计算液态混合物内能和内压的统计热力学理论

假定二元液态混合物分子间的相互作用势能可以表示成多体相互作用势能的和,分子间的力为短程力,相互作用势能只与分子间的相对距离有关.利用分布函数理论导出了二元液态混合物的过剩内能和内压的公式.二元液态混合物的过剩内能和内压可以表示成体积的幂级数形式,其中的系数可以用多体相互作用势和多体径向分布函数表出.讨论了单元液体的内压和过剩内能的表达式,在两种特殊情形下,过剩内能和内压的表达式分别与Egelstaff的微扰论结果及Frank的实验结果具有相同的形式.讨论了二元混合物内压和内能的两个特例,其一,在特殊情形下,给出了混合液体过剩内能的混合规则的一个证明.其二,给出的二元混合物的过剩内能和内压的表达式与Frank的实验结果具有相同的形式.     

低密度溶液中溶剂的重组织性质

分析了溶液的微观结构,结果表明,单个溶质粒子影响其周围的溶剂的结构,溶质粒子间的相互作用也将影响溶剂的结构,溶质对溶剂结构的影响称作溶剂的重组织.提出了二阶重组织能及二阶重组织熵等概念,可以描述在两个溶质粒子发生碰撞时对其周围溶剂结构的影响.利用二元系的集团展开理论,给出了溶剂的一阶、二阶重组织能和重组织熵的表达式.统计热力学分析给出了溶剂-溶剂径向分布函数与溶质和溶剂化学势之间的关系,给出了无限稀溶液模型是否成立的宏观判据.提出的理论可用于低密度的二元溶液.     

稀溶液正则系综的计算机模拟——核酸硷基腺嘌呤溶液的热力学量的蒙特卡罗计算

本文根据正则系综(T,V,N)的统计力学的蒙特卡罗方法,提出了在溶剂化过程中由于溶质分子和溶剂分子相互作用而引起正则系综中亥姆霍兹自由能(功函)A 变化的理论计算。并通过改进的分子间相互作用势,对核酸硷基腺嘌呤稀溶液进行蒙特卡罗模拟处理,求得在溶剂化过程中由于腺嘌呤分子与水分子相互作用而引起亥姆霍兹自由能(功函)、热焓、内能和构型熵的变化,以及包括溶剂分子间(水分子间)、溶质分子、溶剂分子之间相互作用总能量的正则平均。     

稀溶液中溶剂的化学势及其在依数性上的应用

长期以来,稀溶液中溶剂A的化学势为μA（1）=μ^＊A（1）＋RTlnxA,溶质B的化学势为μB（溶质）=μ^ΞB（溶质）＋RTln（bB／b^Ξ）,两式使用了不同的组成变量：溶剂的摩尔分数xA,溶质的质量摩尔浓度bB。按规定,溶液的组成变量应选用bB,故本文介绍了导出理想稀溶液中μA（1）=μ^＊A（1）-RTMA∑BbB的方法,并从此式出发推导出稀溶液的依数性。     

从拉乌尔定律和亨利定律看恒沸溶液

气液平衡是理论教学和实际生产中的重要内容。本文从微观本质讨论理论教学中的拉乌尔定律和亨利定律以及实际生产中的恒沸溶液之间的关系和区别。溶剂-溶剂、溶剂-溶质和溶质-溶质之间相互作用的不同导致两个定律仅适用于稀溶液。这些相互作用通过物质的量分数调节溶剂和溶质的表观蒸气压,当二者的表观蒸气压相等时,则产生了恒沸溶液。     

液体的内压和内能的统计热力学理论

利用分布函数理论导出了液体的内能和内压公式.液体的内压和过剩内能可以表示成体积的幂级数形式,其中的系数可以用多体相互作用势和多体径向分布函数表出,它们仅仅与温度有关.讨论了液体仅存在第n次多体相互作用势情形的内压和过剩内能的表达式,结果与Egelstaff的微扰理论结果具有相同的形式,不仅给出了相应参数的表达式而且适用于多体相互作用较强的情形.定义了物性参数α(T)和m,得到的液体过剩内能和内压的表达式与Frank实验结果具有相同的形式,其结果不仅给出了参数α(T)和m的表达式,而且指出了Frank的过剩内能和内压公式只适用于参数α(T)和m与体积无关的液体.     

丙氨酸在蔗糖-水混合溶剂中的焓对相互作用

利用LKB2277生物活性检测仪测定了298.15 K时丙氨酸分别在不同组成的蔗糖- 水混合溶剂中的稀释焓,利用McMillan-Mayer理论,计算了丙氨酸在不同组成的蔗 糖-水混合溶剂中的焓对相互作用系数h_2,并与其在葡萄糖-水混合溶剂中的焓对 相互作用系数h_2进行了比较。结果表明,丙氨酸的h_2分别在葡萄糖和蔗糖的摩尔 分数为0.1009和0.05843处出现极大值,极值点位置的不同与糖分子所含羟基数目 的多少有关,根据溶质-溶质相互作用和溶质-溶剂相互作用对结果进行了解释。     

甲酰胺、乙酰胺、尿素在两种极性非水溶剂中的体积性质

以尿素、甲酰胺和乙酰胺为溶质,二甲基甲酰胺和二甲基亚砜为溶剂;或以二甲基甲酰胺、二甲基亚砜为溶质,以甲酰胺为溶剂,通过测定溶液在２９８．１５Ｋ下的密度数据,求得了溶质的表观摩尔体积以及与溶质－溶质相互作用相关的体积第二维里系数．利用定标粒子理论讨论了溶质分子的几何体积、溶质－溶剂相互作用对溶质偏摩尔体积的影响,结果表明,溶质的溶剂化与溶质－溶质相互作用的体积效应呈相反的变化趋势     

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.     

I>D-甘露醇在正丙醇和异丙醇水溶液中的体积性质

使用石英振荡管密度计精确测定了298.15 K温度下不同浓度的甘露醇-正丙醇-水和甘露醇-异丙醇-水三元溶液的密度. 计算了甘露醇的表观摩尔体积V_Φ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. 结果表明, 正丙醇在溶液中对甘露醇体积性质的影响较异丙醇显著. 从溶质-溶剂分子间相互作用及丙醇同分异构体中羟基位置的不同对体积性质的变化规律进行了讨论.     

Thermodynamic studies of binary methanol and ethanol solutions of 1-dodecanol and 1-tetradecanol at 25°C

The osmotic coefficients of binary methanol and ethanol solutions of 1-dodecanol and 1-tetradecanol wer measured at 25°C up to 8 mol-kg^–1 in methanol and 5.5 mol-kg^–1 in ethanol. The activity coefficients of the solute were calculated from Bjerrum's relation. From the osmotic and activity coeficients the excess Gibbs energies of solution as well as the respective partial molar functions of solute and solvent and the virial pair interaction coefficients for the excess Gibbs energies were calculated. In addition, the difference in the Gibbs energy of solvation for the solvent in solution relative to the pure solvent was calculated, as well as the partial molar volumes and excess partial molar volumes of solutes at infinite dilution, and the coefficients of pairwise contributions to the excess volume were determined. The thermodynamic parameters obtained are discussed on the basis of solute-solvent and solute-solute interactions.     

二元体系C6H5CH3-DMF在293.15 K时的体积性质

利用Anton Paar DMA4500振动管密度计测量了293.15 K时二元体系甲苯-N,N-二甲基甲酰胺(C6H5CH3-DMF)在C6H5CH3(摩尔分数0~1)中的溶液密度, 利用最小二乘法关联了溶液密度与组成的函数关系, 关联精度为±0.005 kg/m3. 通过密度数据分别计算了二元体系中C6H5CH3和DMF的表观摩尔体积, 并利用非线性最小二乘拟合法, 分别拟合得到了优化的C6H5CH3和DMF的表观摩尔体积和摩尔分数的函数关系, 以及C6H5CH3和DMF的表观摩尔体积和质量分数的函数关系. 通过对函数关系的极限运算得到了C6H5CH3和DMF的极限偏摩尔体积、标准偏摩尔体积和摩尔体积. 还计算了不同组分下体系的超额摩尔体积, 数据可用四参数Redlich-Kister方程关联拟合得到方程系数. 计算关联了C6H5CH3和DMF的超额偏摩尔体积与摩尔分数的关系. 由三参数多项式极限法得到组分的极限超额偏摩尔体积值与Redlich-Kister系数法得到的值在误差范围内一致.     

Excess and partial excess molar volumes of 1,4-dichlorobutane with butanols at 25 and 40°C

From density measurements over the whole composition range at 25 and 40°C excess molar volumes for binary mixtures of 1,4-dichlorobutane with l-butanol, 2-butanol, 2-methyl-l-propanol or 2-methyl-2-propanol are calculated. V^E results were fitted by the method of least squares to a smoothing equation. Excess partial molar volumes and limiting excess partial molar volumes at 25° are also calculated.     

Direct Evaluation of Partial Molar Volumes of Binary Solutions of Dimethyl Sulfoxide with Ethyl Acrylate,Butyl Acrylate,Methyl Methacrylate and Styrene

The Tikhonov regularization is applied to convert specific molar volume data of binary solutions of dimethyl sulfoxide with a number of acrylates and with styrene into their second- and first-partial derivatives with respect to mole fraction under constant temperature and pressure. Generalized Cross Validation is used to guide the selection of the regularization parameter that keeps noise amplification under control. The resulting first derivative is then used to compute the partial molar volumes. These are compared against that obtained by the traditional method of least-squares fitting of excess molar volumes. Some of the advantages of the current approach and possible extension to other partial molar quantities are briefly discussed.     

Excess Molar Volumes and Partial Molar Volumes for Binary Mixtures of Water With 1,2-Ethanediol, 1,2-Propanediol,and 1,2-Butanediol at 293.15, 303.15 and 313.15 K

Abstract

From dilatometric method at 293.15,303,15, and 313.15K for binary mixtures of water and 1,2-alkane diols, the excess molar volumes, V^E and the partial molar volumes, V _i of both components at 293.15 K have been obtained as a function of mixtures composition. Excess molar volumes were calculated and correlated by a Redlich-Kister type function in terms of mole fraction. The partial molar volumes have been extrapolated to zero concentration to obtain the limiting values at infinite dilution, V ⁰ _i . All mixtures showed negative values and decreases with the chain length of diols. The values become less negative with increasing temperature. The results are explained in terms of dissociation of the self-associated diol molecules and the formation of aggregates between unlike molecules.     

Volumetric and compressibility studies for (L-arginine + D-maltose monohydrate + water) system in the temperature range of (298.15 to 308.15) K

The density and speed of sound of L-arginine (0.025–0.2 mol kg^?1) in aqueous + D-maltose (0–6 mass% of maltose in water) were obtained at temperatures of (298.15, 303.15 and 308.15) K. The apparent molar volume, limiting apparent molar volume, transfer volume, as well as apparent molar compressibility, limiting apparent molar compressibility, transfer compressibility, pair and triple interaction coefficients, partial molar expansibilities, coefficient of thermal expansion and also the hydration number, were calculated using the experimental density and speed of sound values. The results have been discussed in terms of solute–solute and solute–solvent interactions in these systems. Solute–solvent (hydrophilic–ionic group and hydrophilic–hydrophilic group) interactions were found to be dominating over solute–solute (hydrophobic–hydrophilic group) interactions in the solution, which increases with increase in maltose concentration.     

Thermodynamics of mixtures with strongly negative deviations from Raoult’s law: Part 5. Excess molar volumes at 298.15 K for 1-alkanols+dipropylamine systems: characterization in terms of the ERAS model

Excess molar volumes, V_m^E, at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with dipropylamine are reported from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the whole mole fraction range, indicating strong interactions between unlike molecules, which are more important for the system involving methanol, characterized by the most negative V_m^E. For the remainder mixtures, V_m^E at equimolar composition, is approximately constant. The V_m^E curves are nearly symmetrical.

V_m^E and excess molar enthalpies, H_m^E, of the mixtures studied are consistently described by the ERAS model. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in the methanol+dipropylamine system.     

Thermodynamic Properties of Multicomponent Liquid Mixtures

Considering a ternary liquid mixture to be made up of three binary mixtures, by means of cell model using Sutherland type potential function for pair interaction between molecules, a statistical theory for binary liquid mixtures has been extended for ternary systems. In the light of above extension, excess volume ( V E ), excess energy ( E E ) and excess entropy ( TS E ) have been computed for three binary (benzene + cyclohexane, benzene + chlorobenzene and cyclohexane + chlorobenzene) and the resultant ternary system (benzene + cyclohexane + chlorobenzene) at 298.15 K. All the above mentioned excess properties have been computed from the data of ultrasonic velocity and density only.     

On the Determination of Partial Molar Volumes,Partial Molar Refractions,Mean Electronic Polarizabilities and Effective Molecular Radii from Dilute Multi-component Data alone using Response Surface Models

A quaternary system consisting of three solutes, namely ethanol, diethylene glycol (DEG) and triethylene glycol (TEG) in benzene at 298.15 K and 1.0125 × 10⁵ Pa was studied. An experimental design in the range of concentration 0.006 < x _solute−i < 0.023 was explored, optimizing the metric distance among the solutes to avoid clustering. On-line simultaneous experimental measurements using a densitometer and a refractometer were utilized to measure bulk solution density and bulk refractive index, respectively. Response surface models describing the total molar volume and total molar refraction were employed to determine the partial molar volumes and the partial molar refractions of each solute from the dilute multi-component data alone. Neither densities nor refractive indices of any of the pure components were used and no binary information was required for the analysis. Definitions for the mean electronic polarizability and the effective molecular radius of a solute based on the partial molar refraction were introduced. Subsequently, the mean electronic polarizabilities and the effective molecular radii for each solute in multi-component solutions, as well as the solvent were determined. The results obtained for the partial molar volumes, partial molar refractions, electronic polarizabilities and the effective molecular radii were in good agreement with those obtained from independent binary experiments as well as those from literature binary data.     

Excess partial molar enthalpies,entropies, Gibbs energies,and volumes in aqueous dimethylsulfoxide

The excess partial molar enthalpies, the vapor pressures, and the densities of dimethylsulfoxide (DMSO)–H₂O mixtures were measured and the excess partial molar Gibbs energies and the partial molar volumes were calculated for DMSO and for H₂O. The values of the excess partial molar Gibbs energies for both DMSO and H₂O are negative over the entire composition range. The results for the water-rich region indicated that the presence of DMSO enhances the hydrogen bond network of H₂O. Unlike monohydric alcohols, however, the solute-solute interaction is repulsive in terms of the Gibbs energy. This was a result of the fact that the repulsion among solutes in terms of enthalpy surpassed the attraction in terms of entropy. The data in the DMSO-rich region suggest that DMSO molecules form clusters which protect H₂O molecules from exposure to the nonpolar alkyl groups of DMSO.