Activity coefficients of NaCl in PEG 4000 + water mixtures at 288.15, 298.15 and 308.15 K

The electromotive force of the cell containing two ion-selective electrodes (ISE),

Na-ISE|NaCl (m), PEG ??4000 (Y), H₂O (100−Y)|Cl-ISE$\text{Na-ISE}|\text{NaCl}(m),\text{PEG}\text{\hspace{0.17em}??}4000(Y),{\text{H}}_2\text{O}(100-Y)|\text{Cl-ISE}$

Activity coefficients of KCl in PEG 4000 + water mixtures at 288.15, 298.15 and 308.15 K

The electromotive force of the cell containing two ion-selective electrodes (ISE), K-ISE|KCl(m), PEG 4000(Y), H₂O(100 − Y)|Cl-ISE has been measured at temperatures of 288.15, 298.15, and 308.15 K as a function of the weight percentage Y of PEG 4000 in a mixed solvent. Y was varied between 0 and 25 wt.% in five-unit steps and the molality of the electrolyte (m) was between ca. 0.05 mol kg⁻¹ and almost saturation. The values of the standard electromotive force were calculated using routine methods of extrapolation together with extended Debye-Hückel and Pitzer equations. The results obtained produced good internal consistency for all the temperatures studied. Once the standard electromotive force was determined, mean ionic activity coefficients for KCl, Gibbs energy of transfer from the water to PEG 4000 + water mixtures, interaction parameters (g_EN, h_EN, s_EN, c_p,EN), salting constants, and the KCl primary hydration number were estimated and comparatively discussed in terms of a model of structural and electrostatic interactions with those of the LiCl and NaCl previously obtained in similar mixtures.     

Mean Activity Coefficients of KCI in the KCI-K2B4O7-H2O Ternary System at 308.15 K by EMF Method

The mean activity coefficients of KCI in a KCI-K2B407-H20 ternary system were experimentally determined at 308.15 K by the electromotive force measurement（EMF） via a battery cell without a liquid junction： K-ISEIKCI（m1）, K2B4O7（m2）ICI-ISE（ISE=ion selective electrode） in a total ionic strength of from 0.01 mol/kg to 1.00 mol/kg at different ionic strength fractions of KzB407 with yB=0, 0.200, 0.400, 0.600 and 0.800. K-ISE and CI-ISE presented a good Nernst effect, which implies that this method could be used to measure the activity coefficients of an electrolyte in the above system. The Harned rule was fitted to the experimental data, the Harned coefficients and the Pitzer single-salt ion parameters of KC1 were evaluated, and the relationship diagrams between the mean activity coefficient of KC1 and the ionic strength fraction（yB） were drawn. The mean activity coefficients of KCI（γ±KCI） decreased monotonically with the increase of I. The experimental results obeyed the Harned rule well.     

Activity coefficients for NaBr in aqueous ternary solutions with sodium propionate and butyrate from EMF measurements

The activity coefficients of NaBr in the NaBr–NaPropionate–H₂O and NaBr–NaButyrate–H₂O systems were determined from EMF measurements at constant total ionic strength of 0.1 0.5 1.0 1.5 2.0 and 2.5 mol-kg^–1 and at 25° C. The activity coefficients were fitted using Scatchard, Pitzer and Lim equations. Finally the excess Gibbs free energy of these mixtures were also calculated.     

非化学计量金属间化合物DO3型Fe3Al热力学性质

用以CaF2单晶为固体电解质的电池电动势(EMF)法测定了720～850 K温度区间内(－)Pt|Ir|Al_0.85Sn_0.15,Na₃AlF₆|CaF₂|Al_xFe_1－x(x=0.23～0.33),Na₃AlF₆|Ir|Pt(＋)电池电动势,通过DO₃型Fe₃Al的粉末化以及选用富Al合金Al_0.85Sn_0.15作为参比电极,使电池反应较快地达到热力学平衡,EMF测量前后工作电极的X射线衍射分析证明没有化学变化发生.计算了DO₃型Fe₃Al非化学计量金属间化合物均相范围内组元Al的活度及Al的偏摩尔热力学函数ΔG_Al、ΔH_Al、ΔS_Al ,基于Gibbs-Duhem方程计算了DO₃型Fe₃Al中另一组元Fe的活度和偏摩尔Gibbs自由能.计算了750 K时DO₃型Fe₃Al相中Al的扩散热力学因子,在化学计量比成分(xAl=0.25)附近Fe₃Al相中Al扩散的热力学因子达到最大值.     

Activity coefficients from the emf of liquid membrane cells V. alkaline earth hexacyanoferrates (III) in aqueous solutions at 25°C

The relative mean activity coefficients of the M₃[Fe(CN)₆]₂ salts, M=Mg, Ca, Sr, Ba, are measured down to about 5×10^–6 mol-kg^–1 using the liquid membrane cell method. In the dilute region these salts display negative instead of positive deviations from the limiting law, contrary to Debye-Hückel's theory predictions. An indirect method based on auxiliary emf measurements in MCl₂, K₃Fe(CN)₆ and KCl, rather than a theory-assisted direct extrapolation to zero of the relative activity coefficients, is used to identify the actual values of the activity coefficients. The data are compared with Mayer's theory, ion-pair theory and numerical integration of the Poisson-Boltzmann equation. Best-fit coefficients of Pitzer's equation which meet the activity coefficients of the M₃[Fe(CN)₆]₂ salts to be reproduced, are reported.     

Activity coefficients of NaCl in aqueous mixtures with ɛ-increasing co-solvent: Formamide–water mixtures at 298.15 K

The electromotive force of the cell containing two ion-selective electrodes (ISE),

Na-ISE|NaCl(m), formamide (Y), H₂O(100 − Y)|Cl-ISE

Specific interactions and single-lon activity coefficients in mixed electrolyte solutions

A reexamination of Guggenheim's theory of specific interactions for dilute aqueous electrolyte solutions shows that the parameters of the theory should include terms for interactions between like-charged ions. The equations developed are analogous to those in Pitzer's treatment of concentrated solutions, and the inclusion of ion-solvent interaction parameters allows comparison with the Stokes and Robinson hydration theory treatment. As with hydration theory, specific-interaction theory predicts differences in single-ion activity coefficients.     

Activity coefficients in mixed-electrolyte solutions at 25°C: Na-formate + NaCl system

Activity coefficients for NaCl in aqueous mixtures with Na-Formate were determined at 25°C from emf measurements for different total ionic strengths. At each total ionic strength studied, the measurements were carried out at different ratios of the Na-Formate to NaCl ionic strengths. The experimental activity coefficients were fitted using the Harned equation and the treatments of Scatchard et al. and Pitzer et al. Finally, the excess Gibbs energy of these mixtures was also calculated.     

Osmotic coefficients of vinylic polyelectrolyte solutions without added salt

 The osmotic pressures of –polyelectrolyte solutions without added salt was measured in the concentration ranges 0.001–0.02 and 0.2–1.9 mol kg^-1. Our results show that the osmotic coefficients φ_p were strongly dependent on the chemical structures of polyelectrolyte through the polyion radius and the interaction between the ionic moiety and counterions. The osmotic pressures in polyelectrolyte solutions without added salt, calculated on the basis of the counterion contribution, are in agreement with the experimental results. We conclude that the counterion contribution is dominant in the osmotic pressures and thus, the polymer contribution is negligible in the examined concentration range 0.2–1.9 mol kg^-1. The P–B approach gave a fair prediction of the absolute values of the osmotic pressures with λ=4.5, where λ is the charge density parameter, except for NaPA. In other words, the concentration dependence of the φ_p values can be explained in terms of the counterion contribution. Received: 11 June 1997 Accepted: 19 August 1997     

Activity coefficients of electrolytes from the E.M.F. of liquid membrane cells. II - multicharged electrolyte solutions

The activity coefficients of Co(en)₃Cl₃ and K₂SO₄ were measured by means of a cell with ion-exchange liquid membranes following the method described in paper I. The results prove that this method is even more valuable with multicharged salts than with 1-1 electrolytes. The values obtained are precise and reliable down to dilution limits never before accessible, e.g., 4×10^–5 mol-kg^–1 in Co(en)₃Cl₃. High dilution levels are of particular importance when dealing with highly charged electrolytes since the trend at higher concentrations often leads to errors both in extrapolation to infinite dilution and in the absolute activity coefficients. As an application, the activity coefficients of [Co(en)₃]₂(SO₄)₃-suspected to be wrongly evaluated in past literature-were measured, and their values at low concentrations were actually lower than those quoted before.     

Evaluation of the chronic intoxication of fluoride on human serum metabolome using untargeted metabolomics

Drinking water is the main source of fluoride intake for the human body and its regulated consumption helps in decreasing dental caries. However, excessive fluoride consumption over a prolonged time period causes fluorosis disease which adversely affects many tissues and organs of the body. This paper describes the evaluation of chronic intoxication of fluoride on human serum metabolome. The untargeted metabolomics approach using UPLC-QTOF-MS/MS is applied for metabolomic profiling, whereas the estimation of fluoride in serum samples was carried out using the ion-selective electrode (ISE). Fluoride concentration was found to be 0.16–1.25 mg/L in serum samples of 39 fluorosis patients and 0.008–0.045 mg/L in 20 healthy samples. A total of 47 metabolites were identified based on the high-resolution mass spectrometry analysis. A volcano plot was generated to discriminate features that are significantly different between the fluorosis and healthy groups at the probability of 0.05 and fold change ≥ 2. Among all identified metabolites, intensities of ten differential identified metabolites including inosine, α-linolenic acid, guanosine, octanoyl-L-carnitine, His-Trp, phytosphingosine, lauroyl-L-carnitine, hydrocortisone, deoxyinosine and dodecanedioic acid have been found altered in disease samples compared to healthy controls. Major pathways identified based on these metabolites include energy metabolism, fatty acid oxidation, purine degradation pathway, elevated protein degradation, and increased ω-6 fatty acid linoleate signatures were observed.     

Correlation of infinite dilution activity coefficients of solvents in polymer solutions using connectivity indices

In this work, correlations for the estimation of the infinite dilution activity coefficients of non-polar solvents in polystyrene (PS), poly(vinyl acetate) (PVAc), poly(n-butyl methacrylate) (PBMA), poly(dimethyl siloxane), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinyl chloride) (PVC), polyisobutylene and polyethylene (PE), and that of polar solvents in PS, PVAc, PBMA, PMMA, PEO, PVC and PE are proposed. A total of 205 polymer/non-polar solvent systems with 1708 data points, and 118 polymer/polar solvent systems with 695 data points were used to develop the correlations. The overall average errors were 9.6% and 11.3%, respectively, significantly lower than other predictive models. Since the new correlations require only the connectivity indices of the solvents in the calculations, and the connectivity indices can be calculated easily once the molecular structure of the substance in question is known, they are easy to apply, and are useful for process design and development.     

Investigation of the interaction of HCl and three amino acids,HEPES, MOPSO and glycine,by EMF measurements

Ionic interaction in the three systems Hcl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid), HCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid), and HCl-glycine have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the three systems are calculated from emf measurements of solutions containing HCl and the amino acid in a H₂/solution/AgCl,Ag cell at 25°C. The first dissociation constant of HEPES at 25°C has also been determined using emf and pH titration measurements.     

Activity coefficients of single electrolytes in concentrated solutions derived from a quasi-lattice model

This paper describes a new model to calculate the mean activity coefficients of dissociated electrolytes in concentrated solutions. It is based on three assumptions: (i) a quasi-lattice arrangements of ions in solution; (ii) a contribution from ion-water interactions to the mean activity coefficients; (iii) a concentration dependence of the dielectric constant. The mean activity coefficients of thirteen strong electrolytes from moderately dilute solutions to saturated solutions are found to correlate well by this model. For dilute solutions, a limiting equation in which only ion-specific parameters are required is proposed. It is suggested that specific ionwater interactions might be the major source of the nonideality of strong electrolyte solutions at high concentrations.     

Transference numbers of aqueous NaCl and Na2SO4 at 25°C from EMF measurements with sodium-selective glass electrodes

Transference numbers in aqueous solutions of NaCl and Na ₂ SO ₄ were obtained by measuring the emf of cells with liquid junction using sodium-selective glass electrodes. Transference numbers in the NaCl–H₂O system from about 0.1 to 4 mol-kg ^–1 (m) are in good agreement with literature data obtained by various experimental techniques, but are markedly lower than recent data obtained from emf measurements with Ag,AgCl-electrodes. Transference numbers in the Na ₂ SO ₄ –H ₂ O system from about 0.03 to 1.9 m show a small decrease with increasing salt concentration, which is near the limit of experimental uncertainty. Sodium-selective electrodes are well suited to perform determinations of transference numbers and may provide an alternative to amalgam electrodes.     

Application of Kirkwood-Buff theory to electrolyte solutions. III. Activity coefficients of aqueous NaCl between 273.15 and 573.15 K

Using a theory recently developed for the interpretation of activity coefficients of 1:1 electrolytes up to high concentrations in aqueous solution at 25°C, we have analysed available data for aqueous sodium chloride solutions up to saturation in the temperature range 273.15–573.15 K. The approach, which is based on Kirkwood-Buff theory and uses the truncated Poisson-Boltzmann equation to obtain the required information about the various ion-ion radial distributions, is able to fit the results to high accuracy with minimum of parameters, viz, three, of which one is the distance of closest approach, the other two relate to ion-solvent interactions and/or higher order terms in the ion-ion interaction.     

水-醋酸体系中HCl的热力学性质研究

人们对混合溶剂中的电解质热力学性质虽然已进行了较广泛的实验研究,并提供了许多实验数据,为理论研究提供了方便,但还很不全面,即使象水-醋酸这样的混合溶剂体系,至今尚未见较全面的报道,为此,本文设计了如下电池:玻璃电极(H⁺)|HCl(m),HAc+H₂O|AgCl-Ag并测定该电池的电动势,以了解HCl在水-醋酸中的热力学行为及离子-溶剂相互作用特点。