A vacuum microbalance and a mass spectrometer have bem used to determine sublimation pressures and heats of sublimation for CaFz(s) over the range 1242-1669°K. The data are represented by log Pat,,, = -(95.46 i . 0.49)/45.76 X 104/T + 8.141 f 0.006. The errors quoted are standard deviations of the least-squares fit.The heat of sublimation a t 298°K. is 103.3 f 2.0 kcal./mole. From studies of the reaction of CaF2 with aluminum over the range 1271-135loK., DOZSS for CaF(g) was determined to be 5.4 =t 0.2 e.v. from two independent equilibria. Close agreement with other investigators is found for the sublimation of CaF2(s) but the dissociation energy oi CaF(g) is much greater than the previously accepted value.The matrix isolation method, which was adapted for infrared spectroscopy of molecular species existing at Rather Most of the features of these spectra must arise from polymeric alkali halide species.Isotope ef-high temperatures by Linevsky, has been employed to examine the spectra of LiF, LiCl, and NaF. complex spectra were found. Spectra were taken for Ar, Kr, and Xe matrices and the effects of matrix material are considered. fects as well as spectral shifts after matrix diffusion assist in the interpretation of these data.

Lithium oxide sublimes mainly by decomposition to the elements at 1400°K., but an appreciable partial pressure of LizO(g) in equilibrium with the solid is indicated by mass spectrometric studies of LiaO sublimation from a platinum Knudsen cell. From absolute pressures and estimated thermodynamic functions, the following heats were obtained: LizO(s) = LiaO(g), AH0°= 104 ± 5 kcal./mole; LiO(g) = Li(g) + 0(g), )0°Z 83 kcal./mole (3.6 e.v.). LiO(g) is of very minor importance as a vapor species, but LiONa(g), formed when Na is present as an impurity, appears to have considerable stability.

High-temperature Knudsen-cell mass spectrometry has been used to measure the gaseous equilibria over an aluminum-gold or aluminum-silver-gold alloy in a tantalum cell. The enthalpies for the reactions (1) AlAu(g) = Al(g) + Au(g), and (2) AlAu(g) + Au(g) = Au2(g) + Al(g) were measured. The following dissociation energy D°0, heat of sublimation Δ H°s,298, and heat of formation Δ H°f,298 were derived from these reaction enthalpies for gaseous AlAu: 77.0 ± 1.5, 98.4 ± 2.5, and 88.9 ± 2.0 kcal mole−1, respectively. The dissociation energy of AlAu(g) has been interpreted in terms of the Pauling model of a polar bond. This model has been used to calculate dissociation energies of selected intermetallic compounds between transition metals, Group III metals, and Group IV metals with gold, which are compared with available literature data.

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By heating the difluorides of magnesium, strontium, and barium under reducing conditions, one obtains significant amounts of the respective monofluorides. Mass spectrometric studies of equilibria involving these monofluorides have yielded the dissociation energies (D°298) 4.62±0.1 eV, 5.43±0.1 eV, and 5.83±0.1 eV for gaseous MgF, SrF, and BaF, respectively. These results support an ionic model for these molecules and are considerably higher than those previously accepted.