Basic Electrolyte Solution Research Articles

Electrosorption of 2-butanol at constant chemical potential of base electrolyte and in the moderate bulk concentration region

The adsorption of 2-butanol on a polarized mercury electrode was investigated at constant activity of the base electrolyte using low and moderate bulk concentrations of the adsorbate. Capillary electrometer and impedance bridge measurements were used as experimental techniques. Both interfacial tension and capacity data were employed for fitting to the Frumkin equations. Results paralleled closely those obtained in earlier adsorption studies of aliphatic compounds employing a base electrolyte solution of fixed concentration.

Formation of Hydrogen Gas with an Electrochemical Photo-cell

Abstract In an electrochemical photo-cell the use of a basic electrolyte solution in the TiO2 electrode compartment and an acidic one in the Pt cathode compartment can produce a high yield of hydrogen gas.

Electrode kinetics and double-layer structure III. The Eu(II)/Eu(III) electrode reaction at the DME in 1 M KCl and 1 M KI base electrolyte solutions

A detailed study has been made of the kinetics of the Eu(III)/Eu(II) electrode reaction in 1 M KCl and in 1 M KI at the dropping mercury electrode, by means of impedance measurements, both at equilibrium potentials (varying cox*/cred/* ratio, cox*+cred*=10 mM) and at externally controlled electrode potentials (cox*=10 mM). The data were analyzed according to the complex plane method, i.e. by considering the electrode admittance as a function of frequency. For the correct interpretation of the results it has been necessary to apply a modified version of the Frumkin correction, taking into account the considerable influence of the highly charged electroactive ions on the potential 2 in the outer Helmholtz plane. Careful comparisons between the results at different potential regions revealed that the data are consistent with a potential-independent, “true” transfer coefficient α (0.59 in 1 M KCl and 0.52 in 1 M KI). On the basis of these values the apparent rate constant ksha was determined in various ways, which gave consistent results. It is shown that the potential dependence of ksha is almost entirely due to the Frumkin effect, since values of the “true” rate constant kshf were substantially potential independent. The mean values are: kshf=(1.4±0.2)×10−5 (in 1 M KCl) and kshf=(0.6±0.1)×10−5 cm s−1 (in 1 M KI). Since in the studied potential region the amounts of specifically adsorbed CI− and I− ions are very different and are moreover strongly potential dependent, it can be concluded that, oppositely to some amalgam-forming redox couples studied previously, specific adsorption has no influence on the charge transfer rate of the Eu(III)/Eu(II) couple. From this it can be inferred that the charge transfer takes place outside the inner part of the double layer (probably even at some distance from the outer Helmholtz plane), the reactants remaining hydrated before or during the reaction. This finding might be a general feature of electrode reactions where both the Ox and the Red components are present in the electrolyte solution.

Electrode kinetics and double-layer structure: III. The Eu(II)/Eu(III) electrode reaction at the DME in 1 M KCl and 1 M KI base electrolyte solutions

Summary A detailed study has been made of the kinetics of the Eu(III)/Eu(II) electrode reaction in 1 M KCl and in 1 M KI at the dropping mercury electrode, by means of impedance measurements, both at equilibrium potentials (varying c ox * / c red / * ratio, c ox * + c red * =10 m M ) and at externally controlled electrode potentials ( c ox * =10 m M ). The data were analyzed according to the complex plane method, i.e. by considering the electrode admittance as a function of frequency. For the correct interpretation of the results it has been necessary to apply a modified version of the Frumkin correction, taking into account the considerable influence of the highly charged electroactive ions on the potential 2 in the outer Helmholtz plane. Careful comparisons between the results at different potential regions revealed that the data are consistent with a potential-independent, “true” transfer coefficient α (0.59 in 1 M KCl and 0.52 in 1 M KI). On the basis of these values the apparent rate constant k sh a was determined in various ways, which gave consistent results. It is shown that the potential dependence of k sh a is almost entirely due to the Frumkin effect, since values of the “true” rate constant k sh f were substantially potential independent. The mean values are: k sh f =(1.4±0.2)×10 −5 (in 1 M KCl) and k sh f =(0.6±0.1)×10 −5 cm s −1 (in 1 M KI). Since in the studied potential region the amounts of specifically adsorbed CI − and I − ions are very different and are moreover strongly potential dependent, it can be concluded that, oppositely to some amalgam-forming redox couples studied previously, specific adsorption has no influence on the charge transfer rate of the Eu(III)/Eu(II) couple. From this it can be inferred that the charge transfer takes place outside the inner part of the double layer (probably even at some distance from the outer Helmholtz plane), the reactants remaining hydrated before or during the reaction. This finding might be a general feature of electrode reactions where both the Ox and the Red components are present in the electrolyte solution.

Mechanism of the Zn II/Zn(Hg) exchange : Part 2: catalysis by halide and thiocyanatk ions

The faradaic admittance at dilute Zn amalgam electrodes in aqueous solutions containing: Zn II has been measured using as base electrolytes solutions containing halide and thiocyanate ions. It is known from previous work by randles and somerton that the rate of the Zn II/Zn(Hg) exchange is accelerated in. the presence of these anions. Measurements have been made using (i) 1 M halide and thiocyanate solutions and (ii) 2 M NaClO 4 solutions containing small varying amounts of added halide or thiocyanate, as base electrolyte solutions. The reaction orders with. respect to Zn II, Zn and X − have been established. In 2 M NaClO 4, the reaction proceeds through the parallel paths Zn 2+ + 2e ⇌ Zn(Hg) Zn 2+ + X − + 2e ⇌ Zn(Hg) + X − (where X − is Cl −, Br −, I − or CNS −) at low X − concentration. At high iodide concentration there is evidence that the predominant reaction is Zn 2+ + 2I − + 2e ⇌ Zn(Hg) + 2I −. (All reactions listed might be composite, and proceed through two consecutive one-electron steps). The rate constants, transfer coefficients, activation energies and frequency factors for the anion-catalysed processes have been obtained by an analysis of the observed exchange currents. The variations of activation energy ΔH ≠ and frequency factor A observed in these reactions are related to an approximate correlation of the type δΔH ≠ ≈ δ log A that appears to hold very generally for the rate constants of electrode processes, measured under similar experimental conditions.

Determination of small amounts of calcium in the presence of large amounts of alkali metal salts by amperometric chelatometry

A rapid polarographic procedure for the determination of 0–50 ppm of calcium in alkali metal salts is described. It is selective and highly sensitive, with only strontium and barium causing interference to any marked degree. A cathode ray polarograph is used to measure the zinc peak current in a potassium chloride/hydroxide/zincate base electrolyte solution; a standard EDTA solution is added to the test solution; and the peak current of the zinc remains sensibly constant until all of the calcium has reacted, after which the peak current decreases as the zinc reacts with the EDTA. The end-point is found by extrapolation of the current-titration curves.