Solubility of β-diketonate complexes for cobalt(III) and chromium(III) in supercritical carbon dioxide

The solubilities of tris(2,2,6,6-tetramethyl-3,5-heptanedionate) cobalt(III) (Co(thd)₃) and chromium(III) (Cr(thd)₃) in supercritical carbon dioxide (scCO₂) were measured at temperatures ranging from 313 to 343 K. The measurements were carried out using a circulation-type apparatus with a UV–vis spectrometer. The solubilities of both Co(thd)₃ and Cr(thd)₃ increased as both the density of scCO₂ and the temperature increased, which has the same tendency as cobalt(III) acetylacetonate (Co(acac)₃) and chromium(III) acetylacetonate (Cr(acac)₃) had in our previous work. The solubilities of Cr(thd)₃ were higher than that of Co(thd)₃, and the solubilities of Co(thd)₃ and Cr(thd)₃ were about 50- and 70-fold higher than those of Co(acac)₃ and Cr(acac)₃, respectively. The measured solubilities of the metal complexes were correlated with the equation based on Chrastil's equation. The parameters were determined by correlating the experimental data for each metal complex, and the correlated results well reproduced the experimental data, especially Co(thd)₃. Moreover, the charge density distributions on the molecular surface of CO₂ and the metal complexes used in the measurement were estimated by the quantum chemical calculation and the COSMO-RS to clear the effect of the molecular structure of the metal complexes on the affinity for CO₂.     

Structure–Solubility Relationship of 1,4-Dioxane Complexes of Di(hydrocarbyl)magnesium

Systematic variation of the 1,4-dioxane (dx) concentration during the precipitation of sparingly soluble [MgBr₂(dx)₂] from ethereal Grignard solutions of RMgBr has allowed the structural investigation of crystallized [R₂Mg(dx)_n] (n=1, 1.5, 2, and 3), which form during this dioxane method, depending on the bulkiness of R. The numbering of the complexes explored in this study is based on the number n of dioxane molecules per magnesium atom, followed by the substituent R; an apostrophe denotes coordination polymers. The following derivatives were studied by X-ray crystal-structure determination and NMR spectroscopy: n=1: [Me₂Mg(μ-dx)]_∞ ( 1′-Me ) and [nPr₂Mg(μ-dx)]_∞ ( 1′-nPr ); n=1.5: [{iPr₂Mg(dx)}₂(μ-dx)] ( 1.5-iPr ), [{oTol₂Mg(dx)}₂(μ-dx)] ( 1.5-oTol ), and [(Me₃Si-C≡C)₂Mg(dx)_1.5]_∞ ( 1.5′-C₂SiMe₃ ); n=2: [tBu₂Mg(dx)₂] ( 2-tBu ) and [oTol₂Mg(dx)₂] ( 2-oTol ); n=3: [Ph₂Mg(dx)₃] ( 3-Ph ). In the structure types 1′ , 1.5 , and 2 , the magnesium atom exhibits the coordination number 4, whereas pentacoordinate metal atoms are observed in types 3 and 1.5′ . The structure type 2′ is realized for [(Ph-C≡C)₂Mg(dx)₂]_∞ ( 2′-C₂Ph ), [MgCl₂(dx)₂]_∞ ( 2′-Cl ), and [MgBr₂(dx)₂]_∞ ( 2′-Br ) with hexacoordinate metal atoms. The solubility of the dioxane adducts in common organic solvents strongly depends on the degree of aggregation with the solubility decreasing from molecular to strand to layer structures.     

Thermodynamics (Solubility and Protonation Constants) of Risedronic Acid in Different Media and Temperatures (283.15–318.15 K)

Potentiometric measurements were carried out to study the protonation constants of risedronic acid (RA) in NaCl_(aq), (CH₃)₄NCl_(aq) and (C₂H₅)₄NI_(aq) at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15). In the same conditions, solubility measurements were also performed. Calorimetric measurements were done in NaCl to determine the protonation enthalpy values at I = 0.15 mol·dm^?3 and 298.15 K. Generally, the proton binding process was endothermic and the driving force was entropic in nature. The values of the protonation constants determined in NaCl_(aq) are lower than those obtained in the two tetraalkylammonium salts. The medium effect was interpreted using different thermodynamic models in terms of variation of the activity coefficients with ionic strength (Debye–Hückel type and SIT), or formation of weak complexes between risedronate (Ris^4?) and the ions of the supporting electrolytes. Specific interaction coefficients (ε) and the stability of five (CH₃)₄N⁺/Ris^4? (at different temperatures and ionic strengths) species are reported. The total solubility of risedronic acid is higher in NaCl_(aq) than in the other two ionic media and, in all cases, increases with increasing temperature. Setschenow and activity coefficients of the neutral species were also computed in all ionic media.     

Solubility of naphthalene in aqueous solutions of poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) triblock copolymers and (2-hydroxypropyl)cyclodextrins

The solubility of naphthalene was investigated in aqueous solutions of triblock copolymers poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PEG–PPG–PEG) and (2-hydroxypropyl)cyclodextrins. The results with solutions of the individual solubilizers were as expected: the solubility enhancement was much higher with a micelle-forming copolymer than with the non-micellizing one and with (2-hydroxypropyl)--cyclodextrin (HPBCD) than with (2-hydroxypropyl)--cyclodextrin (HPACD). Although the formation of inclusion complexes between HPACD and PEG and between HPBCD and PPG is well established, the naphthalene solubility in mixed solutions does not significantly deviate from that predicted for a mixture of independent solubilizers. Thus the interactions between HPCD and PEG–PPG–PEG copolymers are not strong enough to disrupt micelles and aggregates formed by those copolymers. In fact, slight synergetic deviations were observed with the micellizing copolymer, indicating the existence of ternary naphthalene/HPCD/copolymer interactions. For pharmaceutical applications, it is important that the solubilization efficacy of PEG–PPG–PEG copolymers and that of cyclodextrins modified by the 2-hydroxypropyl group would not be compromised if these two types of solubilizers were co-administered.     

Thermodynamic Model for the Solubility of Cr(OH)3(am) in Concentrated NaOH and NaOH–NaNO3 Solutions

The main objective of this study was to develop a thermodynamic model for predicting Cr(III) behavior in concentrated NaOH and in mixed NaOH–NaNO₃ solutions for application to developing effective caustic leaching strategies for high-level nuclear waste sludges. To meet this objective, the solubility of Cr(OH)₃(am) was measured in 0.003 to 10.5 m NaOH, 3.0 m NaOH with NaNO₃ varying from 0.1 to 7.5 m, and 4.6 m NaNO₃ with NaOH varying from 0.1 to 3.5 m at room temperature (22 ± 2°C). A combination of techniques, X-ray absorption spectroscopy (XAS) and absorptive stripping voltammetry analyses, were used to determine the oxidation state and nature of aqueous Cr. A thermodynamic model, based on the Pitzer equations, was developed from the solubility measurements to account for dramatic increases in aqueous Cr with increases in NaOH concentration. The model includes only two aqueous Cr species, Cr(OH) ₄ ^– and Cr₂O₂(OH) ₄ ^– (although the possible presence of a small percentage of higher oligomers at >5.0 m NaOH cannot be discounted) and their ion–interaction parameters with Na⁺. The logarithms of the equilibrium constants for the reactions involving Cr(OH) ₄ ^– [Cr(OH)₃(am) + OH^– Cr(OH) ₄ ^– ] and Cr₂O₂(OH) ₄ ^2– [2Cr(OH)₃(am) + 2OH^– Cr₂O₂(OH) ₄ ^2– + 2H₂O] were determined to be –4.36 ± 0.24 and –5.24 ± 0.24, respectively. This model was further tested and provided close agreement between the observed Cr concentrations in equilibrium with Cr(OH)₃(am) in mixed NaOH–NaNO₃ solutions and with high-level tank sludges leached with and primarily containing NaOH as the major electrolyte.     

Solubility of the Copper(II) Salt–Sodium Formate–Water Systems at 25°C

Solubilities in the CuSO₄ (CuCl₂, Cu(NO₃)₂)–NaHCOO–H₂O systems are studied at 25°C using the isothermal sections method. Crystallization regions of copper(II) formate mono- and dihydrate are elucidated. It is proved that copper(II) formate can be synthesized in CuAn₂ + 2NaHCOO ? Cu(HCOO)₂ + 2NaAn–H₂O quaternary reciprocal systems using the conversion method.     

Solubility in the ZnCl2-CO(NH2)2-HCl-H2O system at 25°C

The ZnCl₂-CO(NH₂)₂-HCl-H₂O quaternary system at 25°C was studied by the solubility method. The concentration boundaries of crystallization were established for the phases that correspond to the eutonic compositions of ternary systems, for double carbamide compounds with zinc chloride and hydrochloric acid, and for the compound ZnCl₂ · 2CO(NH₂)₂ · HCl.     

Solubility characteristics ofβ-cyclodextrin inclusion complexes

Some inclusion complexes of-cyclodextrin (cyclomaltoheptaose) have been investigated, particularly with respect to their solubility. The mathematical characterization of the equilibrated host-guest system containing both solid and solution phases is discussed (first of all those, which contain 1:1 or 1:1 + 2:1 species) and demonstrated by different examples.     

4-(Methylsulfonyl)benzaldehyde Solubility in Binary Solvent Mixtures of Acetonitrile + (Methanol,Ethanol and Isopropanol): Determination and Modelling

The solubilities of 4-(methylsulfonyl)benzaldehyde in the binary mixed solvents acetonitrile + methanol, acetonitrile + ethanol and acetonitrile + isopropanol were determined experimentally using an isothermal dissolution equilibrium method within the temperature range from 283.15 to 318.15 K under atmospheric pressure. The solubility of 4-(methylsulfonyl)benzaldehyde increased with increasing temperature and mass fraction of acetonitrile in each binary system. At the same temperature and mass fraction of acetonitrile, the mole fraction solubility of 4-(methylsulfonyl)benzaldehyde is greater in (acetonitrile + methanol) than in the other two mixed solvents. The solubility data were correlated using the CNIBS/R-K model, Jouyban–Acree model, van’t Hoff–Jouyban–Acree model, Apelblat–Jouyban–Acree model, Ma model and Sun model. The maximum values of relative average deviation (RAD) and root-mean-square deviation (RMSD) are 1.53% and 1.17 × 10^?4, respectively. All of the selected models provided good representation of the experimental solubilities. Furthermore, the standard enthalpies of dissolution were calculated. The dissolution process for 4-(methylsulfonyl)benzaldehyde in these mixed solvents is endothermic. The experimental solubility and the models presented in this work are important for the production and purification of 4-(methylsulfonyl)benzaldehyde.     

Thermodynamic Model for ThO<Subscript>2</Subscript>(am) Solubility in Isosaccharinate Solutions

Extensive studies on ThO₂(am) solubility were carried out as functions of a wide range of isosaccharinate concentrations (0.0002 to 0.2 mol⋅kg⁻¹) at fixed pH values of about 6 and 12, and varying pH (ranging from 4.5 to 12) at fixed aqueous isosaccharinate concentrations of 0.008 mol⋅kg⁻¹ or 0.08 mol⋅kg⁻¹, to determine the aqueous complexes of isosaccharinate with Th(IV). The samples were equilibrated over periods ranging up to 69 days, and the data showed that, in most cases, steady-state concentrations were reached in <15 days. The data were interpreted using the SIT model, and required the inclusion of mixed hydroxy-ISA complexes of Th(IV) [Th(OH)ISA²⁺, Th(OH)₃(ISA)₂^-_{2}^{-}, and Th(OH)₄(ISA)₂^2-]_{2}^{2-}] with log ₁₀ K ⁰=12.5±0.5,4.4±0.5 and −3.2±0.5 for the reactions:

Effect of Lead(II) Complexation on Solubility of β-PbO in Alkaline Solutions in the Presence of Certain Alcohols

Complex formation of lead(II) was studied, and the solubility of -PbO was determined by potentiometric titration in solutions containing sodium hydroxide (0.3-4 M) and a series of mono- and polyhydric alcohols. A correlation between the lead monoxide solubility and Pb(II) complex formation function was considered.     

Solubility of water in polymers—atomistic simulations

The combination of the thermodynamic-integration approach and Widom's particle-insertion method is shown to be appropriate to determine the excess chemical potential of water in dense, amorphous polymer microstructures from MD simulation at an atomistically detailed level. The two-step method is applied to bisphenol-A–polycarbonate (BPA–PC) and polyvinylalcohol (PVA). The results are compared to previously published calculations on water sorption of various polyamides and show the applicability of the two-step method for the calculation of the excess chemical potential of water in a variety of polymer materials to obtain an estimate of their water sorption behavior.     

Changes in the Solubility of β-Cyclodextrin on Complex Formation: Guest Enforced Solubility of β-Cyclodextrin Inclusion Complexes

The most common native host molecule, -cyclodextrin (cycloheptaamylose) is able toform inclusion complexes with a large variety of guestmolecules (or ions) of different size and shape. Theproperties of the included guest molecule are highlyinfluenced by the host-guest interaction, and thepractical usefulness of -cyclodextrin isdependent on these effects. These changes are mainlyinvestigated from the point of view of the guest andto a lesser extent from that of the host. In spite ofthis, the kind of guests and that of the host-guestinteractions during the formation of the inclusioncomplex seem to influence the properties of thehydrophilic domain of -cyclodextrin (i.e. thatof the supramolecule itself), too, and this effect canbe well demonstrated by the change of solubility ofdifferent -cyclodextrin inclusion complexes.This change can be best correlated with the solubilityof the guest as if the guest enforced its solubilityon the supramolecule.     

Thermodynamic Model for ThO<Subscript>2</Subscript>(am) Solubility in Alkaline Silica Solutions

No thermodynamic data for Th complexes with aqueous Si are available. To obtain such data, extensive studies on ThO₂(am) solubility were carried out as functions of: (1) a wide range of aqueous silica concentrations (0.0004 to 0.14 mol⋅L⁻¹) at fixed pH values of about 10, 11, 12, and 13; and (2) and variable pH (ranging from 10 to 13.3) at fixed aqueous Si concentrations of about 0.006 mol⋅L⁻¹ or 0.018 mol⋅L⁻¹. The samples were equilibrated over long periods (ranging up to 487 days), and the data showed that steady-state concentrations were reached in < 29 days. X-ray diffraction, FTIR, and Raman analyses of the equilibrated solid phases showed that the Th solids were amorphous ThO₂(am) containing some adsorbed Si. The solubility of ThO₂(am) at pH values ranging from 10 to 13.3 at fixed 0.018 mol⋅L⁻¹ aqueous Si concentrations decreases rapidly with an increase in pH, and increases dramatically with an increase in Si concentrations beyond about 0.003 mol⋅L⁻¹ at fixed pH values > 10. The data were interpreted using both the Pitzer and SIT models, and required only the inclusion of one mixed-hydroxy-silica complex of Th [Th(OH)₃(H₃SiO₄)₃²⁻]. Both models provided similar complexation constant values for the formation of this species. Density functional theory calculations predict complexes of this stoichiometry, having six-fold coordination of the Th cation, to be structurally stable. Predictions based on the fitted value of log ₁₀ K ⁰=−18.5±0.7 for the ThO₂(am) solubility reaction involving Th(OH)₃(H₃SiO₄)₃²⁻[ThO₂(am)+3H₄SiO₄+H₂O↔Th(OH)₃(H₃SiO₄)₃²⁻+2H⁺], along with the thermodynamic data for aqueous Si species reported in the literature, agreed closely with the extensive experimental data and showed that under alkaline conditions aqueous Si makes very strong complexes with Th.     

Aqueous Long-Term Solubility of Titania Nanoparticles and Titanium(IV) Hydrolysis in a Sodium Chloride System Studied by Adsorptive Stripping Voltammetry

The solubility of industrially produced titanium dioxide nanoparticles has been studied in aqueous sodium chloride media in the pH range 1 to 13 at 25 °C by using adsorptive stripping voltammetry (AdSV). Kinetic dissolution curves have been obtained as well as long-term solubilities that provide an approximation of the equilibrium solubilities. The titania nanoparticles used in the dissolution experiments have been characterized by nitrogen sorption measurements, XRD and colloid titration. The equilibrium solubilities and titanium(IV) speciation and their dependences on pH have been modelled by assuming the formation of the mononuclear titanium hydroxo complexes [Ti(OH) _n ]⁽⁴⁻ⁿ⁾⁺ (n=2 to 5) to be the only titanium species present. The solubility product of titanium dioxide and equilibrium constants for titanium(IV) hydrolysis, calculated from the AdSV solubility data, are presented.     

The Applicaton of IAF Theory to the Study of Dissociation Equilibrium (Ⅱ) --The Calculation of Solubility Product Constant in Nonaqueous Solvents

This article reports a theoretical calculation of solubility product constant of several slightly soluble silver salts in a number of nonaqueous solvents according to the IAF (interaction force) theory based on the interaction free energy of electrostatic, orientation, induction and dispersion. The calculated values of pKsp are in good accordance with those from literature.     

Solubility measurement of α-asarone in supercritical carbon dioxide

The solubility of α-asarone in supercritical CO₂ (sc-CO₂) has been measured using the dynamic method. The measurement was conducted in the pressure range from 9.0 to 18.0 MPa at temperature 35–49 °C. The experimental data were correlated using the Chrastil model. The results show that the solubility increases as the pressure rises and decreases as the temperature rises, which is well correlated with the Chrastil model.     

Solubility in the magnesium chlorate-carbamide-water system at 50°C

The solubility of phases in the magnesium chlorate-carbamide-water system was studied by the isothermal solubility method at 50°C. The crystallization branches of carbamide, magnesium chlorate hexahydrate, Mg(ClO₃)₂ · 6CO(NH₂)₂, Mg(ClO₃)₂ · 4CO(NH₂)₂ · 2H₂O, and Mg(ClO₃)₂ · 2CO(NH₂)₂ · 4H₂O were revealed in the phase diagram.