Dilute Aqueous Electrolyte Research Articles

Specific interactions and single-lon activity coefficients in mixed electrolyte solutions

A reexamination of Guggenheim's theory of specific interactions for dilute aqueous electrolyte solutions shows that the parameters of the theory should include terms for interactions between like-charged ions. The equations developed are analogous to those in Pitzer's treatment of concentrated solutions, and the inclusion of ion-solvent interaction parameters allows comparison with the Stokes and Robinson hydration theory treatment. As with hydration theory, specific-interaction theory predicts differences in single-ion activity coefficients.

A simplified form of Stokes–Robinson equation

In non-associated dilute aqueous electrolyte solutions, the deviation from ideality is principally attributed to the interionic interactions and hydration of ions. Stokes and Robinson combined Bjerrum's thermodynamic treatment of ion–solvent interactions with Debye–Hückel treatment of interionic interactions to obtain a two-parameter equation. In very dilute regions, the Stokes and Robinson's equation reduces to a much simpler form, i.e.[Formula: see text]Activity coefficients of an electrolyte at lower concentrations, say up to 0.1 m, can be calculated from the equation provided suitable values of &([a-z]+); and h are available. Solutions of hydrogen chloride and sodium chloride were chosen as examples. The results agree with the existing data very satisfactorily.

Electrical double layer at the interface between mercury and dilute aqueous electrolyte solutions

Differential-capacitance/potential curves were measured at the interface between mercury and dilute aqueous solutions of HClO 4, NaClO 4, NaOH, CH 3COOH and NH 4OH. In the potential region near the zero-charge potential, the double-layer behaviour of these systems is in agreement with Grahame's theory. In the negatively polarized region, the double-layer capacitances of the strong electrolyte systems decrease with decreasing concentration; this result suggests that the complete formation of the compact double-layer becomes difficult in very dilute solutions. The double-layer properties of CH 3COOH and NH 4OH solutions were compared with those of the strong electrolyte solutions. The difference between the weak and strong electrolyte systems in the differential capacitances in the negatively polarized region is explained in terms of the dissociation field effect on weak electrolytes.

Interfacial tension measurements between mercury and dilute aqueous electrolytes

Interfacial tension measurements between mercury and dilute aqueous electrolytes

Interfacial tension measurements between mercury and dilute aqueous electrolytes

Interfacial tension measurements between mercury and dilute aqueous electrolytes

Reversed-phase partition chromatographic separations with 2-ethylhexyl dihydrogen phosphate and di-2-ethylhexyl hydrogen phosphate

Di-2-ethylhexyl hydrogen phosphate (HDEHP) and 2-ethylhexyl dihydrogen phosphate (H 2MEHP) are compared as stationary phases in reversed-phase chromatography of selected lanthanides, strontium, yttrium, barium, manganese(II), iron(III), cobalt(II), nickel, gold(III), platinum(IV), palladium(II) and silver. Chromatograms were mainly developed with hydrochloric acid at various concentrations. In general H 2MEHP was found to be less satisfactory than HDEHP. Development of chromatograms by dilute aqueous electrolytes on paper is slower and separations of chemically similar metals such as lanthanides is not encouraging. However, movement of lanthanides by EDTA at pH 3 in an aqueous sodium perchlorate medium occurs only on H 2MEHP-treated paper. Good separations of iron(III) and cobalt(II) are possible on paper treated with either ester, and gold(III) and platinum(IV) are separated on HDEHP-impregnated paper. Column methods for the separation of carrier-free gold-199 and iron-59 from macro-amounts of neutron-irradiated platinum and cobalt, respectively, have been developed.

Flexibility of native DNA from the sedimentation behavior as a function of molecular weight and temperature

The sedimentation coefficient at infinite dilution of deoxyribonucleic acid has been measured as a function of molecular weight and temperature for several bacteriophage DNA's. Application of statistical thermodynamic and hydrodynamic theories for stiff-chain (“wormlike coil”) polymers in solution to the data from the sedimentation velocity measurements has yielded estimates of the enthalpy and entropy associated with the bending of the Watson-Crick helix in dilute aqueous electrolyte solution. Calculations using the data from this work have shown that the sedimentation coefficient of DNA increases slightly with temperature and the Kuhn statistical length decreases. The enthalpy and entropy of bending for DNA in solution are small, and a crude calculation of the enthalpy required for packing DNA into a bacteriophage head indicates that 10 kcal. per 100 A length of DNA is required for the bending process. Several tentative interpretations of the negative value obtained for the entropy of bending are advanced.

Dielektrisches verhalten von Ta2O5-Schichten im elektrolyten

Deviations from the normal course of the capacitance and of the equivalent series resistance as a function of the frequency in anodized tantalum measured in dilute aqueous electrolyte solutions, and the dependence of these dielectric properties on the composition of the solution, are explained by a conductivity profile in the oxide. It is assumed that a different kind of oxide film is present at the boundary with the solution, which allows electrolyte to enter. The influence of the second-electrode in the solution (normally Pt) used in these measurements is demonstrated or eliminated by using a second identical oxide film instead of platinum. It follows that the unsymmetrical dc current characteristic of the oxide film has no detectable influence on the measured dielectric properties. In addition a treatment of the oxide layers is given, which makes it possible to obtain reproducible results in different kinds of solution over a longer period of time.

Dilatometric measurements of apparent molar volumes of dilute aqueous electrolytes

Dilatometric measurements of apparent molar volumes of dilute aqueous electrolytes

974. Sorption from dilute aqueous electrolyte solutions by zirconia

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The anodic characteristics of mild steel in dilute aqueous soil electrolytes: T. P. Hoar and T. W. Farrer, Corros. Sci.1, 49 (1961)

The anodic characteristics of mild steel in dilute aqueous soil electrolytes: T. P. Hoar and T. W. Farrer, Corros. Sci.1, 49 (1961)

The anodic characteristics of mild steel in dilute aqueous soil electrolytes

The anodic characteristics of mild steel in dilute aqueous soil electrolytes

The anodic characteristics of mild steel in dilute aqueous soil electrolytes

A study has been made of the relationship of anode current density with electrode potential for mild steel, in dilute solutions of soil electrolytes and under conditions simulating the natural corrosion of metal buried in soil. The results allow the estimation of the increase in corrosion rate resulting from the (measurable) change in electrode potential of buried steel structures that may be caused by adjacent cathodic protection or other electrical installations. The logarithm of the anode current density i A/cm 2 in the range 10 −6-10 −4 A/cm 2 is related approximately rectilinearly to the anode potential E; the increase of potential for a tenfold increase of current density, dE/dlog i, is between 40–65 mV in most conditions. Thus a change of potential of +10 mV produces about a 40 per cent increase of anode current density under the most favourable conditions and about an 80 per cent increase under the least; and a change of +20 mV produces about a two-fold increase under the most favourable conditions and a three-fold increase under the least. The presence of active sulphate-reducing bacteria or of small amounts of sulphide tends to give the smallest, least favourable, values of dE/dlog i. Film-forming solutions, including those containing large amounts of sulphide, tend to give the highest, most favourable values (exceptionally, much higher than 65 mV). The theoretical and practical significance of the results is discussed.

Electrokinetic Potentials on Bulk Metals by Streaming Current Measurements: II . Gold, Platinum, and Silver in Dilute Aqueous Electrolytes

The electrokinetic (ζ) potentials of platinum, gold, and silver in contact with distilled water were found to be 60.8, 61.0, and 49.0 mv, respectively. The ζ potentials of these metals were also measured as a function of concentrations of and . Maxima were observed in all cases except that of gold in solutions. These maxima are qualitatively related to the solubilities of the corresponding chlorides and hydroxides.