Conductimetric determination of ion-association constants for calcium,cobalt, zinc,and cadmium sulfates in aqueous solutions at various temperatures between 0°C and 45°C

Thermodynamic ion-association constants for calcium, cobalt, zinc, and cadmium sulfates in aqueous solutions were determined by means of conductivity measurements at various temperatures between 0°C and 45°C. The standard Gibbs energy, enthalpy, and entropy for the reaction M ²⁺ +SO ₄ ^2– M ²⁺ ·SO ₄ ^2– (M=Ca, Co, Zn, and Cd) were calculated from the temperature dependence of the ion-association constants. The values obtained are as follows: G ₂₉₈ ^o =–12.42 kJ-mole ^–1 , H ^o =6.11 kJ-mole ^–1 , and S ₂₉₈ ^o =62.1 J- ^o K ^–1 -mole ^–1 for Ca ²⁺ ·SO ₄ ^2– ; G ₂₉₈ ^o =–12.84 kJ-mole ^–1 , H ^o =5.00 kJ-mole ^–1 , and S ₂₉₈ ^o =59.8 J- ^o K ^–1 -mole^–1 for Co ²⁺ ·SO ₄ ^2– ; G ₂₉₈ ^o =–12.65 kJ-mole ^–1 , H ^o =8.65 kJ-mole ^–1 , and S ₂₉₈ ^o =71.4 J- ^o K ^–1 -mole ^–1 for Zn ²⁺ ·SO ₄ ^2– ; G ₂₉₈ ^o =–13.28 kJ-mole ^–1 , H ^o =8.39 kJ-mole ^–1 , and S ₂₉₈ ^o =72.7 J- ^o K ^–1 -mole ^–1 for Cd ²⁺ ·SO ₄ ^2– .     

几种二醇与非质子溶剂相互作用的红外光谱研究

测定了1，2-乙二醇、1，2-丙二醇、1，4-丁二醇和1，6-己二醇在CCl4中分别与十几种非质子溶剂相互作用的红外光谱，通过考察频率位移的变化，定量地研究了二醇分子内氢键与分子间氢键的协同效应．在四氯化碳介质中，乙二醇、1，2-丙二醇和1，4-丁二醇体系中存在明显的氢键协同效应。利用红外光谱数据，估算了常温下二醇分子内缔体与非质子溶剂的交叉缔合常数，其数值大于一元正链醇与相应溶剂的交叉缔合常数．     

Rare variants analysis by risk-based variable-threshold method

Genome-wide association studies, as a powerful approach for detecting common variants associated with diseases, have revealed many disease-associated loci. However, the traditional association analysis methods do not have enough power for detecting the effects of rare variants with limited sample size. As a solution to this problem, pooling rare variants by their functions into a composite variant provides an alternative way for identifying susceptible genes. In this paper, we propose a new pooling method to test the variant–disease association and to identify the functional rare variants related with the disease. Variants with smaller and larger risk measures defined as the ratio of allele frequencies between cases and controls are pooled and a chi-square test of the resultant pooled table is calculated. We vary the threshold of pooling over all possible values and use the maximal chi-square as test statistic. The maximal chi-square is in fact the global maximum over all possible poolings. Our approach is similar to the existing variable-threshold method, but we threshold on the risk measure instead of allele frequencies of controls. Simulation results show that our method performs better in both association testing and variant selection.     

极性气体的第二维里系数及缔合平衡常数和缔合焓方程

本文根据对一些极性气体分子聚集现象的分析,推导出计算极性气体的缔合平衡常数和缔合焓方程.还改进了描述低压下的极性气体PVT行为的简单舍项式维里方程.上述诸方程经计算检验,结果满意.     

Activity coefficients of non-electrolyte liquid binary systems under pressure

Abstract

The pressure dependence of the activity coefficients in seven binary non-electrolyte mixtures is calculated. Experimental PVT data for pure components and mixtures are interpolated to give the molar volumes at specific pressures. The partial molar volume along isobars is calculated as a function of composition and the excess partial molar volume is integrated numerically along constant composition lines. The adequacy of the calculations is discussed. The results obtained on all systems are physically reasonable and consistent with thermedynamic data at 1 atm., and the Gibbs-Duhem equation has been used to show that they are mathematically (as distinct from thermodynamically) consistent. The effect of pressure is found to vary: systems may become more or less ideal or the activity coefficients may be unaltered with increasing pressure. Possible sources of the difference in the pressure dependence of the systems are discussed briefly.     

Phosphoric acid solutions. I: Molecular association in a 57.8 molal aqueous solution

A 57.8 molal solution of orthophosphoric acid (85% w/w) has been studied by the wide angle X-ray scattering method. Both the ARDF and the intensity curve are consistent with a hydrogen-bonded ring structure for the dimeric (H₃PO₄)₂.     

硼酸盐水溶液热力学研究: 4.离子对[CaB(OH)~4]^+标准缔合 常数的确定

在温度为278.15-318.15K范围内测定了含有不同Li~2B~4O~7和CaCl~2浓度测试液的无液接电池:Pt,H~2(101.325kPa)|Li~2B~4O~7(m~1),CaCl~2(m~2)|AgCl-Ag的电动势E(V)。在Pitzer电解质溶液理论基础上,用线性外推法确定离子对[CaB(OH)~4]^+的标准缔合常数K~d,并得到K~d随温度T变化的经验公式:pK~d=0.6857-359.72/T-4.632×10^-^3T。同时计算得到了离子对缔合过程的热力学函数,指出形成该离子对的推动力是缔合熵。     

A Density Functional Theory Study of the Hydrates of 2NH_3:H_2SO_4 and Its Implications for the Formation of Atmosphere Particles

Density functional theory was used at the B3LYP/6-311++G(d,p) level of theory to study the hydrates of 2NH3:H2SO4:nH2O for n = 0～4. Neutrals of the most stable clusters, when n = 0 and 1, spontaneously formed and were determined to be hydrogen-bonded molecular complexes of monomeric species. Double ions (clusters containing a NH4+ cation and a HSO4- anion) or even ternary ions (clusters with two NH4+ cations and one SO42- anion) spontaneously formed in the most stable clusters of 2NH3:H2SO4:nH2O (n = 2, 3, 4). The energetics of binding and incremental association was also calculated. Double ions are not energetically favorable until 2NH3:H2SO4:2H2O because of the about equal free energies for forming the neutral (the most stable) and double ion (the second stable) isomers. The free energy of incremental association from free H2O and 2NH3:H2SO4:nH2O has a maximum at n = 2 at room temperature with ΔG ≈ -2 kcal/mol. The comparison of incremental association energies between 2NH3:H2SO4:nH2O, NH3:H2SO4:nH2O and H2SO4:nH2O clusters revealed that NH3 plays an important role in the atmospheric particle nucleation.     

Thermodynamic study of the β-cyclodextrin benzyl-2-pyridyl ketone 2-pyridyl hydrazone inclusion process

Benzyl-2-pyridylketone-2-pyridylhydrazone and -cyclodextrin form a 1 : 1 adduct in water with a standard free energy change, G ^o, in the region of 14.2 kJ mol^–1 at 25°C, and an association constant of 275 M^–1 in the pH range 5–7. These values have been obtained by using the fluorimetric spectral changes associated with the inclusion process.     

On the properties of surfactant aqueous solutions

Summary From studies of aqueous solutions of dodecylammoniumnitrate an association mechanism has been proposed involving multiequilibrium. In the concentration range considered we can differentiate between two aspects: ranges of marked qualitative and quantitative changes and formation of differently structured surfactant species.

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Zusammenfassung Aus der Untersuchung wäßriger Lösungen von Dodecylammoniumnitrat würde ein Assoziationsmechanismus abgeleitet, welcher ein Multiequilibrium beinhaltet. Im untersuchten Konzentrationsbereich können zwei Bereiche unterschieden werden: Bereiche mit ausgeprägten qualitativen und quantitativen Änderungen und Bereiche mit der Bildung von verschieden strukturierten oberflächenaktiven Spezies.

     

NMR Study of Hetero‐Association Accompanying Self‐Association of 2‐Hydroxyl‐4‐methyl‐pyridine and 2‐Pyrrolidone in Acetonitrile

This work in vestigated not only the equilibrium of self‐association of 2‐pyrrolidone (A) and that of 2‐hydroxyl‐4‐methyl‐pyridine (B), but also the hetero‐association between A and B in [²H₃]acetonitrile through hydrogen bonding using high‐resolution nuclear magnetic resonance spectroscopy. Dilution shift data for the protons of the NH group of A and OH group of B were measured over a wide range of temperatures and concentrations. In addition, the monomer shifts, dimer shifts and dimerization constants of self‐association and hetero‐association were evaluated using a graphic method operating on the dilution chemical shift data. The enthalpy and entropy of dimerization of self‐association and hetero‐association were also obtained from the van't Hoff plot.     

Ionic interactions in solutions. II. The theoretical basis of the equilibrium between free and pairwise associated ions

It is shown from recent results based on the statistical mechanics treatment of ionic solutions that the notion of an equilibrium between free ions and paired ions which wasa priori introduced in the chemical model of Bjerrum is essentially correct. The mass-action law which is deduced from such a model is indeed derivable from the more exact treatments of Mayer, Rasaiah, and Friedman starting directly from Hamiltonian models and without any assumptions as to the chemical structure of the ionic solute in the solution. The transformation relation from a primitive-model result to any short-range Hamiltonian model equation is given. It allows a simple mathematical treatment of experimental data for dilute solutions, the derivation of useful information on the Gurney solvation effects, and an interpretation of the multistep association concept.     

醇类的缔合作用与热压力系数

测定了甲醇、正丙醇、正丁醇和正癸醇在25-85℃温度范围的热压力系数, 并为正构醇液体建立了一个热压力系数与密度间的通式。这个通式可用来预测正构醇在各种温度下的内压值。用同形物近似法, 本文还获得了正构醇缔合作用的若干重要信息和估计其缔合度的近似方法。     

Effect of temperature on the molecular association in liquid D-methanol using neutron diffraction data

Hydrogen-bonded cluster analysis of liquid D-methanol data at room and elevated temperatures was carried out and nature of molecular association was extracted. The analysis, based on a choice of suitable centre structure corresponding to an effective pair potential, hardsphere plus a square-well ledge, determines if the H-bonded clusters are broken with the rise in temperature. It is shown that clusters present at room temperature are more or less preserved at elevated temperatures. At low Q (Q being the scattering vector), Ornstein–Zernike behaviour is produced extremely well. The analysis enables the extraction of atom–atom distribution functions, such as g _OO(r), g _OD(r) and g _DD(r), the variation of which with temperature confirm the same observation.     

Ion association and departure from additivity of equivalent conductance as a function of pressure

The equivalent conductance of mixtures of 0.01 equivalent/liter solutions of MgCl₂ and Na₂SO₄ were measured as a function of pressure at 25°C. Departures from additivity are used to infer the pressure dependence of the concentration of MgSO₄ ion pairs. The results are consistent with the pressure dependence of the molal dissociation constant of MgSO₄ obtained from pressure conductance studies on aqueous solutions of MgSO₄.     

Effects of solute-solvent and solvent-solvent association in liquid adsorption chromatography with binary mobile phase

Analytical equations for the capacity ratio in liquid adsorption chromatography with a binary mobile phase, involving solute-solvent and solvent-solvent association in the mobile and surface phases, have been derived. Very simple equations have been obtained for higher values of mole fraction of the more efficient eluting solvent.     

The structure‐dependent self‐association of five phenolic acids in aqueous solution

Weak self‐interaction plays an important role in interpreting the biomechanisms and modes of drug action. The structure‐dependent self‐association of five phenolic acids with various bioactivities, including danshensu (DSS), caffeic acid (CA), rosmarinic acid (RA), lithospermic acid (LA), and salvianolic acid B (SA), was investigated by ¹H NMR. These phenolic acids have similar condensed structures, with a CA moiety and varying numbers of DSS moieties. The strengths of the self‐association constants are in the order DSS < CA < RA < LA < SA, which corresponds to the increasing molecular size of these phenolic acids and roughly corresponds to the increasing number of DSS moieties. The binding site for the self‐aggregation of these phenolic acids has been identified to be on the CA moiety, rather than on the DSS moiety, as a result of CA's stronger aromatic π–π interactions, which cause larger chemical shift variations. The thermodynamic parameters for the self‐association of these phenolic acids show that the self‐association is spontaneous and enthalpically favorable at room temperature in all cases. It was inferred that π–π interactions and intermolecular hydrogen bonding stabilize the stacking structures of the phenolic acids. Knowledge of self‐association processes will enable us to quantitatively assess the possible effects of self‐aggregation on the interaction between drug and protein. Copyright © 2014 John Wiley & Sons, Ltd.     

离子缔合溶剂萃取分光光度法测定痕量铬

Ｃｒ（Ⅵ）氧化Ｉ－离子产生Ｉ－３配阴离子，在硫酸介质中，Ｉ－３与罗丹明Ｂ阳离子形成离子缔合物，该缔合物能被苯等有机溶剂萃取，建立了一种测定痕量铬的新方法．缔合物表观摩尔吸光系数ε＝２．１×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，铬量在１．０－１２．０ｎｇ／ｍＬ范围内符合比耳定律，本法应用于人发中痕量铬的测定，结果满意．     

Aggregation of nitrosubstituted spiropyranes in polymeric films

Absorption, luminescence, and luminescence polarization spectra of associates of photochronic molecules of nitrosubstituted indolinospiropyranes in the closed form in polymeric films at high temperatures were studied. The efficiency of the formation of the associates depends on the structure of the photochrome molecules and the nature of the polymeric matrix. A scheme of phototransformations of the associates taking into account the exciting light wavelength was suggested. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 946–949, May. 1997.