Chemical thermodynamics of the

Current interest in high temperature chemistry and the closely related thermodynamics of the actinides will provide additional stimuli for determining precise thermodynamic data in cryogenic as well as in higher temperature regions. The utopian era in the chemical thermodynamics of the lanthanides is sufficiently far off to occasion extension of shrewdly devised schemes to other classes of compounds. Use of the semi-empirical schemes already discussed—or theoretically based ones— plus the key compound concept may prove as effective here (desipte magnetic and electronic complications) as it has for hydrocarbon thermodynamics. 

WES/GRO] Westrum, Jr., E. F., Gronvold, F., Chemical thermodynamics of the actinide element chalcogenides. Thermodynamics of nuclear materials, Proc. Int. Symp., held in Vienna, Austria,21-25 May 1962, pp.3-37. International Atomic Energy Agency, Vienna,... 

The concentration of the dissolved boron species as a function of pR is shown in Figure 3a. There is little discussion regarding the chemical thermodynamics of the boron equiUbrium (cf. Zeebe Wolf-Gladrow 2001). A value frequently used for the dissociation constant of boric acid, ptsTs. is 8.60 at r= 25°C, 5 = 35 (DOE 1994). It is also noted that at typical total boron concentration of c. 420... 

Oe2 F. L. Getting, M. H. Rand. J.R. Ackermann The Chemical Thermodynamics of the Actinide Elements and Compounds, Part 1, The Actinide Elements, IAEA, Vienna, 1976. 

Wei E.F. Westrum, Jr., F. Gronwald Chemical Thermodynamics of the Actinide Element Chalcogenides, Proc. Symp. ofThermodyn. of Nucl. Mat., IAEA, STI-Pub. 58, pp. 3-37, Vienna, 1962. 

Besmann, T. M., Lindemer, T. B. Chemical thermodynamics of the system Cs-U-Zr-H-I-O in the light water reactor fuel-cladding gap. Nucl. Technology 40, 297-305 (1978)... 

Westrum, E.F.Jr., Developments in Chemical Thermodynamics of the Lanthanides, in Advances in Chemistry Series, Number 71, American Chemical Society 1967, pp. 25-50. 

It is generally assumed that isosteric thermodynamic heats obtained for a heterogeneous surface retain their simple relationship to calorimetric heats (Eq. XVII-124), although it may be necessary in a thermodynamic proof of this to assume that the chemical potential of the adsorbate does not show discontinu-... 

Stull, D. R. Westrum, E. F. Sinke, G. C., 1969. The Chemical Thermodynamics of Organic Compounds. Wiley, New York. 

The sequence of amino acids in a peptide can be written using the three-letter code shown in Figure 45.3 or a one-letter code, both in common use. For example, the tripeptide, ala.ala.phe, could be abbreviated further to AAF Although peptides and proteins have chain-like structures, they seldom produce a simple linear system rather, the chains fold and wrap around each other to give complex shapes. The chemical nature of the various amino acid side groups dictates the way in which the chains fold to arrive at a thermodynamically most-favored state. 

A quantity of great importance in chemical thermodynamics is the Gibbs free energy G. The latter is defined in terms of enthalpy H as... 

The initiators which are used in addition polymerizations are sometimes called catalysts, although strictly speaking this is a misnomer. A true catalyst is recoverable at the end of the reaction, chemically unchanged. Tliis is not true of the initiator molecules in addition polymerizations. Monomer and polymer are the initial and final states of the polymerization process, and these govern the thermodynamics of the reaction the nature and concentration of the intermediates in the process, on the other hand, determine the rate. This makes initiator and catalyst synonyms for the same material The former term stresses the effect of the reagent on the intermediate, and the latter its effect on the rate. The term catalyst is particularly common in the language of ionic polymerizations, but this terminology should not obscure the importance of the initiation step in the overall polymerization mechanism. 

If the gas has the correct composition, the carbon content at the surface increases to the saturation value, ie, the solubiUty limit of carbon in austenite (Fig. 2), which is a function of temperature. Continued addition of carbon to the surface increases the carbon content curve. The surface content is maintained at this saturation value (9) (Fig. 5). The gas carburizing process is controlled by three factors (/) the thermodynamics of the gas reactions which determine the equiUbrium carbon content at the surface (2) the kinetics of the chemical reactions which deposit the carbon and (J) the diffusion of carbon into the austenite. 

Selective Toluene Disproportionation. Toluene disproportionates over ZSM-5 to benzene and a mixture of xylenes. Unlike this reaction over amorphous sihca—alumina catalyst, ZSM-5 produces a xylene mixture with increased -isomer content compared with the thermodynamic equihbtium. Chemical modification of the zeohte causing the pore diameter to be reduced produces catalysts that achieve almost 100% selectivity to -xylene. This favorable result is explained by the greatly reduced diffusivity of 0- and / -xylene compared with that of the less bulky -isomer. For the same reason, large crystals (3 llm) of ZSM-5 produce a higher ratio of -xyleneitotal xylenes than smaller crystahites (28,57). 

The chemical reaction of the lead-acid battery was explained as early as 1882 (11). The double sulfate theory has been confirmed by a number of methods (12—14) as the only reaction consistent with the thermodynamics of the system. The thermodynamics of the lead —acid battery has been reviewed in great detail (15). 

G. Egloff, G. HuUa, and V. I. Komarewski, Isomerisation of Pure Hydrocarbons, Reinhold Publishing Corp., New York, 1942 D. R. Stuhl, E. E. Westrum, and G. C. Sinke, The Chemical Thermodynamics of Organic Compounds, ]ohn Wiley Sons, Inc., New York, 1969. 

Internal and External Phases. When dyeing hydrated fibers, for example, hydrophUic fibers in aqueous dyebaths, two distinct solvent phases exist, the external and the internal. The external solvent phase consists of the mobile molecules that are in the external dyebath so far away from the fiber that they are not influenced by it. The internal phase comprises the water that is within the fiber infrastmcture in a bound or static state and is an integral part of the internal stmcture in terms of defining the physical chemistry and thermodynamics of the system. Thus dye molecules have different chemical potentials when in the internal solvent phase than when in the external phase. Further, the effects of hydrogen ions (H" ) or hydroxyl ions (OH ) have a different impact. In the external phase acids or bases are completely dissociated and give an external or dyebath pH. In the internal phase these ions can interact with the fiber polymer chain and cause ionization of functional groups. This results in the pH of the internal phase being different from the external phase and the theoretical concept of internal pH (6). 

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