R. Palepu

Thermodynamic properties of binary mixtures of butanediols with water

Ultrasonic velocities and densities at five different temperatures over the entire composition range for aqueous solutions of 1,2, 1,3, 1,4, and 2,3 butanediols were measured. Excess volumes and adiabatic compressibilities were calculated using the experimental data. Apparent and partial molar volumes and compressibilities were analyzed to evaluate the departure from ideal solution behavior. From the analysis of the results, the interactions of isomeric butanediols with water are discussed in terms of the placements of hydroxyl groups in the isomeric butanediol molecules.

Partial molar and excess volumes and adiabatic compressibilities of binary mixtures of ethanolamines with water

Speed of sound and densities of solutions of mixtures of seven ethanolamineswith water were measured over the full range of composition at 25, 35, and 45°C.Results of these measurements were used to calculate adiabatic compressibilities,excess volumes, partial molar and apparent molar volumes, and apparent molarcompressibilities. Knowledge of the above properties of these mixtures are abasis for understanding some of the molecular interactions in these systems. Fromthe analysis of the results, the type of interactions between the ethanolaminesand water are discussed in terms of the number and size of the alkyl groupsattached to the nitrogen atom of ethanolamine.

Viscosity, Surface Tension, and Refractive Index Measurements of Mixtures of Isomeric Butanediols with Water

Solution properties of aqueous mixtures of isomeric butanediols have been investigated employing viscosity, surface tension, and index of refraction measurements as functions of temperature. The deviation of viscosity, surface tension, and molar refraction from ideal solution behavior is evaluated from the experimental data. The deviation from ideality is discussed in terms of molecular interactions between the components. Surface activity of the diols is evident from the surface tension measurements. It is found that the degree of hydrophobicity of the diols varies in the order 1,2 > 2,3 > 1,3 > 1,4. The strength of interaction of diols with the water varies in the order 2,3 > 1,4 ≃ 1,3 > 1,2.

Thermodynamic transfer functions at infinite dilution and clathrate formation of ethanolamines in water

The ultrasonic velocities and densities of solutions of water in various binary aqueous solutions of ethanolamines were measured over the full range of compositions at 298, 308 and 318 K. The experimental data in the dilute region with mole fraction of water <0.1 was analyzed to determine the partial molar volume and adiabatic compressibilities at infinite dilution. Compressibility isotherms intersect approximately at a common point for triethanolamine (TEA), methyldiethanolamine (MDEA), dimethylethanolamine (DMEA) and diethylethanolamine (DEEA) and this is attributed to the formation of quasi-clathrate-like structures in the liquid solutions. The standard thermodynamic transfer functions were calculated to evaluate the environment of water at infinite dilution in these systems. The transfer functions of water between the various ethanolamines are considerably larger for ethanolamines that differ in their degree of hydrophobicity.

A thermodynamic and photophysical study of the effects of thiourea on the micellar properties of aqueous sodium dodecyl sulphate solution

The micellar properties of sodium dodecyl sulphate (SDS) in aqueous thiourea solutions were investigated with the aim of studying the effect of thiourea on these properties. The critical micelle concentrations (cmc) and the degree of dissociation of the micelle were determined by the conductometric method over the temperature range 298–323 K for different concentrations of thiourea. The cmc values of the surfactant in the presence of thiourea were obtained by following the change in the relative intensities of vibrational fine structure of the pyrene fluorescence spectra. The aggregation numbers were determined by employing the static quenching fluorescence method. The cmc values in the presence of varying electrolyte concentrations (NaCl) were obtained with 8-anilinonaphthalene 1-sulphonate (ANS) as a fluorescence probe, and from these values the degree of dissociation was calculated. The mass action model was applied in the present study to obtain various thermodynamic parameters of micellization. All these properties were compared with the micellar properties of an aqueous urea/SDS system, and it was found that thiourea is a better demicellization agent.

Spectroscopic investigations on the interaction of an anionic probe with nonionic micelles of Igepal surfactants in aqueous media

The behaviour of the anionic dye 8-anilino-1-napthalenesulfonic acid ammonium salt, or ANS, in aqueous solutions containing the Igepal series of polyoxyethylene nonionic surfactants was investigated using fluorescence spectroscopic technique. The interactions of the dye with the nonionic surfactants were examined in micellar media, to prevent dye aggregate formation and to ensure maximum dye and surfactant interaction. From the relative fluorescence enhancements, binding constants of the dye to the surfactant micelles and aggregation numbers of the micelles were determined. The aggregation numbers were also separately determined by static fluorescence quenching of pyrene by cetylpyridinium chloride in aqueous surfactant mixtures at a fixed concentration of surfactant, and compared with the value obtained from the present investigation of the interaction of the micelles with the ANS probe. The values of binding constants, micropolarity values sensed by pyrene and the Stern–Volmer constants for quenching of pyrene fluorescence by cetylpyridinium chloride were correlated with the number of ethylene oxide groups in the Igepal series.

Micellar properties of N-octylammonium bromide in binary aqueous mixtures of butoxyethanol system

Abstract Micellar and thermodynamic properties of n-Octylammonium bromide in binary aqueous mixtures of butoxyethanol were determined employing conductivity, viscosity, ultrasonic velocity and potentiometric techniques at several temperatures. the variation of critical micellar concentration with temperature and solution composition was investigated. Thermodynamic functions such as Gibbs free energy of micellisation and transfer were evaluated Micellar aggregation numbers of the surfactant in these binary mixtures were determined employing Guth-Simhas relationship, assuming micellar sphericity and neglecting electroviscous effect.