Zbigniew Koczorowski

Electrochemical studies of the tetrabutyl- and tetramethyl-ammonium ion transfer across the water-1,2-dichloroethane interface: A comparison with the water—nitrobenzene interface

Abstract The results of electrochemical studies on the reaction of tetrabutyl- and tetramethylammonium (TBA + and TMA + ) ion transfer from water to 1,2-dichloroethane are presented in this paper and are compared with se of the water—nitrobenzene interface. The TMA + ion transfer has been studied by the chronopotentiometric cyclic voltammetry methods and that of the TBA + ion by the chronopotentiometric method only. It has been found that the reactions are diffusion controlled over the current density range up to about 1O μA cm −2 and at polarization rates up to 0.15V s −1 . Diffusion coefficients of the studied ions have been detemined, as well as their formal potentials with respect to an ion-selective tetrabutylammonium electrode to a partition electrode containing tetraethylammonium picrate whose potential is close to zero. In additon, kinetic parameters of the transfer reaction have been determined for the tetrabutylammonium ion from data obtained at current densities over 10 μA cm −2 (irreversible range).

Adsorption of aliphatic nitriles at the air/solution and the mercury/solution interface

Abstract The adsorption of aliphatic nitriles (acetonitrile, propionitrile and butyronitrile) at the air/solution and the mercury/solution interface is compared by means of surface and interfacial tension, and of surface potential measurements. Results show that the interfacial behaviour is very similar in terms of surface pressure, but is dramatically different in terms of surface potential. The difference is rationalized on the basis of existing models for the adsorption layer, emphasizing the role played by the different orientation of solvent molecules at the two interfaces.

System for electrochemical studies with a four-electrode potentiostat

Abstract A four-electrode potentiostat and a system for electrochemical studies are described. The system is suitale for studies of an interface separating immiscible elecrolyte solutions by voltammetric, chronoamperometric and polarographric methods. The described systems are based on integrated operational amplifiers.

Remarks on the galvani potential of the interface separating immiscible electrolyte solutions

Abstract The Galvani potential ws and its components are discussed for the case of an interface separating two immiscible electrolyte solutions, as well as the relationships and the difference between the Nernst and Donnan equilibria. A method is proposed for measuring the Δws potential by means of a cell with transfer, and preliminary results of such studies are presented for the water-nitrobenzene interface.

Studies of Galvani potentials of the water-nitrobenzene and water-1,2-dichloroethane interfaces

Abstract Possibilities of studying distribution potentials (Galvani potentials) of salts and their ionic components for the water-nitrobenzene and water-1,2-dichloroethane interfaces are presented. The proposed method takes advantage of cells with transport in which a distribution system containing tetraethylammonium picrate serves as the reference interface, the Galvani potential of such a system being close to zero. The measurements carried out for several electrolytes containing one hydrophobic and one hydrophilic ion have shown a satisfactory agreement with the potential values calculated from the literature data on extraction for the water-nitrobenzene system, assuming that the energies of transfer of the tetraphenylarsonium and tetraphenylborate ions are equal.

Study of the impedance of the water-1,2-dichloroethane interface: influence of the picrate ion transfer

Abstract Impedance measurements of the water—1,2-dichloroethane (1,2-DCE) interface in the presence of supporting electrolytes in both phases and picrate ions in the organic phase have been carried out using ac voltammetric and ac bridge methods. The analysis of the impedance data has been performed according to a simple electrical equivalent circuit. An improved method for the evaluation of these model components has been applied. It has been found that the capacity of the interface has a higher value than that calculated from the Gouy—Chapman theory. This can be caused by the surface charge transfer reactions or by the limited application of Gouy—Chapman theory in the system studied, considered by other authors. The interface capacity found in the presence of picrate ions in the organic phase has higher values than that observed in the presence of supporting electrolytes only.

Electrochemical study of the transfer of tetraethylammonium and picrate ions across the water-1,2-dichloroethane interface

Abstract The results of chronopotentiometric and voltammetric studies of tetraethylammonium (TEA+) and picrate (Pi−) ions transfer from water to 1,2-dichloroethane (1,2-DCE) are presented for the diffusioncontrolled range. Diffusion coefficients and standard potentials of the ions studied have been determined. The distribution potential (the Galvani potential) of TEAPi in the water-1,2-DCE system calculated from them is compared with the experimental value determined using a suitable cell with transport and with the water-nitrobenzene interface data.

Differences between surface potentials of water and some organic solvents

A method of experimental estimation of the differences of surface potentials between organic solvents and water, Δswχ, by means of voltaic cells with transport (using the dynamic condenser method) is presented. The liquid junction potential from the organic side is eliminated by the use of nitrobenzene|water partition system containing tetraethylammonium picrate. The qualitative agreement of Δswχ data for the majority of 16 investigated solvents with Δswχ vales calculated from the Helmholtz equation, using bulk solvent dielectric constant, was found. Multilayer model of the surface potential is proposed.

Adsorption of aliphatic monoethers of ethylene glycol (alkoxyethanol) at the free water surface and at the Hg/solution interface

Abstract The adsorption of the monomethyl, monoethyl and monobutyl ethers of ethylene glycol at the free surface of water and at the uncharged Hg/solution interface has been investigated by means of surface and interfacial tension, and surface potential measurements. Results show that the adsorbability obeys Traubes rule at the air/solution interace but not at the electrode surface. The saturation surface concentration with adsorbate also differs at the two interfaces. The lateral interaction has been found to be essentially repulsive, which is interpreted in terms of hydrogen bonding of the polar groups to neighbouring water molecules in the adsorption layer, but definite quantitative differences are observed at the two interfaces. Enhanced electronic effects (dipole-dipole image interaction) and steric hindrance due to the presence of the solid wall are identified as conceivable reasons for the different behavior at the Hg/solution interface from that at the free surface of water.

Chronopotentiometric and voltammetric study of cesium ion transfer across the water—1,2-dichloroethane interface

Abstract Results of electrochemical studies of the cesium ion transfer reaction from water to 1,2-dichloroethane (1,2-DCE) for low ion concentration are presented. Measurements have been made by chronopotentiometric and cyclic voltammetry methods. The diffusion coefficient of Cs + in water saturated with 1,2-DCE and the half wave potential of Cs + at the water—1,2-DCE interface have been determined.