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Abstract
Calorimetric measurements were made of the heat of immersion in water of cassiterite that was either untreated or treated with 60% HNO3. The heats of immersion of cassiterite and fluorite were also calculated theoretically from the surface Gibbs energy components, and compared with the heat of immersion measured for cassiterite and that taken from the literature for fluorite. The results of the measurements and calculation revealed that the heat of immersion depends on the degree of hydration of the surface of cassiterite and fluorite. It was also found that it is possible to predict the heats of immersion in water of cassiterite and fluorite from the Lifshitz-van der Waals and acid-base components of the surface Gibbs energy.
parameters of pair interaction of l -proline with urea in water, (iv) calculate the changes of reduced enthalpy of solution, entropy of solution and the reduced Gibbs energy at the temperature rise from 288 to 318 K, and (v) to discuss the obtained
Abstract
In this paper, examples are given of how calorimetric values can give greater certainty to phase equilibria calculated from thermodynamic data. Errors that may arise when phase diagram evaluations are carried out largely from the basis of Gibbs energy information only are illustrated by reference to recent evaluations of the Ti−Si system and the resulting calculated oxidation behaviour of titanium silicides. The importance of calorimetric values for calculation of metastable phase equilibria is demonstrated by results of work on the AlN−TiN hard-metal coating system. Finally, suggestions are made with regard to areas of work where calorimetric data are urgently needed.
Abstract
The enthalpies, entropies and Gibbs energies of inclusion of dl-1,3-, 1,4- and meso-2,3-butanediols into α- and β-cyclodextrin cavities from ideal gas phase have been determined on the basis of newly obtained experimental data of the butanediols. The butanediol molecules are stabilised strongly in the cavities due to interactions with inner walls of the cavities. Entropies of the gaseous isomers are greatly decreased in the cavities. The largest decrease is obtained for the case of 2,3-BD. Discussions concerning the1,4-butanediol given in the preceding paper have been changed due to the adoption of new data on the butanediols.
metabolism. Since simple formal predictions of the heat release and the Gibbs energy dissipation in heterotrophic growth exist, it ought to be possible to extend these for mixotrophic and autotrophic growth as well. It is the aim of this paper to develop a
Thermodynamic transition properties of highly ordered smectic phases
Series of main-chain liquid crystalline polyethers
A series of polyethers have been synthesized from 1-(4-hydroxy-4′-biphenyl)-2-(4-hydroxyphenyl)propane and α, Ω-dibromoalkanes having different numbers of methylene units [TPPs]. Both odd- and even-numbered TPPs [TPP(n=odd)s and TPP(n=even)s) exhibit multiple transitions during cooling and heating and they show little supercooling dependence, indicating close-to-equilibrium nature of these transitions. Combining the structural characterization obtainedvia wide angle X-ray diffraction powder and fiber patterns at different temperatures and the morphological observations from microscopy techniques, not only the nematic liquid crystalline phase but also highly ordered smecticF, smectic crystalG andH phases have been identified. The phase diagrams for both TPP(n=odd)s and TPP(n=even)s have been constructed [1–3]. Thermodynamic properties (enthalpy and entropy changes) during these transitions are studied based on differential scanning calorimetry experiments. The contributions of the mesogenic groups and methylene units to each ordering process can be separated and they indicate the characteristics of these processes thereby providing estimations of the transition types.
, while Vecher et al. [ 10 ] for the same purpose used a quantitative DTA, however, these two sets of results show significant discrepancies. Partial Gibbs energy of liquid gallium, using the EMF method, was measured by Aselage and Anderson [ 11 ] and
Excess enthalpies of mixtures of mono-carboxylic acid with dibutylether
Comparison with DISQUAC predictions
-carboxylic acid of general formula: CH 3 –(CH 2 ) p-2 –CO 2 H ( p = 2, 3, 4, 5, 6) + di- n -butylether (DBE), CH 3 –(CH 2 ) 3 –O–(CH 2 ) 3 –CH 3 . Data used in the model application deal with vapor liquid equilibrium and correlated excess Gibbs energies, G E
-Benz water model merits attention and calls for an explanation. In particular, it would be important to try to address the role played by the water–water H-bonds and their reorganization. In fact, Southall and Dill found that the Gibbs energy change for the
m o (298.15 K)) calculated from the equilibrium constant of experimentally studied reaction: using the computer program COMICS [ 5 ]. The value of Gibbs energy of formation as noted in the mentioned paper agrees with the results of an unpublished
