• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-24
Xiao-Xu Ba, Tian Gao, Mian Yang, Peng Jiang, Feng-Lei Jiang, Yi Liu

Abstract As one of the newly emerged nanomaterials, graphene quantum dots (GQDs) have shown great application potential as tracking probes and drug carriers in biological areas. The GQDs synthesized via the nitric acid reflux method in this study turned out to quench the fluorescence of human serum albumin (HSA) and gamma globulin (γ-globulin) in two different functional ways. The fluorescence quenching effect of GQDs on HSA is a static pattern and the predominant interaction forces are hydrogen bonds and van der Waals forces. Distinct from HSA, the interaction between GQDs and γ-globulins belongs to dynamic quenching and is driven by electrostatic forces. Ultraviolet–visible (UV–vis) differential spectrometry and transient state fluorescence spectrometry were also utilized to further confirm their quenching types. Also, thermodynamics parameters, the enthalpy change (ΔH) and entropy change (ΔS) of reaction between GQDs and proteins were obtained through a series of calculations from the van’t Hoff equation. Furthermore, the effect of GQDs on the conformational structure of proteins was characterized by synchronous fluorescence spectra (SFS), three-dimensional (3D) fluorescence and circular dichroism (CD) spectra. In addition, the binding mechanism of GQDs with HSA and γ-globulins were proposed based on the obtained experimental results. The research on the reaction between GQDs with HSA and γ-globulins offers promising insight for the further application of nanomaterials in biomedical fields.

更新日期：2020-01-26
• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-20
Adam J. Canner, Laurence M. Harwood, Joseph Cowell, Jasraj S. Babra, Solomon F. Brown, Mark D. Ogden

Abstract In this report, the interaction of monoamide/diamide and monoamide/diglycolamide mixtures with $${\text{UO}}_{2}^{2 + }$$ are investigated in pH = 1 methanolic nitric acid media. These monoamides include N,N-dimethylacetamide (DMAA), N,N-diethylacetamide (DEAA), N,N-dibutylacetamide (DBAA) and N,N-dibutylbutanamide (DBBA). N,N,N′N′-tetraethylmalonamide (TEMA) and N,N,N′,N′-tetraethyldiglycolamide (TEDGA), which were chosen as model diamides and diglycolamides, respectively. Complex stability constants for each ligand were modelled using the Stability Quotients Using Absorbance Data program using UV–visible data. Complex stoichiometry of ligand mixtures was determined using Job plots and UV–Vis spectrometry. Monoamides were confirmed to produce only disolvate complexes with $${\text{UO}}_{2}^{2 + }$$ in solution. The log10(K) values for monoamides were found to be independent of amine-side chain length, but were slightly dependent on the carbonyl-side chain length. TEDGA was found to produce multiple uranyl complexes in solution. Job plot data indicated that the uranyl cation strongly prefers to bond either only with the monoamide or diamide in ternary monoamide–diamide–UO2 systems. Monoamide–diglycolamide–UO2 systems were more complicated, with Job plot data indicating the potential for multiple ternary species being present is dependent on the monoamide structure.

更新日期：2020-01-21
• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-17
Yaohui Huang, Xiaowei Sun, Ling Zhou, Zaixiang Zhang, Shihao Zhang, Qiuxiang Yin

The phase diagrams for carbamazepine (CBZ) and nicotinamide (NCT) in ethanol and ethanol/ethyl acetate mixture were constructed at 298.15 K and 313.15 K under atmospheric pressure using the static method. The solubility of the 1:1 cocrystal is correlated as a function of the cocrystal former (nicotinamide) concentration by a mathematical model based on solubility product theory and the complexation process. The phase diagram of a CBZ–NCT cocrystal in pure ethanol at 298.15 K is asymmetric, which leads to an excess of coformer being needed to isolate the cocrystal. In terms of this issue, it was found that the solvent mixture can have a significant effect on the symmetry of phase diagrams. Employing solvent mixtures could make the phase diagrams of the CBZ–NCT cocrystal more symmetric and enlarge the safe operation region for the cocrystal. Additionally, in the cocrystal formation process, the nucleation of cocrystal and carbamazepine in a slurry crystallization, is a competitive relationship. For avoiding single component crystallization, the supersaturation ratio of cocrystal to drug should be increased to inhibit carbamazepine nucleation. These findings are all beneficial to the development of the cocrystallization process of the CBZ–NCT cocrystal.

更新日期：2020-01-17
• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-08
Elham Parsi, Alireza Salabat

Abstract Active pharmaceutical ingredients with poor solubility in water and some organic solvents are a challenge in the pharmaceutical industry. To overcome this limitation, microemulsion systems are a choice to increase the solubility of a sparingly soluble active ingredient. The purpose of this study is to introduce and compare two types of oil-in-water (O/W) and ionic liquid-in-water (IL/W) microemulsions, which were formulated to increase the solubility of celecoxib as an active pharmaceutical ingredient. The proposed formulations are composed of the same nonionic surfactant/co-surfactant of Tween-80/transcutol®P, and different oil phases of isopropyl myristate, [BMIM][PF6] and [OMIM][PF6]. The pseudo-ternary phase diagrams for the microemulsion systems have been determined at a surfactant-to-co-surfactant mass ratio of 3:1 and 298.15 K. From the microemulsion region of the phase diagrams, four formulations was selected and their physico-chemical properties as density, viscosity, refractive index, electrical conductivity and surface tension were measured at 298.15 K. The solubilities of celecoxib in all selected formulations were also determined and compared. The results show considerable increases in solubility of the celecoxib in the ionic liquid-based microemulsion systems.

更新日期：2020-01-08
• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-08
Kazuhiko Ohashi, Nobutaka Hikiishi

Infrared (IR) spectra were measured for formamide (FA, HCONH2) solutions of Li(ClO4) and Na(ClO4). Both CN stretch and CO stretch bands of FA are observed to undergo upshifts in the presence of the metal ions. Quantum chemical calculations were performed for Li+(FA)n (n = 1–7) and Na+(FA)n (n = 1–8) complexes in order to model the metal ions in FA solutions. In previous Raman studies of the Li+ system, the so-called chelate configuration was assumed, in which the Li+ ion was put into the center of a ring FA dimer. However, the present calculations reveal that such a configuration is in conflict with the observed band shifts. The experimental IR spectra are reproduced by adopting appropriate isomers of Li+(FA)5 and Li+(FA)6 complexes, in which all FA molecules are coordinated to Li+ via the O atom, with a configuration such that the Li+ ion and NH2 group are on the same side of the CO bond. These complexes, especially Li+(FA)6, are also successful in replicating characteristic features observed in the previous Raman spectra. Similarly, an O-bound isomer of Na+(FA)6 is consistent with the experimental IR and Raman spectra of the Na+ system. A strong coupling among the CO oscillators of FA molecules is shown to be responsible for the upshifts of the νCO modes despite the coordination via the O atom.

更新日期：2020-01-08
• J. Solut. Chem. (IF 1.039) Pub Date : 2020-01-04
Yingmin Yu, Lili Zhang, Chuanfu Zhu, Xin Huang, Zhaohui Liao, Qingsong Li

Abstract Liquid–liquid equilibria (LLE) data for {water + 1-butanol + isophorone} and {water + 1-butanol + mesityl oxide} ternary systems were investigated systematically at different temperatures under atmospheric pressure. The Othmer–Tobias and Bachman equations were applied to analyze the dependability of the experimental LLE data. Selectivities and distribution coefficients were used to evaluate the extractive efficiency of the extractants. The Non-Random Two Liquid (NRTL) and Universal Quasi-Chemical (UNIQUAC) models were applied to correlate the studied systems and were well represented with all root mean square deviations (RMSD) less than 0.2%. Meanwhile, binary interaction parameters among these compounds were acquired during the correlation process.

更新日期：2020-01-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-12-10
Ramesh Kumar Banjare, Manoj Kumar Banjare, Sandhyarani Panda

A comprehensive study the effect of acetonitrile (ACN) with four cationic surfactants, viz. tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) was made by using the conductivity, surface tension, fluorescence and FTIR techniques. Significant micellar, interfacial and thermodynamic properties were studied by the tensiometeric and conductivity methods. The critical micelle concentration (CMC), aggregation number (Nagg), and Stern–Volmer constants (Ksv) have also been studied by the steady state fluorescence method using pyrene as probe. The fluorescence study also supports the CMC results obtained from conductivity and surface tension. FTIR was used to ascertain that the strength of intermolecular interactions such as hydrogen bonding, ion–ion pair interactions and induced dipole interactions between the surfactants and ACN depend upon the head-group of the surfactants. The interaction of surfactants with ACN is energetically favorable and occurs via direct interactions between the surfactants and ACN. The results further revealed that the strength of interactions between the surfactants and ACN follows the order: TTAB > CTAB > CPC > CPB.

更新日期：2019-12-11
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-08-02
U. A. Aziz, N. Adnan, M. Z. R. Sohri, D. F. Mohshim, A. K. Idris, M. A. Azman

Enhanced oil recovery (EOR) has been one of the favorable methods in improving oil recovery and extending the production time. One of the techniques used in enhanced oil recovery (EOR) is gas flooding, because of the gases sweeping ability to displace the oil into the production well. Unfortunately, the gas injection method causes severe gas fingering because of the higher mobility and lower viscosity and density of the gas, compared to oil, which creates uneven fluid dispersion (fingering). Thus, a stabilized surfactant foam is introduced to control the injected gas mobility. This paper aims to characterize how the blends of non-anionic and anionic surfactants could act as foam stabilizing agents and to provide a brief exploration on their ability to improve the gas flooding process. The foamability and foam stability of single and mixed surfactant were tested at ambient and elevated temperature; additionally, a salt tolerance study was performed to identify the capability of the foam to withstand real reservoir conditions. Two anionic surfactants: sodium dodecyl sulphate (SDS) and alpha olefin sulfonate (AOS) and one non-ionic surfactant, octyl phenol ethoxylate (TX-100), were used in the study. Each single surfactant was tested for its viscosity and surface tension at the air/water interface under ambient conditions and compared with the mixed surfactants. Data has shown that blending of anionic and non-ionic surfactants has contributed to lower IFT compared to the individual surfactants and to increase viscosity, which is an early indicator of good foam stabilizer for foam flooding, which may lead to oil recovery improvement. The mixture of non-ionic and anionic surfactants, particularly TX-100 and AOS, showed better foamability and foam stability at elevated temperature than the individual pure surfactants.

更新日期：2019-11-30
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-28

The aggregation behavior was investigated in mixtures of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) (anionic-rich catanionic) solutions. The study was conducted in solutions of water–ethylene glycol (EG) by means of surface tension, conductometry, cyclic voltammetry, zeta potential measurements, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. The degree of counterion dissociation (α), critical micelle concentration, aggregation numbers, interfacial properties, interparticle interaction parameters, and morphology of aggregates were determined. Based on regular solution theory, the cosolvent effects between SDS and CTAB as surfactants were also analyzed for both mixed monolayers at mixed micelles (βM) and the air/liquid interface (βσ). It was shown that the formation of large aggregates occurred in the presence of an excess of anionic surfactant. A phase transition from cylindrical micelles to spherical micelles in the anionic-rich regime was observed with an increase in the EG volume fraction. The inter particle interactions were assessed in terms of cosolvent effects on the micellar surface charge density and the cylindrical-to-spherical morphology change. Zeta potential and size of the aggregates were determined using dynamic light scattering and confirmed the models suggested for the processes taking place in each system.

更新日期：2019-11-29
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-25
Sayaka Katsu, Shori Ito, Norio Yoshimura, Masao Takayanagi

Near-infrared absorption spectra of aqueous solutions of eleven polyhydric alcohols (nine dihydric alcohols and two trihydric alcohols) at concentrations up to 20% were obtained at 20, 25, and 30 °C. Variations in the band due to O–H stretching vibration overtones of water and alcohol with changes in concentration and temperature were determined by a multivariate curve resolution-alternating least squares analysis, which identified the components of the band causing the spectral variation. The band consisted of three common components almost independent of the alcohol type. The first and the second components are attributed, respectively, to water molecules weakly hydrogen-bonded (or non hydrogen-bonded) and those strongly hydrogen-bonded with other water molecules, while the third component are due to water interacting with the alcohol and to the alcohol itself. The abundance of the first and third components decreased and increased, respectively, as the alcohol concentration increased. In contrast, the abundance of the second component increased initially and then decreased. The initial increase corresponds to the enhancement of hydrogen bonding by hydrophobic interactions. The subsequent decrease is due to an increase in water–alcohol interactions and a decrease in water concentration. The maximum increase in the abundance of the second component depended on the type of alcohol. The increase in abundance was greater for alcohols with larger alkyl groups. In contrast, the increase in abundance of the second component was smaller for alcohols with more hydric groups.

更新日期：2019-11-26
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-25
Fatemeh Zabihi, Farhoush Kiani, Mojtaba Yaghobi, Seyed Ahmad Shahidi

In this study, we experimentally determined the protonation constants, enthalpy change (ΔHo), change in Gibbs energy (ΔGo), and entropy change (ΔSo) for the deprotonation process of betanin over the temperature range of 298.15 to 318.15 K and at an ionic strength of 0.1 mol·dm−3 (NaClO4) with a combination of spectrophotometric and potentiometric methods. In addition, we theoretically calculated the values of the acidic dissociation constants, the optimized structure, and the thermodynamic properties of betanin in aqueous solutions at various temperatures by ab initio and DFT methods. Density function theory (DFT) methods with the B3LYP/6-31 + G(d) level of theory were applied for calculating the acidic dissociation constants of betanin and also interactions among the solvent and solvated cation, anion, and neutral species of betanin. Thomasi’s method was used to analyze the formation of intermolecular hydrogen bonding between water molecules and various species of betanin. There is a good correlation between the theoretically calculated and experimentally determined values of pKa of betanin.

更新日期：2019-11-26
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-23
Irfan Ullah, Musa Kaleem Baloch, Shanawer Niaz, Ayesha Sultan, Imran Ullah

Quite a high percentage of newly discovered drugs are discarded due to their low aqueous solubility and variable bioavailability. Therefore, it is necessary to explore new methodologies for increasing the aqueous solubility of such drugs. Several procedures have been proposed for this purpose, including salt formation, particle size reduction or using surfactants. In this report, we have improved the aqueous solubility of flurbiprofen by employing aqueous solution of anionic (SDS, SDBS), cationic (DTAB, CTAB, TTAB), non-ionic (Triton X-100 and Triton X-114 and DDAO) and zwitterionic DDAPS surfactants. It is concluded that all of the surfactants increased the solubility of flurbiprofen which increased with the increasing surfactant concentration. The reason behind such a trend was that the drug is partitioned between micelles and the aqueous phase. An increase in aqueous solubility of the drug was correlated with the (molar) solubilization ratio (χ), partition coefficient of drug (KM) between micelle and water, binding constant (K1) and standard state Gibbs energy of solubilization ($$\Delta G_{\text{s}}^{\text{o}}$$) of the drug in the micelles. The order of drug solubilization in nonionic and zwitterionic surfactants was found as Triton X-114 > Triton X-100 > DDAO > DDAPS. In the case of anionic surfactants, it was noted as SDBS > SDS, whereas cationic surfactants solubilized the drug in the order of CTAB > TTAB > DTAB. The differences in χ and log10KM are attributed to the structural features of the surfactants. The aggregation number, HLB, core volume of micelles and electrostatic interaction between drug and micelles play important roles in solubilization of drugs in micellar solutions. The nonionic surfactants proved to be better, due to their low critical micelle concentrations higher solubilization capability and nontoxic nature; they were also found to have better drug release profiles.

更新日期：2019-11-26
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-23
Liyan Qiu, Gordon R. Burton, Stephane Rousseau, Jing Qian

更新日期：2019-11-26
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-20
Juan S. Abella, Carmen M. Romero

Preferential interactions of α-chymotrypsinogen in water and aqueous solutions of ethylene glycol, glycerol, erythritol, sorbitol, and inositol were studied from precise density measurements under conditions of constant molality and constant chemical potential; to achieve the last condition, solutions were brought under equilibrium dialysis. The density measurements were performed at 298.15 K and they were used to determine the preferential interaction parameters. The results confirm a significant correlation between the numbers of hydroxyl groups of the polyols with the stability of α-chymotrypsinogen.

更新日期：2019-11-21
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-20
Elif Merve Sahin, Erol Ayranci

Interactions of 1-butyl-1-methylpyrrolidinium tetrafluoroborate (BMPYBF4) and 1-butyl-1-methylpiperidinium tetrafluoroborate (BMPIBF4) with water and acetonitrile (AN) were studied in a comparative manner through the measurements of density and speed of sound at 288.15, 293.15, 298.15, 303.15 and 308.15 K. The measured densities and speeds of sound were used in calculation of apparent molar volumes and apparent molar isentropic compressions of the two ionic liquids (ILs) in water and in AN. Infinite dilution values of the two apparent molar quantities were obtained by extrapolation. Then, these properties were evaluated in terms of IL–water and IL–AN interactions. The effect of presence of an additional cyclic –CH2– group in the structure of BMPIBF4, compared to that of BMPYBF4, on the volumetric and acoustic properties has been examined both in water and in AN. The effect of solvent, H2O or AN, on the solution behaviors of the two ILs is discussed, based on transfer apparent molar volumes and transfer apparent molar isentropic compressions from H2O to AN. Apparent molar isobaric expansions at infinite dilutions were determined. Temperature effects on solution behaviors of the two ILs in H2O and in AN are discussed based on variation of apparent molar properties at infinite dilution with temperature.

更新日期：2019-11-20
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-19
Dhiman Ray, Bijan Das

The aggregation phenomena of two ionic liquid surfactants—1-decyl-3-methylimidazolium chloride (C10MeImCl) and 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl) have been investigated in aqueous solutions in the presence of a polyelectrolyte, sodium polystyrenesulfonate (NaPSS), using electrical conductivity, surface tension, fluorescence and vapor pressure measurements. The counterion-condensation behavior of aqueous NaPSS has also been studied and approximately 62% of the counterions have been found to remain uncondensed in these solutions. The characteristic concentrations signifying different kinds of interactions, namely the critical aggregation concentration and the polymer saturation concentration, in the premicellar regime have been identified. Surface-active complexes with bound surfactant monomers onto the polyion backbone, non-surface active aggregates with small micellar units wrapped by polyion chains, and non-surface active micelles of ionic liquid surfactant monomers, were found to form in aqueous ionic liquid surfactant solutions in the presence of NaPSS. The surfactant concentration where polyelectrolyte–surfactant monomer complexes begin to form (cac), the concentration where the polyion chains get saturated with the small micellar units (psc), and the concentration where micelles of ionic liquid surfactant molecules begin to appear (cmc*) were identified in aqueous C16MeImCl solutions in the presence of NaPSS. Only two critical concentrations, namely the psc, and cmc* were, however, detected in aqueous C10MeImCl solutions in the presence of NaPSS. Effects of alkyl chain length of the ionic liquid surfactants, temperature, NaPSS concentration, and the charge parameter of NaPSS on the self-aggregation of the ionic liquid surfactants have been considered to elucidate the interactions in these mixed systems. The thermodynamics of micellization in these systems have also been studied and the spontaneity of the polyelectrolyte-induced micellization processes have been rationalized for the systems investigated, with the entropy terms superseding the enthalpy terms.

更新日期：2019-11-19
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-19
Jingwei Yang, Zhengkun Hou, Guilin Wen, Peizhe Cui, Yinglong Wang, Jun Gao

The selection of the extractant is an important consideration for the design of liquid–liquid extraction processes. Researchers are paying more attention to a priori predictions of liquid–liquid equilibria. The predictive and fully open-source thermodynamic model COSMO-SAC (conductor-like screening model-segment activity coefficient) uses quantum chemical calculations for calculating activity coefficients and thermodynamic properties. Through a brief review of the recent advances of COSMO-SAC in predicting liquid–liquid equilibrium of ionic liquid systems, this work assessed the accuracy of prediction for different chemical family combinations and generated directions for future improvement.

更新日期：2019-11-19
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-18
Sinem Ezgi Sarlı, Umit Ay

A complex of anthracene with methyl-beta-cyclodextrin (A-Me-β-CD) having fluorophoric characteristics was obtained in aqueous medium. Spectroscopic and thermal analyses of the complex were performed by Fourier transform infrared spectroscopy and differential scanning calorimetry-thermogravimetry. The interaction of Me-β-CD and anthracene was also analyzed by means of spectrometry by a UV–Vis spectrophotometer. The stoichiometry of the complex was determined by the Benesi–Hildebrand method. The complex formation constant was found to be (42 ± 3) × 103 L·mol−1. The Gibbs energy and excited singlet state energy were calculated. The mechanism of the quenching effect of Co(II) and Ni(II) metals in the inclusion complex was studied. The Stern–Volmer constant, bimolecular quenching rate constant, lifetime and approximate activation energy values were determined, and the quenching was found to be diffusion controlled dynamic quenching. In addition, with the energy band calculations made, it was shown by means of Taug curves that electron transfer was made to Ni and Co metals from the complex fluorophore group in the quenching mechanism.

更新日期：2019-11-19
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-13
Cai Liu, Yan Zhang, Jingjing Guo, Fengling Cui

In this paper, under the condition of a simulated human physiological environment, steady-state fluorescence, UV spectra, three-dimensional fluorescence, time-resolved fluorescence, and the circular dichroism were implemented to investigate the binding mechanism between bicyclol (BYL) and human serum albumin (HSA). The results revealed a red shift in the UV absorption wavelength of HSA and an increase in absorption intensity of HSA with increasing concentration of bicyclol. Bicyclol quenched the intrinsic fluorescence of HSA via a static quenching mechanism. At 298 K, the number of binding sites (n) and binding constant of BYL–HSA were about 1 and 9.67 × 103 L·mol−1, respectively. The thermodynamic parameters ΔG, ΔH, ΔS are − 22.76 and − 19.07 kJ·mol−1 and 27.17 J·K−1·mol−1 respectively, which demonstrated that the binding of bicyclol and HSA was mainly driven by hydrophobic and electrostatic forces. In addition, the molecular docking method was utilized to further investigate the binding site when BYL is combined with HSA, which indicated that BYL is bound on the hydrophobic cavities of sub-domains IIA and IIIA of HSA, respectively, and that the binding affinity in the IIIA site was much higher than that in the IIA site.

更新日期：2019-11-14
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-11-08

A thermodynamic model is introduced to describe equilibrium conditions of gas hydrates formed from mixtures of CO2, N2 and H2O. The model employs the van der Waals and Platteeuw (vdW–P) solid solution theory and a modified version of cubic-plus-association equation of state that uses the Peng–Robinson equation of state for physical interactions (PR–CPA) to describe hydrate and fluid phases, respectively. When not available elsewhere, the model parameters are determined as part of this work. Pure component parameters for N2 were calculated by fitting of the PR–CPA parameters to vapor pressures and saturated liquid densities. Moreover, solubility data for N2 in pure water are used to fit the binary interaction parameter for the N2–H2O system. Finally, Kihara cell potential parameters are obtained by regressing the model to the hydrate dissociation pressures of mixed hydrates. The model is validated with available experimental data in terms of equilibrium dissociation pressure and hydrate composition. Results reveal that the model is capable of describing equilibrium conditions with high accuracy. In addition to the equilibrium dissociation pressure, the model is able to predict hydrate compositions with satisfactory accuracy compared to other models, although such data were not utilized as reference data in the fitting procedure. Due to disparity amongst various data sets for the studied system, it is difficult to find unequivocally a model that perform better for all data sets. However, the introduced model shows more accurate results for most data sets and obtains satisfactory agreement in the rest. Additionally, the presented model predicts the structural transition boundary better than other similar models.

更新日期：2019-11-11
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-24
Ahmed E. Fazary, Hala A. Ibrahium, Maha A. Youssef, Nasser S. Awwad, Hisham S. M. Abd-Rabboh

The complexing capacities of thymoquinone with trivalent holmium(III) and gadolinium(III) metal ions and their overall stability constants in aqueous solutions were obtained using the HYPERQUAD 2008 program from the pH-potentiometric titration data. The molecular structures of thymoquinone—metal complexes formed in solutions were determined based on some spectral methods, and molecular modeling. The graphic representation of the complex species concentration curves is given by the distribution diagram performed by means of the HySS 2009 modeling program, which furnishes a variety of data presentations, including tables of concentrations of all species present in solution in the selected pH ranges.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-17
Jalel M’halla, Sondes Boughammoura, Anis Ghazouani

Conductivity measurements in water and at 25 °C show that the variation of the equivalent conductivity ΛPX with the counter ion concentration CX of some PDDPX polyelectrolytes, poly(1,1-dimethyl-3,5-dimethylene piperidinium, X), for X ≡ Br−, Cl−, $${\text{NO}}_{3}^{ - }$$ and F−, is characterized by an inversion in Kohlraush’s law (i.e., $$\forall$$C, ΛPX < ΛPX′ if $$\lambda_{\text{X}}^{ \circ }$$ > $$\lambda_{{\text{X}}^{\prime}}^{ \circ }$$), where $$\lambda_{\text{X}}^{ \circ }$$ is the conductivity of the counter ion X at infinite dilution. This anomaly cannot be explained in the case of stretched polyions, by the dependence of ΛPX with the degree of dissociation αX, since αX remains quasi-constant at about 0.7 for CX < 2 × 10−2 mol·L−1. On the other hand, such a reversal implies that in the case of a coiled conformation, there is an increase in the ionic condensation, which is incompatible with hydrophobic folding. Similarly, hydrodynamic, electrophoretic and ionic frictions on these PDDPX polyelectrolytes cannot explain this inversion given their weak dependence with the nature of the counter ion X. In fact, for X ≡ Br−, Cl−, $${\text{NO}}_{3}^{ - }$$, and for X ≡ F− with CX > 10−3 mol·L−1, this anomaly occurs for PDDPZS+ polyions having a completely stretched chain conformation for which the translational dielectric friction effect on their charged groups becomes important to a variable degree depending on the nature of X. For PDDPF polyelectrolytes, this anomaly is amplified at high dilution because of possible synergy between the ionic dissociation and the hydrophobic character of the polyion, giving rise to a “pearl-necklace conformation” of effective length, L, decreasing with the dilution. In this work, we represent the conformation of polyions by an ellipsoid with a variable eccentricity γp, or by a chain of charged spheres with a variable group radius Rg, or by a pearl necklace model with a variable length L and a variable bead radius. The stability of the general configuration was formally studied according to a new approach based on the principle of superposition of ionic screening effects on the different charged groups.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-24
Li Xinbao, He Yating, Farajtabar Ali, Song Nan, Zhao Hongkun

The effect of solvent on the solubility of sulfachloropyridazine was studied by making a correlation between the solubility values and solvent’s descriptors for solvent–solute and solvent–solvent interactions with the help of linear solvation energy relationships concept. From analysis of the molecular structure of sulfachloropyridazine, the variation of solubility was well explained in terms of the change in hydrogen bond basicity of mixtures when the mole fraction of methanol (or ethanol or isopropanol) increased in all aqueous binary solvent mixtures. The preferential solvation analysis of sulfachloropyridazine in the three aqueous co-solvent solutions of isopropanol, ethanol and methanol was carried out from solubility values through the method of inverse Kirkwood–Buff integrals. In water-rich compositions of the aqueous co-solvent solutions, the δx1,3 values are negative, indicating that the sulfachloropyridazine was solvated preferentially by the solvent water. In intermediate and alcohol-rich compositions, sulfachloropyridazine was preferentially solvated by the isopropanol, ethanol or methanol. The magnitude of preferential solvation of sulfachloropyridazine is greater in isopropanol solutions than in the other two co-solvent solutions. Analysis results of the KAT-LSER and IKBI methods indicate that the solute mainly acts as a Lewis acid through its –NH2 and > NH functionalities. In addition, the enthalpy, Gibbs energy and entropy of transfer were obtained, which demonstrated that the solubilization ability was more favorable in intermediate composition of the alcohols.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-22
B. Mukesh, T. Sreekanth, M. Gowrisankar, M. Raveendra

Densities (ρ), speeds of sound (u), and viscosities (η) are reported for binary mixtures of 2-methoxyaniline with chlorinated ethane components (1,2-dichloroethane, 1,1,2-trichloroethane and 1,1,2,2-tetrachloroethane) over the entire composition range of mole fraction at T = (303.15–313.15) K and at atmospheric pressure (0.1 MPa). The excess properties: excess molar volume, excess isentropic compressibility and deviation in viscosity are calculated from the experimental density, speed of sound and viscosity. Excess properties are correlated using the Redlich–Kister polynomial equation. The excess partial molar volumes and excess partial molar isentropic compressibilities are calculated for all the binary systems throughout the composition range and at infinite dilutions. The results are analyzed in terms of electron donor–acceptor interactions leading to the formation of intermolecular complexes and hydrogen bonding between 2-methoxyaniline and chlorinated ethane molecules. The VE results are analyzed in light of the Prigogine–Flory–Patterson theory. Analysis of each of the three contributions viz. interactional, free volume and P* to VE has shown that the interactional contribution are positive for all studied systems, the free volume and P* contributions are negative for all the binary mixtures.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-23
Arifa Shaheen, Rabia Arif

In the present study, we have examined the mixed micellization behavior of promethazine hydrochloride (PMT) and the nonionic surfactant Triton X-100 mixtures at different mole fractions of TX-100 (α1) in aqueous solutions with and without additives (CTAB, glycine, vitamin-C and PVP) using conductometric, tensiometric and fluorescence techniques. PMT belongs to a class of amphiphilic drugs called phenothiazines and is used as an antihistamine, analgesic and sedative. Various parameters which include the ideal critical micelle concentration (cmcid), ideal micellar mole fraction, $$X_{1}^{\text{id}}$$, of TX-100, micellar composition, $$X_{1}^{\text{mic}}$$, of TX-100, interaction parameter (β), activity coefficients ($$f_{1}^{\text{mic}}$$ and $$f_{2}^{\text{mic}}$$), thermodynamic parameters $$\left( {\Delta G_{\text{mic}}^{ 0} , \;\Delta G_{\text{ad}}^{0} \;{\text{and}}\;\Delta G_{\text{mic}}^{\text{E}} } \right)$$ and interfacial parameters (Γmax, Amin, and Πcmc) have been calculated by using Clint’s and Rubingh’s models. In our study, we have found that the cmc < cmcid, β < 0 and $$f_{1}^{\text{mic}}$$ and $$f_{2}^{\text{mic}}$$ < 1; all the mixtures show synergism $$X_{1}^{\text{id}}$$ as well as non-ideality. The values of $$\Delta G_{\text{ad}}^{0} > \Delta G_{\text{mic}}^{ 0}$$ for all the systems indicate that adsorption phenomenon occurs primarily as compared to the micellization process. The negative values of $$\Delta G_{\text{mic}}^{\text{E}}$$ for all α1 in the absence and presence of additives indicate greater stability of the micelles of mixtures than for the micelles of pure components. The interfacial parameters give information about the packing of amphiphilic molecules.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-18
Shiraz A. Markarian, Heghine H. Ghazoyan, Hasmik R. Sargsyan, Gohar A. Shahinyan

Densitometry, UV–Vis and FT IR spectroscopy were used to study the complex formation of cobalt(II) chloride and nickel(II) chloride with diethylsulfoxide (DESO). The apparent molar volumes and partial molar volumes were determined for solvated ions in DESO. The complex formation of nickel(II) and cobalt(II) ions with DESO molecules via oxygen atom of SO group was revealed from the SO stretching band in the FT IR spectra. UV–Vis spectra show the coexistence of two types of complexes with DESO in solution. The results show that solvating ability of DESO is stronger than that of dimethylsulfoxide.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-22
László Kiss, Sándor Kunsági-Máté

In this report, the solubility of hydroquinone (1,4-dihydroxybenzene) was determined in dichloromethane, trichloromethane and carbon tetrachloride at 298 K by using cyclic voltammetry. By the proposed cosolvent calibration method a mixed solvent was used for the determination of solubility where acetonitrile was the co-solvent. The molar ratios of the two solvents were uniform during the whole procedure both in the calibration solutions and in solutions used for solubility determinations. The solubility of hydroquinone decreased by the decrease of solvent permittivity, which were in dichloromethane 5.683 mmol·L−1, in trichloromethane 2.785 mmol·L−1 and in carbon tetrachloride 0.321 mmol·L−1.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-10-12
Milan B. Vraneš, Snežana M. Papović, Slobodan B. Gadžurić

In this work, the absorption spectra of cobalt(II) nitrate and chloride complexes in the composition xCa(NO3)2–(1 – x)NH4NO3–H2O have been investigated in the 400–800 nm range of wavelength at T = 328.15 K and atmospheric pressure p = 101.3 kPa. Spectra were recorded in 0.3 Ca(NO3)2–0.7 NH4NO3–H2O solutions with variable water content (R = H2O/salt mole ratio; Rws = 1.0, 1.2, 1.6 and 2.0), and in xCa(NO3)2–(1 – x)NH4NO3–H2O (x = 0.3, 0.5 and 0.7) solutions where the H2O/salt mole ratio was kept constant (Rws = 2.0). The blue shift of the absorption maximum with increasing water content (Rws) suggests simultaneous coordination by water molecules and nitrate ions. From an analysis of the spectra, it can be concluded that the following complexes: [Co(NO3)4(H2O)2]2−, [Co(NO3)2Cl2]2− and [CoCl4]2− were formed. The overall stability constants of these complexes and the corresponding resolved species spectra were calculated at T = 328.15 K.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-09-25
Kavosh Majlesi, Clemente Bretti, Concetta De Stefano, Gabriele Lando, Kimia Majlesi, Silvio Sammartano

Protonation of nicotinic acid has been investigated by means of potentiometric titrations at different temperatures 283.15 ≤ T (K) ≤ 383.15 and ionic strengths of NaCl(aq), 0.12 ≤ I (mol·kg−1) ≤ 4.84 and mixed NaCl with MgCl2 or CaCl2. Stability constants of the CaL+ and MgL+ species were obtained by means of the ΔpK method. Different models (e.g. Debye–Hückel type equation, Specific Ion Interaction Theory, Pitzer and van’t Hoff) were applied to account for the ionic strength and temperature dependences, in order to obtain data in a standard state and parameters to calculate stability constants in any point of our experimental domain. Speciation studies were performed simulating the conditions of natural fluids. Literature data were investigated for comparison with the experimental results here obtained.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-09-18
Glenn Hefter, Cezary Gumiński

A thorough search of the scientific literature under the auspices of the IUPAC Sub-Committee on Solubility and Equilibrium Data (SSED) has identified and compiled quantitative thermodynamic data for the first sulfate protonation step from about 270 papers, reports, books and electronic databases. A critical evaluation of these sources using well-defined criteria has rejected about half of them. The remaining (‘accepted’) data reveal that the standard state values of the first protonation constant of the sulfate ion, $$K_{1}^{\text{o}}$$, corresponding to the equilibrium: $${\text{SO}_{4}^{2 - }} ({\text{aq}}) + {\text{ H}}^{ + } \left( {\text{aq}} \right) \rightleftharpoons {{\text{HSO}}_{4}^{ - }}({\text{aq}})$$ at infinite dilution, are known to good levels of accuracy up to ~ 250 °C. However, at higher temperatures, and at all temperatures in the presence of added electrolytes, the equilibrium constant values are much less certain. The corresponding values for the enthalpy ($$\Delta_{\text{r}} H_{1}^{\text{o}}$$), entropy ($$\Delta_{\text{r}} S_{1}^{\text{o}}$$) and isobaric heat capacity ($$\Delta_{\text{r}} C_{p,1}^{\text{o}}$$) changes are also moderately well determined at near-ambient temperatures but are much more poorly defined both at higher temperatures and in the presence of even modest concentrations of added electrolytes. Comments on a number of aspects of the data and their evaluation are provided.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-09-10

The present investigation describes the adsorption capability of native and magnetic oxide (Fe3O4) impregnated bentonite clays for the adsorption of Cr(III) from aqueous solutions. The characterization of native bentonite as well as the impregnated bentonite was performed by PZC, SEM, BET, XRD and FTIR spectroscopy. The results proved that magnetized bentonite with high specific surface area provides high affinity and fast kinetics for the uptake of Cr(III). In the case of lower metal ion concentration in working solutions, the adsorption efficiency of the impregnated form was better than the native form. The effects of pH, contact time, temperature and initial metal ion concentration on overall adsorption efficiency were determined in detail. The equilibrium data was interpreted by linear forms of Langmuir, Fruendlich and Dubinin–Radushkevich isotherm models. Maximum adsorption capacity (Xm) for Cr(III) uptake was obtained as 1.25 and 1.28 mmol·g−1 for native and impregnated bentonite respectively. The apparent mean free energy of adsorption (E) determined from the DRK model was less than 8 kJ·mole−1 indicating that the Cr(III) adsorption on both adsorbents was physisorption in nature. Two different kinetic models, pseudo first and pseudo second order models were subjected to evaluate the kinetic data and reaction mechanism.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-09-24
Manidipa Basu, Prithwish Sinharoy, Jayshree Ramkumar, Santosh L. Gawali, Bijaideep Dutta, J. N. Sharma

The use of any new extractant requires the study of its tendency to form third phases. To understand the phase separation process it is important to have knowledge of the molecular scale phenomena present in the system. This includes the mixing of the substances and the behavior and nature of the aggregates. Here we report the mixing properties of N,N,N′,N′-tetra-(2-ethyl hexyl) diglycolamide (TEHDGA)–dodecane–isodecanol (in the absence and presence of micellar aggregates) which is recognized as a promising system for the separation of minor actinides through the conventional solvent extraction route. The nature of interactions between TEHDGA and isodecanol was investigated using several techniques, including density and speed of sound measurements, ultraviolet absorption spectroscopy and computational studies. The TEHDGA–isodecanol interaction was found to be favored over the inter-isodecanol interaction. On equilibrating the organic phase with nitric acid, some indication of pre-micellar aggregation was obtained. Increase of micellar aggregate size on addition of isodecanol was indicated.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-08-19
Zareen Abbas, Elisabet Ahlberg

Monte Carlo (MC) simulations were used to calculate single ion and mean ionic activity coefficients and water activity in concentrated electrolytes and at elevated temperatures. By using a concentration dependent dielectric constant, the applicability range of the MC method was extended to 3 mol·L−1 or beyond, depending on the salt. The calculated activity coefficients were fitted to experimental data by adjusting only one parameter, i.e., the cation radius. Fitted ionic radii obtained by such a procedure indicate the extent of cation–anion interaction in a salt solution. For example, the fitted radii of Li+ and Na+ in LiClO3 and NaClO3 indicate that Li+ is strongly hydrated and has a weak interaction with the ClO 3 − ion whereas Na+ forms ion pairs and loses its hydration. The single ion activity coefficients for protons and chloride ions in HCl were calculated by MC simulations and compared with experimental values obtained by ion selective electrodes. The calculated single ion activity coefficients for protons and chloride ions are much lower and higher, respectively, than the experimental values. However, the mean activity coefficients of HCl obtained by the MC simulations, ion selective electrodes and vapor pressure measurements are in good agreement. In the case of NaCl and KCl the calculated single ion activity coefficients of Na+, K+, and Cl− are much closer to the values obtained by ion selective electrodes. The results in HCl indicate that the hydrated proton is large and includes the chloride ion within the hydration shell, i.e., the apparent size of the chloride ion is negligible.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-07-08
Xu Bao, Zhaohui Chen, Juan Han, Yun Wang, Chunmei Li, Liang Ni

Binodal curves of the aqueous 1-butyl-3-methylimidazolium tetrafluoroborate([C4mim]BF4) + kosmotropic salt (Na3PO4,(NH4)3PO4) + water aqueous two-phase systems were determined experimentally at 288.15, 298.15, 308.15 and 318.15 K. Three empirical equations were used to correlate the binodal data. All three empirical equations reproduce the data with a high degree of precision. The effect of temperature on the binodal curves was studied. Corresponding to two different salts, the two-phase area decreases with increasing temperature. From the binodal model for these systems, the effective excluded volumes (EEV) were obtained. The binodal curves and EEV both indicate that the salting-out abilities are in the order: Na3PO4 > (NH4)3PO4. And, the reliability of the tie-line compositions was proved by the empirical correlation with the Othmer–Tobias and Bancroft equations. The results show that the salting-out strength is greater at lower temperatures. Additionally, a relatively simple two-parameter equation was used for the correlation of the tie-line data.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-08-22
V. I. Smirnov, V. G. Badelin, V. P. Barannikov, M. S. Kurbatova

The dissolution enthalpies ($$\Delta_{\text{sol}} H_{\text{m}}$$) of dl-α-alanyl-dl-α-valine (AlaVal) and dl-α-alanyl-dl-α-norleucine (AlaNln) in aqueous solutions of dodecyl sulfate (SDS) at SDS concentration of mSDS = 0.05 mol·kg−1 and peptide concentration m = 0.010 to 0.025 mol·kg−1 at T = 298.15 K were measured via calorimetry. The results obtained have been used to calculate the transfer enthalpies ($$\Delta_{\text{tr}} H_{\text{m}}$$) of AlaVal and AlaNln from water into (water + SDS) micellar solution. Thermochemical characteristics of the transfer of AlaVal, and AlaNln in the investigated range of peptide concentrations are compared. The results are interpreted by considering ion–ion, ion–polar, and hydrophobic–hydrophobic interactions between the dipeptides and SDS micelles.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-09-07
Xianshu Qiao, Fang Han, Long Zhao, Huipeng Li, Jianbin Zhang

In the development of CO2 capture and utilization, the physical and transport properties of the binary systems are significant, because these can affect the gas absorption and desorption processes. Thus, we report the densities and viscosities of two binary systems: 2-ethoxyethanol (ECS) + water (H2O) and ECS + dimethyl sulfoxide (DMSO), with various compositions at temperatures from (298.15 to 318.15) K. On the basis of these data, excess molar volumes ($$V_{\text{m}}^{\text{E}}$$) and viscosity deviations (Δη) were calculated. The $$V_{\text{m}}^{\text{E}}$$ values of the two binary mixtures are negative and decrease with increasing temperatures; Δη values are positive at all compositions and decrease with increasing temperatures. The $$V_{\text{m}}^{\text{E}}$$ and Δη values were fitted with the Redlich–Kister equation. The physico-chemical properties of the two binary systems, including activation enthalpy and entropy, were calculated from the kinematic viscosity. In addition, various spectral results offer evidence for the formation of weak interactions between ECS and DMSO or H2O.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-07-23
Caroline Marks, Alexander Mitsos, Jörn Viell

1-Ethyl-3-methylimidazolium acetate (EMIMAc) is an ionic liquid (IL) often investigated as a solvent, especially in the context of biopolymers and biomass pretreatment. A reduced solvent efficacy occurs upon the addition even of low amounts of water to EMIMAc. Molecular mechanisms have not yet been fully understood. It is expected that the functionality as hydrogen bond donor and acceptor is key for the solvent–solute interactions. In this work, we analyze the solvent efficacy of EMIMAc in terms of hydrogen–deuterium (H/D) exchange at the C(2)-position in mixtures with water or acetic acid added as proton donors. Low-field NMR spectroscopy and deuterated solvents are used for a time-resolved evaluation of H/D exchange reactions. The H/D exchange is also modeled to explore changes in the reaction kinetics as a function of the mixture composition. The significant difference in calculated rate constant values among the concentration regimes shows that the chosen model equations of a possible pseudo-first-order and second-order reaction mechanism including water dissociation do not cover all interaction phenomena that influence the exchange in the individual concentration ranges. However, the modeling also indicates that the investigated interaction of $$\hbox {EMIM}^+$$ and $$\hbox {Ac}^-$$ remains constant for concentrated IL mixtures containing $$70\, {\text{mol}}\%$$ of EMIMAc in water up to diluted mixtures as low as $$30\, {\text{mol}}\%$$ EMIMAc. This exemplifies the change between ions strongly associated in networks in concentrated mixtures suitable for biomass pretreatment and the much less associated anion–cation pairs in diluted mixtures which leads to the decreased efficiency of EMIMAc with increasing water content.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-08-02
Sanaz Edrisi, Hamid Bakhshi, Mostafa Rahimnejad

In present study, the liquid–liquid equilibrium of the quaternary system of polyethylene glycol (PEG) (with molar masses of 1000, 2000, 6000, and 8000 g·mol−1), sodium tartrate salt, Penicillin G and water at 298 K were investigated. The partitioning of Penicillin G between two aqueous phases was also reported. The extended non random two liquid (NRTL) and extended Universal Quasi Chemical (UNIQUAC) models were used to correlate the experimental equilibrium data. The parameters of these activity coefficient models were optimized for the investigated systems. The results show that the polymer molar mass has a dominant effect on the partition coefficient of Penicillin G. Also, results of both thermodynamic models were very satisfactory and satisfactory predicted the equilibrium concentrations of the components in ATPS. Comparison of the absolute average deviation of the two models shows that the extended UNIQUAC model was superior to the extended NRTL model for correlation and interpolation of phase equilibrium data.

更新日期：2019-11-04
• J. Solut. Chem. (IF 1.039) Pub Date : 2019-08-15
Catarina M S S Neves,Teresa B V Dinis,Pedro J Carvalho,Bernd Schröder,Luís M N B F Santos,Mara G Freire,João A P Coutinho

The order of the salting-in or salting-out inducing ability of ions on the aqueous solubility of macromolecules in aqueous solutions is known as the Hofmeister series. Taking into account that ionic liquids (ILs) are constituted by ions, they can exert similar effects on the solubility of other ILs in aqueous media. In order to expand the knowledge on the salting-in/-out ability of ILs, experimental studies on the solubility of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonylimide) in water in presence of other IL/salts were conducted at 298.15 K at atmospheric pressure. Both the impact of the anion and cation of the IL were evaluated with the following ILs/salts: 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium hydrogensulfate, cholinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide, in a wide composition range. As happens with common salts, both salting-in and salting-out effects exerted by ILs were observed, with a higher impact exerted by the IL anion on the salting-out phenomenon. These data allow to better understand the ILs impact when designing liquid-liquid separation processes.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2018-12-14
Poonam Patyar,Gurpreet Kaur,Tarnveer Kaur

Apparent molar volumes ( ϕ V ) of glycine/l-alanine in water and in aqueous citric acid (CA) solutions of varying concentrations, i.e. (0.05, 0.10, 0.20, 0.30, 0.40 and 0.50) mol·kg-1 were determined from density measurements at temperatures T = (288.15, 298.15, 308.15, 310.15 and 318.15) K and at atmospheric pressure. Limiting partial molar volumes ( ϕ V o ) and their corresponding partial molar volumes of transfer ( Δ tr ϕ V ) have been calculated from the ϕ V data. The negative Δ tr ϕ V values obtained for glycine/l-alanine from water to aqueous CA solutions indicate the dominance of hydrophilic-hydrophobic/hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions over ion/hydrophilic-dipolar interactions. Further, pair and triplet interaction coefficients, i.e. ( V AB ) and ( V ABB ) along with hydration number ( n H ) have also been calculated. The effect of temperature on the volumetric properties of glycine/l-alanine in water and in aqueous CA solutions has been determined from the limiting partial molar expansibilities ( ∂ ϕ V o / ∂ T ) p and their second-order derivative ( ∂ 2 ϕ V o / ∂ T 2 ) P . The apparent specific volumes ( ν ϕ ) for glycine and l-alanine tend to approach sweet taste behavior both in the presence of water and in aqueous CA solutions. The ν ϕ values for glycine/l-alanine increase with increase in concentration of CA at all temperatures studied. This reveals that CA helps in enhancing the sweet taste behavior of glycine/l-alanine which also supports the dominance of hydrophobic-hydrophobic interactions.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2018-12-14
Katarzyna Szymczyk,Anna Zdziennicka,Bronisław Jańczuk

Measurements of the surface tension of aqueous solutions of polysorbates (Tween 20, Tween 60 and Tween 80) at 293, 303 and 313 K were made. On the basis of the obtained results the Gibbs surface excess concentration of the Tweens at the water-air interface and critical micelle concentrations were determined. Knowing the Gibbs surface excess concentration and taking into account the difference between the limiting area occupied by water and Tween molecules at the water-air interface, the fraction occupied by Tween molecules was established. The limiting area occupied by the Tween molecule was calculated by applying the Joos equation. The area determined in such a way was confirmed by the calculations of cross section of Tween molecules based on the bond lengths and the angles between them as well as the average distance between the molecules, taking into account their different conformations. This area was used for calculation of the standard Gibbs energy of adsorption using the Langmuir equation. The standard Gibbs energy of Tweens adsorption at the water-air interface was also calculated from the hydrophobic part of Tween molecule-water interface tension and that of hydrophobic part. Using the determined values of standard Gibbs energy of adsorption at different temperatures, the standard enthalpy and entropy values were deduced. The standard thermodynamic functions of micellization were also determined and compared to the Gibbs energy of Tween molecules interactions through the water phase.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2018-12-14
Dorota Warmińska

Apparent molar volumes and apparent molar compressibilities for d-sorbitol in (0.05, 0.1, 0.2 and 0.3) mol·kg-1 aqueous solutions of l-alanine, l-cysteine and l-histidine and NaCl have been determined from measurements of solution density at T = (288.15, 298.15, 308.15 and 318.15) K and sound velocity at T = 298.15 K, as a function of the concentration of the sugar alcohol. The data were used to obtain the limiting apparent molar volumes, limiting apparent molar compressibilities and the corresponding transfer parameters. Limiting apparent molar expansibilities and their second order derivatives and volume interaction coefficients were also estimated. These parameters are discussed in terms of d-sorbitol and co-solute (amino acid or sodium chloride) interactions in aqueous solutions.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2010-02-18
Rabindra N Roy,Lakshmi N Roy,Shahaf Ashkenazi,Joshua T Wollen,Craig D Dunseth,Michael S Fuge,Jared L Durden,Chandra N Roy,Hannah M Hughes,Brett T Morris,Kevin L Cline

The values of the second dissociation constant, pK(2) of N-(2-hydroxyethyl) piperazine-N'-2-ethanesulfonic acid (HEPES) have been reported at 12 temperatures over the temperature range 5 to 55 degrees C, including 37 degrees C. This paper reports the results for the pa(H) of eight isotonic saline buffer solutions with an I = 0.16 mol*kg(-1) including compositions: (a) HEPES (0.01 mol*kg(-1)) + NaHEPES (0.01 mol*kg(-1)) + NaCl (0.15 mol*kg(-1)); (b) HEPES (0.02 mol*kg(-1)) + NaHEPES (0.02 mol*kg(-1)) + NaCl (0.14 mol*kg(-1)); (c) HEPES (0.03 mol*kg(-1)) + NaHEPES (0.03 mol*kg(-1)) + NaCl (0.13 mol*kg(-1)); (d) HEPES (0.04 mol*kg(-1)) + NaHEPES (0.04 mol*kg(-1)) + NaCl (0.12 mol*kg(-1)); (e) HEPES (0.05 mol*kg(-1)) + NaHEPES (0.05 mol*kg(-1)) + NaCl (0.11 mol*kg(-1)); (f) HEPES (0.06 mol*kg(-1)) + NaHEPES (0.06 mol*kg(-1)) + NaCl (0.10 mol*kg(-1)); (g) HEPES (0.07 mol*kg(-1)) + NaHEPES (0.07 mol*kg(-1)) + NaCl (0.09 mol*kg(-1)); and (h) HEPES (0.08 mol*kg(-1)) + NaHEPES (0.08 mol*kg(-1)) + NaCl (0.08 mol*kg(-1)). Conventional pa(H) values, for all eight buffer solutions from 5 to 55 degrees C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 degrees C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH 7.3 to 7.5 at I = 0.16 mol*kg(-1).

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2010-02-18
Rabindra N Roy,Lakshmi N Roy,Michael S Fuge,Chandra N Roy,Curtis A Himes,Paul A Bryant,Kyle T Robinson,Daniel A Kaufmann,Colby H Grove,Toshi Ghosh,Adonis Bwashi

The values of the second dissociation constant pK2 and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over the temperature range 5 to 55°C including 37°C. This paper reports the paH values of four chloride ion free buffer solutions and eight buffer solutions with I = 0.16 mol·kg -1, matching closely to that of the physiological sample. Conventional paH values for all twelve buffer solutions from 5 to 55°C, are reported. The residual liquid junction potential correction for two widely used temperatures, 25 and 37°C, has been made. The flowing-junction calomel cell method has been utilized to measure Ej , the liquid junction potential. The operational pH values for four buffer solutions at 25 and 37°C are calculated using the physiological phosphate buffer standard based on NBS/NIST convention. These solutions are recommended as pH standards in the pH range of 6.8 to 7.2 for physiological fluids.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2010-02-18
Lakshmi N Roy,Rabindra N Roy,Sean R Lenoue,Cole E Denton,Michael S Fuge,Craig D Dunseth,Chandra N Roy,Shawn M Hayden,Joshua T Wollen,Kripa Sreepada

The values of the second dissociation constant, pK(2), and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55 degrees C including 37 degrees C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I = 0.16 mol.kg(-1). Conventional pa(H) values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37 degrees C after correcting the liquid junction potentials with the flowing junction cell.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2014-06-06

The densities of aqueous mixtures of aminoethylethanolamine (CAS #000111-41-1) were measured over the entire compositional range at temperatures of 283.15-343.15 K. The results of these measurements were used to calculate excess molar volumes and isobaric thermal expansion coefficients, and partial molar and apparent molar volumes and excess isobaric thermal expansion coefficients were subsequently derived. The excess molar volumes were correlated as a function of the mole fraction using the Redlich-Kister equation. Temperature dependences of the Redlich-Kister coefficients are also presented. The partial molar volumes at infinite dilution of AEEA in water were determined using two different methods. In addition, the solution density was correlated using a Joubian-Acree model. Aqueous solutions of AEEA exhibit similar properties to the aqueous solutions of other alkanolamines (like monoethanolamine) used in acid gas sweetening.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2014-02-25
Magdalena Tyczyńska,Małgorzata Jóźwiak

The density of 15-crown-5 ether (15C5) solutions in the mixtures of N,N-dimethylformamide (DMF) and water (H2O) was measured within the temperature range 293.15-308.15 K using an Anton Paar oscillatory U-tube densimeter. The results were used to calculate the apparent molar volumes (VΦ ) of 15C5 in the mixtures of DMF + H2O over the whole concentration range. Using the apparent molar volumes and Redlich and Mayer equation, the standard partial molar volumes of 15-crown-5 were calculated at infinite dilution ([Formula: see text]). The limiting apparent molar expansibilities (α) were also calculated. The data are discussed from the point of view of the effect of concentration changes on interactions in solution.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-12-10
Yihua Li,Wenge Yang,Tuan Zhang,Chaoyuan Wang,Kai Wang,Yonghong Hu

Solubility data were measured for omeprazole sulfide in ethanol, 95 mass-% ethanol, ethyl acetate, isopropanol, methanol, acetone, n-butanol and n-propanol in the temperature range from 280.35 to 319.65 K by employing the gravimetric method. The solubilities increase with temperature and they are in good agreement with the calculated solubility of the modified Apelblat equation and the λh equation. The experimental solubility and correlation equation in this work can be used as essential data and model in the purification process of omeprazole sulfide. The thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were calculated using the van't Hoff equation.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-12-10
Anna Mozrzymas

Modelling of the critical micelle concentrations (cmc) using the molecular connectivity indices was performed for a set of 21 cationic gemini surfactants with medium-length spacers. The obtained model contains only the second-order Kier and Hall molecular connectivity index. It is suggested that the index 2χ includes some information about flexibility. The obtained model was used to predict log10 cmc of other cationic gemini surfactants. The agreement between calculated and experimental values of log10 cmc for the gemini surfactants that were not used in the correlation is very good.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-12-10
Hideshi Maki,Masahiko Tsujito,Makoto Sakurai,Tetsuji Yamada,Hiroyuki Nariai,Minoru Mizuhata

ABSTRACT The stability constants of ML-type complexes of the two linear triphosphate ligand anion analogues triphosphate ([Formula: see text]) and diimidotriphosphate ([Formula: see text]) were investigated thermodynamically using potentiometric titrations according to Schwarzenbach's procedure. The stability constants of the ML-type complexes of different divalent metal ions with [Formula: see text] are larger than those of the corresponding complexes with [Formula: see text] because of the greater basicity of the imino group. The order of the stability constants for the ML-type complexes follows the Irving-Williams order, indicating that only non-bridging oxygen atoms are coordinated directly to the different metal ions in both ligands, and that the imino groups cannot participate in coordination to the metal ions. In the complexation reactions of the Ca2+, Sr2+, Ba2+-[Formula: see text] and Cu2+, Zn2+, Ni2+-[Formula: see text] systems, each metal ion forms an enthalpically stable complex, and there was no suggestion of a conspicuous entropic effect based on the chelate effect. Monodentate complexes that are strongly coordinated with the ligands were therefore formed, whereas entropically stable bidentate complexes were formed in the complexation reactions of the Cu2+, Zn2+, Ni2+-[Formula: see text] and Ca2+, Ba2+, Sr2+-[Formula: see text] systems. According to the HSAB concept, hard metal cations such as Ca2+, Ba2+ and Sr2+ should bind to the harder oxygen atoms rather than the softer nitrogen atoms of the imidopolyphosphate anions, preventing direct coordination to the imino nitrogen atom. GRAPHICAL ABSTRACT

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-11-26
M A El-Gahami,H M Albishri

Equilibrium studies in aqueous solution are reported for dibutyltin(IV) (DBT) complexes of the zwitterionic buffers "Good's buffers" Mes and Mops. Stoichiometric and formation constants of the complexes formed were determined at different temperatures and ionic strength 0.1 mol·L-1 NaNO3. The results show that the best fit of the titration curves were obtained when the complexes ML, MLH-1, MLH-2 and MLH-3 were considered beside the hydrolysis product of the dibutyltin(IV) cation. The thermodynamic parameters ΔHo, ΔSo and ΔGo calculated from the temperature dependence of the formation constant of the dibutyltin(IV) complexes with 2-(N-morpholino)ethanesulfonic acid (Mes) and 3-(N-mor-pholino)-propanesulfonic acid (Mops) were investigated. The effect of dioxane as a solvent on the formation constants of DBT-Mes and DBT-Mops complexes decrease linearly with the increase of dioxane proportion in the medium. The concentration distribution of the various complexes species was evaluated as a function of pH.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-11-26
K G Sekar,R V Sakthivel

The kinetics of oxidation of cyclanols, viz., cyclohexanol, cyclopentanol, cycloheptanol and cyclooctanol by quinaldinium fluorochromate has been studied in aqueous acid medium at 313 K (±0.1 K). The cyclanols were converted to the corresponding cyclic ketones. The order of reaction was found to be one with respect to oxidant and fractional with respect to the substrate and hydrogen ion concentrations. Increase in the percentage of acetic acid increases the rate of reaction. The reaction mixture shows the absence of any free radicals in the reaction, which has ruled out the possibility of a one-electron transfer during the addition of acrylonitrile. The reaction has been studied at four different temperatures and the activation parameters were calculated. From the observed kinetic results a suitable mechanism was proposed. The relative reactivity order was found to be cyclohexanol < cyclopentanol < cycloheptanol < cyclooctanol. This was explained on the basis of I-strain theory.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-09-17
Katarzyna Lewandowska

The viscosity behavior of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B), such as chitosan/poly(vinyl alcohol) (Ch/PVA) and microcrystalline chitosan/poly(vinyl alcohol) (MCCh/PVA), have been investigated at 25 °C. The intrinsic viscosity and the viscosity interaction parameter of each polymer in 0.1 mol·dm-3 CH3COOH/0.2 mol·dm-3 NaCl solution as well as the ternary systems (polymer A/polymer B/solvent) have been determined and have served for estimation of the miscibility of different polymer mixtures by means of the method of classical dilution. By comparing the experimental and ideal viscosity data it is clearly seen that the satisfaction of the miscibility criterion depends on the definition of the ideal parameter [Formula: see text]. If the [Formula: see text] parameter is defined according to the Krigbaum-Wall criterion and Garcia criterion, the investigated blends of Ch/PVA satisfy the miscibility criterion. In the case of MCCh/PVA blends, the polymeric components show poor miscibility. Additionally, the viscosity results show that the degree of miscibility depends on the molecular weight of chitosan and on the degree of PVA hydrolysis.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-06-14

ABSTRACT The stepwise protonation constants of two linear triphosphate ligand anions, triphosphate, [Formula: see text] and di-imidotriphosphate, [Formula: see text], were investigated by potentiometric titration, and the intrinsic chemical shifts of the stepwise protonated species of these anions were determined from the pH-dependence of the 31P NMR chemical shifts. All stepwise protonation constants of [Formula: see text]were found to be larger than those of [Formula: see text], and the 31P NMR signals due to P3O8(NH)2 always appeared at a lower magnetic field compared to the signals due to P3O10. These results indicate higher basicity of the P3O8(NH)2 ligand, because it contains two imino groups in the ligand molecule. The 31P NMR signals for the end phosphate groups appear at a lower magnetic field than those for the middle phosphate groups, indicating that the basicity of the end phosphate group is higher than that of the middle phosphate group. It can be expected that the high basicity of the P3O8(NH)2 ligand brings about the formation of high stability complexes with various metal ions. Furthermore, the only 31P NMR signal due to the middle phosphate group of P3O8(NH)2 ligand molecule clearly showed a low-field shift in the range of pH < 2.5. The reason for this peculiar low-field shift should be the change of the localization of imino protons around the nitrogen atom in P3O8(NH)2. GRAPHICAL ABSTRACT

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-06-14

Densities of pure 1-butyl-3-methylimidazolium methylsulfate, [C4mim][MeSO4], and its mixtures with methanol have been measured. Measurements were made with an accuracy of ±0.2 kg·m-3, using a vibrating-tube densimeter, over the temperature and pressure ranges (283.15-333.15) K and (0.1-35) MPa, respectively. The experimental densities for the pure ionic liquid and alcohol have been correlated by the Tait equation. The results for the {x1[C4mim][MeSO4] + (1 - x1)MeOH} system have been correlated by a van Laar equation involving parameters that are dependent on temperature and pressure. Excess volumes have been obtained directly from the experimental densities, while isobaric expansivities, isothermal compressibilities, and related excess properties were calculated from the correlation equation. Exceptionally strong pressure and temperature influences on these properties were observed.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-06-14
M Gowrisankar,P Venkateswarlu,K Sivakumar,S Sivarambabu

Densities, ρ, viscosities, η, and ultrasonic sound velocities u of pure methyl isobutylketone, diethylketone, cyclopentanone, cyclohexanone, 2-methyl cyclohexanone and those of their binary mixtures with N-methyl aniline were measured at 303.15 K over the entire composition range. These experimental data have been used to calculate the excess volume (VE), deviation in ultrasonic sound velocity (∆u), isentropic compressibility (κs ), intermolecular free length (Lf), excess intermolecular free length ([Formula: see text]), acoustic impedance (Z), excess isentropic compressibility ([Formula: see text]), deviation in viscosity (∆η) and excess Gibbs energy of activation of viscous flow (G*E). The viscosity data have been correlated using three equations proposed by Grunberg and Nissan, Katti and Chaudhri, and Hind et al. The excess/deviations have been fitted by Redlich-Kister equation and the results are discussed in terms of molecular interactions present in these mixtures.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-05-11
Małgorzata Koźbiał,Paweł Gierycz

The aim of the presented work is the comparison of aqueous and 1-octanol solubilities of different acyclovir derivatives and their hydroxypropyl-β-cyclodextrin inclusion complexes. The solubility measurements were carried out at different temperatures over the range 25-45 °C using water, 1-octanol, water saturated with 1-octanol, 1-octanol saturated with water, buffered aqueous solutions (pH = 5.5 and 7.0) and buffered aqueous solutions containing cyclodextrin as solvents. The aqueous solubilities of the compounds are very low but may be enhanced by complexation with hydroxypropyl-β-cyclodextrin, especially if the acyclovir derivatives have aromatic groups which may be included in the cyclodextrin cavity. The values of 1-octanol-water partition coefficients of acyclovir derivatives, obtained using extraction experiments, showed a similar sequence as the solubility results in 1-octanol. Additionally, some molecular mechanics and molecular dynamic calculations were performed to determine optimized structures of acyclovir derivative complexes with β-cyclodextrin treated as a model.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-04-02
Dharshani N Bopege,Matt Petrowsky,Matthew B Johnson,Roger Frech

Self-diffusion coefficient measurements were performed for pure n-alkyl ketone liquids using the pulsed field gradient NMR spin-echo technique. Ionic conductivities and dielectric constants of 0.0055 mol·L-1 tetrabutylammonium trifluoromethanesulfonate in 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, and 2-decanone were also measured. The temperature-dependent conductivities and diffusion coefficients over the range 5-80 °C can be described using the compensated Arrhenius formalism. Compensated Arrhenius equation plots were used to calculate the average activation energy for both sets of data. The average activation energy from conductivity data is approximately equal to that from diffusion data. The data for the pure ketones and ketone-based electrolytes are compared with analogous data for pure n-alkyl acetates and n-alkyl acetate-based electrolytes.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2013-03-14
Andrzej Lewandowski,Lukasz Waligora,Maciej Galinski

The electrochemical behavior of cobaltocenium has been studied in a number of room temperature aprotic ionic liquids. Well defined, diffusion controlled, anodic and cathodic peaks were found for the Cc+/Cc (cobaltocenium/cobaltocene) reduction/oxidation on gold, platinum and glassy carbon electrodes. Values of the peak separation parameters suggest quasireversibility or even irreversibility for the redox process. The difference between the ferrocene/ferrocenium and cobaltocenium/cobaltocene couples has been evaluated as equal to (1.350 ± 0.020) V. Values of the cobaltocenium (Cc+) diffusion coefficients D have been calculated on the basis of the Randles-Sevcik equation.

更新日期：2019-11-01
• J. Solut. Chem. (IF 1.039) Pub Date : 2012-12-18
Aleksandra Chodzińska,Anna Zdziennicka,Bronisław Jańczuk

From measurements of the surface tension, density, viscosity and light scattering of aqueous solutions of methanol, ethanol and propanol at 293 K, their activity in the surface monolayer, surface excess concentration, and apparent and partial molar volume were determined. The surface excess concentration of alcohols at the water-air interface was determined from the Gibbs equation by using both the alcohol's activity and their molar fraction in the bulk phase and recalculated by using the Guggenheim-Adam equation. The values of the surface excess concentration determined from the Gibbs equation were also applied to determine the standard Gibbs energy of alcohol adsorption at the water-air interface from Langmuir's equation and compared to those determined from that of Aronson and Rosen. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10953-012-9935-z) contains supplementary material, which is available to authorized users.

更新日期：2019-11-01
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