Ion-solvent interaction: Viscosity and apparent molar volume of univalent electrolytes in dioxane-water mixtures at different temperatures

The viscosity and apparent molar volume of NaCl, NaBr, NaNO₃, KCl, KBr and KNO₃, at mass fractions of dioxane of 10, 20 and 30%, have been studied at 30, 35, 40 and 45°C. The values of the A and B coefficients of the viscosity equation indicate ion-ion and ion-solvent interactions. The limiting apparent molar volume (φ°) and limiting slope (S_v) is found to be different for different salts at different solvent compositions and has also been interpreted in terms of ion-ion and ion-solvent interaction.     

Ionic association and mobility in propylene carbonate

Molar conductivities were measured at 298.15 K for symmetric quaternary ammonium picrates, R₄NPic, with R equal to C₁ to C₅ as well as for potassium picrate in propylene carbonate. The molar conductivities at infinite dilution, association constants of ion pairs, ionic conductivities at infinite dilution, and Stokes radii were calculated for the ions employed. The salts, Me₄NPic and Et₄NPic, were found to be dissociated, the others are associated. For the associated salts the data conform to the Fuoss model for the association process.     

Conductivities and ion association of 1:1 electrolytes in mixed aprotic solvents

Molar conductivities of the 1:1 electrolytes LiClO₄, LiAsF₆, n-Bu₄NClO₄ and n-Bu₄NBPh₄ were measured in mixtures of propylene carbonate and dimethoxymethane over the concentration range 0.01?1 × 10^?4 mol dm^?3. In all cases a maximum in molar conductivity (and hence in electrolytic conductivity) is observed in a solvent mixture having a composition of around 40 mass % propylene carbonate. Molar conductivities at infinite dilution (Λ^∞) and thermodynamic ion association constants (K^∞_a) were evaluated from these data. Single ion molar conductivities (λ^∞_i) were evaluated using the assumption that λ^∞(n-BuN⁺₄) = λ^∞(BPh^?₄). In order to account for the observed conductivity behavior it is necessary to assume that lithium salts from solvent separated ion pairs in ethereal solvents. All other salts from contact ion pairs.     

Physico-chemical properties of NH4I-formamide concentrated solutions

Density, viscosity and electrical conductivity of NH₄I-formamide solutions up to the saturated concentration, in the temperature range 25–55°C, are reported in this work. From the density data which linearly depend on the salt concentration, apparent and partial molar volumes constant and close to the molecular volume of pure salt can be deduced. Viscosity data, treated following the V and model, show a weak interaction of NH⁺₄ ion with the solvent in all the range of concentrations used. Viscosity and conductivity have also been analysed, following a proposal of Angell, with an extended Arrhenius equation used in the treatment of transport in glass-forming liquid.     

CORRELATION OF PARTIAL MOLAR VOLUMES AT INFINITE DILUTION OF SALTS IN WATER

Salt partial molar volumes at infinite dilution show the unusual behavior of increasing with pressure while at higher temperatures becoming large and negative, reaching negative infinity at the critical point of water. A simplified method for estimating the infinite dilution partial molar volumes for fully ionized aqueous salts up to 350°C and all pressures has been developed using generalized expressions based on fluctuation solution theory. Tabulations of parameters are given for several salts made from 10 different cations and 9 different anions that can be used to predict V^∞ _s for many solutions of practical interest.     

Electrical conductance and apparent molar volumes of Al(ClO4)3, Be(ClO4)2, and Cu(ClO4)2 in N,N-dimethylacetamide solutions at 25°C

Equivalent conductances and apparent molar volumes of Al(ClO₄)₃, Be(ClO₄)₂, and Cu(ClO₄)₂ in N,N-dimethylacetamide at 25°C are reported. The limiting equivalent conductances, the first step association constants, and the apparent molar volumes at infinite dilution are derived and discussed in terms of influence of nature of cation on the properties of DMA-solvated cations.     

Molar volumes of aqueous acetic acid-ammonium salt solutions

The mean apparent molar volumes φ_v of the CH₃COOHNH₄X(X  Cl, Br, NO₃) solutions have been determined at 40° from precise density measurements. The modified Young's rule for electrolyte-nonelectrolyte mixtures has been used to predict mean apparent molar volume, φ_v, from the pure water data. The modified Young's rule was found to be applicable for the CH₃COOHNH₄X systems to some extent. The deviations from the Young's rule approximation are studied as excess volumes of mixing of CH₃COOH and NH₄X solutions.     

The development of a response surface model for the determination of infinite dilution partial molar volumes and excess volumes from dilute multi-component data alone. Implications for the characterization of non-isolatable solutes in complex homogeneous reactive systems

A non-ideal system containing several solutes, e.g. methanol, acetone, and 2-butanol in n-hexane was studied. Traditionally defined excess molar volumes (based on pure component molar volumes) of the multi-component solutions were measured in the limit of infinite dilution in n-hexane using a vibrating-tube densitometer at and . An experimental design in the concentration range 0.0015<x_solute-i<0.023 was explored, optimizing the metric distance among the solutes to avoid clustering. The partial molar volumes of methanol, acetone, and 2-butanol at infinite dilution determined from the multi-component data were very consistent with the values obtained from separate binary experiments. Next a total molar volume response surface model was developed. Only experimental total volume and component moles are needed for analysis. The partial molar volumes of all the solutes were accurately predicted from the multi-component data alone. A new expression for excess molar volume is proposed to express component interactions. This approach is undoubtedly of considerable usefulness for determination of the partial molar properties of non-isolated but observable species in multi-component reactive solutions.     

Thermal diffusion of alkali chlorides in H2O and D2O

Entropies of transport for very dilute aqueous alkaline chlorides solution at 25° have been determined by the potentiometric method. The limiting slopes were calculated and the molar entropies of transport at infinite dilution obtained by extrapolation.The standard transported entropy of Cl^? ion was also derived by extrapolating the steady state thermoelectric powers to infinite dilution. The ‘absolute’ ionic entropies of transport have been estimated from the standard transported entropy following Gurney's choice of the absolute standard partial molar entropy of H⁺ ion as ?5.5eu.Soret data obtained in H₂O are compared with that obtained in D₂O. Results are discussed in terms of the structure of the solvent and ionic hydration phenomena.     

Molar volumes of multicharged electrolytes in water and aqueous sulphuric acid

The apparent molar volumes, φ_v, of aluminium ammonium sulphate and potassium aluminium sulphate in water and aqueous sulphuric acid (0.01, 0.05, 0.10 and 0.15 N) at different concentrations and temperatures have been estimated from the densities of the solutions measured by hydrostatic balance. The φ_v values vary linearly with square root of concentrations. The limiting apparent molar volume, φ⁰_v, and the experimental slope S_v, have been interpreted in terms of solute-solvent and solute-solute interactions, respectively. The φ⁰_v values vary with temperature and can be represented in the power series of temperature. Structure making/breaking capacity of the electrolyte is inferred from the sign of [?φ⁰_v/?T²] values. Both the electrolytes behave as structure breakers in water but structure makers in aqueous sulphuric acid. The molar expansibility, at infinite dilution have been found to be the same for both electrolytes at 290.5 K.     

emf Studies of zinc halides ln concentrated aqueous NH4NO3CA(NO3)2 solutions

The formation constants of the species ZnC⁺, ZnCl₂, ZnBr⁺ and ZnBr₂ were determined from emf measurements in suitable concentration cells. Mixtures of NH₄NO₃Ca(NO₃)₂ with a molar ratio 0.844/0.156 containing variable amounts of water (from 0 to 1.2 moles per mol of salt) were used as a solvent. The bromide complexes were found to be more stable than the chloride complexes in the anhydrous melt, while the opposite was found in the concentrated aqueous solutions. The results are discussed on the basis of models for chemical equilibria in molten salts and aqueous melts.     

Conductometric study of ion—ion and ion-solvent interaction—1. Conductances of lithium acetate in water,methanol and 50, 60 and 70% (W/W) dioxane—water mixtures at 25°C

Conductances of lithium acetate in water, methanol and 50, 60 and 70% (w/w) dioxane—water mixtures were measured. The data was analysed using the Fuoss-Hsia equation in the form of Fernandez—Prini coefficients to find the ion-pair formation constants (K_A) and molar conductances at infinite dilution. The log K_Avs 1/D plot is a straight line passing through the origin in agreement with the Dension—Ramsey theory. The Walden products, solvation numbers and solvodynamic radii were also calculated. The results indicate the formation of solvent separated ion-pairs (SSIP).     

The conductance of 1:1 electrolytes in sulfolane in the presence of proton donors at 30°C

The molar conductances of LiCl, LiNO₃, KCHCl₂COO and Na p-(NO₂)C₆H₄O in sulfolane, in the presence of HCl, CH₃COOH, CHCl₂COOH and p-(NO)₂C₆H₄OH have been determined. The data were analysed by the full Pitts equation and interpreted in terms of the ionic association constant (K_A) of the salts K⁺A^? and K⁺RHA^?, and the heteroconjugation constant (K_f) of RHA^?. Values of K_f have been calculated from the ratio of association constant K_A(K⁺A^?)/K_A(K⁺RHA^?).     

Temperature-dependent aggregation of bio-surfactants in aqueous solutions of galactose and lactose: Volumetric and viscometric approach

Modulation in the aggregation behavior of bio-surfactants(bile salts), sodium cholate(NaC) and sodium deoxycholate(NaDC) in aqueous solutions of carbohydrates(galactose and lactose) have been investigated by measuring the density(ρ), speed of sound(u) and viscosity(η) of the mixtures at different temperatures293.15, 298.15, 303.15, 308.15 and 313.15 K. The density and speed of sound data have been used to calculate various volumetric and compressibility parameters such as apparent molar volume(V_φ), isentropic compressibility(κ_s), apparent molar adiabatic compression(κ_(s, φ)) to get a better insight into the micellization mechanism of bile salts. Further, the viscosity data have been studied in the light of relative viscosity(η_r) and viscous relaxation time(τ). Some derived parameters such as free volume(V_f), internal pressure(πi) and molar cohesive energy(MCE) of Na C and Na DC in aqueous solution of saccharides have also been calculated from viscosity data in conjunction with density and speed of sound values. All the calculated and derived parameters provide qualitative information regarding the nature of interactions i.e. solute–solute, solute–solvent and solvent–solvent in the solution.     

Density,viscosity and electrical conductivity of LiCl and some uni-bivalent electrolytes in formamide solutions at 25°C

Density, viscosity and equivalent conductivity in formamide at 25°C are reported for LiCl, Mg(ClO₄)₂, CaCl₂, CaBr₂, Ca(NO₃)₂, ZnCl₂, ZnBr₂ and ZnI₂ salts. The linear dependence of the density of the investigated salts on the concentration is interpreted assuming that the structural configuration of the solvent formamide remains unchanged in the concentration range experienced. Viscosity and conductivity data have been treated following a proposal of Angell. A least-squares program used to linearise the lg Λ and the lg η functions against 1/(N₀ ? N) gives N₀ values, the glass-transition concentration at 25°C, acceptably low and sufficiently close in most cases.     

Apparent molar volumes of tetraalkylammonium iodides in sulfolane at 30, 40 and 50° C

The apparent molar volumes φ_ν of some tetraalkylammonium iodides R₄NI (R = Et, Pr, Bu, Am, Hex) have been determined in sulfolane at 30, 40 and 50°C. From the limiting apparent molar volumes, we have calculated φ°_ν values using Masson's equation and we have obtained the individual ionic φ°_ν (ion) contributions according to the method suggested by Conway, Verral and Desnoyers. From the ionic limiting apparent molar volumes and their dependence on temperature it is possible to obtain information about the kind of interactions between R₄ N⁺ ions and sulfolane.     

Polyelectrolyte behaviour of acrylonitrile methallylsulphonate copolymers in dimethylformamide

The properties in organic solvent (DMF) of two ionic copolymers are investigated and compared to those of polyelectrolytes in aqueous solutions. First, the viscometric behaviour is disccussed: it is demonstrated that [η] varies linearly with $\text{C}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}{}_{\mathrm{T}}$, where C_T is the ionic concentration of the solution. At infinite salt concentration we obtain data in agreement with unperturbed dimensions. Using isoionic dilution, we deduce ø_p, the osmotic coefficient. From osmometry, the dependence of ø_p on the concentration is obtained and compared to the theoretical value. In the presence of neutral salt, the osmotic pressure is determined as a function of salt and polymer concentrations. The results are interpreted in terms of a Donnan equilibrium.     

CORRELATION OF PARTIAL MOLAR VOLUMES AT INFINITE DILUTION OF SALTS IN WATER

Salt partial molar volumes at infinite dilution show the unusual behavior of increasing with pressure while at higher temperatures becoming large and negative, reaching negative infinity at the critical point of water. A simplified method for estimating the infinite dilution partial molar volumes for fully ionized aqueous salts up to 350°C and all pressures has been developed using generalized expressions based on fluctuation solution theory. Tabulations of parameters are given for several salts made from 10 different cations and 9 different anions that can be used to predict V^∞ _s for many solutions of practical interest.     

Thermodynamic interactions of solvents with styrene–butadiene–styrene triblock copolymers

Fundamental thermodynamic interaction data for various solvents with two styrene–butadiene–styrene triblock copolymers (Kraton D-1101 and Kraton D-1300X) have been collected by the use of inverse gas chromatography at infinite dilution. Experimental results are presented for nine D-1101/solvent systems and nine D-1300X/solvent systems at 308, 328. and 348 K. Weight-fraction activity coefficients and Flory–Huggins χ interaction parameters have been calculated from the retention volumes. The χ parameter is used as a measure of the strength of interaction and therefore as a guide in the prediction of polymer–solvent compatibility. In addition, partial molar heats of mixing, ΔH_m^∞, and heats of solution, ΔH_s, were determined. The Hildebrand–Scatchard solubility theory was combined with the Flory theory in order to estimate the solubility parameter of the thermoplastic rubbers at the three different temperatures.