库仑滴定法测定烟叶提取物中茄尼醇

本文提出用库仑滴定法测定茄尼醇。以含有1mol·L－1KBr的78％（V／V）醋酸溶液为介质，以5mA恒电流为电解电流，对布尼醇进行库仑滴定，用双铂电极电流法指示滴定终点，得到满意结果．方法简便、准确，不需要标准溶液，不需要昂贵仪器。     

库仑滴定法测定己内酰胺与聚醚样品中过氧化物的含量

建立了库仑滴定法测定己内酰胺与聚醚样品中过氧化物含量的方法。铂片电极分别作电解电极对和指示电极对,以1.00 mol·L~(-1)氯化铈溶液为支持电解质,经1.0 mA电流电解生成Ce~(4+)后,与样品溶液中过氧化物定量发生氧化还原反应,根据法拉第电解定律,计算样品中过氧化物的含量。结果表明:标准曲线的线性范围为24.11～301.35 mg·L~(-1),检出限(3s)为7.2μg·g~(-1)。采用该方法分析实际样品,测定结果与电位滴定法的结果无显著性差异,测定值的相对标准偏差(n=5)均低于3.0%。     

库仑滴定法快速测定白酒中总酯的含量北大核心CSCD

提出了库仑滴定法测定白酒中总酯含量的方法。以铂电极为工作电极对,pH复合玻璃电极为指示电极,0.80 mol·L^(-1)硫酸钾溶液为支持电解质,通过恒电流电解生成的H~+滴定预处理后样品中剩余的OH^(-),直至滴定终点pH 7.70,根据法拉第电解定律测得样品中总酯的含量。结果表明:测定过程约10 min完成。按标准加入法进行回收试验,回收率为88.0%~106%。方法用于实际白酒样品中总酯含量的测定,测定结果与国家标准规定的电位滴定法测定结果无显著性差异。     

库仑双点电位滴定法测定酒的总酸度

库仑滴定法测定酸,通常用铂电极作电生电极,为了避免阳极产生H~+的干扰,需要将阴极与阳极隔开,由于隔膜的影响,库仑池内阻增大,这就要求恒电流电源输出更高电压,或要求降低恒电流强度,这样对于高含量的测定就受到限制。用银电极为阳极,在卤化物电解     

库仑滴定法间接测定补锌片中锌

以pH 9.2的1.0mol·L~(-1)碘化钾-四硼酸钠溶液为支持电解质溶液,铂电极作为电解电极与指示电极,于室温下电解生成碘10s后加入补锌片样品溶液滴定剩余的半胱氨酸,采用库仑滴定法指示滴定终点,根据法拉第电解定律,间接测定样品溶液中锌含量。锌的质量浓度在0.05～0.50g·L~(-1)内与其消耗的电量呈线性关系,检出限(3s)为0.04mg·L~(-1)。方法用于补锌片样品的分析,测定值的相对标准偏差(n=6)为0.76%～0.92%,测定值与标示量不存在显著性差异。     

锑电极-库仑滴定法快速测定壳聚糖脱乙酰度

为了克服pH玻璃电极在浑浊、黏稠的壳聚糖溶液中响应H+活度滞后的缺陷,提出了采用锑电极作为指示电极和钨电极作为参比电极的指示电极对指示滴定终点的库仑滴定法快速测定壳聚糖脱乙酰度的方法。壳聚糖滴定可在5min左右完成。分别分析了5种壳聚糖样品,测定结果与核磁共振氢谱法的测定值接近。     

库仑滴定法测定新洁尔灭溶液中溴化苄烷铵的含量

应用库仑滴定法测定了新洁尔灭溶液中溴化苄烷铵的含量。用0.09mol·L-1硝酸溶液和0.5%(w)明胶溶液以体积比10比1混合的混合溶液作电解液,银棒作阳极进行恒电流电解,电解电流为10mA。电解过程中,从银电极释放出的Ag+与试液中溴化苄烷铵的Br-反应生成沉淀。Br-被完全沉淀时,电流上升,滴定到达终点,根据法拉第定律计算溴化苄烷铵的含量。溴化苄烷铵的质量浓度在0.422 8~1.480g·L-1范围内与所消耗的电量之间呈线性关系。对同一样品的分析,本方法的测定结果与四苯硼钠滴定法的测定结果相符,本方法测定结果的相对标准偏差(n=6)为0.9%。用标准加入法进行回收试验,测得回收率在99.6%~102%之间。     

CPC零电流示波电位滴定法测定陶瓷铂金水中的铂（Ⅳ）

提出了一个快速测定铂（Ⅳ）的零电流示波电位滴定法。以氯化十六烷基吡啶为滴定剂，用铂电极和银电极为指示电极，利用阴极射线示波器荧光屏上荧光点的突然位移来指示ＣＰＣ滴定ｐｔ（Ⅵ）的终点，具有灵敏、准确、快速等特点。用该法测定陶瓷铂金水中的铂，结果良好。     

用精密库仑滴定法测定三氧化二砷的纯度

一、前言三氧化二砷是容量分析中常用的一种基准物质。Marinenko和Taylor曾用电解氧化碘离子产生碘的库仑滴定法测定其纯度,同时研究了电解产生碘的电流效率。Newton亦进行过类似的工作,他们都获得了很高的测量精度。在本工作中用积分残余电流的方法进一步研究了电解产生碘的电流效率及其与电解质溶液的pH关系。测定三氧化二砷纯度的精度为31ppm。     

非水库仑滴定法测定天然水体中溶解的无机碳

介绍用非水库仑滴定法测定天然水体中溶解的无机碳，对非水库仑滴定方法的关键技术－非水电解液进行了组分选择及优化，并对实验条件进行了优化。用该方法对碳酸钠标准溶液进行测定，测定结果的相对标准偏差为0.18%，测定值与理论值的平均相对误差为0.48%，表明该方法具有较高的精密度与准确度。     

Densities,speeds of sound,excess volumes and viscosities of binary mixtures of mtbe with tetralin and decalin at 303.15 k

Measurements of densities, speeds of sound, excess volumes and viscosities of binary mixture of methyl tert-butyl ether with tetralin and decalin are reported at 303.15?K over the entire range of composition. Excess volumes are measured using batch dilatometer technique. Sound speeds are obtained using ultrasonic interferometer. Densities are computed from excess volume data. Isentropic compressibilities are derived from density and sound speed data. Speeds of sound are evaluated on the basis of Jacobson's free length theory and Schaff's collision factor theory. The predicted values are in good agreement with the experimental results. The viscosity data are analysed on the basis of corresponding states approach. Excess volumes and deviation in isentropic compressibilities are negative and deviation in viscosities are positive over the entire composition range. The experimental results are discussed in terms of possible molecular interactions between unlike molecules.     

On topological and geometrical distance matrices

Differences between topological and geometrical distance matrices are examined. Some examples of geometrical distances when graphs are embedded in spaces of different dimensions are given. Relations of topological distance matrices to other graph matrices are shown. The topological distance matrices are defined in the Hilbert space and their elements are distances through the graph lattices.     

Mechanisms of antioxidant action: Effect of processing on the transformation products of thiophosphoryl compounds in polyolefins

It is shown that low density polyethylene or polypropylene processed in the presence of thiophosphoryl disulphides or thiocarbamoyl disulphides in air or in the presence of hydroperoxides are much more photo-stable than analogous samples processed normally. This is found to be true when the additives are added at normal (low) concentration levels or as concentrates which are subsequently diluted in the polymer to normal levels. Among the products formed when bis dialkyl dithiophosphoryl disulphides are oxidatively processed in polyethylene are polymer-bound thiophosphoryl compounds which are believed to generate sulphur acids slowly in the polymer.     

Some Strategies for the Refinement of Disordered Structures with the SHELXL-97 Refinement Program

1 INTRODUCTION finement stage. The person performing the crysta- llographic manipulations works on numerical data The high degree of order in the arrangement of that are quite different from the diffraction images atoms in a crystal is a fundamental characteristic of on a computer terminal, and most often does not even the crystalline state, an ideal crystal being envisaged see the images. to be constructed of regularly-stacked unit cells, each The refinement program, SHELXL-97[1], has …     

Field Effects in Nematic Liquid Crystals in Terms of Catastrophe Theory

The field effects in nematic liquid crystal layers are reanalysed using catastrophe theory. The layer with pretilted director orientation and obliquely applied magnetic field, the hybrid aligned nematic cell and twisted nematic structures are considered. The stable solutions are identified and transitions between them are specified. The results are in essential agreement with previous work. Some details concerning the behaviour near the threshold are revealed.     

Structures, energetics, and spectra of hydrated hydroxide anion clusters

The structures, energetics, electronic properties, and spectra of hydrated hydroxide anions are studied using density functional and high level ab initio calculations. The overall structures and binding energies are similar to the hydrated anion clusters, in particular, to the hydrated fluoride anion clusters except for the tetrahydrated clusters and hexahydrated clusters. In tetrahydrated system, tricoordinated structures and tetracoordinated structures are compatible, while in pentahydrated systems and hexahydrated systems, tetracoordinated structures are stable. The hexahydrated system is similar in structure to the hydrated chloride cluster. The thermodynamic quantities (enthalpies and free energies) of the clusters are in good agreement with the experimental values. The electronic properties induced by hydration are similar to hydrated chloride anions. The charge-transfer-to-solvent energies of these hydrated-hydroxide anions are discussed, and the predicted ir spectra are used to explain the experimental data in terms of the cluster structures. The low-energy barriers between the conformations along potential energy surfaces are reported.     

Trace element determination in suspended matter and in sedimetns-by instrumental neutron activation analysis

By means of instrumental neutron activation, more than 20 trace elements are determined in suspended matter in Rhine water, Main water and Rhine sediments. Monoelement and multielement standards are used for calibration. Sample collection, separation of suspended matter by filtration or centrifugating and sample preparation are described. The results obtained by filtration and by centrifuging are compared. Interferences in evaluation of the γ-spectra and their influence on the results are discussed. Systematic errors are detected by participation in ring analysis.     

Chemiluminescence in analytical chemistry

Analytical applications based on chemiluminescence are reviewed. Analyses in the gas phase for atmospheric pollutants such as sulphur compounds, ozone and oxides of nitrogen are described. The commonest chemiluminescent systems used in the liquid phase are then discussed. Their applications as indicators in different types of titration are outlined. Determinations of organic and inorganic substances are classified according to their action as oxidant, catalyst or inhibitor. Special applications are described in fields such as forensic science, microbiology, polymer technology, radiation chemistry and flow mechanics.     

Utilizing biotechnology in producing fats and oils with various nutritional properties

The role of dietary fat in health and wellness continues to evolve. In today's environment, trans fatty acids and obesity are issues that are impacted by dietary fat. In response to new information in these areas, changes in the amount and composition of edible fats and oils have occurred and are occurring. These compositional changes include variation in fatty acid composition and innovation in fat structure. Soybean, canola, and sunflower are examples of oilseeds with varied fatty acid composition, including mid-oleic, high-oleic, and low-linolenic traits. These trait-enhanced oils are aimed to displace partially hydrogenated vegetable oils primarily in frying applications. Examples of oils with innovation in fat structure include enzyme interesterified (EIE) fats and oils and diacylglycerol oil. EIE fats are a commercial edible fat innovation, where a lipase is used to modify the fat structure of a blend of hard fat and liquid oil. EIE fats are aimed to displace partially hydrogenated vegetable oils in baking and spread applications. Diacylglycerol and medium-chain triglyceride (MCT)-based oils are commercial edible oil innovations. Diacylglycerol and MCT-based oils are aimed for individuals looking to store less of these fats as body fat when they are used in place of traditional cooking and salad oils.     

叠氮二异丁基铝的构造及其缔合-解离平衡研究

叠氮二异丁基铝（DBAA）是一个新合成的化合物。通过相对分子质量的测定、氢－核磁共振谱和铝－核磁共振谱的测定,确定了DBAA三聚体的分子构造;在溶液中研究了DBAA的三聚体和单晶体之间的缔合－解离平衡。这个平衡受溶剂性质、温度的影响。借助铝－核磁共振谱和相对分子质量的测定计算了DBAA三聚体的解离平衡常数、解离焓和解离熵等热力学数据。