Hexafluoride modifications

Powder X-ray diffraction data of technetium hexafluoride and rhenium hexafluoride modifications are compiled in Table 10.5. A. 

FIGURE 8.41 Xenon Hexafluoride modification most stable at room temperature. 

Uranium can be analysed as the hexafluoride, but the procedure requires modification of the chromatographic apparatus, nickel coating of metallic parts and nickel filaments in the katharometer [606], Tin in zirconium—tin alloys can be analysed as the chloride, prepared by treatment with chlorine [607]. Selenium and tellurium are converted into fluorides by treatment of their oxides with xenon difluoride [608]. 

The similarity of OsOFg and ReOFg to the related hexafluorides is also shown by the thermod5mamic and structural data contained in Tables 5 and 6. The orthorhombic (low temperature) modification of OsOFg... 

Technetium hexafluoride can be prepared by reaction of technetium metal powder with excess fluorine gas in a closed nickel can at 400 °C. The volatile golden-yellow solid was purified by fractional sublimation at reduced pressure. The yield of purified TcF, was greater than 90% [63[. Lower conversions are obtained by treating finely divided technetium metal at 350 °C with a F2/N2 mixture in a flow stream. TcFf, melts at 37.4 °C, boils at 55.3 °C, and undergoes a solid-solid transition at -4.54 °C from the low temperature orthorhombic to the bcc modification at room temperature [64]. More recently the transition temperature of 268.335 K was reported [67]. 

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