Electrolysis Duration Research Articles

Electrochemical fluorination of acetonitrile

Abstract An electrolytic cell with a gas dispersion disk below the nickel anode was used to study the effects of gas bubbling, electrolysis duration, anode potential, concentration of acetonitrile and pulsed electrolysis on the electrochemical fluorination of acetonitrile. Appreciable effects of the flow rate of helium flush gas and electrolysis duration on the current efficiency of CF3CN were observed. The time dependence of fluorination was discussed in connection with the film formation on the nickel anode. Pulsed electrolysis did not lead to improved yields of fluorinated compounds. From the analysis of the decay of anode potential, it was indicated that the extremely high anodic overpotential was mainly due to the potential operating across the anodic film of nickel which imposed the barrier for electron transfer. Based on the results obtained, the mechanism of electrochemical fluorination was discussed.

Electrolytic aluminum powder and its properties

1. An electrolysis apparatus and a process for the manufacture of electrolytic aluminum powder have been developed and tested on a large laboratory scale. 2. A study was made of the effect of electrolysis variables on the particle size distribution and particle morphology of electrolytic aluminum powder. It has been demonstrated that: a) lowering the temperature, increasing the initial current density, and reducing the duration of electrolysis decrease the proportion of coarse fractions in electrodeposited powder and narrow the range of particle sizes; b) with decreasing current density, the particle shape changes from elongated, dendritic to compact and, finally, lamellar; c) the powder particles are perfect single crystals. 3. Compared with powders produced by the atomization of liquid aluminum and mechanical comminution of solid aluminum, electrolytic aluminum powder has a larger specific surface, Its gravimetric density and aluminum oxide content per unit surface are less than those of the other powders. 4. The amount of the principal metallic impurities is less in electrolytic aluminum powder than in A99 grade aluminum.

Study of electrolytic labeling of fibrinogen with 131iodine by sephadex G-10 gel filtration

The labeling of human fibrinogen with 131I by the electrolysis technique of Rosa and coll. 2 was studied by Sephadex G-10 gel filtration of the product. Because fibrinogen may not be labeled in excess of 0.5 atoms of iodine per molecule fibrinogen, it was necessary to use a smaller amount of carrier iodide in the electrolytic cell than in the original method. Under these circumstances, there was a high side reaction of oxidation of iodide probably to iodate, resulting in a very low iodination yield. Under defined conditions of iodide concentration, pH and duration of electrolysis, a satisfactory product was prepared. Together with gel filtration, this method offers an accurate and elegant procedure for the preparation of iodinated proteins under controlled conditions. Prepared by this method, iodinated human fibrinogen had a biological half-life ( t 1 2 ), in turnover studies, of approximately 3.6 days in normal subjects, while in subjects suffering from venous thrombosis this half-life was markedly shortened to a mean value of 2.5 days.

AN ELECTROLYTIC RESPIROMETER FOR MEASURING OXYGEN UPTAKE IN SOILS

SummaryAn electrolytic respirometer and its accompanying pressure compensator are described together with some examples of performance. A simple transistorized detector circuit is used to automatically switch electrolysis and timing circuits to replace O2 used by a respiring sample. The respirometer is capable of measuring oxygen uptake within the range of 2 ml to 500 ml per 24 h. Oxygen uptake is calculated from the duration and rate of electrolysis. The accuracy of the method depends upon the maintenance of a stable current during electrolysis. The pressure compensator utilizes motor‐operated syringes to eliminate variation in air volume within the respirometer chamber due to changes in atmospheric air pressure.

Cathodic reduction of oxygen on smooth platinum in acid solutions

The mechanism of the cathodic reduction of oxygen on smooth platinum in 0·5 M H 2SO 4 solution has been studied on the basis of the current efficiency for H 2O 2 formation. H 2O 2 formation occurs at cathode potentials ≤680 mV (nhe), whereas the initial rest-potential lies at 960 mV. The current efficiencies for H 2O 2 formation depend on both cathode potential and duration of electrolysis, the maximum efficiency (99 per cent) being found at 450 mV with the shortest experiments (30 min). The proposed mechanism is at the highest potentials, the cathodic reduction occurs through the two reactions O 2 ads + H + + e → HO 2 ads (slow) and PtO + 2H + + 2 e → Pt + H 2O (fast). The first tends to inhibit the electrode surface progressively owing to the formation of adsorbed HO 2 radicals, and the second supports the greater part of the cathodic current: neither forms H 2O 2. At less noble potentials, the reaction O 2 + H + + 2 e → HO 2− begins, giving rise to H 2O 2 formation. At potentials ≤450 mV the process H 2O 2 + 2H ads → 2H 2O takes place, due to the intervention of adsorbed atomic hydrogen. The process O 2 + 2H ads → H 2O 2 can also overlap those just mentioned, and it may become the prevailing process when oxygen reduction proceeds in the presence of halide ions.

Lead Dioxide Anode in the Preparation of Perchlorates

Lead dioxide deposited on graphite or carbon was used to make anodes suitable for the preparation of sodium perchlorate from sodium chlorate. This type of anode has been used successfully in the presence of certain addition agents as a replacement for platinum anode. The influence of anodic current density, temperature, pH, current concentration, and duration of electrolysis on the current efficiency of perchlorate formation was studied. Current efficiency was found to depend on anode surface transformation, which occurred with repeated use. Such changes could be observed visually and were confirmed by anode potential measurements. High current efficiency could be obtained even under slightly alkaline conditions of electrolysis, but addition of fluoride improved results. Addition of fluoride together with sulfate (as sulfuric acid) had the maximum effect on current efficiency under acidic conditions of pH.

Quantitative bestimmung von kobalt an der rotierenden quecksilberelektrode

A modified mercury electrode was constructed and used as a cathode and, at the same time, as a container for the electrolyte. Its applicability as well as its advantages in comparison with other mercury electrodes have been studied on the determination of cobalt. On this rotating electrode cobalt could be quantitatively determined with a shorter duration of electrolysis. If determined conditions wire fulfilled, satisfactory results could he obtained in spite of a slight tendency for a subsequent oxidation of the cobalt from the amalgam. This justifies the recommendation of the rotating mercury electrode and of the method described for the quantitative determination of cobalt.

The polarization of zinc electrodes in neutral and acid solutions of zinc salts by direct and alternating currents.—Part. I

In the preceding paper it was shown that an amalgamated Line electrode made anode in an anode zinc sulphate solution undergoes considerable polarisation, and that tins polarisation can be more than overcome by the superposition of a sufficiently large alternating current of high frequency. Further, Allmand and Puri mention experiments in which a cathode of amalgamated zine had superposed on it alternating currents of intensities up to 200 times that of the direct current, and of frequencies varying between 20 and 400, the effect being to increase the polarisation of the electrode, which became more negative. These results were not to be anticipated from previous work, and it seemed that a closer investigation of the whole subject might not only explain the facts referred to, but perhaps throw fresh light on the mechanism of the electrode processes involved. As possible factors affecting the phenomena could be considered the amalgamation or otherwise of the zinc electrode, the presence or absence of free acid in the solution, the nature of the zinc salt ( e. g. , whether sulphate or chloride), duration of electrolysis, temperature, the absolute and relative values of the direct and alternating current densities, and tbs frequency of the alternating currents. The present paper contains an investigation of some of these points, working at room temperature and with zinc sulphate solutions, potential measurements have been made with amalgamated zinc electrodes in absence and in presence of free H 2 SO 4 , and with unamalgamated electrodes in neutral solution. Alternating currents and compound currents have been used, and a few experiments made with direct currents, frequencies varying between 50 and 11,000 have been worked with.