Parameters Of Viscous Flow Research Articles

Polythermal studies of the water – propylene glycol systems by densitometry, viscometry and spin probes method

Based on the determined values of density, dynamic viscosity and molar volumes, the thermodynamic activation parameters and excess thermodynamic activation parameters of viscous flow at temperatures from 293.15 K (20°C) to 313.15 K (40°C) were calculated for the mixed binary solvents water – propylene glycol (PG). Using the isotherms at 298.15 K, assumptions were made about the composition regions of binary solvents with different structural organizations. The structure of the mixed solvent has an impact on the various functional characteristics of the systems water – PG, and it could also influence the performance of medicinal products with a liquid dispersion medium. The density and excess density, as well as the dynamic viscosity and excess dynamic viscosity for systems water – PG were determined as a function of the PG concentration. Using the method of spin probes, it was demonstrated that changes in the dynamic viscosity of systems water – PG correlated with the alterations in the viscosity of the microenvironment of spin probe molecules. The viscosity of the microenvironment was also influenced by the interaction between molecules of dissolved spin probes and solvent molecules.

Physicochemical investigations on molecular interactions of adenine with aqueous D-glucose/D-maltose solvent media at varying temperatures and compositions

Adenine derivatives are used in pharmaceuticals, and carbohydrates like D-maltose and D-glucose which are often used as excipients or stabilizers in drug formulations. Studying their interactions can help in optimizing drug formulations for stability and effectiveness. Further, understanding their interactions, provide insights into flavor development, food stability, and potential applications in food technology. In this regard, we have analysed the physicochemical properties of adenine in aqueous saccharide solvent media which can contribute to various fields, including biochemistry, pharmaceuticals, catalysis, and material science, with use for both basic research and practical applications. So, in this research work, physicochemical properties of adenine have been investigated in aqueous and mixed aqueous (0.05, 0.10 and 0.15) mol kg−1 D-glucose/D-maltose solvent media at discrete temperatures (293.15–313.15) K and experimental pressure (0.1 MPa). The experimentally determined physical properties such as density, velocity of sound, and viscosity have been utilized for the estimation of several parameters such as apparent molar volume (Vϕ), limiting apparent molar volume (V0ϕ), hydration number (nH), limiting apparent molar expansivity (E0ϕ), Hepler’s constant (∂E0ϕ/∂T)P, apparent molar isentropic compression (Kϕ,s), limiting apparent molar isentropic compression (K0ϕ,s), viscosity B-coefficients, transfer parameters and thermodynamic parameters of viscous flow (Δμ01, Δμ02, TΔS02 and ΔH02). Further, the Co-sphere overlap model has been employed for the analysis of varied probable interactions operating in the prepared systems. The obtained results signify that in all solution systems, the solute–solvent interactions are advancing with rising temperature and concentrations of saccharides. Also, the structure breaking tendency of adenine has been investigated via inference of Hepler’s constant data and positive values of dB/dT data for all the investigated systems. Moreover, the deduced apparent specific volume data evidently specify that adenine has sweet taste in water and different concentrations of chosen saccharides.

Solvation behavior of chitosan monomers in aqueous [Hmim]CL solutions. Experimental and DFT studies

This paper reports densities and viscosities for the mixtures of D-glucosamine hydrochloride (GlcN·HCl) and N-acetyl-D-glucosamine (GlcNAc) with aqueous solutions of 1-hexyl-3-methylimidazolium chloride, [Hmim]Cl, between 293.15 and 318.15 K in 5 K increments and atmospheric pressure. Leveraging this data, we calculated volumetric properties such as apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and standard molar volume of transfer, ΔVϕ0. We handled viscosity data to compute the viscosity B-coefficient and several activation parameters of viscous flow. Some of these are relevant in discussing interactions between monosaccharides (solute) and [Hmim]Cl (co-solvent) in aqueous media. The solute–solvent interactions were discussed based on ionic/ hydrophilic/ hydrophobic interactions using the co-sphere overlap model. ΔVϕ0 > 0 indicates that ionic/hydrophilic interactions predominate in the studied systems and are stronger in GlcN·HCl solutions than in GlcNAc at low [Hmim]Cl molalities. At higher [Hmim]Cl concentrations, decreasing values of ΔVϕ0 suggest the dominance of hydrophobic interactions over hydrophilic/ionic ones. We discuss (using Hepler’s constant and viscosity B-coefficient) the ability of monosaccharides to act as structure maker/breaker in aqueous [Hmim]Cl solutions. This indicates that GlcNAc is a better structure promoter than GlcN⋅HCl in aqueous [Hmim]Cl solutions. Finally, density functional theory (DFT) was used to model the molecular structure and compute the solute–solvent interaction energies using the GAMESS 2016 software.

Activation parameters of viscous flow of guar gum and its cross-linked system

The structure of a cross-linked form of a concentrated solution of guar gum was studied using IR spectroscopy. The processes of viscous flow of concentrated solutions of guar gum and its cross-linked system have been studied. It is shown that this system is a non-Newtonian fluid with a thixotropic type of viscous flow anomaly, which is also determined by the nature of the complexing agent. The influence of temperature on viscous flow processes, as well as the structure of aqueous systems of guar gum and its cross-linked form, were studied based on the average statistical sizes of kinetic units, which makes it possible to estimate the mobility of structural elements and their sizes for concentrated systems. The activation parameters of the viscous flow of aqueous systems of guar gum and its cross-linked system were studied. Calculations of thermodynamic parameters were carried out free energy, heat of activation of viscous flow, characterizing the strength of structures, and entropy of activation of viscous flow, characterizing the ordering of structures. At high shear stresses, for the guar gum solution system, the processes of ordering and orientation prevail during flow, and for the guar gum - pentaerythritol borate system, the processes of structure destruction and disordering prevail.

Thermodynamic characterization of aqueous solutions of NaCl, KCl, MgCl2 and CaCl2: volumetric, acoustic, viscometric and computational analysis

The volumetric and acoustic properties of alkali and alkaline earth metal salts are ubiquitous in numerous biological and non-biological processes and accurate formulation of their thermophysical properties is a fundamental prerequisite for complete exploration of their diverse applications. To meet this purpose, in this investigation, we herewith report the systematic data of densities ρ, speed of sound u and viscosity η of aqueous binary solutions of the prominent alkali and alkaline earth metal salts viz. NaCl, KCl, MgCl2, and CaCl2 at seven different temperatures T = (288.15–318.15 K) and ambient pressure over the wide concentration range of (0.002–1) mol∙kg−1.These experimental data have been further employed to obtain some important thermodynamic parameters, viz, the apparent molar volume of solute Vϕ, limiting apparent molar volume of solute Vϕ0, isentropic compressibility of solution κS, apparent molar isentropic compression of the solute KS,ϕ, limiting apparent molar isentropic compression of solute KS,ϕ0 and apparent molar expansibility Eϕ0. Further, the coefficient of thermal expansion α*, the second-order derivative of limiting apparent molar volume ∂2Vϕ0/∂T2, Jones-Dole equation viscosity A, B, D coefficients, temperature derivative of B coefficient i.e. dB/dT, activation parameters for viscous flow and hydration number nH have also been computed. The results obtained have been used to elucidate different interactions taking place in the aqueous electrolytic solutions. To corroborate the experimental results, quantum chemical calculations were performed using density functional theory (DFT) by Gaussian software package. The calculations included an analysis of molecular orbitals, with particular emphasis on the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Insights into the physicochemical properties of newly synthesized benzyl triethylammonium chloride-based deep eutectic solvents

In order to utilize deep eutectic solvents (DESs) as a replacement for conventional organic solvents for different applications, a detailed understanding of their physicochemical properties is extremely important. In this study, several novel DESs based on benzyl-triethylammonium chloride (BTEA) as a hydrogen bond acceptor (HBA) and acids/or alcohols as hydrogen bond donors (HBDs) have been synthesized. DESs have been thoroughly characterized and investigated for their physicochemical properties viz. thermal stability, glass transition temperature, viscosity (η), surface tension (γ), refractive index (nD), density (ρ), speed of sound (u), and conductivity (κ) in a temperature range of 293.15–343.15 K. The effect of temperature, type of HBDs, and alkyl chain length of HBDs of the DESs on the physicochemical properties are critically examined and discussed. Viscosity data are fitted to Vogel-Fulcher-Tamman (VFT) and Arrhenius models. A linear model was used to fit surface tension (γ), density, refractive index, and speed of sound data whereas conductivity data were fitted to a nonlinear equation. Primary data on physicochemical properties have been used to estimate the viscous flow parameters (activation entropy, activation enthalpy, and free energy of activation) and other derived parameters such as lattice energy, standard entropy, molar volume, intermolecular free length, and isentropic compressibility. A relationship between molar conductivity and dynamic viscosity has been established to evaluate the ionicity of the synthesized DESs. Insights into the structure–property correlations are discussed in detail.

Влияние неравномерности потока за корпусом модели одновального судна на гидродинамические и кавитационные характеристики отдельной лопасти в составе гребного винта

Object and purpose of research. This paper investigates wake non-uniformity effect of single-shafter model upon local and integral hydrodynamic and cavitation parameters of separate blade of its propeller. The study was performed on propeller models KP505 and containership models KCS. Materials and methods. Local and integral hydrodynamic parameters of propeller and container ship were obtained as per CFD methods. Viscous flow parameters are obtained through finite volume (FVM) solution of unsteady Reynolds equations (URANS) closed by biparametric semi-empirical turbulence model. Main results. The paper demonstrates that local and integral parameters of separate blade in “hull-propeller” system are considerably different from those determined in the uniform wake at the speeds obtained for the nominal wake field in behindhull conditions. Conclusion. Krylov State Research Centre experience of numerical calculations shows that 1) in many aspects of marine hydrodynamics numerical techniques are more informative than model tests and 2) in a number of cases, conventional propeller design approach based on the nominal wake field data (calculated or experimental) might lead to somewhat incorrect technical solutions.

Influence of physicochemical properties and structure of mixed solvents propylene glycol – macrogol 400 on their in vitro release

Aim. To study the density and dynamic viscosity of the mixed solvents propylene glycol (PG) – macrogol 400 (M400), to calculate their excess values and excess activation parameters of viscous flow, to evaluate the features of the structure of the mixed solvents and its influence on the in vitro release of PG and M400.
 Materials and methods. The mixed solvents PG - M400 were studied over the entire concentration range at temperatures from 293.15 to 313.15 K. The density and dynamic viscosity were determined, and the excess density, excess dynamic viscosity, activation parameters of viscous flow, and excess activation parameters of viscous flow were calculated. The in vitro release of PG and M400 from the mixed solvents was studied using vertical diffusion cells. The content of PG and M400 in the receptor medium was determined by gas chromatography using validated analytical procedures. The release rate, cumulative content, percentage of released PG or M400, coefficients of correlation and coefficients of determination were calculated.
 Results. The isotherms of excess density and excess dynamic viscosity of the mixed solvents PG-M400 pass through a maximum. The enthalpy makes the main contribution to the free activation energy of the viscous flow. The excess free energy is positive and has small values; the values of the excess entropy and excess enthalpy are negative, and the isotherms have the minimum at PG concentrations of 70‑75mol %. The release parameters of M400 are greater in binary mixtures where the M400 structure predominates. At PG content of ~75 mol %, the release parameters for PG and M400 are identical. With the increase in PG content above 75 mol %, when the PG structure predominates in the system, the release parameters of PG increase dramatically, and the release parameters of M400 decrease sharply.
 Conclusions. The structure of the binary system PG – M400 depends on its composition. Based on the isotherms of excess activation of viscous flow, it is possible to differentiate the areas where the structure of PG or the structure of M400 dominates, or the mixed structure of the binary solvent prevails. The in vitro release parameters for PG and M400 depend on the structure of the mixed solvents. The greatest difference in the release parameters of PG and M400 was observed in the area where the structure of PG dominates

Effect of [Bmim][Br] and [Emim][HSO4] on the solution properties of pyridoxine HCl at various temperatures: A physicochemical, thermodynamic and spectroscopic approach

The current paper is concerned with deliberation of physicochemical and thermodynamic parameters of pyridoxine HCl in water and binary aqueous (0.05, 0.10 and 0.15) mol kg−1 [Bmim][Br]/[Emim][HSO4] media by means of empirically acquired density, velocity of sound and viscosity data. These parameters have been evaluated for the examination of interactions prevailing between pyridoxine HCl and [Bmim][Br]/[Emim][HSO4] in aqueous medium over a temperature range (293.15 to 313.15) K and at 0.1 MPa pressure. The deliberated parameters include partial molar volumes (Vϕo), partial molar isentropic compressibilities (Kϕ,so), Jones-Dole coefficients (A and B) and thermodynamic parameters of viscous flow (Δμ10,Δμ20, ΔH20andTΔS20) etc. Further, apparent specific volume (ASV) has been studied for pyridoxine HCl in water and in aqueous IL systems, showing that the studied systems have sweet-bitter taste at all temperatures and compostions. Moreover, the trends corresponding to deviation in computed parameters have been analysed in light of the solute−solvent and solute−solute interactions prevailing in the systems. Additionally, UV spectral analysis has been carried out for the interpretation of interactions prevailing between pyridoxine HCl and [Bmim][Br]/[Emim][HSO4]. By the obtained results, we have inferred that there is dominance of ion-hydrophillic and hydrophilic-hydrophillic interactions in the investigational systems.

Внедрение методов суперкомпьютерной оптимизации в процесс проектирования водометных движителей

Object and purpose of research. This study discusses fast boats and waterjet propulsors. The purpose is to design a waterjet impeller shape to required conditions by means of supercomputer-based optimization with further validation of results at sea trials. Materials and methods. The optimization process is governed by a Russian software package pSeven. The computation core is Star CCM+ (Siemens). Parametric 3D model of the impeller is generated in BladePlus software (in-house KSRC development). Hydrodynamic parameters of waterjet are calculated as per CFD methods. Viscous flow parameters are found through the control-volume solution of unsteady Reynolds equations (URANS) closed by the bi-parametric semi-empirical turbulence model. Main results. The optimization studies yielded new shapes for impellers, stators and flow parts of waterjets. These solu-tions are more efficient than the prototype thanks to greater thrust of the propulsion system and lower resistance of the flow part without prejudice to good cavitation performance. Calculated hydrodynamic parameters of waterjets and the estimates for achievable speed of fast boats have been confirmed by the sea trials. Conclusion. Supercomputer optimization ensured successful beginning of the development of Russian waterjet family for fast boats not inferior to universally recognized market leaders in terms of performance parameters.

Elucidation of molecular interactions of aspartic acid with aqueous potassium sorbate and sodium benzoate: Volumetric, viscometric and FTIR spectroscopic investigation

Aspartic acid (Asp), a nonessential amino acid has been taken for the present study. Solutions of different concentrations of aspartic acid were prepared by dissolving it in water and {water + (1.5, 2.0 and 2.5 m) Potassium sorbate (PS)/sodium benzoate (SB)}. Density and viscosity of the solutions were experimentally determined at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K. Volumetric parameters like apparent molar volume (V∅), partial apparent molar volume (V∅0), partial apparent molar expansibility (E∅0) were computed by using standard formulations. Stronger ion-ion, ion-hydrophilic and hydrophilic-hydrophilic interactions between zwitterionic centers (COO- and NH3+) and polar groups of aspartic acid (COOH and NH2) and ions present in aqueous PS/SB are found to dominate the hydrophobic interactions between the nonpolar organic segments of amino acid and PS/SB. Structure building character of aspartic acid in presence of PS/SB are established by the positive values of Hepler’s constant (∂2V∅0/∂T2)P for all compositions of solutions. Positive viscosity B-coefficient (BJ) and negative (∂BJ/∂T)values further establish the structure building character of aspartic acid. Thermodynamic parameters for viscous flow (Δμ20,#,ΔS0,#andΔH0,#) suggest that transition state for viscous flow is less stable than the ground state and formation of transitions state is not thermodynamically favoured. Shifting of IR absorption band for O-H stretching due to H-bonding at 3300–3340 cm-1 confirms changes in solvent structure due to ion-ion and ion–solvent interactions occurring in the investigated systems.

Валидация методики оптимизации пропульсивного комплекса транспортного судна

Object and purpose of research. This research was intended to validate supercomputer-based optimization procedure for propulsion systems of carrier ships, with a case study of hull shape and propeller optimization for a Project 1594 vessel. Materials and methods. The optimization proceeds in Russian software package pSeven. The computation core is Siemens Star CCM+ software. Three-dimensional parametric model of the propeller is generated in KSRC-developed BladePlus software, whereas three-dimensional parametric model of the hull is generated in Siemens NX software package. Hydrodynamic parameters of the propulsion system are obtained as per CFD methods. Viscous flow parameters are obtained through control volume-based solution of unsteady Reynolds equations (URANS) closed by biparametric semi-empirical turbulence model. Main results. The study yielded a new bow shape offering lower wave-making resistance for the same overall dimensions. It also yielded a new shape of propeller offering higher efficiency than the initial one taking into account the limitations for available shaft torque. Design hydrodynamic parameters have been confirmed by the model test data obtained at KSRC Deepwater Test Tank. Propulsion performance calculation has shown a growth in the achievable speed of the optimized propulsion system in different running conditions. Conclusion. The optimization studies intended to improve propulsion efficiency of Project 1594 ships yielded new shapes for hull and propeller. The solution thus obtained features high propeller efficiency and low wave-making resistance of the hull. Numerical simulation results have been confirmed with experimental data.

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.

Improving ethylene glycol transport properties by caffeine – Thermodynamic and computational evidence

In this article, detailed physicochemical characterization of ethylene glycol and caffeine + ethylene glycol mixtures is performed based on density, viscosity and refractive indices measurements in temperature range from (288.15 to 343.15) K. The apparent molar volume (Vϕ), apparent molar volume at infinite dilution (Vϕo), Masson's experimental slope (Sv), limiting apparent molar expansibility, (Eϕo), viscosity B-coefficient, thermodynamical parameters of viscous flow and molar refractions (Rm) have been evaluated from experimental measurements and results are additionally proven by molecular dynamic simulations. The addition of caffeine reduces viscosity of ethylene glycol, while caffeine molecules have high tendency to form self-aggregates due to weak interactions with ethylene glycol. Compared to aqueous solution of caffeine, caffeine + ethylene glycol mixtures are characterized with significantly lower solvation number and with more pronounced caffeine self-aggregation.

Calculation of the three-dimensional turbulent boundary layer in the vessel’s bow and midship area by the integral method

The quality of technical solutions applied in ship design and construction is substantially determined by the validity of viscous flow parameters, especially in the vicinity of thrusters. The influence of shapes on velocity, pressure and turbulence distribution can be assessed by physical experimentation. Along with undeniable advantages, physical modelling has a number of disadvantages: high labour input and cost, limited range of parameters variation (e.g. Reynolds numbers), difficulty in separating the influence of individual factors. Therefore, the development of mathematical models and numerical calculation schemes based on them is extremely relevant. Calculation of friction resistance and calculation of the velocity field in the vicinity of a vessel comes down to the calculation of its boundary layer and trace parameters. Current mathematical models with a planar representation, i.e. working with projections rather than real curves, do not give an accurate description. This has led to the need for a mathematical model that can address all of the required characteristics of a three-dimensional turbulent boundary layer. Both differential and integral methods are used to calculate three-dimensional boundary layers. The model is capable of calculating the characteristics of the spatial boundary layer in the stern and the viscous wake, in the bow and in the middle of the vessel. The model is quite versatile: it has been successfully used both for computing the boundary layer characteristics in the bow and midship area by the integral method based on the thick boundary layer concept, and for computing the turbulent flow in the stern and viscous wake by the differential method based on the partial parabolic concept using the k-ε turbulence model. In this paper we will elaborate on the integral method calculation.

Viscometric and Densimetric Study of Water–PEG–KBr Systems

The dynamic viscosity and density of a water–PEG–KBr system are measured in the ranges of 293.15–323.15 K and 0–0.001 mol parts. Polyethylene glycol samples with average molecular weights of 1000, 1500, 3000, 4000, and 6000 g/mol are used. The concentration of KBr is 0.01 mol parts. The activation parameters of viscous flow (Gibbs energy, enthalpy, and entropy) and the partial molar volume of PEG in a solution are calculated using experimental data in the specified range of temperatures and concentrations. It is shown that the activation parameters of viscous flow grow along with concentration and molar weight. It is found that the partial molar volume of PEG in a solution falls as the concentration rises, and the partial molar volume per monomer does not change, depending on the average molecular weight of PEG. A simple way of determining the hydration number of a polymer molecule is described, based on which the hydration number of a PEG macromolecule in a solution is calculated. It is found that the hydration number of a PEG macromolecule falls as the temperature rises and grows along with the molecular weight.

Insight into solute-solute and solute-solvent interactions of l-proline in aqueous-D-xylose/L-arabinose solutions by using physicochemical methods at temperatures from 293.15 to 318.15 K

The interactions of l-proline with carbohydrates are investigated by using volumetric, viscometric and acoustic properties. The measurements of the densities, ρ, ultrasonic speeds, u and viscosities, η of the l-proline in water and in aqueous-D-xylose/L-arabinose (2.5% and 5% D-xylose/L-arabinose in water) solvents were carried out at temperatures (293.15–318.15) K and at atmospheric pressure of 101 kPa by using digital vibrating tube density and sound analyzer and microviscometer. The experimental data have been used to evaluate the apparent molar volumes, Vϕ, limiting apparent molar volumes, Vϕ°, apparent molar compressibilities, Ks, ϕ, limiting apparent molar compressibilities, Ks,ϕ°, transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr°. The viscosity A and B coefficients, Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1°# and of solute, Δμ2°#, enthalpies, ΔH∘# and entropies, ΔS∘# of viscous flow, were obtained using the viscosity data. The effect of concentration, temperature and solute structure were discussed in terms of solute-solvent and solute-solute interactions prevailing in these systems. The structure making/breaking ability of l-proline is examined in from the sign of temperature derivative of B-coefficient, dB/dT. The thermodynamic parameters of viscous flow for the solutions are also calculated and discussed using transition state theory.

How the presence of ATP affect caffeine hydration and self-aggregation?

Based on data analyzed from volumetric, viscosimetric measurements and computational simulations, caffeine hydration and aggregation properties in aqueous solutions were compared with caffeine properties in the presence of ATP. The experimental values of the apparent molar volume (Vϕ), apparent molar volume at infinite dilution (Vϕo), Masson's experimental slope (Sv), the apparent molar volume of transfer (ΔtrVϕo), limiting apparent molar expansibility, (Eϕo), hydration number, viscosity B coefficient, thermodynamics parameters of viscous flow were calculated in the temperature range from T = (283.15 to 313.15) K. For the additional investigation of the caffeine hydration properties, the molecular dynamics (MD) simulations, the radial distributive functions (RDFs) and spatial distribution functions (SDFs) were performed. Reduced caffeine hydration and pronounced self-aggregation in the ATP presence are linked to its dehydration effect on caffeine molecules. These results point out the ATP negative effects on caffeine, due to undesirable process of active molecule self-aggregation leading to the reduce bioavailability in the biological systems.

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.

Theoretically consistent calculation of viscous activation parameters through the Eyring equation and their interpretation

The activation parameters of viscous flow can be used to probe the molecular interactions in fluids from viscosity experimental data. They are assessed by mathematical derivations of the Eyring equation, but differences in these derivations can generate parameters that lead to conflicting interpretations. In this work, a new method for the estimation of the activation parameters of viscous flow is proposed and compared with two other methods previously reported in the literature. It is shown that the new method is the only presenting theoretically consistent trends, as confirmed by its application to alkanes and ionic liquids.