水中总硬度与碳酸盐和非碳酸盐硬度的测定

文献 [1 ,2 ]介绍 ,水中总硬度用 EDTA法测定钙和镁的总量 ,用中和法测定 HCO-3 来换算碳酸盐硬度 ,两者之差为非碳酸盐硬度。常出现碳酸盐硬度等于甚至高于总硬度值的现象 ,为此硬性规定当总硬度值比碳酸盐硬度值大时 ,总硬度是碳酸盐硬度与非碳酸盐硬度之和 ;若总硬度值等于或小于碳酸盐硬度时 ,只存在碳酸盐硬度而无非碳酸盐硬度。然而 ,上述的做法与规定在理论上是错误的 ,根本不代表实际情况 ,因为中和反应并非 HCO-3 的专一反应 ,而凡是在此滴定条件下能与酸发生中和反应的所有物质都干扰测定 ,产生正误差 ,见表中试验数据。本文…     

水质硬度测定仪的研制及应用

研制了一种便携式硬度测定仪，仪器检出限为０．２μｍｏｌ／Ｌ，，特别适用于锅炉罗化水等超低硬度水样的快速测定。     

A^NB^8—N晶体中的化学键参数与硬度的关系

物质的硬度作为一个物理量已被广泛运用于各种研究领域。硬度测量在各种机械试验法中是最迅速、最经济的一种方法,而且材料硬度值与其它机械性能有一些相当精确的相应关系。有关硬度的各种测试方法已发展相当完善。同时,人们对硬度的微观机制也曾作了许多     

异质富勒烯C58P2的理论研究

用ＭＮＤＯ半径能方法研究了异质富勒烯Ｃ５８Ｐ２各异构体的结构和相对稳定性。结果表明,１,４－位取代的异构体最稳定,异构体的稳定性随杂原子同距离的增加而降低。Ｃ５５８Ｐ２分子和稳定性比全碳富勒烯Ｃ６０低,但仍具有相当的稳定性,是潜在的合成目标。杂原子磷的掺杂改善了富勒烯的氧化还原性能。考察了各异构体的整体硬度和绝对电负性,产根据绝对电负性的差异预测了富勒烯和异质富勒烯间形成聚合物时的电子转移。     

一种新型水硬度测定的进样装置

报道一种新型水硬度测定的进样装置，它是特殊的直接进样－混合－混合－排液系统，勿需预先显色，可直接进样测定。实验表明具有操作简便，快速的优点。     

石灰法处理纳米膜过滤浓缩水

纳米膜过滤技术可用于处理高硬度地下水,但过滤后的浓缩水硬度很大,需软化处理才能排放.利用石灰法处理硬度为 1 750mg/L的纳米膜过滤浓缩水,选择倒锥形反应罐,合理控制CaO加入量和水流量,处理后的水硬度小于 600mg/L.     

软水与硬水区别

水分为软水、硬水，凡不含或含有少量钙、镁离子的水称为软水，反之称为硬水。水的硬度成分，如果是由碳酸氢钙或碳酸氢镁引起的，系暂时性硬水（煮沸暂时性硬水，分解的碳酸氢钙，生成的不溶性碳酸盐而沉淀，水由硬水变成软水）；如果是由含有钙、镁的硫酸盐或氯化物引起的，系永久性硬水。依照水的总硬度值大致划分，总硬度为0～30mg／L称为软水，总硬度在60mg／L以上称为硬水，高品质的饮用水不超过25mg／L，高品质的软水总硬度在10mg／L以下。在天然水中，远离城市未受污染的雨水、雪水属于软水；泉水、溪水、江河水、水库水，多属于暂时性硬水，部分地下水属于高硬度水。     

免疫毒素LHRH-PE40对HeLa细胞表面硬度的影响

利用基于原子力显微镜(AFM)的力谱技术,在正常生长的单个活细胞表面上,实时动态地研究了免疫毒素LHRH-PE40对HeLa细胞表面硬度的影响。采用Hertz-Sneddon模型计算所得力曲线相应的杨氏模量。实验表明,LHRH-PE40会引发HeLa细胞表面硬度逐步增加,且这种硬度的增加与细胞内微丝骨架的重组聚集有关系。本研究为全面掌握LHRH-PE40的药用效果和作用机理提供了重要信息。     

一种新型多元共聚含氟丙烯酸树脂的制备及性能研究

以含氟丙烯酸酯与几种不同结构丙烯酸酯单体为原料,采用常规的自由基引发溶液聚合反应,制备了一种新型疏水低表面能丙烯酸树脂。并以水接触角和铅笔硬度两项指标考察其应用性能。经固化成膜后,聚合物膜与水的接触角达到118.5°,铅笔硬度达到F等级以上。系统研究了涂膜与水接触角和铅笔硬度的主要影响因素,可通过调节单体投料比来调控接触角和铅笔硬度来适应不同实际应用领域的技术指标需求。这种具有力学强度的疏水涂层具有很大的应用价值。     

用Cu—PAR间接指示剂测定工业用水总硬度

自50年代以来,测定水的总硬度通常采用络黑T(EBT)指示剂,在氨性缓冲溶液中用EDTA标准溶液滴定水中的钙镁总量.标定EDTA溶液则使用基准物质碳酸钙.由于Ca~(2+)对EBT显色的灵敏度低,故标定时通常采用K-B指示剂.试验证明,测定时用EBT作指示剂,标定时用K-B指示剂,两者变色点不同,会产生方法误差.为此,有人提出在EDTA溶液中加入少量镁盐(或标定时加入适量Mg-EDTA),这样在标定时也可使用EBT作指示剂,从而提高了测定的准确度.但EBT溶液不稳定,容易失效,配成固体试剂虽然稳定,但指示剂的用量不便掌握.K-B指示剂也不够稳定.为此,本法探索用Cu-PAR间接指示剂法测定水的总硬度.4-(2-吡啶偶氮)-间苯二酚(PAR)溶液稳定,此测定方法变色敏锐,测定结果也较满意.     

Determination of structures, stabilities, and electronic properties for bimetallic cesium-doped gold clusters: a density functional theory study

The equilibrium geometric structures, stabilities, and electronic properties of bimetallic Au(n)Cs (n = 1-10) and pure gold Au(n) (n ≤ 11) clusters have been systematically investigated by using density functional theory with meta-generalized gradient approximation. The optimized geometries show that one Au atom capped on Au(n-1)Cs structures and Cs atom capped Au(n) structures for different sized Au(n)Cs (n = 1-10) clusters are two dominant growth patterns. Theoretical calculated results indicate that the most stable isomers have three-dimensional structures at n = 4 and 6-10. Averaged atomic binding energies, fragmentation energies, and second-order difference of energies exhibit a pronounced even-odd alternations phenomenon. The same even-odd alternations are found in the highest occupied-lowest unoccupied molecular orbital gaps, vertical ionization potential, vertical electron affinity, and hardnesses. In addition, it is found that the charge in corresponding Au(n)Cs clusters transfers from the Cs atom to the Au(n) host in the range of 0.851-1.036 electrons.     

Hard ormosils prepared with ultrasonic irradiation

Organically modified silicates (ormosils) of high hardness were prepared by the reaction of TEOS (tetraethoxysilane) and PDMS (polydimethylsiloxane) aided by ultrasonic irradiation, which was chosen as the method for concentration of the solutions. The mechanisms leading to the hard ormosil formation were examined by liquid state ²⁹Si NMR spectroscopy. PDMS chains were found to be broken into shorter chains and/or cyclic D₄ tetramers during the reaction and finally, all the PDMS chains were chemically incorporated as short chains into silica networks. Structural models of the mechanisms are also proposed. Elastic moduli and Vickers hardnesses of the hard ormosils were measured. Vickers hardnesses of the hard ormosils were compared with those of some glasses and the hardest transparent plastics and the hard ormosils were much harder than the plastics and a little softer than soft glasses. Theoretical models have been developed for the calculations of the elastic moduli and Vickers hardnesses and agreed well with the experimental results. Predictions based on these models indicate that even higher elastic moduli and Vickers hardnesses of the hard ormosils can be obtained when Al₂O₃, ZrO₂ and TiO₂ are substituted for SiO₂. 30 mol% TiO₂-containing ormosils of high hardness were also prepared aided by ultrasonic irradiation. TEOS and tetraisopropyltitanate (TIPT) were used as the inorganic components. Dimethyldiethoxysilane (DMDES) was used instead of PDMS as the organic precursor. The reactions among alkoxides were examined by liquid state ²⁹Si NMR spectroscopy. While the reactivity between TIPT and PDMS was much lower than the reactivity between TIPT and hydrolyzed TEOS, the reactivity between TIPT and hydrolyzed DMDES was not so different from the reactivity between TIPT and hydrolyzed TEOS, and thus DMDES was used as the organic precursor instead of PDMS. Elastic moduli and Vickers hardnesses of the hard ormosils of the TEOS/TIPT/DMDES system were measured and even higher elastic moduli and Vickers hardnesses than those of the TEOS/PDMS system hard ormosils were obtained. Also, the calculated results from the theoretical models agreed well with the experimental results.     

Empirical evaluation of chemical hardness

Two possible measures of hardness are proposed. An average chemical hardness is calculated separately for acidic and basic reactions of atoms. Differential hardnesses are derived from atomic radii.     

Equilibrium geometries, stabilities, and electronic properties of the bimetallic M2-doped Au(n) (M = Ag, Cu; n = 1-10) clusters: comparison with pure gold clusters

The density functional method with relativistic effective core potential has been employed to investigate systematically the geometrical structures, relative stabilities, growth-pattern behaviors, and electronic properties of small bimetallic M(2)Au(n) (M = Ag, Cu; n = 1-10) and pure gold Au(n) (n ≤ 12) clusters. The optimized geometries reveal that M(2) substituted Au(n+2) clusters and one Au atom capped M(2)Au(n-1) structures are dominant growth patterns of the stable alloyed M(2)Au(n) clusters. The calculated averaged atomic binding energies, fragmentation energies, and the second-order difference of energies as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The analytic results exhibit that the planar structure Ag(2)Au(4) and Cu(2)Au(2) isomers are the most stable geometries of Ag(2)Au(n) and Cu(2)Au(n) clusters, respectively. In addition, the HOMO-LUMO gaps, charge transfers, chemical hardnesses and polarizabilities have been analyzed and compared further.     

富勒烯和富勒烯衍生物中的Stone-Wales旋转

Stone-Wales旋转是富勒烯异构化的基本方式,了解其特征和规律对于理解富勒烯和富勒烯衍生物的形成至关重要.本文采用密度泛函理论方法系统研究了富勒烯和富勒烯衍生物的Stone-Wales旋转.结果显示,富勒烯异构体趋向于从高B55键(两个五元环共用的边)结构向低B55结构转化,满足独立五元环原则的结构或具有低B55键数的异构体在热力学上更为有利.相反,对于富勒烯衍生物,具有更多B55的异构体不仅在热力学上更有利,而且从动力学角度讲,从满足独立五元环原则的结构向不满足的结构的转变比相反过程更容易.这些结果可以解释目前的相关实验事实,暗示了富勒烯衍生物可能是先衍生化后异构化而形成.     

Tautomerism and the maximum hardness principle

Through the application of the atom–bond electronegativity equalization method (ABEEM) to the calculation of the hardnesses of more than 300 tautomers, it can be seen that the maximum hardness principle is nearly useless to account for their relative stabilities. Moreover, by calculating the energies of these tautomers with the HF, B3LYP, B3PW91, and MP2 methods at the 6‐31G, 6‐31G*, 6‐31G**, 6‐31+G**, 6‐311G**, or 6‐311++G** level, it is found that all these methods may not be always reliable in predicting their relative stabilities. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Stereochemistry of heterocycles

2-Methyl-and 2,5-dialkyl-5-phenoxy-1,3-dioxanes were synthesized and separated into their geometrical isomers by precision rectification. The configuration and conformations of these isomers were determined by PMR spectroscopy. It is shown that the low-boiling trans isomers exist primarily in the chair conformation with an equatorial phenoxy group, whereas the high-boiling cis isomers exist primarily in the chair conformation with an axial phenoxy group.     

有机异构体的质谱分析简介

本文介绍了用于有机异构体辨析的几种质谱方法，并综述了它们在五类异构体中的应用。     

Simultaneous determination of total, non-carbonate and carbonate water hardnesses by direct potentiometry

Total, non-carbonate and carbonate water hardness have been determined simultaneously by manual and automated direct potentiometry, using the bivalent ion-selective electrode, and known addition-known dilution technique. The automated and programmable system produces direct print-out of total, non-carbonate and carbonate water hardnesses. The optimum sampling rate is 20 samples per hour. This time-saving method compares well with the standard method.     

Separation of isomers of dienoic acids by electromigration techniques

Different capillary electromigration techniques were employed to resolve geometrical isomers of sorbic acid, decadienoic acid, and ethyl sorbate. Since these substances differ in their polarity, shape, and size, various electromigration approaches were investigated to separate the four geometrical isomers of each compound. With capillary electrophoresis (CE) modified with a cyclodextrin (β‐CD) the four isomers of sorbic acid were separated using a buffer that consists of 60 mM tetraborate and 8 mg/mL β‐CD. The separation of decadienoic acid geometrical isomers was not possible, even at elevated tetraborate and cyclodextrin concentrations. The four isomers of decadienoic acid were successfully separated using micellar electrokinetic chromatography (MEKC) with a buffer consisting of 30 mM tetraborate and 100 mM SDS and microemulsion electrokinetic chromatography (MEEKC). Ethyl sorbate is the least polar of all the studied substances and its isomers could not be separated by MEKC or MEEKC. The resolution was improved and isomers were fully separated using capillary electrochromatography (CEC) with ODS stationary phase and a mobile phase consisting of 10 mM boric acid in 50% acetonitrile. Minor differences in the polarity and the shape of isomers and high resolving power of the applied techniques were sufficient for separation of very similar compounds. We have shown that versatile electromigration techniques can be applied for separation of geometrical isomers of dienoic acids and their esters.