Correlations of Thermodynamic Properties of Aqueous Amino Acid-Electrolyte Mixtures

Suitable equations have been proposed to correlate thermodynamic properties, like mean ion activity coefficients, volumes and compressibilities, of amino acids in electrolyte solutions. An amino acid–electrolyte–water interaction parameter is extracted from the regression of the amino acid property values in aqueous electrolyte solution that is then transferred to an expression to correlate the properties of the electrolyte in mixtures. The single interaction parameter can successfully correlate the published data on mean ion activity coefficients, apparent molar volumes and compressibilities of amino acids as well as of electrolytes in their aqueous mixtures. The equations are tested against the large number of experimental data sets available in the literature.     

Ionic interactions from volumetric investigations of l-alanine in NaBr,KCl, KBr and MgCl2 up to high concentrations

The densities and sound speeds of l-alanine in aqueous NaBr, KCl, KBr and MgCl₂ are reported at 298.15 K. These data are used to derive apparent molar volumes and compressibilities. The apparent molar properties of l-alanine are greatly influenced by MgCl₂ than any other electrolytes studied herein. The apparent molar properties of l-alanine are correlated with concentration of the electrolyte using two adjustable parameters, which in turn are employed to predict the properties of electrolytes with good accuracy. The proposed method yields good estimates of densities and sound speeds.     

Apparent Molar Volume, Isentropic Compressibility, Refractive Index, and Viscosity of DL-Alanine in Aqueous NaCl Solutions

New experimental data at 25^°C for the density, velocity of sound, refractive index, and viscosity of aqueous solutions of DL-alanine and NaCl are reported. The apparent molar volume and isentropic compressibility of DL-alanine in aqueous electrolyte solutions have been calculated from the measured properties. The results show that DL-alanine exhibits a positive volume transfer to solutions of a higher NaCl concentration and a negative apparent isentropic compressibility for DL-alanine in the presence of NaCl. These effects indicate that the apparent volume of DL-alanine is larger in solutions with higher electrolyte concentration and the water molecules surrounding the DL-alanine molecules are less compressible than the water molecules in the bulk solution. The results also show an increase in the viscosity of the solution with an increase in both DL-alanine and NaCl concentrations. These effects are attributed to the two charged groups of DL-alanine and the interactions between the charged groups and the hydrocarbon backbone of DL-alanine with the ions. A model, consisting of a short-range interaction term represented by a virial expansion and a Debye-Hückel term that considers long-range interactions, has been developed to correlate the measured experimental data.     

Correlation of the mean ionic activity coefficients of electrolytes in aqueous amino acid and peptide systems

The activity coefficients of electrolytes in amino acid (peptide) aqueous systems were predicted using an expression for the excess Gibbs free energy of the solution. The model combines the contribution of long-range interactions given by the Khoshkbarchi–Vera model and the contribution of short-range interactions by the local composition based models such as the Wilson, the NRTL and the NRTL–NRF. The local composition models accurately correlate the activity coefficients of 30 amino acid (peptide)–water–electrolyte systems. The results show that the Wilson model can accurately correlate the activity coefficient of the electrolyte in amino acid (peptide) aqueous systems.     

A computer controlled continuous dilution dilatometer for the determination of solute molar volumes and direct measurement of reaction volumes in solution

The design and operation of a computer controlled continuous dilution dilatometer utilizing a diode array detection system is presented. To test the accuracy and reproducibility of the technique, apparent molar volumes of dilute aqueous solutions of potassium ferricyanide and potassium ferrocyanide have been measured. To provide supporting data for high pressure studies of reaction volumes and molar volume change in solutions of high ionic strength, study of these electrolytes was extended by dilution into 0.1M and 1.0M potassium nitrate solutions rather than extrapolation to zero ionic strength as is normal. In addition, the system has been used to determine reaction volumes of some acid-base reactions by direct measurement, using the equipment as an automatic titration dilatometer.     

Partial molar volumes of l-alanine,dl-serine,dl-threonine,l-histidine,glycine, and glycylglycine in water,NaCl, and DMSO aqueous solutions at T = 298.15 K

The apparent molar volumes of l-alanine, dl-serine, dl-threonine, l-histidine, glycine, and glycylglycine in water and in the aqueous solutions of NaCl and DMSO with various concentrations at T = 298.15 K have been measured by the precise vibrating-tube digital densimeter. The calculated partial molar volumes at infinite dilution have been used to obtain corresponding transfer volumes from water to various solutions. The experimental results show that the standard partial molar volumes of the above amino acids and peptide at the dilute DMSO aqueous solutions are very close to those in water. However, the volumes show several types of variations with the increase of the concentrations of DMSO due to different types of side chain of amino acids, which should be discussed specifically. The NaCl changes considerably the infinite dilution standard partial molar volumes of the above amino acids and peptide in the aqueous solutions. The infinite dilution standard partial molar volumes of the each amino acids and peptide increase with the concentrations of NaCl. The experimental results have been rationalized by a cosphere overlap model.     

298.15 K甘氨酰二肽在乙酸钠水溶液中的体积性质

测定了298.15 K三种甘氨酰二肽(甘氨酰甘氨酸、甘氨酰-L-缬氨酸和甘氨酰-L-亮氨酸)在0.5, 1.0, 1.5和2.0 mol•kg－1乙酸钠水溶液中的密度, 计算了这些肽在乙酸钠水溶液中的表观摩尔体积, 标准偏摩尔体积, 标准偏摩尔转移体积, 理论水化数和体积相互作用参数. 结果表明: 甘氨酰二肽的标准偏摩尔体积和标准偏摩尔转移体积均随乙酸钠浓度的增加而增大, 溶液中离子与肽带电基团/甘氨酰基团(CH2CONH)之间的相互作用大于离子与肽的非极性基团间的相互作用, 乙酸钠和甘氨酰二肽之间主要是对相互作用. 利用共球交盖模型对所研究的肽与乙酸钠之间的体积相互作用进行了解释. 利用氨基酸的标准偏摩尔体积值, 对二肽的标准偏摩尔体积进行了估算, 发现计算值与实验值一致.     

Thermodynamics of Diglycine and Triglycine in Aqueous NaCl Solutions: Apparent Molar Volume, Isentropic Compressibility, and Refractive Index

New experimental data for the density, speed of sound, and refractive index of aqueous solutions of diglycine + NaCl and triglycine + NaCl have been reported. The apparent molar volume and apparent molar isentropic compressibility of these peptides at various NaCl concentrations have been calculated from the measured properties. The results show that both peptides exhibit a positive volume transfer to solutions with higher NaCl concentrations and a negative apparent isentropic compressibility in the presence of NaCl. These effects indicate that the apparent volumes of the peptide molecules are larger in solutions with higher NaCl concentrations and that the water molecules around the peptide molecules are less compressible than the water molecules in the bulk solvent. These effects are attributed to the doubly charged nature of the peptides and the interactions between the charged groups and hydrocarbon backbone of peptides with the ions.     

Li7P3S11电解质的合成、传导及应用

固态电解质是固态电池中的关键材料,开发具有高离子电导率、高化学/电化学稳定性、电极兼容性良好的固态电解质正成为研究热点。硫化物固态电解质相较其它固态电解质具有更高的离子电导率和良好的机械加工性能等优势,是最有前景实现实用化的固态电解质之一。在众多硫化物固态电解质中,Li₇P₃S₁₁因其高的离子电导率和较低的原料成本而极具研究意义。本文首先介绍了Li₇P₃S₁₁电解质的结构、Li+传导机理及合成路径;其次,针对该电解质的电导率提高、空气/水稳定性提升、固固界面稳定性及电解质自身稳定性改善等问题,综述了目前常用的改性策略研究;再次,总结了基于Li₇P₃S₁₁电解质的全固态锂离子电池和全固态锂硫电池的构筑;最后,本文分析了Li₇P₃S₁₁电解质的研究和应用面临的挑战,并指出该电解质未来发展的趋势。     

Effect of tetra-n-alkylammonium bromides on the volumetric properties of glycine,l-alanine and glycylglycine at T=298.15 K

The effect of tetra-n-alkylammonium bromides, R₄NBr (R=CH₃, C₂H₅, C₄H₉) on the densities, ρ, of glycine, l-alanine and glycylglycine are reported at T=298.15 K. The apparent molar volumes of amino acids in aqueous tetra-n-alkylammonium salts, φ_VAJW, and of tetra-n-alkylammonium bromides in aqueous amino acids and peptide, φ_VJAW, are calculated from the measured densities. Both φ_VAJW and φ_VJAW have been analysed accurately using a simple equation. Positive transfer volumes are observed for glycine, l-alanine and glycylglycine in the presence of R₄NBr. Tetra-n-butylammonium bromide shows almost double increase in the transfer volumes of amino acids or peptide than tetramethyl- or tetraethylammonium bromides. Negative transfer volumes for the tetra-n-alkylammonium bromide salts are noted in aqueous amino acids or peptide due to large tetra-n-alkylammonium cation undergoing hydrophobic hydration.     

Volumetric studies to examine the interactions of imidazolium based ionic liquids with water by means of density and speed of sound measurements

Densities and speeds of sound for aqueous solutions of ionic liquids having 1-butyl-3-methylimidazolium as cation and chloride, bromide, iodide, acetate, tetrafluoroborate, and trifluoromethanesulfonate as anions were accurately measured at various concentrations and temperatures. The data were used in evaluating thermodynamic properties as apparent molar volumes and apparent molar isentropic compressions. Infinite dilution values of these properties were determined using appropriate extrapolation procedures utilizing Debye–Hückel limiting law for electrolyte solutions. Apparent molar isobaric expansions at infinite dilutions were also evaluated from the temperature dependence of apparent molar volumes. The results were interpreted in terms of ionic liquid–water interactions.     

Li2S-P2S5体系电解质及其在全固态锂离子电池中的应用研究进展

全固态锂离子电池具有安全性能好、能量密度高、工作温区广等优点,被广泛应用于便携式电子设备。固态电解质是全固态锂离子电池的关键材料之一,其中的硫化物电解质具有离子电导率高、电化学窗口宽、晶界电阻低和易成膜等特点,被认为最有希望应用于全固态锂离子电池。本文综述了Li_2S-P_2S_5体系电解质的发展状况,包括固态电解质的制备、改性、表征以及电极/固态电解质之间的固-固界面的稳定兼容问题。本文还涉及了以Li_2S-P_2S_5为电解质的全固态锂离子电池性能的研究进展。     

Tetraalkylammonium Ions in Aqueous and Non-aqueous Solutions

Property data for tetraalkylammonium cations, [H(CH₂) _n ]₄N⁺, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series. The properties of the isolated ions increase linearly with the chain length. Molar enthalpies of formation of the gaseous and aqueous cations, and absolute standard molar enthalpies of hydration, are derived. Standard molar entropies of dissolution of several salts in water are obtained from their solubilities and enthalpies of solution. The molar entropies of the crystalline iodides of the first four members of the series then give the standard partial molar entropies of the aqueous cations and their molar entropies of hydration. The standard partial molar volumes in aqueous and non-aqueous solutions are quite linear with n and in non-aqueous solutions the molar volume hardly depends on the nature of the solvent. On transfer from water to non-aqueous solvents the volume of Me₄N⁺ suffers some shrinkage, that of Et₄N⁺ appears to be unaffected, but from Pr₄N⁺ onwards an increasing expansion takes place. This unexpected result is tentatively explained by hydrophobic intra-molecular association of pairs of alkyl chains in aqueous solutions, resulting in a tightening of the structure. The transfer of the R₄N⁺ cations from water into non-aqueous solvents is governed by a large positive entropy change, outweighing the smaller positive enthalpy change. The transport properties of the aqueous R₄N⁺ cations are non-linear with n. A major impediment to movement is thus the sticking of the water molecules to the ice-like hydrophobic hydration sheaths of the larger cations. The number of water molecules affected by the hydrophobic cations is open to widely differing estimates resulting from various approaches, and constitute an open issue.     

The partial molar heat capacities of glycine and glycylglycine in aqueous solution at elevated temperatures and atp = 10.0 MPa

Apparent molar heat capacities have been determined for aqueous solutions of glycine at temperatures from 352.09 K to 470.63 K and glycylglycine at temperatures from 352.09 K to 423.15 K. Both systems were investigated at a pressure of 10.0 MPa. Measurements were performed with a differential flow calorimeter that is capable of operation at temperatures  > 723 K and pressures to approximately 40.0 MPa. Partial molar heat capacities at infinite dilution have been calculated from apparent molar values and have been corrected for “relaxation" contributions. The reported partial molar heat capacity values for aqueous glycine and glycylglycine solutions have been modelled using the revised Helgeson, Kirkham, and Flowers semi-empirical equations of state. These models for solutions of glycine and glycylglycine in water have been compared with those previously reported in the literature.     

Lithium insertion into manganese dioxide polymorphs in aqueous electrolytes

The electrochemical behaviour of the spinel-like LiMn₂O₄ was studied in non-aqueous and aqueous saturated alkali nitrate electrolytes in comparison with the layered manganese dioxide δ-MnO₂. The results obtained by galvanostatic and cyclic voltammetry techniques showed that the insertion of Li⁺/e^– or H⁺/e^– depends on both the host lattice and the type of electrolyte. The spinel-like LiMn₂O₄ preferably allowed the insertion of Li⁺/e^– in non-aqueous and aqueous saturated LiNO₃ electrolytes, as observed from the similarity of the electrochemical behaviour in these electrolytes and the stability of the structure. This was explained by the presence of a three-dimensional network of vacant tetrahedral and half-filled octahedral sites in LiMn₂O₄, which guarantee high mobility of Li⁺ ions. The layered manganese dioxide could be inserted by Li⁺/e^– only in non-aqueous electrolytes. The work described herein was carried out at the Institut für Anorganische und Analytische Chemie, Technische Universit?t Berlin, Germany     

288.15, 298.15和308.15 K温度条件下甘氨酰甘氨酸在蔗糖-水混合溶剂中的体积性质研究

利用Anton Paar DMA55精密数字密度计测定了288.15, 298.15和308.15 K甘氨酰甘氨酸在蔗糖-水混合溶剂中的密度, 计算了甘氨酰甘氨酸的表观摩尔体积VΦ和极限偏摩尔体积 , 得到了其由纯水溶剂转移至混合溶剂中的迁移偏摩尔体积Δtrs 和理论水化数Nh．根据共球交盖模型, 讨论了迁移偏摩尔体积和水化数的变化规律．结果表明, 甘氨酰甘氨酸带电中心与蔗糖之间的结构相互作用对其迁移体积有正贡献, 且占主导地位．甘氨酰甘氨酸的迁移偏摩尔体积为正值, 且随着蔗糖浓度的增大而增大; 理论水化数随温度升高、蔗糖浓度的增大而减小; 温度升高, 极限偏摩尔体积增大, 迁移偏摩尔体积变化很小．     

Thermodynamics of concentrated electrolyte mixtures. II. Densities and compressibilities of aqueous NaCl−CaCl2 at 25 °C

Densities and ultrasonic velocities of NaCl–CaCl₂ aqueous mixtures at 25 °C have been measured for the ionic strength range I=0.30–20.0. Where NaCl solubility permitted, both properties were measured over the range of compositions from pure NaCl to pure CaCl₂ at constant I. Apparent molar volumes and apparent molar compressibilities of the mixtures were calculated. The Pitzer form of the specific interaction theory is used to predict the properties of the binary mixtures from the properties of the single salt solutions. It provides a good fit over the full range of ionic strength for apparent molar volumes but a much inferior fit for compressibilities. It is also clear that in the high ionic strength range, explicit mixing parameters must be included for an excellent fit.     

Relative partial molar enthalpies and apparent molar volumes of dipeptides in aqueous solution

Enthalpies of dilution at 25°C of aqueous solutions of the dipeptides glycylglycine, glycylalanine and alanylalanine have been determined and used to calculate the partial molar enthalpies of the solvent water in the solutions. The partial molar volumes of these dipeptides are also reported. The results are discussed in terms of the likely solute-solvent interactions.     

Thermodynamic investigations on derivatives of pyrimidine nucleic acid bases: Joint use of calorimetric, volumetric and structural data for the description of properties of pyrimidine nucleic acid bases and their derivatives

The experimental enthalpies of solution Δ_solH_m^∞, van’t Hoff enthalpies of sublimation Δ_s^gH_m⁰ of solid compounds, partial molar volumes V₂⁰, and partial molar heat capacities C_p,2⁰ of aqueous solutions of pyrimidine nucleic acid bases and their derivatives, determined previously and collected here, are discussed in terms of calculated structural parameters. Relations have been established between the calorimetric and volumetric properties. Correlations have been developed to relate both the enthalpies of solvation and the partial molar heat capacities to the polar and apolar parts of the accessible molecular surface areas.