Partial Molar Expansibilities Research Articles

Thermophysical studies of protonated and deprotonated glycine in aqueous sodium acetate buffer solutions at different temperatures

Interactions of glycine in water and in (0.10, 0.50 and 1.00) aqueous sodium acetate buffer solutions of pH (1.00 and 12.40) have been investigated at different temperatures, T/K = (298.15-318.15). Densities, and viscosities, of glycine in water and in aqueous sodium acetate buffer solutions have been measured. The obtained density data have been used to calculate apparent molar volume, , limiting partial molar volume, , limiting partial molar volumes of transfer, . Viscosity B-coefficient, viscosity B-coefficient of transfer, , Activation free energies per mole of the solute, and solvent, have been calculated from viscosity data. Further, second order derivative of partial molar expansion coefficient and dependence of coefficients on temperature is useful in measuring the structure making and breaking behavior of solute in these systems. Pair and triplet interaction coefficients for both the properties were also calculated. Thus, the results obtained from volumetric and viscometric studies are of considerable importance to identify different type of interactions (i.e. H-bonding, van der Waal’s interactions)in these systems.

Studies on molecular interactions of l-histidine/l-serine in aqueous diphenhydramine hydrochloride solutions at various temperatures: Volumetric, ultrasonic and viscometric approach

Thermophysical properties for varying concentrations of essential (L-histidine) and non-essential (L-serine) amino acids in water and (0.05–0.15) mol kg−1 mixed aqueous diphenhydramine hydrochloride solvent system has been deliberated at different temperatures ranging (293.15−318.15) K and ambient pressure (101.3 kPa). The experimentally obtained data has been utilized to compute different volumetric, compressibility and rheological parameters such as apparent molar volume (Vϕ), partial molar volume (V0ф), partial molar expansibility (E0ϕ), apparent molar isentropic compression (Kϕ,s), partial molar isentropic compression (K0ϕ,s), hydration number (nH), transfer parameters, viscosity coefficients etc. The structure breaking ability of the solute molecules has been comprehended using Hepler′s constant (temperature derivative of partial molar expansibility at constant pressure) and dB/dT (temperature derivative of viscosity B-coefficient) values. Further, by using the co-sphere overlap model various sorts of solute-drug interactions prevailing in the systems have been discussed.

Effect of ethylene glycol/diethylene glycol/triethylene glycol on the thermodynamics of the aqueous biotin solutions at various temperatures

Acoustic and volumetric parameters for the liquid mixture (water + Biotin + ethylene glycol/diethylene glycol/triethylene glycol) are evaluated at different temperatures (288.15 K, 298.15 K, 308.15 K, and 318.15 K) and constant pressure of 0.1 MPa over the range of biotin concentrations (0.0000, 0.0015, 0.0025, and 0.0035) mol·Kg-1. The experimental work was carried out by Anton Paar DSA 5000 M, where the density (ρ) and the speed of sound (c) are measured, which are later used to determine the various derived thermodynamic properties, such as, apparent molar properties (apparent molar volume, Vϕ; apparent molar isentropic compression,Kϕ,S), the partial molar properties (partial molar volume, Vϕ0; partial molar isentropic compression, Kϕ,S0), the partial molar transfer properties (partial molar volume of transfer, ΔVϕ0; partial molar isentropic compression of transfer, ΔKϕ,S0) and the partial molar expansibility (Eϕ0) along with its first derivative ∂Eϕ0/∂TP. The obtained results are explained in terms of the kind of intermolecular interactions developed in the mixture using the co-sphere overlap model. Further, with the partial molar properties, the pair and triplet interaction coefficients (VAB,KAB; VABB, KABB) are calculated.

Molecular interactions of two biologically active molecules (L–serine and L-valine) in aqueous [Hmim]Cl solutions: Volumetric and viscometric approach

Mixtures of amino acids L–serine and L–valine + (0.05, 0.1, 0.2 and 0.3 mol·kg−1) aqueous solutions of ionic liquid 1-n-hexyl-3-methylimidazolium chloride, [Hmim]Cl, at temperatures T = (293.15, 298.15, 303.15, 308.15 and 313.15 and 318.15 K) have been studied using density and viscosity measurements. From density, the volumetric properties: the apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and expansibility, Eϕ0, standard molar volume of transfer, ΔVϕ0, and hydration number, nH, were calculated. Similarly, from viscosity measurements and using the Jones–Dole equation and transition state treatment, the viscosity B coefficient and some activation parameters of viscous flow were calculated. These parameters, their variation with temperature and concentration, were discussed in terms of transition state theory. Based on the co-sphere overlap model, the solute–solute and solute–solvent interactions were discussed, including amino acids hydration, and structural effects. The structure making/breaking ability of the amino acids in solutions was also discussed using Hepler's constant and (dB/dT) variation.

Investigations on volumetric, compressibility and viscometric properties of L-ascorbic acid and thiamine hydrochloride in aqueous 1-ethyl-3-methylimidazolium hydrogen sulfate solutions at different temperatures

A comprehensive study on volumetric, compressibility, and viscometric properties of two vitamins namely L-ascorbic acid and thiamine hydrochloride in aqueous and (0.05, 0.10, and 0.15 mol kg−1) binary aqueous 1-ethyl-3-methylimidazolium hydrogen sulfate media has been done. The physical properties like density, speed of sound, and viscosity have been estimated at six discrete temperatures (293.15–318.15) K and ambient pressure (0.1 MPa). The thermophysical parameters like apparent molar volume (Vϕ), partial molar volume (Voϕ), partial molar expansivity (Eϕo), Hepler’s constant ∂Eϕo∂TP, apparent molar isentropic compressibility (Kϕ,s), partial molar isentropic compressibility (Kϕ,so), acoustic and volumetric interaction coefficients (KAB, KABB, VAB, VABB), Jones-dole coefficients (A and B) etc are deliberated. Cosphere overlap model was employed for the understanding of various types of molecular interactions that are established in the studied systems. Also, the structure breaking ability of both vitamins have been examined through the positive sign of dBdT values and negative sign of ∂Eϕo∂TP values. Moreover, this study provides the crucial data imperative for the designing of several industrial processes.

Temperature-dependent thermodynamic and physicochemical studies of glycols in aqueous biotin solutions

The current study deals with the analysis of the molecular interactions among the glycols (propylene glycol, PG and hexylene glycol, HG) molecules in (0.000, 0.001, 0.002 and 0.003) mol·Kg-1 aqueous solutions of biotin at constant experimental pressure 0.1 MPa and temperature range (288.15 K, 298.15 K, 308.15 K and 318.15 K). The speed of sound and the density for the liquid mixtures is measured with Anton Paar DSA 5000 M. Numerous thermodynamic and acoustic parameters are determined using these experimental data. The apparent molar volume (Vϕ), partial molar volume (Vϕ0), partial molar volume of transfer (ΔVϕ0), apparent molar isentropic compression (Kϕ,S), partial molar isentropic compression (Kϕ,S0), partial molar isentropic compression of transfer (ΔKϕ,S0) were estimated using the experimentally obtained density and speed of sound respectively along with the partial molar expansibility(Eϕ0), its first-order derivative ∂Eϕ0/∂TP and pair-triplet interaction coefficients (VAB,KAB,VABB; KABB). The apparent molar properties recommend the existence of strong (solute and solvent) interactions in the ternary mixture which is also justified by the positive partial molar expansibility values, while the partial molar properties suggest the formation of the hydrogen bond in the mixture. With Passynski's equation the hydration number (nh) for PG/HG in aqueous solutions of biotin is calculated utilizing the compressibility data and the obtained results are explained in terms of combined hydration effects and hydrophobic effect.

Elucidation of molecular interactions between amino acid and imidazolium based ionic liquid in an aqueous system: Volumetric and acoustic studies

Some of the most active academic and scientific research faces of the past decade are on ionic liquids and their behavior for industrial purposes. In the present work, the densities and sound velocities of an amino acid (glycine) in pharmaceutically active ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIm][PF6] solutions were measured at different temperatures ranging from 293.15 K to 318.15 K under atmospheric pressure. The experimental data has been further used to calculate volumetric and acoustic parameters such as apparent molar volumes, VΦ and apparent molar isentropic compression, KΦ partial molar expansion, EΦ0 partial molar volume, VΦ0 and partial molar isentropic compression KΦ0 and corresponding empirical constants, Sv and Sk. The negative values are obtained for partial molar volume of transfer, ΔtVΦo at all temperatures and become more negative by increasing the concentration of the ionic liquid. The positive values of partial molar expansibilities, EΦo are decreasing with an increase in temperature predict increasing electrostriction. The obtained values of expansibilities show the structure-making/breaking ability of glycine in investigated solutions.

Molecular interaction studies of antidepressant drug with aqueous caffeine using volumetric and acoustic methods

Knowledge of drug interactions and the factors controlling these interactions could be useful to overcome their adverse effects on human health. In this study, the effect of caffeine on the antidepressant action of escitalopram oxalate was investigated to explore the behavior of escitalopram oxalate in the presence of caffeine in terms of molecular interactions in an aqueous system at temperature range 293.15 to 313.15 K and atmospheric pressure. Density (ρ) and ultrasonic velocity (u) of escitalopram oxalate in different concentrations of caffeine solutions were measured at the selected range of temperatures. Experimental data has been used to calculate apparent molar volume (Φv) and apparent molar isentropic compressibility (Φv) and fitted to the Redlich–Mayer equation to obtain limiting parameters. Negative deviations from Debye–Huckel limiting law of apparent molar volume for the drug in the presence of caffeine were observed which can be used as a direct measure of the ion-ion and ion–solvent interactions. Partial molar volumes of transfer (ΔtΦvο) were found to be negative for the studied mixture. The partial molar expansibilities and Hepler's constant (∂2∅V0/∂T2) were found to be positive for the mixture (escitalopram oxalate+ caffeine) in water. Intermolecular free length (Lf) and compressibility hydration number (nH) were also analyzed. Obtained results were explored in terms of molecular interactions prevailing among escitalopram oxalate and caffeine molecules in aqueous solutions.

Gatifloxacin–Ionic Surfactant Interactions: Volumetric, Acoustic, Voltammetric, and Spectroscopic Studies

AbstractSurfactant systems have been frequently used as pseudomodels for investigating interactions of drugs with biological membranes because of their structural similarities with the latter. This helps to understand complicated yet very important biological processes like diffusion of bioactive moieties through biomembranes. The current study deals with voltammetric and spectroscopic studies to evaluate the interaction of a potential antibacterial drug, gatifloxacin (GTF), with a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS), under physiological conditions (phosphate buffer, pH 7.4). For more detailed insight into the GTF–ionic surfactant interactions, density and acoustic data were also recorded and used to calculate several important parameters, namely, apparent molar volume (ɸV), isentropic compressibility (Ks), and apparent molar isentropic compressibility (ɸK) at T = 298.15, 303.15, 308.15, and 313.15 K. Values for partial molar volume (, partial molar expansivity , specific acoustic impedance (Z), relative association (RA), intermolecular free length (Lf), and sound velocity number (U) were also obtained. The interpretation of the concentration dependence of the above‐mentioned quantities using a cosphere overlap model led to a better apprehension of solute–solute and solute–solvent intermolecular interactions present in the investigated system, whereas cyclic voltammetry and ultra violet (UV)–visible spectroscopic studies assisted in predicting the location of adsorbed GTF molecules within the DTAB and SDS micelles.

Volumetric and aggregation properties of metformin hydrochloride in methanol in temperature range of (288.15–318.15) K

This manuscript is related to the study of volumetric and micellar properties of metformin hydrochloride (Met-HCl) in methanol in temperature range of (288.15–318.15) K. Conductometric and refractive index data was used to find CMC of drug. From conductometric data various thermodynamic variables were calculated which include free energy of micellization, entropy of micellization and enthalpy of micellization. Density measurements of different drug solutions at specified temperatures were utilized for the calculation of apparent molar volume, partial molar volume, Hepler's constant and partial molar expansivity. These parameters are important for getting an understanding about different types of interaction of drug in solution. Met-HCl showed strong solvophobic than electrostatic interaction with methanol and had a structure promoting effect on it which was apparent from positive value of partial molar volume, Hepler's constant and partial molar expansivity. Micellization process was spontaneous, endothermic and resulted in increase in entropy of system because Gibbs energy change was negative, enthalpy change and entropy changes were positive.

Molecular interactions studies of doxycycline hyclate in water, aqueous L-phenylalanine and glycyl glycine at different temperatures by using volumetric, ultrasonic and viscometric parameters

The density, sound velocity and viscosity of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine have been determined at different temperatures (305.15, 310.15, 315.15 and 320.15) K. The calculated values of partial molar volume (V_ϕ^o), standard partial molar volume of transfer (〖Δ_tr V〗_ϕ^o), partial molar adiabatic compressibility (κ_(ϕ,s)^o) and partial molar adiabatic compressibility of transfer (〖Δ_tr κ〗_(ϕ,s)^o) for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine infer the dominance of ion-hydrophilic interactions over hydrophobic-hydrophobic interactions. The Jones-Dole viscosity B-coefficient, viscosity B-coefficient of transfer (ΔtrB), free energy of activation of viscous flow per mole of pure solvent (〖Δμ〗_1^(o*)) and solute (〖Δμ〗_2^(o*) ), respectively, activation entropy (〖ΔS〗_2^(o*)) and activation enthalpy (〖ΔH〗_2^(o*)) of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been calculated using viscosity data. The structure making and breaking behaviour of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine are obtained from the values of Hepler’s constant i.e.((δ^2 V_ϕ^o)/(δT^2 )) and (dB/dT). The presence and absence of caging effect has been studied with the help of partial molar adiabatic expansibility (E_ϕ^o). The isobaric thermal expansion coefficient (α^o= (E_ϕ^o)/(V_ϕ^o )), intermolecular free length and acoustic impedance for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been determined.

Volumetric and transport properties of ternary solutions of l-serine and l-valine in aqueous NaCl solutions in the temperature range (293.15–323.15) K

In this paper we report new density and viscosity data of l-serine and l-valine in aqueous NaCl solutions as a function of amino acids molality at fixed salt concentration (0.1, 0.2, 0.5, 0.7 and 1.0 mol·kg−1) and temperature T = (293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K at atmospheric pressure of p = 0.1 MPa. From density, some derived properties such as the apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and expansibility, Eϕ0, standard molar volume of transfer, ΔVϕ0, and hydration number, nH, were calculated and discussed in terms of solute–solvent interactions and structural effects. The Jones–Dole equation and transition state treatment were used to obtain the viscosity B coefficient, free energy of activation of viscous flow per mole of solvent, Δμ10#, and per mole of solute, Δμ20#, entropies, ΔS20#, and enthalpies, ΔH20#, of activation of viscous flow for amino acids. All the activation parameters were discussed in terms of transition state theory. The co-sphere overlap model was used to interpret the results. The structure making/breaking ability of the amino acids in solutions was also discussed.

Volumetric, acoustic, electrochemical and spectroscopic investigation of norfloxacin–ionic surfactant interactions

Rising levels of bacterial resistance to antibiotics is a persistent and dynamic concern in the field of medicine and demand design and discovery of new and more effective antibiotics. One of the major hurdles in designing new antibiotics which should be capable of passively diffusing across biological membranes is the scarcity of knowledge regarding their biophysical interaction with these membranes. Surfactant systems have been frequently reported in the past decade as potential pseudo-membrane models to understand biophysical interactions of drugs with biological membranes at the molecular level. The present work is aimed at understanding the interaction of norfloxacin (NRF), a fluoroquinolone drug, with dodecyltrimethylammonium bromide (DTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant) at molecular level. Volumetric and acoustic studies of DTAB and SDS in buffered solutions of NRF at physiological pH (7.4) and a temperature range of 298.15 to 313.15 K were performed to calculate apparent molar volume (ɸV), isentropic compressibility (Ks), apparent molar isentropic compressibility (ɸK), partial molar volume (ɸVo), partial molar expansibility (ɸEo), specific acoustic impedance (Z), relative association (RA), intermolecular free length (Lf) and sound velocity number (U). The variation in these quantities as a function of surfactant concentration is interpreted in terms of NRF-ionic surfactant interaction using a cosphere overlap model. Cyclic voltammetry and UV–visible spectroscopy were used to calculate the partition coefficient (Kc) and binding constant (Kb) of NRF with ionic micelles. Free energies calculated from corresponding Kc and Kb values revealed the spontaneity of partitioning and binding of NRF with ionic micelles.

Use of Masson's and Jones–Dole equations to study different types of interactions of three pharmacologically important drugs in ethanol

AbstractThe volumetric and viscometric study of three allopathic drugs (sodium valporate, benzalkonium chloride, and losartan potassium) in ethanol solvent is reported here. This study was carried out at four different temperatures that is, from 288.15 to 318.15 K. The accurately measured density values were used to calculate partial molar volume at infinite dilution, solute–solute interaction parameter, Hepler's constant, partial molar expansivity constant, and isobaric thermal expansion coefficient. The viscosity measurements were carried out for the calculation of constants of Jones–Dole equation and to calculate different thermodynamic parameters of viscous flow which include standard free energy change, standard enthalpy change, and standard entropy change of viscous flow. All these viscometric and volumetric parameters are useful for understanding the different types of interactions of drugs in solution and to study the drug action in body. The results of both volumetric and viscometric studies showed that all drugs had structure promoting effect on solvent, existing of strong solute–solvent interaction, and very weak solute–solute interaction. For all these drugs, solvophobic interaction was found to be dominant over electrostriction. Viscometric studies also showed the existing of stronger solute–solvent interaction in ground state as compared to that in transition state.

Insight into solute-solute and solute-solvent interactions of semicarbazide hydrochloride in water and d-glucose/d-sucrose + water solutions at temperatures (293.15 to 318.15) K

The solute-solute and solute-solvent interactions of drug semicarbazide hydrochloride with carbohydrates (d-glucose/d-sucrose) are investigated by using volumetric, viscometric and acoustic properties. The measurements of the densities ρ, ultrasonic speeds u, and viscosities η. of semicarbazide hydrochloride in 5% and 10% d-glucose/d-sucrose + water (w/w) solutions were carried out at temperatures (293.15–318.15) K and at pressure, p = 101 kPa. The apparent molar volumes, Vϕ, limiting apparent molar volumes,Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks,ϕ°, partial molar expansibilities, Eϕ°, transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr° have been calculated from the experimental data. The viscosity data were examined by using the Jones-Dole equation and the viscosity A and B coefficients were evaluated. The results are discussed in terms of solute-solute and solute-solvent interactions in these solutions. The structure making/breaking ability of semicarbazide hydrochloride is examined using the sign of temperature derivative of B-coefficient, dB/dT.

Insight into intermolecular interactions and hydration properties of biologically active amino acids in aqueous solutions of cefepime: volumetric, compressibility and viscometric studies

The measurement of density, speed of sound and viscosity of an amino acid and its dipeptide i.e., glycine and glycylglycine in aqueous solution of antibiotic drug cefepime has been carried out at various temperatures. The density and speed of sound data has been used to obtain partial molar volume partial molar expansion coefficient second derivative hydration number (), isentropic compressibility partial molar isentropic compressibility partial molar volume of transfer and partial molar isentropic compressibility of transfer The viscosity data have been used to calculate the viscosity B–coefficients, its temperature derivative dB/dT, viscosity B–coefficient of transfer () and various thermodynamic parameters of activation of viscous flow i.e., and for amino acid/peptide in cefepime solutions. The dependence of these parameters upon concentration and temperature clearly suggests the role of amino acid/peptide and cefepime in solute-solvent interactions. The obtained results have been explained on the basis of competing pattern of interactions between the co-solute and solute in the studied ternary system in order to deduce important information regarding drug-amino acid/peptide interactions.

Density measurements of water – N-methylacetamide mixture at temperatures from 274.15 to 333.15 K and ambient pressure. A comparison of the volumetric characteristics of some amides

The densities ρ of the binary mixture of N-methylacetamide with water have been measured in the entire composition range of the mixture liquid state at T = (278.15, 288.15, 298.15, 308.15, 323.15 and 333.15) K at atmospheric pressure (0.1 MPa). The densities were also measured for dilute aqueous solutions of N-methylacetamide (from 0.00455 to 0.05743 mol fractions) at a temperature from 274.15 to 283.15 K, with an increment of 1 K at atmospheric pressure, in order to study the effect of N-methylacetamide on the temperature of the maximum water density. These data were later used to calculate the excess molar volumes .VmE., partial molar volumes of water V1 and N-methylacetamide V2, and to obtain the limiting partial molar volumes Vi∞ and limiting partial molar isobaric expansion of N-methylacetamide EP,2∞. The following volumetric characteristics were then obtained from these values: the shift temperature of the maximum density, Hepler’s constant, the pressure derivative of the second virial coefficient, relative volumetric parameter of hydration. The obtained parameters show the effect of N-methylacetamide on water. The study also included a comparison of these volumetric characteristics for several aqueous solutions of amides: acetamide, urea and N-methylurea. The paper also presents a comparison of these parameters at the changes in the structure of amide molecules.

Volumetric and ultrasonic study of l-arginine/l-histidine and gentamicin sulphate in aqueous medium at different temperatures

The nature of interaction of amino acid with drug are examined from the experimentally measured values of densities, ρ and ultrasonic speeds, u of l-arginine and l-histidine in aqueous-gentamicin sulphate (1% and 2% gentamicin sulphate in water, w/w) solvents over the temperature range from 293.15 K to 318.15 K and at atmospheric pressure. From the experimental ρ values, the apparent molar volume, Vϕ, limiting apparent molar volume, Vϕ°, transfer volume, Vϕ, tr°, and limiting partial molar expansivity, Eϕ° were obtained. Using the u data, acoustic parameters, viz., apparent molar compressibility, Ks, ϕ, limiting apparent molar compressibility, Ks, ϕ° and transfer compressibility, Ks, ϕ, tr° have been evaluated. The results have been interpreted in terms of possible solute-solute and solute-solvent interactions.

Drug-drug and drug-solvent interaction studies of Chloroquine phosphate, Acefylline piperazine and Gentamicin sulfate in polymeric systems

The densities of three pharmacologically significantly used drugs i.e., Chloroquine phosphate (CP), Acefylline piperazine (AP) and Gentamicin sulfate (GS) have been carried out in aqueous (aq), aqueous polyethylene glycol (aq-PEG) and aqueous polyvinyl pyrrolidone (aq-PVP) solvent systems within concentration range (0.02–0.1 ± 0.001 mol.dm−3) at different temperatures (293.15–318.15 K) with the interval of 5 K. Density data were used to evaluate volumetric properties of drugs (CP, AP and GS) by apparent molar volume, partial molar volumes, molar expansibilities and isothermal expansion coefficient. ϕE° provides information about the absence or presence of a caging or packing effect. Partial molar transfer volume was also calculated to study the hydrophilic/hydrophobic interactions in aq-PEG and aq-PVP solvent systems. The results are interpreted in terms of drug–solvent and drug-drug interactions and structure making or breaking abilities of drugs in aq, aq-PEG and aq-PVP solvent systems.

Volumetric Properties of Secondary Butanol and Tertiary Butanol in Water and Aqueous Micellar Systems of Sodium Dodecyl Sulphate

The apparent molal volumes of sec-butanol and t-butanol in water and in aqueous micellar system of sodium dodecyl sulphate have been determined from density measurements at different surfactant concentrations and temperatures. The partial molal volumes of the alcohols in aqueous micellar system at infinite dilution, V20 (mean, mic) were obtained from apparent molal volume data and compared with the corresponding values in aqueous solvent, V20 (mean, aq). The standard partial molal expansibilities, E20 (mean) of the alcohols were evaluated from V20 (mean) data at various temperatures. The transfer apparent molal volumes, ∆φtr0 for the alcohols from water to surfactant-water system are determined from apparent molal volume data. The sign and magnitude of these parameters are used to analyze the location of the solubilizate (alcohols) in the micellar system and the nature of interactions between alcohols and the micellar aggregates.