Prediction of anthracene solubilities in binary alcohol+alcohol solvent mixtures using alcohol-specific mobile order theory stability constants

Experimental solubilities are reported for anthracene dissolved in six binary mixtures containing 2-methyl-1-pentanol with 1-propanol, 2-propanol, 1-butanol, 2-butanol 2-methyl-1-propanol, and 1-octanol at 25°C. Results of these measurements, along with previously published solubility data for anthracene in binary alcohol + alcohol solvent mixtures, are used to test the limitations and applications of expressions derived from mobile order theory and the Kretschmer-Wiebe association model. Alcohol-specific mobile order theory association constants are calculated from vapor-liquid equilibrium data for binary alkane + alcohol solvent mixtures and used in the solubility predictions. For the 57 systems considered, both models provided very accurate predictions of the anthracene solubilities, with an overall average absolute deviation between measured and calculated values being 1.7 and 1.2% for mobile order theory and the Kretschmer-Wiebe association model, respectively.     

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system [LiBr/Ca(NO₃)₂ mass ratio=1.0] were measured in various absorbent (lithium bromide+calcium nitrate) concentration and temperature ranges. Solubilities were measured by a visual polythermal method in the temperature range from 282.55 to 343.45 K and the experimental values were correlated with two least-squares regression equations as a function of temperature. The average absolute deviation between the experimental and the calculated solubilities was 0.23%. Vapor pressures were measured by the boiling point method in the temperature range from 334.65 to 385.85 K and in the absorbent concentration range from 44.9 to 70.3 mass%. The experimental values were correlated with an Antoine-type equation and the overall average absolute deviation was found to be 1.06%.     

Study of mixed micelles and interaction parameters for polymeric nonionic and normal surfactants

Surface tension (ST) measurements were carried out on various binary mixtures of the "normal" surfactants, such as nonionic surfactant, hexaethylene glycol mono-n-dodecyl ether(C12EO6), and cationic surfactant, tetradecyltrimethylammonium bromide (TTAB), and polymeric copolymer, Pluronic F127, F127(PPO)-g-PVP, and F127(PEO)-g-PVP. In all cases mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured using surface tension measurement. In the region where mixed micelles are formed, the interaction of two "normal" surfactants and three "polymeric" nonionic surfactants showed synergistic behavior and the results were analyzed using a interaction parameter, beta, which characterized the interaction in the mixed micelle and introduced by a regular solution theory. The regular solution theory can be applied to describe the interaction between TTAB and C12EO6, and graft polymeric surfactants systems. The results discussed in this paper indicated that regular solution theory has broader extent of application.     

The Solubilities of Esters of 4-Hydroxybenzoic Acid,Determined Separately and Together,in Aqueous Solutions of 2-Hydroxypropyl-β-cyclodextrin

Abstract

The solubilities of four esters of 4-hydroxybenzoic acid have been investigated singly and together in water and in aqueous solutions of 2-hydroxypropyl-β-cyclodextrin (HPCD). Values obtained for the solubilities of methyl (MP), ethyl (EP), propyl (PP), and butyl (BP) esters in water agreed welt with literature values, when determined separately. When measured together the solubilities of the methyl and butyl esters increased slightly, that of the ethyl ester decreased slightly, and the solubility of the propyl ester decreased by approximately 50%. Association constants for complexes of esters and HPCD determined separately in water agreed well with literature values, declining from methyl to ethyl and then increasing through propyl to butyl. When the association constants were determined for the esters together in solutions of HPCD the same pattern was noted, but the large decreases in association constants may indicate some other process in addition to competition between the esters for the HPCD molecules.     

Solubility Prediction of Active Pharmaceutical Compounds with the UNIFAC Model

The crystallization from solution of an active pharmaceutical ingredient requires the knowledge of the solubility in the entire temperature range investigated during the process. However, during the development of a new active ingredient, these data are missing. Its experimental determination is possible, but tedious. UNIFAC Group contribution method Fredenslund et al. (Vapor–liquid equilibria using UNIFAC: a group contribution method, 1977; AIChE J 21:1086, 1975) can be used to predict this physical property. Several modifications on this model have been proposed since its development in 1977, modified UNIFAC of Dortmund Weidlich et al. (Ind Eng Chem Res 26:1372, 1987), Gmehling et al. (Ind Eng Chem Res 32:178, 1993), Pharma-modified UNIFAC Diedrichs et al. (Evaluation und Erweiterung thermodynamischer Modelle zur Vorhersage von Wirkstofflöslichkeiten, PhD Thesis, 2010), KT-UNIFAC Kang et al. (Ind Eng Chem Res 41:3260, 2002), \(\ldots \) In this study, we used UNIFAC model by considering the linear temperature dependence of interaction parameters as in Pharma-modified UNIFAC and structural groups as defined by KT-UNIFAC first-order model. More than 100 binary datasets were involved in the estimation of interaction parameters. These new parameters were then used to calculate activity coefficient and solubility of some molecules in various solvents at different temperatures. The model gives better results than those from the original UNIFAC and shows good agreement between the experimental solubility and the calculated one.     

Drug-Delivery by Ion-Exchange: Part II: Physico-Chemical Properties of Ester Pro-Drugs of Propranolol

Abstract

The pKa values, solubilities and partition coefficients of a series of O-n-acyl propranolol pro-drugs have been estimated. The direct measurement of solubilities is limited by the instability of the esters and pK values are difficult to estimate by potentiometric titration due to low solubilities. Titrations in a range of aqueous methanolic solutions provide an estimate of the pK_a while titration under non-logarithmic conditions, when excess, undissolved base is present in the system, allows the determination of solubility.     

Influence of Physicochemical Interactions on the Properties of Suppositories,II, Interactions Between the Constituents of Fatty Suppository Bases and Ketoprofen or Metronidazole

Abstract

The rate at which drugs are released from suppositories and absorbed by the rectal mucosa tends to decrease with increasing solubility of drug in the base or increasing strength of interaction between them. The solubility of ketoprofen or metronidazole in various molten mono-acid triglyceride constituents of fatty suppositories was determined at various temperatures and extrapolated to 37°C and to 100°C. With increasing acyl chain length of the triglyceride solvent the solubility of both drugs tended to decrease and the enthalpy and entropy of solution, determined by van't Hoff or Hildebrand plots, tended to become increasingly positive. The solubility data did not accord with regular solution theory, indicating that specific solute-solvent interactions are important in the solutions. The R_f values of the drugs were determined on triglyceride-impregnated layers of silica gel using water: methanol: glacial acetic acid (10:10: 1 v/v) as the moving phase. For ketoprofen the rank order of the R_f values was the inverse of that of the solubility values, but metronidazole gave a poor rank order correlation between partition chromatography and solubility. Therapeutic concentration of the drugs (3.4% w/w ketoprofen or 23.4% w/w metronidazole) had small effects on the phase diagrams of binary mixtures of the triglycerides, the eutectic temperatures being lowered by less than 1°C and the eutectic composition of the lower melting triglyceride being increased by about 10% w/w. The implications of these data to drug release are discussed.     

Vapor-liquid equilibrium and volumetric properties calculations for solutions in the supercritical carbon dioxide

The calculations of gas solubilities in supercritical solvents require equations of state remaining accurate in the critical range, which are difficult to obtain with classical models. In this work, the Helmholtz energy of a mixture is considered as the sum of the Helmholtz energies of pure components taken at a constant packing fraction and of a residual term which may have the form of a RedlichKister, Van Laar, NRTL, UNIQUAC, or UNIFAC function. Thus it is possible to assign to a given component an equation of state whose form is different from that of the others. This model has been applied to binary systems containing supercritical carbon dioxide. The results are improved with respect to those obtained with the classical model for vapor-liquid equilibria and for volumetric properties.     

Consideration of some dilute-solution phenomena based on an expression for the Gibbs free energy

Rigorous expressions based on the Lennard-Jones (6–12) potential, are presented for the Gibbs and Helmholtz free energy of a dilute mixture. These expressions give the free energy of the mixture in terms of the thermodynamic properties of the pure solvent, thereby providing a convenient means of correlating dilute mixture behavior with that of the pure solvent. Expressions for the following dilute binary solution properties are derived: Henry's constant, limiting activity coefficients with their derivatives, solid solubilities in supercritical gases, and mixed second virial coefficients. The Henry's constant expression suggests a linear temperature dependence; application to solubility data for various gases in methane and water shows a good agreement between theory and experiment. In the thermodynamic modeling of supercritical fluid extraction, we have demonstrated how to predict new solubility-pressure isotherms from a given isotherm, with encouraging results. The mixed second virial coefficient expression has also been applied to experimental data; the agreement with theory is good.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Phase Separation Line for Solid Mixtures of 3He in 4He

The excess pressure due to the phase separation of solid mixtures of ³He in ⁴He held at a constant volume was measured and used for constructing the phase separation diagram of this system. We obtained high-quality homogeneous samples of the solid mixtures after several cycles of cooling down and heating up the two-phase crystal. This gave reliable and reproducible experimental data without hysteresis efects. We compared the phase diagram line obtained with various theoretical approaches, which describe the phase separation of the helium isotope mixtures. The regular solution model can not describe the experimental data well and neither can the asymmetrical Mullin's model. Good agreement is observed only with the theory of Edwards and Balibar which takes into account the difference between the crystal symmetry (hcp and bcc) of the coexisting phases.     

A variant of the endochronic theory of plasticity with a singular kernel for describing complex deformation processes

The effectiveness of the application of equations of state with a weak peculiarity of the endochronic theory of plasticity in describing complex processes is investigated. The influence exerted by the magnitude of the bend angle of the stress path and various plastic-strain paths on prediction of the material's mechanical behavior is analyzed. The results obtained are compared with the solution for a model employing a regular kernel.Translated from Problemy Prochnosti, No. 4, pp. 97–102, April, 1990.     

Solubility of Various Sulfonamides in N-Alkanols II. Thermodynamic Parameters

The solubilities of several useful sulfonamides were studied at three temperatures over a wide spectrum of polarity of normal alcohols. Thermodynamic elements were generated from both literature values and experimental values of solubility as a function of temperature. Although all these sulfonamide solutions were of a dilute nature, the thermodynamic parameters that were obtained gave a set of results of complex nature. It was possible with this approach to determine the values of the mixing functions for enthalpy and entropy, activity coefficients and the excess free energy function. The overall solution     

The Dortmund Data Bank: A computerized system for retrieval,correlation, and prediction of thermodynamic properties of mixtures

The Dortmund Data Bank (DDB) was started in 1973 with the intention to employ the vast store of vapor-liquid equilibrium (VLE) data from the literature for the development of models for the prediction of VLE. From the beginning, the structure of the DDB has been organized in such a way that it was possible to take advantage of the full potential of electronic computers. With the experience gained in fitting and processing VLE data, we extended the DDB system to other types of mixture properties, i.e., liquid-liquid equilibria (LLE), gas solubilities (GLE), activity coefficients at infinite dilution , heats of mixing (h ^E), and excess heat capacities. Besides the files for mixture properties, the DDB contains pure-component data and program packages for various applications. New experimental data are checked for consistency before they are stored. For data retrieval user-specified search masks can be used. The data files are available via an online data service and through the Dechema Chemistry Data Series. For the purpose of data correlation and model testing, parameter fitting is performed with an optimization routine (Nelder-Mead). In the past years the DDB system has been successfully employed for the development of prediction methods for VLE, LLE, GLE, , and h ^E (UNIFAC, mod. UNIFAC, etc.).Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Solubility of C70 in Organic Solvents

The solubility of C⁷⁰ in various organic solvents has been measured at 303 K for the first time. The solubilities vary from 2 μg/ml in pentane to 36 mg/m1 in o-dichlorobenzene. The solubility is correlated with solvent properties such as Hildebrand solubility parameter and polarisability. The solubility parameter shows good correlation with the solubility for most of the organic solvents studied, with the exception of carbon disulphide and o-dichlorobenzene. The polarisability parameter also explains the wide range of solubility in various organic solvents. However, both the solvent parameters do not satisfactorily explain the trend in the observed solubility over the entire range of solvents.     

A comparison of phase equilibria in some II-IV-VI compounds based on PbTe

The solubilities of the group II elements Cd, Zn, Hg, Ca and Mg in PbTe are compared over the temperature range 250 to 800° C. Cd, Zn and Mg have retrograde solubilities whilst Hg and Ca are virtually insoluble in “as-grown” material. A consequence of these solubilities is a change in the properties of the alloys compared with PbTe. Thus the phase widths of the Cd/PbTe, Mg/PbTe and Zn/PbTe systems differ from that of PbTe. With the exception of the Zn/PbTe system, (where there is reasonable evidence to support the solubility of Zn in PbTe) there is a significant change in all measured electrical properties compared with PbTe.     

Solubility of helium in melts of the metallic glass system Pd-Ni-P and in related systems

Glass melts of the metallic alloy system Pd_10–70Ni_10–70P_14–26 were saturated with helium gas during the melt-spinning process. Some melts with platinum substituted for palladium; manganese, iron or cobalt for nickel; and boron for phosphorus could also be saturated. The helium could be extracted from the glasses and the amount of gas was quantitatively measured with a mass spectrometer. The helium solubilities, obtained between 750 and 1250° C, varied between about 2 and 45 (l He per mol glass) (T/273). These solubilities turned out to be strongly composition-dependent. This fact is discussed in terms of different short-range order structure units which are directly related to the free volume available for the gas solution process.     

Kriometric determination of purity of materials forming solid solutions with their contaminants

The standard kriometric method of determination of impurity concentration x is based on measuring the lowering of melting (or freezing) point ΔT_m with respect to the ultra-pure material. However, the method is applicable only if a liquid solution coexists with a pure solid. We have studied the problem of kriometric evaluation of concentration of an impurity which forms solid solutions with the main component. First, melting points were determined by differential scanning calorimetry for a number of samples of acetanilide contamrinated to a varying degree with phenacetine. Second, x values were calculated by three procedures and compared with true values. Two methods gave results which were not entirely satisfactory. A third method, based on the theory of strictly regular solutions, renders computed values of impurity concentrations virtually coinciding with the true ones.     

Solubilities, Vapor Pressures, and Heat Capacities of the Water + Lithium Bromide + Lithium Nitrate + Lithium Iodide + Lithium Chloride System

The optimum mole ratio of lithium salts in the H₂O + LiBr + LiNO₃ + LiI + LiCl system was experimentally determined to be LiBr : LiNO₃ : LiI : LiCl = 5 : 1 : 1 : 2. The solubilities were measured at temperatures from 252.02 to 336.75 K. Regression equations on the solubility data were obtained with a least-squares method. Average absolute deviations of the calculated values from the experimental data were 0.15% at temperatures <285.18 K and 0.05% at temperatures 285.18 K. The vapor pressures were measured at concentrations ranging from 50.0 to 70.0 mass% and at temperatures from 330.13 to 434.88 K. The experimental data were correlated with an Antoine-type equation, and the average absolute deviation of the calculated values from the experimental data was 2.25%. The heat capacities were measured at concentrations from 50.0 to 65.0 mass% and temperatures from 298.15 to 328.15 K. The average absolute deviation of the values calculated by the regression equation from the experimental data was 0.24%.     

Experimental determination of metastable zonewidth,induction period,interfacial energy and growth of non-linear optical l-Glutamic Acid Hydrochloride single crystals

Single crystals of l-Glutamic Acid Hydrochloride (LGAHCl) were grown by low temperature solution growth technique. The induction periods were measured at various supersaturations and hence the interfacial energies were evaluated. The experimentally evaluated values of interfacial energies are found to be in good agreement with theoretically predicated values.     

Investigation on the nucleation kinetics of l-arginine acetate single crystals

Single crystals of l-arginine acetate (LAA) were grown by low temperature solution growth technique. The induction periods were measured at various supersaturations and hence the interfacial energies were evaluated. The experimentally evaluated values of interfacial energies are found to be in good agreement with theoretically predicated values.