二组分平衡体系的T-x相图

主要从3个方面介绍了二组分平衡体系的T-x相图。一是简单相图的介绍;二是简单相图的组合;三是实际体系复杂相图的认识。从而可以让学生理解和掌握相平衡中的二组分体系的气-液、液-液和液-固平衡的T-x相图,并为实际应用打下良好的基础。     

甲酸—乙酸—水—氯化镁体系汽液平衡中的盐效应

采用Otsuiki-Williams式汽液平衡仪在9.866×10~4Pa下测定了甲酸-水、乙酸-水、甲酸-乙酸、甲酸-乙酸-水体系无盐和加氯化镁后各体系的汽液平衡数据,绘制了两组分和三组分体系相图。相图表明氯化镁有明显的盐效应。     

二组分体系的相图及其相图边界理论

主要探讨了二组分体系的相图,如气-液相图和液-固相图,总结了二组分相图的分类、绘制及相图分析,这有利于理解和掌握二组分相图的基本规律。并简单介绍了相图边界理论,扩展了相图的热力学研究。     

磷脂中胆碱(PC)、乙醇胺(PE)和水(H2O)三相相图的研究

利用X射线衍射测定了磷脂中胆碱（PC），乙醇胺（PE）和H2O不同含量时的X射线衍射峰，初步绘制出了三相相图的轮廓，为三磷脂中相相图的进一步研究和从磷脂的混合体系中分离出纯的胆碱奠定了基础。     

辽河减压渣油-正戊烷体系的相态变化特性

利用RUSKA公司无汞PVT装置,对辽河减压渣油-正戊烷体系的相行为进行了实验观察,测定了辽河渣油-正戊烷体系相态变化的边界线,如液-液相分界线、液-液-气三相区分界线等,绘制了体系的p-t相图;在140℃～190℃,1.0MPa～10.0MPa,溶剂质量比为3.0～6.0的条件下,对体系相特性的变化进行了分析和讨论。在实验条件下,辽河渣油-戊烷体系的p-t相图可以划分为四个区域:单一液相区、液-液两相区、液-液-气三相区、气-液两相区;溶剂质量比对由单一液相区转变为液-液两相分相压力的影响显著,溶剂质量比越大,分相压力越大;但溶剂质量比对液-液-气三相区影响不大。确定了辽河渣油-正戊烷体系溶剂脱沥青过程适宜的操作区域。     

EuI_2-KI二元系相图

用差热分析和X射线衍射的方法研究了EuI2 KI二元体系在 3× 10 - 4 Pa压强下的低压相图。实测相图显示 ,该二元体系存在一个同份熔化化合物KEu2 I5 和一个异份熔化化合物K4EuI6 ,两个三相共晶点的温度和成分分别为 737K ,2 0 %KI和 713K ,6 0 %KI。X射线粉末衍射的结果表明KEu2 I5 的晶体结构参数与文献数据十分吻合。本文还讨论了实测相图的误差来源 ,并由相图计算出EuI2 的熔化热为2 10 12J·mol- 1 。     

0℃时REI3-CS(NH2)2-H2O(RE=Eu,Yb)的相图及REI3·2CS(NH2)2·10H2O的合成与表征

采用湿渣法研究了0℃时REI3 CS(NH2)2 H2O(RE=Eu,Yb)的三元体系相平衡,绘制了该体系的等温溶解度相图,相图分析结果表明,该体系中有组成为REI3·2CS(NH2)2·10H2O的新配合物生成,该配合物在相图中的结晶区较小,且异组成溶解于水。对所得配合物组成进行的化学分析结果与相图分析一致,采用X射线粉末衍射分析对所得配合物的物相进行了鉴定,采用红外光谱、差热 热重分析法表征了配合物的结构和热稳定性,结果表明:配合物中稀土离子与H2O和CS(NH2)2中的S作用。     

用DTA法绘制Pb-Sn相图

相图在矿物冶炼、玻璃陶瓷、合金材料的研究,以及物质的分离、提纯、分析等方面,有着极为广泛的应用,因此,绘制一个较完整的相图是非常重要的。在二组分凝聚体系中,对仅具有简单低共熔混合物的二组分体系来说,采用步冷曲线方法绘制相图,无疑是一个简便、直观和可靠的方法。     

对应关系定理及其推论在温度、压强、组成均可独立变化的多元相图中的应用

本文将文献[3]所导出的对应关系定理应用于温度T、压强P和组成x_i均可独立交化的多元相图,得到适用于这类相图的六条推论,讨论了这类相图中两个紧邻相区中的不同相的总数Φ、紧邻相区的相边界的维数R_1以及两个紧邻相区中共同具有的相的数目△Φ的变化范围和规律。同时又讨论了这类相图中两个紧邻相区的边界的维数R_1~′和Ri、△Φ的关系。根据所有这些规律和关系具体地分析了二元和三元体系的P-T-x相图中紧邻相区及其边界的关系。     

改良合成复体法制作水盐三组分体系相图的实验研究

前言水盐三组分体系相图的制作方法颇多,常用的有干渣法、湿渣法、冷却法及合成复体法等。这些方法虽各有其特点,但一般说来都较繁复费时,常常既要测定平衡体系中饱和溶液的组成,且要测定平衡体系的固相组成。 E.L.Heric曾提出一种只需测定平衡体系中饱和溶液的水含量,便可制作出水盐三组分体系相图的方法,颇具特色。其原理是:若以a、b、c分别表示试样中水、盐Ⅰ和盐Ⅱ的重量百分数;以a_s,b_s,c_s分别表示已达溶解平衡的饱和溶液中的水,盐Ⅰ和盐Ⅱ的重量百分     

Carbon dioxide-water phase equilibria results from the Wong-Sandler combining rules

A model based upon the Peng-Robinson equation of state with the Wong-Sandler mixture combining rule (W-S MCR) can correlate phase equilibria in CO₂ + H₂O. The W-S MCR requires two energy parameters for liquid behavior and one interaction parameter for gas behavior, k_ij. In this paper, we present expressions for the energy parameters which cover a wide temperature range, and we use a new procedure to obtain k_ij by relating it to experimental cross second virial coefficients, B_ij. The three-phase pressures calculated for this system using our proposed model agree with the experimental data within a fraction of 1 bar. The correlated phase behavior of CO₂ + H₂O appears to be accurate over the ranges 1 – 1000 bar and 298.15–623.15 K. The proposed model also confirms the advantage of using the W-S MCR for phase equilibrium calculations.     

The line tension and the generalized Young equation: the choice of dividing surface

Using Gibbs method of dividing surfaces, the condition of equilibrium of a sessile drop on a flat non-deformable solid substrate is investigated. The dependence of the line tension on the curvature radius of the dividing three-phase contact line is found. It has been derived a relationship between the partial derivative of the line tension with respect to the curvature radius of the three-phase contact line (which stands in the generalized Young equation) and the total derivative of the line tension with respect to the same radius along the equilibrium states. Various approximated formulas of the generalized Young equation used in the literature are analyzed.     

物理化学课程中相平衡理论的教学策略

针对物理化学相平衡章节体系多变、知识点繁多、相图抽象等问题提出了一套系统的教学策略。首先对相平衡中的基本概念和定律进行论述,并强调重、难点;随后对章节知识点进行总结归纳,通过表格系统罗列相图的体系、相律、应用和术语;最后提出相图解读通行方法,并结合具体例子讲解这些方法、相律以及杠杆规则如何使用。     

The phase envelopes of alternative solvents (ionic liquid,CO2) and building blocks of biomass origin (lactic acid,propionic acid)

Solid–liquid, liquid–liquid and vapour–liquid equilibrium measurements for binary and ternary systems containing building blocks of biomass origin such as propionic acid, lactic acid and alternative solvents like carbon dioxide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid have been carried out at 313.15 K. The binary solid–liquid and liquid–liquid equilibrium measurements were performed at ambient pressure. The vapour–liquid equilibrium was studied in the range of pressure from 3.54 to 12 MPa while ternary systems were examined at 9, 10 and 12 MPa. The samples from the coexisting phases were taken and the compositions of both liquid and vapour phases were determined experimentally. The three-phase system was observed for lactic acid + ionic liquid + CO₂ as well. The achieved results were correlated using the Peng–Robinson equation of state with the Mathias–Klotz–Prausnitz mixing rule. The set of interaction parameters for the employed equations of state and the mixing rule for the investigated systems were obtained.     

Implications of the phase rule for capillary systems containing surfaces and three-phase contact lines with surface and linear constraint relations

The phase rule is generalized to heterogeneous systems with moderately curved surfaces and linear or line-phase boundaries. It will be shown that the number of degrees of freedom or variancef of a capillary sysem is, in general, larger than that predicted by the classical Gibbs' phase rule. Restrictions on the value off for capillary systems is intimately connected with the imposition of mechanical constraints like the Laplace and Young equations of capillarity. As a direct consequence, it may be shown that the variance for anr-component, three-phase solid-liquid-vapour system (i.e., a liquid drop on a solid surface) is different from that of anr-component, liquid-liquid-vapour system. This conclusion has important implications for the existence or possible existence of equation-of-state type relations.     

The line adsorption equation: the one-dimensional counterpart of the Gibbs adsorption equation

The thermodynamic development for multiphase contact lines is analogous to that for surfaces or interfaces. However, for one of the most important equations in surface thermodynamics, the Gibbs adsorption equation, the one-dimensional analogue is missing. This paper derives such an analogue, the line adsorption equation. Similarly to the Gibbs adsorption equation, the line adsorption equation is derived from Gibbsian thermodynamics. For a three-phase, three-component contact line system (e.g. an oil lens on the surface of an aqueous solution), the line concentrations (excesses) of two immiscible solvents can be made vanish by appropriately placing the dividing line. Consequently, the line concentration of the solute can be evaluated through the line tension change with the volume concentration of the solute. Such an evaluation provides information about molecular adsorption at the contact line, which is important in physical chemistry of lines, but difficult to obtain by any other means.     

Phenomenological description of transport properties of three-phase composites

The possibility is discussed of estimating the values of conductivity and dielectric permeability of three-phase composites using the modified mixing equation similar to the equation suggested earlier for two-phase systems. It is shown that the choice of theoretical mixing equation parameters for three-phase composites of the conductor–electrolyte–insulator type can be controversial; variants of solving this problem are suggested. According to the equation, three percolation thresholds can exist in this three-phase system; their position can be estimated on the basis of the maximum of dielectric permeability. The value of the maximum is determined by the ratio of conductivities of the conducting and dielectric phases. The equation can be extended to the case when interaction exists between the individual phases of the composite and a highly conducting layer is formed at the interface between these phases. The calculation of three-phase composites of the conductor–composite solid electrolyte–insulator type is calculated for the first time. It is shown that the mixing equation also allows calculating electric properties of composites in this case.     

Models of adsorption at a line of three-phase contact

Two model density distributions at a line of three-phase contact for which the adsorptions are readily calculated are analyzed. One of them provides a numerical illustration of a recently found surprising fact about the thermodynamics of adsorption at such contact lines. A form of the line analogue of the Gibbs adsorption equation is conjectured, and it is noted that the conjecture is in principle testable by computer simulation and by experiment.     

Modeling of three-phase vapor–liquid–liquid equilibria for a natural-gas system rich in nitrogen with the SRK and PC-SAFT EoS

In this work, we present the modeling of three-phase vapor–liquid–liquid equilibria for a mixture of natural gas (Hogback gas) containing high concentrations in nitrogen (51.8 mol%) with the SRK and PC-SAFT equations of state. The interest of studying this mixture is due to the experimental evidence of the occurrence of multiple equilibrium liquid phases for this mixture over certain ranges of temperature and pressure. The calculation of the multiphase equilibria was carried out by using an efficient numerical procedure based on the minimization of the system Gibbs energy and thermodynamic stability tests to find the most stable state of the system. The results of the calculated vapor–liquid–liquid equilibria (VLLE) show that the PC-SAFT equation of state predicts satisfactorily the phase behavior that experimentally exhibits this mixture, whereas the SRK equation of state predicts a three-phase region wider than the experimentally observed. The two-phase boundary for this mixture was also calculated through flash calculations, and the results showed that this mixture does not present any gas-liquid critical point.