Ions Of Different Valences Research Articles

Diffusion coefficients of ions through ion excange membrane in Donnan dialysis using ions of different valence

Donnan dialysis with an ion exchange membrane was investigated for ions of different valence. The effective diffusion coefficients ( D e) of various kinds of ions in the membrane were obtained by fitting of the equation derived from the Nernst–Planck equation to three or more sets of experimental data for Donnan dialysis. It became apparent that the value of D e/ D s of monovalent ions (e.g., K + or Na + ions) at z A=1 and z B=2 (feed ions are monovalent ones and driving ions are bivalent ones) remained constant at ca. 1/210 and that of bivalent ions (e.g., Ca 2+, Cu 2+, or Mg 2+ ions) remained constant at ca. 1/526 where D s denotes the diffusion coefficient of ions at infinite dilution in water calculated from the Nernst–Einstein equation, and z A and z B represent the valences of the feed and driving ions, respectively. D e/ D s of monovalent ions (e.g., H +, K +, or Na + ions) at z A=2 and z B=1 (feed ions are bivalent ones and driving ions are monovalent ones) was constant at ca. 1/23.3 and that of bivalent ions remained constant at ca. 1/58.4. It was proved that D e/ D using D e at z A=1 and z B=2 was constant at 1/3.0 and that at z A=2 and z B=1 remained constant at 3.0 where D represents the diffusion coefficient of ions in the membrane at z A= z B (the valences of both feed and driving ions are equal). Therefore, it was found that a large flux of ions could be obtained using the monovalent driving ions in Donnan dialysis. On the other hand, the small flux can be obtained using bi- or higher-valent driving ions.

Absorption spectra and luminescence of oxygen-deficient centres in a titanosilicate glass synthesised in a steady laser plume. I. Absorption spectra

The absorption spectra of titanosilicate glasses with the titanium concentration ∼ 0.1 — 3% by weight were investigated in the wavelength range 225 — 460 nm. These glasses were synthesised in a steady laser plume in an atmosphere of air or nitrogen at normal pressure. Synthesis in these two atmospheres gave rise to Ti ions of different valence in the glasses. For the same Ti concentration the intensity of the characteristic absorption bands of titanium in its reduced states (Ti2+, Ti3+) with maxima at λ ∼ 278 and 306 nm were 3 — 6 times higher when the synthesis took place in nitrogen. The enhancement of the 278 nm band was approximately half that of the band at 306 nm. Clear-cut strong absorption in the UV range at 260 — 280 nm as well as strong absorption in the visible range at 400 — 500 nm, observed for the first time for titanium-doped silica glass, were the results of a record-high concentration of Ti3+ ions, compared with the concentrations found in bulk glass samples prepared by other technologies such as melting, reduction of Ti4+ ions, and plasma hydrolysis.

Optical spectra and photoconductivity of uranium-doped CaF 2 crystals

Using infrared and optical absorption spectroscopy in combination with photoconductivity measurements on uranium-doped calcium fluorite crystals, we clarify a controversy in the assignment of U 2+ and U 4+ ion valences in CaF 2 crystals which exhibit different coloration. The energy thresholds of donor-like processes (photoionization) follow the sequence of ionization potentials for uranium ions of different valences and indicate the green and yellow colors to be due to U 4+ of different charge compensation.

Photophysical and Photochemical Properties of Three-Dimensional Metal-Tris-Oxalate Network Structures

Abstract Chemical variation and combination of metal ions of different valencies in the oxalate backbone as well as in the tris-bpy cation of the three-dimensional network structures of the type [MII 2(ox)3][MII(bpy)3] (bpy = 2,2′-bipyridine, ox = C2O4 2-), [MIMIII(ox)3][MII(bpy)3] and [MIMIII(ox)3][MIII(bpy)3]ClO4 offer unique opportunities for studying a large variety of photophysical processes. Depending upon the relative energies of the excited states of the chromophores, excitation energy transfer either from the tris-bipyridine cation to the oxalate backbone or vice versa is observed, as for instance from [Ru(bpy)3]2+ as photo-sensitiser to [Cr(ox)3]3- as energy acceptor in the combination [NaCr(ox)3][Ru(bpy)3], or from [Cr(ox)3]3- to [Cr(bpy)3]3+ in [NaCr(ox)3][Cr(bpy)3]ClO4. In addition efficient energy migration within the oxalate backbone is observed. Furthermore, depending upon the excited state redox potentials, light-induced electron transfer processes may be envisaged.

Ion-Selective Membrane Electrodes: A General Limiting Treatment of Interference Effects

It is shown that interference effects exhibited by ion-selective membrane electrodes are given completely by the measurable difference in the electrochemical potential of the species one wishes to sense on the two sides of the membrane. A general expression for this difference is derived. When used together with general results from nonequilibrium thermodynamics and statistical mechanics, this expression leads to an equation for the dependence of interference effects on test solution composition. This equation should be generally valid under steady state conditions for membranes with fixed or mobile sites whenever the amounts of interfering species in the membrane are everywhere sufficiently small. According to the equation the contribution of species j to the interference potential of a membrane selective to species i varies as aj(ai)-νi/νj, where a denotes activity in the test solution and ν denotes ionic valency, including the sign. All combinations of i and j valencies are covered. When (νi/νj) is positive (negative), the magnitude of the interference potential decreases (increases) with increasing ai at constant aj. It is concluded that two proposed extensions of the well-known Nicolsky equation for ions of different valency are incorrect.

New method for determining the concentration of ionic impurities in solvent polymeric membranes

A new method is proposed for ascertaining the amount of ionic impurities in solvent polymeric membranes of ion-selective electrodes. The method is based on determining the selectivity coefficient for ions of different valences as a function of the concentration of a lipophilized tetraphenylborate salt added to the membrane phase. Thus, the concentration of anionic impurities in commercially available poly(vinyl chloride) and of cationic ones in Tecoflex® (a polyurethane) was obtained as 0.063 ± 0.016 and 0.044 ± 0.006 mmol/kg, respectively.

Existence for 2-Point Boundary Value Problems in Two Ion Electrodiffusion

In this paper we consider the two-point boundary value problem y″=y{λ−(y(0) 2−y 2)/2+[lλ+(y(0) 2−y(1) 2)/2]x} −[lλ+y(0) 2−y(1) 2)/2]D, x∈[0,1], y′(0)=0=y′(1)which arises when two ions with the same valency diffuse and migrate across a liquid junction under the influence of an electric field E. Here y is proportional to the electric field E and, after scaling, the junction occupies the region 0≤x≤1. The parameters l, λ, and D are functions of the physical parameters of the problem and the range of physical interest is l, λ>0, −1< D<1. We consider the case l, λ, D>0. Using the maximum principle we show that positive solutions are strictly decreasing and satisfy y(0)≤ y(1)(1+ l), and that there are no negative solutions. Using Schauder degree theory and upper and lower solutions we show positive solutions exist if [formula]. These results extend and unify those of the author ( Acta Math. Sci. 8, 1988, 373-387). We briefly discuss the corresponding model for two ions of different valencies.

Frequency Dependence of the Membrane Flexoelectric Voltage Response. Adsorption of Multivalent Counterions on the Surface of Curved Lipid Bilayer

Abstract The flexoelectric response of the oscillating membrane for different frequencies is studied. The influence of the adsorption of ions of different valencies on the membrane flexoeffect is considered. Different adsorption mechanisms corresponding to different binding of the electrolyte counterions to the lipid molecules are proposed.

On the partitioning of the viscosity B coefficient and the correlation of ionic B coefficients with partial molar volumes of ions for aqueous and non-aqueous solutions

A new method of partitioning the viscosity B coefficients has been proposed on the basis of the assumption that ionic B values should be a monotonie function of crystal radii cubed, independent of the sign of the charge, for aqueous and various non-aqueous systems. Ionic B values thus obtained in different solvents by a single method of division provide a basis for uniform comparison among themselves as well as with the existing values. The usual assumption of equal contributions of K+ and Cl− ions has been discarded. The internal consistency of the derived set of Bi values is demonstrated by correlation with the ionic radii, hydrated ionic radii, partial molal volumes, temperature coefficient of equivalent conductance, and partial molal ionic entropy. The salient feature of the set of Bi values is noted by its linear relationship not only with the partial molal volumes but the same is also observed with the ionic radii of ions of different valence and charge types. Eyring's equation for viscosity using Frank–Wen's model of ion–solvent interaction has been utilised for the calculation of void viscosity and electrostriction viscosity. The latter is compared with the corresponding component of partial molal volumes using the Drude–Nernst equation based on the continuum model for solvent. Keywords: ion–solvent model, ionic B values, B coefficients, division of B coefficient, void viscosity, micro viscosity.

Electrical properties of polyurethane metal complexes

The static and dynamic electrical conductivity of coordination compounds of 2, 4-tolylene diisocyanate with Cu (II) and Fe (II) halides, and also polyurethanes synthesized from them are studied. According to the proposed model, the electrical conductivity of metal coordination polyurethanes is associated with electron exchange bettween metal ions of different valence, and depends on saturation with electrons of hetero-atoms entering into the composition of the flexible parts of the macro-chain.

Studies of the equilibrium behaviour of crystalline fast-ionically conducting systems

Investigations of several different beta- and beta″-aluminas have found that cationic ordering phenomena play a major role in determining the properties of many of these systems. Low-temperature equilibrium states in the “single-ion” isomorphs of the beta″-aluminas are only attained by careful annealing treatments or by slow cooling the samples from the temperature of ion exchange. Rapidly cooled crystals contain non-equilibrium disordered arrangements that are responsible for the high ionic conductivity. In “mixed-ion” systems ordering between the different cations also inhibits the ionic conductivity. Beta″-aluminas containing two ions of different valence can form cationic arrangements involving substantial long-range correlations.

Spatial distribution of ions around rod-like polyelectrolytes

The nonlinear Poisson–Boltzmann equation for the spatial distribution of counterions and coions around thin cylindrical polyelectrolytes is studied. We give a perturbative treatment of the distribution functions when a small amount of salt is added. Activity coefficients for ions of different valencies are computed explicitly to dominant order in the salt concentration.In excess salt, and with equal valencies, the distribution functions are determined numerically for selected polyion charge densities. For line charge densities beyond a critical value these distributions are universal functions.

Surface studies on aqueous suspensions of tourmaline (dravite)

Tourmaline (dravite) from Western Australia was characterized and its surface properties studied by techniques including potentiometric titrations, microelectrophoresis, X-ray diffraction, microprobe analysis, secondary ion mass spectrometry and ion exchange. Results showed that, when suspended in aqueous solution, dravite released lattice ions into solution. The zeta potential of the dravite surface could be manipulated by exchanging ions from the tourmaline lattice with ions of different valency from solution. The significance of these results to tourmaline flotation are discussed with particular reference to selective cassiterite flotation from tourmaline.

Polyion ion-pair liquid chromatography : I. A new method for the regulation of the retention of ionic compounds in liquid chromatography

A type of chemical interaction, which has received little attention in analytical and separation procedures, is introduced for the use in reversed-phase column liquid chromatography of low-molecular-weight ionic organic compounds. It is the association between a polyion and oppositely charged ions of low valency in aqueous solution. The stationary phase is a microparticulate octylsilica material. It was found that addition of a polyanion, dextran sulphate, of very high molecular weight to the mobile aqueous phase causes a drastic decrease of the chromatographic retention of divalent ammonium compounds. The results follow a retention model which assumes that the polyion associates with the sample ions in the mobile phase. Monovalent sample ions are only ver little affected by the polyion. This opens new possibilities to regulate the separation selectivity between sample ions of different valency and charge type, e.g., in ion-pair chromatography.

Internal friction of alkaline-earth-iron-metaphosphate glasses

The internal frictions of Mg, Ca, Ba iron-metaphosphate glasses were studied from 120 to 700 K using the low-frequency torsion pendulum technique. The internal friction as a function of temperature revealed two distinct peaks. The low-temperature peak was absent in glass without iron oxide. Its activation energy compared favourably with that for dielectric loss and dc conductivity in similar glasses. This suggests the same mechanism for all three processes, probably connected with electron transfer between iron ions of different valence.

Ternary ion exchange. Part 4.—Activity corrections for the solution phase

A previously developed model for the evaluation of activity coefficient ratios in mixed dilute solution is employed with particular respect to ternary cation exchange in zeolites in the presence of up to three different coanions in solution. Potential errors arising from ignoring either completely or partially the non-ideality correction for the solution phase are evaluated and discussed. Exchanges involving counter-ions of the same valency, or involving ions of different valencies, are both considered. It is shown that when all the counter-ions have the same valency, the magnitude of the non-ideality correction is independent of the selectivity of the exchanger. When the valencies of the counter-ions are different it is essential to apply the mixed-salt activity correction for any accurate studies of ternary ion-exchange equilibria.

The primary electroviscous effect in ageing AgI sols: Effect of increasing concentrations of counter ions of different valencies

The electroviscous effect in negatively charged AgI sol has been measured in presence of uni-, bi-, and trivalent cations at different concentrations, for a constant low volume fraction of the suspended solid particles. The I − ion activity of the sol (and also the particle size) gradually increased due to ageing effect during the entire course of study over a period of several months, but remained effectively constant during each course of study (over a few days) with any particular counterion. The potentials were simultaneously measured electrophoretically at identical electrolyte and I − ion concentrations. The electrical (double layer) contribution to the viscosity of the sol was calculated for various values of q o for each electrolyte. A close correspondence has been found in each case with the potential results.

Electrolytic separation of ions of different valency by ion‐exchange membranes

AbstractThe transport properties through a cation‐exchange membrane were investigated for ions of different valency, using an electric field as driving force. In agreement with theoretical considerations a distinct preference of the higher valent ions was found.

Comparison of polyelectrolyte theories of the binding of cations to DNA

Predictions of the binding of counterions to DNA made using the counterion condensation theory developed by Manning are compared with those made using the Poisson-Boltzmann equation, solved numerically by the Runge-Kutta procedure. Ions are defined as territorially or atmospherically bound if they fall within a given distance, defined by counterion condensation theory, from the DNA surface. Two types of experimental situations are considered. The first is the delocalized binding of a single type of counterion to DNA. In this case the Poisson-Boltzmann treatment predicts somewhat lower extents of binding TO DNA, modeled as a 10-A radius cylinder, than does Manning theory. The two theories converge as the radius decreases. The second type of experiment is the competition of ions of different valence for binding to DNA. The theories are compared with literature values of binding constants of divalent ions in the presence of monovalent ions, and of spermidine 3+ in the presence of Na+ or Mg2+. Both predict with fair accuracy the salt dependence of the equilibrium constants.

Electrolytic Separation of Ions by Ion‐Exchange Membranes

AbstractThe ion separation by ion‐exchange membranes appears to be of interest as an energy‐saving, continuous and economical process. The separation of ions of the same valency can only be achieved through membranes which have specific interaction with these ions. Ions of different valencies can, however, be separated thanks to the fixed charges in the membrane. For membranes with low hydrodynamic permeability the separation process can be described by the Nernst‐Planck‐Equations. Exact solutions of these equations exist in parametric form. Their numerical evaluation is easily accomplished with the present‐day programmable calculators. — The analysis shows that at relatively high fields coions are more effectively separated then counter ions, although the separation of the latter is more economical in most cases.