钴和硼的联合测定

建立了一种联合测定硼酰化钴中钴含量和硼含量的分析方法。采用二甲酚橙为指示剂,EDTA为滴定剂测钴时,加入孔雀绿作衬托剂,可明显改善滴定终点。采用甘露醇强化硼酸滴定硼时,以EDTA为掩蔽剂,可消除二价钴对硼分析的干扰,改用溴甲酚绿－甲基红－酚酞三元混合指示剂作为测定硼的指示剂,使滴定终点灵敏,准确。     

硼酰化镍中硼含量的测定

硼酰化镍作为橡胶与金属的粘合促进剂正越来越被关注。因为镍比钴便宜 ,有可能用硼酰化镍代替钴盐作为粘合促进剂。但是硼酰化镍中硼含量分析却未见文献报道。对于含硼有机化合物中硼的定量方法一般多采用微量或半微量分析 ,即首先将含硼有机化合物分解成硼酸或硼酸盐 ,然后再测定硼酸根离子。含硼有机化合物的分析方法有 :过氧化氢存在下的湿法氧化 [1] ;与过氧化钠或高氯酸钠在一起的熔化分解法 ;氧瓶法 [2 ] 等 ,这些方法的操作均较繁琐。本文采用盐酸 (1 1 )将硼酰化镍分解成无机镍离子与硼酸 ,用 EDTA掩蔽镍离子的干扰。调节 p H值…     

硼酰化钴在橡胶与镀锌钢丝粘合中的应用研究

研究硼酰化钴的用量变化对丁苯橡胶／天然橡胶与镀锌钢丝粘合的影响,通过表面分析对其粘合机理进行了研究。研究表明：硼酰化钴对丁苯橡胶／天然橡胶与镀锌钢丝粘合的粘合增强作用十分明显。硼酰化钴添加2phr左右,粘合性能最佳,同时硫化胶的物理性能得到改善。X-射线光电子能谱分析表明,粘合物镀锌钢丝界面中存在ZnO、ZnS、CoS2,说明粘合时发生了Zn的硫化反应,硼酰化钴中的钴向钢丝表面迁移,继而在锌层中扩散,提高了ZnO和ZnS晶格的缺陷浓度,这两种行为的共同作用,使橡胶与镀锌钢丝的粘合强度显著提高。     

荧光法测定土壤中硼

研究了2-[(5′-羧基-2′-砷酸基苯)偶氮]-1,8-二羟基-3,6-萘二磺酸(5-CarAsA-1)与硼的荧光性能。硼与试剂形成1:2的强荧光配合物,其λ_(ex)/λ_(em)=240nm/381nm,B(Ⅲ)量在0～0.16mg·L~(-1)范围内呈良好线性关系。方法检出限为2μg·L~(-1)。建立了测定缴量硼的新方法。方法应用于土壤中微量硼的测定,结果满意。     

微波消解-ICP-AES法测定钴基合金中的硼

采用微波消解-ICP-AES法测定钴基合金中硼元素。通过试验探讨了钴基高温合金中基体元素,主量元素如铬、钨、钼等对硼元素分析谱线的光谱干扰情况,采用基体匹配法对基体干扰进行校正,确定了合适的分析谱线。方法的线性范围为0～8 mg/L,检出限为0.0003%。测定结果的相对标准偏差为1.88%～6.04%(n=6),回收率为92.0%～104.2%。     

原位合成钴/还原氧化石墨烯纳米粒子催化氨硼烷制氢

采用简单的原位还原合成方法,利用具有温和还原性能的氨硼烷作为还原剂,在室温下一步还原氧化石墨烯和氯化钴混合溶液制备了还原氧化石墨烯负载钴纳米复合材料催化剂. 利用所制备的钴/还原氧化石墨烯催化剂催化氨硼烷水解制氢,发现钴/还原氧化石墨烯具有优异的催化性能. 相对于没有负载的钴纳米粒子以及采用硼氢化钠作为还原剂制备的钴/还原氧化石墨烯催化剂,采用氨硼烷还原制备的钴/还原氧化石墨烯催化剂表现出更加优越的催化性能. 动力学测试表明,钴/还原氧化石墨烯催化氨硼烷水解反应为零级反应,同时钴/还原氧化石墨烯催化剂催化氨硼烷水解反应的活化能为27.10 kJ·mol^-1,低于大部分已报道的其它催化剂,甚至一些贵金属催化剂的活化能. 钴/还原氧化石墨烯催化剂有着稳定的循环使用性,特别是其具有的磁性使得它能够直接从溶液中通过磁力回收,极具应用前景. 这种简单有效的合成方法有望推广到其它的金属-还原氧化石墨烯纳米复合材料体系.     

原位生成非晶纳米钴高效催化氨硼烷的醇解制氢

用金属钴配合物和过渡金属(Cu,Ni,Co等)原位生成的非晶纳米粒子作为均相、多相催化剂,研究氨硼烷的醇解放氢反应,结果发现原位生成的非晶钴纳米粒子展现出优异的产氢性能。通过10次的催化循环测试,钴纳米粒子放氢催化转换数(TON)可达6 000,最高催化产氢速率(TOF)达515 mol_(H_2)·mol_(metal)~(-1)·h~(-1)。该催化剂制备方便,且产氢稳定性好。此外,对钴纳米粒子催化氨硼烷放氢实验做动力学研究,计算其催化活化能为20.00 kJ·mol~(-1),低于大多数已经报道的其他纳米催化剂催化氨硼烷放氢反应的活化能。通过硼谱的跟踪检测,发现钴纳米催化氨硼烷的醇解反应产物是硼酸三甲酯,并对此催化反应机理进行了初步的解释和讨论。     

姜黄素法测定微量硼

硼的吸光光度法已有不少报道,次甲基蓝法是被广泛采用的方法之一,但要使用大量有毒的二氯乙烷。其他的显色剂还有1,1′-二蒽醌亚胺、醌茜素、胭脂红酸,但操作麻烦。后来又研究了硼水杨酸-乙基紫及硼水杨酸-罗丹明6C等三元络合物的方法,但灵敏度仍提不高。所以,灵敏度很高的姜黄素法仍然是目前广泛采用的方法。蒸干法的姜黄素法较费时,我们试验了直接显色法的条件。研究结果,本法简单快速、灵敏度高、重现性好,用于粮食、水质等样品中微量硼的测定,结果满意。　 1 试验部分     

滴定法测定含硼富燃推进剂燃烧残渣中总硼含量

为了深入研究含硼富燃料推进剂一次燃烧反应机理,为化学反应机理的研究提供直接的试验依据,测定燃烧残渣中物质的量是十分必要的.含硼富燃料固体推进剂在纯氮气中点火燃烧后的燃烧残渣中总硼含量的测定方法,国内尚无统一的方法.目前硼粉纯度检测时多采用硝酸溶解,用指示剂法或电位滴定法进行滴定.     

稀土在降低电解渗硼层脆性中的作用

采用熔盐电解法分别对45钢试样进行了渗硼和稀土-硼共渗处理,用三点弯曲声发射试验测定其脆性。对比实验结果表明,稀土元素的加入可大大降低电解渗硼层的脆性。通过裂纹形貌观察、稀土元素在硼化物和α-Fe中的固溶分析以及对Fe_2B点阵常数的影响,探讨了稀土元素对降低电解渗硼层脆性的原因。     

Process monitored spectrophotometric titration coupled with chemometrics for simultaneous determination of mixtures of weak acids

A new spectrophotometric titration method coupled with chemometrics for the simultaneous determination of mixtures of weak acids has been developed. In this method, the titrant is a mixture of sodium hydroxide and an acid-base indicator, and the indicator is used to monitor the titration process. In a process of titration, both the added volume of titrant and the solution acidity at each titration point can be obtained simultaneously from an absorption spectrum by least square algorithm, and then the concentration of each component in the mixture can be obtained from the titration curves by principal component regression. The method only needs the information of absorbance spectra to obtain the analytical results, and is free of volumetric measurements. The analyses are independent of titration end point and do not need the accurate values of dissociation constants of the indicator and the acids. The method has been applied to the simultaneous determination of the mixtures of benzoic acid and salicylic acid, and the mixtures of phenol, o-chlorophenol and p-chlorophenol with satisfactory results.     

非水滴定法测定酰胺缩醛

对非水滴定酰胺缩醛的溶剂、滴定剂和指示剂进行了选择试验，用ＨＣｌ甲醇标准液进行滴定，通过电位滴定曲线或甲基橙指示剂可以准确的确定滴定终点，方法简便，结果准确。     

Complexometric titration of Aluminium

A procedure is given for the complexometric titration of aluminium. A known volume of a standard solution of EDTA is added to the sample solution, and the excess is back-titrated with a zinc sulphate solution, dithizone being used as indicator. The titration is performed at pH = 4.0 — 4.5 and 40 — 50% alcohol is added as solvent for the indicator.The theoretical basis of the method is developed, and the theoretical titration error with various amounts of aluminium and zinc is calculated.The results of some titrations are given.     

Precise chelatometric titrations of zinc, cadmium, and lead with molecular spectroscopy.

Spectral data during a chelatometric titration were utilized for determining an equivalence point of the titration. Three-dimensional titration data were analyzed by fitting to a theoretical equation that was derived from equilibrium equations among a metal ion, an indicator and EDTA. The equation with optimized parameters successfully explained the three-dimensional titration data. This method was applied to EDTA titration systems of zinc, cadmium and lead with xylenol orange (XO) as an indicator. These systems were analyzed while taking the formation of 1:1 and 2:1 metal-indicator complexes into account. By this method, an accurate equivalence point was determined as well as stability constants and molar absorption spectra of metal-indicator complexes in each titration system. Moreover, the comparability among the concentrations of the metal standard solutions prepared from pure metals (Zn, Pb, and Cd) was also confirmed by the proposed evaluation method.     

Ferrimetric determination of uranium using rhodamine 6G as fluorescent indicator

Experimental conditions have been developed for the titration of uranium^IV with iron^III alum solution, using Rhodamine 6G as a fluorescent indicator. The titration is best carried out at 98–100° in a 2–3N hydrochloric acid medium, under filtered ultraviolet light, using 2.0 ml of 0.05% Rhodamine 6G solution for 30 ml of the titration mixture. A slight excess of iron^III solution quenches the greenish-yellow fluorescence of the dye through inner filter action. With the titration assembly described here, it is possible to determine uranium^IV with an accuracy of about 0.4%. This method appears to be more convenient than the potentiometric titration or the method employing potassium thiocyanate as internal indicator.

Evidence is also presented to show that the reaction between uranium^IV and iron^III is slow at room temperature.     

A note on successive complexometric determination of thorium and rare earths

An improved method for successive determination of thorium and rare earths is described. It is based on the EDTA titration of thorium at pH 2 (Xylenol Orange as indicator) followed by addition of acetylacetone-acetone mixture, adjustment of the pH to 5-5.5 with hexamine, and by further EDTA titration of rare earths with the same indicator.     

A Restudy of Direct Chelatometric Titration of Vanadium(IV) with N-Benzoyl-N-phenylhydroxylamine as Indicator

This paper restudies the method of direct chelatometric titration of V(IV) with N-benzoyl-N-phenylhydroxylamine (BPHA) as indicator. The indicator functions entirely differently from indicators hitherto used in chelatometry. The solution contains two independent systems – the indicator and the titrand-titrant system – without any color changing species. The BPHA-V(V) chelate once formed as the result of aerial oxidation constitutes the indicator system and does not react with EDTA. Its color therefore remains unchanged throughout titration. It is not a metallochromic indicator. Its function is that of color-screening. The color of the titrant system deepens during titration, but does not change. The end-point is indicated by one color completely covering up the other. Hence, this method is of purely empirical nature.Received July 5, 2002; accepted February 11, 2003 Published online July 16, 2003     

Simultaneous microdetermination of iodine and sulfur in organic compounds

A simple and rapid method for the simultaneous microdetermination of iodine and sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion, the iodide ions titration with 0.01 N mercuric perchlorate solution and diphenylcarbazone as indicator and the sulfate ions titration with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are in good agreement with calculated values.     

Determination of hexafluoropropan-2,2-diol in its binary mixtures with water

A visual titration method for the determination of hexafluoropropan-2,2-diol (HFPD) in HFPD-water mixtures is suggested. The procedure involves the titration of the weakly acidic HFPD with sodium methoxide, using dimethylformamide or ethanol as solvent and thymol blue as indicator. The results are in good agreement with the ones obtained by potentiometric titration in water.