Solutions Of Strong Electrolytes Research Articles

Local order and vibrational dynamics in strong II-I mixed electrolytic aqueous solutions

EXAFS and Raman spectra, obtained from mixed MBr2+NBr2 (M, N=Zn2+, Cu2+, Sr2+) in H2O are discussed. The measurements, carried out at Adone (PULS facility), for EXAFS and in our light scattering laboratory, for Raman, allow us to study both the static and the dynamic properties of these systems. In particular, strong evidence of metal-halogen ionic pairs and hydration shell formation is reported. Our results, in terms of existing structural models, are also discussed.

Calculation of the density of aqueous solutions of strong electrolytes from individual ionic parameters

Based on a hypothesis verified earlier, according to which the concentration dependence of apparent molar volumes of ions in aqueous solutions is caused by their dehydration due to the decrease of the volume concentration of water, a method for the calculation of the density of concentrated aqueous electrolytes from individual ionic constants is proposed. The theory is verified by comparing with experimental data from the literature (420 solutions of 57 electrolytes).

Structure related fluctuation of refractive indices of aqueous strong electrolyte solutions.

Structure related fluctuation of refractive indices of aqueous strong electrolyte solutions.

Quantitative Treatment of The Variation of The Mean Activity Coefficient of The Ions in Solutions of Strong Electrolytes with Dilution

Quantitative Treatment of The Variation of The Mean Activity Coefficient of The Ions in Solutions of Strong Electrolytes with Dilution

Quantitative Treatment of the Variation of Ionic Activity and Equivalent Conductivity of Solutions of Strong Electrolytes with Dilution

Quantitative Treatment of the Variation of Ionic Activity and Equivalent Conductivity of Solutions of Strong Electrolytes with Dilution

Estimation of activity coefficients in concentrated sulfite‐sulfate solutions

AbstractThe electrolyte theory of Pitzer and coworkers is used to estimate geometric mean‐ion activity coefficients in strong electrolyte solutions at 25–55°C. By using Pitzer's equations with ion‐pair parameters estimated in this paper, one can calculate activity coefficients to moderately high ionic strengths in aqueous mixtures containing the following ions: Na+, K+, Mg2+, Ca2+, Cl−, ClO, ClO, HCO, HSO, CO, SO, SO, and S2O. Mixtures containing these ions are present in CaO/CaSO4 flue gas desulfurization units and in laboratory experiments aimed at understanding the chemistry occurring in such units. The computed activity coefficients are relatively insensitive to the values of the estimated quantities. The basis of the estimates, as well as their effect on calculated activity coefficients, is discussed. It is concluded that activity coefficients are estimated with an accuracy of ±25% or better.

Quasihydrodynamic theory of ionic conductance in spatially homogeneous solutions of strong electrolytes

Correlation function expressions are derived for the contributions of the frequency-dependent relaxation effect to the conductivity and dielectric permittivity of the electrolyte solution. The evolution equation for the time-dependent irreducible ionic pair correlation function is derived in the mean field approximation by the application of the generating functional method.

An analytic solution of the non‐linear equation ∇2λ(r) = f(λ) and its application to the ion‐atmosphere theory of strong electrolytes

For a long time the formulation of a mathematically consistent statistical mechanical theory for a system of charged particles had remained a formidable unsolved problem. Recently, the problem had been satisfactorily solved, (see Bagchi [1] [2]) ,by utilizing the concept of ion‐atmosphere and generalized Poisson‐Boltzmann (PB) equation. Although the original Debye‐Hueckel (DH) theory of strong electrolytes [3] cannot be accepted as a consistent theory, neither mathematically nor physically, modified DH theory, in which the exclusion volumes of the ions enter directly into the distribution functions, had been proved to be mathematically consistent. It also yielded reliable physical results for both thermodynamic and transport properties of electrolytic solutions. Further, it has already been proved by the author from theoretical considerations (cf. Bagchi [4])as well as from a posteriori verification (see refs. [1] [2]) that the concept of ion‐atmosphere and the use of PB equation retain their validities generally. Now during the past 30 years, for convenice of calculations, various simplified versions of the original Dutta‐Bagchi distribution function (Dutta & Bagchi [5])had been used successfully in modified DH theory of solutions of strong electrolytes. The primary object of this extensive study, (carried out by the author during 1968‐73), was to decide a posteriori by using the exact analytic solution of the relevant PB equation about the most suitable, yet theoretically consistent, form of the distribution function. A critical analysis of these results eventually led to the formulation of a new approach to the statistical mechanics of classical systems, (see Bagchi [2]), In view of the uncertainties inherent in the nature of the system to be discussed below, it is believed that this voluminous work, (containing 35 tables and 120 graphs), in spite of its legitimate simplifying assumptions, would be of great assistance to those who are interested in studying the properties of ionic solutions from the standpoint of a physically and mathematically consistent theory.

Effects of strong electrolytes on the iron alum--Alcian Blue--Safranin staining of mast cell granules of the rat.

Rat mast cells fixed in Carnoy's fluid were stained with iron alum-Alcian Blue--Safranin solution after pre-treatment with strong electrolyte solutions including acids, neutral salts and alkalis. Although both red and blue mast cells were observed without pre-treatment, most mast cells were stained blue and a few red when they were stained after the pre-treatment. Mast cell granules contain salt complexes formed between basic proteins and acidic polysaccharides through ionic linkages between protein basic groups and polysaccharide sulphate and carboxylic acid groups. It is suggested that when sections are treated with strong electrolyte solutions, complexes are broken by disruption of ionic linkages and sulphate and carboxylic acid groups of polysaccharides masked by basic proteins become available for binding Alcian Blue. This was confirmed by model experiments performed with smears of a heparin-lysozyme complex. When mast cells were fixed in aldehyde-containing fixatives, no effects of strong electrolyte solutions on the staining properties of mast cell granules were revealed.

PREDICTION OF WATER ACTIVITY OF AQUEOUS SOLUTIONS IN CONNECTION WITH INTERMEDIATE MOISTURE FOODS: EXPERIMENTAL INVESTIGATION OF THE awLOWERING BEHAVIOR OF SODIUM LACTATE AND SOME RELATED COMPOUNDS

ABSTRACTThe water activity lowering behavior of sodium lactate, lactic acid, and other related hydroxy acids as well as its sodium salts, has been experimentally determined. The results for the sodium salts were very well fitted to Bromley's (1973) model for awin aqueous solutions of strong electrolytes, while the aw, data for the acids were very well described by Norrish's (1966) equation. It was found that sodium lactate does not present any exceptional negative deviation from Raoult's law as it has been reported in the literature. The B number for sodium lactate (0.050 kg/mol−1) was found to be somewhat lower than that corresponding to sodium chloride. Moreover, lactic acid was found to have a small positive deviation from Raoult's law.

Structural properties of ionic liquids

Abstract Two types of ionic liquids are considered: molten salts and aqueous solutions of strong electrolytes. It is shown that in both cases, modern theoretical methods are capable of making definite predictions about the spatial correlations between the ions themselves and between the ions and water molecules. It is further shown that the technique of neutron diffraction as applied to isotopically enriched samples allows, for the first time, detailed comparisons to be made between theory and experiment. The results of these comparisons are discussed and areas in which the theory is in urgent need of revision are identified.

EXAFS studies of strong electrolytic solutions

Extended x-ray absorption fine structure measurements are reported for aqueous solutions of CuBr2, ZnBr2, CuCl2, NiCl2, and NiBr2 at various concentrations. It is shown that, for highly concentrated solutions of CuBr2, ZnBr2, and CuCl2, some local order, resembling that of the corresponding crystals, exists. When the concentration decreases, this order partly remains, while the hydration increases. In contrast to this behavior, SrBr2 does not show the existence of any bonding, and it is difficult to make conclusions in the case of NiCl2 and NiBr2 solutions. The temperature dependence of the EXAFS spectra of CuBr2 and ZnBr2 is presented also; some change in the low energy region occurs between 45 and 60°C for CuBr2 solutions.

The prediction of water activity of aqueous solutions in connection with intermediate moisture foods III. aW Prediction in multicomponent strong electrolyte aqueous solutions

SummaryA study was made on the theoretical prediction of water activity (aW) in multicomponent aqueous solutions of strong electrolytes, in the range of aW of most interest for intermediate moisture foods (IMF). A simplified model proposed by Ross (1975) is tested against a rigorous model equation developed on the basis of recent statistical theories of electrolytes. As a result of this study a new simple and very accurate model equation is proposed for predicting aW in aqueous solutions of mixed strong electrolytes in the aW range of most interest to IMF.

Ion-pairing in aqueous media. An exact solution for the interaction energy associated with two dielectric spheres

The phenomenon of ion-pairing in strong aqueous electrolyte solutions is examined by looking at the Coulomb interactions between two typical ions. These are modelled as hard-spheres in order to take account of the short-range forces between them and the surroundings are treated as a continuum having a macroscopic value for the dielectric constant of pure water.The present work leads to exact analytical formulae for the field strength and effective dielectric constant of the system. Only approximate and purely numerical solutions have been previously available and these are compared with the full solutions.

An estimation of the volume of restructured water shells around hydrophobic solutes

Water is known to be a largely associated liquid. The presence of non-electrolytes or large organic ions, tends to strengthen the hydrogen bonds between the water molecules near the large hydrophobic solute, and a cage or ‘iceberg’ is effectively formed around them. This model of the hydrophobic hydration of alkyl groups is widely accepted but the thickness of restructured water shells around hydrophobic solutes has not been determined. In order to estimate the volume of restructured water per mole hydrophobic solute we used the differential conductometry of carefully thermostatted (0.001 °C) solutions [1,2]. The experimental procedure consists of measuring the specific electrical conductance ( χ) of a strong electrolyte solution before and after adding a small amount of hydrophobic solute. Provided the equivalent conductance of the strong electrolyte ions in the restructured water shell is zero [3] the volume of the restructured water shell is given by [2,3] ▪ where Δ χ is the change in χ, corrected for the increase in volume and c is the molar concentration of the strong electrolyte. We have attempted to measure the V s,o-values in aqueous solutions of perchloric acid for 16 alkylammonium ions. The results obtained can be summarized as follows. ▪ where n(i) is the number of groups i in the ion studied and V(i) is the specific volume of hydration shell of i-group. In 10–20% HClO 4(w/w), V(CH 3) ≈ V(CH 2 ≈ 40 ± 10 [cm 3/n(i)] mol] and V(NH + 3) ≈ −48 ± 10 [cm 3/n(i)]. The negative value for V(NH + 3) reflects the negative hydration of −NH + 3-group.

Estimation of phase diagrams and solubilities for aqueous multi‐ion systems

AbstractCalculation of the phase diagram for saturated aqueous multi‐ion solutions of strong electrolytes, based upon use of the thermodynamic solubility products, is illustrated for the four‐ion system: Na+, K+, Mg++, SO4=. Solid phases are identified along with the ion concentrations of the associated saturated solutions.

Light-induced conductivity changes in purple membrane suspensions.

Small light-induced changes in the conductivity of light-adapted purple membrane suspended in strong electrolyte solutions were detected. The method used involved modulated light and a phase sensitive detector and it allowed us to detect accurately changes as small as 0.0001% in the conductivity of the suspension. The light-induced conductivity changes turned out to be composed of at least two different event: a small fast increase in conductivity (tau approximately 2 ms) followed by a slower and larger decrease in this parameter (tau = 70 ms-80 ms). The effects of pH and temperature on these changes were studied. Both events reached maximal values around neutral pH and approached zero at both high and low pH's. Heating the suspension decreased the photoconductivity change and Arrhenius plots of the data showed breaks around 31 degrees C. It is suggested that the conductivity changes reflect changes in the surface charge of the membrane and can be used to follow the kinetics of the conformational changes occurring in the system.

Conductance equation of dilute mixed strong electrolytes. II. Hydrodynamic and osmotic terms in relaxation field

The hydrodynamic and osmotic terms in the relaxation field are computed up to order linear in concentration for a dilute solution of mixed strong electrolytes using the primitive model. The computation is based on the relative function μji computed in part earlier for the purely electrostatic interaction and in part in this work for the hydrodynamic interaction assuming the adequacy of the Fuoss velocity field. The results are compared with the earlier computations of Fuoss and Onsager, Murphy and Cohen, and Falkenhagen, Ebeling, and Kraeft. It is found that some terms of the new results are in agreement with the earlier computations and the other terms represent an improved computation.

Theory of concentrated solutions of strong electrolytes. Part 2.—Thermodynamic properties of mixed electrolytes. Theoretical basis of the Harned rule

The lattice-like model of electrolyte solutions has been used to interpret the thermodynamic properties of mixtures of strong electrolytes. Activity coefficients and the partial molar enthalpy content of several pairs of electrolytes have been calculated by assuming a cubic lattice of the common ion in which the two sorts of counter ions occupy body-centred positions. Comparison with experiment shows fairly good agreement. The theoretical treatment yields a correlation between Harned rule coefficients and the activity coefficients of the pure components at the total concentration of the mixture. According to this correlation the absolute value of the Harned rule coefficients, α1,2 and α2,1, must be the same, which is in agreement with measured values in case of acid mixtures, while the difference in their absolute value points to local hydrolysis in salt solutions.

A new thermodynamic representation of binary electrolyte solutions nonideality in the whole range of concentrations

AbstractA system of equations based on the ionic atmosphere theory of Debye and Huckel, Born model contribution, and local compositions of the nonrandom two‐liquid (NRTL) model is developed to represent isothermal activity coefficients, in the whole range of concentrations, for solutions in an undissociated solvent of a partially or completely dissociated electrolyte.The physical constants and the four adjustable parameters necessary to represent the osmotic coefficient, for fifteen strong aqueous electrolytic solutions, are given at 298.15°K and atmospheric pressure. Vapor‐liquid equilibrium, for the hydrochloric acid‐water system at 298.15°K, is represented for acid compositions ranging from infinite dilution to 18 M using a known dissociation constant and six parameters.