Ionic mobilities and hydrophobic interactions in Ph4PCl-NaCl mixtures in hydroorganic solvents

The aim of this work is to correlate the experimental conductimetric ionic behavior with the hydrophobic properties of the Ph₄P⁺ ion. Ionic mobility determinations using radioactive tracers have been extended to Ph₄PCl-NaCl mixtures at a constant 0.5 molar total salt concentration over the whole range of electrolyte mixture composition. Molar conductance measurements have been carried out in water and in H₂O — 5 mole percent acetonitrile and H₂O — 5 mole percent dimethylsulfoxide. Deviations from the additivity law have been found to be maximum for a 0.6 mole fraction of Ph₄PCl. Large negative mixture effects, up to –27% in H₂O have been measured for the limiting case of a cation in trace amounts. The main experimental result is the decrease of the Ph₄P⁺ mobility with increasing proportion of Na⁺ ions in the mixture. The unexpected negative sign of the mixture effect for the less mobile cation is interpreted in terms of solute-solvent hydrophobic interactions and solvent structure. A possible dimerization of the Ph₄P⁺ ion is suggested. Densities of NaCl and Ph₄PCl in the aquo-organic solvents are also included.     

Thiophene separation from aliphatic hydrocarbons using the 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid

The ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate has been tested as solvent for the separation of thiophene from aliphatic hydrocarbons. Liquid–liquid equilibrium data have been determined for ternary systems containing the ionic liquid, thiophene and C₆, C₇, C₁₂ or C₁₆ alkanes at T = 298.15 K. The performance of the ionic liquid as solvent in such systems has been evaluated. The experimental data were correlated using the NRTL and UNIQUAC equations, and the binary interaction parameters have been reported. The phase diagrams for the ternary mixtures including both the experimental and calculated tie-lines have been presented.     

Nd3+ and Am3+ ion interactions with sulfate ion and their influence on NdPO4(c) solubility

The effects of Nd(III)/Am(III) complexation with sulfate were studied by 1) re-examining existing data for the Am–SO₄ system using more, advanced aqueous electrolyte models valid to high concentration to obtain reliable thermodynamic data for SO ₄ ^2– complexes or ion interactions with Nd³⁺ and Am³⁺ and 2) conducting experimental solubility studies of NdPO₄(c), an analog phase of AmPO ₄ (c), a possibly important phase in high level nuclear wastes, in the presence of SO ₄ ^2– to test the newly developed thermodynamic model and show the possible influence of sulfate in a repository environment. The data showed that the increase in the solubility of NdPO ₄ (c) resulted primarily from the increase in ionic strength. Slightly higher observed Nd concentrations in the presence of sulfate, as compared with concentrations predicted at the experimental ionic strengths, resulted from the weak complexes or ion interactions involving Nd ³⁺ –SO ₄ ^2– . The Pitzer ion interaction parameters, applicable to 0.5m sulfate, were obtained for Am ³⁺ –SO ₄ ^2– from a reinterpretation of known solvent extraction data. These parameters are also consistent with literature data for Am ³⁺ /Na⁺ exchange and solvent extraction in the presence of sulfate. When used for the analogous Nd ³⁺ –SO ₄ ^2– system to predict NdPO ₄ (c) solubility in the presence of sulfate, they provided excellent agreement between the predicted and the observed solubilities, indicating that they can be reliably used to determine Nd ³⁺ or Am ³⁺ ion interactions with SO ₄ ^2– in all ground waters where SO ₄ ^2– is less than 0.5m     

Volumetric properties of dilute aqueous solutions of cobalt-amine-type salts. Part I. Densities at 25°C

The densities of dilute aqueous solutions of [CoL₃]X₃ [L=1,2-diaminoethane(en), 1,2-diaminopropane(pn), 1,3-diaminopropane(tn) X=Cl^–, Br^– and (ClO₄)^–] have been measured at 25°C from 0 to 5×10^–2m. The apparent molar volumes were calculated and extrapolated to infinite dilution. Ion-solvent interactions were detected from the change of the ionic partial molar volumes with concentration. These interactions depend both on the properties of the ion (polarization charge density at the surface, hydrophobic groups, etc.) and the characteristics and structure of the solvent.     

Tracer diffusion of Co2+ ions in agar gel containing multi-electrolyte systems

Tracer diffusion coefficients of cobalt ions have been measured in the supporting medium containing multi-electrolyte systems of alkali bromides. The electrolyte concentration was varied between 10^–6-0.1M at 25°C and the diffusion coefficients were determined by zone-diffusion technique using agar gel medium. The trend in the theoretical values of diffusion coefficients is accounted for by considering the relative contribution of mobility function, ionic strength as well as ion size parameter to the theoretical value in different systems. While the deviations between theoretical and experimental values of diffusion coefficients are explained on the basis of various co-occurring effects in ion-gel-water system.     

Transport and Conduction Properties of Solid Electrolyte CuCl–CdCl2 in the Region of Solid Solutions

In quasi-binary salt system CuCl–CdCl₂ where CuCl is the basis compound and CdCl₂ is the additive, maximum values of electroconductivity, ion transport number, and diffusion coefficient are determined at 20–30 mol % CdCl₂, which points to a maximum ionic disordering. Character of ionic disordering is discussed and predominant conduction by copper(I) ions is proved. X-ray diffraction analysis shows the formation of CuCl-based solid solutions at 20–30 mol % CdCl₂. The current efficiency is close to 100%, which guarantees that Faraday's laws are obeyed during coulometric titration of CuCl–CdCl₂ of optimum compositions in cells containing a solid electrolyte. The CuCl–CdCl₂ system is found to have good ceramic properties. Electrolytic and working characteristics can be stabilized at low temperatures by decreasing hydrolyzability and oxidizability of the solid electrolyte after adding a dopant.     

Molar Volumes and Heat Capacities of Electrolytes and Ions in Nonaqueous Solvents: 1. Formamide

Apparent molar volumes and heat capacities of 27 electrolytes have been measured as a function of concentration in formamide at 25°C using a series-connected flow densimeter and Picker calorimeter system. These data were extrapolated to infinite dilution using the appropriate Debye–Hückel limiting slopes to give the corresponding standard partial molar quantities. Ionic volumes and heat capacities at infinite dilution were obtained by an appropriate assumption based on the reference electrolyte Ph₄PBPh₄ (TPTB). The ionic volumes, but not the heat capacities, agree reasonably well with previously published statistically based predictions. The values obtained are discussed in terms of simple models of electrolyte solution behavior and a number of interesting features are noted, including, possible dependencies of ionic volumes on solvent isothermal compressibility and of ionic heat capacities on solvent electron acceptor abilities.     

Thermodynamics of Aqueous Diethylenetriaminepentaacetic Acid (DTPA) Systems: Apparent and Partial Molar Heat Capacities and Volumes of Aqueous H2DTPA3−, DTPA5−, CuDTPA3−, and Cu2DTPA− from 10 to 55°C

Apparent molar heat capacities and volumes have been determined for aqueous solutions of the mixed electrolytes Na₅DTPA + NaOH, Na₃CuDTPA + NaOH, and NaCu₂DTPA + NaOH, and the single electrolyte Na₃H₂DTPA (DTPA=diethylenetriaminepentaacetic acid) at temperatures from 10 to 55°C. The experimental results have been analyzed in terms of Young's rule with the Guggenheim form of the extended Debye–Hückel equation and the Pitzer ion-interaction model. These calculations led to standard partial molar heat capacities and volumes for the species H₂DTPA^3–(aq), DTPA^5–(aq), CuDTPA^3–(aq), and Cu₂DTPA^–(aq) at each temperature. The partial molar properties at 0.1 m ionic strength were also calculated. The standard partial molar properties were extrapolated to elevated temperatures with the revised Helgeson–Kirkham–Flowers (HKF) model. Values for the partial molar heat capacities from the HKF model have been combined with the literature data to estimate the ionization constants of H₂DTPA^3–(aq) and the formation constant of the CuDTPA^3–(aq) copper complex at temperatures up to 300°C.     

Influencing of the migration time in CZE

For selective influencing of the ion mobility in CZE several electrolyte additives were used. With acetone as organic solvent the migration times of inorganic cations are changed. The separation of Cl^– and I^– is optimized by adding -cyclodextrin to the electrolyte. By adding 18-crown-6 it is possible to slow down the mobility of K⁺. In this way the disturbing effect of matrix ions can be prevented.     

Conductance behavior of 1∶1 electrolytes in N,N-dimethylmethanesulfonamide

The conductances of eleven 1:1 salts have been measured at 50°C in N,N-dimethylmethanesulfonamide (DMMSA) for electrolyte concentrations of 1.2–55.0×10^–4 mol-dm^–3. The conductance data were analyzed using the equation of Lee and Wheaton. Calculations for different values of the distance parameter R indicate that all salts studied are only slightly associated in DMMSA. Association was somewhat greater for the trimethylphenylammonium halides than for the tetraalkylammonium salts. Ionic limiting molar conductances were estimated using the tris (isopentyl) butylammonium tetraphenylborate approximation. The markedly smaller value for _o (Na⁺) compared to the values for _o (Br^–) and _o (I^–) indicates that the sodium ion is probably more extensively solvated than the halide ion. In general, it appears that DMMSA (dielectric constant=80.31 at 50°C) is similar in its solvent properties to dipolar aprotic heterocyclic solvents such as 2-cyanopyridine and 3-methyl-2-oxazolidone which have similar dielectric constants.     

The adsorption theory of electrolytes and the volumetric properties of some nitrate-water systems. From fused salts to dilute solutions

Summary On the basis of theBrunauer-Emmet-Teller adsorption model extended byStokes andRobinson to concentrated electrolyte solutions, from theStokes-Robinson equation for water activity, and from theAbraham equation for electrolyte activity,Ally andBraunstein have derived equations for the partial excess molar volumes of salt and water in salt-water systems. In their equations, only oneBET parameter is considered to be pressure dependent. In the present publication, complete equations are proposed, taking into account the dependence of bothBET constants on pressure. These equations are tested successfully with nitrate-water systems containing mono and divalent cations over a concentration range from fused salts to water: [0.500 LiNO₃–0.500 KNO₃+H₂O], [0.467 TlNO₃–0.214 CsNO₃–0.319 Cd (NO₃)₂+H₂O], [N(C₂H₅)₄NO₃+H₂O], [0.515 AgNO₃–0.485 TlNO₃+H₂O], and [AgNO₃–TlNO₃–M(NO₃) _n +H₂O] (M=Na, K, Cs, Cd, Ca;x(AgNO₃)/x(TlNO₃) as in the preceding systemx(M) being varied from 0.025 to 0.125 depending on the cation). Additivity rules which involve the partial derivatives of theBET constants with respect to pressure are also proposed.

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Adsorptionstheorie der Elektrolyte und volumetrische Eigenschaften einiger Nitrat-Wasser-Systeme. Von Salzschmelzen zu verdünnten Lösungen

Zusammenfassung Auf der Basis desBrunauer-Emmet-Teller-Modells, vonStokes undRobinson für konzentrierte Elektrolytlösungen erweitert, sowie ausgehend von den Gleichungen nachStokes-Robinson für die Aktivität von Wasser und nachAbraham für dieAktivität von Elektrolyten, leitetenAlly undBraunstein Beziehungen für die partiellen molaren Zusatzvolumina von Salz und Wasser in Salz-Wasser-Systemen her, in denen nur einBET-Parameter als druckabhängig behandelt wird. In der vorliegenden Publikation werden vollständige Gleichungen vorgestellt, die die Druckabhängigkeit beiderBET-Konstanten berücksichtigen und die erfolgreich an Nitrat-Wasser-Systemen getestet wurden, die mono- und divalente Kationen enthalten und deren Konzentrationsbereich von Salzschmelzen bis zu reinem Wasser reicht: [0.500 LiNO₃–0.500 KNO₃+H₂O], [0.467 TlNO₃–0.214 CsNO₃–0.319 Cd(NO₃)₂+H₂O], [N(C₂H₅)₄NO₃+H₂O], [0.515 AgNO₃–0.485 TlNO₃+H₂O] und [AgNO₃-TlNO₃-M(NO₃) _n +H₂O] (M=Na, K, Cs, Cd, Ca;x(AgNO₃)/x(TlNO₃) wie im vorhergehenden System:x(M) je nach Kation zwischen 0.025 und 0.125). Zusätzlich werden Additivitätsregeln, die sich auf partielle Ableitungen derBET-Parameter bezüglich des Drucks beziehen, vorgestellt.

     

The system HCl+InCl3+H2O from 5 to 55°C: Application of Harned's rule

Electromotive-force measurements of cells containing hydrochloric acid and indium chloride have been made to determine the variation of the log of the activity coefficient of hydrochloric acid with change in the amount of indium chloride in the solution. The simpler Harned equations have been used to fit the data. The quadratic terms in the Harned equations for the activity coefficients of HCl in the salt mixtures are required for a good fit of the 968 experimental emf data points at all the experimental ionic strengths and temperatures. The more convenient Pitzer ion-interaction treatment of the data will be reported in a separate publication which will include the values of the Pitzer parameters for pure InCl₃(aq), and mixing parameters for H⁺–In⁺³ and H⁺–In⁺³–Cl^–. A comprehensive investigation on the mixed electrolyte solutions at 11 different constant total ionic strengths ranging from 0.05 to 3.5 mol-kg^–1 was made at 11 temperatures from 5 to 55°C using the cell without liquid junction of the type: Pt,H₂(g, 1 atm)|HCl(m _A)+InCl₃(m _B)+H₂O|AgCl,AG (A).     

A test of the onsager reciprocal relations and a discussion of the ionic isothermal vector transport coefficientsI Ij for aqueous AgNO3 at 25°C

Values ofI _ij calculated from experimental data are given for AgNO₃ at 25°C. Experimental values of the ratioI ₁₂/I₂₁ are calculated to provide a sensitive direct test of the Onsager reciprocal relations,I ₁₂=I₂₁. This ratio is found to be unity within experimental error (ca. 2%). The general physical interpretation ofI _ij/N as mobilities is discussed. An approximate way of estimatingI _ij for dissociated salts is considered. A comparison is made between AgNO₃ I _ij data and corresponding data for NaCl and KCl. It is concluded that ion-pair formation (1) sharply increases the magnitude of the interaction mobility,I ₁₂/N; and (2) increases the intrinsic mobility of Ag⁺,I ₁₁/N, and decreases the intrinsic mobility of NO ₃ ^– ,I ₂₂/N.     

The EDTA complexes of astatine

Using the electromigration method the monopositive astatine ion has been shown to form EDTA [H₄L] complexes in 0.1M NaClO₄ solution at pH=3–10. The ion mobility of the AtL^3– complex is 5.60/23/x10^–4 cm².V^–1.s^–1.     

Hygrometric Determination of Water Activities and Osmotic and Activity Coefficients of NH4Cl–KCl–H2O at 25°C

Relative humidities have been measured for mixed aqueous electrolyte system of ammonium and potassium chlorides by the hygrometric method at total molalities from 0.3 to 6 mol-kg^–1for ionic-strength fractions yof NH₄Cl of 1/3, 1/2, and 2/3 at 25°C. The data allow the calculation of new water activities and osmotic coefficients. The proposed ECA (extended composed additivity) rule of calculation of water activity in mixed aqueous electrolyte solutions from the water activities of a single component is extended to this system. The experimental results and the predictions of the ECA rule are compared with the Robinson–Stokes, Reilly–Wood–Robinson, the Pitzer, and the Lietzke–Stoughton II models. Predictions made using these models are, in general, consistent with our results. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture for different ionic-strength fractions.     

Equilibrium and Transport Properties of Sodium n-Octyl Sulfonate Aqueous Solutions

Measurements of osmotic coefficients, mutual diffusion coefficients, and conductivity were performed on the binary system sodium n-octyl sulfonate (C₈SO₃Na)–water at 25°C both below and above the micellar composition range. The osmotic coefficient data were obtained through vapor-pressure osmometry, while the Taylor dispersion method was used to measure diffusion coefficients. The mass equilibrium model was applied to this self-aggregating system, taking into account the deviation of the activity coefficients from the Debye–Hückel limiting law by using the Guggenheim corrective terms for mixed electrolyte solutions. The expressions derived from the model fit the experimental osmotic and diffusion coefficient data well, when the same values of aggregation number, fraction of condensed counterions, and equilibrium constant are used. Osmotic coefficients were also used to determine the thermodynamic factor required to compute the solute mobility from diffusion data. Conductivity data were used to test two theoretical models, namely, the Onsager–Fuoss and the Mean Spherical Approximation theories. Both models have been found to yield unsatisfactory fits to our experimental data and some arbitrary terms had to be applied to the theoretical expressions to obtain good agreement between experiment and theory.     

Unimolecular rearrangement of α-silylcarbenium ions. An ab initio study

The unimolecular rearrangements of hydrogen, methyl and phenyl groups at the Si atom in α-silylcarbenium ions have been investigated using an ab initio molecular orbital method. MP2/6–31 + G^*//HF/6–31G^* calculations predict that all three groups migrate from the Si to an adjacent C_α with no energy barrier. Thus, the silicenium ion is the only stable species in each potential energy surface. The conformation of the benzylsilicenium ion, (C₆H₅)CH₂−SiH₂⁺, indicates that the phenyl ring is significantly bent toward the silyl cationic center in order to interact with the vacant 3p(Si⁺) orbital. In contrast to MP2 results, Hartree-Fuck calculations (both HF/3–21G^* and HF/6–31G^* levels) predict small energy barriers for 1,2-migrations of H and Me (1.4 kcal mol⁻¹ for H migration, and 1.5 kcal mol⁻¹ for Me migration, respectively, at the HF/6–31G^* level). This difference provides convincing evidence that the incorporation of electron correlation is of particular importance in describing the potential energy surface for the rearrangement of α-silylcarbenium ions to silicenium ions. The results of the calculations have also been applied to the possible rearrangement mechanism of α-chlorosilanes to chlorosilanes, assuming that the experimental conditions are favorable toward the generation of ionic species. Various factors which may govern the migratory aptitudes of various R groups, i.e. (1) activation energies, (2) overall reaction energies and (3) the conformational preference of reactants have been investigated. The calculated activation energy obtained, namely the energy for the generation of the silicenium ion and the C⁻¹ ion from an α-chlorosilane, is consistent with the experimental migratory aptitude in the gas phase observed in mass spectrometers.     

Viscosity of aqueous mixtures of silver and thallium nitrates with calcium or cadmium nitrates from pure fused salt to pure water

Fused salt-water systems extending from pure fused salt to pure water have been less studied than dilute aqueous solutions, despite their practical and theoretical importance. Even fewer studies have been made regarding the influence of the temperature upon transport properties. The present publication brings new interesting information on the viscous flow properties of the following two fused nitrate-water systems containing monovalent and divalent cations: AgNO₃–TINO₃–M(NO₃)₂–H₂O where M=Ca or Cd, with the TINO₃ and M(NO₃)₂ mole fractions in the anhydrous salt fixed at 0.436 and 0.100, respectively. The parameters in the Arrhenius, Eyring, Batschinski and the Abraham and Abraham equations are found to be well correlated with the properties of the components of the melts. The temperature effect allows a discussion to be made in terms of structural features such as holes and free volumes.     

Thermodynamic Aspects of Metal–Ion Complexation in the Structured Solvent, <Emphasis Type="Italic">N</Emphasis>-Methylformamide

Chloride complexation of cobalt(II), nickel(II) and zinc(II) ions has been studied by calorimetry and spectrophotometry in N-methylformamide (NMF) containing 1.0 mol-dm^{− 3} (n-C₄H₉)₄NClO₄ as an ionic medium at 298 K. A series of mononuclear complexes, MCl_n^{(2 -n) +} (M=Co, Ni and Zn) with n = 1, 3 and 4 for cobalt(II), n = 1 for nickel(II), and n = 1–4 for zinc(II), are formed and their formation constants, enthalpies and entropies were obtained. It revealed that complexation is suppressed significantly in NMF relative to that in N,N-dimethylformamide (DMF) in all metal systems examined. The suppressed complexation in NMF is mainly ascribed to the smaller formation entropies in NMF reflecting that the solvent–solvent interaction or solvent structure in the bulk NMF is much stronger than that in the bulk DMF. Formation entropies, Δ S₁^o, of the monochloro complex in DMF, dimethyl sulfoxide and NMF are well correlated with the Marcus’ solvent parameter, Δ Δ_v S^o/R, according to Δ S₁^o/R = aΔ Δ_v S^o/R+b. The a value is negative and similar in all metal systems examined, whereas the b value depends on the metal system. When a gaseous ion is introduced into a solvent, the ionic process of solvation is divided into two stages: the ion destroys the bulk solvent structure to isolate solvent molecules at the first stage and the ion then coordinates a part of isolated solvent molecules around it at the second stage. We propose that the a and b values may reflect the changes in the freedom of motion of solvent molecules at the first and second stages, respectively, of the ionic process of solvation.     

Electromigration of carrier-free radionuclides

The electromigration behaviour of carrier-free²⁴¹Am–Am(III) in inert electrolytes, =0.1 (C10 ₄ ^– ), T=298.1(1) K, was studied. On the basis of the overall ion mobilities of²⁴¹Am–Am(III) on pH between pH 5.5 and 12.9, the stoichiometric hydrolysis constants p ₃ ³ =23.8(9), and pK₁=6.9(2) were obtained. For K₄ a limitation of pK₄14.4(3) was possible, because no formation of anionic hydrolysis products in solutions pH12.9 was registered. The individual ion mobility of the²⁴¹Am–Am³⁺ decrease in the range pH 5.5–3 from +6.85(15) up to +5.50(15)·10^–4 cm²·s^–1·V^–1. Dependences of this effect on overall ionic strength, inert electrolyte anion, and the temperature of the electrolytes were studied in acidic and neutral solutions.