共查询到20条相似文献,搜索用时 31 毫秒
1.
The membrane electrode based on a synthetic chalcocite (Cu(2)S) single crystal responds primarily to the activity of copper(I) ions in solution. The experimental selectivity coefficient with respect to copper(II) ions is in good agreement with the value calculated on the basis of solubility products of both sulphides. The electrode has been calibrated with metal-ion buffers containing a strongly complexing ligand. TETREN, and can be used as an indicator in titrations of copper with EDTA and TETREN. Comparison of an experimental titration curve with one calculated with the aid of the program HALTAFALL showed good agreement in the case of TETREN, but there were discrepancies for the EDTA titration, which are attributed to the presence and complexation of copper(I) ions. The electrode has also been applied in metal titrations with Cu(2+) as indicator ion, though the potential changes observed were smaller than predicted. All titrations showed errors less than 1%. 相似文献
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The behaviour of the dropping lead amalgam electrode has been studied. Calculated and experimental current-voltage curves have been compared and an explanation has been given for the observed differences. Selective determination of metal ions appears to be possible in the presence of saturated chloride, 1M bromide and 10(-2)M iodide by means of amperometric complex-formation titrations using normal pulse polarography with the dropping lead amalgam electrode. 相似文献
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A new PVC membrane electrode for cobalt(II) ions based on a recently synthesized Schiff base of 5-((4-nitrophenyl)azo)- N-(2',4'-dimethoxyphenyl)salicylaldimine is reported. The electrode exhibits a Nernstian response for Co(2+) ions over a wide concentration range (9.0 x 10(-7)-1.0 x 10(-2) M) with a slope of 29(+/-1). The limit of detection is 8.0 x 10(-7) M. The proposed sensor revealed good selectivities over a wide variety of other cations including hard and soft metals. This electrode could be used in a pH range of 3.5-6.0. It was used as an indicator electrode in potentiometric titrations of cobalt(II) ions and can be used in the direct determination of Co(2+) in aqueous solutions. 相似文献
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在不锈钢基上通过复合电沉积的方式制备了二氧化铅 碳化钨(PbO2-WC)电极。 考察了温度、电流、WC颗粒浓度对电极性能的影响;通过析氧曲线、Tafel曲线、扫描电子显微镜能谱、X射线衍射图谱考察了WC颗粒掺杂前后PbO2电极相关性能的变化。 结果表明,在最佳工艺即温度70 ℃、镀液中WC颗粒浓度为40 g/L时,电流密度为0.015~0.025 A/cm2;PbO2-WC共沉积过程中PbO2发生了择优生长,WC颗粒的加入能够细化PbO2晶粒,使镀层变得致密,相对于PbO2电极,PbO2-WC复合电极的耐腐蚀性上升,析氧过电位下降。 相似文献
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C Yu G Li X Guan J Zheng D Luo L Li 《Physical chemistry chemical physics : PCCP》2012,14(35):12368-12377
This work has initiated an investigation on the electrochemical behaviors and the structure changes of the composite electrode 0.3Li(2)MnO(3)·0.7LiMn(1/3)Ni(1/3)Co(1/3)O(2) when charged with different cut-off voltages. It is found that the charge cut-off voltages could not only affect the capacity property and coulombic efficiency, but also alter the electrode kinetics of the composite. As a consequence, the electrochemical activation of the composite electrode is highly dependent on the charge cut-off voltages: when the charge cut-off voltage is higher than 4.5 V, the inert component Li(2)MnO(3) in the composite electrode is completely activated. At the meanwhile, there occurred an irreversible oxygen loss during the initial charge process, which yielded a hollow sphere in the electrode. Regardless of charge voltages, Mn ions in the composite electrode were presented in an oxidation state of +4, while Co(2+) ions were detected at the surface of the electrode when cycled at low voltages. Ni ions in the composite could react with organic or inorganic species and then cover the surface of the cycled electrode. 相似文献
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Potentiometric titrations of metal ions with EDTA have been carried out with a platinum or graphite electrode and the Fe(III)/Fe(II) redox system. In the absence of oxygen and for pH < 2 the titration curves may be described by an equation similar to that given previously for titrations with silver and mercury electrodes. Titration curves for bismuth and indium, which are more strongly complexed than iron, are asymmetrical and useful for analytical purposes. When the titrated ions are complexed less strongly than iron(III) ions the kinetics of metal complexation have a pronounced effect. The titration curves of thorium and copper, which react more rapidly than iron, are analytically useful. The curves recorded rapidly after titrant additions have a better end-point break than those which correspond to thermodynamic equilibrium. When a metal, e.g., nickel, is weakly bound by EDTA, and reacts more slowly than iron, a very small end-point break or none at all is observed. 相似文献
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The behaviour of a new type of electrode, made from ceramic Ag(2)S, has been investigated. The electrode response is Nernstian for Ag(+) over the range 10(-6)-2M and for Hg(2+) in the concentration range 10(-6)-10(-2)M, both at constant ionic strength (0.1M). The electrode is Ag(+)-selective, with maximum interference from Hg(2+). It can be used for acid-base potentiometric titration and for potentiometric Ag(+) and Hg(2+) precipitation titrations. 相似文献
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The application of d.c. and square-wave polarographic measurements for the indication of the end-point in titrations with triethylenetetraminehexa-acetic acid (TTHA) has been studied. TTHA has ten co-ordinating groups and forms complexes with metal to ligand ratios of either 1:1 or 2:1, depending on the metal and experimental conditions. The shape of the titration curves, determined by the dependence of the limiting current (peak current of the square-wave polarographic curve) or of the half-wave potential (peak potential) on the amount of TTHA added indicates the composition of the complex formed in the titration. The composition of this complex as determined from the studied titration curves agrees with that predicted by theory. Titrations with polarographic indication of the end-point were also applied for direct titrations of binary mixtures of metal ions. The resulting titration curves indicated the existence of mixed dinuclear complexes and also the kinetic factors involved in the reactions between two different metal ions and TTHA. 相似文献
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Amperometric complex-formation titrations with a dropping bismuth amalgam electrode in halide medium
The use of the dropping bismuth amalgam electrode has been investigated for the selective determination of metal ions in the presence of large concentrations of halides by means of amperometric complex-formation titrations, using normal pulse polarography. Concentrations of metal ions down to 3 x 10(-7)M have been determined with adequate accuracy in the presence of about 0.1M chloride or 0.01M bromide. Calculated and experimental current-voltage curves have been compared and found to be in reasonable agreement. 相似文献
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The behaviour of the bright palladium electrode toward the redox systems Cr(2)O(7)(2-)/Fe(2+) and Ce(4+)/Fe(2+) (in potentiometric titration) has been investigated as a function of pretreatment of the electrode. Anodization of the electrode at potentials higher than 800 mV increases DeltaE at the equivalence point by 300-400 mV for the dichromate titration. The sharp change in potential is due to the reaction between PdO(2) and Fe(2+). The equivalence point corresponds to the beginning of the potential drop, rather than the inflexion point, especially for dilute solutions. If the electrode is ignited before use the surface oxide PdO is oxidized to PdO(2) by Cr(V), the potential increases during the titration and DeltaE is 200 mV bigger than when an untreated electrode is used. In the titration of Ce(4+) with Fe(2+) the DeltaE is largest with untreated electrodes, and if the anodized electrode is used, the titration curves clearly show the reaction between PdO(2) and Fe(2+). 相似文献
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添加剂对电沉积二氧化铅阳极性能的影响 总被引:4,自引:0,他引:4
本文研究了各种添加剂对电沉积二氧化铅阳极性能的影响,结果表明卤素离子和过渡金属离子对制备二氧化铅阳极的形貌和性能有很大影响,实验发现以氯离子和铁离子为添加剂制备的二氧化铅阳极用于电解析出臭氧时,其活性和稳定性明显改善。 相似文献
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不同电极材料和不同酸介质对3-甲基吡啶电氧化的影响 总被引:1,自引:0,他引:1
在以质子交换膜为隔膜的电解池内,通过3-甲基吡啶在PbO2/Ti、SnO2/Ti、石墨和MnO2/Ti电极上的电氧化研究发现,在硫酸溶液中,PbO2电极是催化活性最高的工作电极.通过3-甲基吡啶在硫酸、高氯酸、磷酸和乙酸介质中的电氧化研究发现,对于PbO2电极,硫酸是最适合的介质.利用循环伏安实验和恒电位电解实验,研究了电氧化条件和电催化活性,比较了各种条件下的电流效率和选择性. 相似文献
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The construction and basic characteristics of a new liquid-state Hg(2+)-selective membrane electrode are discussed. The membrane consists of the PAN chelate of Hg(II), dissolved in CHCl(3). The linear response range of the electrode is 10(-1) -10(-5)M Hg(2+) with a slope of 28.5 mV/decade of concentration. The response time of the electrode in dilute solutions is less than 3 min, and in concentrated solutions it is only a few sec. The electrode has been used in precipitation or complexation titrations in which Hg(2+) is involved (e.g., in the determination of some organic compounds in drug synthesis). 相似文献
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Rada S Dehelean A Culea M Culea E 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(2):320-324
FTIR, UV-VIS and EPR spectra of manganese doped lead-tellurate glasses with composition xMnO·(100-x)[4TeO2·PbO2] where x=0, 1, 5, 10, 20, 30, 40mol% have been studied. The FTIR spectra show the formation of the Mn-O-Pb and Mn-O-Te bridging bonds by increasing of MnO concentration. The UV-VIS spectra show the Mn(+3) species exhibit pronounced absorption, which masks the Mn(+2) spin-forbidden absorption bands when Mn(+2) ions are in high concentrations in these glasses. The EPR spectra exhibit resonance signals characteristic of Mn(+2) ions. The resonance signal located at g≈2 is due to Mn(+2) ions in an environment close to octahedral symmetry, whereas the resonance at g≈4.3 and 3.3 are attributed to the rhombic surroundings of the Mn(+2) ions. The increase in the MnO content gives rise to absorption at g≈2.4 and the paramagnetic ions are involved in dinuclear manganese centers. 相似文献
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Titration curves were derived for potentiometric titrations with zero electric current, utilizing a membrane electrode as indicating electrode, the membrane consisting of permselective, ion-exchanging material. As a first example, calculations were made for simple precipitation titrations with only +1 or -1 charged ions present in the solution to be titrated and in the reagent. For the calculations of the membrane potentials the theory of TEORELL and MEYER and SIEVERS was used. The influence of several parameters, such as the diffusion coefficients of the ions, the capacity of the membrane and the concentration of the solutions, was examined. 相似文献
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Teixeira MF Ramos LA Fatibello-Filho O Cavalheiro ET 《Fresenius' Journal of Analytical Chemistry》2001,370(4):383-386
The construction and analytical evaluation of a PbO2-based graphite-epoxy electrode sensitive to H3O+, based on incorporation of lead(IV) oxide in a graphite-epoxy matrix, are described. The data obtained from a variety of acid-base titrations in aqueous and aqueous-ethanolic media were compared with those obtained by use of a glass electrode under the same conditions. The proposed electrode provides a linear response in the pH range from 1 to 11 with a slope of -58.7+/-0.3 mV pH(-1) and -60.8+/-0.2 mV pH(-1) in aqueous and ethanolic media, respectively. The response time was less than 15 s and the lifetime of the electrode was at least eight months (ca. 5000 determinations) and its performance is good in pH determination and end-point detection in potentiometric acid-base titrations in both aqueous and aqueous-ethanolic media. 相似文献
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The construction and basic characteristics of a liquid-state Hg(2+)-sensitive electrode are discussed. The membrane consists of the Hg(2+) chelate of diketohydrindylidene-diketohydrindamine (DYDA) in chloroform. The range of linear response of the electrode is 10(-1)-10(-5)M Hg(2+) with a slope of 31 mV/decade. The response time of the electrode is a few seconds in concentrated solutions. The electrode may be used with good results in potentiometric titrations involving Hg(2+). 相似文献
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The paper deals with the influence of anode material on the efficiency of degradation for organic pollutants in water system.The electrochemical performance of fluorine ion doped lead dioxide(F--PbO2) electrode for the degradation of aniline was compared with that of undoped lead dioxide(PbO2) electrode by ultraviolet-visible(UV-Vis) spectroscopy,linear voltammetry and other analytical methods,such as the measurement by chemical oxygen demand analyzer,high performance liquid chromatography and scanning electron micrography.It was shown that both PbO2 electrode and F--PbO2 electrode could make aniline be mineralized completely and have the same degradation course,but F--PbO2 electrode has much higher electrocatalytic activity than undoped PbO2 electrode for the electrochemical degradation of aniline.The experimental results confirm that F--PbO2 electrode has much higher potential for oxygen evolution than undoped PbO2 electrode. 相似文献