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Experimental investigations of corrosion behavior of glassy metal Fesolfco in 1.0 mol dm"3 H2SO4 are described. Results are presented on voltametric and impedance measurements in three distinct anodic potential ranges. Two relaxation processes have been observed and identified: i) a kinetically controlled interfacial charge transfer mediated by adsorption of some intermediate species in the active dissolution range; ii) the same process, but with a blocking effect due to adsorption of the passivating species in the passivation or transition range; and iii) ion migration in a high electric field within the passive layer with adsorption of surface states in the passive range. Using a general impedance of the resistance, the measured impedances have been characterized in terms of parameters of compatible equivalent circuits.

Cyclic voltammograms obtained for the reduction and reoxidation reactions of nickel cyanide complex with and without an excess of free cyanide in solution are shown and discussed. These reactions could best be described as an ECE mechanism, accompanied by a fast equilibrium disproportionation reaction between the two Ni(I) complex intermediates.

Relaxation times were measured for the surface tension relaxation of spread and soluble surface films at the water/air interface. Measurements were done in a modified Langmuir trough with a Wilhelmy Pt sensor attached to an electrobalance using surface sweeping rates between 6.4 and 57.6 Hz-1• The relaxation times were determined in the stationary state from the phase angle between the perturbation function (surface sweeping) and the response function (dynamic surface tension). The calculated values for the relaxation times of oleic acid films were between 0.25 and 1.25 s, and were inversely proportional to both the rate of sweeping and to the concentration of molecules in the surface film. For the soluble surfactant, sodium dodecylsulfate, the relaxation times were reaching a minimum value of 0.2 s, at a bulk concentration between 9.1 and 18.3 ~t mol dm-3•

The case of a preceding chemical reaction in a chronopotentiometric experimentunder second order conditions was studied by digital simulation and experimental verification. Chronopotentiometry is sensitive enough to distinguish second from pseudo-first order preceding chemical reaction, only when the ligand ion concentration . is less than five times higher than the electroactive metal ion concentration. These findings are based on experiments of reduction of Ti(IV) in thiocyanate solutions.

The influenoe of ionic surface active agents (SAA), represented by some aliphatic straight chain amines and acids, on the zeta-potential of Ag! precipitates has been studied. It has been shown that SAA ions are zeta-potential determining in a narrow concentration region only'. This region is independent of the pl of the solution. In case the sign of charge of the SAA ion is the same as that of the original precipitate there is no marked influence on the zetapotential. Whether the sign of the zeta-potential is determined by the activity of the constituent ions in the solution or by the concentration of SAA ions, the magnitude of the zeta-potential is determined by the sign of charge and concentration of the counter ion only. The total potential difference and the zeta-potential are brought about by two differe nt, independent processes.

A description of an electroosmotic apparatus based on the principle of a micro bubble flow meter is given. Statistical analysis of some results obtained on quartz particles in aqueous and methanolic solutions of potassium chloride is given, the mean standard error beeing about 7%.

Using radioactive t32Eu 3+ a nd 6oco2 + indicato11s the adsorption of these ions on the surface of silver iodide precipitates was measured. The experiments were performed in the equivalency region, from pl 5.5 to pAg 5.5. The measurem e nts indicated a constant amount of counter ions o f about 2 mgequiv .. /gmole of Ag! adsorbed from pl 5.5 to pl 7. At higher pl a gradual d esorption occurs, and at pAg 7.3 the zero point of adsorption i s attained. The adsorbed amount is independe nt of the concentratio n of the counter ion in the solution in the range from the coagulation concentration up to ten times its value. By aging the precipitate or by some other kind of pretreatm e nt the adsorbed amount of counter ions is d ecreased. In addition the zero point of adsorption is shifted from pAg 7.3 to pAg 7.1. Series of experments were performed to establish the adsorption-desorption equil ib11ia of one ion in presence of various concentrations of a second one.

The method originally employed by . Hurd & Hackermann to me asure streaming currents on single capillaries has been modified for measurements on porous diafragms of precipitates. An application of microvolt amplifiers and pressure transducers in connection with chart recorders to record the streaming current - pressure relation is described.

A systematic study of the influence of exchange of ions on the surface of silver iodide precipitates on the elektrokinetic potential (EKP) was undertaken. Examples of the exchange o:f ions of valencies 1 :2, 1 :3, 1 :4, 2 :4 and 3 :4 are given. At higher activity of potential determining ions in solution, at pl= 3, larger changes in the EKP were measured. At the same pl effects of specific adsorption o:f Th4+ were found. The conclusion is drawn, that the exchange of ions at the surface bears no direct, simple relation to the EKP.

E. Lederer i M. Lederer: Chromatography. (K. Balenović) K. Arima, W. J. Nickerson, M. Pyke, H. Schanderl, A. S. Schultz, A. C. Thaysen i R. S. W. Thorne (urednik W. Rom an): Yeasts. Hag 1957. (V. Johanides) Prace Konferencji Elektrochemicznej (Radovi elektrokemijske konferencije), Varšava, 15.-19. listopada 1955. (V. Pravdić)

An attempt is described to determine the charge densities at different layers of the surfaces of glass. Three different techniques were used: the heat-of-immersion technique, the electron spin resonance hyperfine splitting measurements, and the electrokinetic streaming potential or current technique. Estimates of the charge densities at the various interfaces show the structure can be subdivided into the high and low charge portions. The heat-of-immersion technique, looks into the actual solid surface: there the charge density is estimated at in excess of 1014 unit e-charges per cm2• The hyperfine splitting of the 107Ag ESR spectrum assumed due to the electrostatic field at the site of the localized atom position: a charge density of 0.7 to l.3Xl013 is estimated. It is assumed that the Ag atom is localized in the gel-like layer- solution interface. The excess counter-ion charge in the diffuse part of the double layer in the liquid phase is estimated at 3 to 7 X 1012• Thus, the high charge density plane is the interface solid-gel layer. The estimates are based on independent models of the interface structure, widely accepted in literature, although not entirely free of arbitrary assumptions.

Proton conductivity is established in lithium sulfate monohydrate by electrolysis.experiments in the solid state. This effect is discussed in relation to the large amplitude oscillations of the water molecule as evidenced by proton magnetic resonance measurements at different temperatures. The importance of unidirectional chainlike structure of hydrogen bonds in this substance is emphasized, and several implications of the proton conductivity are mentioned.

The purpose of this work was to investigate the possibility of preparation of uranium dioxide by electrochemical reduction of uranium(VI) from alkali carbonate solutions. There are many interesting features in deciding whether or not the electrochemical process is applicable to certain conditions of solution equilibria in the uranium-carbonate system. The study ·of the reduction of uranium(VI) from carbonate solutions has been undertaken to determine the reduction potential-current density relationship, the current efficiency, and the O/U ratio in the precipitated uranium dioxide, for which only scarce data are available in the literature.

It was suggested in a preceding communication1 that protonic conduction may be operative in borax. Coulometric measurements have so far been used twice as evidence for such a mechanism of electrical conductivity. In the case of cetyl alcohol Kakiuchi et al.2 measured the pressure of the gas evolved on the cathode and verified spectroscopically that it was H 2• Decroly et al.8 measured the gas volumetrically (in a capillary) on the cathodic side of an ice crystal.

A streaming potential device for work with dispersed material is described. The use of a vibrating condenser electrometer-amplifier in connection with a paper strip recorder gives the possibility to perform measurements in short time and with small volume of liquid. Statistical analysis of the results on quartz particles of three different sizes in KCl solutions (1 X 10-s to 5 X l0-3 N) is given. The determination of the ~-potential with this device and experimental technique can be performed with a standard error of about 5%.

Oxidation - reduction reactions of uranium(V) and (VI) in sodium and caesium carbonate solutions at high pH were studied using the chronopotentiometric technique. Uranium(V) formed by electrolysis of uranium(VI) at constant potential is stable, its rate of disproportionation negligible. The apparent standard redox potential (uncorrected) of the U(VI) /U(V) couple was found to be - 0.760V vs. S. C. E. in 1 M Na2C03 and pH = 11.5. The uncorrected overall transfer coefficients for the oxidation of U(V) and rereduction of U(VI) were: 0.64 and 0.42 in 1 M Na2C03, and 0.47 and 0.47 in 0.5 M Cs 2C03• The formal rate coefficients for the oxidation and re-reduction of 1 mM bulk U(V), referred to the N. H. E. were: 2.1 X 10-9 and 2.7 X 10-s cm/sec in 1 M Na2C03, and 8.0 X 10-9 and 1.1 X 10 -s cm/sec in 0.5 M Cs2C03• Narrow concentration limits for the solubility of uranium complexes and the relatively low concentration sensitivity of the chronopotentiometric technique render precise quantitative calculations and corrections for double layer effects or counter-ion association rather difficult.

The electrokinetic potential was measured for uranium oxide samples of different atomic ratios O/U, ranging from 2.00 to 2.45. It was found that the differences in the oxidation states correspond to small but significant differences of the electrokinetic potential, with higher values. for lower oxidation states. The reversal of sign has been observed for positive suspensions at pH = 3.3 by the phosphate counter ion. The electrokinetic po tential was found to be independent of the us+ /U4+ ratio in the solution, indicating that these ions are not potentia l determining.

The zero point of the ~potential (streaming potential and electroosmosis) on AgI coagulated with a neutral electrolyte lies in the region between pAg 5.1 and 6.2 in which region it is irreproducible. The shift of the zero point towards lower pAg values is smallest for the 3-valent and highest for the monovalent cations. The ~potential is independent of the pI value between 3 and 9. The change in concentration of the neutral electrolyte from 10-' to 10-2 N lowers the ~potential for a factor of 3 to 4. The relation between the ~potential and the coagulation with neutral electrolyte and the isoelectric coagulation is discussed.

The precipitation of uranium(IV) from sodium carbonate solutions has been studied. Uranium(IV) has been prepared by electrochemic al reduction at controlled constant potential at the -mercury cathode. From the stable solution uranium(IV) precipitates as hydrous oxide. The dependence of the degree of precipitation of uranium(IV) on the composition of the solution is given, considering the carbonate to uranium concentration ratio, th e total sodium carbonate concentration, and the pH of the solution. Th e precipitation was induced and performed also by raisi ng the temperature up to 60° C. Ex perimental limits of the solubility of uranium(IV) carbonate complex es, at 60° C and at pH = 9.5 and 10.3, indicate the possibil ity of the existence of the uranium(IV) in solution predominantly as the [U(OH)2 (C03) 4]-6 complex .