Thermodynamics of Gaseous Species in the Sodium‐Scandium‐Iodine System

Abstract

The vaporization behavior of NaI(s), ScI3(s), and mixtures of these two phases containing 50, 92, 95, and 98 mole percent (m/o) NaI has been studied by effusion-beam mass spectrometry and by torsion-mass-effusion techniques in the approximate region 700-900 K. Vapor molecular weights show that NaI and SCI3 monomers make up 84 and 94 m/o, respectively, of the saturated vapors over the pure phases with the balance primarily dimer. NaScI4 is the maj or gaseous species over the mixtures, with a small amount of Na2ScI5 also present. Total vapor pressures of the pure phases and the mixtures were determined by the torsion method, and the enthalpies of sublimation of the monomer and dimer species over NaI and ScI3 were determined. The total vapor pressures of molten NaI and the NaI-ScI3 mixtures were also measured in the 10 2-10 -1 atm range by the TGA boiling point method, and vapor mass spectra were used to estimate the activities of'NaI and ScI3 in the liquid mixtures. Additionally, gaseous equilibria involving NaScI4 as well as the lower valent species ScI and ScI2 were studied by mass spectrometry. Vapor thermodynamic properties were derived and are compared with results in the literature.

Thermochemical Properties of the Gaseous Bromo-iodides of Dy and of the Na−Dy Tetrahalo Complexes

“…Chemical modeling of local equilibrium conditions is a useful tool in predicting lamp behavior, and for this reason studies of the vaporization thermodynamics of the NaBr−DyBr 3 1 and NaI−DyI 3 2,3 systems have been reported. Similar studies of the NaI−ScI 3 system have also been reported. , In addition, Hilpert 6 has reviewed much of the information on complexation of metal halide vapors.…”

“…Separate mass spectra on NaBr vapor show that the intensities of Na + and NaBr + are very similar, so that Na + is a major fragment ion from NaDyBr 4 , as seen also in NaScI 4 vapor. 4,5 Intensities of the principal ions NaBr + , DyBr 3 + , and NaDy-Br 3 + were then measured at AE + 3 eV at a series of temperatures. From the mass spectra of NaBr, DyBr 3 , and that of NaBr-DyBr 3 reported here, the fragmentation patterns of each of the gaseous neutrals NaBr, DyBr 3 , and NaDyBr 4 in the mixture were sorted out so that the total ion yields of each at AE + 3 eV could be evaluated from the intensities of the principal ions noted above.…”

“…Table 9 gives a summary of the gaseous reaction equilibria studied in this work, together with derived third law enthalpy changes and standard enthalpies of formation, ∆ f H°2 98 , of the Na-Dy-Br-I species evaluated from these results. The six independent thermochemical relations (3)(4)(5)(6)(7)(8) were solved to obtain the six unknown ∆ f H°2 98 values for the species NaDyBr 3 I, NaDyBr 2 I 2 , NaDyBrI 3 , DyBrI, DyBr 2 I, and DyBrI 2 , after evaluation of ∆ f H°2 98 for NaDyBr 4 and NaDyI 4 from the thermochemistry of reactions 1 and 2. Auxiliary thermodynamic 9 shows that the enthalpy changes for the ligand exchange reactions 3-8 are all relatively small, only a few kcal mol -1 , compared to the Na-X and Dy-X, where X ) Br or I, bond strengths ranging from 65 to 100 kcal mol -1 .…”

“…Similar studies of the NaI-ScI 3 system have also been reported. 4,5 In addition, Hilpert 6 has reviewed much of the information on complexation of metal halide vapors.…”

The fate of alkali species in advanced coal conversion systems. Final report

“…The instrumentation constant was calculated from the observed NaC1 vaporization data. The ionization cross section of molecules was calculated from the sum of atomic ionization cross sections (Hildenbrand et al, 1990). The atomic ionization cross-section data were taken from the compilation by Mann (1967).…”