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Ultrasonic velocity, viscosity, density and excess properties of binary mixture of dimethyl sulphoxide with propanoic acid and n-butyric acid
Journal of Molecular Liquids 135 (2007) 166 – 169 www.elsevier.com/locate/molliq
Ultrasonic velocity, viscosity, density and excess properties of binary mixture of dimethyl sulphoxide with propanoic acid and n-butyric acid Vijay Kumar Misra, Isht Vibhu, Rahul Singh, Manisha Gupta ⁎, J.P. Shukla Department of Physics, University of Lucknow, Lucknow — 226007, India Received 22 June 2006; accepted 12 December 2006 Available online 27 February 2007
Abstract Ultrasonic velocity (u), viscosity (η) and density (ρ) have been measured for binary mixtures of dimethyl sulphoxide (DMSO) with propanoic acid (PA) and n-butyric acid (BA) at three temperature 293 K, 303 K and 313 K, over the entire range of composition. Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess free energy of activation for viscous flow ΔG⁎E have been calculated using experimental values of ultrasonic velocity (u), density (ρ) and viscosity (η). Deviation in isentropic compressibility (ΔβS) and viscosity (Δη) as well as excess free energy of activation for viscous flow (ΔG⁎E) were plotted against the mole fraction of DMSO over the entire composition range. The values of ΔβS have been found to be negative whereas the values of ΔG⁎E and Δη were positive for both the mixtures over the entire composition range. The strength and the nature of interaction between the molecules of DMSO with propanoic acid and n-butyric acid have been discussed. © 2007 Published by Elsevier B.V. Keywords: Ultrasonic velocity; Viscosity; Deviation in isentropic compressibility
1. Introduction Study of thermodynamic properties of binary mixtures of varying composition and environment provides opportunities for continuous adjustment of observable properties and thus yields an experimental background for optimizing the choice of solvent in manifold applications [1–3]. The study on the possible change of thermodynamic properties of mixtures and their degree of deviation from ideality has been found to be an excellent qualitative and quantitative way to obtain information about the molecular structure and intermolecular forces in liquid mixtures. This has given impetus to the theoretical and experimental investigations on excess thermodynamic properties of liquid mixtures [4–6]. In our research program, an attempt has been made to study the behaviour of dimethyl sulphoxide (DMSO) with propanoic
⁎ Corresponding author. E-mail address: [email protected] (M. Gupta). 0167-7322/$ - see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.molliq.2006.12.028
acid (PA) and n-butyric acid (BA) as binary mixtures covering the entire range of composition. DMSO has a wide range of applicability as a solvent in chemical and biological processes involving both plants and animals. Due to the presence of a – S_O group it is a highly polar aprotic solvent and has large dipole moment and permittivity (μ = 3.9 D and ϵ = 46.6 at 298.15 K) [7]. Carboxylic acids are used in material engineering as chemical constituents. As a chemical constituent it is used in paints, ink, pesticides, cosmetics, plastics and rubber. It is also used as natural colorants for food and Nutraceutical. Electronegative substituents near the carboxyl groups act to increase the acidity. The present paper reports the deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess energy of activation of viscous flow ΔG⁎E for the binary mixtures of DMSO with propanoic acid and n-butyric acid at T = 293, 303 and 313 K. The aim of the present study is to analyze the disruption of self association in propanoic acid and n-butyric acid and the breaking of dipole–dipole interactions of DMSO along with the interaction between the –S_O group of
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
DMSO and the –COOH group of propanoic acid and n-butyric acid respectively.
167
compressibility, density, viscosity and molar volume of mixture. βSi, ρi, ηi and Vmi (i = 1, 2) denote the isentropic compressibility, density, viscosity, and molar volume of the ith component.
2. Experimental details 4. Results and discussion Ultrasonic velocity was measured using the ultrasonic interferometer (model M-83) supplied by Mittal Enterprises, New Delhi. Standard values of velocity for benzene and carbon tetrachloride at 293, 303 and 313 K were calculated from literature values of velocity at 298 K and −du / dt (the rate of change of velocity with temperature). The accuracy in velocity measurements was ± 0.08%. The temperature during the experiment was controlled by circulating water around the liquid cell from the thermostatically controlled adequately stirred water bath (accuracy ± 0.1 °C). A single capillary pycnometer was used to measure the density of the liquid mixtures. The volume of the bulb of the capillary pycnometer was 8 ml. Viscosity of mixtures was determined by using Ostwald's viscometer. Pycnometer and viscometer were kept inside a double wall glass jacket, in which water from a thermostatically controlled water bath was circulated. The inner cylinder of this doubled wall jacket was filled with water of the desired temperature to establish and maintain thermal equilibrium. The accuracy in the viscosity and density measurements was with in ± 0.5%. DMSO, propanoic acid and n-butyric acid used for study were of LR grade. DMSO, propanoic acid and n-butyric acid were obtained from Ranbaxy, Sd Fine and Merck, respectively. All the chemicals used were purified by standard procedures [8]. The samples were kept in tightly sealed bottles to minimize the absorption of atmospheric moisture. 3. Theory Isentropic compressibility βS is calculated using Laplace's equation [9–11]. bS ¼ 1=u2 q
ð1Þ
Energy of activation of viscous flow ΔG⁎E is calculated using theory of reaction rates [12–14] as DG⁎ expt ¼ RT ln½ηVm =hN
ð2Þ
Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη, and excess energy of activation of viscous flow ΔG⁎E are calculated using the following equations. DbS ¼ bS −ðX1 bS1 þ X2 bS2 Þ
ð3Þ
Dη ¼ η−ðX1 η1 þ X2 η2 Þ
ð4Þ
E ΔG⁎ ¼ RT ½lnðηVm =η2 Vm2 Þ−X1 lnðη1 Vm1 =η2 Vm2 Þ
ð5Þ
where R is the universal gas constant. T is absolute temperature. u, βS, ρ, η and Vm denote the ultrasonic velocity, isentropic
Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess energy of activation of viscous flow ΔG⁎E are plotted against the mole fraction of DMSO (X1) and are shown in Figs. 1–3 respectively. It can be seen from Fig. 1 that the values of deviation in isentropic compressibility ΔβS, for DMSO + propanoic acid and DMSO + n-butyric acid are negative over the entire composition range at all temperature studied. The negative values of ΔβS suggest that the mixture is less compressible than the corresponding ideal mixture. The observed values of ΔβS for these mixtures can be explained as a result of various types of intermolecular interactions between the components. It has been reported earlier [4,15–17] that the three main types of contributions to excess thermodynamic properties of mixtures are physical, chemical and structural. 1. Physical interaction, consisting mainly of dispersion forces or weak dipole–dipole interaction, leading to a positive contribution to ΔβS and a negative contribution to ΔG⁎E and Δη. 2. Chemical interaction, which includes charge transfer forces, formation of H-bonds and other complex forming interactions making negative contribution to ΔβS and positive contribution to ΔG⁎E and Δη. 3. Structural interaction arising due to interstitial accommodation and changes in free volume. A vital role is played by sign and magnitude of deviation/ excess values in assessing the molecular rearrangement as a result of molecular interaction between the component molecules in the liquid mixtures. The negative values of ΔβS in DMSO + propanoic acid and DMSO + n-butyric acid mixture can be explained on the basis of complex formation through hydrogen bonding between the oxygen atom of (–S_O) DMSO and the hydrogen atom of propanoic and n-butyric acid. This is in accordance with the view proposed by Fort and Moore [18] according to which liquids of different molecular size usually mix with decrease in volume yielding negative ΔβS values. Negative trends in ΔβS were also reported earlier for binary mixtures of alkanols and alkanes [19]. The order of negative values of ΔβS for DMSO + propanoic acid is greater than for DMSO + n-butyric acid. The higher negative values of ΔβS for DMSO + propanoic acid mixture suggest that interaction between DMSO and propanoic acid is stronger when compared to that between DMSO and butyric acid. It is also seen from Fig. 1 that in the two mixtures ΔβS decreases as a function of mole fraction of DMSO, attains a minimum and then increases. The magnitude of ΔβS values increases with increase in temperature for the two mixtures. The effect of temperature is not very significant for DMSO + n-butyric acid mixture when temperature changes from 293 to
168
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
Fig. 1. Deviation in isentropic compressibility (ΔβS) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
303 K. However, the change in ΔβS values is quite significant, when the temperature is raised from 303 to 313 K. Some other workers [20,21] have reported similar behaviour of ΔβS. Deviation in viscosity Δη is found to be positive for the two mixtures (DMSO + propanoic acid and DMSO + nbutyric acid) over the entire composition range, which suggests the presence of strong intermolecular interaction. Deviation in the viscosity curves shows the maxima at or near those mole fractions of DMSO where values of ΔβS
Fig. 3. Excess free energy of viscous flow (ΔG⁎E) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
attain minima. This further supports the molecular association through hydrogen bonding between unlike molecules as suggested earlier by other workers [9,22]. The absolute value of Δη decreases in the two mixtures as temperature is raised. An increase in temperature decreases the self association of pure components and heteroassociation between unlike molecules, because of the increase of thermal energy. This leads to less positive values of Δη with increasing temperature as observed in the present study. Similar temperature dependence has been reported by Marigliano [21]. It can also be seen from Fig. 2 that Δη decreases significantly in the DMSO rich region where heteromolecular association acquires predominance. The variation of excess free energy of activation for viscous flow ΔG⁎E with mole fraction of DMSO (X1) is shown in Fig. 3. The values of ΔG⁎E were found to be positive in the two mixtures over the entire composition range. The positive value of ΔG⁎E gives information regarding the presence of strong interaction between unlike molecules in solvent mixtures as suggested by Oswal and Desai [23]. This supports the view that chemical interaction which may involve association due to hydrogen bonding, dipole–dipole interaction, formation of complexes due to charge transfer may lead to strong interactions [18]. 5. Conclusion
Fig. 2. Deviation in viscosity (Δη) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
The observed negative values of ΔβS and also the positive values of Δη and ΔG⁎ E suggest the existence of strong hydrogen-bonding between unlike molecules. Weak dipole– dipole interaction may also contribute to the observed results.
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
References [1] F. Commelli, S. Ottani, R. Francesconi, C. Coastellari, J. Chem. Eng. Data 47 (2002) 93. [2] B. Gracia, A. Alcalde, J.M. Leal, J.S. Matos, J. Chem. Soc., Faraday Trans. 93 (1997) 1115. [3] J. George, N.V. Sastry, S.R. Patel, M.K. Valand, J. Chem. Eng. Data 47 (2) (2002) 262. [4] A. Ali, A.K. Nain, Pramana — J. Phys. 58 (4) (2002) 695. [5] R.B. Torres, A.Z. Francesconi, P.L.O. Volpe, Fluid Phase Equilib. 200 (2002) 1. [6] H. Iloukhani, G.G. Redhi, J. Chem. Eng. Data 45 (2000) 57. [7] B.V.K. Naidu, K.C. Rao, M.C.S. Subha, J. Chem. Eng. Data 47 (2002) 379. [8] D.D. Perrin, W.L.F. Armarego, Purification of Lab Chem, 3rd Edition, Pergamon Press, Oxford, 1988. [9] P.J. Victor, D.K. Hazra, J. Chem. Eng. Data 47 (2002) 79. [10] J. Canosa, A. Rodriguez, J. Toju, J. Chem. Eng. Data 46 (2001) 846.
169
[11] S.B. Alisha, M.C.S. Suba, K.C. Rao, J. Pure Appl. Ultrason. 23 (2001) 26. [12] R. Neejus, C. Damas, D. Lemordant, R. Coudert, P. Willmann, J. Chem. Thermodyn. 34 (2002) 795. [13] A. Ali, A.K. Nain, Ind. J. Chem. 35 (A) (1996) 751. [14] A. Pal, R.K. Bhardwaj, Ind. J. Chem. 41 (A) (2002) 706. [15] S.K. Mehta, A.K. Sharma, K.K. Bhasin, R. Prakash, Fluid Phase Equilib. 201 (2002) 203. [16] S. Baluja, S. Ojha, Fluid Phase Equilib. 200 (2002) 11. [17] A. Pal, A. Kumar, B.R. Arbad, A.B. Tekale, Ind. J. Chem. 41 A (2002) 1593. [18] R.J. Fort, W.R. Moore, Trans. Faraday Soc. 16 (1965) 2102. [19] D.G. Salgado, C.A. Tover, C.A. Cerdeirina, E. Carballo, L. Romani, Fluid Phase Equilib. 199 (2002) 121. [20] F. Commelli, S. Ottani, R. Francesconi, C. Castellari, J. Chem. Eng. Data 47 (5) (2002) 1226. [21] A.C.G. Marigliano, H.N. Solimo, J. Chem. Eng. Data 47 (2002) 796. [22] J.L. Trenjado, J.S. Matos, R. Alcalde, Fluid Phase Equilib. 200 (2002) 295. [23] S.L. Oswal, H.S. Desai, Fluid Phase Equilib. 149 (1998) 359.
Ultrasonic velocity, viscosity, density and excess properties of binary mixture of dimethyl sulphoxide with propanoic acid and n-butyric acid Vijay Kumar Misra, Isht Vibhu, Rahul Singh, Manisha Gupta ⁎, J.P. Shukla Department of Physics, University of Lucknow, Lucknow — 226007, India Received 22 June 2006; accepted 12 December 2006 Available online 27 February 2007
Abstract Ultrasonic velocity (u), viscosity (η) and density (ρ) have been measured for binary mixtures of dimethyl sulphoxide (DMSO) with propanoic acid (PA) and n-butyric acid (BA) at three temperature 293 K, 303 K and 313 K, over the entire range of composition. Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess free energy of activation for viscous flow ΔG⁎E have been calculated using experimental values of ultrasonic velocity (u), density (ρ) and viscosity (η). Deviation in isentropic compressibility (ΔβS) and viscosity (Δη) as well as excess free energy of activation for viscous flow (ΔG⁎E) were plotted against the mole fraction of DMSO over the entire composition range. The values of ΔβS have been found to be negative whereas the values of ΔG⁎E and Δη were positive for both the mixtures over the entire composition range. The strength and the nature of interaction between the molecules of DMSO with propanoic acid and n-butyric acid have been discussed. © 2007 Published by Elsevier B.V. Keywords: Ultrasonic velocity; Viscosity; Deviation in isentropic compressibility
1. Introduction Study of thermodynamic properties of binary mixtures of varying composition and environment provides opportunities for continuous adjustment of observable properties and thus yields an experimental background for optimizing the choice of solvent in manifold applications [1–3]. The study on the possible change of thermodynamic properties of mixtures and their degree of deviation from ideality has been found to be an excellent qualitative and quantitative way to obtain information about the molecular structure and intermolecular forces in liquid mixtures. This has given impetus to the theoretical and experimental investigations on excess thermodynamic properties of liquid mixtures [4–6]. In our research program, an attempt has been made to study the behaviour of dimethyl sulphoxide (DMSO) with propanoic
⁎ Corresponding author. E-mail address: [email protected] (M. Gupta). 0167-7322/$ - see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.molliq.2006.12.028
acid (PA) and n-butyric acid (BA) as binary mixtures covering the entire range of composition. DMSO has a wide range of applicability as a solvent in chemical and biological processes involving both plants and animals. Due to the presence of a – S_O group it is a highly polar aprotic solvent and has large dipole moment and permittivity (μ = 3.9 D and ϵ = 46.6 at 298.15 K) [7]. Carboxylic acids are used in material engineering as chemical constituents. As a chemical constituent it is used in paints, ink, pesticides, cosmetics, plastics and rubber. It is also used as natural colorants for food and Nutraceutical. Electronegative substituents near the carboxyl groups act to increase the acidity. The present paper reports the deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess energy of activation of viscous flow ΔG⁎E for the binary mixtures of DMSO with propanoic acid and n-butyric acid at T = 293, 303 and 313 K. The aim of the present study is to analyze the disruption of self association in propanoic acid and n-butyric acid and the breaking of dipole–dipole interactions of DMSO along with the interaction between the –S_O group of
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
DMSO and the –COOH group of propanoic acid and n-butyric acid respectively.
167
compressibility, density, viscosity and molar volume of mixture. βSi, ρi, ηi and Vmi (i = 1, 2) denote the isentropic compressibility, density, viscosity, and molar volume of the ith component.
2. Experimental details 4. Results and discussion Ultrasonic velocity was measured using the ultrasonic interferometer (model M-83) supplied by Mittal Enterprises, New Delhi. Standard values of velocity for benzene and carbon tetrachloride at 293, 303 and 313 K were calculated from literature values of velocity at 298 K and −du / dt (the rate of change of velocity with temperature). The accuracy in velocity measurements was ± 0.08%. The temperature during the experiment was controlled by circulating water around the liquid cell from the thermostatically controlled adequately stirred water bath (accuracy ± 0.1 °C). A single capillary pycnometer was used to measure the density of the liquid mixtures. The volume of the bulb of the capillary pycnometer was 8 ml. Viscosity of mixtures was determined by using Ostwald's viscometer. Pycnometer and viscometer were kept inside a double wall glass jacket, in which water from a thermostatically controlled water bath was circulated. The inner cylinder of this doubled wall jacket was filled with water of the desired temperature to establish and maintain thermal equilibrium. The accuracy in the viscosity and density measurements was with in ± 0.5%. DMSO, propanoic acid and n-butyric acid used for study were of LR grade. DMSO, propanoic acid and n-butyric acid were obtained from Ranbaxy, Sd Fine and Merck, respectively. All the chemicals used were purified by standard procedures [8]. The samples were kept in tightly sealed bottles to minimize the absorption of atmospheric moisture. 3. Theory Isentropic compressibility βS is calculated using Laplace's equation [9–11]. bS ¼ 1=u2 q
ð1Þ
Energy of activation of viscous flow ΔG⁎E is calculated using theory of reaction rates [12–14] as DG⁎ expt ¼ RT ln½ηVm =hN
ð2Þ
Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη, and excess energy of activation of viscous flow ΔG⁎E are calculated using the following equations. DbS ¼ bS −ðX1 bS1 þ X2 bS2 Þ
ð3Þ
Dη ¼ η−ðX1 η1 þ X2 η2 Þ
ð4Þ
E ΔG⁎ ¼ RT ½lnðηVm =η2 Vm2 Þ−X1 lnðη1 Vm1 =η2 Vm2 Þ
ð5Þ
where R is the universal gas constant. T is absolute temperature. u, βS, ρ, η and Vm denote the ultrasonic velocity, isentropic
Deviation in isentropic compressibility ΔβS, deviation in viscosity Δη and excess energy of activation of viscous flow ΔG⁎E are plotted against the mole fraction of DMSO (X1) and are shown in Figs. 1–3 respectively. It can be seen from Fig. 1 that the values of deviation in isentropic compressibility ΔβS, for DMSO + propanoic acid and DMSO + n-butyric acid are negative over the entire composition range at all temperature studied. The negative values of ΔβS suggest that the mixture is less compressible than the corresponding ideal mixture. The observed values of ΔβS for these mixtures can be explained as a result of various types of intermolecular interactions between the components. It has been reported earlier [4,15–17] that the three main types of contributions to excess thermodynamic properties of mixtures are physical, chemical and structural. 1. Physical interaction, consisting mainly of dispersion forces or weak dipole–dipole interaction, leading to a positive contribution to ΔβS and a negative contribution to ΔG⁎E and Δη. 2. Chemical interaction, which includes charge transfer forces, formation of H-bonds and other complex forming interactions making negative contribution to ΔβS and positive contribution to ΔG⁎E and Δη. 3. Structural interaction arising due to interstitial accommodation and changes in free volume. A vital role is played by sign and magnitude of deviation/ excess values in assessing the molecular rearrangement as a result of molecular interaction between the component molecules in the liquid mixtures. The negative values of ΔβS in DMSO + propanoic acid and DMSO + n-butyric acid mixture can be explained on the basis of complex formation through hydrogen bonding between the oxygen atom of (–S_O) DMSO and the hydrogen atom of propanoic and n-butyric acid. This is in accordance with the view proposed by Fort and Moore [18] according to which liquids of different molecular size usually mix with decrease in volume yielding negative ΔβS values. Negative trends in ΔβS were also reported earlier for binary mixtures of alkanols and alkanes [19]. The order of negative values of ΔβS for DMSO + propanoic acid is greater than for DMSO + n-butyric acid. The higher negative values of ΔβS for DMSO + propanoic acid mixture suggest that interaction between DMSO and propanoic acid is stronger when compared to that between DMSO and butyric acid. It is also seen from Fig. 1 that in the two mixtures ΔβS decreases as a function of mole fraction of DMSO, attains a minimum and then increases. The magnitude of ΔβS values increases with increase in temperature for the two mixtures. The effect of temperature is not very significant for DMSO + n-butyric acid mixture when temperature changes from 293 to
168
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
Fig. 1. Deviation in isentropic compressibility (ΔβS) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
303 K. However, the change in ΔβS values is quite significant, when the temperature is raised from 303 to 313 K. Some other workers [20,21] have reported similar behaviour of ΔβS. Deviation in viscosity Δη is found to be positive for the two mixtures (DMSO + propanoic acid and DMSO + nbutyric acid) over the entire composition range, which suggests the presence of strong intermolecular interaction. Deviation in the viscosity curves shows the maxima at or near those mole fractions of DMSO where values of ΔβS
Fig. 3. Excess free energy of viscous flow (ΔG⁎E) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
attain minima. This further supports the molecular association through hydrogen bonding between unlike molecules as suggested earlier by other workers [9,22]. The absolute value of Δη decreases in the two mixtures as temperature is raised. An increase in temperature decreases the self association of pure components and heteroassociation between unlike molecules, because of the increase of thermal energy. This leads to less positive values of Δη with increasing temperature as observed in the present study. Similar temperature dependence has been reported by Marigliano [21]. It can also be seen from Fig. 2 that Δη decreases significantly in the DMSO rich region where heteromolecular association acquires predominance. The variation of excess free energy of activation for viscous flow ΔG⁎E with mole fraction of DMSO (X1) is shown in Fig. 3. The values of ΔG⁎E were found to be positive in the two mixtures over the entire composition range. The positive value of ΔG⁎E gives information regarding the presence of strong interaction between unlike molecules in solvent mixtures as suggested by Oswal and Desai [23]. This supports the view that chemical interaction which may involve association due to hydrogen bonding, dipole–dipole interaction, formation of complexes due to charge transfer may lead to strong interactions [18]. 5. Conclusion
Fig. 2. Deviation in viscosity (Δη) as a function of mole fraction of DMSO (X1) for DMSO + propanoic acid mixture (mixture-1) and DMSO + n-butyric acid mixture (mixture-2).
The observed negative values of ΔβS and also the positive values of Δη and ΔG⁎ E suggest the existence of strong hydrogen-bonding between unlike molecules. Weak dipole– dipole interaction may also contribute to the observed results.
V.K. Misra et al. / Journal of Molecular Liquids 135 (2007) 166–169
References [1] F. Commelli, S. Ottani, R. Francesconi, C. Coastellari, J. Chem. Eng. Data 47 (2002) 93. [2] B. Gracia, A. Alcalde, J.M. Leal, J.S. Matos, J. Chem. Soc., Faraday Trans. 93 (1997) 1115. [3] J. George, N.V. Sastry, S.R. Patel, M.K. Valand, J. Chem. Eng. Data 47 (2) (2002) 262. [4] A. Ali, A.K. Nain, Pramana — J. Phys. 58 (4) (2002) 695. [5] R.B. Torres, A.Z. Francesconi, P.L.O. Volpe, Fluid Phase Equilib. 200 (2002) 1. [6] H. Iloukhani, G.G. Redhi, J. Chem. Eng. Data 45 (2000) 57. [7] B.V.K. Naidu, K.C. Rao, M.C.S. Subha, J. Chem. Eng. Data 47 (2002) 379. [8] D.D. Perrin, W.L.F. Armarego, Purification of Lab Chem, 3rd Edition, Pergamon Press, Oxford, 1988. [9] P.J. Victor, D.K. Hazra, J. Chem. Eng. Data 47 (2002) 79. [10] J. Canosa, A. Rodriguez, J. Toju, J. Chem. Eng. Data 46 (2001) 846.
169
[11] S.B. Alisha, M.C.S. Suba, K.C. Rao, J. Pure Appl. Ultrason. 23 (2001) 26. [12] R. Neejus, C. Damas, D. Lemordant, R. Coudert, P. Willmann, J. Chem. Thermodyn. 34 (2002) 795. [13] A. Ali, A.K. Nain, Ind. J. Chem. 35 (A) (1996) 751. [14] A. Pal, R.K. Bhardwaj, Ind. J. Chem. 41 (A) (2002) 706. [15] S.K. Mehta, A.K. Sharma, K.K. Bhasin, R. Prakash, Fluid Phase Equilib. 201 (2002) 203. [16] S. Baluja, S. Ojha, Fluid Phase Equilib. 200 (2002) 11. [17] A. Pal, A. Kumar, B.R. Arbad, A.B. Tekale, Ind. J. Chem. 41 A (2002) 1593. [18] R.J. Fort, W.R. Moore, Trans. Faraday Soc. 16 (1965) 2102. [19] D.G. Salgado, C.A. Tover, C.A. Cerdeirina, E. Carballo, L. Romani, Fluid Phase Equilib. 199 (2002) 121. [20] F. Commelli, S. Ottani, R. Francesconi, C. Castellari, J. Chem. Eng. Data 47 (5) (2002) 1226. [21] A.C.G. Marigliano, H.N. Solimo, J. Chem. Eng. Data 47 (2002) 796. [22] J.L. Trenjado, J.S. Matos, R. Alcalde, Fluid Phase Equilib. 200 (2002) 295. [23] S.L. Oswal, H.S. Desai, Fluid Phase Equilib. 149 (1998) 359.