Mechanism and analytical aspects of the polarographic maximum wave of tellurium

The polarogram of tellurium(IV) in weakly basic solution has a sharp maximum on the diffusion current plateau. The electrode process causing this maximum has been examined by means of various techniques such as semiconductor catalysis, "block" polarography and ultraviolet irradiation of the dropping mercury electrode. The maximum was found to be caused by the catalytic wave of hydrogen produced by the tellurium deposited on the mercury surface. Part of the tellurium is reduced to hydrogen telluride by nascent hydrogen formed catalytically. The brown mist which usually appears in the vicinity of the surface of the dropping mercury cathode consists of elemental tellurium produced by the decomposition of the hydrogen telluride near the electrode. The sudden decrease in the current maximum at a potential more negative than the peak potential of the maximum is due to desorption of tellurium, caused by movement of mercury.     

Determination of Tellurium by Gas Phase Molecular Absorption Spectrometry After Hydrogen Telluride Generation

Abstract

A method for determination of tellurium(IV) or tellurium(VI) is described that involves hydrogen telluride generation by reduction with sodium tetrahydro-borate(III), evolution of hydride with HCl solution, transport into a flow-cell placed in a UV-visible molecular absorption spectrophotometer and measurement of gas at 190 nm. Hydride generation and determination procedures are optimized, based on height and area of absorbance versus time profile of hydrogen telluride generated. Using the best experimental conditions found the calibration curve is linear from 5 to 100 μg/ml of tellurium, 1.1 μg/ml of tellurium(IV) or 3.1 μg/ml of tellurium(VI) can be detected, and relative standard deviation ranges from 4 to 7%. The method is applied to the analysis of additives for synthetic rubber making.     

Molecular emission cavity analysis: Part 22. Determination of selenium and tellurium by direct injection into the cavity

Selenium (>50 ng) as selenite or selenate, and tellurium (1–15 μg) as tellurate may be determined by measuring the intensities of the Se₂ and Te₂, emissions, in a carbon cavity situated in a hydrogen—air flame. Certain organic compounds (e.g., citric acid, ascorbic acid and glucose) enhance the intensities, especially of tellurium.     

Molecular emission cavity analysis: Part 14. Determination of Selenium Utilizing Hydrogen Selenide Generation

Selenium (0.02–2 ppm), after conversion to hydrogen selenide -with sodium tetrahydroborate, can be determined by molecular emission cavity analysis. The detection limit is 7 ng of selenium. The effects of 26 ions are reported. The depressive effects of arsenic and antimony can be removed by selective volatilisation, and the enhancing effects of tellurium and sulphite by addition of tellurium to standards and by oxidation to sulphate, respectively.     

Reaction of 1,1-dichloroethane with tellurium in the system hydrazine hydrate-potassium hydroxide

The reaction of 1,1-dichloroethane with tellurium in the system hydrazine hydrate-potassium hydroxide gave ethyltellanyl derivatives as a result of replacement of one chlorine atom in the substrate by tellurium, and of the other, by hydrogen. Probable mechanisms of reduction of the C-Cl bond and mass spectra of the products were considered. The mass spectra of ditelluroacetals revealed unusual rearrangement of the molecular ion, leading to the formation of Te-Te and new C-C bond.     

Determination of trace impurities in zircaloy-2 and tellurium by spark source mass spectrometry

Determination of trace impurities in zircaloy-2 and tellurium by Spark Source Mass Spectrometry (SSMS) is reported. The advantage of SSMS lies in the fact that along with metallic trace constituents even the nonmetallic impurities and gases including hydrogen can also be determined.     

The reaction of hydrogen chloride with bis (p-ethoxyphenyl)telluride,a possible route to pure tellurium

The reaction of hydrogen chloride with bis(p-ethoxyphenyl)telluride is investigated and shown to give essentially phenetole (C₆H₅COEt), tellurium, and bis(p-ethoxyphenyl)tellurium dichloride. Spectroscopic methods (UV–visible, ¹²⁵Te NMR) show that some bis(p-ethoxyphenyl)ditelluride is produced. This is believed to arise from a side reaction of organic telluride with an intermediate organyltellurenyl chloride which is considered to arise from initial proton attack at the Te–C bond of the telluride. The ditelluride reacts with HCl to deposit 80% of its tellurium content as the element; phenetole is the other major product. Use of a spin-trap reagent gave no evidence of radical intermediates. An attempt to develop a reaction sequence to prepare high-purity tellurium is described. Although a purity of 99.985% could be achieved, overall yields are not economic, unless very highpurity tellurium is required. The method described is, however, very effective for the removal of traces of tin, lead, arsenic and antimony and can significantly reduce the copper, iron and selenium content; for example, one treatment of an alloy (Te, 75%; Se, 25%) gave a sample of tellurium containing 40 ppm selenium.     

Influence of volatile hydride-forming elements on antimony determination by atomic-absorption spectrometry with hydride-generation

A study was undertaken to determine the interfering effects of arsenic, bismuth, germanium, lead, selenium, tin and tellurium on trace determination of antimony by atomic-absorption spectrometry with hydride-generation. A 1% NaBH(4) solution was used as reductant and a small amount of oxygen was added to the hydrogen produced, to support the combustion and atomization of SbH(3). The interference from selenium in the determination of antimony is removed if potassium iodide-ascorbic acid solution or copper sulphate is added to the sample solution. The interference of tin and tellurium can also be avoided by adding potassium iodide-ascorbic acid solution. A possible interference mechanism is discussed.     

Synthese et caracterisation de fluorotellurates IV alcalins et d'ammonium partie I. Etude du pentafluorotellurate IV de lithium LiTeF5

Lithium pentafluorotellurate (IV) LiTeF₅ has been prepared by different methods:

• •slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride,
• •heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF₅ is orthorhombic

(a = 9,52 Å b = 9,12 Å c = 11, 60 Å)     

选择脱卤还原反应的研究

Ramasamy、Osuka等用NaHTe/EtOH研究了二卤代物的脱邻二溴、偕二溴反应和α-溴代羰基化合物的脱卤还原反应,我们选择结构不同的卤代物以NaHTe还原,发现在水介质和催化量碲代替计算量碲时也能顺利地进行这类反应,其反应条件温和,产率高,是有机官能团转化的好方法。     

A New Polarographic Adsorptive Catalytic Wave for the Determination of Trace Tellurium in Smog Dust and Wheat Flour

Linear-sweep polarography of tellurium in sulfuric acid solution containing methylene blue produces a wave at −0.82 V (vs SCE). In a cathodic sweep, the derivative peak current is directly proportional to the concentration of tellurium over the range 4 × 10⁻⁹to 1 × 10⁻⁷g/ml, and the detection limit is 2 × 10⁻⁹g/ml. The polarographic wave is an adsorptive catalytic hydrogen wave. This method has been applied to the determination of trace amounts of tellurium in smog dust and wheat flour, with satisfactory results.     

Selective reduction of imonium salts by sodium hydrogen telluride

Sodium hydrogen telluride reduces imonium salts effeciently at room temperature in ethanol. The products of the reaction depend upon the pH. Under alkaline pH only dihydro-derivatives are formed. Under acid pH (6-7) the products depend on the structure of the salt. The tellurium con be recovered quantitatively.     

Über Chalkogenidhalogenide des Kupfers

Nine ternary chalcogenidehalides of copper could be synthesized under hydrothermal conditions from the resp. hydrogen halide solutions. They belong to the pseudobinary systems, formed between selenium and tellurium and the resp. Cu^I halide. In the selenium systems exist: CuISe₃, rhombohedral; CuBrSe₃, orthorhombic, and CuClSe₂, monoclinic. Two homologous series of tellurium compounds exist: CuXTe, tetragonal, and CuXTe₂, monoclinic (X ? Cl, Br, I). Thermodynamic data could be obtained for the selenium compounds using the Knudsen effusion method. The samples exhibit a temperature independant diamagnetism. All compounds can also be synthesized by reaction of stoichiometric amounts of Cu^I halide and selenium (300°C) or tellurium (350°C). The corresponding thiohalides could not be observed.     

Atomic absorption spectrometry of tellurium with electrothermal atomization in a molybdenum microtube

Hydrogen, added to argon purge gas, is necessary to protect the molybdenum microtube atomizer from oxidation, but it increases the atomization temperature and decreases the maximum absorbance of tellurium. A mixture of thiourea and copper removes the interfering effects of diverse elements and counteracts the effect of hydrogen. Tellurium (20–200 ppm) in copper can be determined after extraction as a chloride complex.     

微波消解–石墨炉原子吸收光谱法测定空气中碲

建立微波消解–石墨炉原子吸收光谱法测定空气中的碲。采用微孔滤膜收集样品,以硝酸–双氧水混合体系微波消解滤膜,氯化钯为基体改进剂,在优化的仪器工作条件下测定。碲的质量浓度在0~15μg/L范围内与吸光度线性关系良好,相关系数为0.999 5,方法检出限为0.14μg/L。样品加标回收率在95.6%~104.0%之间,测定结果的相对标准偏差为1.15~1.37%(n=7)。该方法操作简单、灵敏度高,适用于空气中微量碲的测定。     

A rapid procedure for the determination of the tellurium content of organotellurium compounds

A rapid micro-analytical procedure for the analysis of tellurium in organotellurium compounds is described. The compounds are decomposed using the conventional oxygen flask method followed by treatment with aqueous hydrogen peroxide/hydrochloric acid solution. The tellurium content of the resulting solution is determined by atomic absorption spectrophotometry. If the analyses are carried out batch wise i.e. 6–8 samples with each standardisation of the instrument, the total analysis time is about $\text{1}\text{2}$ hour per sample.     

Investigation of the primary processes occurring at the tin/semiconducting layer/electrolyte interfaces by rapid pulse technique: Part II. Studies of the Sn/Te/electrolyte system

Tellurium layers are cathodically deposited on the surface of tin substrate from a sodium tellurite bath of pH 9.67. The electrode is anodically polarized using rapid galvanostatic rectangular pulses. Apparent specific resistance values calculated from resistance overpotentials demonstrate the semiconducting nature of the tellurium layers. The observed resistance, being too high compared to the reported values for Te crystals suggests the presence of amorphous Te in the electrodeposited phase, as well as the persistence of adsorbed hydrogen cathodically formed. Activation overpotentials are interpreted in view of the primary processes probably operating at the electrode/solution interface. These are associated with the corrosion of tellurium, or occasionally tin in its pores.     

Aromatic derivatives and tellurium analogues of cyclic seleninate esters and spirodioxyselenuranes that act as glutathione peroxidase mimetics

[Reaction: see text]. Several novel organoselenium and tellurium compounds were prepared and evaluated as mimetics of the selenoenzyme glutathione peroxidase, which protects cells from oxidative stress by reducing harmful peroxides with the thiol glutathione. The compounds were tested for catalytic activity in a model system wherein tert-butyl hydroperoxide or hydrogen peroxide were reduced with benzyl thiol and the rate of the reaction was measured by monitoring the formation of dibenzyl disulfide. Thus, aromatic derivatives 19, 22, 24, and 25 proved to be inferior catalysts compared to the parent cyclic seleninate ester 14 and spirodioxyselenurane 16. In the case of 19 and 22, this was the result of their rapid conversion to the relatively inert selenenyl sulfides 31 and 32, respectively. In general, hydrogen peroxide was reduced faster than tert-butyl hydroperoxide in the presence of the selenium-based catalysts. The cyclic tellurinate ester 27 and spirodioxytellurane 29 proved to be superior catalysts to their selenium analogues 14 and 16, respectively, resulting in the fastest reaction rates by far of all of the compounds we have investigated to date. Oxidation of 29 with hydrogen peroxide produced the unusual and unexpected peroxide 33, in which two hypervalent octahedral tellurium moieties are joined by ether and peroxide bridges. The structure of 33 was confirmed by X-ray crystallography. Although 33 displayed strong catalytic activity when tested independently in the model system, its relatively slow formation from the oxidation of 29 rules out its intermediacy in the catalytic cycle of 29.     

电感耦合等离子体发射光谱法测定粗二氧化碲中 铜、铅、锑、铋、砷和硒

粗二氧化碲作为碲精炼或碲化工产品生产的重要原料,其中共存元素铜、铅、砷、锑、铋、硒含量的准确测定对于生产过程质量控制和贸易结算具有重要意义,但目前没有粗二氧化碲中铜、铅、砷、锑、铋、硒含量检测的标准分析方法。采用王水和饱和氟化氢铵分解试样,在王水和酒石酸介质中,选用Cu 327.393 nm、Pb 220.353 nm、Sb 217.582 nm、Bi 223.061 nm、As 193.696 nm、Se 196.026 nm为分析谱线,采用电感耦合等离子体发射光谱(ICP-AES)法测定粗二氧化碲中铜、铅、锑、铋、砷和硒含量。各元素校准曲线的相关系数均大于0.999;铜、铅、锑、铋、砷和硒的检出限分别为0.0004%、0.0005%、0.0006%、0.0007%、0.0004%和0.0007%,定量检出限分别为0.0012%、0.0016%、0.0020%、0.0025%、0.0013%和0.0025%。按照实验方法测定5个粗二氧化碲样品中铜、铅、锑、铋、砷和硒,测定结果的相对标准偏差(RSD,n=7)为0.79%~4.8%,加标回收率为96.0%~103%。方法简单,精密度和准确度较高,可用于测定粗二氧化碲中铜、铅、砷、锑、铋、硒含量。     

碲的极谱催化波研究进展

碲是一种有毒和致畸元素,也是重要的材料元素,碲的一种重要分析方法就是极谱催化波,碲的极谱催化波包括平行催化波,催化氢波以及络合物吸附(催化)波。此文就近年来碲的极谱催化波的研究现状进行评述,引用文献42篇。