“AKVA” general-purpose automated voltammetric complex for electrochemical research and analysis

Kenzin, V. I.; Zamyatin, A. P.; Bek, R. Yu.; Novitskii, S. P.

doi:10.1007/bf02512116

Cited by 3 publications

(5 citation statements)

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“…According to [5], the equilibrium potential of the reaction HPb + 2Â + ç 2 é = Pb + 3 OH -in alkali solutions may be calculated with the equation E eq = -0.54 + RT /(2 F ) ln ( c 1 / ) , where c 3 is the concentration of hydroxide ions. As lead ions form no strong complexes with cyanide ions, the magnitude of E eq in the solutions studied must be close to − 0.65 V. In the above solutions, the equilibrium potentials of thallium (-0.65 V [6]) and gold (-0.61 V [4]) have nearly the same values, while the equilibrium potential of silver is displaced to somewhat more positive potentials, specifically, to almost -0.5 V.…”

Section: Methodsmentioning

confidence: 86%

“…The same pattern occurs at other current densities, which were varied in the interval of i/i d from 0.1 to 0.6. 4 Parameter i d in this ratio is the limiting diffusion current by silver ions in the solution under study, which equals nearly 3 mA cm -2 [13]. No sections where the polarization would decay on the scale shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The technique in question was described in [3]. When coupled with a computer-based meter of the i -E -t dependences [4], the technique permits automatic renewal of the electrode surface and then measurement of the E , t curves at i = const with allowance for the time period ∆ t that elapsed since the renewal of the electrode surface until the switching on the current, i.e. until the beginning of measurements of a potential transient.…”

Section: Methodsmentioning

confidence: 99%

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Potential transients on a renewed electrode as a source of information on the surface concentration of catalytically active adatoms

Bek

Shuraeva

2005

Russ J Electrochem

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Potential transients on renewable gold and silver electrodes in cyanide solutions containing catalytically active ions of lead and thallium are measured. The transients are recorded both on freshly renewed electrodes and on renewed electrodes kept in solution for specified time periods ∆ t . The behavior of transients following a change in the concentration of lead and thallium ions, current density, and ∆ t qualitatively conforms to regularities that could be expected if the catalytically active adatoms were inserted into the deposit similarly to the admixtures. Methods for determining coefficients of capture of such adatoms by the growing metal deposit are suggested. Factors that hamper determination of these coefficients and make it worthwhile to select a method for their determination that would use potential transients are considered. The capture coefficient for the incorporation of lead adatoms in the growing silver deposit is nearly 20 times that for gold.

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Section: Methodsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Potential transients on a renewed electrode as a source of information on the surface concentration of catalytically active adatoms

Bek

Shuraeva

2005

Russ J Electrochem

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“…Experiments were performed at a temperature of the solution equal to 24°ë , which was maintained with the aid of a thermostat. Polarization curves and dependences of current i on the electrolysis duration t at given values of the electrode potential E were obtained with the aid of a program-controlled measuring complex that was described in [12,13]. The time that would elapse between the instant the cutting-off was done and the measurements were begun was monitored.…”

Section: Methodsmentioning

confidence: 99%

Gold Dissolution Electrocatalysis in Thiourea Electrolytes in the Presence of Chemisorbed Sulfide Ions

2005

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Adding a microscopic quantity of sodium sulfide (~ 10 -5 M) into acid solutions of thiourea leads to a dramatic acceleration of anodic dissolution of gold. The acceleration effect is greater at larger thiourea concentrations ( c ) and longer times of the electrode contact with solution ( ∆ t ) before the beginning of measurements. The effect diminishes after a polarization curve passes through a maximum at E Ӎ 0.5 V. Regularities of the gold dissolution in a solution containing 0.1 M thiourea and 0.5 M H 2 SO 4 at given values of c and ∆ t are studied with use made of the technique of renewing the electrode surface by cutting off a thin surface layer of metal. The discovered regularities are given an explanation which is based on the assumption that the dissolution process is catalyzed by sulfide ions adsorbed on the electrode surface.

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“…Coupled with a computer-controlled recorder of i-E,t curves [15], it automatically renewed the electrode and recorded potential transients at i = const.…”

Section: Introductionmentioning

confidence: 99%

Electrode kinetics in cyanide silver-plating electrolytes at different surface coverages by lead adatoms

Bek

Shuraeva

2005

Russ J Electrochem

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INTRODUCTIONIn a previous work and in accordance with [1][2][3] it was demonstrated [4] that the silver deposition in cyanide solutions accelerates in the presence of microscopic (~10 -5 to 10 -4 M) quantities of lead compounds. Hydroxy compounds of lead affect the gold electrodeposition similarly [5][6][7], which was linked with electrocatalysis of this process by lead adatoms. Lead atoms undergo adsorption on silver as well [8]. Therefore, one could expect that the effect of lead compounds on the silver deposition has the same nature that in the gold deposition. Approaches to studying the deposition and dissolution while monitoring the surface coverage θ by adatoms of catalytically active metals [7,9,10] are used here to examine how microscopic quantities of lead compounds affect the electrode kinetics in cyanide silver-plating electrolytes. EXPERIMENTALObviously, kinetic parameters of an electrochemical process in the presence of a catalyst are dependent on its concentration in the reaction zone, i.e. at the electrode surface. Therefore, to determine these, it is necessary at the very least to monitor the constancy of θ when taking measurements. In our case the catalyst is lead atoms, which form at the silver surface out of anions H ê b present in the solution. The adsorption of atoms of "foreign" metals at a metal substrate surface is known to begin at potentials that are by several hundreds of millivolts more positive O 2 -than the equilibrium value of this indicator, i.e. at an "undervoltage" [8]. The equilibrium potential of the reaction HPb(1)Here, c 1 and c 2 are concentrations of hydroxy compounds of lead and hydroxide ions. In most of the solutions under study ( c 1 = 10 -5 -10 -4 M), which contained 0.05 M AgNO 3 , 1.0 M KCN, and 0.3 M KOH as basic components, the equilibrium potential of silver is close to -0.5 V. Thus, as lead ions form no strong compounds with cyanide ions, E eq Ӎ -0.65 V at c 2 Ӎ 0.3 M. Hence, lead adatoms might affect both the initial portion of an anodic polarization curve and the entire cathodic silver deposition curve, for some atoms of lead remain on the surface despite its co-deposition with silver.The surface density of lead atoms may be determined from the balance of supply rates of hydroxy compounds of lead (it is limited by, more likely than not, diffusion) and the inclusion of lead atoms into the deposit [7,9,12] and described by the equation(2)Here, D is the diffusion coefficient for lead ions in solution; δ = 0.01 cm is the effective diffusion layer thickness [9]; Γ lim Ӎ 3 × 10 -9 mol cm -2 is the limiting silver surface coverage by lead atoms; b Ӎ 0.09 cm 2 mA -1 s -1 is a "capture" coefficient [12]; and i is the current density, in mA cm -2 [9].Abstract -Effective values of exchange current i 0 , cathodic and anodic transfer coefficients α and β , and cathodic and anodic reaction orders with respect to cyanide ions ( P c , P ‡ ) are measured in cyanide silver-plating electrolytes at different surface coverages by lead adatoms θ . With increasing coverage, i 0 and α...

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“AKVA” general-purpose automated voltammetric complex for electrochemical research and analysis

Cited by 3 publications

References 0 publications

Potential transients on a renewed electrode as a source of information on the surface concentration of catalytically active adatoms

Potential transients on a renewed electrode as a source of information on the surface concentration of catalytically active adatoms

Gold Dissolution Electrocatalysis in Thiourea Electrolytes in the Presence of Chemisorbed Sulfide Ions

Electrode kinetics in cyanide silver-plating electrolytes at different surface coverages by lead adatoms

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