Faculty Publications
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Item Molecular interactions in glycylglycine-mncl2 aqueous solutions at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) k(2009) Santosh, M.S.; Bhat, D.K.; Bhat, A.S.The viscosities, ultrasonic velocities, densities, and refractive indices of glycylglycine and MnCl2in water have been studied at different temperatures and concentrations. Excess thermodynamic parameters such as adiabatic compressibility (?ad), apparent molar volume (?V), apparent molar compressibility (?K),intermolecular free length (Lf), specific acoustic impedance (Z), relative association (RA), and salvation number (Sn) have been calculated. The variations in apparent molar volume were confirmed by Scaled particle theory, and the changes in apparent molar compressibilities were interpreted using the Kirkwood model. The variations in apparent molar volumes were fitted with Masson's equation. The viscosity data have been fitted using the Jones-Dole empirical equation. The molecular relaxation of MnCl2and glycylglycine in water gives an idea about solute-solute interactions. The interactions also suggest the formation of H-bonding in the system. The tructure forming tendency of the solute has also been indicated by the solvation number. Copyright& copy; 2009 American Chemical Society.Item Ultrasonic velocities, densities, and viscosities of glycylglycine and CoCl2 in aqueous and aqueous ethanol systems at different temperatures(2010) Santosh, M.S.; Bhat, D.K.; Bhatt, A.S.Ultrasonic velocity (u), density (?), and viscosity (?) have been measured for glycylglycine and CoCl2 in aqueous and aqueous ethanol systems at T = (288.15 to 318.15) K. Using the experimental values, the adiabatic compressibility (?s), molar hydration number (nH), apparent molar compressibility (KS?), apparent molar volume (V?), limiting apparent molar compressibility (KS ?{symbol}0), limiting apparent molar volume (V?{symbol}0), their constants (SK, SV), viscosity coefficients of A and B parameters of Jones-Dole equation, relative viscosity (?r), and excess Gibbs free energy of activation (? G* E) were calculated and the results of all these parameters have been discussed in terms of solute-solvent and solute-solute interactions. © 2010 Elsevier Ltd. All rights reserved.Item Volumetric, refractometric, and excess properties of glycylglycine in aqueous FeCl2 solution at temperatures T = (288.15 to 318.15) K(2010) Santosh, M.S.; Bhat, D.K.; Bhatt, A.S.Densities and refractive indices have been measured for glycylglycine in aqueous FeCl2 solution as a function of concentration at T = (288.15 to 318.15) K. The apparent molar volumes and partial molar volumes were obtained from these density data. The limited partial molar expansivities have been calculated from the temperature dependence of the partial molar volume. The molar refractions were calculated from the experimental refractive index values for the studied mixture. The excess volumes and molar refractions were also calculated. The results are discussed in terms of molecular interactions. © 2010 American Chemical Society.Item Excess molar volumes, viscosity deviations and isentropic compressibility changes in glycylglycine-NiCl2 aqueous ethanol mixtures(2010) Santosh, M.S.; Bhat, D.K.The densities, viscosities and ultrasonic velocities for glycylglycine-NiCl2 in aqueous ethanol mixtures have been studied in the temperature range 288.15-318.15K. The excess molar volumes, viscosity deviations and changes in isentropic compressibility for the binary mixtures have been calculated and discussed in terms of hydrogen bonding and structure-breaking effect. The computed results are fitted to the Redlich-Kister polynomial. The results clearly indicate that there is a strong association in the mixtures studied. © 2010 Elsevier B.V.Item Molar volume, compressibility and excess properties of glycylglycine in aqueous NiCl2 solutions(2010) Santosh, M.S.; Bhat, D.K.Volumetric and acoustical parameters are reported for glycylglycine in aqueous NiCl2 solution at T=(288.15-318.15)K. The apparent molar volumes and isentropic compressibilities were calculated from the experimental data of ultrasonic velocity and density. Together with these, excess isentropic compressibility (?SE), excess free volume (VfE), excess intermolecular free length (LfE) and deviations of ultrasonic velocity (?u) were obtained. The results are interpreted in terms of molecular interactions. The results show that the cation and anion play a significant role in influencing the behavior of glycylglycine in aqueous solutions. These effects were also attributed to the doubly charged behavior of glycylglycine and to the formation of physically bonded ion-pairs between charged groups of glycylglycine and cation and anion of the electrolyte. © 2010 Elsevier B.V.Item Application of Prigogine-Flory-Patterson theory to volumetric, ultrasonic, and compressibility parameters of (glycylglycine + CuCl2) in aqueous ethanol mixtures(2011) Santosh, M.S.; Bhat, D.K.The molar volume and compressibility of (glycylglycine + CuCl2) in aqueous ethanol mixtures have been obtained at four different temperatures T = (288.15 to 318.15) K from ultrasonic velocity and density measurements. Excess molar volumes were found to be negative throughout the composition range indicating notable changes in hydrogen bonding and electrostatic interactions. Using the Prigogine-Flory-Patterson theory, quantitative estimation of different contributions, i.e. interactional, free volume, and P effect to VE have been obtained. The molar isentropic compressibility has been computed using the ultrasonic velocity and excess volume data. The trends in ?SE are affected by the size of the molecule leading to negative contributions. In order to compare the theoretical values of ultrasonic velocity, the equations of Nomoto and Junjie were used and found to predict the experimental data very well. © 2011 Elsevier Ltd. All rights reserved.Item Volumetric, acoustic, and refractometric study of cyclic alanylalanine in aqueous cobalt chloride solutions at temperatures T = (293.15 to 313.15) K(2013) Karanth, V.R.; Bhat, D.K.Density, refractive index, and speed of sound values of cyclic alanylalanine + aqueous CoCl2 systems have been reported as a function of concentrations of cyclic alanylalanine and that of CoCl2 at temperatures T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. The values of partial molar volumes, isentropic compressibilities, and partial molar isentropic compressibilities of the cyclic alanylalanine + aqueous CoCl 2 systems have been calculated from the speed of sound and density data obtained from the experiment at various temperatures. The decreasing value of isentropic compressibility with respect to the molal concentration of cyclic alanylalanine and temperature indicated the presence of strong solute-solvent interaction operative in the present system. The variations in partial molar volumes as well as partial molar isentropic compressibilities have been discussed in terms of ionic, hydrophilic, and hydrophobic interactions present in the system. © 2013 American Chemical Society.Item Partial molar volume and partial molar isentropic compressibility study of glycine betaine in aqueous and aqueous KCl or MgCl2 solutions at temperatures T = 288.15-318.15 K(2013) Karanth, V.R.; Bhat, D.K.Partial molar volume, ?v0, isentropic compressibility, ?s, and partial molar isentropic compressibility, ?k0 of glycine betaine in aqueous and aqueous KCl or MgCl2 solutions have been computed using the experimental density and speed of sound data at temperatures, T = 288.15-318.15 K. The transfer partial molar volumes, ?tr?v0, and transfer partial molar isentropic compressibilities, ?tr?k0, have also been evaluated using the experimental data. The partial molar volumes of glycine betaine were computed using the usual equation as well as the equation employed by Pitkänen et al. So obtained values have been compared with literature values. The variations in experimental and computed parameters have been discussed in terms of solute-solvent and solute-solute interactions. © 2013 Elsevier B.V. All rights reserved.Item Optical and mechanical properties of calcium phosphate glasses(Maik Nauka Publishing / Springer SBM compmg@maik.ru, 2014) Venkateswara Rao, G.V.; Shashikala, H.D.Binary calcium phosphate glasses in the system, xCaO-(100 - x) P 2O5 with x = 30, 35, 40, 45, and 50 mol % were prepared by conventional melt quenching technique. The density, molar volume and refractive index of the glasses were found to increase with the increase in CaO content. Structural investigation by FTIR spectroscopy revealed that the substitution of P2O5 by CaO depolymerizes the phosphate glass network by systematic conversion of Q3 structural units to Q2 structural units by breaking the P-O-P links. From the optical absorption studies, the optical band gap values were found to decrease with increasing CaO content which can be due to increase in the concentration of non-bridging oxygens in the glass network. Vickers hardness increased with the calcium oxide content due to densification. The fracture toughness decreases with the increase in CaO content due to the increase in the bond density between the modifying cations and the non-bridging oxygens in the glass network. It was observed that brittleness increases with the addition of CaO content which can be mainly attributed to the decrease in the molar volume. © 2014 Pleiades Publishing, Ltd.Item Partial molar volumes and compressibilities of glycine betaine in aqueous NaCl solutions at temperatures T=(288.15-318.15)K(Elsevier, 2014) Karanth, V.R.; Bhat, D.The partial molar volumes, partial molar isentropic compressibilities, transfer molar volumes and transfer molar isentropic compressibilities of the system: glycine betaine in aqueous (0.1, 0.2, 0.3, 0.4 and 0.5molkg-1) NaCl solutions at different temperatures were determined using the experimental values of density and speed of sound. The positive transfer molar volumes of the systems indicated the presence of strong solute-solvent interactions. The electrostatic charge-charge interactions (among Na+/Cl- ions and amino/carboxylic groups of glycine betaine) were found to be predominant over the ionic-hydrophobic interactions (among Na+/Cl- ions and CH2/CH3 groups of the glycine betaine) in aqueous solutions. Size of the metal ion was found to influence the volumetric properties to an appreciable extent. © 2014 Elsevier B.V.