Chronopotentiometric Measurements Research Articles

Effect of ammonia on the Ni(Hg)/Ni(II) electrode reactions in aqueous chloride solutions

From steady-state cathodic and anodic polarization and chronopotentiometric measurements in 1 M chloride solutions containing ammonia, the reactions of the Ni(Hg)/Ni(II) electrode appear controlled by slow charge transfer with α=0.5 and n=2. The cathodic reaction mainly occurs from diammine nickel(II) species but also from ammine and diammine species. Quantitative kinetic data for the various species are presented and discussed.

Effect of ammonia on the Co(Hg)/Co(II) electrode reactions in aqueous chloride solutions

From steady-state cathodic and anodic polarization and chronopotentiometric measurements in 1 M and 2 M chloride solutions containing ammonia, the reactions of the Co(Hg)/Co(II) electrode appear controlled by slow charge transfer with α=0.5 and n=2. The cathodic reaction seems to occur equally fast from hydrated, ammine and diammine cobalt(II) species. Quantitative kinetic data for the various species are presented and discussed.

Effect of ammonia on the Ni(Hg)/Ni(II) electrode reactions in aqueous chloride solutions

Abstract The title subject has been studied using single pulse and chronopotentiometric polarization measurements on the Zn(Hg)/Zn(II) electrode and equilibrium measurements on the same and the Zn/Zn(II) electrode, mainly in 2 M NH 4 Cl with 0–0.3 M NH 3 . At low ammonia concentrations, the Zn(Hg)/Zn(II) reactions are found to occur in two consecutive charge-transfer steps with Zn(I) as intermediate, and with little or no participation of ammonia. At higher ammonia concentrations, however, nearly symmetric transfer by divalent zinc ion (α=0.5 and n =2) to and from diammine species appears to be the predominant charge-transfer step.

A Study of the Ionic Transfer across an Aqueous Solution Liquid Membrane Interface by Chronopotentiometric and Impedance Measurements

When an electric current passes across a boundary between a liquid membrane and an aqueous solution, it can give rise to a diffusion over-potential, to an ion transfer overpotential or to both. The application of chronopotentiometry and impedance measurement methods to study the ion transfer reaction at theses interfaces is described. With these methods, it is possible to determine some parameters of the ionic transfer kinetics: transfer coefficients, rate constants and to get information about the diffusion overpotential. On the other hand, the values of the interfacial double-layer capacitance can be determined by impedance measurements.

Electromigrational Depletion (ED) Chronopotentiometry Temperature Dependence of Diffusion in Molten BeF2‐LiF

New chronopotentiometric measurements with a Be anode in highly viscous molten 95 mole per cent mole per cent mixture are described in the range of temperature 564°–704°C. The transition is a result of electromigrational depletion (ED) of mobile nonelectroactive lithium ions. The equation of the chronopotentiogram is derived with the linear phenomenological equations of the thermodynamics of irreversible processes. Interdiffusion coefficients are derived from analysis of emf‐time data along the chronopotentiograms rather than from a transition time alone. The low values, 3 × 10−9–3 × 10−7 cm2/sec and high Arrhenius energy, 50.5 kcal/mol, are compared with the results of molecular dynamics computer experiments and the values of other transport coefficients in this and related systems.

Effects of thiocyanate on Ni(Hg)/Ni(II) and Ni/Ni(II) electrode reactions

Chronopotentiometric and stationary polarization measurements have been performed on mercury, nickel, and platinum electrodes in aqueous solutions of x M NiCl2+y M KSCN+(1−2x−y) M KCl at 25°C. Reaction products have been studied by electrochemical, radio-tracer, electron-microprobe, and X-ray diffraction techniques. At all three electrodes, cathodic reduction mostly gives a composite film of amorphous nickel sulphide and small nickel crystals. At mercury, however, this is preceded by the formation of a superficial layer of partly supersaturated nickel amalgam. Thiocyanate stimulates the charge transfer at this liquid amalgam and provides sulphur for the sulphide precipitation, but has little effect on the reactions at nickel crystals. The stimulation is more likely to be due to specific adsorption than to complex formation. Ni(I) appears as intermediate.

Effects of thiocyanate on Ni(Hg)/Ni(II) and Ni/Ni(II) electrode reactions

Chronopotentiometric and stationary polarization measurements have been performed on mercury, nickel, and platinum electrodes in aqueous solutions of x M NiCl 2 + y M KSCN+(1−2 x − y ) M KCl at 25°C. Reaction products have been studied by electrochemical, radio-tracer, electron-microprobe, and X-ray diffraction techniques. At all three electrodes, cathodic reduction mostly gives a composite film of amorphous nickel sulphide and small nickel crystals. At mercury, however, this is preceded by the formation of a superficial layer of partly supersaturated nickel amalgam. Thiocyanate stimulates the charge transfer at this liquid amalgam and provides sulphur for the sulphide precipitation, but has little effect on the reactions at nickel crystals. The stimulation is more likely to be due to specific adsorption than to complex formation. Ni(I) appears as intermediate.

Kinetics of the Zn(Hg)/Zn(II) electrode in acid chloride solution

From fast galvanostatic and chronopotentiometric polarization measurements in both directions of the Zn(Hg)/Zn(II) electrode at 25°C in 1 M chloride solutions of pH 3, it is found that charge transfer occurs in two consecutive steps (Zn(Hg)/Zn(I)/Zn(II)), that both steps are essentially symmetric, and that they are little affected by double-layer changes (including chloride adsorption) within the potential region covered (−1.2 to −0.8 V (SCE)). For both steps, quantitative kinetic data are presented and discussed.

Kinetics of the Zn(Hg)/Zn(II) electrode in acid chloride solution

Summary From fast galvanostatic and chronopotentiometric polarization measurements in both directions of the Zn(Hg)/Zn(II) electrode at 25°C in 1 M chloride solutions of pH 3, it is found that charge transfer occurs in two consecutive steps (Zn(Hg)/Zn(I)/Zn(II)), that both steps are essentially symmetric, and that they are little affected by double-layer changes (including chloride adsorption) within the potential region covered (−1.2 to −0.8 V (SCE)). For both steps, quantitative kinetic data are presented and discussed.

Kinetics of the Ni(Hg)/Ni(II) electrode in noncomplexing aqueous solution

From stationary, chronopotentiometric, and double-pulse galvanostatic measurements on the Ni(Hg)/Ni(II) electrode in 1 N chloride, acetate, and sulphate solutions of pH 1.4–5.3 at 25°C it is found that parallel charge transfer by the consecutive steps Ni(Hg)/Ni(I)/Ni(II) and the direct step Ni(Hg)/Ni(II) occurs in either direction, that stimulation occurs by adsorbed anions (Cl−>Ac−>SO42−) especially at anodic overvoltages, and that slight inhibition occurs by acid at cathodic overvoltages. Kinetic data are presented for each of the charge-transfer steps and for effects of anion adsorption. Some observations are moreover made on supersaturation of nickel in mercury and on the formation of NiHgx.

Kinetics of the Ni(Hg)/Ni(II) electrode in noncomplexing aqueous solution

From stationary, chronopotentiometric, and double-pulse galvanostatic measurements on the Ni(Hg)/Ni(II) electrode in 1 N chloride, acetate, and sulphate solutions of pH 1.4–5.3 at 25°C it is found that parallel charge transfer by the consecutive steps Ni(Hg)/Ni(I)/Ni(II) and the direct step Ni(Hg)/Ni(II) occurs in either direction, that stimulation occurs by adsorbed anions (Cl − >Ac − >SO 4 2− ) especially at anodic overvoltages, and that slight inhibition occurs by acid at cathodic overvoltages. Kinetic data are presented for each of the charge-transfer steps and for effects of anion adsorption. Some observations are moreover made on supersaturation of nickel in mercury and on the formation of NiHg x .

Electrochemical Behavior of Sulfide in Fused LiCl ‐ KCl Eutectic

Liquid sulfur has been reduced coulometrically in fused eutectic at 420°C. Nernstian behavior is observed for the cell C, , , . The standard potentials of the sulfur/sulflde couple at 450 °C with respect to the appropriate standard platinum reference electrode are −1.008, −1.039, and −1.219v on the molar, molal, and mole fraction scales, respectively. Voltammetric studies showed an anodic wave at +0.03v ascribed to and a cathodic wave at −0.92v ascribed to . The diffusion coefficient of the (poly)sulfide ion was found to be at 420°C by chronopotentiometric measurements. The observed blue color of sulfur‐sulfide solutions is ascribed to polysulfide ions.

Chronopotentiometric measurements of chemical reaction rates. II. Kinetics and mechanism of the dehydration of N-(p-hydroxyphenyl)hydroxylamine

Chronopotentiometric measurements of chemical reaction rates. II. Kinetics and mechanism of the dehydration of N-(p-hydroxyphenyl)hydroxylamine

On the impedance of galvanic cells: XXII. Determination of the parameters of the double-layer impedance from the electrode impedance and the electrocapillary curve in the case of specific

The electrode impedance in the case of specific adsorption of the electroactive species is discussed, critically applying the charge separation model of delahay. Comparison with experiments performed with the In 3+/In(Hg) couple in 1 M KCNS, comprising impedance, chronopotentiometric and surface-tension measurements, is given. An improved theory of the relation between surface tension and double-layer parameters is presented, leading to a better agreement with experiment. Consistent values are obtained for the surface excess of In 3+. It is shown that the linear relation between the value of thè double-layer capacity and Tl + concentration that has been found earlier at low concentrations, also holds for concentrations up to 2 m M. The consequences of the application of a modified treatment given by reinmuth, are discussed.

Chronopotentiometric and Chronocoulometric Measurements of Adsorption of Lead and Mercury(II) at Mercury Electrodes.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChronopotentiometric and Chronocoulometric Measurements of Adsorption of Lead and Mercury(II) at Mercury Electrodes.R. W. Murray and D. J. GrossCite this: Anal. Chem. 1966, 38, 3, 392–404Publication Date (Print):March 1, 1966Publication History Published online1 May 2002Published inissue 1 March 1966https://doi.org/10.1021/ac60235a006RIGHTS & PERMISSIONSArticle Views93Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

The Electrodeposition of Coherent Deposits of Refractory Metals: III . Zirconium

Exploratory experiments in chloride, bromide, and mixed chloride‐fluoride melts always produced dendritic zirconium deposits. Pure fluoride systems consisting of dissolved in alkali fluoride solvents produced coherent deposits of metal, some as thick as 0.1 in. with no indication of reaching a thickness limit, on electrolysis at 750 °C and 30 ma/cm2 cathode current density. Analysis and material balance experiments showed that reduced compounds were absent in these fluoride systems. Chronopotentiometric measurements indicate that the zirconium is deposited from the tetravalent state in a single four‐electron step which would appear to be irreversible. The addition of , , and to a working zirconium bath results in the deposition in coherent form of the compound and the alloys and . The plate was 11 mils thick and showed no evidence of reaching an upper limit of thickness, while both alloys were smooth and fine‐grained in nature, the deposit showing a particularly interesting rhythmic banded structure.

Electrochemical oxidation of dissolved sulphur dioxide at platinum and gold electrodes

The electrochemical oxidation of dissolved sulphur dioxide has been studied at platinum and gold electrodes using voltammetric, chronopotentiometric and galvanostatic measurements. The effects of electrode preconditioning and solution pH on the mechanism and the kinetics of the electrode reaction have been determined. Oxidation of sulphur dioxide occurs by two mechanisms, one a pure electron-transfer process and the other a chemical oxidation by electrolytically formed metal oxide. With an activated platinum electrode the electron-transfer mechanism is the predominating process. The electron-transfer process is also predominant at an active gold electrode. For this process the rate-controlling step as well as the over-all process is a two-electron oxidation.

The influence of hydrolysis on the deposition and CO-DE-position of iron-group metals (Fe, Co, Ni) at the dropping mercury electrode

The deposition and co-deposition of iron(II), cobalt(II) and nickel(II) ions were studied polarographically in weakly acid (pH 3–5.5) solutions. Variation of pH in this region does not affect the waves. By adding oxygen to the solution, high pH values were generated at the electrode surface (O 2 + 2 H 2O + 4 e → 4 OH −) leading to hydrolysis of the discharging metal ions. Hydrolysis not only reduces the concentration of the discharging species due to Me 2+ + 2 OH − → Me(OH) 2 ↓ but also leads to adsorption of hydroxides at the interface. Chronopotentiometric measurements showed that about 3 · 10 −10 moles/cm 2 Fe(OH) 2 are adsorbed at the electrode. Hydrolysis changes the rate of single metal discharge only slightly, but has a strong effect on the co-deposition of metals. The discharge of one metal can be suppressed by the presence of a second iron-group metal. Ferrous ions cause the strongest suppression followed by cobaltous ions. The same sequence (Fe 2+ > Co 2+ > Ni 2+) is found in the suppression of Tl + discharge. This sequence is interpreted on the basis of adsorption measurements.

Studies on the Electroreduction of Uranyl (VI) in Molten Equimolar KCl ‐ NaCl by Chronopotentiometric and Electrode Impedance Measurements

The reduction of to in molten salt at 716°C has been shown by chronopotentiometry to be diffusion controlled at a platinum electrode. Furthermore, the potential‐time curves indicated that the reaction occurred in two steps at nearly the same potential. This observation was verified by measuring the pseudo capacity of the polarized cathode as a function of its potential for which a plot of the data shows two peaks in capacity. The first was found to be symmetric with a concentration‐independent potential, which is indicative of an electrode reaction producing a soluble product. The second peak was asymmetric with a concentration‐dependent potential, which is indicative of an electrode reaction producing an insoluble product. These observations suggested that the electrode reaction proceeds by a reduction of to followed by the reduction of the to Additional verification of this mechanism was provided by the reduction of by to yield a stable solution of . The heterogeneous rate constant for the reduction of to was estimated to be 2 cm sec−1, but a value for the reduction of could not be determined because of the solid deposit. The diffusion coefficient was estimated from the chronopotentiometric data to be .

Kinetics of aqueous oxidation of tantalum from chronopotentiometric measurements.

Kinetics of aqueous oxidation of tantalum from chronopotentiometric measurements.