Dosage de l'oxygene dans l'uranium et ses composes par la methode au monochlorure de soufre

A sulfur monochloride method is proposed for the determination of oxygen in uranium compounds. Sulfur monochloride reacts with oxygenated compounds at temperatures depending upon their nature; the sulfur dioxide produced is titrated by iodometry, after the excess reagent has been eliminated by a selective adsorption-desorption process using activated charcoal. This method has been successfully applied to uranium oxides (UO₂, U₃O₈), to mixtures of uranium dioxide with uranium, uranium nitride, and uranium carbide, and to substituted carbides (UC_1-xO_x). The results are generally satisfactory for oxygen contents higher than 500 p.p.m. However, in the presence of free or combined carbon, this limit is considerably higher. A loss of oxygen as carbon monoxide is also possible, and a simultaneous determination of carbon monoxide must be carried out. The relative error is of the order of a few per cent.     

Catalytic activity of manganese and copper oxides in the oxidation of sulfur compounds

Catalytic activity of manganese and copper oxides in the oxidation of sulfur compounds, including sodium sulfide, sodium hydrosulfide and ammonium sulfide was studied. Polymeric catalyst based on copper(II) and manganese(IV) oxides showed high activity, especially in the oxidation of sodium hydrosulfide and ammonium sulfide. Kinetic investigation showed that all the reactions are first order with respect to oxygen concentration and zero—to the source concentration of sulfur compounds.     

Sulfur speciation in hard coal by means of a thermal decomposition method

A new method for the determination of organic and pyritic sulfur in hard coal is presented. The method is based on controlled thermal decomposition of coal sample in oxygen-free and oxygen atmospheres. The results for sulfur liberated in an argon atmosphere at temperatures up to 773 K were close to organic sulfur contents (Sorg), although owing to the definition of 'organic sulfur' the values were not directly comparable. Sorg contents are calculated from the difference between total sulfur content in coal and contents of this element in the form of sulfides, sulfates and pyrites. Sulfur contents, found in the second stage of analysis, were close to pyritic sulfur contents. The difference between total sulfur content and the sum of sulfur values obtained in stages I and II corresponded to sulfur contents in those samples which were neither decomposed nor oxidized at temperatures up to 1173 K. Although not comparable with such conventional concepts for industrial purposes these data are attractive due to the ease and rapidity of the new method for the control of sulfur streams in industrial processes.     

A novel combustion system for the microdetermination of nitrogen

A method for the determination of nitrogen by combustion in a fast flow of pure oxygen is described. The oxygen is produced electrolytically and the hydrogen produced simultaneously is used to reduce the excess oxygen and oxides of nitrogen. A short layer of copper oxide oxidizes the hydrogen which remains uncombined due to the oxygen consumption of the sample. This layer is swept out by the water vapor; thus, only minute amounts of carbon dioxide are used, reducing the consumption of potassium hydroxide. The small layer of copper oxide can easily be reoxidized with air or technical oxygen. A virtually unlimited excess of oxygen during the combustion makes this method especially useful for samples difficult to combust and for trace determinations.     

Automatic sample preparation of35S labelled organic compounds for liquid scintillation counting

An automatic sample preparation method for the determination of³⁵S in organic compounds by liquid scintillation counting is described. The sample is burned in a stream of oxygen and the combustion products are led onto a quartz wool column wetted with dilute hydrogen peroxide. Sulfur oxides are retained on the quartz wool as sulfuric acid, while the other acid producing combustion products are eliminated by evaporation. The residual sulfuric acid in rinsed with distilled water, the sulfuric acid solution obtained is added to a liquid scintillation cocktail and the radioactivity is measured with a liquid scintillation counter. The combustion-evaporation process runs automatically according to the operational program carried out by an electronic programmer.     

硫化铜精矿物相分析及氧化机理研究

在海轮运输及样品的制备过程中,进口硫化铜精矿氧化的现象普遍存在,使得货物的重量和铜品位发生变化,但该种现象的机理研究不多。针对硫化铜精矿的物相进行分析,并对硫化铜精矿的氧化机理进行研究。首先,利用显微镜、扫描电子显微镜、X射线荧光光谱(XRF)、X射线衍射(XRD)等方法对两个硫化铜精矿进行物相分析,并对其中的主要元素和含铜主要物相进行定量化学分析。再次,利用热重分析(TGA)研究这两个硫化铜精矿发生氧化反应的温度,结果表明在400℃时铜精矿样品重量开始增加,在约650℃重量达到顶峰,随后重量开始下降。最后,分别在400、650和900℃对两个铜精矿样品进行灼烧,并利用XRF和XRD方法进行测定,从而研究铜精矿的氧化机理,结果表明在400℃时,出现了铁的氧化物和铜的硫氧化物,说明黄铜矿和黄铁矿开始氧化,但还没有完全氧化,在650℃时,化合物中的氧含量继续增加,硫含量逐步减少,在900℃时,铜和铁的化合物只剩氧化物,硫已全部被氧化。结果表明,硫化铜精矿中的铜、铁等元素在温度和时间的作用下逐步氧化,硫氧化物的产生为中间态,氧化物的产生为最终态。实验解释了进口硫化铜精矿氧化的原理,有助于贸易双方减少分歧,有助于海关技术中心更规范地制备样品,降低数据误差。     

Simultaneous determination of35S and14C in double-labelled organic compounds by liquid scintillation counting

An isotope analytical method for the simultaneous determination of³⁵S and¹⁴C in double-labelled organic compounds by liquid scintillation counting is described. The sample is burned in a stream of oxygen. Sulfur oxides are converted to sulfuric acid and separated from other combustion products, including carbon-14 dioxide, on a heated quartz wool column previously wetted with hydrogen peroxide. Carbon dioxide is collected from the gas stream by an absorbent suitable for liquid scintillation counting. The residual sulfuric acid is rinsed off the column with water and the aqueous solution obtained is mixed with a liquid scintillation cocktail for radioactivity measurement. The final solutions ready for counting are obtained in less than fifteen minutes, quantitative collection recovery is achieved and no cross contamination occurs.     

Automatic microanalyzers: VII. Automatic analyzer for rapid microdetermination of sulfur

A commercially available analyzer for determination of sulfur (0.5–100%) in organic and some inorganic compounds is described. It involves combustion of the sample at high temperature (1050 °C) to form SO₂ and SO₃ in a vertical reactor. SO₃ is reduced to SO₂ and nitrogen oxides to N₂ on copper at 850–900 °C. At this temperature the chemical reactions of SO₂ and copper are minimized so that SO₂ is obtained quantitatively in this range.Use of a vertical reactor and an autosampler makes an easy and complete automation of the sulfur determination possible. With this automation, great improvements are noticed in accuracy and precision over manual methods. The average time for a single determination is about 8 min.     

A purge and trap technique to capture volatile compounds combined with comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectrometry to investigate the effect of sulfur‐fumigation on Radix Angelicae Dahuricae

Sulfur‐fumigation is known to reduce volatile compounds that are the main active components in herbs used in herbal medicine. We investigated changes in chemical composition between sun‐dried and sulfur‐fumigated Radix Angelicae Dahuricae using a purge and trap technique to capture volatile compounds, and two‐dimensional gas chromatography/time‐of‐flight mass spectrometry for identification. Using sun‐dried Radix Angelicae Dahuricae samples as a reference, the results showed that 73 volatile compounds, including 12 sulfide compounds, were found to be present only in sulfur‐fumigated samples. Furthermore, 32 volatile compounds that were found in sun‐dried Radix Angelicae Dahuricae samples disappeared after sulfur‐fumigation. The proposed method can be applied to accurately discriminate sulfur‐fumigated Radix Angelicae Dahuricae from different commercial sources. Copyright © 2014 John Wiley & Sons, Ltd.     

烟气中二氧化硫及三氧化硫测定方法的研究

本文采用过氧化氢-氯化钡-钍试剂法以及80%异丙醇-氯化钡-钍试剂法分别测定了烟气中的二氧化硫及三氧化硫质量浓度,并对该方法的灵敏度、准确度以及各种影响因素进行了研究分析.本方法简单、快速、准确、便于现场监测控制.     

硫中毒对Cu/γ-Al_2O_3催化含硫低浓度甲烷燃烧特性的影响

采用浸渍法制备了质量分数11.32%Cu/γ-Al2O3催化剂,采用固定床反应器,考察了SO2浓度(0~0.02%)对低浓度甲烷(体积分数,3%)催化燃烧特性的影响,通过反应前后催化剂的微观结构及化学成分检测,结合理论分析,探讨了催化反应的硫中毒原因。研究表明,SO2的通入导致了Cu/γ-Al2O3催化剂活性及稳定性的降低,在同一反应温度下,甲烷转化率随着SO2浓度的增加而下降。SEM、EDS、FT-IR、XRD表征结果表明,SO2会导致Cu/γ-Al2O3催化剂表面出现结块现象,催化剂表面有硫元素的累积,且以硫酸盐的形式存在,其主要成分为硫酸铜(CuSO4)。在富氧条件下,SO2分子及氧离子在Cu2+上吸附所形成的硫酸铜,附着在催化剂表面,形成一层坚硬的外壳,是产生硫中毒现象的根本原因。     

Determination of sulfur in steels by radiochemical neutron activation analysis with liquid scintillation counting

A method has been developed for the determination of low-level sulfur in steels by radiochemical neutron activation analysis. During sample irradiation, ³⁵S is produced by the ³⁴S(n,γ)³⁵S reaction. Irradiated steels are mixed with sulfur carrier and dissolved in HCl/HNO₃. Sulfur is reduced to H₂S by reaction with HI/H₃PO₂/HCl. The evolved H₂S is absorbed in dilute NaOH, which is mixed with scintillation cocktail for the measurement of ³⁵S by liquid scintillation counting. Sulfur carrier yield is determined by iodometric titration. Chlorine is also determined by RNAA in order to correct for ³⁵S produced via the ³⁵Cl(n,p)³⁵S reaction. Sulfur has been determined at mass fractions as low as ≈5 mg/kg in ultra-high-purity iron using this method.     

XPS and XAES analysis of copper,arsenic and sulfur chemical state in enargites

Enargite, a copper arsenic sulfide with the formula Cu₃AsS₄ is of environmental concern due to its potential to release toxic arsenic species. The oxidation and dissolution of enargite are governed by the composition and chemical state of the outermost surface layer. Qualitative and quantitative analysis of the enargite surface can be initially obtained on the basis of X‐ray photoelectron spectroscopy (XPS) binding energy and intensity data. However, a more precise determination of the chemical state of the principal elements of enargite (copper, arsenic and sulfur) in the altered surface layer and in the bulk of the mineral requires a combined analysis based on XPS photoelectron lines and the corresponding X‐ray excited Auger lines. On the basis of results obtained on natural and synthetic enargite samples and on standards of sulfides and oxides, the Auger parameter α′ of different compounds was calculated and the Wagner chemical state plots were drawn for arsenic, copper and sulfur. Arsenic in enargite is found to be in a chemical environment similar to that of arsenides or elemental arsenic, whereas copper in enargite is in a chemical state that corresponds to copper sulfide, Cu₂S, for all samples irrespective of surface treatment (natural or freshly cleaved). Only sulfur changed from a chemical state similar to that of copper or iron sulfide in freshly cleaved samples to another state in natural enargite in the as‐received state. Thus, it is the sulfur atom at the surface of enargite that is most susceptible to changes in the enargite surface state and composition. A more detailed interpretation of this behavior, based on differences in the initial and final state effects, is proposed here. The concept of Auger parameter and chemical state plot, used here for the first time for investigating enargite, has proved to be a method to unambiguously assign the chemical state of the principal elements copper, arsenic and sulfur in these minerals. Copyright © 2006 John Wiley & Sons, Ltd.     

Neutron activation determination of oxygen in ceramic materials on the basis of yttrium,barium and copper

A procedure of determining oxygen in superconducting materials on the basis of yttrium, barium and copper oxides with the application of 14 MeV-neutron activation has been developed. The method is based on determining the relation between oxygen and yttrium in the compounds investigated. Quantitative evaluation of this relation is performed with the aid of a comparator and two-component monitor. In order to minimize systematic errors, expressions accounting for spectrometer dead time under conditions of varying component activity are proposed. The procedure ensures determination of the relation between oxygen and yttrium with a relative error of 0.4%(10 parallel measurements) with NAA using a neutron generator with a neutron yield of (1–3)·10¹⁰ n·s^–1.     

Rapid,automatic, high-precision method for micro,ultramicro, and trace determinations of sulfur

Samples are burned in a Carlo Erba 1106 elemental analyzer over copper oxide with oxygen, injected into the carrier gas. Combustion gases are reduced with copper. Water is absorbed, and sulfur dioxide is separated from carbon dioxide and nitrogen in a very short column of Porapak QS. Sample size is upt ot 0.7 mg, one determination takes 5 min, and the sampler takes up to 196 samples. It can be continuously loaded, and the instrument can be left to work automatically overnight. For the micro determination, helium is the carrier gas, and sulfur dioxide is measured with a thermal conductivity detector. The standard deviation of 18 analyses of pure organic compounds was 0.0446% S. The detection limit is 0.5 μg S, or about 0.1% S in a normal 0.5-mg sample. For ultramicro and trace determination, nitrogen is the carrier gas, and the measurement is made with an electron capture detector. The detection limit is 0.002 μg S, or about 0.0004% (4 mg kg^?1 S) in a normal 0.5-mg sample.     

Direct determination of cadmium in biological material using electrothermal atomization atomic absorption spectrometry with a metal tube atomizer and a matrix modifier

A direct determination of cadmium by electrothermal atomization atomic absorption spectrometry with a molybdenum tube atomizer has been investigated. Direct calibration method with cadmium standard solutions and ultrasonic agitation method of a solution including sample powder were used. Sulfur served as a matrix modifier for removal of interferences. Though this direct analytical method for cadmium determination in biological materials had a relatively large standard deviation, the accuracy was similar or superior to those of a sample digestion method and the direct analysis without sulfur. The advantages of this method are its simplicity, low cost, high speed of analysis, and rapid calibration.     

Determination of phosphorus,sulfur and chlorine in high-purity aluminium

Multi-step procedures for the determination of phosphorus, sulfur and chlorine are described and tested against established methods and on reference materials. Phosphorus is separated as hydrogen phosphide, extracted as phosphomolybdic acid, reduced to molydenum blue and measured photometrically (detection limit 0.05 g/g). Sulfur is separated after reduction as hydrogen sulfide or by means of pyrohydrolysis and measured by ICP-OES (detection limit 0.1 g/g). Chloride can be measured by ion chromatography after pyrohydrolytic separation (detection limit 0.1 g/g). The determination of sulfur was also successfully tested on copper and steel samples.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

锂硫电池正极用硫/介孔碳复合材料的制备及电化学性能

制备了以十二烷基硫酸钠(SDS)为模板的介孔碳,并将介孔碳和单质硫采用熔融渗透法复合制得硫/介孔碳复合材料。SEM、TEM和BET结果显示介孔碳成直径约为500 nm的大小均一的球体,存在孔径为2 nm的微孔;单质硫充分填充在介孔碳的微孔中。以硫/介孔碳复合物作为锂硫电池正极材料时显示出高的电化学性能。初始放电容量高达1519 mAh·g^-1,在200 mA·g^-1的电流密度下充放电200个循环后依然能保持在835 mAh·g^-1。硫/介孔碳复合材料的高倍率性能和优异的循环稳定性,源于介孔碳良好的导电性及其孔结构的固硫作用。     

Coupling needle‐trap devices with comprehensive two‐dimensional gas chromatography with high‐resolution time‐of‐flight mass spectrometry to rapidly reveal the chemical transformation of volatile components from sulfur‐fumigated ginseng

Sulfur‐fumigation could alter the quality of white ginseng by damaging the bioactive compounds and generating sulfur‐containing materials. In the present study, coupling needle‐trap devices with comprehensive two‐dimensional gas chromatography and high‐resolution time‐of‐flight mass spectrometry was applied to rapidly reveal chemical transformation of volatile components from sulfur‐fumigated ginseng. Thirty‐two volatile compounds were not in white ginseng samples after sulfur‐fumigation. Furthermore, 20 sulfur‐containing compounds were identified for the first time in volatile oil of sulfur‐fumigated white ginseng. The established approach could be applied to discriminate sulfur‐fumigated white ginseng among commercial samples and to control the quality of white ginseng.     

Contribution a l’etude du dosage par radioactivation du soufre et du phosphore en tres faibles concentrations dans les metaux de tres haute purete (Aluminium,magnesium, cuivre,fer, nickel)

The analytical procedure for the determination of sulfur in copper by activation with thermal neutrons is given. The purifications necessary to obtain a radiochemically pure precipitate of baryum sulphate are described. The occurrence of some discrepant values in the determinations led to the observation, for the first time, of abnormally high contents of³⁵S^* at a relatively important depth in the samples of irradiated copper (as deep as about 300 μ). Therefore it is necessary to etch the samples to a depth of 300 μ at least on each surface, before doing the chemical separations. Owing to the great influence of the reaction³⁵Cl(n,p)³⁵S^*, the determination of sulfur by thermal neutrons is only possible at contents higher than 10⁻⁶, even if the chlorine concentration is very low (2·10⁻⁸ Cl introduces a correction in terms of sulfur of the order of 10⁻⁶). For sulfur contents lower than 10⁻⁶, the determination is made by irradiation in fast neutrons. The analytical procedure is described and the corrections in the presence of phosphorus and chlorine are discussed. At contents of the order of 10⁻⁸, the corrections are very small and the determination of some 10⁻⁷ of sulfur is easy. Finally, the determination of phosphorus in copper by activation in thermal neutrons is given. The chemical separations are the same as in the preceding case. Contents of the order of 10⁻⁸ phosphorus are determined without difficulty. The results of the determination of sulfur and phosphorus in many samples of copper are indicated: OFHC copper, High Purity copper (99.999%) and different samples of zone refined copper prepared at the Vitry’s Laboratory.