单原子离子溶剂化的研究 Ⅰ. 偏摩尔体积与溶剂化数

本文用比重法测定了25 ℃一些盐在N,N-二甲基甲酰胺和碳酸丙烯酯中的偏摩尔体积。在统计热力学理论推导的基础上, 提出了一种将盐的偏摩尔体积划分为离子的偏摩尔体积的方法。运用单层结构模型, 得到了从离子偏摩尔体积求离子溶剂化数的公式。讨论了各种类型离子的溶剂化数的某些现象和规律。     

Volume and compressibility changes of complex formation between 18-Crown-6 and NaCl,KCl, and CsCl in water

The apparent molal volumes and compressibilities of NaCl, KCl, and CsCl in mixtures of 18-Crown-6 and water have been calculated from density and speed-of-sound measurements at 25°C. The partial molal volumes and compressibilities of the salts when all cations have formed complexes with 18-Crown-6 molecules have been evaluated. The sign and magnitude of the volume and compressibility changes of complex formation strongly suggest that the charge of the cation becomes very effectively screened by the crown ether.     

Apparent molal volumes of phosphonium halides at 15, 25 and 35°C

The densities of aqueous solutions of the phosphonium halides, Bu _4-n Ph _n PX(n=0–4), some of which were synthesized from the phosphines, were measured at 15, 25 and 35°C. Partial molal volumes at infinite dilution, , and B _v coefficients for the apparent molal volumes were determined at each temperature. For the first four cations varies little with n. For all salts B _v are negative but become less negative with increasing n. The temperature dependence of B _v is positive for butyl-rich salts (n<2) but negative for phenyl-rich salts (n>1). Also it appears that is relatively large for phenyl-rich cations in comparison with that for butyl-rich cations.     

The volumetric and thermochemical properties of YCl3(aq), YbCl3(aq), DyCl3(aq), SmCl3(aq), and GdCl3(aq) at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa

Relative densities and massic heat capacities have been measured for acidified aqueous solutions of YCl₃(aq), YbCl₃(aq), DyCl₃(aq), SmCl₃(aq), and GdCl₃(aq) at T=(288.15, 298.15, 313.15, and 328.15) K and p=0.1 MPa. These measurements have been used to calculate experimental apparent molar volumes and heat capacities which, when used in conjunction with Young’s rule, were used to calculate the apparent molar properties of the aqueous chloride salt solutions. The latter calculations required the use of volumetric and thermochemical data for aqueous solutions of hydrochloric acid that have been previously reported in the literature. The concentration dependences of the apparent molar properties have been modeled using Pitzer ion interaction equations to yield apparent molar volumes and heat capacities at infinite dilution. The temperature and concentration dependences of the apparent molar volumes and heat capacities of each trivalent salt system were modeled using modified Pitzer ion interaction equations. These equations utilized the revised Helgeson, Kirkham, and Flowers equations of state to model the temperature dependences of apparent molar volumes and heat capacities at infinite dilution. Calculated apparent molar volumes and heat capacities at infinite dilution have been used to calculate single ion properties for the investigated trivalent metal cations. These values have been compared to those previously reported in the literature. The differences between single ion values calculated in this study and those values calculated from thermodynamic data for aqueous perchlorate salts are also discussed.     

Association studies of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride in ethanol solutions at 25°C

Practical osmotic coefficients of ethanol solutions of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride were determined by the isopiestic method at 25°C. The relations for the concentration dependences of practical osmotic coefficients, mean molal activity coefficients of solutes and for the excess Gibbs free energies of solutions and partial molal excess Gibbs free energies of solutes and solvents are given in analytical form. The results obtained are compared with those reported previously; in the case of tetramethylguanidinium perchlorate with its aqueous and methanol solutions, in the case of tetramethylguanidinium chloride with its aqueous solutions. The non-ideal behavior of the systems investigated is discussed on the basis of the structure of solute species, as well as on the nature of the solvent.     

Apparent molal volumes of aqueous solutions of bis-tetraalkylammonium salts at 25°C: Methylene-group contribution to the limiting molal volume

Densities of aqueous solutions of a series of polymethonium chloride and bromide salts (CH₃)₃–N–(CH₂)_n–N–(CH₃)₃X₂ have been measured at 25°C. Apparent molal volumes have been calculated, and methylene-group contributions to the limiting apparent molal volumes °_v have been estimated. Constant values of the methylene-group contribution of 16.5 and 17.0 cm³-mole^–1 were obtained for the bromide and chloride salts, respectively. These values are consistent with methylene-group contributions reported for other series of organic electrolytes.     

Thermodynamics of bolaform electrolytes. IV. Enthalpies and partial molal heat capacities in H2O,D2O,and dimethylsulfoxide

The partial molal heats of solution ΔH _s ^o and the partial molal heat capacities of solution ΔC _p ^o of the bolaform salts [Et₃N(CH₂)_nNEt₃]Br₂ and [allyl₃N(CH₂)_nNallyl₃]Br₂ have been obtained at infinite dilution in dimethylsulfoxide (DMSO). A comparison of these data with the results of previous thermodynamic studies of the same solutes in aqueous solvents has been carried out. The observed differences have been interpreted in terms of solute-induced solvent structural effects occurring in aqueous solvent media. Partial molal heat capacities of the bolaform salts at infinite dilution in DMSO, H₂O, and D₂O have been calculated from ΔC _p ^o data and previously reported values of the heat capacities of the crystalline state. The data clearly show that the structure-promoting capabilities of these salts in aqueous solvents increase with increasing hydrocarbon content. A comparison of contributions to partial molal heat capacities of methylene groups in the bolaform and R₄N⁺ series of salts reveals that similarities exist between the solvation effects of CH₂ groups in the normal alkyl chain of the R₄N⁺ cations and in the bridging alkyl chain of the bolaform cation.     

Partial molal volumes of polymers in aqueous solutions from partial molal volume group contributions

It is shown that the partial molal volumes (pmv) of the repeat units of nonionic polymers in aqueous solutions calculated from pmv group contributions, obtained from pmv data for small molecules and salts in aqueous solutions, agree in most instances to within ± 1 cm³/mole with the experimental values. The pmv of ionic polymers calculated from pmv group contributions have been found to be always larger than the experimental values. The difference gives a lower bound of the cooperative electrostrictive effect of neighboring charged sites of the polymer chain on surrounding water molecules.     

Thermodynamics of aqueous bile salt solutions: Heat capacity,enthalpy and entropy of dilution

Heat capacity data at various temperatures and enthalpies of dilution at 25°C are reported for aqueous bile salt solutions. The apparent molal heat contents _L have been combined with osmotic and activity coefficients to obtain the excess molal entropies. Measurements of some of these properties have also been carried out with the anionic detergent sodium dodecylsulfate so that the bile salt micellization process may be compared with that of a classical detergent. The observed data have been interpreted in terms of the hydrophobic association properties of bile salts in aqueous solution.     

甘氨酸和L-丝氨酸在LiNO3, NaNO3和KNO3水溶液中的体积性质

用Anton Paar DMA 55精密数字密度计测定了甘氨酸和L-丝氨酸在LiNO3, NaNO3和KNO3水溶液中的密度, 计算了氨基酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积、理论水化数和体积作用系数. 根据静电相互作用和结构水合作用模型讨论了氨基酸的侧链和阳离子的性质对迁移偏摩尔体积的影响. 结果表明, 甘氨酸和L-丝氨酸在3种硝酸盐水溶液中的迁移体积均为正值, 并且随着盐溶液浓度的增大而增大. 氨基酸两性离子端基和阴阳离子间的静电作用对迁移体积的贡献是主要的, 静电作用削弱了两性离子带电中心对周围水分子的电致收缩效应, 造成氨基酸的理论水化数随盐溶液浓度的增加而减小. L-丝氨酸的侧链与离子之间的亲水-亲水相互作用对迁移体积有小的正贡献, 使得在同一种盐溶液中L-丝氨酸的迁移体积较甘氨酸的大. 同一种氨基酸在NaNO3和KNO3水溶液中的迁移体积较在LiNO3水溶液中的大, 主要是由于Li＋难以去水化. 在低浓度的盐溶液中氨基酸与盐之间的相互作用以1∶1形式为主, 随着溶液浓度的增大, 1∶2形式的相互作用逐渐增大     

Solution thermodynamics of first row transition elements. 3. Apparent molal volumes of aqueous ZnCl2 and Zn(CIO4)2 from 15 to 55°C and an examination of solute-solute and solute-solvent interactions

The apparent molal volumes of aqueous ZnCl₂ and Zn(ClO₄)₂ solutions have been measured from 15–55°C. The dilute solution data are extrapolated to infinite dilution using the Redlich-Meyer equation. The full concentration range data are fitted with the Pitzer formalism. The data are then compared with the data on the previously measured salts of Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, and Cu²⁺. The effect of complex ion formation is easily seen in the Cu²⁺ and Zn²⁺ salt data. A new approach to single ion volumes from salt volumes is proposed. The calculated ionic volumes at infinite dilution are compared, and it is clear that crystal field effects must be considered in any quantitative theory of transition element volumes.     

Thermodynamic behavior of water-acetonitrile mixtures excess volumes and viscosities

Densities of water+acetonitrile mixture have been measured from 308.15 to 278.15 K over the entire composition range. Partial molal volumes of both components of the mixed system have been calculated and deviations from ideal volumes of mixing have been evaluated. Literature data on viscosity have also been treated by a least square method and activation thermodynamic functions of viscous flow computed. Structural correlations have been made with previous results on acid-base properties; they allow to distinguish several interaction regions between components of binary systems.     

Aqueous Guanidinium Salts: Part I. Densities, Ultrasonic Velocities, and Apparent Molar Properties

The densities and ultrasonic velocities in aqueous solutions of guanidinium chloride, bromide, acetate, perchlorate and sulfate have been measured at 25°C. The infinite dilution partial molar volumes and compressibilities of the salts were estimated and analyzed by the Pitzer equations. The concentration dependence of densities and sound velocities of the guanidinium salts can be correlated by the Pitzer equations with an average root-mean-square deviation of 0.025 kg-m^-3 and 0.31 m-s^-1, respectively.     

Apparent molal volumes of the solutions of CaCl2 and Ca(NO3)2 in ethanol at 298.15: experimental data and correlation by local composition models

Apparent molal volume of the solutions of CaCl₂ and Ca(NO₃)₂ in ethanol are reported and correlated using equations obtained from the various local composition (LC) models. The considered models are e-NRTL, NRF, MNRTL, and EW models. The applicability of the models has been discussed with comparing their standard deviations with those obtained from the Pitzer model and a polynomial equation. Limiting partial molal volumes of the salts have been obtained using dilute region data via the Redlich–Meyer equation.     

Ultrasonic vibration potentials,apparent molal volumes,and apparent molal heat capacities of 1:1 electrolytes in acetonitrile

The ultrasonic vibration potentials and apparent molal volumes for many inorganic and organic electrolytes were measured in acetonitrile at 25°C and combined to obtain ionic contributions to the standard partial molal volumes V°(ion). Monatomic cations and anions of the same size essentially have the same V°(ion). Their size dependence can be interpreted through Hepler's equation. The apparent molal heat capacities were also measured in acetonitrile and used to derive standard values. Various methods of estimating C _p ⁰ (ion) were investigated and an ionic scale is proposed. It is concluded that C _p ⁰ (ion) of large organic ions are very close to the intrinsic heat capacities of the ions, and the solvation contribution to monatomic ions is positive for both cations and anions.     

The ionization of perchloric and hydrofluoric acids in aqueous solution

Cyclical bifurcated hydrogen bonded structures are proposed for aqueous solutions of hydrofluoric acid and for the bifluoride ion which are consistent with the spectral data. The structure proposed for HF is also applicable to solutions in organic solvents. Raman spectra of tetramethylguanidinium perchlorate suggest that the corresponding Raman spectra of perchloric acid solutions may not be interpreted in terms of a completely dissociated acid. Other evidence including activity coefficient, heat capacity and partial molal volume data suggest that there is some association in relatively dilute perchloric acid solutions between the perchlorate ion and the hydrated proton. This association decreases in concentrated aqueous solutions.     

Structural interaction leading to volumetric changes in aqueous solutions of nitrates of rubidium,cesium, strontium,yttrium, and gallium at different temperatures

Densities of the aqueous dilute solutions of rubidium, cesium, strontium, yttrium, and gallium nitrate were measured at different temperatures ranging from (293.15–343.15) K and atmospheric pressure. From these density values, the apparent molal volumes were calculated and fitted to Masson’s correlation and the temperature dependence was correlated by a second order polynomial. The apparent molal volumes at infinite dilution and experimental slopes have been interpreted in terms of ion–solvent and ion–ion interactions, respectively. The measurements include density as per ASTM D-4052, refractive index (nD²⁵) at sodium D line at 25 °C. Thermal isobaric expansibility was calculated and structure making and structure breaking behaviour of electrolytes were inferred from the sign of the second derivative of apparent molal volumes with respect to temperature at constant pressure. The experimental apparent molal volume was compared with the available literature value.     

Heat capacity measurements in carboxylic polyelectrolyte solutions

Apparent molal heat capacities as a function of the degree of neutralization have been determined for dilute aqueous solutions of poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), copoly(maleic acid-ethylene) (MAEt), and copoly(maleic acid-styrene) (MASt) using direct flow microcalorimetry. Apparent molal volumes were measured as well. Both molal heat capacity and molal volume decrease with increasing ionization of the polymer. The effect of the hydrophobic interactions of the methyl group or phenyl group was obtained from the difference in the molal quantities of PMA and PAA, or MASt and MAEt. No evidence of hydrophobic effects, as determined from the heat capacity, was found for the conformational transition of PMA, but the hydration of the phenyl groups in MASt was found to be changed significantly at a degree of neutralization of 0.4.     

Partial molal volumes of alcohols in propylene carbonate at 25°C

The densities of the homologous series of alcohols and diols R_nCH₂OH (n=2–6), CH₃CHOHR_n (n=1–5), 1,2-propanediol, 1,3-1,4-, and 2,3-butanediol, 1,5-pentanediol, and 1,7-heptanediol dissolved in propylene carbonate have been measured at 25°C. The partial molal volumes at infinite dilution have been evaluated. Additivity of group molal volumes has been confirmed in propylene carbonate. The results have been discussed in relation to the same data in aqueous solution, and the scaled particle theory has been employed to calculate intrinsic volumes of the solutes.     

The Standard Partial Molar Volumes of Ions in Solution. Part 3. Volumes in Solvent Mixtures Where Preferential Solvation Takes Place

Standard partial molar volumes of 1:1 salts in aqueous mixtures of ethanol (EtOH), dimethyl sulfoxide (DMSO) and acetonitrile (MeCN) at 298.15 K were obtained from the literature. In such mixtures there is evidence that preferential solvation occurs in the solvent shell around the ion where electrostriction takes place. Specifically, the anions are better solvated by the water whereas the cations are generally solvated by both the water and the nonaqueous component of the mixtures to various extents. There are no clear-cut criteria for how the measured volumes are to be apportioned between the ions in such mixtures. Various solvation models were used to estimate the volumes of the salts by calculation of the electrostriction around the ions. Only the taking into account of the preferential solvation of the ions in the solvation shell yielded calculated results of the standard partial molar volumes of the salts in agreement with the experimental data.