Solubility of sildenafil citrate in propylene glycol + water mixtures at various temperatures

The solubility of sildenafil citrate (SC) in aqueous mixtures of propylene glycol (PG) was investigated. This study was carried out at different mass fractions of PG ranging from 0.1 to 0.9 at T = 293.2–313.2 K. The solubility of SC in the mixed solutions increased with increasing temperature and PG mass fraction.

The solubility values were correlated by two co-solvency models (Jouyban–Acree model and van’t Hoff–Jouyban–Acree model). The mean relative deviations (MRD) were 5.7% and 5.5%, respectively. Density of the SC-saturated solutions over the entire solvent composition and temperature range was also measured and the results correlated with the Jouyban–Acree model. Furthermore, the apparent thermodynamic properties, dissolution enthalpy, dissolution entropy and Gibbs free energy change of dissolution process of SC in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of SC in these mixed solvents is an endothermic process.     

Ion-solvent interactions in aqueous solutions at various temperatures

The temperature variation of the limiting partial molar volumes of a number of electrolytes in aqueous solution has been examined in terms of solvent electrostriction. The Desnoyers, Verrall, and Conway theory has been modified and extended to cover the temperature range 0–100°C. It has been shown that electrostriction effects alone cannot account for the observed maxima in the V° –T plots for various electrolytes. It is concluded that solvent structural changes over this temperature range may well be important.     

Investigation of molecular interactions in binary mixtures of homologous series of aliphatic alcohols with 2-methoxyaniline at various temperatures

ABSTRACT

Thermodynamic and transport properties (excess molar volume, excess isentropic compressibility and deviation in viscosity) are calculated from the experimental density, speed of sound and viscosity. The results are analysed in terms of rupture of hydrogen-bonded chain as the dipolar interaction between 2-methoxyaniline and 1-alkanol (1-hexanol, 1-heptanol and 1-octanol) exceeds the intermolecular interaction through dipole-dipole and hydrogen bonding between these unlike molecules. The V^E results are analysed in the light of Prigogine-Flory-Patterson theory. Analysis of each of the three contributions viz. interactional, free volume and P* to V^E has shown that interactional contribution are positive for all systems, the free volume effect and P* contribution are negative for all the mixtures.     

Investigation of molecular interactions in binary mixtures of 2-methoxyaniline with cyclic ketones at various temperatures through thermophysical properties

Journal of Thermal Analysis and Calorimetry - Using recently constructed experimental phase diagram isotactic polypropylene–1,2,4,5-tetrachlorobenzene (TeCB), we formulate a physically...     

Compressibilities of cyclohexane and toluene mixtures at various temperatures

The isothermal compressibilities _T for cyclohexane+toluene mixtures at 25, 35, 45 and 60°C have been determined by direct piezometric measurement. By combining our results with supplementary literature data, we have calculated the isentropic compressibility _S. Values of the excess functions (V^E/_p)_T, _T ^E and _S ^E were also calculated at four temperatures and their behavior as a function of mole fraction and temperature was studied.     

Solubility of celecoxib in carbitol + water mixtures at various temperatures: experimental data and mathematical modelling

ABSTRACT

A brief review on various solubilisation techniques of coxibs is provided and the solubility of celecoxib (CXB) in binary solvent mixtures of {carbitol (1) + water (2)} is reported at temperatures ranging from 298.2 to 313.2 K. Three cosolvency models, i.e. Yalkowsky model, Jouyban–Acree model and the Jouyban–Acree–van’t Hoff model, have been used for correlating the reported data, and the mean relative deviations are employed to evaluate the accuracy of the fitness. Solubilities are also predicted by the generally trained version of the Jouyban–Acree model and its combined model with Abraham solute parameters previously proposed for {carbitol (1) + water (2)} binary mixtures. Furthermore, the apparent thermodynamic properties of dissolution process of CXB in all -investigated solvents were calculated according to van’t Hoff and Gibbs equations.     

Measurement and modelling of solubility data for bosentan in 1-propanol + water mixtures at various temperatures

ABSTRACT

The experimental solubility determination of bosentan (BST) in 1-propanol + water mixtures within temperature range, T = (293.15–313.15) K were performed by applying the shake-flask method. The solubility data were correlated by four cosolvency models, which are the Jouyban-Acree, Jouyban-Acree-van’t Hoff, modified Wilson, and Yalkowsky equations. The back-calculated solubility using the Jouyban-Acree-van’t Hoff equation presents better compatibility with the experimental data than those by the other models. Thermodynamic properties such as apparent molar enthalpy, entropy, and Gibbs free energy change of BST dissolution process in the binary (1-propanol + water) mixtures were also calculated which indicative of the inspontaneous process of dissolution.     

Viscosities of 1,2-Ethanediol-2-Methoxyethanol solvent mixtures at various temperatures

Viscosities were measured for binary solvent mixtures of 1,2-ethanediol-2-methoxyethanol at 19 temperatures ranging from –10 to 80°C. Several different equations, such as those of Arrhenius, Waterton, and Williams et al., have been applied in order to establish the best regression fit for as a function of temperature. For this binary solvent system, the viscometric properties are continuous but not a linear function of the mixture composition. The deviations of the excess viscosities from ideality were found to be useful in detecting the formation of solvent-cosolvent complex species and to evaluate their stoichiometrical composition.     

Volumetric properties of binary mixtures of alcoxyethanols with tert-butyl ethyl ether at various temperatures

Densities at 293.15, 298.15, 303.15, 308.15 and 313.15 K of the binary liquid mixtures made of tert-butyl ethyl ether with either 2-ethoxyethanol, or 2-(2-ethoxy)ethoxyethanol, or 2-[2-(2-ethoxy)ethoxy]ethoxyethanol have been measured over the whole mixture compositions. These data have been used to compute the excess molar volumes (V^E). The excess molar volumes always are negative over the entire range of composition for all the binary mixtures investigated. The changes of V^E with variations of the composition and the chain-length of the alkyl groups in the alkoxyethanol molecules are discussed in terms of possible intermolecular interactions.     

Molecular interactions in poly(ethylene glycol)-water mixtures at various temperatures: density and isentropic compressibility study.

The densities and sound velocities of mixtures of water with poly(ethylene glycol), poly(ethylene glycol) monomethylether, and poly(ethylene glycol) dimethylether with mean molar weights between 250 and 500 have been measured as a function of mixture composition and temperature between 10 and 40 degrees C. Isentropic compressibilities are derived from the data and are compared to those for the ethylene glycol/water system and for other organic solvent/water mixtures. Relative minima in the mixture volume to ideal volume ratio and in the dependence of the compressibility upon mixture composition are discussed in terms of the conformational variability of the chainlike oligomers, of hydrogen-bonded networks, and of water clusters between the oligomer chains.     

Size ratio effects on interparticle interactions and phase behavior of microsphere-nanoparticle mixtures

We investigate the interparticle interactions and phase behavior of microsphere-nanoparticle mixtures of high charge asymmetry and varying size ratio. In the absence of nanoparticles, negligibly charged microspheres flocculate as a result of van der Waals interactions. Upon addition of a lower critical nanoparticle volume fraction, the microspheres are stabilized by the formation of nanoparticle halos around each microsphere. , A weak attraction between the two species leads to a pronounced enhancement of the effective nanoparticle concentration near the microsphere surface relative to the bulk solution. Above an upper critical nanoparticle volume fraction, the microspheres undergo reentrant gelation. Binary mixtures, in which the effective nanoparticle size is reduced at a fixed microsphere diameter, exhibit a narrow window of stability that ultimately disappears with increasing ionic strength. By contrast, binary mixtures of varying microsphere diameter are stabilized at similar nanoparticle volume fractions and exhibit a broader window of stability with decreasing size ratio. This unexpected observation may arise from the reduced attraction between smaller microspheres because negligible differences in nanoparticle halo formation are observed in these mixtures.     

Solubility of bosentan in {propylene glycol + water} mixtures at various temperatures: experimental data and mathematical modelling

Solubility measurements were performed for bosentan (BST) in binary mixtures of propylene glycol (PG) and water at atmospheric pressure within the temperature range, T = 293.2 – 313.2 K by employing a shake-flask method. Generated solubility data were correlated with Jouyban-Acree-van’t Hoff model and the accuracies of the predicted solubilities and model performance were illustrated by mean relative deviations (MRD). Furthermore, the apparent thermodynamic properties of BST dissolving in all the mixed solvents were calculated, and the obtained results show that the dissolution process is endothermic. By using the inverse Kirkwood–Buff integrals, it was observed that BST is preferentially solvated by water in water-rich solvent mixtures and preferentially solvated by PG (as a cosolvent) in the composition range of 0.20 < x₁ < 1.00 at 298.2 K.     

Further calculations on solubility of dipyrone in some binary solvent mixtures at various temperatures

The recently reported solubility data of dipyrone in binary solvent mixtures of {ethanol + water}, {methanol + ethanol} and {methanol + 1-propanol} at various temperatures have been used to report further numerical results based on the Jouyban–Acree model.     

Static permittivity and molecular interactions in binary mixtures of ethanolamine with alcohols and amides

The relative static permittivity at 1 MHz and high frequency limit permittivity at wavelength of sodium-D line of the binary mixtures of ethanolamine (2-aminoethanol) with alcohols (ethyl alcohol, ethylene glycol and glycerol) and amides (formamide, N,N-dimethylformamide and N,N-dimethylacetamide) have been investigated over the entire concentration range at 30 °C. The excess permittivity and Kirkwood correlation factor of the binary mixtures were determined to explore the hydrogen-bonded hetero-molecular interactions and their dependence on the number of hydroxyl groups of alcohols molecules and the extent of substitution in amides molecules. Results confirm that ethanolamine form weak H-bond interactions with alcohols, N,N-dimethylformamide and N,N-dimethylacetamide, but the dipolar alignments in these mixtures vary with number of hydroxyl group of alcohols and their molecular size. Comparatively strong H-bond interactions were found between ethanolamine and formamide molecules with reduce in number of parallel aligned effective dipoles.     

Structural-thermodynamic characteristics and intermolecular interactions in mixtures of strongly associated solvents with aprotic amides

Thermodynamic characteristics of mixtures of aprotic amides with water and organic solvents with hydrogen bond networks are calculated. Within a model approach the specific and non-specific components of the total energy of the intermolecular interaction are determined, based on which the corresponding contributions to the enthalpies of component mixing are calculated. It is found that negative enthalpies of mixing in the mixtures under study are due to non-specific interactions rather than heterocomponent specific ones. It is shown that the difference in the structural-thermodynamic characteristics of aqueous and nonaqueous mixtures of aprotic amides is mainly caused by packing features of solutions and the behavior of hydrogen bond networks of water and organic solvents.     

Excess molar volumes of the binary mixtures of polyethylene glycol 300 with ethoxyethanols at various temperatures

Densities at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K in the binary liquid mixtures of polyethylene glycol 300 with 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, or 2-{2-(2-ethoxyethoxy)ethoxy}ethanol have been measured over the entire range of mixture compositions. These data have been used to compute the excess molar volumes. The excess molar volumes are negative over the entire range of composition for all studied mixtures. The results are discussed in terms of intermolecular interactions in the bulk binary mixtures.     

Viscosity studies of solutions of water inn-aliphatic alcohols at various temperatures

Viscosity measurements have been made at 25°C on solutions of water inn-propanol, and at 15, 25, 35, and 45°C on solutions of water inn-butanol,n-pentanol, andn-hexanol over the respective solubility ranges. For most of the systems, water decreases the viscosity of the dry alcohols, while for the lower members of the series literature data report an increase in viscosity on addition of water. These results are rationalized in terms of two kinds of interaction between water molecules and alcohols: participation of water molecules in chain formation for the lower alcohols and formation of water-centered complexes for butanol and higher alcohols.     

Study of molecular interactions in binary mixtures of formamide with 2-methoxyethanol and 2-ethoxyethanol at varying temperatures

The thermophysical properties of binary mixtures of formamide with 2-methoxyethanol and 2-ethoxyethanol have been investigated in this article. Densities, refractive index, ultrasonic velocity and viscosity for the two binary mixtures viz. formamide with 2-methoxyethanol and 2-ethoxyethanol have been measured over the entire composition range at 293, 303 and 313 K and at atmospheric pressure. The excess molar volume, the molar refraction deviation, excess Gibb's free energy of activation for viscous flow, excess isentropic compressibility, deviation in viscosity, excess free volume and excess molar enthalpy have been computed using experimental data. These excess parameters have been correlated with Redlich–Kister polynomial equation. The results have been interpreted on the basis of strength of intermolecular interaction occurring in these mixtures. Densities, refractive index and ultrasonic velocity were correlated with second-order polynomial equation. The molar volume and excess partial molar volume at infinite dilution have also been calculated for both the mixtures.     

Densities and relative permittivities for mixtures of 2-methoxyethanol with DEA and TEA, at various temperatures

Densities () and relative permittivities () of numerous binary mixtures of 2-methoxyethanol (ME) (1)+diethylamine (DEA) (2) at four temperatures and 2-methoxyethanol (1)+triethylamine (TEA) (2) at five temperatures, between (291.15 and 313.15) K, are reported. These results are used to calculate excess molar volumes, and deviations in the relative permittivities. The results are fitted to the Redlich-Kister polynomial equation to estimate the binary coefficients and standard errors. Furthermore, the experimental results are used to disclose the nature of binary interactions in the bulk of studied the binary mixtures.This revised version was published online in November 2005 with corrections to the Cover Date.