Vapor pressure and activity of components of melts formed by manganese chloride and chlorides of alkaline-earth metals

The boiling points of melts were measured at different pressures over the melts for certain concentrations of components of the liquid phase in binary systems constituted by manganese chloride and chlorides of alkaline-earth metals. The temperature dependences of the saturated vapor pressure, normal boiling points, and enthalpies of evaporation were calculated. The concentration dependences of the thermodynamic activities of the components of four binary systems were analyzed.     

Applicability Limits of Calculation Methods for Estimating the Enthalpy of Vaporization of Organophosphorus Compounds

Quantitative relationships used today for calculating the enthalpies of vaporization of organophosphorus compounds are analyzed. The parameters of equations used in these calculations largely depend on specific structural features and are common for closely related compounds only. With various P(III) derivatives as examples, narrow ranges are distinguished in which the enthalpies of vaporization can be estimated from the boiling points using common relationships. The group contributions of phosphorus-containing fragments for calculations by the additive scheme are determined.     

Polynomial Dependence for the Calculation of Vaporization Enthalpies of Organophosphorus Compounds

Enthalpies of vaporization of organic phosphorus compounds are related to the normal-pressure boiling points through a polynomial dependence. Each class of organophosphorus compounds is characterized by its own specific parameters of the general dependence. The polynomial dependences may be used for the calculation of vaporization enthalpies of organophosphorus compounds with different modes of phosphorus coordination.     

Thermodynamic properties of ionic liquids-a cluster approach

We describe a method for calculating thermodynamic properties of ionic liquids by using standard quantum statistical thermodynamics as characterized by ab initio techniques. We review briefly how thermochemical properties for different sized clusters of ionic liquids are calculated by standard ab initio programs. The cluster partition functions allow one to calculate energies, enthalpies and Gibbs energies. Assuming that the ionic liquid exists exclusively as isolated ion-pairs in the gaseous phase and regarding the largest clusters as possible liquid structures, we could estimate vapor pressures, enthalpies of vaporization and entropies of vaporization. For possible boiling points it is shown how they vary with pressure.     

Physikalische und spektroskopische daten von trifluormethylselenol und derivaten

The characterization of the compounds CF₃SeX (X = H, Cl, Br, CN, CF₃, SeCF₃) is completed by the report of melting points, boiling points, enthalpies of vaporization and entropies of vaporization. Ultraviolet and mass spectra are presented and discussed. An improved synthesis for CF₃SeH is reported.     

饱和链烃图特征和热力学性质

本文讨论饱和链烃分子异构化和热力学性质之间的关系.首先利用图论方法引进描写分子支化度的α_N指数,该指数能分辨仅有微小结构差异的饱和链烃分子,给出支化结构的合理描述.在此基础上,得到了利用分子图特征参量计算饱和链烃热力学量(如:沸点、密度、生成焓、原子生成热、折射率和色谱保留指数等)的统一表达式.     

Heat capacity,saturation vapor pressure,and thermodynamic functions of ethyl esters of C<Subscript>3</Subscript>–C<Subscript>5</Subscript> and C<Subscript>18</Subscript> carboxylic acids

The heat capacities of ethyl propanoate (EPr), ethyl n-pentanoate (EPen), and ethyl n-octadecanoate (ethyl stearate, ESt) were measured by vacuum adiabatic calorimetry in the temperature range of 6 to 373 K. Triple point temperatures, fusion enthalpies and entropies, and purity of the samples of the sub-stances under study were determined. The saturation vapor pressures for EPr and EPen were determined by comparative ebulliometry in an atmospheric pressure range of 4.0 to 101.7 kPa. The normal boiling points and vaporization enthalpies vs. temperature were obtained. The standard thermodynamic functions (S, H, and G) were calculated for the condensed and ideal gas states on the basis of the experimental data. The vapor pressures of the atmospheric range were extrapolated to entire ranges of the liquid phases of EPr and EPen using the principle of corresponding states and the combined processing of pT parameters and low-temperature differences in the heat capacities of an ideal gas and liquid.     

Liquid–vapor phase equilibria and the thermodynamic properties of 2-methylpropanol–<Emphasis Type="Italic">n</Emphasis>-alkyl propanoate solutions

The boiling points of solutions of five binary systems are measured via ebulliometry in the pressure range of 2.05–103.3 kPa. Equilibrium vapor phase compositions, the values of the excess Gibbs energies, enthalpies, and entropies of solution of these systems are calculated. Patterns in the changes of phase equilibria and thermodynamic properties of solutions are established, depending on the compositions and temperatures of the systems. Liquid–vapor equilibria in the systems are described using the equations of Wilson and the NRTL (Non-Random Two-Liquid Model).     

The temperature dependences of saturated vapor pressures and heat capacities of some perfluoropolyethers

The borling temperatures of perfluoro-2,4,6,9,11,13-hexaoxy-n-tetradecane, perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane, and perfluoro-2,4,6,8,11,13,15,17,19,21-decaoxy-n-docosane were determined by comparative ebulliometry over the saturated vapor pressure range 6.2–101.6 kPa. The heat capacity of perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane was studied by adiabatic calorimetry over the temperature range 5.3–371.2 K. The densities of the substances at 296–338 K were measured in quartz pycnometers. The data obtained were used to calculate the normal boiling points, enthalpies of vaporization, critical parameters, and thermodynamic functions (entropy, enthalpy, and Gibbs energy) of the polyethers studied.     

改进的连接性指数用于链烷烃热力学性质与沸点研究

基于邻接矩阵和原子特征值qi，建立邻接指数^mQ,用^0Qr,^1Q与85种链烷烃的标准生成焓、标准生成自由能、标准熵和沸点关联，相关系数均在0.99以上，属于良好模型，与Randic指数的^mX比较，^mQ具有良好的性质相关性。     

二氯苯的蒸发焓和升华焓测定

在进行分子内非键合相互作用的热化学研究中,我们已用燃烧量热法测定了各种取代的氯代苯在凝聚态的标准生成焓。为了排除分子间的相互作用,以得到准确的气态生成焓,需要这些化合物的标准蒸发焓或升华焓。文献中这类数据不多,且相当一部分是用测量蒸气压随温度变化按Clapeyron-Clausius方程计算的,不如直接量热法准确。对高取代的氯代苯,由于蒸气压很低,实验困难,数据更缺。为此,我们用量热法测定了三个二氯苯异构体的蒸发焓和升华焓,并结合已有的文献数据,建立了氯代苯标准蒸发焓和升华焓与其沸点的线性关系,估算了其余未知的数据。     

Automatic simulated distillation of heavy petroleum fractions up to 800°C TBP by capillary gas chromatography. Part I: Possibilities and limits of the method

The characterization of heavy petroleum fractions is essential for the design and improvement of cracking plants converting heavy feedstock into valuable “white” products. Conventional simulated distillation methods using packed columns are unsuitable for this purposes, being limited to boiling points up to about 600°C. The method presented is able to cover a boiling points interval ranging from about 150°C up to around 800°C. It employs a short, nonpolar, highly thermostable capillary column routinely operated at temperatures around 430°C. The analytical system is based on a high temperature versions of a fully automatic, capillary dedicated gas chromatograph. The experimental data demonstrate that cold on-column injection is the sole sampling system suitable for such heavy compounds. The conversion of the retention times into boiling points, based on the use of low molecular weight polyethylenes, is extremely reliable, as demonstrated by the excellent retention time reproducibilities. The lower part (up to 550–600°C TBP) of the boiling point distribution curves of heavy petroleum fractions obtained on capillary columns fits well with the corresponding distribution curves based on packed column data. For the petroleum fractions fully eluted from the column the quantitative results obtained either using internal standards or by direct processing of the elution curves are in excellent agreement (less than 0.3 weight% differences). The method has been applied to the determination of the true boiling points corresponding to short path vacuum distillation (DISTACT) cut points over 300°C.     

Substituent effects on the energetics and aromaticity of aminomethylbenzoic acids

The standard (p0 = 0.1 MPa) molar enthalpies of combustion of six aminomethylbenzoic acids were measured at T = 298.15 K by static bomb calorimetry. With these values, the standard molar enthalpies of formation in the crystalline state were obtained. Combining these results with the standard molar enthalpies of sublimation, the standard molar enthalpies of formation in the gaseous phase were derived. For the 10 possible isomers, the obtained experimental results were compared to and correlated with the relative stability obtained by ab initio calculations at the B3LYP/6-311++G(d,p) level of theory. Seeking a better understanding of the aromatic behavior and energetics of aminomethylbenzoic acids in the gas phase, calculations of NICS values, HOMA indices, and dihedral angles between the aromatic carbon and the amino group, Phi(Ar-NHH), were also performed computationally. The significant differences observed in the energetics, as well as in the NICS values, HOMA indices, and Phi(Ar-NHH) dihedral angles for these 10 isomers suggest a strong dependency on the identity and relative position of the three substituents on the benzene ring. This study points out a marked tendency for a decrease of the ring aromaticity, accompanied by an increase in the respective system stability, as the conjugation between the substituents becomes more extensive.     

Prediction of vapor pressures and enthalpies of vaporization of organic compounds from the normal boiling point temperature

Recently, our Laboratory proposed a model for the prediction of vapor pressures of organic compounds that requires only the knowledge of the normal boiling point of the compound involved, and a compound specific K_f for which generalized expressions for several classes of organic compounds as functions of the normal boiling point and the molecular weight were developed.In this work our model is compared with the one proposed in Lyman's book, which is similar to our model but uses different K_f values. The results indicate that our model provides very satisfactory results in the temperature range from the melting up to the normal boiling point and up to the critical, where no hydrogen-bonding is involved. Also, it is proven that the accuracy of our model is much better than that proposed by Lyman, especially for the high molecular weight compounds.Finally, our model is used for the prediction of enthalpies of vaporization at the normal boiling point. Excellent results are obtained that are comparable or better than those obtained with two recommended models in “The Properties of Gases and Liquids” book, where the latter, however, require as input information except from the normal boiling point the critical properties of the compound involved as well.     

Estimation of boiling and melting points of light,heavy and complex hydrocarbons by means of a modified group vector space method

A modified group vector space (GVS) method was developed for estimating the normal boiling points and melting points of alkanes, alkenes, alkynes, and cyclic and aromatic hydrocarbons including their isomers. The present method, based on group contributions as well as topological contributions, can represent the normal boiling points of isomeric compounds accurately. The group parameters for the modified GVS method were obtained from the correlation of the boiling and melting points of 1115 hydrocarbons.     

Determination of low-melting alloys in the ternary reciprocal system Na,K‖Br,WO<Subscript>4</Subscript>

The ternary reciprocal system Na,K‖Br,WO₄ was studied by differential thermal analysis. The compositions and melting points of the alloys corresponding to invariant equilibrium points were determined, and the enthalpies of melting of eutectic mixtures were measured. Phase equilibria in systems were described, and the fields of crystallizing phases were delineated.     

乙烷氟氯衍生物常压沸点与结构之间的定量关系

构建了一个新的自相关拓扑指数0 Lk,并研究了乙烷氟氯衍生物的常压沸点Tb 与其基团零价自相关指数0 Lk 之间的定量关系 ,给出了相关方程 ,相关系数 (R =0 .96 33)为良好级 .估算的 36个乙烷氟氯衍生物的常压沸点与实验值相吻合 .还对一些没有常压沸点的乙烷氟氯衍生物进行了预测 ,预测的沸点数据指出CHF2 CHF2是CFC3 可能的代用品     

Nitrous oxide: Saturation properties and the phase diagram

The experimental values of the coordinates of the triple point and of the critical point of nitrous oxide registered in the literature were assessed and those judged as most reliable have been selected. Empirical equations have been found for the vapour pressure, sublimation and fusion curves. The virial coefficients and saturation properties as functions of temperature along the equilibrium curves are described by reduced equations. They were used in arriving at the molar enthalpies at the triple point and the normal boiling temperature. Equations for the sublimation and fusion curves resulting from the exactly integrated Clapeyron equation compare favourably with the results from the empirical treatment and the experimental data.     

Isobars of the boiling temperature and isotherms of excess thermodynamic functions of isobutanol-alkyl ketone solutions

The boiling temperatures for solutions of five binary systems are measured via ebulliometry in the pressure range of 5.333–101.3 kPa. The isotherms constructed for the pressure of saturated vapor serve as the base for computing the compositions of equilibrium vapor phases of the systems. The excess Gibbs energies, enthalpies, and entropies of solutions are computed from the data on liquid-vapor equilibrium. The laws of changes in the phase equilibria and thermodynamic properties of solutions are determined depending on the composition and temperature of the systems. The vapor-liquid equilibrium of the systems is described by Wilson and NRTL equations.