Determination of traces of perchlorate in chlorate solutions

Perchlorate present in chlorate solutions is determined gravimetrically as tetraphenylphosphonium perchlorate after destruction of chlorate by addition of hydrochloric acid. Interference of Fe(III) and Cr(III) is prevented by complexing with tarartic acid. Replicate analyses of a sodium chlorate solution containing NaClO(3), NaCl, Na(2)Cr(2)O(7), and 390 ppm NaClO(4) showed 405 ppm NaClO(4) (standard deviation 19 ppm, 12 results).     

Sur le dosage de chlorure en présence d'hypochlorite,chlorite et chlorate alcalins

A method has been developed for determining the chloride anion with silver nitrate in presence of the hypochlorite, chlorite and chlorate anions.The chlorate anion does not interfere with the determination. In the presence of chlorite anions the figures for Cl' are too low in acid media.The hypochlorite anion should be reduced to the Cl' anion by PENOT'S solution.     

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.     

EDTA滴定法测定除尘灰中锌含量

采用灰化后再溶解试样的方法,成功解决了除尘灰因碳含量过高而难于溶解的问题;将灰化后的试样以HCl-HNO3-HF-HClO4混酸溶解,在氯酸钾存在下,以铁盐作载体,用氨水沉淀分离大部分铁、铝、铅等元素,以硫脲-氟化物、硫代硫酸钠、抗坏血酸作掩蔽剂,掩蔽剩余少量铜、锡、铁等干扰元素,在pH=5.5~6条件下,以二甲酚橙为指示剂,用EDTA标准溶液滴定得到锌的含量。方法的相对标准偏差在0.75%~2.8%,加标回收率在98.0%~102%。方法操作简便,且分析结果准确度、重现性较好,可以满足生产检验的需要。     

极谱法测定化探样品中钨钼的技术改进

针对传统极谱法测定化探样品中钨钼时操作手段繁琐问题加以改进。试样以硫酸-二苯乙醇酸-二苯胍-氯酸钠体系为混合底液,将经过碱熔融后的样品以甲基橙为指示剂,用硫酸(1+1)调酸度后,加入固定比例的混合底液,摇匀,无需定容,放置25~30min后直接测定。采用二次倒数波测定,钨峰电位在-660mV左右,钼峰电位在-30mV左右,钨钼的质量浓度在0.02~1.0μg/mL内呈线性关系,钨检出限为0.5μg/g,钼检出限为0.3μg/g。方法灵敏度高,快捷、简单,适用于大批量化探样品的测定。     

Alternating current polarographic determination of microgram amounts of iodide ion by means of the catalytic oxidation of 1-amino-2-naphthol-4-sulfonic acid

The catalytic oxidation of 1-amino-2-naphthol-4-sulfonic, acid proceeds quickly with microgram amounts of iodide in the presence of sodium chlorate at pH between 1.3 and 2.0. The oxidation product shows a sensitive tensammetric wave at potentials of about +0.03 V vs. SCE (pH 1.75), so that the catalytic reaction was applied for the determination of microgram amounts of iodide ion. The most suitable conditions of the pH range, the concentration of ANS and sodium chlorate, reaction temperature and standing are 1.3–2.0, 3 × 10^?4M, 0.05 M, 50° C and 1 h respectively. Using the recommended procedure, iodide ion can be determined precisely in the concentration range 0.4–6.5 ng ml^?1 with a relative error of about 3%. Interference of foreign species and the application to the determination of total iodine in river and sea water are described.     

抑制型离子色谱法检测植物样品中植酸根及磷酸根的含量

采用抑制型高效离子色谱法检测植物样品中植酸根和磷酸根的含量。样品用1%(质量分数)三氯乙酸处理,离心沉降 后取上清液经0.45 μm微孔滤膜过滤后注入离子色谱仪。用0.22 mol/L氢氧化钠水溶液、水和50%(体积分数)异丙醇水 溶液进行梯度淋洗,经微膜抑制后检测其电导率。实验结果表明,植酸根与磷酸根的检测不受F-、Cl-、SO2-4、NO-3、CC l3CO-2等阴离子的干扰。植酸根、磷酸根的质量浓度分别为5~400 mg/L和5~500 mg/L 时与峰面积呈良好的线性关系(r2分别为0.9994和0.9999),检出限分别为3.5 mg/L和1.5 mg/L;植酸根、磷酸根的平均 回收率分别为99.8%和98.4%,检测结果的相对标准偏差分别为1.98%和2.09%。     

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。     

Direct potentiometric titration of chlorite in presence of chlorate, chlorine dioxide and chloride

A direct potentiometric titration of chlorite in the presence of chlorate, chlorine dioxide and chloride is described. Chlorite is determined in 0.01-0.0005 M sodium chlorite at pH 2.0-3.5 using hypochlorite solution. The course of the reaction is followed potentiometrically using saturated calomel and platinum electrodes; the end-point is indicated by a potential jump of about 230 mV. Under these conditions no reaction takes place with chlorate, chlorine dioxide or chloride. Previously, the determination of chlorite in such mixtures was only possible by difference from several oxidimetric titrations.     

Thermoanalytical properties of analytical grade reagents V. Sodium halates

The thermoanalytical properties of sodium halates have been investigated by means of a derivatograph and a visual DTA instrument. The thermal decomposition of the compounds studied was found to proceed only in the melt phase to a measurable extent, while the corresponding sodium halides were being formed. For sodium chlorate the formation and decomposition of sodium perchlorate could also be observed. The comparison of the results of thermal investigations with results of X-ray measurements has shown that the ionic character of the chemical bonds is highest for sodium iodate and lowest for sodium chlorate.     

Determination of chlorine containing species in explosive residues using chip-based isotachophoresis

A new method has been developed to allow the determination of the chlorate, chloride and perchlorate anions in inorganic explosive residues to be made using isotachophoresis (ITP). To enable a good separation of these species to be achieved the method involves the use of two complexing agents. Indium(III) is used to allow the determination of chloride whilst using nitrate as the leading ion and alpha-cyclodextrin is used to allow the separation of chlorate and perchlorate. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. The method was applied to analysing both model samples and actual inorganic explosive containing residue samples. Successful determinations of these samples were achieved with no interference from other anions typically found in inorganic explosive residues. Limits of detection (LOD) for the species of interest were calculated to be 0.80 mg l(-1) for chloride, 1.75 mg l(-1) for chlorate and 1.40 mg l(-1) for perchlorate.     

Chiral hide-and-seek: retention of enantiomorphism in laser-induced nucleation of molten sodium chlorate

We report the observation of non-photochemical laser-induced nucleation (NPLIN) of sodium chlorate from its melt using nanosecond pulses of light at 1064 nm. The fraction of samples that nucleate is shown to depend linearly on the peak power density of the laser pulses. Remarkably, we observe that most samples are nucleated by the laser back into the enantiomorph (dextrorotatory or levorotatory) of the solid prior to melting. We do not observe a significant dependence on polarization of the light, and we put forward symmetry arguments that rule out an optical Kerr effect mechanism. Our observations of retention of chirality can be explained by decomposition of small amounts of the sodium chlorate to form sodium chloride, which provide cavities for retention of clusters of sodium chlorate even 18 °C above the melting point. These clusters remain sub-critical on cooling, but can be activated by NPLIN via an isotropic polarizability mechanism. We have developed a heterogeneous model of NPLIN in cavities, which reproduces the experimental data using simple physical data available for sodium chlorate.     

Thermal decomposition of sodium chlorate and chromium(III) oxide mixtures

A study of the thermal decomposition of intimate mixtures of sodium chlorate and chromium(III) oxide in different molar ratios was made employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. Sodium chlorate in the presence of chromium(III) oxide starts to decompose around 180°, which is much below the decomposition temperature of pure NaClO₃. Each mole of Cr₂O₃ consumes 8/3 moles of NaClO₃, undergoing oxidation to sodium dichromate.     

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.     

Determination of low concentrations of chlorite and chlorate ions by using a flow-injection system

A flow-injection method is reported for the determination of chlorite ion and chlorite and chlorate ions in mixtures at the submilligram per liter level in drinking water. The chlorite ion concentration is selectively determined by using its reaction with iodide ion at pH 2, which liberates iodine. Both species react with iodide ion in6 M HCl to produce iodine, the concentration of which is measured spectrophotmetricaly at 370 nm. The individual species are determined using multiplel regression. The method exhibits a linear range from 2 to 150 μM (0.1–10.1 mg l^-1) for chlorite ion and from 2 to μM (0.1–8.3 mg l^-1 for chlorate ion, with relative standard deviations of 0.4 and 1.2%, respectively.     

EDTA滴定法连续测定铅精矿中铅和锌

建立了EDTA滴定法连续测定铅精矿中铅和锌的方法。试样用盐酸、硝酸、硫酸和氯酸钾分解。铅通过硫酸铅沉淀与其他干扰元素分离,沉淀溶解于乙酸-乙酸钠溶液中。在滤液中加入氨水、氟化钾使铁等干扰元素沉淀并与锌溶液分离。用二甲酚橙作指示剂,EDTA分别滴定溶液中的铅和锌。研究中测定了能力验证NILPT(2010)-0211铅精矿样品10-1和10-2中铅和锌,结果满意。     

Thermal decomposition of alkali metal perchlorates

The effect of past mechanical history on the subsequent thermal decomposition kinetics of sodium, potassium, rubidium and caesium perchlorates, has been investigated. At low temperatures the decomposition of all these salts is significantly sensitized by pre-compression. At high temperatures, however, prior compression results in a lowered decomposition rate in the case of potassium, rubidium and caesium perchlorates and in an increase in the thermal reactivity of sodium perchlorate. The high temperature behaviour is shown to be an indirect consequence of the low temperature behaviour. The difference in behaviour between sodium perchlorate and the other alkali metal perchlorates is explained on the basis of the stability of the respective chlorates, formed during the low temperature decomposition. This is substantiated by experiments which show that the addition of sodium chlorate to sodium perchlorate brings about a sensitization while potassium perchlorate admixed with potassium chlorate results in a desensitization at high temperatures.     

An ion-exchange method for selective separation of palladium, platinum and rhodium from solutions obtained by leaching automotive catalytic converters

An ion-exchange method has been developed for the separation of palladium, platinum and rhodium from a solution that is highly acidic and contains a considerable amount of lead, aluminum, iron and cerium, obtained by leaching a used honeycomb type automotive catalytic converter. A column of Amberlite IRA-93 anion-exchange resin was found appropriate to recover platinum metals from the pregnant solution. Selective stripping of these metals from the resin was achieved by eluting rhodium first with 6.0M hydrochloric acid, then palladium with a 1% ammonia solution at ambient temperature, and platinum with 5% of the reagent at elevated temperatures. Optimum conditions for leaching these metals from the catalyst were 5.0M hydrochloric acid and 0.4M sodium chlorate at 70 degrees C. This method can be applied to both analytical as well as large scale operations. It is simple, economical, and relatively safe for human exposure and the environment.     

The chlorate-iodine clock reaction

A clock reaction produced by mixing chlorate and iodine solutions in perchloric acid media is reported. This is the first example of a clock reaction using chlorate as a reagent. Increasing chlorate and acid concentration reduces the induction period. Changing the initial iodine concentration does not affect the length of the induction period. The discovery of this clock reaction opens the possibility that a new family of oscillation reactions can be built using chlorate as reagent.     

Brodie's or Hummers’ Method: Oxidation Conditions Determine the Structure of Graphene Oxide

Synthesis and studies of graphite oxide started more than 150 years ago and turned into a boom by the measurements of the outstanding physical properties of graphene. A series of preparation protocols emanated trying to optimize the synthesis of graphene oxide in order to obtain a less defective material, as source for graphene. However, over-oxidation of the carbon framework hampered establishing structure-property relationships. Here, the fact that two different synthetic methods for graphene oxide preparation lead to very similar types of graphene oxide with a preserved graphene lattice is demonstrated. Either sodium chlorate in nitric acid (similar to Brodie's method) or potassium permanganate in sulfuric acid (similar to Hummers’ method) treatment are possible; however, reaction conditions must be controlled. With a preserved carbon lattice analytical differences between the samples relate to the altered on-plane functionality. Consequently, terming preparation protocols “according to Brodie's/Hummers’ method” is not sufficient.