Solubility Data Research Articles

Molecular simulation and solubilities of (R,S)- and (S)-tetramisole hydrochloride in two binary solvents

In this article, the molar fraction solubility of (R,S)- and (S)-tetramisole hydrochloride in two binary solvents (methanol + ethanol and methanol + toluene) was measured by experiments between 283.15 K and 323.15 K. Then four different equations including Apelblat equation, λh equation, GSM equation, Jouyban-Acree equation were applied to connect the measured solubility data of (R,S)- and (S)-tetramisole hydrochloride, where Apelblat equation had the minimum ARD%. The crystal structures together with intermolecular interactions of (R,S)- and (S)-tetramisole hydrochloride were then analyzed. In addition, the infrared spectra were also simulated using dimer configurations. Furthermore, molecular dynamic simulations including radial distribution function (RDF) combined with solvation free energy were performed to explore solvent–solvent interactions along with solute–solvent interactions. The results showed that there was co-solvency in methanol + toluene binary solvent. According to simulation results, both solvent–solvent interactions and solute–solvent interactions played an important role in affecting the solubilities of (R,S)- and (S)-tetramisole hydrochloride. In the end, combining solid state characterization and ternary phase diagrams, (R,S)-tetramisole hydrochloride was determined to be a racemic compound. All the results in this paper can provide theoretical support for enhancing crystallization resolution techniques for chiral drugs.

Solubility determination, Hansen solubility parameter, molecular simulation and thermodynamic properties of 2-anilino-6-(dibutylamino)-3-methylfluoran in four binary solvent mixtures from 283.15 K to 323.15 K

The laser monitoring method was used to assess the solubility of 2-Anilino-6-(dibutylamino)-3-methylfluoran (ODB-2) in four binary solvent systems (methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate + acetonitrile) at temperatures ranging from 283.15 K to 323.15 K. The results indicated that the solubility of ODB-2 increased with the increasing temperature and molar fraction of the ester solvent. Five models, including the Apelblat model, λh model, CNIBS/R-K model, Ma model, and Sun model, were applied to fit the experimental ODB-2 solubility data. Among these models, the Apelblat model and CNIBS/R-K model performed significantly better than the other models. Moreover, it was found that the Hansen solubility parameter played a significant role in explaining the dissolving behavior of ODB-2 in the four binary solvents. The intermolecular interactions between solute and solvent, as well as between solvent molecules themselves, were studied using the radial distribution function obtained through molecular dynamics simulations. The findings suggested that the dissolving behavior of ODB-2 was closely related to the intermolecular forces among solute–solvent and solvent–solvent. The thermodynamic properties of the dissolution process, including enthalpy and entropy changes, were calculated using the modified van't Hoff equation. These results demonstrated that the dissolution of ODB-2 was an endothermic process driven by entropy.

Highly efficient nitric oxide absorption by low viscosity superbase/amide deep eutectic solvents through mutual promotion effect

A series of low-viscous deep eutectic solvents (DESs) with superbase as HBA and amide as HBD were designed and prepared for NO absorption. Impressively, both a comparably low viscosity of 8.07 mPa∙s and a high absorption capacity of 6.43 mol∙kg−1 (∼0.19 kg/kg) at 293.2 K were achieved, which was superior to that of other reported absorbents. Through a combination of absorption experiments, FT-IR characterization, and thermodynamic modelling, the results indicated that such a high solubility for NO was originated from the mutual promotion effect between the superbase and the amide. Considering that chemical absorption occurred accompanied with physical one, a reaction equilibrium thermodynamic model (RETM) equation was derived to correlate the experiment solubility data, so that the thermodynamic parameters were obtained to evaluate the absorption process. The absorption-desorption cycle experiment revealed that the regeneration efficiency of the superbase/amide DESs could be high up to 90 %. Given the low viscosity, high absorption capacity and excellent recycle efficiency, the superbase/amide DES was considered as a promising candidate for NO capture and utilization.

Determination of solubility of sildenafil citrate in propylene glycol + 2-propanol and N-methyl pyrrolidone + water: Comparing solubilization power of aqueous or non-aqueous mixtures

For identifying the solubilization power of aqueous and non-aqueous solvent mixtures for sildenafil citrate (SLC), its solubility was determined in four mono-solvents of propylene glycol, 2-propanol, N-methyl pyrrolidone and water along with the binary solvent mixtures of propylene glycol + 2-propanol and N-methyl pyrrolidone + water at 293.2 to 313.2 K and at pressure of 85 kPa. Among the neat organic solvents and also water, N-methyl pyrrolidone presented a high solubilization power for SLC (8.66 × 10-2 at 313.2 K) and its aqueous binary mixtures had also a more ability to solubilize the drug in compared with the binary (propylene glycol + 2-propanol) mixtures (with the highest value of 4.96 × 10–4 at 313.2 K). Besides, increasing the solubility of SLC with raising temperature illustrated that its dissolution in the aforementioned mixtures was endothermic. The equilibrium solid phase crystal of SLC was also characterized with X-ray powder diffraction analysis to identify no polymorphic transformation, solvate formation or crystal transition during the whole solvent crystallization process. Moreover, the experimental mole fractions were modelled by used commonly cosolvency models and regressed the model parameters. The back-calculated mole fractions of SLC by cosolvency models shown a better agreement with the experimental data (overall mean percentage deviation (OMPD) ≤ 7.6 %) and Jouyban-Acree model as a function of temperature and solvent compositions had the best performance (MPD of 3.2 %). Furthermore, the solubility data sets of SLC in 7 binary solvent mixtures were collected from the literature and correlated with the Jouyban-Acree model and its derivates, the OMPDs for the back-computed solubility indicating the generally trained models, especially Jouyban-Acree-Abraham model (MPD of 24.2 %), had an acceptable ability in the prediction of SLC solubility and can be useful in the pharmaceutical industry. Finally, apparent thermodynamic properties of Gibbs free energy, standard enthalpy and entropy of the dissolution processes were also investigated.

CO2 solubility and amine volatility data for low-concentration solutions of MEA, AMP, PZ and CESAR-1 blend (AMP/PZ)

Water-wash section(s) effectively reduce amine compound emissions in amine-based carbon capture processes. Reliable predictions of the behavior of these emission control technologies depend on detailed understanding of the vapor-liquid equilibrium (VLE) of water wash system. However, existing vapor-liquid equilibrium data in the literature focus primarily on solvent-like amine concentrations in amine–CO2–H2O systems; hence, new low-concentration VLE data are needed. In this work, the CO2 solubility in low-concentration solutions of monoethanolamine (MEA), piperazine (PZ), 2-amino-2-methyl-1-propanol (AMP), and AMP/PZ blend (CESAR-1) was investigated for temperatures between 303 and 353 K at atmospheric pressure. Additionally, amine volatility measurements for CO2-loaded low-concentration solutions of MEA, PZ, AMP and CESAR-1 were performed in the range of 313–373 K and 8–96 kPa. Overall, the data show that the CO2 partial pressure increases with increasing CO2 loading and temperature. Similarly, the amine partial pressure increases with increasing pressure and temperature. The new experimental data were compared with two existing VLE models using electrolyte non-random two-liquid activity coefficient models to evaluate the ability of the latter to predict vapor-liquid equilibrium behavior. Both CO2 solubility and amine volatility predictions by the models tend to show significant deviations. The comparison highlight the need for such low-concentration data for all systems studied. This data shall serve to improve existing water-wash modeling tools.

Development of an Activity Coefficient Model for the Aqueous Amino Acid Solution

AbstractThe enthalpy and solubility of aqueous amino acid solutions are essential thermodynamic properties for the modeling of heat and mass balance, and these properties can be estimated by considering the activity coefficient in thermodynamic calculations. In this study, the parameters of a non‐random two‐liquid model were identified using heat capacity and solubility data together to calculate the acceptable activity coefficient for an aqueous amino acid system. As a result, a highly accurate activity coefficient model of an aqueous amino acid solution was developed, and inaccurate alternative solutions regressed with heat capacity or solubility only can be avoided.

Measurement, correlation and thermodynamic analysis of the solubility of dicyandiamide in three binary solvents

Dicyandiamide (DCD) is an important chemical raw material. The solid–liquid equilibrium solubility of DCD in three kinds of binary solvent mixtures (N,N-dimethylformamide (DMF) + ethanol, DMF + acetonitrile, DMF + acetone) at T = (283.15–323.15) K was determined by gravimetric method. The thermodynamic parameters of DCD dissolution in solvents were studied. The solubility of DCD in the three groups of binary mixed solvents increases with the increase of temperature. In three binary mixed solvents, the solubility of DCD increases monotonically with the increase of DMF composition. The modified Apelblat model, van’t Hoff model, λh model, the nonrandom two-liquid (NRTL) model and the Apelblat-Jouyban-Acree model were used to correlate the solubility data. The results show that the modified Apelblat model have the best correlation with the solubility of DCD. The calculation of thermodynamic parameters during the dissolution process indicates that dissolution is exothermic and driven by both enthalpy and entropy. This work can provide reference for improving the crystallization process of DCD, as well as for improving the chemical production process using DCD as raw material.

Insight into the solution thermodynamic properties of cimetidine form A and form B based on experiments and molecular simulations

Cimetidine (CIM) is an antagonist of the type II histamine receptors, and act as a significant agent in the treatment of stomach ulcers. In this work, the effect of polymorphism and solvent type on the thermodynamic properties of CIM was investigated based on experimental results and molecular simulations. The solubility data of two polymorphs for CIM (forms A and B) in organic solvents were measured and correlated with four thermodynamic models. It could be found that the solubility of CIM form A is higher compared to form B. In addition, molecular simulations were adopted to investigate the mechanism of the solubility and stability of the two forms. Hirshfeld surface analysis shows that strong H···N interaction contributes to better stability of form B. Meanwhile, molecular electrostatic potential surface and radial distribution function results indicate that the solubility behavior is significantly influenced by the intensity of the solute–solvent interactions. Finally, the dissolution thermodynamic properties, including the enthalpy change, the Gibbs energy change, and the entropy change, were calculated and the results show that the dissolution process of CIM is endothermic, entropy-driven and spontaneous.

Experimental measurement and modeling of the solubility of fluorinated compounds derived from dichlone in supercritical carbon dioxide

Dichlone, also known as 2,3-dichloronaphthalene-1,4-dione, is a solid organic substance employed in the field of agriculture for its fungicidal properties and as a retardant for vegetable decomposition. The bioactive properties of dichlone can be enhanced by modifying its structure, specifically through the synthesis of new derivatives achieved by replacing the functional groups within its molecular structure. Two new solid dichlone derivatives were synthesized in this work, namely 2-chloro-3-((4-fluorobenzyl)amino)naphthalene-1,4-dione (dCl-2B-F) and 2-chloro-3-((4-fluorophenethyl)amino)naphthalene-1,4-dione (dCl-3 P-F) and measured their solubility in supercritical carbon dioxide at (313, 323, and 333) K and pressures between (9. to 32) MPa. The results indicated that solubility ranged between 30.5 and 47.9 µmol of solute/mol of CO2 for dCl-2B-F, and from 2.2 to 243.5 µmol of solute/mol of CO2 for dCl-3 P-F. The solubility data of dichlone and its synthesized derivatives (dCl-2B-F, dCl-3 P-F, 2-chloro-3-((4-chlorobenzyl)amino)naphthalene-1,4-dione (dCl-2B-Cl), 2-chloro-3-((4-chlorophenethyl)amino)naphthalene-1,4-dione (dCl-3 P-Cl), 2-(benzylamino)-3-chloronaphthalene-1,4-dione (dCl-2B) and 2-chloro-3-(phenethylamino)naphthalene-1,4-dione (dCl-3 P)) was compared using the density-based correlation of Chrastil and the Statistical Associating Fluid Theory of Variable Range Mie-potential (SAFT-VR Mie) equation of state (EoS), to better comprehend the effects of the structural differences on the solubility. As a result, for the Chrastil model, a root mean square deviation (rmsd) of 3% was obtained for dCl-2B-F and 16% for dCl-3 P-F, whereas for the SAFT-VR Mie equation, it averaged 24% for dCl-2B-F and 28% for dCl-3 P-F. It was found that the solubility of the homologous compounds, differing only in one methylene group, increased with solute size (-2B derivatives were less soluble in CO2 than the −3 P ones), contrary to the expected trend, which could be attributed to the increased probability of ring-to-ring interactions as the chain length connecting the rings decreases. This demonstrates that geometric factors, along with the pressure and temperature, affect the behavior of the solubility and these should be accurately represented in the predictive models.

Insight into the dissolution behavior of valsartan (form E) in twelve pure solvents: Solubility, modelling and molecular simulation

Valsartan is an angiotensin II receptor antagonist used to treat hypertension. Crystals of valsartan were prepared and the stability of the valsartan (form E) at different solvents and temperatures was investigated. The solid-liquid equilibrium solubility of valsartan (form E) in twelve pure solvents was determined by a dynamic method at the temperature from 278.15 K to 323.15 K. Among the solvents used in the experiment, the solubility of valsartan (form E) was found to be highest in methanol and lowest in acetonitrile. In straight-chain alcohols, the solubility decreases with the increase of carbon chain length. The modified Apelblat model, λh model and NRTL model were used to correlate the solubility data. The thermodynamic properties of the mixing process such as Gibbs free energy, enthalpy and entropy were estimated by applying the NRTL model. The KAT-LSER model was adopted to explore solvent effects. Hirshfeld surface analysis and molecular electrostatic potential (ESP) were employed to visualize close contacts and charge distribution of valsartan and solvents. In addition, molecular dynamics (MD) simulation was performed to calculate intermolecular interactions between solute and solvent. Radial distribution function (RDF) and the mean square displacement (MSD) analyses were also carried out to explore molecular association and molecular diffusion.

Experimental solubility of FeCO3 in aqueous 3–20 wt% KCl at 25–80 °C

FeCO3 is a mineral, present in both industrial and natural systems. While the solubility of FeCO3 is determining for CO2 storage, and driving for corrosion, it is not well understood. For the development of rigorous modelling, there is a lack of adequate experimental data under relevant conditions to model carbonated systems containing iron.In this work, the solid-liquid equilibrium (SLE) of the ternary system FeCO3-KCl-H2O was measured at atmospheric pressure at temperatures from 25 to 80 °C. The FeCO3 solubility was studied in aqueous KCl solutions from 3 to 20 wt%. 73 new solubility data points for the systems FeCO3–KCl–H2O are presented together with 73 oxidation data points. Results showed that less than 5% of FeCO3 is oxidized in the electrolyte system. The equilibrium concentration of FeCO3 was obtained after 5–10 days with the fastest equilibrium kinetics obtained at the highest temperature, 80 °C. Temperature had a minor impact on the FeCO3 solubility in aqueous KCl solutions. However, the FeCO3 solubility seemed to slightly decrease with temperature. The solubility data was fitted to a first-order rate equation with molality as driving, to obtain kinetic insights. The dissolution rate decreases as a function of KCl concentrations. In some cases, it was 75 % lower than in NaCl. A rate constant of approximately 0.2 1/day was obtained for most experiments. The FeCO3 solubility and kinetic data obtained in this work will allow for a deeper understanding and better prediction of CO2 corrosion and mineralization, suitable for CO2 storage.

Sequence-dependent dipeptide solubility in ethanol-water and DMSO-water solutions

Reliable solubility data is crucial for controlling and optimising crystallisation conditions, to provide a cost-effective purification method with the potential for scaling up. This study investigated the effect of amino acid sequence on determining peptides solubility behaviours. Four dipeptides with different sequences and combinations of alanine and glycine were selected to study their temperature dependent (283.15 K to 313.15 K) aqueous solubilities and solubility in the presence of ethanol and DMSO as antisolvent at 298.15 K. Aqueous solubility data of dipeptides presents the following order: glycyl-L-alanine (gly-ala) > L-alanyl-L-alanine (ala-ala) > glycyl glycine (gly-gly) > L-alanyl glycine (ala-gly). This solubility order has been substantiated by solvation free energy calculations using molecular dynamics (MD) simulations, providing insights into the underlying molecular interactions that govern these solubility patterns. The solubility data also demonstrated difference in the temperature dependency that: gly-gly > gly-ala > ala-gly > ala-ala, corresponding to their dissolution enthalpy order. In the presence of antisolvent range from 0 % to 80 % (by mass) concentration, peptide’s solubility was more susceptible to DMSO than ethanol. Accurate prediction of the solubilities validated the effectiveness of non-random two-liquid (NRTL) model for peptide studies.

Experimental and simulation study on the solubility of 1-naphthylamine in twelve neat solvents

To meet the demand of separating and purifying 1-naphthylamine from the reaction production and filling the solubility data gap, the solubility of 1-naphthylamine in twelve pure solvents (acetone, acetonitrile, ethyl acetate, n-butyl acetate, cyclohexane, n-heptane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, and iso-butanol) was experimentally investigated in the range from 273.15 K to 308.15 K. It was found that the solubility of 1-naphthylamine increases markedly with increasing temperature in all solvent systems. The maximum solubility was 0.8978 (in the solvent of acetone,T = 308.15 K) and the minimum solubility was 0.005485 (in the solvent of n-heptane, T = 273.15 K). Then the experimental solubility data was correlated by the modified Apelblat model, Van't Hoff model, NRTL model, Wilson model, and Margules model. ARD% was calculated to assess the accuracy of the five equations and the results indicated that the modified Apelblat model fits optimally with an average ARD% value of 1.62 %. The effects of various physicochemical properties such as solvent polarity, hydrogen bond donor, hydrogen bond acceptor, and cohesive energy density on solute dissolution behavior were explored. In addition, the apparent thermodynamic properties of 1-naphthylamine in different solvents were analyzed based on modified Van’t Hoff model, which indicated the dissolution process of 1-naphthylamine in selected solvents is endothermic and entropy-driving. Finally, the effect of intermolecular interactions on the dissolution behavior was investigated at the molecular scale through molecular dynamics simulation studies, including molecular electrostatic potential surface, solvation free energy and radial distribution function analysis. This work will provide a fundamental guidance for the crystallization, separation, and purification of 1-naphthylamine.

Phase diagram and density of SiO2–H2O fluid across critical conditions

The SiO2–H2O binary system serves as a basis for understanding complex silicate-water systems. In this study, based on limited existing experimental data of solubility, we propose a new thermodynamic model for SiO2–H2O fluid by modifying the traditional non-random two-liquid model with a simplified polymerization reaction. This model is applicable from 773 K to the anhydrous quartz melting temperature and from 0.5 GPa to at least 2 GPa across the critical conditions. It can predict solid–liquid equilibrium and vapor–liquid equilibrium in good agreement with available experiments. The upper critical endpoint of the SiO2–H2O system is predicted to be at ~ 1.14 ± 0.18 GPa and 1344 ± 87 K. With the new model, we obtain a quantitative three-dimensional pressure–temperature–composition phase diagram of the SiO2–H2O fluid, which greatly facilitates the understanding of the complex phase behavior of this binary around the upper critical endpoint. In addition, since the model is based on the Gibbs free energy foundation, we further discuss the derived density variations of SiO2–H2O fluid along with its complex phase changes in typical geochemical processes.

Theoretical and experimental study on the recovery of bromide by crystallization from pesticide production wastewater

Brominated wastewater from the propyl bromide pesticide production rich in ammonium, sodium and bromine salts at a high concentration of 11 %. For the recycling of chemical resources of this mixed brine salt system, this paper proposes a method for the separation of bromide from bromine-containing chemical wastewater by crystallization. According to the process design needs of the new method, and because 298 K and 323 K are two common temperatures in industrial practice, in this paper, the solubility data of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K and 323 K, as well as its ternary subsystems, NaBr-NH4Br-H2O and NH4Cl-NH4Br-H2O at 323 K were determined by the isothermal solubilization method, and the corresponding phase diagrams were drawn. The solubility of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K was also calculated using the Pitzer model, and the calculated results were in good agreement with the experimental measurements. Finally, based on the theoretical analysis of the phase diagrams of the 298 K and 323 K NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary systems and combined with the phase diagrams of the 298 K NaBr-NaCl-CH3OH system, this paper proposes and designs a salt extraction process route for the brominated wastewater of the propyl bromide pesticide production. Through the separation experiment, the new process proved to be technically feasible and produced NaCl with 100 % purity, Na(Br,Cl) with 98.23 % NaBr, and NH4(Cl,Br) with 99.18 % and 97.57 % NH4Cl, respectively. The new process realizes the resourceful utilization of bromine-containing wastewater, and has the significant advantages of production safety and no emission of three wastes.

Study on the liquid–liquid phase separation phenomenon of iohexol in a binary mixed solvent of methanol and n-butanol: Thermodynamic behavior and molecular dynamics calculation

The impact of oiling-out on the control of the crystallization purification process during iohexol crystallization is significant. Thus, the solubility of iohexol and its oiling-out behavior in a binary solvent mixture of methanol and n-butanol was investigated in this study. The solubility was determined using the equilibrium method at temperatures ranging from 273.15 K to 303.15 K under atmospheric pressure, revealing that solubility increases with temperature and methanol concentration. Four models were employed to model the solubility data, with the CNIBS/R-K model demonstrating the highest correlation. The van't Hoff equation was utilized to calculate the thermodynamic properties, the result indicating that enthalpy predominates in the dissolution process. Furthermore, ternary phase diagrams were constructed to elucidate the nucleation mechanism of iohexol, identifying nucleation sites and performing kinetic simulations from a molecular perspective. These analyses indicated that lower temperatures are favor the control of oiling-out phenomena. The nucleation of iohexol is characterized by a two-step mechanism, initiating with liquid–liquid separation, followed by nucleation and crystal growth. Solubility parameters, derived using Materials Studio, suggest enhanced interactions between iohexol and methanol, which is also corroborated by the solvation energy data from Gaussian software. This interaction explains the tendency of iohexol to oiling out in mixed solvents. Radial distribution function (RDF) analysis illustrates that methanol-iohexol interactions intensify prior to oiling-out, reach a peak during oiling-out, and diminish after nucleation due to desolvation. The occurrence of oiling-out can lead to challenges such as diminished product quality, reduced yields, and difficulties in reprocessing. Therefore, understanding the mechanism of oiling-out is fundamental to addressing these issues, rendering these insights invaluable for the study of crystallization processes and oiling out phenomena in other small organic molecules.

Solubility and thermodynamics of mesalazine in aqueous mixtures of poly ethylene glycol 200/600 at 293.2–313.2 K

In this study, the solubility of mesalazine was investigated in binary solvent mixtures of poly ethylene glycols 200/600 and water at temperatures ranging from 293.2K to 313.2K. The solubility of mesalazine was determined using a shake-flask method, and its concentrations were measured using a UV-Vis spectrophotometer. The obtained solubility data were analyzed using mathematical models including the van't Hoff, Jouyban-Acree, Jouyban-Acree-van't Hoff, mixture response surface, and modified Wilson models. The experimental data obtained for mesalazine dissolution encompassed various thermodynamic properties, including ΔG°, ΔH°, ΔS°, and TΔS°. These properties offer valuable insights into the energetic aspects of the dissolution process and were calculated based on the van't Hoff equation.

2024 Franzosini Prize and Balarew Award—Call for Nominations

Abstract In 1989 the Subcommittee on Solubility Equilibrium Data (SSED) inaugurated the Franzosini Award to assist a promising young contributor to the Solubility Data Project. In 2023 the Franzosini Award was renamed the Franzosini Prize and elevated to an award in recognition of outstanding and sustained contributions to the field of critical evaluation of data in solubility and related chemical equilibria. At the same time the Balarew Award was inaugurated to recognize an Outstanding Young Scientist working in the field of critical evaluation of solubility and/or related chemical equilibria.

Determination of Regorafenib monohydrate (colorectal anticancer drug) solubility in supercritical CO2: Experimental and thermodynamic modeling

In this study, the solubilities of Regorafenib monohydrate (REG), a widely used as a colorectal anticancer drug, in supercritical carbon dioxide (ScCO2) were measured under various pressures and temperature conditions, for the first time. The minimum value of REG in mole fraction was determined to be 3.06×10−7, while the maximum value was found to be 6.44×10−6 at 338 K and 27 MPa. The experimental data for REG were correlated through the utilization of two types of models: (1) a set of 25 existing empirical and semi-empirical models that incorporated 3–8 parameters according to functional dependencies, (2) a model that relied on solid-liquid equilibrium (SLE) and the newly improved association models. All of the evaluated models were capable of generating suitable fits to the solubility data of REG, however, the average absolute relative deviation (AARD) of Gordillo et al. model (AARD=13.2%) and Reddy et al. model (AARD=13.5%) indicated their superiority based on AARD%. Furthermore, solvation and sublimation enthalpies of REG drug were estimated for the first time.

Solubility, Thermodynamic Parameters, and Dissolution Properties of 17-α Hydroxyprogesterone in 13 Pure Solvents.

The static gravimetric method was used to measure the solubility of 17-α hydroxyprogesterone (OHP) in 13 pure solvents ranging from 278.15 to 323.15 K. The results indicate that the experimental solubility of OHP increases with increasing temperature. The experimental solubility data were correlated by the selected van't Hoff model, λh model, modified Apelblat model, Yaws model, and nonrandom two-liquid (NRTL) model. The fitting results show that the Yaws model can give better correlation results by fitting 13 different pure solvent systems. Based on the NRTL equation, the thermodynamic analysis of solubility data showed that the mixing process was spontaneous. The Hansen solubility parameters (HSPs) and solvent effect were applied to explore these solubility characteristics. Finally, the thermodynamic properties ΔsolH°, ΔsolS°, ΔsolG°, %ξH, and %ξTS were calculated by the van't Hoff model equation. The results showed that ΔsolH°, ΔsolS°, and ΔsolG° are all positive values, indicating that the dissolution of OHP in the selected solvent is an endothermic reaction with increasing entropy.