The A l-N i phase diagram has been investigated in the com position range x Ni = 0.70 to 0.97. Phase boundaries were determined by using differential thermal analysis and Knudsen effusion mass spectrometry. The measurements were carried out in the temperature range between 1409 and 1730K. An A l-N i phase diagram is obtained for x Ni Si 0.70 by com bining the data from this work with selected data from the literature. This diagram deviates from that recommended by phase diagram compilations and used generally in the literature to date; it agrees reasonably well with a diagram which has been rejected in the literature. + On leave from: Fuel Chemistry D ivision,

The vaporization of NaI/FeI2 and NaI/PbI2 samples of equimolar composition was investigated in the temperature ranges between 574 to 683 K and 562 to 669 K, respectively, by using the mass spectrometric Knudsen effusion method. The gaseous species I. I2, Nal. (NaI)2 FeI2, (FeI2)2, FeI3, NaFel3, and Na2FeI4 (NaI—FeI2 system) as well as Nal, (Nal)2, PbI2, (PbI2)2, and NaPbI3 (NaI—PbI2 system) are present in the equilibrium vapours. The equilibrium partial pressures of these species were determined with the exception of I, I2, and Fel3. Enthalpies and entropies of dissociation resulted for the reactions as ΔdH2980 (Eq. (1)) = 184 ± 5 kJ mol−1, ΔdH2980 (Eq. (1)) = 043 ± 8 j mol−1K−1;ΔdH2980 (Eq. (2)) = 333 ± 9 kj mol−1, ΔdH2980 (Eq. (2)) = 274 ± 14 J mol−1 K−1; and ΔdH2980 (Eq. (3)) = 168 ± 5 J mol−1, ΔdH2980 (Eq. (3)) = 151 ± 9 j mol−1 K−1. Equilibrium constants for these reactions are additionally given. The pressures of NaFel3(g) and NaPb13(g) as well as their enthalpies of dissociation are discussed with respect to their significance for semi empirical rules.

The vaporization of liquid and solid alloys of the Al — Ni system in the range xNi = 0.7 to 1 has been extensively investigated by the use of Knudsen effusion mass spectrometry in the temperature range between 1389 and 1734 K. 15 alloy samples of different compositions of the complete concentration range were studied in the course of 25 runs and their Al and Ni partial pressures determined. The vapour pressure measurements in the course of the individual runs were carried out over temperature ranges of up to about 300 K covering the solid and the liquid state for many of the alloys investigated. Chemical activities and chemical potentials for Al and Ni as well as Gibbs energies were evaluated at 1600 K for the solid and at 1728 K for the liquid state. Two independent methods were used for the determination of Ni activities of the solid alloys yielding consistent results. The large temperature range of the partial pressure measurement for the solid AlNi3 phase with xNi = 0.750 rendered possible the determination of a complete set of partial and integral thermodynamic functions (ΔG, ΔH, ΔS) for the formation of this phase. The values obtained are discussed. The partial and integral enthalpies of formation are compared with the enthalpies of dissociation of the gaseous species Ni2(g), Al2(g), and AlNi(g). The integral enthalpy of formation, obtained for the first time by vapour pressure measurements, agrees well with the results of a recent calorimetric study.

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The sorption of Sr by graphitic materials used in high‐temperature gas‐cooled reactors was studied by applying high‐temperature mass spectro‐metry with a Knudsen cell and the isopiestic method. Sorption isotherms were determined for matrix graphite with Sr concentrations between 3.88 · 10−5 and 8.85 · 10−2 mol kg−1. The sorption enthalpies and partial pressures determined for concentrations greater than 1.5 · 10−4 mol kg−1 showed many properties of Freundlich isotherms. The evaluated vaporization enthalpies of Sr(e.g. ΔvH01660 = 447. 8 ± 7.7 kj mol−1 for a Sr concentration of 3.42 · 10−4 mol kg−1) indicate a strong chemisorption of Sr by graphite. An exceptionally high sorption capacity for Sr has been observed for nongraphitized coked resin binder.