Aqueous-phase ion solvation and the selectivity of anion exchange resins for monovalent ions

This research examines and quantifies the influence of ion solvation parameters on the affinity of monovalent anions for strong-base anion resins. A data set comprising resin selectivity coefficients and solvation parameters from the literature is statistically analyzed using correlation and multiple regression techniques. The affinity of monovalent anions for the resin phase correlated well to ionic radii. Solvation parameters such as the hydration number, and entropy, enthalpy and free energy of hydration are also strongly correlated to selectivity. Using the stepwise regression procedure on subsets of independent variables, the entropy of hydration, which characterizes the structure-influencing nature of ions in solution, is incorporated as the sole parameter in the predictive model for resin selectivity. The data are best correlated by the exponential form of the regression equation, and the physical meaning of the correlation is shown to be reasonable. A simple rule for categorizing ions as structure-makers and structure-breakers is proposed, and the results are consistent with conventional classifications.     

Error of DIAL-measured Ozone Concentration and a Three-Wavelength Inversion Technique

Sensitivity of the error in the stratospheric ozone concentration measured by DIAL to the scattering property of the stratospheric aerosol is studied through both theoretical analysis and numerical experiment in this paper, and based on the sensitivity, a three-wavelength lidar inversion technique is proposed for a simultaneous determination of ozone concentration profile, aerosol backscatter coefficient profile and its size distribution in the stratosphere. It is found from the sensitivity study that there is a considerable effect of the stratospheric aerosol on accuracy of the ozone concentration solution. If the aerosol scattering is neglected, a large error of the solution can be obtained, especially when there is the stratospheric volcanic cloud, the error can be up to 100%. According to numerical experiments, a great improvement of the ozone concentration solution is obtained by using the present three-wavelenght inversion method.     

Osmotic and activity coefficients of sodium chloride-sorbitol and potassium chloride-sorbitol solutions at 25°C

Osmotic and activity coefficients are reported for sorbitol over the range 1.8–11.1m with NaCl as the reference and 1.8–7.6m with KCl as the reference electrolyte. The osmotic coefficients over the range 0–3.7m are identical with those reported earlier by Robinson. It was found that the activity coefficients of sorbitol are uniformly about four percent lower than those of dextrose. Activity coefficients of trace quantities of NaCl in concentrated sorbitol solutions are about one-half of their value in pure NaCl solutions while the activity coefficients of trace quantities of sorbitol in concentrated NaCl solutions are about one-third of their value in pure sorbitol solutions. Potassium chloride lowers the activity coefficient of sorbitol less than does sodium chloride in solutions of similar water activity. Sorbitol lowers the activity coefficients of potassium chloride in concentrated solution but actually elevates them in dilute solutions.     

Volumetric properties of ethanol–water mixtures under high temperatures and pressures

The densities of ethanol and ethanol–water mixtures were measured with a vibrating tube densimeter at 25.0, 50.0 and 75.0 °C in the pressure range from 0.10 to 40.00 MPa. Densities were correlated using an empirical model. Partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures were calculated from obtained densities. This study reports the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures on composition, temperature and pressure.     

含铅聚合物微凝胶与硫化氢反应前后在良溶剂中的分子扩散行为

用溶液聚合法制备出轻度交联的含铅微凝胶,用光子相关光谱技术测定其在良溶剂中与H2S反应前、后的扩散行为,由外推法得到在浓度无限稀时的分子扩散系数,给出微凝胶的流体力学半径。结果表明:相同量的含铅微凝胶在不同的初始浓度下与H2S反应,生成含PbS纳米微粒的凝胶；但其体积增大不同,这说明H2S与含铅微凝胶的反应既可以在分子内也可以在分子间进行,分子间的反应使含硫化铅微凝胶扩散系数随浓度的变化曲线的线性范围变小。     

硝基甲烷在离子液体BMImBF4中的电还原特性

采用循环伏安等测试方法, 以铂微盘电极为工作电极, 研究了硝基甲烷在离子液体1-正丁基-3-甲基咪唑四氟硼酸盐(BMImBF4)中的电化学行为, 并探讨了温度和扫描速率等因素对硝基甲烷电化学特性的影响. 实验结果表明, 硝基甲烷在离子液体BMImBF4中的还原反应是受扩散控制的不可逆过程. 估算了不同温度下硝基甲烷在离子液体BMImBF4中的扩散系数D, 进而求得它的扩散活化能Ea约为39.5 kJ·mol-1.     

固定pH滴定法测定弱酸弱碱性药物

报道一种水溶液吕测定弱酸弱碱性药物的新型滴定分析方法－固定ｐＨ滴定法，其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在ｐＨ值固定时为常数，对甲硝唑，盐酸美西律等离散常数在１０＾－８至１０＾－１１范围内的７种弱酸弱碱性药物进行测定。结果与药典法吻合，回收率在９９．４％～１００．６％，方法简便，快速，准确，制剂中的赋形剂及色物不影响测定。     

Nondestructive Monitoring of Sucrose Diffusion in Oil-in-Water Emulsions by Ultrasonic Velocity Profiling

The diffusion of sucrose through an optically opaque oil-in-water emulsion was monitored nondestructively by measuring the ultrasonic velocity as a function of height. Initially, a corn oil-in-water emulsion (0, 5, 10, 15, or 20 wt% oil) stabilized by Tween 20 (1 wt%) and xanthan (1 wt%) was placed in a measurement cell at 30°C. A 20 wt% sucrose solution containing the same concentration of Tween 20 and xanthan as the aqueous phase in the emulsion was placed on top of the emulsion. The ultrasonic velocity of this two-layer system was measured as a function of sample height and time and then converted into sucrose and oil concentration–distance profiles using empirical calibration curves. The translational diffusion coefficient of the sucrose in the upper and lower layers was determined by fitting the experimental data to a Fickian diffusion model. The measured diffusion coefficients of the sucrose molecules decreased as the droplet concentration in the emulsion increased, indicating retardation of the sugar molecule movement. Ultrasonic profiling was also used to monitor the compression of the emulsion due to movement of water molecules into the upper layer.     

Equilibrium conformations of polymer chains Part II. Conformons in networks

With regard to the ideal network it is shown that the concept ofN non-interacting polymer chains can be transformed in a problem of non interacting excitations (called conformons) for rubber elasticity. Modelling the interaction on permanent crosslinks as a scattering problem and taking the finite chain length into account, an interpretation of the second Mooney coefficient can be given. There is some evidence that the junctions move by constrained self diffusion.Dedicated to Prof. Dr. W. Ruland on the occasion of his 60th birthday.     

Unusual ion pairs and their relationship to acid ionization

Osmotic and activity coefficients, determined from isopiestic measurements, are presented for aqueous solutions of eight tetramethylguanidinium salts. It is proposed that both hydronium and tetramethylguanidinium ions are capable of forming stable ion pairs with many anions by means of bridged hydrogens forming six-membered rings and that these ion pairs are stable in rather dilute aqueous solutions.