Acoustic Study of Solvent Coordination in the Hydration Shells of Potassium Iodide

The isentropic compressibilities of aqueous solutions of potassium iodide, from dilute to almost saturated, were determined at 288 to 308 K based on precise measurements of the speed of ultrasound. Using proper correlations, the hydration numbers (h) were calculated as well as the molar volume and compressibility parameters of the hydrated complexes (V _h , β _h V _h ) of water in the hydration shell (V _1h , β_1h V _1h), and of the cavity containing stochiometric mixtures of K⁺ and I⁻ ions (V _2h, β_2h V _2h). It is revealed that under the studied conditions, the obtained values of h and β _h V _h are independent of temperature whereas the molar compressibility of the hydration shell β _h V _h) is independent of concentration. The electrostatic field of the ions is shown to influence the temperature dependence of the molar volume of water in the hydration shell more substantially than a change of pressure alone influences the temperature dependence of the molar volume of pure water.     

Solvation of the Electrolytic Components of Seawater

A new modification of the adiabatic compressibility method of investigating solvation in solutions is presented and applied to the analysis of the following structurally-related characteristics of hydrated complexes of seawater electrolytes (NaCl, KCl, MgCl₂, CaCl₂, Na₂SO₄, MgSO₄) at different concentrations (0.1 to 5.0 mol⋅kg⁻¹) and temperatures (278.15 to 308.15 K): solvation numbers (h) and their dependences on concentration, volumes of stoichiometric mixtures of ions without their hydration shells (V _2h ), compressibilities (β _1h ) and molar volumes of water in their solvation shells (V _1h ), their dependences on concentration and temperature, etc.     

Definition of Hydration Parameters in the Region of Maximal Solvent Density

The approach to the definition of hydration numbers using the ultraacoustic method is critically discussed. Leaning upon a correct thermodynamic analysis, limited validity is shown of the main equation used in the publication of Onori over a wide range of state parameters. It is revealed that the mentioned equation is true only in the region of maximum solvent density. For this range of conditions, hydration numbers, the compressibility of hydration formations, molar volume and compressibility of water in hydration shells, molar volume and compressibility of stoichiometric mixtures of ions of NaCl are calculated based upon the experimental data of density and speed of ultrasound in solutions.     

MX—NX2和MX—NX3电解质水溶液的热力学研究

本文用Pitzer方程研究相同阴离子的非对称性混合电解质溶液的热力学性质,讨论了高次静电项(~Eθ_(ij)、~Eθ′_(ij))所产生的效应。引入混合参数(θ_(ij))和离子强度(Ⅰ)的关系式,估算了25℃时MX-NX_2和MX-NX_3电解质水溶液的Pitzer混合参数~Sθ_(ij)~(0)、~Sθ_(ij0~(1)和φ_(ij)k,其计算值和文献值吻合。     

用于聚合物溶液扩散系数计算的活度系数模型比较

用40个聚合物溶液体系的实验数据,对三个有代表性的活度系数模型用于计算联系自扩散系数和互扩散系数的热力学因子的精度进行了比较,结果表明三个模型的精度相近,误差一般在20％左右。,因而本工作揭示了聚合物溶注保由自扩散系数计算与扩散系数的一个潜在问题。即由于活度系数模型计算热力学因子误差较大所带来的较大不确定性。     

Density and compressibility measurements of a highly viscous polyelectrolyte solution: a study on aqueous solutions of sodium hyaluronate

The density of a highly viscous polyelectrolyte solution was measured using both pycnometers and oscillating-tube densimeters in parallel to elucidate the difficulties inevitably involved when an oscillating tube is employed for density measurements of viscous liquids. It was confirmed that the oscillating-tube densimeter gives too high values for viscous liquids, and the deviation increases with the increase in the viscosity of liquids. The analysis of adiabatic compressibilities of sodium hyaluronate (NaHy) solutions, as estimated from density and ultrasound velocity data of the same solution, suggests that the disaccharide unit of the NaHy chain is less hydrated than the sum of its component monosaccharide residues. Received: 2 September 1998 Accepted in revised form: 29 September 1998     

电解质溶液自扩散系数的布朗动力学模拟

采用布朗动力学方法对电解质溶液进行了模拟,在传统布朗动力学的基础上综合考虑了流体力学的影响,并且引入SmartMonteCarlo方法的接受概率,避免了离子不现实的移动和位型重叠,这样不仅可以将模拟过程中的时间步长大幅度提高,而且还可使溶质在相空间的演化过程更接近实际.模拟过程以电解质溶液的原始模型为基础,将溶剂看作连续介质,溶质分子之间的相互作用采用软核加静电的势能函数模型,长程静电力采用Ewald加和的处理方法.模拟得到KCl和NaCl溶液的径向分布函数g+-(r),g++(r)和g--(r),并与文献中HNC计算以及模拟的结果进行比较,使用推广的Green-Kubo公式模拟计算溶液中各种离子的自扩散性质,计算结果与实验数据吻合良好.     

无盐聚电解质溶液的分子热力学模型

聚电解质在水处理和胶体领域应用广泛 ,在生物系统中 ,蛋白质和 DNA等均是聚电解质 .文献中已发表了不少聚电解质溶液的理论和模型 ,如基于柱型胞腔模型的 Poison- Boltzmann( PB)方程理论[1]及其改进型 ( MPB) [2 ] 、Manning反离子凝聚理论 [3 ] 、积分方程理论 [4] 及适合于工程应用的半经验模型 [5 ]等 ,但离工程实际应用的要求还相差较远 .最近 ,姜建文等 [6]建立的分子热力学模型 ,其预测结果与 MD模拟数据非常吻合 .本文在此基础上进一步考虑聚离子与反离子间的缔合作用 ,可以在中高浓度范围内很好地关联实验数据 .1　模　　型…     

电解质对非离子型微乳液的影响

本文通过测定微乳液的电导率和相图,研究了电解质(硝酸镍)对非离子型微乳液Triton X-100/正己醇/环己烷/水或硝酸镍水溶液系统稳定性的影响.发现分散相为水的微乳液体系中,表面活性剂的含量越大微乳液的电导率越大;分散相为盐溶液的微乳液体系中,微乳液的电导率随着盐溶液浓度的增大而减小;而且盐溶液浓度越大微乳液的含水量越小.     

Conductance of Electrolyte Solutions

The present article deals with methods and results of conductance studies with special reference to nonaqueous solvents, e.g. ethanol, dioxane, dimethylformamide, acetonitrile, nitromethane, and acetone, in some cases mixed with water, as well as NH₃, SO₂, I₂, etc. On the basis of a model in which the ions are represented as charged spheres and the solvent as a homogeneous isotropic medium, the conductance theory can (at least for low electrolyte concentrations) give a more or less complete representation of the problem. A new statistical treatment of the transport problem confirms important results of this representation. The present state of the investigation is finally outlined in a review of recent publications.     

An Application of Percolation Theory to the Electrolyte Penetration through Porous Water-Swollen Cellulose Triacetate Membrane

Permeability coefficients P of KCl through porous cellulose triacetate (CTA) membranes were measured as a function of the water volume fraction V_W and diffusion coefficients D were determined using solubility parameters K and a membrane thickness d from the relationship of P = KD/d. D increased with an increase in V_W. D especially increases abruptly around V_W = 0.5, which corresponds to 2% triethylene glycol (TEG) content. The percolation theory was applied to the experimental results under the conditions D_A = D (V_W = 1) = 1.8 × 10⁻⁵ cm² s⁻¹, D_B = D(V_W = 0) = 1.8 × 10⁻⁸ cm² s⁻¹, coordination number (Z) = 2.5, 3, 3.5, and 4, and packing fraction f = 1.0. A good fit was obtained at Z = 3.5 because the experimental and calculated results also shifted at the same V_W below V_W = 0.5. It is suggested that a phase inversion, that is, change of a discontinuous water phase to a continuous water phase, occurs around V_W = 0.5. Above V_W = 0.5, the experimental results agree well with the calculated line for Z = 3 or Z = 2.5 which means that the coordination numbers decrease with an increase in water content. It is thought that V_W is overestimated because it is hard to completely wipe off the excess water quickly from the membrane surface. Z = 3.5 means that a pore can connect in 3.5 directions.     

Evidence of hydration forces between proteins

Proteins are fundamental molecules in biology that are also involved in a wide range of industrial and biotechnological processes. Consequently, many works in the literature have been devoted to the study of protein–protein and protein–surface interactions in aqueous solutions. The results have been usually interpreted within the frame of the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory for colloidal systems. However, against the DLVO predictions, striking evidence of repulsive forces between proteins at high salt concentrations has been observed in different works based on the analysis of the second virial coefficient or on the direct measurement of protein interaction with an atomic force microscope. Hydration forces due to the adsorption of hydrated cations onto the negatively charged protein surfaces have been invoked to rationalize this anomalous repulsion. The hydration forces between proteins provide protein-covered particles with a non-DLVO colloidal stability at high salt concentrations, as different studies in the literature has proven. This review summarizes the most relevant results published so far on the presence of hydration forces between proteins and protein-coated colloidal particles.     

The Solubility of Boric Acid in Electrolyte Solutions

The solubility of boric acid [B] in LiCl, NaCl, KCl, RbCl, and CsCl was determined as a function of ionic strength (0–6 mol ⋅ kg⁻¹) at 25 ^∘C. The results were examined using the Pitzer equation

强电解质溶液粘度的研究

研究对强电解质溶液粘度的影响因素,18种强电解溶液在不同温度和不同浓度下的粘度测定结果显示,强电解质溶液的粘度和离子强度、温度倒数分别成指数关系,符合经验公式:lnη=lna+b/T+kl,且粘度和电解质的电荷强度、离子半径等相关.     

电解质溶液中牛血清白蛋白分子相互作用的动态光散射研究

溶液中粒子斥与吸引作用力,这种依赖关系可以通过作用参数λ来的扩散系数对浓度的依赖关系主要取决于粒子在溶液中所占的体积分数和粒子间的排表示。本研究利用动态光散射技术测量了不同离子强度下牛血清白蛋白分子的扩散系数,求出了相应条件下的λ值。结果表明,在低离子强度下,λ是正值,蛋白质分子间的作用以排斥力为主,随着离子强度的逐渐增大,λ变为负值,蛋白质分子间的作用以吸引力为主,当离子强度大于0．5mol／L的时候,蛋白质开始发生聚集。利用DLVO理论的两体硬球相互作用模型解释了蛋白质分子间相互作用的变化规律：随着离子强度的增加,静电斥力被屏蔽,范德华分子作用力起主要作用。根据值与离子强度变化的相关性,回归出了蛋白质参数：在实验条件下,蛋白质所带的有效电荷Zr=-9．0e、Hamaker常量AH=2．8kBT。实验结果表明：动态光散射技术可以有效地用来研究蛋白质分子间的相互作用。     

锂离子电池有机电解液研究

本文分析了影响有机电解液电导率的主要因素 ;总结了有机电解液的一般特点 ,从有机溶剂和电解质锂盐两个方面介绍了有机电解液的化学和电化学 ;概述了各常用有机溶剂的性质和近年来的研究状况 ;综述了有机电解液在电解质锂盐、有机溶剂和添加剂三个方面的研究进展 .文章最后对有机电解液研究的现状作了简要的评论     

用Pitzer理论预测混合电解质溶液的偏摩尔体积

用Pitzer理论研究了混合电解质溶液的偏摩尔体积,建立了偏摩尔体积的预测方法,并利用所得电解质溶液的表观摩尔体积的Pitzer参数预测了HNO₃-UO₂(NO₃)₂-H₂O、KCl-Na₂SO₄-H₂O、NaCl-Na₂SO₄-H₂O、NaCl-CaCl₂-H₂O、KCl-CaCl₂-H₂O、KCl-MgCl₂-H₂O和KCl-NaBr-H₂O共7个系统4种类型的混合溶液的偏摩尔体积。     

纳滤膜对电解质溶液分离特性的理论研究(II): 混合电解质溶液

假定纳滤膜具有狭缝状孔, 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 用流体力学半径和无限稀释扩散系数表征了离子特性. 采用扩展Nernst-Planck方程、Donnan平衡模型和Poisson-Boltzmann理论描述了混合电解质溶液中离子在膜孔内的传递现象, 计算了三种商用纳滤膜(ESNA1-LF, ESNA1和LES90)对同阴离子、同阳离子和含四种离子的混合电解质体系中离子的截留率, 并与实验数据进行了比较. 计算结果表明, 电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对混合电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对含一价离子的混合电解质溶液通过纳滤膜的截留率计算结果比较准确, 但对高浓度或含高价离子的混合电解质溶液则偏差较大.     

Calculation of the osmotic and activity coefficients of seawater at 25°C

The equation of Reilly, Wood, and Robinson was used to predict the osmotic coefficient of seawater and of its concentrates at molal ionic strengths of 0.5 to 6.0 at 25°C. The results agree closely with experimental data at ionic strengths below 5. The average difference in osmotic coefficients over the entire concentration range is 0.0014. The only serious discrepancy is at an ionic strength of 6, where a difference of 0.0068 is found. The accuracy of the predictions of osmotic coefficients prompted the calculation of the activity coefficients of NaCl, Na₂SO₄, MgCl₂, MgSO₄, KCl, and K₂SO₄ in the mixture. The calculated activity coefficients of NaCl and Na₂SO₄ agree within experimental error with previous measurements. This agreement demonstrates the prediction of activity and osmotic coefficients for complex mixtures.     

Compressibility and thermal expansion coefficients of nanocomposites with amorphous and crystalline polymer matrix

Clay-containing polymeric nanocomposites (CPNC) with polystyrene (PS) or polyamide-6 (PA-6) matrix were studied within T = 300-600 K and P = 0.1-190 MPa. From the Pressure-Volume-Temperature (PVT) data the derivatives: compressibility, κ, and thermal expansion coefficient, α, were computed as functions of T, P and clay content, w. Dependence of these coefficients on P and T were significantly different for the amorphous PS than for the semi-crystalline PA-6. In the PS plots of κ and αvs.T the presence of secondary transitions, T_β/T_g ≈ 0.9 ± 0.1 and T_c/T_g = 1.2 ± 0.1, were detected and the clay effect at low T was prominent, affecting the physical aging. The isobaric values of α = α(T) were characterized by nearly T-independent values in the glassy and molten phase, connected by a large transitory region stretching from the ambient pressure values of T_g to T_c; this region was even more prominent in κ = κ(T). The derivative properties of PA-6 based CPNC were distinctly different. Here, the isobaric κ = κ(T) followed the same dependence on both sides of the melting zone, while the isobaric α = α(T) dependencies were dramatically different for the solid and molten phase; at T < T_mα linearly increased with T, after melting its value sharply decreased, and then at T > T_m (depending on w and P) either increased or decreased with T. Interpretation of the behavior in the melt and glass is based on the Simha-Somcynsky (S-S) cell-hole theory while that of the semicrystalline state on the Midha-Nanda-Simha-Jain (MNSJ) cell theory. In spite of the nonequilibrium conditions below the main transition point, T_g or T_m, the theories well predict the observed dependencies.