Standard Enthalpies Of Solution Research Articles

Equilibria of the ternary systems CsBr–LnBr3 (Ln = Gd, Dy)–H2O and the quaternary system CsBr–GdBr3–HBr (∼12.1 mass %)–H2O at T = 298.15 K and standard molar enthalpies of formation for new compounds

As part of a series of studies, this paper reports experimental phase equilibrium data for CsBr–GdBr3–H2O, CsBr–DyBr3–H2O and CsBr–GdBr3–HBr (∼12.1 mass %)–H2O systems at T = 298.15 K. The phase diagrams were constructed based on the measured data. In the phase diagrams of the ternary system CsBr–GdBr3–H2O and the quaternary system CsBr–GdBr3–HBr (∼12.1 mass %)–H2O,there are all two invariant points, and three crystallization regions corresponding to CsBr, Cs3GdBr6·10H2O, and GdBr3·6H2O, respectively.There are two invariant points and three crystallization regions corresponding to CsBr, Cs3Dy2Br9·16H2O and DyBr3·6H2Oin the system CsBr–DyBr3–H2O.The experimental solubility values of gadolinium bromide and dysprosium bromide at 298.15 K were 65.42 mass % and 65.94 mass %. The compounds Cs3GdBr6·10H2O and Cs3Dy2Br9·16H2O are incongruently soluble in water or a medium of ∼ 12.1 mass % HBr, and were characterized by XRD and TG-DTG techniques. The standard molar enthalpies of solution for Cs3GdBr6·10H2O, Cs3Dy2Br9·16H2O, GdBr3·nH2O (n = 6.00) and DyBr3·nH2O (n = 5.99) were obtainedby means of microcalorimetric measurement, the values found for standard molar enthalpies of formation of Cs3GdBr6·10H2O, Cs3Dy2Br9·16H2O, GdBr3·nH2O (n = 6.00) and DyBr3·nH2O (n = 5.99) were – (5104.8 ± 3.2) kJ·mol−1, – (7827.3 ± 3.6) kJ·mol−1, – (2726.0 ± 2.7) kJ·mol−1 and – (2734.5 ± 3.3) kJ·mol−1, respectively.

Energetics of dehydroepiandrosterone polymorphs I and II from solution and drop-sublimation Calvet microcalorimetry measurements

The lattice enthalpies and monotropic relationship of two dehydroepiandrosterone (DEHA) polymorphs (forms I and II) were evaluated through a combination of differential scanning calorimetry (DSC), isothermal solution microcalorimetry, and drop-sublimation Calvet microcalorimetry experiments. The standard molar enthalpy of transition between both forms was determined as ΔtrsHmo(II→I, 298.15 K) = −0.90 ± 0.07 kJ mol−1 and ΔtrsHmo(II→I, 417.8 K) = −1.7 ± 1.0 kJ mol−1, from measurements of standard molar enthalpies of solution in dimethyl sulfoxide and enthalpies of fusion, respectively. Drop-sublimation Calvet microcalorimetry experiments on form I led to ΔsubHmo(cr I, 298.15 K) = 132.0±3.3 kJ mol−1. This result, when combined with the more precise ΔtrsHmo(II→I) value obtained by solution calorimetry, afforded ΔsubHmo(cr II, 298.15 K) = 131.1±3.3 kJ mol−1. The overall data indicate that on enthalpic grounds form I is more stable than form II from 298.15 K up to fusion. This conclusion, and the fact that DSC experiments indicated that form I has also a considerably higher temperature fusion, namely, Tfus(cr I)= 422.5±0.2 K and Tfus(cr II) = 413.1±0.2 K, suggest that the two polymorphs are monotropically related.

Composition of the Solvation Shell of the Selected Cyclic Ethers (1,4-Dioxane, 12-Crown-4, 15-Crown-5 and 18-Crown-6) in a Mixture of Formamide with Water at Four Temperatures

The solution enthalpy of 15-crown-5 and 18-crown-6 ethers in the mixture of formamide (F) and water (W) was measured at four temperatures: 293.15 K, 298.15 K, 303.15 K, 308.15 K. The standard molar enthalpy of solution, ΔsolHo, depends on the size of cyclic ethers molecules and the temperature. With increasing temperature, the values of ΔsolHo become less negative. The values of the standard partial molar heat capacity Cp,2o of cyclic ethers at 298.15 K have been calculated. The Cp,2o=f(xW) curve shape indicates the hydrophobic hydration process of cyclic ethers in the range of a high-water content in the mixture with formamide. The enthalpic effect of preferential solvation of cyclic ethers was calculated and the effect of temperature on the preferential solvation process was discussed. The process of complex formation between 18C6 molecules and formamide molecules is observed. The cyclic ethers molecules are preferentially solvated by formamide molecules. The mole fraction of formamide in the solvation sphere of cyclic ethers has been calculated.

Solubility Phase Diagrams of ternary systems of CsCl–CdCl2–H2O and CsBr–CdBr2–H2O at T = 298.1 K and the thermodynamic properties of the new solid phase compounds

Using an isothermal equilibrium method, thephaseequilibrium of the ternary systems CsCl–CdCl2–H2O and CsBr–CdBr2–H2O were studied at T = 298.1 K. In thephasediagram of the system CsCl–CdCl2–H2O, the solidphasesof CsCdCl3 and Cs2CdCl4, besides CsCl and CdCl2·2.5H2O, were discovered. Thephasediagramof the system CsBr–CdBr2–H2O contains five crystallization fields for the solidphases CdBr2·4H2O, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 and CsBr. The new solidphasesof CsCdCl3 and CsCdBr3 are congruently soluble, and Cs2CdCl4, Cs5Cd2Br9 and Cs3CdBr5 are incongruently soluble in the aqueous system. The experimental solubility data and phase diagrams for the ternary systems show more practical application for the obtained cadmium-based halide perovskite. The five new solid phase have been analyzed by X-ray diffraction and thermogravimetry/derivative thermogravimetry. By measuring the standard molar enthalpies of solution of the compounds, the standard molar enthalpies of formation of CsCdCl3, Cs2CdCl4, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 were determined to be –(873.3 ± 0.7) kJ·mol−1, –(1325.6 ± 0.9) kJ·mol−1, –(742.8 ± 0.7) kJ·mol−1, –(2710.0 ± 1.3) kJ·mol−1 and –(1558.1 ± 1.0) kJ·mol−1, respectively.

Additive scheme of solvation enthalpy for halogenated aliphatic hydrocarbons at 298.15 K.

In this work, an additive scheme for the estimation of solvation enthalpy of halogenated aliphatic hydrocarbons in n-heptane was developed. The proposed structural fragments for halogen group contributions are dependent on the nature of neighbouring atoms. A linear relationship between solvation and vaporization enthalpy at 298.15 K for mono- and di-α,ω-halogen aliphatic compounds was found. These relationships can be used for the quick estimation of standard vaporization and solution enthalpies at 298.15 K. Proposed approaches for estimation of solvation, solution and vaporization enthalpies at 298.15 K were verified by conventional methods. In most cases, absolute deviations between experimental and estimated values for halogenated aliphatic hydrocarbons do not exceed 1-2 kJ mol−1.

Solid–liquid equilibria in the systems cesium bromide + holmium bromide + water and cesium bromide + holmium bromide + hydrobromic acid (~11.7 mass %) + water at T = 298.15 K

The (Solid–Liquid) phase equilibria for the systems of cesium bromide + holmium bromide + water and cesium bromide + holmium bromide + hydrobromic acid (~11.7 mass %) + water at T = 298.15 K were researched by the isothermal dissolution equilibrium method. According to the experimental data, the phase diagrams of the two systems were depicted. There were two invariant points, three invariant curves, and three crystallization fields (CsBr, Cs3Ho2Br9·16H2O, HoBr3·8H2O) in the two phase diagrams. Cs3Ho2Br9·16H2O was incongruently soluble in the two systems. The solubility of HoBr3 measured in water at T = 298.15 K is 65.41 mass %. The compound Cs3Ho2Br9·16H2O was investigated using chemical analysis, XRD and TG-DTG analysis. The standard molar enthalpy of solution of Cs3Ho2Br9·16H2O in water was measured to be −(5.54 ± 0.28) kJ/mol by a microcalorimetry, and its standard molar enthalpy of formation was determined as being –(7846.5 ± 1.2) kJ/mol.

Construction and performance evaluation of a CSC-1 type horizontal rotating micro-bomb combustion-solution isoperibol multifunctional calorimeter

In this work, a CSC-1 type horizontal rotating micro-bomb combustion-solution isoperibol multifunctional calorimeter was constructed. There are three main differences between the structure of this calorimeter and the existing calorimeters: (1) two functions, i.e. the measurements of combustion heat and solution heat were integrated together; (2) Dewar bottle was used as a shared calorimetric container for the determination of combustion heat and solution heat; (3) submersible magnetic mixer replaced the traditional mechanical rod mixer. The energy equivalent of combustion system in the calorimeter was calibrated with NIST SRM 39j benzoic acid, giving the result of (1181.94 ± 0.23) J⋅K−1. Furthermore, the standard specific energy of combustion of salicylic acid was measured using the combustion system, and the result showed that the standard specific energy of combustion of salicylic acid was – (21884.9 ± 5.4) J·g−1 at 298.15 K. Then, the standard molar enthalpy of formation of salicylic acid was calculated to be ΔfHmo[C7H6O3(s),298.15K]=-(589.27±2.98)kJ⋅mol−1. In addition, the energy equivalent of solution system in the calorimeter was calibrated with electrical energy, giving the result of (5.28084 ± 0.00261) J·mV−1. And the standard specific enthalpy of solution of KCl was measured by the solution system in water at 298.15 K, the results indicated that the standard specific and molar enthalpy of solution of KCl (1100 H2O, 298.15 K) were (235.33 ± 0.03) J·g−l and (17543.2 ± 8.9) J·mol−l, respectively. All these results demonstrated that the calorimetric systems of combustion and solution in the developed calorimeter are reliable and feasible.

Standard molar enthalpy of the orthorhombic to monoclinic polymorphic phase transition in 4′-hydroxyacetophenone from enthalpy of solution measurements

The standard molar enthalpy of transition between the two known polymorphs of 4′-hydroxyacetophenone (HAP), at 298.15 K, was determined from measurements of their standard molar enthalpies of solution in dimethyl sulfoxide (DMSO). The obtained result ΔtrsHmo(cr II→cr I) = (0.48 ± 0.10) kJ.mol−1 is in excellent agreement with a previously reported value measured in ethanol with an isoperibol calorimeter, using ~ 7 times larger amounts of sample and solvent. The fact that the two polymorphs are easily prepared, and such good agreement was observed between results from two considerably different calorimetric techniques and solvents, suggests that HAP may be a convenient benchmark system for the validation of solution calorimetry measurements or force field predictions on the relative enthalpic stability of organic polymorphs.

Thermodynamics of transfer and partition of 3,5-diamino-1-phenyl-1,2,4-triazole in the 1-octanol/water biphasic system

In this paper, we focus for the first time on thermodynamics of transfer of 3,5-diamino-1-phenyl-1,2,4-triazole (DAPT) from water to liquid 1-octanol which is considered in pharmaceutical chemistry as an appropriate model of a lipid-like environment for studying a passive membrane transport of various drugs. The enthalpies of solution of DAPT have been determined calorimetrically in both solvents at 298.15, 308.15 and 328.15 K. The partition coefficients (P) have been obtained in the 1-octanol/water biphasic system at 298.15 and 328.15 K using a classical isothermic saturation method. Standard thermodynamic functions of DAPT transfer from water to a lipid-like phase have been calculated via the Gibbs–Helmholtz equation using the temperature dependence of the standard enthalpies of solution and the partition coefficient at the reference temperature of 298.15 K. We have found that the enthalpic term favours the solute transfer both at lower and elevated temperatures, whereas the entropic one contributes in the opposite manner. The free energy of transfer remains negative for all the temperature range studied indicating rather appreciable affinity of a potential drug towards a lipid-like environment. The comparison of the experimental and calculated P values indicates that our approach is able to predict with a good accuracy the behaviour of the 1,2,4-triazole derivatives for the physiological temperature range.

Phase equilibria in Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3 (∼20%)–H2O systems at 298.15 K and thermodynamic properties of Mg3Ln2(NO3)12·24H2O (Ln = Nd, Sm)

The phase diagrams of the Mg(NO3)2–Ln(NO3)3 (Ln = Nd, Sm, Eu, Tb)–HNO3–H2O systems in the (∼20%) HNO3 regions at T = 298.15 K were determined by using an isothermal solution saturation method. The Schreinemaker’s wet residues method was used to determine the compositions of solid-phases. Both Mg(NO3)2–Nd(NO3)3–HNO3–H2O and Mg(NO3)2–Sm(NO3)3–HNO3–H2O systems are complicated with three equilibrium solid phases Mg(NO3)2·6H2O, Mg3Ln2(NO3)12·24H2O and Ln(NO3)3·6H2O (Ln = Nd, Sm). But the systems Mg(NO3)2–Eu(NO3)3–HNO3–H2O and Mg(NO3)2–Tb(NO3)3Tb–HNO3–H2O are simple eutonic type. The two new solid-phase compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O are congruently soluble in an average medium of ∼20 mass % HNO3, and they were identified and characterized by the methods of powder X-ray diffraction, X–ray diffraction single crystal structure analysis, and thermogravimetric/differential thermogravimetric. The XRD diffraction patterns for the two new solid-phase compounds are identical due to their isomorphic structure. They belong to hexagonal systems, with space group R3. For Mg3Nd2(NO3)12·24H2O, a = b = (1.0993 ± 0.0005) nm, c = (1.7211 ± 0.0007) nm, V = (1.8012 ± 0.0013) nm3, Dc = (4.2532 ± 0.0024) g·cm−3, Z = 3; for Mg3Sm2(NO3)12·24H2O, (a = b = 1.1198 ± 0.0004) nm, c = (1.7257 ± 0.0006) nm, V = (1.8742 ± 0.0011) nm3, Dc = (4.1201 ± 0.0012) g cm−3, Z = 3. The standard molar enthalpies of solution of the compounds Mg3Nd2(NO3)12·24H2O and Mg3Sm2(NO3)12·24H2O in water (aq) were measured to be (101.26 ± 0.77) kJ mol−1 and (80.27 ± 0.81) kJ mol−1, and their standard molar enthalpies of formation were calculated to be – (12214.13 ± 2.5) kJ mol−1 and – (12183.6 ± 2.5) kJ mol−1, respectively.

Similarity and differences of the thermochemical characteristics of l-glutamine dissolution in aqueous solutions of some acetamides and formamides at T = 298.15 K

The enthalpies of l-glutamine dissolution in an aqueous solution of acetamide, N-methylacetamide, and N, N-dimethylacetamide were determined by the calorimetric method at T = 298.15 K and organic solvent mole fractions up to x2 ~ 0.25. The standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of l-glutamine from water to a mixed solvent as well as the enthalpy coefficients of pairwise interactions (hxy) were calculated. The interrelation between enthalpic characteristics of l-glutamine dissolution (transfer) and the composition of water-organic mixtures was determined. The received thermochemical characteristics of intermolecular interactions of l-glutamine with the molecules of acetamides were compared with the analogous characteristics interactions of l-glutamine with the molecules of formamides (formamide, N-methyformamide, and N, N-dimethylformamide).

Solid-liquid equilibria for the systems of (CsCl + DyCl3 + H2O) and {CsCl + DyCl3 + HCl (∼10.7%) + H2O} at T = 298.15 K and the thermodynamic properties of the new solid compounds

Solid–liquid equilibria in the ternary system (CsCl + DyCl3 + H2O) and the quaternary system {(CsCl + DyCl3 + HCl (∼10.7%) + H2O} at T = 298.15 K and under 101.3 kPa were investigated by the method of isothermal solution saturation, and the corresponding phase diagrams were constructed. It was found that there were three crystallization regions corresponding to CsCl, Cs2DyCl5·6H2O and DyCl3·6H2O in the ternary system. Nevertheless, four crystallization regions corresponding to CsCl, Cs5DyCl8·6H2O, Cs2DyCl5·6H2O and DyCl3·6H2O were found in the quaternary system. The compound Cs2DyCl5·6H2O was congruently soluble in the two systems, and new double salt Cs5DyCl8·6H2O was formed in the quaternary system which was congruently soluble in an average medium of ∼10.7 mass% HCl. The new solid-phase compounds Cs5DyCl8·6H2O and Cs2DyCl5·6H2O were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs5DyCl8·6H2O and Cs2DyCl5·6H2O in water were measured to be (44.28 ± 0.50) kJ·mol−1 and (5.32 ± 0.27) kJ·mol−1 by microcalorimetry in the condition of infinite dilution, and their standard molar enthalpies of formation were determined to be –(5086.9 ± 1.3) kJ·mol−1 and –(3771.6 ± 0.9) kJ·mol−1. As part of this work, five compounds Cs3LaCl6·3H2O, CsLaCl4·4H2O, CsCeCl4·4H2O, CsPrCl4·6H2O and CsNdCl4·9H2O were synthesized according to the literature [18–21]. The molar enthalpies of solution of Cs3LaCl6·3H2O, CsLaCl4·4H2O, CsCeCl4·4H2O, CsPrCl4·6H2O and CsNdCl4·9H2O in water were also measured to be (14.78 ± 0.31) kJ·mol−1, –(30.98 ± 0.62) kJ·mol−1, –(20.26 ± 0.22) kJ·mol−1, –(19.64 ± 0.54) kJ·mol−1 and –(5.86 ± 0.45) kJ·mol−1 in the condition of infinite dilution, and their standard molar enthalpies of formation were calculated to be –(3351.1 ± 1.1) kJ·mol−1, –(2740.3 ± 1.0) kJ·mol−1, –(2746.1 ± 0.7) kJ·mol−1, –(3326.8 ± 0.9) kJ·mol−1 and –(4189.7 ± 0.9) kJ·mol−1, respectively.

The effect of the side chain structures on the energy of intermolecular interactions of α-amino acids with some formamides in aqueous solutions at T = 298.15 K

To evaluate the effect of amino acid side chains on the thermodynamics of their interaction with the formamides molecules in aqueous solutions, we expanded the range of amino acids by studying in the present investigation the thermodynamics of the dissolution of glutamine in mixed solvents {water + (formamide, N‑methylformamide and N,N‑dimethylformamide)} at T = 298.15 K and organic solvent mole fractions up to x2 ~ 0.3. The standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of l-glutamine from water to a mixed solvent as well as the enthalpy coefficients of pairwise interactions (hxy) were calculated. The interrelation between enthalpic characteristics of l-glutamine dissolution (transfer) and the composition of water-organic mixtures was determined. Using the enthalpic coefficients of pairwise interactions of l-glutamine and five more amino acids (glycine, dl-α-alanine, l-valine, l-methionine, and l-threonine), the enthalpic contributions of the side chains of these amino acids to their interparticle interactions with the molecules of formamides were calculated.

Thermodynamic Parameters of the Dissolution of 4-Hydroxy-L-Proline and L-Phenylalanine in Mixed Aqueous Solvents at 298 K

The enthalpies of solution of 4-hydroxy-L-proline and L-phenylalanine in binary mixed aqueous solvents containing acetonitrile (AN), 1,4-dioxane (1,4-DO), or acetone (AC) at mole fractions of 0 to 0.25 are determined at T = 298.15 K via isothermal calorimetry. The standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of 4-hydroxy-L-proline and L-phenylalanine from water to mixed aqueous solvents are calculated using the experimental calorimetric data, as are the enthalpy coefficients of paired interactions (h xy ) between the molecules of the investigated amino acids and the organic solvents. The effects the mixed aqueous solvent composition and the structure of the organic solvent molecules have on the enthalpies of solution and transfer for the investigated amino acids are considered. The correlation between the enthalpy of solution of the amino acids and the electron-donating properties of the organic solvents in the mixed aqueous solvent systems is established.

Remarks on “Measurement and correlation solubility and mixing properties of L-malic acid in pure and mixed organic solvents [Fluid Phase Equilibria 360 (2013) 466–471

Some mathematical errors are identified about the published equation coefficients of Kai and coworkers [Fluid Phase Equilibria 360 (2013) 466–471] for correlating the solubility data of L-malic acid in pure and binary mixtures using the three models. In addition, some other flaws were found regarding their calculation of the standard enthalpy of solution (ΔHsolo) and the standard entropy of solution (ΔSsolo) about L-malic acid dissolved in pure and mixed solvents by the famous van't Hoff equation.

Solubility and thermodynamics of terbinafine hydrochloride in different neat and binary solvents: Measurement, correlation and molecular interactions

The solubility of terbinafine hydrochloride in four pure solvents, including methanol, ethanol, n-propanol and ethyl acetate and their binary solvent mixtures, including (methanol+ethyl acetate), (ethanol+ethyl acetate) and (n-propanol+ethyl acetate) performed at different mass fractions of methanol, ethanol or n-propanol ranging from 0.1 to 0.9, was determined by using isothermal saturation method with temperatures ranging from (278.15 to 313.15) K. The descending order of the mole fraction solubility in pure solvents was as follow: methanol>ethanol>n-propanol>ethyl acetate, and for the three mixture with given initial composition, the solubility of terbinafine hydrochloride increased with increasing temperature and mass fraction of alcohol for the three systems including (methanol+ethyl acetate), (ethanol+ethyl acetate) and (n-propanol+ethyl acetate). At the same mass fraction of methanol, ethanol or n-propanol and temperature, the solubility of terbinafine hydrochloride was greater in (methanol+ethyl acetate) than in the other mixed solvents. The maximum mole fraction solubility of terbinafine hydrochloride was observed in methanol (6.297×10−2 at 313.15K), followed by that in ethanol (3.785×10−2 at 313.15K), n-propanol (3.007×10−2 at 313.15K) and ethyl acetate (1.497×10−2 at 313.15K)·The obtained solubility data were correlated with Jouyban-Acree model, van't Hoff-Jouyban-Acree model, modified Apelblat-Jouyban-Acree model and CNIBS/R-K model. The correlation showed good agreement with experimental results, the largest values of relative average deviations (RAD) and the root-mean-square deviations (RMSD) between the experimental and calculated solubility were 4.32×10−2 and 15.28×10−4, respectively. On the basis of the obtained solubility, the standard enthalpy of solution (ΔHsolo), the standard Gibbs energy (ΔGsolo) of solution and the standard entropy of solution (ΔSsolo) of terbinafine hydrochloride dissolved in pure and mixed solvents were obtained by the famous van't Hoff calculations. Thermodynamic treatment of solubility data of terbinafine hydrochloride in these pure and mixed solvents by “Apparent thermodynamic analysis” indicated that the dissolution is an endothermic and entropy-driven process. The experimental solubility and the models in this study could be helpful in purifying the crude terbinafine hydrochloride.

Thermodynamic characteristics of trans-4-hydroxy-l-proline dissolution in some (water + amide) mixtures at T = 298.15 K

The enthalpies of solution ΔsolHm have been determined for trans-4-hydroxy-l-proline (4-hydroxyproline) in aqueous solutions of formamide (FA), N-methylformamide (MFA), N,N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA). The measurements have been made at 298.15K and mole fraction of amide x2=(0–0.3) on the precise “isoperobol” calorimeter. The results obtained have been used to calculate the standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of 4-hydroxyproline from water into mixtures as well as the enthalpic coefficients of pairwise interaction (hxy) of 4-hydroxyproline with amides in aqueous solution. The interrelation between enthalpy characteristics of dissolution (transfer) of 4-hydroxyproline and the composition of (water+amide) binary mixtures has been established. Contributions of the amides properties (molar volume, dipolarity/polarizability, acidity, and basicity) to the variation of the energy of pairwise interactions have been estimated quantitatively by means of a modified Kamlet-Taft equation.

Effect of properties of the N,N-dimethylformamide–methanol and N,N-dimethylformamide–water mixtures on the solution enthalpy of glymes in these mixtures at 298.15 K

The enthalpies of solutions of diglyme, triglyme, tetraglyme, pentaglyme and hexaglyme in N,N-dimethylformamide–methanol mixtures (DMF+MeOH) have been measured at 298.15K. On the basis of the data obtained, the effect of the acid–base properties of the DMF+MeOH mixtures on the standard solution enthalpy of glymes in these mixtures has been analyzed. The results obtained have been compared with analogous data obtained for N,N-dimethylformamide–water (DMF+W) mixtures.

(Solid + Liquid) Phase Equilibria for the Systems CsBr + EuBr3 + H2O and CsBr + EuBr3 + HBr (∼12.3%) + H2O at 298.15 K and Atmospheric Pressure and Thermodynamic and Fluorescent Properties of the New Solid-Phase Compound

In this study, the (solid + liquid) phase equilibria for the two systems of CsBr + EuBr3 + H2O and CsBr + EuBr3 + HBr (∼12.3%) + H2O at 298.15 K and atmospheric pressure were determined by isothermal solubility method. Schreinemaker wet residue approach was used to determin the solid phases obtained from the studied systems. The related phase diagrams were depicted based upon the experimental data. There were two invariant points, three invariant curves, and three crystallization fields corresponding to CsBr, 5CsBr·2EuBr3·20H2O, and EuBr3·6H2O in the two phase diagrams. New double salt 5CsBr·2EuBr3·20H2O was incongruently soluble in the two systems. The content of EuBr3 in two invariant points decreased as the concentration of HBr in equilibrium liquid phase increased, while that of CsBr changed a little. The new solid-phase compound 5CsBr·2EuBr3·20H2O was investigated using chemical, XRD, and TG-DTG analyses. Additionally, the standard molar enthalpy of solution for 5CsBr·2EuBr3·20H2O in water was confir...

Solubility and selectivity of CO2 in ether-functionalized imidazolium ionic liquids

Ionic liquids are widely recognized new materials in carbon dioxide capture and separation technology. In this work, we synthesized and characterized two kinds of ether-functionalized imidazolium ionic liquids, 1-methoxyethyl-3-methylimidazolium hexafluoroborate ([EOMmim][PF6]) and 1-methoxyethyl-3-methylimidazolium bis(trifluoro-methylsulfony)imide ([EOMmim][Tf2N]). Solubility values of CO2 in these ionic liquids were determined by isometric weight method at the temperatures from 298.15K to 343.15K and the pressure up to 5.185MPa. Furthermore, solubilities of other flue gases, N2 and O2, in these two ionic liquids were also measured at 303.15K. It was shown that little influence had been exerted on CO2 solubility by the introduction of ether groups on the cation, but it decreased N2 and O2 solubility, resulting in the remarkable increase of CO2/N2 and CO2/O2 selectivity. In addition, the solubility data were well correlated by Pitzer model, and the standard state solution Gibbs energy, solution enthalpy and solution entropy of CO2 in the two ionic liquids were reported. Regeneration characteristics of the investigated ionic liquids was also studied by vacuum desorption and atmospheric desorption, respectively.