Danilo Cozzi

A cell with solid microelectrode with periodical renewal of the diffusion layer

Abstract A new cell with a platinum microelectrode is described: the diffusion layer is renewed by the periodical movement of the electrolyte caused by the displacement of a piston. A magnetic field causes the piston displacement. The diffusion current intensities, both instantaneous and average, may be calculated with a good agreement by the simple equation of spherical diffusion. The cell allows many possibilities of regulation both in the period of the electrode washing and in that during which the electrode is in the stationary electrolyte. Moreover, the flow speed of the solution may be easily regulated. This new cell is particularly interesting for the study of many electrochemical processes characterized by a high redox potential.

The mechanism of ion exchange with algenic acid

Abstract The exchange mechanism which determines the retention capacity of alginic acid has been investigated. Chromatographic, pH, and viscosity measurements, performed with several metal ions, have permitted us to show that ion exchange is not the only mechanism but that the influence of the two vicinal hydroxyl groups on the retention capacity of alginic acid is also important.

Alginic acid, a new thin layer material : Part I

Abstract Alginic acid is proposed as a new stationary phase for TLC. The effects of the distance moved by the solvent front, temperature, hydrogen ion concentration of the eluents and the thickness of the layers on the R F values of some common elements have been extensively investigated. Characteristic R F values of some common elements are reported. The chromatographic properties of alginic acid and carboxymethylcellulose were compared.

The polarographic behaviour of rhodium(III) chlorocomplexes

Abstract It has been experimentally proved, by coulombometric measurements, that Rhodium(III) chlorocomplexes are reduced to metal at dropping mercury electrode, and we have given evidence of the reversibility of reduction process. Further, it has been studied the variation of the half wave potential as a function of chloroions activity in acid solution. The formation constants of complexed ions: RhCl+2RhCl2+RhCl3RhCl4−RhCl5−2RhCl6−3 have been computed and the following values derived: K 1 = 2.8 · 10 2 , K 1 = 3.5 · 10 4 , K 3 = 8.3 · 10 3 K 4 = 1.2 · 10 7 , K 5 = 5.6 · 10 4 , K 3 = 2.7 · 10 8

Electrostatic effect of specifically adsorbed electroinactive ions upon electrode processes

Summary The reduction rate kf of BrO4− in the presence of halides and pseudohalides at sufficiently negative potential with respect to the point of zero charge satisfies the well-known Butler-Volmer equation corrected for diffuse-layer effects according to Frumkin. On the other hand at less cathodic potentials, where halide and pseudohalide adsorption becomes appreciable, the rate constant kf at constant applied potential E, once corrected for diffuse-layer effects according to Frumkin, still depends on the charge density qi due to the specifically adsorbed halide and pseudohalide ions. Thus in the presence of Cl−, Br−, SCN−, and N3− the logarithm of kf,d=0 (where kf,d=0 denotes the rate constant at constant E corrected for diffuse-layer effects) decreases linearly with |qi, at least for |qi|>∼10 μC cm−2. The slopes of the various log kf,d=0vs. qi plots are in satisfactory agreement with a theoretical treatment proposed by two of the authors1,2, which accounts for the electrostatic interactions between the activated complex for the electrode reaction and the neighbouring specifically adsorbed ions within the compact layer.

Thin-layer chromatographic and electrophoretic behaviour of primary aromatic amines on weak ion exchangers

Abstract The authors have studied extensively the thin-layer chromatographic and electrophoretic behaviour of primary aromatic amines on weak ion exchangers such as alginic acid and carboxymethylcellulose. The eluents were solutions of organic and inorganic acids, water, buffer solutions and aqueous organic solvents. The R F values were correlated with the acidity and basicity of many amines.

Ion-change thin-layer chromatographic separation of amino acids on alginic acid

Abstract Alginic acid was tested as an adsorbent in the ion-exchange chromatography of 31 amino acids on thin layers, the eluents being hydrochloric acid, acetic acid, water, potassium nitrate solutions and aqueous organic solvents. The behaviour of the amino acids on alginic acid was compared with their behaviour on carboxymethylcellulose. An ion-exchange mechanism operates in the case of basic amino acids. As regards the neutral amino acids, their affinity for alginic acid seems to be influenced by steric hindrance.

Thin-layer chromatography of metal ions on alginic acid : Part II

Abstract The R F values of 41 elements, some in two oxidation states, have been determined by TLC on alginic acid. The effect of the nature and concentration of the acids employed as eluents was extensively investigated.

A study of the hydrogen ion concentration gradient on alginic acid thin layers

Abstract The various types of hydrogen ion concentration gradients formed along a chromatographic layer during elution with mineral acids, buffer solutions, and neutral salt solutions were thoroughly investigated. The results indicate that the formation of such gradients may be attributed to a process of absorption by the substrate and to ion-exchange. Various analytical applications are envisaged.

The bubbling platinum electrode

Abstract The authors present, and give examples of the use of, a new type of platinum electrode, the bubbling platinum electrode, which may be used in place of the dropping mercury electrode for the study of the electrochemical properties of substances with high redox potentials.