanol>n-Butanol> iso-Propanol> n- Propanol> Ethanol. The negative VE, positive and positive interaction parameter e for the DMF Methanol system may be ascribed that the interaction is strong, namely formation of Fl-bonding between DMF and Methanol. The negative yE, negative ηE and negative E for the DMF + rest of the studied alcohols systems indicate that dispersion force is dominant. For the later case,P'E is negative due to the segmental inclusion of DMF in the interstices of polymolecular alkanol aggregates. Some disruptive force causing volume expansion may be present, but it is more than compensated for by volume contraction through the segmental inclusion of DMF.

The thermodynamic parameters such as, free energy (∆GH), enthalpy (∆H'H) and entropy (∆SH) change of activation for the viscous flow for these systems were determined for the entire range of composition by using Eyring's equation. The free energy (∆GH) were found to be positive in magnitude indicating that the kinetic species involved in forming cavities or holes in the liquid medium is given by the work required in forming the hole against surface tension of the solution. The excess properties (yE, ηE∆GHE) data have been fitted by the least square method to the four parameter Redlich-Kister equation and the values of the parameter a1 have been reported. Although the value of density and viscosity of the studied systems of 0.02M SDS in DMF solutions are slightly higher than the pure DMF solutions, but no appreciable change in the volumetric and viscometric properties were observed by the addition of the surfactants.