Selected thermodynamic data references

In the same chapter (Chapter 5), as an introduction to the paragraphs dedicated to the various groups of metals, the values relevant to a number of elementary properties have been collected. These are atomic properties (such as metallic and ionic radii, ionization energies, electronegativities, Mendeleev number, chemical scale, Miedema parameters, etc.), crystal structure and lattice parameters data of the allotropes of the elements, and selected thermodynamic data (melting and boiling temperatures and enthalpies, etc.). All these data indeed represent reference values in the discussion of the alloying behaviour of the elements. 

Selected standard thermodynamic data referring to chemical reactions are also compiled in the data base. A chemical reaction r , involving reactants and products B , can be abbreviated as ... 

Table 111-1 Selected thermodynamic data for selenium compounds and complexes. All ionic species listed in this table are aqueous species. Unless noted otherwise, all data refer to the reference temperature of 298.15 K and to the standard state, i.e., a pressure of 0.1 MPa and, for aqueous species, infinite dilution (/ = 0). The uncertainties listed below each value represent total uncertainties and correspond in principle to the statistically defined 95% confidence interval. Values obtained from internal calculation, cf. footnotes (a) and (b), are rounded at the third digit after the decimal point and may therefore not be exactly identical to those given in Part V. Systematically, all the values are presented with three digits after the decimal point, regardless of the significance of these digits. The data presented in this table are available on computer media from the OECD Nuclear Energy Agency.

Some of tfie physical piopeities of tungsten ate given in Table 3 fuithei property data ate available (12—14). For thermodynamic values. References 5,15, and 16 should be consulted. Two values are given for the melting point. The value of 3660 K was selected as a secondary reference for the 1968 international practical temperature scale. However, since 1961, the four values that have been reported ranged from 3680 to 3695 and averaged 3688 K. 

Table 2.1 Thermodynamic properties of AIN at selected temperatures (data are taken from NIST-JANAF tables [17]). Enthalpy reference temperature = T = 298.15 K p° = 1 bar.

Figure 4.24 Relationship between the partial pressure of oxygen and the composition of CO-CO2 and H2-H2O gas mixtures at 1 bar. (a) Pco PcO-, versus temperature and (b) Pyi2IPw-X) versus temperature at selected partial pressures of oxygen. Thermodynamic data are taken from reference [21].

References (20, 22, 23, 24, 29, and 74) comprise the series of Technical Notes 270 from the Chemical Thermodynamics Data Center at the National Bureau of Standards. These give selected values of enthalpies and Gibbs energies of formation and of entropies and heat capacities of pure compounds and of aqueous species in their standard states at 25 °C. They include all inorganic compounds of one and two carbon atoms per molecule. 

The section entitled Thermodynamic Data contains references which include thermodynamic properties and also chemical reaction equilibria data, physical property data, and specific formulae required in calculations. It is difficult to select the best source as each provided different information. 

The thermodynamic data compiled in the present review (see Chapters III and IV and Appendix E) refer to the reference temperature of 298.15 K and to standard conditions, cf. Section II.3. For the modelling of real systems it is, in general, necessary to recalculate the standard thermodynamic data to non-standard state conditions. For aqueous species a procedure for the calculation of the activity factors is thus required. This review uses the approximate specific ion interaction method (SIT) for the extrapolation of experimental data to the standard state in the data evaluation process, and in some cases this requires the re-evaluation of original experimental values (solubilities, emf data, etc.). For maximum consistency, this method, as described in Appendix B, should always be used in conjunction with the selected data presented in this review. However, some solubility data for highly soluble selenates were evaluated in the original papers by the Pitzer approach. No attempt was made to re-evaluate these data by the SIT method. 

The thermodynamic data in the selected set refer to a temperature of 298.15 K (25.00°C), but they can be recalculated to other temperatures if the corresponding data (enthalpies, entropies, heat capacities) are available [97PU1/RAR]. For example, the temperature dependence of the standard reaction Gibbs energy as a function of the standard reaction entropy at the reference temperature (7o= 298.15 K), and of the heat capacity function is ... 

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