Apparent Molar Volumes of Multicharged Cations in Dimethyl Sulfoxide Solutions at 25°C

Densities for DMSO solutions of iron(III), aluminium(III), beryllium(II) and magnesium(II) perchlorates and silver nitrate are reported. Densities for DMSO solutions of tetraethylammonium perchlorate and nitrate and tetrabutylammonium perchlorate and tetraphenylborate are also presented. The partial molar volumes of the DMSO-solvated cations are derived and discussed in terms of variation with the charge number.     

Apparent Molar Volumes of Divalent Transition Metal Cations in Dimethyl Sulfoxide Solutions

Densities for DMSO solutions of divalent transition metal perchlorates are reported. The partial molar volumes of the hexakis-(DMSO) cations are derived and discussed in terms of variation within the series. The ligand-field effect on the partial molar volume and enthalpy of solvation is demonstrated.     

Volumetric properties of aqueous electrolytes at high temperature: Mixtures of LiOH and KOH up to 523 K

The densities of mixtures of aqueous lithium and potassium hydroxides were measured up to 3 molal, at 373, 423 and 523 K at pressures close to saturation. The partial molar volumes were calculated and the coefficients of the Pitzer equation for the mixtures were obtained. The mixing volume is positive at 373 K while at higher temperatures the mixture is ideal within experimental error, probably as a result of association of the lithium hydroxide.     

Temperature effect on the volume properties of a bisurea aqueous solutions

The densities of aqueous solutions of bisurea (2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione) were measured using a vibrating-tube densimeter at 288.15, 298.15, 308.15, and 318.15 K in the concentration range up to ∼3·10⁻³ moles of solute (1000 g of H₂O)⁻¹ with the error at most ±5· 10⁻⁶ g cm⁻³ (reproducibility up to 2·10⁻⁶ g cm⁻³). The limiting partial molar volume and expansibility of bisurea in water were calculated. The bicyclic molecules under study form in aqueous solution H-bonded hydrate complexes with rather high structure-packing density. These complexes are more subjected to the destroying effect of temperature than the corresponding urea complexes. The hydration of bisurea weakens with the temperature increase. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1929–1932, October, 2007.     

Ion-solvent interactions in aqueous solutions at various temperatures

The temperature variation of the limiting partial molar volumes of a number of electrolytes in aqueous solution has been examined in terms of solvent electrostriction. The Desnoyers, Verrall, and Conway theory has been modified and extended to cover the temperature range 0–100°C. It has been shown that electrostriction effects alone cannot account for the observed maxima in the V° –T plots for various electrolytes. It is concluded that solvent structural changes over this temperature range may well be important.     

Partial molar volumes of sodium chloride solutions at 200 bar,and temperatures from 175 to 350°C

High precision densities of sodium chloride solutions at a constant pressure of 200 bar and temperatures between 175°C and 350°C have been measured by a mercury displacement technique. The densities have been converted to apparent molar volumes. The apparent molar volumes decrease with increasing temperature and decreasing concentration whereas the concentration effect increases with temperature. Standard partial molar volumes range from 8.0 cm³-mol^–1 at 175°C to –600 cm³-mol^–1 at 350°C. The results indicate the applicability of the unextended Debye-Hückel limiting law up to concentrations of 0.02 mol-kg^–1.     

L-丝氨酸在正丙醇-水混合溶剂中的体积性质

应用精密数字密度计测定了298.15 K时不同组成的L-丝氨酸-正丙醇-水体系的密度, 计算丝氨酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积和水化数. 根据结构水合作用模型讨论了迁移偏摩尔体积和水化数的变化规律. 结果表明, 丝氨酸两性离子部分和亲水侧链与正丙醇羟基间的相互作用对其迁移体积有正贡献, 且占主导地位. 丝氨酸在正丙醇-水混合溶剂中的迁移偏摩尔体积为正值, 且随醇浓度的增大而增大. 丝氨酸在正丙醇-水混合溶剂中的水化数随溶液中醇浓度的增加而减小.     

On the Determination of Equilibrium Constant and Thermodynamic Parameters for the Association Process of Hydrogen Bond Complexes Using Relaxation Parameters

Abstract

A dielectric study of H-bond complexes of three acetates namely ethyl acetate, butyl acetate, and benzyl acetate with the proton donor (O-Cresol) has been made. The equilibrium constant and the thermodynamic parameters for the association process as well as the dielectric relaxation process have been determined from the dielectric data using an equation, proposed in our earlier paper. The results obtained being in agreement with the literature values thus support the validity of the proposed equation.     

甘氨酸在多元醇-水混合溶剂中的体积性质

利用精密数字密度计测定了甘氨酸分别在不同组成的乙二醇 水和丙三醇 水混合溶剂中的密度,计算了甘氨酸的表观摩尔体积、极限偏摩尔体积和理论水化数.根据结构水合作用模型讨论了迁移偏摩尔体积的变化规律,并与乙醇 水体系作了比较. 结果表明,甘氨酸分子在醇 水混合溶剂中增体积效应的大小与醇分子所含OH基数目的多少有关,但最直接也是最重要的影响因素是其水合壳层的结构形态. 乙醇 水体系中的增体积效应特别显著与该溶剂结构变化上的微观不均匀性和不连续性有关.     

Densities and partial molar volumes of aqueous solutions of lithium,sodium, and potassium hydroxides up to 250°C

The densities of aqueous solutions of lithium, sodium and potassium hydroxides were measured up to 3m (mol-kg^–1) with a vibrating tube densimeter from 55 to 250°C an at pressures close to saturation. The apparent molar volumes of the solutions were calculated and the infinite dilution values at each temperature and saturation pressure were obtained by extrapolation. The present data are compared with literature values (for LiOH and KOH below 75°C and over the entire temperature range for NaOH) and with the predictions of a semiempirical model. It is concluded that the high temperature data for NaOH reported here improves the available experimental information on the volumetric properties of this system. The influence of ion association on the volumetric properties of LiOH solutions is also discussed.