Studying the Link between the Potential of a Metal-Oxide Anode, the Current Efficiency for Chlorate, and the Current Losses for the Oxygen and Chlorine Evolution in a Wide Range of the Chlorate Electrolysis Conditions

Dependences of the current efficiency for chlorate and current losses for the oxygen evolution on the anode potential are studied. The study is performed in a cell without directed electrolyte circulation during the electrolysis of chloride–chlorate solutions of various compositions at the ORTA and ORTA-I1 anodes, at different current densities, temperatures, and solution pH. At identical temperatures, the dependences have extremums. The anode potentials corresponding to extremums coincide with critical potentials (found in a polarization study) for anodes covered with coatings containing ruthenium dioxide. The current efficiency for chlorate at ORTA-I1 is higher than that at ORTA, while the extremum region is less pronounced. The problem of how to substantially decrease the specific power consumption in the chlorate production by simultaneously increasing the anodic current density and the electrolysis temperature is considered.     

Kinetics of Oxygen Evolution on Dimensionally Stable Anodes during Chlorate Electrolysis

The kinetics of oxygen evolution on dimensionally stable anodes during chlorate electrolysis at markedly different concentrations of chloride and sodium chlorate is studied. The theoretical model developed for the process kinetics assumes that molecules of hypochlorous acid participate in the oxygen evolution. The process rate is characterized by first reaction order by active chlorine, provided molecules of hypochlorous acid can inhibit the process due to their reversible adsorption on the anode surface. Mathematical modeling methods are employed to demonstrate the model adequacy to experiment.     

Kinetics of the Sodium Chlorate Formation in Electrolysis of Chloride Solutions with Use of Dimensionally Stable Anodes

The kinetics of the formation of sodium chlorate during electrolysis of chloride solutions with use of dimensionally stable anodes is studied. An analysis and calculations suggest that the experimental results are well described by the proposed set of differential equations under the assumption that the homogeneous chemical reaction of chlorate formation has second, rather than third, order by active chlorine.     

饮用水中氯酸盐、亚氯酸盐的离子色谱测定方法

建立了饮用水中微量氯酸盐以及亚氯酸盐的离子色谱测定方法。结果表明,亚氯酸盐和氯酸盐在0～0.50 mg/L范围内线性良好,精密度高,亚氯酸盐r2=0.999 8,样品加标平均回收率91.5%～99.4%,相对标准偏差(RSD)0.64%～1.78%,检出限为3.98μg/L;氯酸盐r2=0.999 6,样品加标平均回收率94.7%～101.6%,相对标准偏差(RSD)0.94%～1.35%,检出限为4.65μg/L;方法操作简单、快速、准确、灵敏度高、干扰少,适用于饮水消毒副产物亚氯酸盐和氯酸盐的检测。     

Electroreduction of As(III) in Acid Environment

The main reduction products of aqueous sulfuric acid solutions of As(III) are arsine and elemental arsenic, whose yields are substantially dependent on the electrolysis conditions. At a current density of 500 A m^–2and an As(III) concentration of 0.25 M, the following current efficiencies (CE) for arsenic and arsine are obtained: Cd, 28.2 and 26.2; Pb, 29.3 and 22.9; Ti, 16.1 and 22.4; steel 3, 21.0 and 21.0; Cu, 20.3 and 19.9; and stainless steel, 24.9 and 16.9. For arsine, CE on a Pb cathode is virtually temperature-independent at 15–80°C. Multiple use of the same Pb cathode barely impacts its activity. The arsine CE considerably increases at 2500–3000 A m^–2and reaches 75–78% and 50–53% on Pb and Cd, respectively.     

Combustion of a Layered System Based on Sodium Chlorate

The velocity of combustion under atmospheric conditions in a constant-volume bomb of formulations based on sodium chlorate and polyethylene in the form of tubes (layered system) was subjected to a comparative study in relation to the type of additive, layer porosity, and fraction composition of sodium chlorate.     

氯酸钾二氧化锰实验室制氧法探原

Oxygen preparation by potassium chlorate and manganese dioxide is one of the most classical laboratory method. Few study has been made so far on its origination and establishment. Through checking the original roles of potassium chlorate and manganese dioxide, it is found that manganese dioxide was ever first selected as raw material for making oxygen, then led the discovery of chlorine by Scheele and potassium chlorate by Berthollet. Potassium chlorate itself was also ever used for oxygen preparation at a high temperature. In 1832, manganese dioxide was firstly mixed with potassium chlorate for oxygen by Döbereiner and reduces the temperature dramatically. With more following studies, the classic method of oxygen preparation via the two materials was finally established.     

Burning of Sodium Chlorate Based Formulations

The burning velocity of sodium chlorate based formulations with polyethylene and kerogen under atmospheric conditions was studied in relation to composition, i.e., oxygen excess factor.     

Chlorate ion mediated rutile to anatase reverse phase transformation in the TiO2 nanosystem

Rutile TiO(2) nanoneedles (8 nm × 100 nm) synthesized at room temperature by anodization in perchloric acid (pH < 1) are shown to undergo an interesting reverse phase transformation to anatase nanoparticles (8 nm) at 300 °C only if the chlorate ions are maintained in the ambient medium. When chlorate ions are removed by multiple washing, the rutile phase and the needle morphology are maintained. The mechanism of formation of the ion-stabilized solid and its thermal evolution is discussed.     

A gravity-independent single-phase electrode reservoir for capillary electrophoresis applications

Capillary electrophoresis (CE) holds great promise as an in situ analytical technique for a variety of applications. However, typical instrumentation operates with open reservoirs (e.g., vials) to accommodate reagents and samples, which is problematic for automated instruments designed for space or underwater applications that may be operated in various orientations. Microgravity conditions add an additional challenge due to the unpredictable position of the headspace (air layer above the liquid) in any two-phase reservoir. One potential solution for these applications is to use a headspace-free, flow-through reservoir design that is sealed and connected to the necessary reagents and samples. Here, we demonstrate a flow-through high-voltage (HV) reservoir for CE that is compatible with automated in situ exploration needs, and which can be electrically isolated from its source fluidics (in order to prevent unwanted leakage current). We also demonstrate how the overall system can be rationally designed based on the operational parameters for CE to prevent electrolysis products generated at the electrode from entering the capillary and interfering with the CE separation. A reservoir was demonstrated with a 19 mm long, 1.8 mm inner diameter channel connecting the separation capillary and the HV electrode. Tests of these reservoirs integrated into a CE system show reproducible CE system operation with a variety of background electrolytes at voltages up to 25 kV. Rotation of the reservoirs, and the system, showed that their performance was independent of the direction of the gravity vector.     

低浓度NaCl溶液Ti/Pt阳极电解制备活性氯

以Ti板阴极、Ti/Pt阳极组成无隔膜电解装置,电解低浓度NaCl溶液制得活性氯.研究电解时间、电流密度、氯离子浓度、溶液pH值对活性氯浓度及电流效率的影响.结果表明:电解时间增加,活性氯浓度增加,而电流效率逐渐降低;初始阶段活性氯浓度增加较快,近1 h活性氯浓度趋于稳定;增加氯化钠浓度可提高活性氯浓度和改善电流效率;微酸性电解液有利于提高活性氯浓度.电解过程中,溶液电导率不断降低,pH值变化范围在1之内.     

氯酸钠氧化法制备超细氧化铁黄的研究

利用氯酸钠氧化硫酸亚铁工艺制备超细氧化铁黄,制备过程中采用低成本的氨水合成氢氧化铁。制备过程包括亚铁盐水溶液的氧化、氢氧化铁胶体的合成和转化以及产物的表面处理。产物是分布在长100～230 nm,宽15～30 nm范围的针状粒子。通过X-射线衍射鉴别晶相,利用X-射线衍射和透射电镜测定产物的粒径,考察了反应温度等多种因素对样品的色相和粒径的影响。     

Electroanalysis of Bromate,Iodate and Chlorate at Tungsten Oxide Modified Platinum Microelectrode Arrays

This article describes the direct detection of Bromate, but also of chlorate and iodate, using modified arrays of platinum ultramicroelectrodes. The detection limits for these ions are IO =0.76 μM; BrO =2.34 μM and ClO =133.2 μM. The formation of a suitable tungsten oxide layer and the optimum analytical conditions are described. These oxide layers are formed electrochemically from hydrogen peroxide‐tungstanate solutions in acid conditions. Although film stability may be an issue, particularly at pH>3, these modified arrays of microelectrodes can be used for analytical purposes. After the analysis, the modifying oxide is easily removed and the Pt microelectrode array recovers its original properties.     

Identification and determination of inorganic anions in real extracts from pre- and post-blast residues by capillary electrophoresis

Fast, selective, and sensitive analysis of inorganic anions is compulsory for the identification of explosives in post-blast or environmental samples. For the last twenty years, capillary electrophoresis (CE) has become a valuable alternative to ion chromatography (IC) for the analysis of inorganic-based explosives because of its low running costs and its simplicity of use. This article focuses on the development and validation of a CE method for the simultaneous analysis of 10 anions (chloride, nitrite, nitrate, thiosulphate, perchlorate, chlorate, thiocyanate, carbonate, sulphate, and phosphate) which can be found in post-blast residues, plus for the first time azide anion, possibly present in the composition of detonators, and the internal standard (formate) in 20 min total runtime. Intermediate precisions were 2.11% for normalized areas and 0.72% for normalized migration times. Limits of detection close to 0.5 ppm for all anions were obtained with the use of preconcentration techniques, thanks to a fast and simple sample preparation allowing the analysis of a large variety of matrices with the developed generic CE method. The matrix effects were statistically studied for the first time in the explosive field for different matrices, containing interfering anions and cations, sometimes at high levels. In fact, no significant matrix effect occurred (tests with blank matrix extracts of soil, cloth, glass, plastic, paper, cotton, and metal). Finally, analyses of real post-blast residues and real detonator extracts were performed. The CE results were compared with those obtained with the IC method used routinely and showed excellent correlation.     

Application of the Bismuth Film Electrode for Voltammetric Determination of Titanium Using Ti(IV)‐Oxalate‐Chlorate Catalytic System

The catalytic voltammetric protocol for the determination of titanium at a bismuth film electrode is presented. The method is based on the reduction of the Ti(IV)‐oxalate complex to Ti(III)‐oxalate in an acidic solution. It was proven that the addition of KClO₃ causes rapid oxidation of Ti(III)‐oxalate and, subsequently, an increase of the reduction peak current of Ti(IV) at the bismuth film electrode. Parameters that influence the Ti response, including the film preparation, solution pH, oxalate acid and chlorate concentrations, were optimized. The exploitation of the bismuth film electrode under the optimized conditions yielded a stable response for titanium, with high sensitivity (12.5 μA μM^?1), good precision (RSD=5.0%) and a low detection limit (1×10^?8 M).     

酸性氯酸钾处理-水浴加热全自动凯氏定氮仪测定土壤矿物中的固定态铵

固定态铵作为一种重要的潜在氮源,准确测定其含量,对于认识土壤肥力的形成机理、生态系统氮循环和保障国家粮食安全具有十分重要的意义。固定态铵最常用的方法是Silva-Bremner法,但该方法试剂配制要求严苛,前处理过程操作繁琐、费时。为了实现快速、准确、安全地测定土壤固定态铵的含量,对前处理过程进行了研究,用酸性氯酸钾溶液处理土壤样品,用水浴代替震荡,并与Silva-Bremner法的结果进行了对比。试验了自动凯氏定氮仪工作参数、酸性氯酸钾的浓度和用量、水浴加热的温度和时间,确定了测定土壤固定态铵的最佳条件。结果表明,称取1克样品加入20毫升氯酸钾-盐酸混合溶液（3％-10％）预处理,用0.5mol/L氯化钾溶液交换、洗涤,残渣加入加5mL氢氟酸-盐酸溶液（5mol/L-1mol/L）,在沸水浴加热1.5-2h,用自动凯氏定氮仪蒸馏滴定。对5种类型土壤固定态铵7次测定的结果进行了数据分析,相对标准偏差（RSD）均小于3.87%,最大G值1.49,最大F检验值4.12,最大t检验值0.72,均小于临界值,两种方法测定结果无显著差异。该方法的操作安全性和分析效率得到大幅提高,方法的精密度、准确度满足要求。     

Detection of fuel-oxidizer explosives utilizing portable capillary electrophoresis with wipe-based sampling

Portable analytical instrumentation that can provide an alarm indication for the presence of explosives and related components is critical for the identification of explosives-based hazards and threats. Many explosives incident reports involve an inorganic oxidizer-fuel mixture which can include pyrotechnics, fireworks, flash powders, black powders, black powder substitutes, and improvised or homemade explosives. A portable CE instrument with targeted analysis of common inorganic oxidizer ions, for example, chlorate, perchlorate, and nitrate, was used here as a rapid detection platform. Unlike frequently used gas-phase separation and detection instrumentation such as ion mobility spectrometry (IMS), an automated liquid extraction mechanism is required for CE separation using acetate paper sample collection wipes. Target inorganic oxidizers were inkjet-printed onto sample wipes to investigate instrument response relative to the collected analyte spatial distribution. Overall, analyte signal intensities increased with off-center sample deposition due to improved sample extraction from wipes and no change in response was observed for varied array distributions across wipes. The system demonstrated sub 200 ng detection limits for all target analytes, with further improvement when normalizing to an internal standard.     

用离子色谱法测定水中的二氧化氯、氯、亚氯酸根及氯酸根

建立了一种测定水中的ClO2、Cl2、ClO2^-、ClO3^-离子色谱法,在含有碳酸氢钠缓冲溶液的中性条件下,用NaNO2将ClO2、Cl2还原为ClO2^-、Cl^-,通过测定ClO^-和NO3^-的变化值,间接测定ClO2和Cl2。加入硫代乙酰胺(TAA)作掩蔽剂测定ClO2^-。     

Anhydrous Mercurous Chlorate,Hg2(ClO3)2

Colourless single crystals of the anhydrous mercurous chlorate were grown from a solution of mercuric oxide (HgO) in chloric acid (HClO₃) in the presence of elemental mercury. The crystal structure (monoclinic, P2₁/n, Z = 4, a = 816.59(12), b = 641.02(5), c = 1290.3(2) pm, β = 97.506(12)°, R(all) = 0.0317) contains trans‐O₂ClO‐Hg‐Hg‐OClO₂ molecules with a Hg‐Hg distance of 251.03(4) pm, Hg‐O (bond) distances of 218 and 224 pm and Hg‐Hg‐O angles of 177 and 165°, respectively.     

Reversed flow injection spectrophotometric determination of chlorate

An interfacing has been developed to connect a spectrophotometer with a personal computer and used as a readout system for development of a simple, rapid and sensitive reversed flow injection (rFI) procedure for chlorate determination. The method is based on the oxidation of indigo carmine by chlorate ions in an acidic solution (dil. HCl) leading to the decrease in absorbance at 610 nm. The decrease in absorbance is directly related to the chlorate concentration present in the sample solutions. Optimum conditions for chlorate were examined. A linear calibration graph over the range of 0.1-0.5 mg L⁻¹ chlorate was established with the regression equation of Y = 104.5X + 1.0, r² = 0.9961 (n = 6). The detection limit (3σ) of 0.03 mg L⁻¹, the limit of quantitation (10σ) of 0.10 mg L⁻¹ and the RSD of 3.2% for 0.3 mg L⁻¹ chlorate (n = 11) together with a sample throughput of 92 h⁻¹ were obtained. The recovery of the added chlorate in spiked water samples was 98.5 ± 3.1%. Major interferences for chlorate determination were found to be BrO₃⁻, ClO₂⁻, ClO⁻ and IO₃⁻ which were overcome by using SO₃²⁻ (as Na₂SO₃) as masking agent. The method has been successfully applied for the determination of chlorate in spiked water samples with the minimum reagent consumption of 14.0 mL h⁻¹. Good agreement between the proposed rFIA and the reference methods was found verified by Student's t-test at 95% confidence level.