The influence of the surfactant in a perfluorinated emulsion on the determination of thallium,lead and cadmium by anodic stripping voltammetry

The effects of the Pluronic F-68 surfactant in the emulsion are described. A study of the two electrode processes in the measuring cycle shows that the deposition stage is not affected provided that the deposition potential is negative enough. The peak potentials for Pb²⁺ and Cd²⁺ are slightly shifted and the stripping currents are seriously decreased when the differential pulse (d.p.) mode is used, but the inhibition is independent of metal ion concentration and deposition time, and the d.p. mode is suitable for quantitative work. The performance of hanging drop and film mercury electrodes is compared.     

Silver based mercury film electrode: Part II. The influence of aging of electrode on the electrode processes of various metal ions

The cyclic voltammetric behaviour of 8 metal ions at solid silver amalgam electrodes prepared by aging of a thin silver based mercury film electrode (SBMFE) and by deposition of silver and mercury on platinum were investigated. It was established that such electrodes behave in relation to some metals (Pb, Bi, Sn) similarly as silver electrodes i.e. the cyclic curves obtained with these electrodes at concentration 10^?3M range show a prepeak-postpeak system corresponding to deposition and dissolution of the monolayer of deposit. On the other hand under the same conditions no prepeaks were observed for cadmium, zinc and thallium. In all cases investigated the heights of anodic stripping peaks were lower on curves obtained with aged SBMFE than on those obtained with fresh SBMFE having a mercury layer 1 μm thick.     

Electrochemistry of quinizarine adsorbed on a glassy carbon electrode in aqueous solutions

The electrochemistry of quinizanne in aqueous solutions, adsorbed on electrochemically pretreated glassy carbon electrodes, is described. The anodic and cathodic reversible reactions are followed by physical and chemical processes, respectively. The desorption of the fully oxidized species from the electrode was assigned to the follow-up process in the anodic region. The follow-up reaction at the more negative potentials is ascribed to tautomerization. in which the central hydroxyl group(s) participate. When the range of the reduction is expanded, two additional irreversible reduction waves are observed. A full mechanism of the electrode reactions is proposed. Intramolecular hydrogen bonds and the pH of the aqueous solutions play an important role in the rationalization of the overall mechanism. The “electro-chemical label” concept is used to study the progress of the electrode reactions, and to evaluate the intermediates and the products which are confined to the electrode surface.     

The polarographic behaviour of some elements in concentrated calcium chloride solution : The polography of chromium,nickle and lead

This paper discusses in detail the polarography of chromium, nickel and lead in 5M calcium chloride. The conditions for polarography are laid down and the theoretical aspects of the results obtained with a single-sweep cathode ray polarograph are discussed. The mutual interference of the elements is detailed and recommendations for their determination in the presence of one another are presented.     

The adsorption structure of nonionic surfactant on the sessile mercury electrode in a thin liquid film

In relation to a colloid stability, the adsorption structure of the Stern layer on a sessile mercury electrode in a thin liquid film of nonionic surfactant was investigated by measuring the double layer capacitance. The Stern capacitance on the electrode in the film could be detected when the measuring frequency used was low, for the resistance of the film was not extremely high but of the order of several thousand ohm. It was found that the adsorption structure of nonionic surfactant in the thin liquid film shows a stratification different from that of bulk.     

Analytical applications of triethylenetetraminehexaacetic acid : Part I. the influence of TTHA on the polarographic reduction of some metal ions

The influence of triethylenetetraminehexaacetic acid (TTHA) on the d.c. and square-wave polarographic curves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), Zn(II), Fe(III), Bi(III), Sb(III), As(III) and In(III) has been investigated in several supporting electrolytes over the pH range 1–13. The E_{$\text{1}\text{2}$} and E_p values with and without a 10-fold excess of TTHA are compared. Some analytical applications are suggested.     

Fundamentals of lead-acid cells: Part XIII. The influence of additives on the charge and discharge processes of the negative electrode

The effects of BaSO₄ and a lignosulphonate on the normal discharge and charge processes of a porous lead electrode have been examined by the potential-step technique. Here, BaSO₄ is shown to exert a major electrochemical effect on the discharge reaction while the lignosulphate is found to increase the available active surface area of the electrode.     

Kinetics of electrode processes on a bismuth electrode in acid solutions containing thiourea and formamidine disulphide

A study of the mechanism by which bismuth is electrodissolved in an aqueous solution of thiourea on the background of H₂SO₄ demonstrated that, in the thiourea concentration range 0.001 M < c < 0.5 M, a current oscillation is observed in cyclic voltammograms at E ≈ 0.4–0.3 V when the potential is swept from the anodic to the cathodic region. This oscillation is due to the loosening of the passivating film formed in the anodic process. It is shown that thiourea is not oxidized to formamidine disulphide at the bismuth electrode. thiourea and formamidine disulphide have mutually opposite effects on the height of the cathodic peak: the peak current falls with increasing thiourea concentration and grows with increasing formamidine disulphide concentration. According to the results of an X-ray fl uorescence analysis, sulfur is formed on the bismuth electrode upon its prolonged polarization of in a 0.5 M solution of thiourea. An explanation is provided for the experimental facts observed in the study.     

Electron transport in biological processes: Electrochemical behaviour of ubiquinone Q,10 adsorbed on a pyrolytic graphite electrode

The E-pH diagram has enabled us to obtain the acid-base constant of ubiquinone and the equilibrium potential at pH = 0 for the different couples participating in the process of quinone adsorption on a pyrolytic graphite electrode in aqueous buffered media. The electrochemical behaviour found for ubiquinone may explain in part the in vivo ubiquinone processes. The molecular contour of deoxyribonucleic acid changes the stability of the semiubiquinone intermediate, as shown by chemiluminescence and binding experiments.     

Preparation and in vitro characteristics of a blood substitute based on pyridoxylated polyhemoglobin

Stroma-free hemoglobin (SFHb) is prepared from outdated blood. Red cells are washed, lysed in hypotonic phosphate buffer, and stromal lipid is then removed by toluene extraction and high-speed centrifugation. Pyridoxal-phosphate (PP) added in a 4∶1 molar ratio to deoxygenated SFHb, is covelently linked across the polyphosphate binding site of the Hb tetramer by reduction with NaBH₄ under N₂ for 18 h. Excess reagents are removed by dialysis. Subsequent crosslinking using 5.0% glutaraldehyde in the presence of lysine for 12–36 h yields soluble, macromolecular polyhemoglobin (PolyHb). Progress of the reaction is monitored by gel chromatography. In vitro work shows that different molecular weight (MW) PolyHb can be produced, ranging in weight from 130,000 to over 1,000,000. Intermediate MW PolyHb (<600,000) remains stable for months at 4°C, withstands prolonged incubation at 37°C, and has a viscosity similar to blood. SFHb has a lowP ₅₀=15 torr, which has been raised to 26 torr by pyridoxylation. When PP-SFHb is crosslinked into PP-PolyHb, it can reversibly carry oxygen with a lower affinity (P ₅₀=16 torr) than nonpyridoxylated PolyHb (P ₅₀=11 torr). These favorable physicochemical properties of PP-PolyHb suggest that further progress toward a potential artificial blood substitute has been made.     

The use of redox reactions in the analysis of dyes and dye intermediates: XVII. The influence of proton donors on direct current polarographic behavior of some water-insoluble azo pigments in acetonitrile

The influence of water and perchloric acid on the polarographic behavior of some water-insoluble azo pigments in acetonitrile has been investigated. The conditions were defined for the polarographic determination of the test substances in a mixed acetonitrile-water medium. The presence of strong acids prevents analytical use of these reactions.     

The polarographic behaviour of some elements in concentrated calcium chloride solution: The determination of chromium in the presence of nickel

Further studies on the polarography of trivalent chromium in concentrated calcium chloride solution are described. Details are given of a chloride-hydroxylamine base electrolyte (7.4M with respect to chloride) in which chromium may be determined directly in the presence of nickel. This method is not applicable if the nickel-chromium ratio is large. Results are presented and certain theoretical aspects are discussed.     

The influence of aminobenzoic acid on Zn(II) electroreduction on a mercury electrode in water-methanol

Summary The influence of the isomers of aminobenzoic acid on the reaction Zn(II)/Zn(Hg) was studied in water-methanol mixtures. Theo- andm-isomers accelerate this reaction in all investigated solutions. The standard rate constants are similar at the same degree of electrode coverage with these isomers in water and mixed solutions.p-Aminobenzoic acid inhibits the process of Zn(II)/Zn(Hg) electroreduction. The results suggest that the decisive role in the acceleration is played by the formation of the active complex inside the adsorption layer.

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Der Einfluß von Aminobenzoesäure auf die Elektroreduktion von Zn(II) an einer Quecksilberelektrode in Methanol-Wasser

Zusammenfassung Der Einfluß der verschiedenen Isomeren von Aminobenzoesäure auf die Reduktion von Zn(II) an einer Quecksilberelektrode wurde in Methanol-Wasser-Mischungen untersucht. Dieo- undm-Isomeren beschleunigen die Reaktion, und die Reaktionsgeschwindigkeiten sind in Wasser und in Methanol-Wasser gleich. Die Beschleunigung wird wahrscheinlich durch Bildung des aktivierten Komplexes innerhalb der Adsorptionsschicht verursacht.p-Aminobenzoesäure hemmt die Elektroreduktion.

     

The polarographic behaviour of some elements in concentrated calcium chloride solution : The development of a method for the determination of metallic impurities in calcium metal

The results of investigations discussed in this and previous papers are employed to develop a polarographic method for the determination of copper, chromium, lead, cadmium and manganese in calcium metal. Full details of the method are given and results and conclusions are presented.     

极谱法研究金属配合物时滴汞电极表面配位剂平衡浓度的一般表达式

在金属配合物的极谱研究中,往往需要知道配位剂 X~b-在汞滴表面的平衡浓度[X]_o.作者曾用扩散电流理论,在配位剂 X(b-)与 H~ 不配合时,导出了一个金属离子各级单核配合物在汞滴表面还原为汞齐时的[X]_0表达式.最近,作者又得到了一个普适性更好的[X]_0表达式.它不仅能把文献中更多的[X]_0表达式在同一理论基础上统一起来,而且还可在新的条件下得到一系列新的[X]_0表达式.表达式的推导设在所讨论的缓冲溶液中,加有高价金属离子 M~(n )(M),低价金属离子 M~((n-a) )(M′),配位剂 X~(b-)(X)和足量的支持电解质.在溶液本体中和汞滴表面上,X~(b-)分别与 M~(n )、M~((n-a) )、氢离     

Adsorption of N-Decyl-N,N,N-trimethylammonium triflate (DeTATf), a cationic surfactant, on the Au(111) electrode surface

The adsorption behavior of the cationic surfactant N-decyl-N,N,N-trimethylammonium triflate (DeTATf) on the Au(111) electrode surface was characterized using cyclic voltammetry, differential capacity, and chronocoulometry. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DeTATf has a multistate character. At low bulk DeTATf concentrations, the adsorption state is consistent with the formation of an adsorbed film of nearly flat molecules. At higher concentrations this film may represent a three-dimensional aggregated state. At negative potentials and charge densities close to 0 microC cm-2, the data suggest the formation of a film of tilted molecules oriented with the hydrocarbon tail toward the metal surface and the polar head toward the solution. A surprising result of this study is that DeTATf displays adsorption characteristics of a zwitterionic rather than a cationic surfactant. This behavior indicates that the adsorbed species is an ion pair.     

Solute-solvent interactions in surfactant adsorption: Part I. The influence of the polar head

This study deals with the variation of the interfacial tension of mercury aqueous solutions with potential and concentrations for solutions of butanol. butyric acid, butyramide and butyl monoether glycol. The results obtained have been analysed using an isotherm proposed by Bennes leading to values for the energy of adsorption corrected for the influence of the solute-solvent interactions in solution.A correlation has been revealed been to exist between the corrected energy of adsorption, the hydrophobicity coefficient and the dipole moment of the molecule which are all parameters related to the nature of the hydrophilic grouping.These result serve to show how the adsorption on mercury can be used to approach the problem of interactions between molecules in surfactant solutions.