Conversion of Parameters Among Variants of Scatchard’s Neutral-Electrolyte Model for Electrolyte Mixtures that Have Different Numbers of Mixing Terms

Various model equations are available for representing the excess Gibbs energy properties (osmotic and activity coefficients) of aqueous and other liquid mixed-electrolyte solutions. Scatchard’s neutral-electrolyte model is among the simplest of these equations for ternary systems and contains terms that represent both symmetrical and asymmetrical deviations from ideal mixing behavior when two single-electrolyte solutions are mixed in different proportions at constant ionic strengths. The usual form of this model allows from zero to six mixing parameters. In this report we present an analytical method for transforming the mixing parameters of neutral-electrolyte-type models with larger numbers of mixing parameters directly to those of models with fewer mixing parameters, without recourse to the source data used for evaluation of the original model parameters. The equations for this parameter conversion are based on an extension to ternary systems of the methodology of Rard and Wijesinghe (J. Chem. Thermodyn. 35:439–473, 2003) and Wijesinghe and Rard (J. Chem. Thermodyn. 37:1196–1218, 2005) that was applied by them to binary systems. It was found that the use of this approach with a constant ionic-strength cutoff of I≤6.2 mol⋅kg⁻¹ (the NaCl solubility limit) yielded parameters for the NaCl+SrCl₂+H₂O and NaCl+MgCl₂+H₂O systems that predicted osmotic coefficients φ in excellent agreement with those calculated using the same sets of parameters whose values were evaluated directly from the source data by least-squares, with root-mean-square differences of RMSE(φ)=0.00006 to 0.00062 for the first system and RMSE(φ)=0.00014 to 0.00042 for the second. If, however, the directly evaluated parameters were based on experimental data where the ionic strength cutoff varied with the ionic-strength fraction, i.e., because they were constrained by isopiestic ionic strengths (MgCl₂+MgSO₄+H₂O) or solubility/oversaturation ionic strengths (NaCl+SrCl₂+H₂O and NaCl+MgCl₂+H₂O), then parameters converted by this approach assuming a constant ionic-strength cutoff yield RMSE(φ) differences about an order of magnitude larger than the previous case. This indicates that for an accurate conversion of model parameters when the source model is constrained with variable ionic strength cutoffs, an extension of the parameter conversion method described herein will be required. However, when the source model parameters are evaluated at a constant ionic strength cuttoff, such as when source isopiestic data are restricted to ionic strengths at or below the solubility limit of the less soluble component, or are Emf measurements that are commonly made at constant ionic strengths, then our method yields accurate converted models. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

在电解质溶液中测定非电解质溶解度的新方法

提出了一种可以同时测定电解质溶液中非电解质的溶解度和饱和溶液水活度的新方法。该法把等压平衡与传统化学分析统一起来,其优点是：（1）将多元饱和溶液中非电解质溶解度的测定转变为共存离子的溶度测定,避开了对非电解质难于进行精确化学分析的难题;（2）可以同时确定所测饱和体系的水活度。用该法测定了NaCl和KCl溶液中甘露醇的溶解度并与文献值进行了比较,结果表明二者符合得很好。     

聚吡咯微粒掺入的聚苯乙烯膜在电解质溶液中的介电弛豫谱及其解析

在40 Hz～11 MHz频率范围测量了聚苯乙烯膜以及混入聚吡咯粒子的聚苯乙烯膜和电解质溶液构成的体系的介电谱, 发现了特异的弛豫现象: 纯的和掺入导电性聚吡咯后的聚苯乙烯膜分别显示出单一弛豫和双弛豫的不同模式的介电谱. 在Maxwell-Wagner界面极化概念基础上解释了该弛豫机制: 高、低频弛豫分别由膜-液界面极化和膜相本身的不均一性引起的. 将体系进行了模型化, 并利用Hanai理论方法对谱进行了解析, 获得了内部电性质的诸多参数. 对不同聚吡咯掺入量的膜/溶液体系的介电测量和解析结果表明, 电解质溶液的种类、浓度以及膜中混入聚吡咯的量都影响着膜相的介电响应. 这些结论为利用加入导电粒子改善绝缘高分子聚合物的电性质的研究以及制备既具有导电功能又使基体的力学性能得到提高的高分子复合物提供了重要的线索.     

湿化学法合成钙钛矿结构中温电解质La0.8Sr0.2Ga0.85Mg0.15O3-δ及其性能研究

以尿素-硝酸盐为前驱体合成了具有钙钛矿结构的中温电解质La0.8Sr0.2Ga0.85Mg0.15O3-?(LSGM)。用DTA-TG和XRD分析了样品中钙钛矿相的形成过程。用热膨胀仪确定了LSGM的烧结温度及热膨胀系数。用交流阻抗谱研究了所获得LSGM样品的电学性能。研究结果表明：用尿素-硝酸盐合成LSGM的成相温度为1300， 1500 ℃烧结6 h可获得单相的LSGM样品。用尿素-硝酸盐合成LSGM样品的烧成温度为1485 ℃，明显低于固相法合成LSGM的烧成温度。 1500 ℃烧结6 h的LSGM样品在850 ℃时的电导率为5×10-2 S·cm-1，高于同温下钇稳定化氧化锆(YSZ)样品的电导率，表明LSGM更适合做中温SOFC的电解质材料。在30～1000 ℃的温度范围内， LSGM的膨胀系数为12.8×10-6 ℃-1。     

标准加入法在酸碱分析中的应用

本文推导了单元酸标准加入法的线性公式。在被测酸溶液中,等量加入同种酸的标准溶液多次,并记录pH值,代入线性公式计算后即可得一直线,该直线在纵轴上的截距为被测酸浓度,斜率为该酸的条件稳定常数。本文还对单元酸及其共轭碱的标准加入法同时测定进行了研究。     

Validated Enantioselective LC Method, with Precolumn Derivatization with Marfey’s Reagent, for Analysis of the Antiepileptic Drug Pregabalin in Bulk Drug Samples

An enantioselective high-performance liquid chromatographic method, with precolumn derivatization with Marfey’s chiral reagent, sodium 2,4-dinitro-5-fluorophenyl-l-alanine amide, has been developed for resolution of the enantiomers of a new antiepileptic drug, pregabalin, in the bulk drug. The diastereomers of the pregabalin enantiomers were resolved to baseline on a reversed-phase ODS column with a 60:40 (v/v) mixture of aqueous 0.2% triethylamine (pH adjusted to 3.5 with dilute orthophosphoric acid) and acetonitrile as mobile phase. Resolution between the diastereomers was not less than five. The method was extensively validated and proved to be robust. The calibration plot was indicative of an excellent linear relationship between response and concentration over the range 750 (LOQ) to 7,500 ng L⁻¹ for the R enantiomer. The limits of detection and quantification of the R enantiomer were 250 and 750 ng L⁻¹, respectively, for an injection volume of 10 μL. Recovery of the R enantiomer from bulk drug samples of pregabalin ranged from 97.5 to 101.76%. Solutions of pregabalin in water and in the mobile phase were found to be stable for at least 48 h. The method was found to be suitable and accurate for quantitative determination of the R enantiomer in the bulk drug. It can be also used to test the stability of samples of pregabalin.     

New Rapid Validated HPTLC Method for the Determination of Lycorine in Amaryllidaceae Plants Extracts

A rapid, accurate, specific, repeatable and robust HPTLC method for the determination of lycorine in different Amaryllidaceae plant extracts is presented in this work. No article related to the HPTLC determination of lycorine in plant extracts has been reported in literature. Lycorine, a common alkaloid of family Amaryllidaceae, moreover, there have been some recent reports which reveal the interaction of lycorine with DNA and tRNA. It has, therefore, been to the interest of phytochemists to determine the content of this alkaloid in Amaryllidaceaous plants.     

偏最小二乘法用于铽、钍、铒的同时测定

偏最小二乘法用于紫外可见光度分析测定多组分间相互作用较显著的铽、钍、铒稀土体系得到较好的结果.考查了波长和间隔选取对计算精度的影响,与卡尔曼滤波法对比,证明了本法的优越性和广泛适用性.     

Dislocation Analysis for Large-sized Sapphire Single Crystal Grown by SAPMAC Method

In this paper,large-sized sapphire (230×210 mm,27.5 kg) was grown by SAPMAC method (sapphire growth technique with micro-pulling and shoulder-expanding at the cooled center). Dislocation peculiarity in large sapphire boule (0001) basal plane was investigated by chemical etching,scanning electron microscopy and X-ray topography method. The triangular dislocation etch pit measured is 7.6×101～8.0×102 cm-2,in which relative high-density dislocations were generated at both initial and final stages of crystal growth. The analysis of single-crystal X-ray topography shows that there are no apparent sub-grain boundaries; the dislocation lines are isolated and straight. Finally,the origins of low-density dislocation in sapphire crystal are discussed by numerical analysis method.     

酶抑制法农药残留快速测定仪灵敏度的校准

用农药残留测定仪在波长412 nm处测定农药吸光度的变化值,根据酶抑制法计算抑制率,抑制率与农药浓度呈正相关。用农药标准物质从低于规定的农药检测下限开始配制一系列标准溶液对仪器进行校准,在抑制率为50%处的浓度即为仪器的灵敏度。对影响校准结果的因素进行分析,该方法校准结果的相对扩展不确定度为4%。     

A Simple Novel Method for the Analysis of Lubricating Oil Additives by the Use of Sep-Pak Cartridges

In combination with the use of SEP-PAK cartridges and computerized difference infrared spectroscopic technique, a simple novel method for analyzing lubricating oil additives was developed. The present method involves solvent extraction and the use of SEP-PAK C₁₈ for separating polar additives from residual base oil, followed by the use of SEP-PAK Silica for further elution. With the aid of infrared data station, components of the polar additives were identified. The present method is definitely much more rapid and efficient than the conventional column separation method, and the separation efficiency of this simple method is comparable to that of using flash chromatographic technique.     

Two new graph-theoretical methods for generation of eigenvectors of chemical graphs

Two new graph-theoretical methods, (A) and (B), have been devised for generation of eigenvectors of weighted and unweighted chemical graphs. Both the methods show that not only eigenvalues but also eigenvectors have full combinatorial (graph-theoretical) content. Method (A) expresses eigenvector components in terms of Ulam’s subgraphs of the graph. For degenerate eigenvalues this method fails, but still the expressions developed yield a method for predicting the multiplicities of degenerate eigenvalues in the graph-spectrum. Some well-known results about complete graphs (K _n) and annulenes (C _n ), viz. (i)K _n has an eigenvalue −1 with (n−1)-fold degeneracy and (ii) C _n cannot show more than two-fold degeneracy, can be proved very easily by employing the eigenvector expression developed in method (A). Method (B) expresses the eigenvectors as analytic functions of the eigenvalues using the cofactor approach. This method also fails in the case of degenerate eigenvalues but can be utilised successfully in case of accidental degeneracies by using symmetry-adapted linear combinations. Method (B) has been applied to analyse the trend in charge-transfer absorption maxima of the some molecular complexes and the hyperconjugative HMO parameters of the methyl group have been obtained from this trend.     

毛细管色谱切割-反吹法归一化分析汽油中芳烃

发展了一种毛细管色谱切割 反吹方法分析汽油中的芳烃。利用OV 2 3 3 0强极性毛细管预柱将芳烃保留至n C1 0 之后 ,并反吹到非极性毛细管柱中按沸点详细分离分析。从预柱先流出的组分和从分析柱流出的组分都先后进入同一检测器中 ,因此可用响应因子校正的归一化方法定量分析汽油中的芳烃。该方法在15min内完成汽油中苯至C1 0 芳烃的分析 ,结果的重复精度误差≤ 3 % (RSD) ,切割误差± 5s时对分析结果的影响≤ 4% (RSD)。对该方法的装置和部分应用进行了讨论     

Succinonitrile Activated by Thiating Agents as Precursor of Bis-cyclic Amidines, Tectons for Molecular Engineering

Summary. Modification of the thio-Pinner’s method via in situ activation of a nitrile by thiating agents, S₈, P₄S₁₀, Lawesson reagent, or Na₂S·9H₂O, was applied in the syntheses of bis(4,5-dihydro-1H-imidazol-2-yl)alkanes and bis(1,4,5,6-tetrahydropyrimidin-2-yl)alkanes.