Solvated Radii Research Articles

Evaluation of the optimum solute concentration for good glass formability in multi-component alloys

The atomic size effect on the glass formability of rapidly solidified metallic materials is explored by using the atomic volume mismatch estimated from the cube of the atomic radius of solvent and solute. The product of the atomic volume mismatch and the minimum solute concentration required to obtain a stable glassy phase is empirically found to be a nearly constant value of 0.10 in various binary alloys and some ternary alloys known as glass forming systems. On the basis of such empirical correlation, the optimum solute concentration for good glass formability is discussed at the phenomenological level, using the results of Fe-Si-B-Cr quarternary alloys as an example.

Photoionization Threshold Energies of Amine Solutions Studied by Photoelectron Emission by Solution

Abstract The threshold energies Et of photoelectron emission by solutions (PEES) were determined for several butylamines in acetonitrile and water. The correlations between Et and gas-phase ionization potential Ip and oxidation potential Eox were found to be linear. The difference between Et and Ip originates from the electronic polarization energy of solvent molecules and the polarization energy was found to be inversely proportional to the solvation radius in accordance with the Born solvation free energy model. The Et values were also compared with Eox to discuss the reorientation relaxation of solvent molecules in the electron transfer process. The selective coverage of aqueous solution surface with amine molecule was indicated by the PEES technique.

Macroscopic model for solvated ion dynamics

A macroscopic treatment of solvated ion dynamics is developed and applied to calculate the limiting (zero concentration) conductance of cations in several aprotic solvents. The theory is based on a coupled set of electrostatic and hydrodynamic equations for the density, flow, and polarization fields induced in the polar solvent by a moving ion. These equations, which are derived by the Mori projection technique, include crucial local solvent structure (ion solvation) effects through solvent compressibility, and local constitutive parameters. If solvent structure is suppressed, the equations reduce to those derived previously by Onsager and Hubbard [J. B. Hubbard and L. Onsager, J. Chem. Phys. 67, 4850 (1977)]. The macroscopic equations are approximately decoupled into electrostatic and hydrodynamic parts. The decoupled equations are solved assuming a step density, viscosity, and dielectric constant model for the local solvent structure and dynamics. This yields analytic expressions for the viscous, ζV, and dielectric ζD, contributions to the ion friction coefficient. These expressions generalize, respectively, the Stokes and Zwanzig results for the (slip) viscous and dielectric friction so as to account for ion solvation effects. The friction coefficients involve a desolvation function Δ which depends on the local structure (density) and dynamics of the solvent. The drag coefficient results reduce in form to those of Zwanzig (within a flow gradient correction factor of 2/3) and Stokes for both weak (Δ→1) and strong (Δ→0) ion–solvent interaction. For Δ→1 the true ionic radius Ri appears in the drag formulas while for Δ→0 a renormalized solvated ion radius σ=Ri+2Rs (where Rs=solvent molecule radius) appears. The theory is fit to experimental cation conductances in pyridine, acetone, and acetonitrile by representing Δ by a two parameter switching function. Agreement between the model and experiment is satisfactory for all three solvents. Moreover dielectric friction is found to have a negligible effect on ion mobility in these solvents.

Calculations on ionic solvation. Part 1.—Free energies of solvation of gaseous univalent ions using a one-layer continuum model

The electrostatic free energy of solvation of an ion has been calculated using a model in which an ion of radius a and dielectric constant εi= 1 is surrounded by a solvent layer of thickness (b–a) and dielectric constant ε1, immersed in the bulk solvent of dielectric constant ε0. The electrostatic energy is combined with the nonelectrostatic free energy of solvation, obtained from experimental data on the free energy of solution of gaseous non-polar solutes, to yield the total free energy of solvation of a gaseous ion in a solvent. It is found that when a is taken as the ionic crystal radius, (b–a) as the solvent radius and ε1= 2 there is excellent agreement with experiment for the solvation of gaseous univalent cations and anions in the solvents, 1,1-dichloroethane, 1,2-dichloroethane, tetrahydrofuran, 1,2-dimethoxyethane, ammonia, acetone, acetonitrile, nitromethane, 1-propanol, ethanol, methanol and water. Limited data suggest that the method can also be applied to solution of ions in benzene, bromobenzene, chlorobenzene, ethyl benzoate, ethyl acetate and nitrobenzene.

Solvation effect of the cation of the supporting electrolyte in hexamethylphosphoramide

Polarographic reductions of sodium and potassium ions in hexamethylphosphoramide (HMPA) have been examined in various supporting electrolytes. The supporting electrolytes, which have much the same solvated radii and much the same electrocapillary curves, sometimes have a significantly different influence on the polarographic reductions of metal ions. The Li+ and Hex4N+ ions provide a typical example. Their effective radii are seen to have much the same characteristics. However, the polarographic reduction of the sodium ion shows a difference in shape between that occurring in Li+ solution and that in Hex4N+ solution. Another example is found in the case of Et4N+, Me4N+ and 5N6+, whose reff and the electrocapillary curves are much the same. However, the polarographic reductions of the sodium and potassium ions are different in these solutions. The solvation number of the solvent molecule of the supporting electrolyte cation seems to exert a great influence on these reductions. The electrocapillary curves were also examined with the tetradodecylammonium ion, tetradecylammonium ion and tetraphenylphosphonium ion used as the supporting electrolytes. The inhibition of the reduction of metal ion for these cations is evidence for their lack of solvation. The effects of the solvated asymmetrical tetraalkylammonium ions on the polarographic behaviour were also examined. When some methyl groups cooperate with the tetraalkylammonium ion, the chemical character is between that of the Et4N+ ion and that of the Me4N+ ion.

Solvation effect of the cation of the supporting electrolyte in hexamethylphosphoramide

Polarographic reductions of sodium and potassium ions in hexamethylphosphoramide (HMPA) have been examined in various supporting electrolytes. The supporting electrolytes, which have much the same solvated radii and much the same electrocapillary curves, sometimes have a significantly different influence on the polarographic reductions of metal ions. The Li + and Hex 4N + ions provide a typical example. Their effective radii are seen to have much the same characteristics. However, the polarographic reduction of the sodium ion shows a difference in shape between that occurring in Li + solution and that in Hex 4N + solution. Another example is found in the case of Et 4N +, Me 4N + and 5N6 +, whose r eff and the electrocapillary curves are much the same. However, the polarographic reductions of the sodium and potassium ions are different in these solutions. The solvation number of the solvent molecule of the supporting electrolyte cation seems to exert a great influence on these reductions. The electrocapillary curves were also examined with the tetradodecylammonium ion, tetradecylammonium ion and tetraphenylphosphonium ion used as the supporting electrolytes. The inhibition of the reduction of metal ion for these cations is evidence for their lack of solvation. The effects of the solvated asymmetrical tetraalkylammonium ions on the polarographic behaviour were also examined. When some methyl groups cooperate with the tetraalkylammonium ion, the chemical character is between that of the Et 4N + ion and that of the Me 4N + ion.

The effect of the double-layer structure on the electrode kinetics of the vanadium perchlorate system

The electrode parameters of the V 3+/V 2+ couple in perchlorate media have been examined by the Faradaic impedance technique. The double-layer structure has been varied by changes in electrolyte concentration and by the adsorption of organic additives both ionic and neutral. Using existing models of the double layer, attempts have been made to correlate changes in the parameters with changes in the reaction plane potential. The results suggest that the reaction plane is somewhat further from the electrode surface than the probable solvated radius of the reacting ions would indicate.

The Solubility of Silver Bromate in Tetrahydrofuran- Water Mixed Solvents

Abstract To investigate the relation between the solubility of inorganic salts and the dielectric constants of solvents, the solubility of silver bromate in tetrahydrofuran-water mixed solvent was determined at 20°, 25° and 30°C, respectively. The logarithm of solubility is almost reciprocally proportional to the dielectric constant of the solvent in the region of the higher dielectric constant. But no linear relation was found in that of the lower dielectric constant of tetrahydrofuran-water mixed solvent. Also, the solvation radius of silver bromate was calculated applying the above-mentioned data. The solvation radius is about 1 Å at each temperature.