Surface charge density on spherical silica particles in aqueous alkali chloride solutions

The results of a systematic investigation on the influence of different alkali ion species on the surface charge density, ₀, of spherical silica particles (AEROSIL 300) in the pH range between 4 and 8 and with electrolyte concentrations from 0.005 M to 0.3 M are presented. The accuracy of the data may be described by a residual deviation,s( ₀ ^m ), including at least four single measurements:s( ₀ ^m )>0.2C/cm². The alkali sequence found for the spherical particles is in agreement with data for porous silica published by other authors.     

以5-Cl-PADAB为指示剂用EDTP光度滴定铜

本文提出在pH5.5水溶液中,在510nm处,以5—Cl—PADAB为指示剂,用EDTP光度滴定铜。本法的终点响应迅速,选择性高,适用于滴定5～2000μg铜,已用于铅合金、铝合金和锌合金中铜的测定。     

Synthesis and Crystal Structure of a Three-dimensional Cd(Ⅱ) Coordination Polymer [Cd(μ1,3-SCN)(μ3-pco)]n (pco = Pyrazine-2-carboxylate 4-oxide Anion)

The three-dimensional complex [Cd(μ1,3-SCN)(μ3-pco)]n has been synthesized with μ1,3-SCN- and pco as mixed bridged ligands. The crystal belongs to monoclinic, space group P21/n with a = 10.3777(16), b = 6.2592(9), c = 13.150(2) (A), β= 97.317(2)°, V=847.2(2) (A)3, Z= 4,C6H3CdN3O3S, Mr = 309.575, Dc = 2.427 g/cm3, F(000) = 592 and μ = 2.804 mm-1. The structure was refined to R = 0.0255 and wR = 0.0550 for 1712 observed reflections (I＞2σ(I)). In the crystal the Cd(Ⅱ) ions are coordinated by μ1,3-SCN- and μ3-pco bridge ligands to form a three-dimensional structure.     

铀酰离子和2，3－二羟基－5－甲氧羰基苄基胺羧酰胺螯合剂及小分子配体的三元混配反应研究

用ｐＨ电位法在２５℃，离子强度为０．１（ＫＮＯ３）条件下研究了铀酰离子和六种２，３－二羟基－５－甲氧羰基苄基胺羧酰胺螯合剂、五种在人体血液中含量最高的小分子配体的三元配位反应，得到混配配合物的生成常数，讨论了其稳定性．通过分布计算说明促排过程中可能形成铀酰离子的混配配合物．     

Hydrogen diffusion through a steel membrane from solutions of the C2H5OH-H2O-HCl system: Effect of cathodic and anodic polarizations

Effect of cathodic and anodic polarizations on the hydrogen diffusion through a steel membrane from ethanol solutions of hydrochloric acid with a constant ionic strength is studied. The relation of the diffusion flux to the potential of the membrane’s entrance side; concentration of protons in a solvate form; water content in the mixed solvent; and the presence of the thiocyanate ions, which stimulate hydrogen sorption, is considered.     

电导滴定的联机测试

提出把电导滴定所用仪器和ＰＣ机组成联机测试装置，使用专门设计的程序采集滴定数据和动态显示滴定曲线，滴定完毕，计算机在数分钟内完成全部的数据处理和保存，并打印输出测试结果。这种联机方式，数据采集与处理直观迅速，且采集之电导数据精度明显提高。平行测试９个样品的结果相对标准偏差一般在０．３０％以下。     

Study of the cyclen derivative 2-[1,4,7,10-tetraazacyclododecan-1-yl]-ethanethiol and its complexation behaviour towards d-transition metal ions

The compound 2-[1,4,7,10-tetraazacyclododecan-1-yl]-ethanethiol (L2) has been synthesized and characterized by multinuclear NMR spectroscopy and mass spectrometry. Its thiol-protected precursor L1 has also been isolated and characterized, including by X-ray structural analysis. The protonation constants of L2 were determined by potentiometric methods at 25.0 °C and 0.10 mol dm⁻³ KNO₃ ionic strength. ¹³C NMR studies and 2D NMR spectra recorded at different pD values have been used to analyse its protonation scheme. Stability constants of L2 with Cu²⁺, Zn²⁺ and Cd²⁺ were also determined by potentiometry, and the Zn(II) and Cu(II) complexes were studied in solution by NMR, UV–Vis, and EPR spectroscopies. The pM values (pH 7.4) calculated for the metal complexes of L2 are higher than the corresponding values found for cyclen and cyclam, but the selectivity of L2 for Cu²⁺ is low.     

Karl Fischer titration at elevated temperatures

The determination of the water content is one of the most frequent analyses. This is particularly true in the field of foodstuffs, where the water content influences many technological, physical, microbiological and sensory properties and is important for the shelf life, logistic and legal aspects.Although drying methods (above all oven drying, also in infrared or microwave dryers) are the most commonly used technique, they can principally not yield the water content as result. On the one hand strongly bound water may not be detected. On the other hand not only water is driven out by the process, but all the substances volatile under the drying conditions, even those produced by the process itself. So these results are a question of definition, because they depend on the employed conditions. For nearly no foodstuff a really stable mass in the course of a drying process can be obtained.The by far most widespread procedure to determine the true water content is Karl Fischer titration which is based on a specific chemical reaction. It may also serve to calibrate indirect methods like nuclear magnetic resonance spectroscopy, near infrared spectroscopy or microwave techniques.In some cases a problem may arise because the water must get in direct contact with the reagents. We dispose, however, of several measures to provide for a liberation of practically all the water contained in samples that are not soluble in the working medium. One of these measures is the titration at elevated temperatures. The positive effect of this parameter (also in combination with others) is shown for several examples of foodstuffs.     

异丙基膦酸单(1-已基-4-乙基)辛酯的某些基本常数的测定

用两相滴定法测定异丙基膦酸单（１－己基－４－乙基）辛酯（ＰＴ－２，ＨＬ）在水中的溶解度Ｓ，在水中的解离常数Ｋ在水－正庚烷中的分配常数Ｋｄ及二聚常数Ｋ２，利用ＳＯＬＷＲ计算程序，简单快速地处理两相滴定数据，得到结果为：Ｓ＝３．６８ × １０－５ｍｏｌ／Ｌ，ｐＫａ＝５．４９，ｌｏｇ Ｋ２＝４． ６７，ＩｏｇＫｄ＝ ２． ６７（２５±０． ５℃）．     

自动电位滴定快速测定84消毒液中的有效氯含量

During the outbreak of novel coronavirus pneumonia, 84 Disinfectant has been widely used. It is very important to determine the available chlorine content in 84 Disinfectant. A new method to rapidly determine the available chlorine content in 84 Disinfectant by automatic potentiometric titration was established. Statistically, there is no significant difference in results between automatic potentiometric titration and manual titration. Combined the principles of analytical chemistry and the application to the determination of anti-epidemic material, this experiment has theoretical and practical significance, and can be used as an experiment in analytical chemistry laboratory for sophomore students.