Sources of thermodynamic data

The changes in free energy of formation of Reaction (1) are shown in Fig. 2.1 as a function of temperature. " The values of AG were calculated using Eq. (1) above for each temperature. The Gibbs free-energy values of the reactants and products were obtained from the JANAF Tables.1 Other sources of thermodynamic data are listed inRef 6. These sources are generally accurate and satisfactory forthe thermodynamic calculations of most CVD reactions they are often revised and expanded. 

Many sources of thermodynamic data are now availableinclud-ing the following ... 

Sources of thermodynamic data which the authors have found to be valuable in hydrometallurgical applications have been assembled in Table II. 

STABCAL was also used to construct pE-pH stability fields for chloropyromorphite, hinsdalite, plumbogummite, tricadmium diphosphate, tricopper diphosphate, and hopeite (Fig. 7). These diagrams allow for estimation of stability with respect to pH and to the presence of insoluble sulphides. The NBS thermodynamic database (Wagman et al. 1982) was used as a source of thermodynamic data. The total concentrations chosen for each metal were selected to produce a stability region for the metal phosphate solid. In some cases, this was a very low total concentration (e.g., CTPb =1 x 10 10 M for Pb). In other cases, the total metals concentration was high (e.g., C r.cd— 1 x 10 3 M for Cd). The modelling exercise used typical equilibrium concentrations for MSW bottom ash leachates as shown in Table 2. 

The sources of thermodynamic data and reaction-specific data are increasing rapidly, and this overview is by no means comprehensive. Still, important information on thermochemistry for important species or rate constants for key reactions may be unavailable. In such situations data estimation procedures may be employed. A number of simple as well as more advanced methods can be used for this purpose. For an overview the reader may consult the review by Senkan [356]. 

We now look at some examples of redox reactions involving simple cations in aqueous solution. Electrochemical terminology will often be encountered, since e.m.f. measurements on electrochemical cells are important sources of thermodynamic data in this area. For example, the reduction potential ° for the half-reaction ... 

In some cases, a literature source of thermodynamic data may exist, allowing one to perform the conversion. Fortunately, standard references (such as Refs. 168 and 180) frequently tabulate both the condensed and gas phase thermochemistry values. When that is not the case, the following relations may be used, where the enthalpies and entropies of vaporization and fusion must be at 25 °C ... 

Standard sources of thermodynamic data list the heat or enthalpy of formation at a... 

One may not necessarily be able to find the Kp for every reaction of concern therefore the determination from sources of thermodynamic data can become important. 

Section 2.5 examines addition reactions which are the reverse of the radical decomposition reactions considered in Section 2.4. These reactions in themselves are comparatively unimportant in hydrocarbon oxidation, but they have provided a good source of thermodynamic data on radicals. Thermodynamic parameters are central to the modelling of autoignition because of the importance of heat release, but also because of their use in determining the rate parameters for the reverse of well characterized reactions. Section 2.5 includes a brief review of the currently accepted alkyl radical heats of formation. This field has been in turmoil in recent years because of disagreements on the values, which largely derive from kinetic measurements. Consensus is emerging but controversy still remains. 

Reference [9] abbreviated as K was used as the primary source of thermodynamic data. This is because K contains more relevant information than any other up to date compilation. For most compounds thermodynamic data from different compilations are identical or almost identical, but there are a few clear discrepancies. Assessment of credibility of data from different compilations is beyond the scope of the present book. 

EQ3/6 (Wolery, 1992). EQ3 is a speciation program, which can be used alone or to prepare input for eq6, a reaction path program. A kinetics option is also available. The program has a comprehensive database, primarily through the effort of Dr James Johnson. Unlike many other databases, the sources of thermodynamic data are documented in this database. 

One of the more comprehensive and reliable sources of thermodynamic data is the JANAF thermochemical tables. 

The objective of the present review is the critical compilation of a database for the inorganic species of nickel. This aim is achieved by an assessment of all sources of thermodynamic data published until mid-2002. This assessment is performed in order to decide on the most reliable values that can be recommended. Experimental measurements published in the scientific literature are the main source for the selection of recommended data. Previous reviews are not neglected, but form a valuable source of critical information on the quality of primary publications. 

Thermod3mamic data must be sought from many sources. The American Petroleum Institute and Manufacturing Chemists Association have large projects to determine and collect thermodynamic data. Several governmental agencies, such as the National Bureau of Standards and the Bureau of Mines, determine, collect, and publish thermodynamic data. Some of the best and most readily available sources of thermodynamic data are listed below. 

K. Ciazynska-Halarewicz, M. Helbin, P. Korzenecki and T. Kowaiska, Mathematical models of solute retention in gas chromatography as sources of thermodynamic data. Part IV. Aliphatic alcohols as the test analytes,/ Chromatogr. Set, 2007, 45, 492-499. 

Another problem is deciding how to model the system. In checking the two most complete sources of thermodynamic data, the National Bureau of Standards (1) and Russian Academy of Sciences (2) compilations, two different pictures of the solution behavior emerge. The NBS gives the following data for a gypsum solution ... 

For many years, the thermodynamic description of macromolecules lagged behind other materials because of the unique tendency of pol5nneric systems to assume nonequilibrium states. Most standard sources of thermodynamic data are, thus, almost devoid of polymer information (1-7). Much of the aversion to include polymer data in standard reference sources can be traced to their nonequilibrium nature. In the meantime, polymer scientists have learned to recognize equilibrium states and utilize nonequilibrium states to explore the history of samples. For a nonequilibrium sample it is possible, for example, to thermally establish how it was transferred into the solid state (determination of the thermal and mechanical history). More recently, it was discovered with the use of temperature-modulated differential scanning calorimetry (TMDSC) that within the global, nonequilibrium structure of semicrystalline polymers, locally reversible melting and crystallization processes are possible on a nanophase level (8). 

Light Scattering. Light scattering methods are a long established and reliable source of thermodynamic data on both dilute and concentrated polymer solutions. Scholte showed in detail how to obtain concentration and temperature dependences of chemical potential from the intensity (/) of scattered light, and also how the extrapolation (/ -> 0) furnishes spinodal temperatures even in... 

Calorimetric, spectroscopic and electrochemical measurements are the classical sources of thermodynamic data. In the present section it will be demonstrated that thermodynamic data of com parable quality can be extracted from the results of phase equilibria experiments at elevated pressures and temperatures. The prerequisite for data extraction are that... 

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