Thermodynamic properties of saturated and compressed liquid difluorochloromethane

In an isochoric study the thermodynamic behaviour of liquid difluorochloromethane was experimentally investigated. New measurements of (p, ?, T) have been carried out at densities from 0.83 to 1.36 g·cm^?3 (reduced densities from 1.6 to 2.7) and pressures up to 60 MPa. In addition new results for the vapour pressure of liquid difluorochloromethane are reported at temperatures from 312 to 369 K. Saturated liquid densities were obtained from the extrapolation of the isochoric results to the vapour-liquid coexistence curve.     

Treatment of excess thermodynamic quantities for liquid mixtures

Thermodynamic data on mixtures of liquids are usually expressed as excess quantitiesY ^EX and analyzed with the Redlich-Kister equation. This approach can in some cases be misleading and hide strong interactions at low concentrations. In agreement with the original statement of Redlich and Kister, it is therefore better to plot such data asY ^EX/X ₂(1-X ₂). This quantity, which is directly related to the apparent molar quantities of both components, is often a more useful quantity and has just as much a thermodynamic significance asY ^EX.     

The thermodynamic stability of clathrate hydrate. Encaging non-spherical propane molecules

The thermodynamic stability of a clathrate hydrate encaging non-spherical molecules has been investigated by examining the free energy of cage occupancy. In the present study, a generalized van der Waals and Platteeuw theory is extended to treat the rotational motion of guest molecules in clathrate hydrate cages. The vibrational free energy of both guest and host molecules is divided into harmonic and anharmonic contributions. The anharmonic free energy associated with the non-spherical nature of the guest molecules is evaluated as a perturbation from the spherical guest. Predicted thermodynamic properties are compared with measured values. It is shown that this anharmonic contribution is important in the free energy of the hindered rotation of the guests.     

Evaluation of thermodynamic quantities etc. in the cation exchange of Mg2+ from magnesium saturated bentonite and vermiculite

Summary Cation exchange studies have been carried out between Mg-saturated bentonite and vermiculite and a number of monovalent electrolytes. According to the distribution and selectivity coefficients the cations are preferred in the order: Li Na43)₄N (C₂H₅)₄N for betonite and Li < Na < NH₄ < K < Rb < Cs < H and (C₂H₅)₄N < (CH₃)₄N for vermiculite. The selectivity coefficient of H⁺ is found to be much greater than other inorganic ions.TheG-values of the cation exchange reaction have been calculated by an equation ofBarrer. The experimental data were analyzed by the theoretical approach ofPauley too.     

硝基甲苯异构体的液晶溶液热力学性质的色谱法研究

本文用气液色谱方法研究了o-, m-, p-硝基甲苯三种异构体在双(对己氧基苯甲酸)对苯二酚酯(PBH~xB)和双(对庚氧基苯甲酸)对苯二酚酯(PBH~pB)两种向列液晶固定液中无限稀薄条件下的活度系数, 进而求得了超额焓, 超额自由能和超额熵, 同时得到溶解焓和溶解熵, 并对结果进行了分析和讨论。     

The thermodynamic behaviour of Sm3+-doped LiKSO4 crystals

The influence of the point defects introduced by means of Sm³⁺ on the thermal properties of LiKSO₄ crystals was studied in the vicinity of the high-temperature phase at 708 and 940 K. The temperature dependence of the specific heat was found to vary monotonously with the Sm³⁺content, while the first transition temperature was unchanged. The change in the value of the specific heat was attributed to the correlation between the defect-defect interaction and the presence of internal local strain generated inside the crystal. The variation of the excess specific heat with the reduced temperature obeys the 3d Ising model.     

Prediction of multicomponent liquid adsorption using excess quantities I. Statistical thermodynamic derivation of the basic equation of excess formalism

The utilization of excess quantities as the basis of a thermodynamic approach can simplify the prediction of multicomponent liquid adsorption from binary data. From statistical thermodynamics, the fundamental equation is derived for the prediction of ternary or higher order data from adsorption data for the constituent binary mixtures. An additive expression is obtained for the double Gibbs free excess energies, valid for adsorption on liquid mixture/air interfaces as well as liquid mixture/solid interfaces.     

Thermodynamic modeling of saturated liquid compositions and densities for asymmetric binary systems composed of carbon dioxide,alkanes and alkanols

The present study mainly focuses on the phase behavior modeling of asymmetric binary mixtures. Capability of different mixing rules and volume shift in the prediction of solubility and saturated liquid density has been investigated. Different binary systems of (alkane + alkanol), (alkane + alkane), (carbon dioxide + alkanol), and (carbon dioxide + alkane) are considered. The composition and the density of saturated liquid phase at equilibrium condition are the properties of interest. Considering composition and saturated liquid density of different binary systems, three main objectives are investigated. First, three different mixing rules (one-parameter, two parameters and Wong–Sandler) coupled with Peng–Robinson equation of state were used to predict the equilibrium properties. The Wong–Sandler mixing rule was utilized with the non-random two-liquid (NRTL) model. Binary interaction coefficients and NRTL model parameters were optimized using the Levenberg–Marquardt algorithm. Second, to improve the density prediction, the volume translation technique was applied. Finally, Two different approaches were considered to tune the equation of state; regression of experimental equilibrium compositions and densities separately and spontaneously. The modeling results show that there is no superior mixing rule which can predict the equilibrium properties for different systems. Two-parameter and Wong–Sandler mixing rule show promoting results compared to one-parameter mixing rule. Wong–Sandler mixing rule in spite of its improvement in the prediction of saturated liquid compositions is unable to predict the liquid densities with sufficient accuracy.     

High-performance liquid chromatography of amino acids, peptides and proteins. CXV. Thermodynamic behaviour of peptides in reversed-phase chromatography.

The thermodynamic behaviour of three peptides, bombesin, beta-endorphin and glucagon, was studied under reversed-phase high-performance liquid chromatographic conditions. Experimental data related to the interactive surface contact area (S values) and solute affinity (log k0) were derived over a range of temperatures between 5 and 85 degrees C. These experimental conditions allowed changes in the secondary structure of the solute to be monitored. The influence of the nature of the stationary phase ligand on the relative conformational stability of the three peptides was analysed by acquiring data with n-octadecyl silica (C18) and n-butyl silica (C4) sorbents. Values for the relative changes in entropy and enthalpy associated with the interactive process were also determined. The results provide further insight into the factors involved with the stabilization of secondary structure and the mechanism of the interaction of peptides with hydrophobic surfaces.     

Thermodynamic analysis and thermodynamic efficiency of chemical reactors

In this paper, conditions of minimal dissipation for processes occurring in chemical reactors with a given duration and a given degree of transformation are obtained. It is demonstrated that the derived entropy production can be used to construct the space of realizable (thermodynamically feasible) regimes of a chemical reactor.     

Prediction of multicomponent liquid adsorption using excess quantities. II. Calculations for the liquid/solid interface

The utilization of excess quantities as the basis for a thermodynamic approach can simplify the prediction of multicomponent liquid adsorption from binary data. A new method for predicting liquid adsorption on solids is suggested, which is different from the existing equations with respect to the theoretical background and formulation. The applicability of the new model is tested with three ternary adsorption systems. The predicted surface excesses are discussed and compared with experimental ones and with those of other prediction models in the literature. The accordance between measured and predicted ternary data is convincing.     

Prediction of multicomponent liquid adsorption using excess quantities. III. Calculations for the liquid/air interface

The utilization of excess quantities as the basis of a thermodynamic approach can simplify the prediction of multicomponent data from binary ones. Whereas in Part II the excess formalism was applied to the prediction of liquid phase adsorption on solids, in this paper, the liquid/air interface is investigated. In order to show the generality of the suggested approach, thermodynamic equations are developed in analogy to Part II. Surface tensions are predicted by different excess models and compared with experimental data. From predicted surface tensions, ternary adsorption isotherms on the liquid/air interface are calculated.     

Organization of measurable thermodynamic quantities and their relevance to analytical chemistry

Summary A short discussion is given of the fundamentals of thermodynamics and of how the large number of measurable thermodynamic quantities can be organized in a clear and self-consistent way. The suggested Thermodynamic Family Tree also undelines the recent introduction of third order derivatives of Gibbs free energy as measurable properties with a sufficient accuracy. Those state functions are so new that they dont have a name nor a symbol yet! Finally some thoughts are given of how one should relate the thermodynamics to a recent discussion of H. Malissa [3] concerning the philosophy of analytical chemistry.

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Organisation meßbarer thermodynamischer Größen und ihre Bedeutung für die Analytische Chemie

Zusammenfassung Die Grundprinzipien der Thermodynamik werden kurz diskutiert und es wird gezeigt, wie die große Zahl meßbarer thermodynamischer Größen in ein klares und folgerichtiges System gebracht werden kann. Der vorgeschlagene thermodynamische Stammbaum zeigt die kürzlich eingeführten dritten Ableitungen der freien Gibbs-Energie als meßbare Eigenschaften mit befriedigender Genauigkeit. Diese Zustandsfunktionen sind so neu, daß sie noch keinen Namen und kein Symbol haben. Abschließend wird ausgeführt, wie die Thermodynamik zu einer kürzlichen Diskussion von Malissa über die Philosophie der analytischen Chemie in Beziehung gebracht werden kann.

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This paper was suggested by Professor Malissa of the Technische Hochschule Wien and should be considered a complement or extension to his important contribution to the discussion on the state and future of Analytical Chemistry (published in Fresenius Z. Anal Chem 305:97 (1981)     

Release kinetics of nicotinamide from fatty acid-nicotinamide equimolar complexes. II. Activation thermodynamic quantities.

The rates of release of nicotinamide (NAA) from fatty acid (FA)-NAA complexes, FA-NAA, were determined at various temperatures, and the thermodynamic quantities for the release of NAA were estimated. The results were compared with the previous results obtained for FA-thiamine disulfide (TDS) complexes, (FA)6(TDS). The values of activation enthalpy (delta H ++) and activation entropy (delta S ++) for the release of NAA from FA-NAA were positive and negative, respectively, indicating that the release of NAA is disadvantageous from not only enthalpic but also entropic viewpoints. The plots of delta H++ against the carbon number (n) in the constituent FA showed a zig-zag line with an upward convex at an odd-numbered position and the plots of the absolute values of (-delta S++) showed a zig-zag line with a downward convex at an odd-numbered position, though the positive value of delta H++ increases and the negative value of delta S++ decreases with an increasing n for either even-numbered or odd-numbered FA. It was found that the release of NAA from FA-NAA formed with odd-numbered FA is more disadvantageous enthalpically but more advantageous entropically as compared with that from FA-NAA formed with even-numbered FA. This phenomenon was similar to that observed for (FA)6(TDS). Furthermore, it is suggested that FA-NAA is formed at least by van der Waals forces and hydrophobic interactions and that van der Waals forces are dominant for the formation of FA-NAA formed with odd-numbered FA and that hydrophobic interactions are dominant for the formation of FA-NAA formed with even-numbered FA.     

Thermodynamic properties of liquid mixtures. II. Dimethylformamide-water

The excess enthalpy of mixing of DMF-water was measured at 25° C in the 0–1 molar fraction range. The maximum of heat is developed for a 0.33 DMF molar fraction. The excess partial molar and other excess quantities were also calculated for the DMF-water system at 25° C. The results suggest a strong interaction between DMF and water.     

Thermodynamic quantities of surface formation of aqueous electrolyte solutions VII. Aqueous solution of alkali metal nitrates LiNO3, NaNO3, and KNO3

To compare the effect of nitrate anions on the surface tension increments of aqueous solutions with that of halide anions, the surface tension of aqueous solutions of lithium nitrate, sodium nitrate, and potassium nitrate was measured as a function of temperature and concentration. It is shown that the surface tension of aqueous alkali metal nitrate solutions is determined primarily by the kinds of anions, since the surface tension increments of these nitrates were of the same magnitude. The importance of the electrical double layer at the surface is discussed in relation to these surface tension increments.     

Densities and derived thermodynamic properties of binary (alkanol + boldine) mixtures in the compressed liquid region

In this work, densities of two binary systems of {alkanol (ethanol and 1-propanol) + boldine} are measured at temperatures from (313 to 363) K and pressures up to 20 MPa using an Anton Paar vibrating tube densimeter. Each (alkanol + boldine) system was prepared at five diluted compositions with respect to the alkaloid. These are (x₂ = 0.0012, 0.0074, 0.0136, 0.0196, 0.0267) and (x₂ = 0.0018, 0.0046, 0.0077, 0.0112, 0.0142) mixed in ethanol and 1-propanol, respectively. Experimental densities are correlated using an empirical 6-parameter equation with deviations within 0.04%. Extrapolated densities at atmospheric pressure agree with the literature data. Isobaric expansivity, isothermal compressibility, thermal pressure coefficient, and internal pressure have been calculated.