High-temperature mass-spectrometric investigations of the equilibrium vapours over crystalline tellurium dioxide have shown the existence of the molecular species (Te02)n and (TeO)n, where n = 1,2, 3 , 4 as well as Te2 and 0,. Under these conditions the most abundant species are Te02(g) and TeO(g). Second-and third-law heats of reaction and entropies for the various equilibria among these species have been obtained. Fundamental frequencies obtained from infra-red absorption studies of the species isolated in rare-gas matrices were used for calculations of thermodynamic functions at various temperatures. Heats of atomization for (TeO& and (TeO)z were obtained. Using the average of the second and third-law heats, = 2.5f2 kcal mol-l, for the reaction TeO(g) = *Te2(g)++02(g) one obtains the dissociation energy for TeO(g), Di = 92.5 rfr2 kcal mol-'. A bent geometry (110") is indicated for TeO, and evidence for cyclic structures of (Te02)2 and (TeO), is given.
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.
Gallium has become increasingly popular as a substrate material for electronic devices. Aside from ore, gallium can be obtained from such industrial sources as the Bayer process caustic liquor that is a byproduct of bauxite processing, flue dust removed from the fume-collection system in plants that produce aluminum by the electrolytic process, zinc refinery residues, gallium scrap materials, and coal fly ash. The purification process for gallium can start with solvent-extraction processes where the concentrations of impurities, especially metals, are reduced to the ppm range. This article describes how ultra-purification techniques can be employed to reduce the undesirable impurities to the low ppb range. The various procedures described give an idea as to the extent of work needed to obtain and prepare high-purity gallium for electronic application.
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