Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

A Calixarene-Based Fluorogenic Reagent for Selective Mercury(II) Recognition

The first calixarene-based fluorogenic Hg(II)-selective extractant, 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,27-bis(N-(5-dimethylaminonaphthalene-1-sulfonyl)carbamoylmethoxy)-26,28-dimethoxycalix[4]arene (2), is reported. In solvent extraction from aqueous acidic solutions (HNO(3)), 2 exhibits excellent selectivity for Hg(II) over a wide range of transition, alkali, and alkaline earth metal cations. Quenching of its fluorescence due to Hg(II) coordination is unaffected by the presence of 100-fold excesses of alkali metal cations, alkaline earth metal cations, Ag(I), Tl(I), Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Pd(II), Zn(II), or Fe(III).     

用密度泛函理论研究汞在CeO_2(111)表面的吸附

采用密度泛函理论计算了Hg、HgCl、HgCl_2在CeO_2(111)表面的吸附构型、吸附能和态密度。结果表明,Hg在CeO_2(111)表面属于弱化学吸附。HgCl与CeO_2(111)表面为强化学吸附,是反应的重要中间体。HgCl_2在CeO_2(111)表面是物理吸附,易发生解离,脱除。氯对于汞的吸附和氧化产生较强的影响,这与实验结果相一致。基于计算结果,得到汞在CeO_2(111)表面的反应机理。     

Preconcentration and Voltammetric Determination of Mercury(II) at a Chemically Modified Glassy Carbon Electrode

In this work, the organic compound 2-mercaptobenzimidazole was covalently bound on the surface of a glassy carbon rod, via silanization, yielding a material capable of selectively complexing Hg(2+) ions. This material was applied as an electrode for voltammetric determination of mercury(II) following its nonelectrolytic preconcentration. After exchanging the medium, the voltammetric measurements were carried out by anodic stripping in the differential pulse mode (pulse amplitude, 50 mV; scan rate, 1.25 mV s(-)(1)) using 10(-)(2) mol L(-)(1) NaSCN solution as supporting electrolyte. An anodic stripping peak was obtained at 0.06 V (vs SCE) by scanning the potential from -0.3 to +0.3 V. After a 5 min preconcentration period in a pH 4.0 Hg(2+) solution, this electrode shows increasing voltammetric response in the range 0.1-2.2 μg mL(-)(1), with a relative standard deviation of 5% and a practical detection limit of 0.1 μg mL(-)(1) (5.0 × 10(-)(7) mol dm(-)(3)). Compared with the conventional stripping approach, this chemically modified glassy carbon electrode procedure presented good discrimination against interference from Cu(II) in up to 10-fold molar excess.     

二等标准水银温度计检定规程的修订及不确定度评定

论述了二等标准水银温度计检定规程修订的内容及检定结果的不确定度评价。     

Mercury chalcogenides under pressure

The mercury chalcogenides, HgTe and Hg_1?x Cd _x Te, have received considerable attention in recent years because of their use in infrared photon detectors. This article is concerned with some recent experiments on the Γ₆-Γ₈ band crossover in these systems induced by pressure. It is shown that although the inverted band model is valid for HgTe, the conclusions of the earlier workers on the pressure induced Γ₆-Γ₈ crossover are erroneous. Experimental results show that it is difficult to observe the band crossover due to an intervening structural phase transition from cubic zinc blend to the cinnabar structure. However pressure experiments on the semiconductor alloy system Hg_0·9Cd_0·1 Te clearly indicate this crossover. New results on the zinc blend-cinnabar phase transformation are also presented. The striking behaviour of thermoelectric power in the high pressure cinnabar phase is correlated with the available experimental data on the structurally similar elemental semiconductors like selenium and tellurium.     

Apparent Formation of an Oxidant by Electrochemical Reduction in the Mercury(0,I,II) Chloride System

The paradoxical appearance of a cathodic reaction sometimes observed in anodic stripping voltammetry and stripping potentiometry when using mercury film electrodes in chloride media containing mercury(II) has been investigated by systematically varying relevant chemical and electrochemical parameters and comparing the results with thermodynamic equilibrium calculations. Microscopic observations of morphological changes on the electrode surface caused by potential variations were made possible by using a novel electrode design. Three conditions have to be fulfilled for the cathodic reaction to occur: (a) formation of calomel by reaction between elemental mercury on the electrode surface and mercury(II) in solution, (b) subsequent reduction of mercury(II) to elemental mercury on the calomelized electrode surface, and (c) a chloride concentration in the range 0.001-3.5 M. Different ways of avoiding the interference from the cathodic reaction in stripping voltammetry and stripping potentiometry are experimentally demonstrated, and a mechanism for the appearance of the cathodic reaction is proposed.     

汞三相点的研究

叙述了汞三相点密封容器的设计和制作程序，并介绍了具体的复现装置和实验方法。实验结果表明，复现性为±０．１ｍＫ，平均熔化温度与平均凝固温度的差为０．１ｍＫ，不同密封容器间的差小于０．２ｍＫ。