Sodium halides thermodynamic data

Figure 7.4 Thermodynamic data needed in evaluation of the enthalpy of formation of MX(s). (a) Lattice enthalpy of sodium halides (b) lattice enthalpy of alkali iodides (c) electron gain and dissociation enthalpies of halides (d) ionization and atomization enthalpies of alkali metals.

The complexation in the Nal-Sclg system (cf. Table 20) has been investigated by us for the first time by the use of two-compartment Knudsen cells. By this means a substantially improved assignment of the various ions in the mass spectrum to their neutral precursors is rendered possible, which is a pre-requisite for the determination of reliable thermodynamic data. Two-compartment Knudsen cells were also used for the study of the systems NaX-SnXj (X = Q, Br, I) (Table 20) as well as the systems NaBr-SnIj and SnBr2-Snl2 (Table 21) due to the different volatilities of the sodium and tin halides and in order to elucidate fragmentation patterns especially for systems with mixed anions. 

REDUCTION OF OTHER METAL HALIDES. The reduction of several other metal halides with sodium dispersions proved very successful, although higher temperatures were required for the reduction of some of the metals. In most instances, reduction did not occur imtil a specific threshold, or trigger, temperature was reached no attempt was made to determine whether this phenomenon was due to a potential barrier which required a high activation energy to overcome, or to some other thermodynamic and/or kinetic properties of the system. Attempts to correlate free energy data with threshold temperatures were unsuccessful. 

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