The action of fluorine on tellurium gives at -150' exclusively the hexafluoride, a t -60' hexafluoride and some ditellurium decafluoride, and at W O O mainly tetrafluoride. The proportion of decafluoride is increased by various solid additives; of these tellurium dioxide was the most effective. Apart from the useful control of temperature brought about by diluting the fluorine with another gas, a gaseous diluent also raises the yield, nitrogen considerably and oxygen much more. With the use of the former the oxyfluoride Te,F,,O, also appears among the products, and with the latter both this oxyfluoride and a more complex one are formed.The ditellurium decafluoride has been rigorously purified and many of its properties have been studied. Our data are in substantial agreement with those of English and Dale.6The properties of Te,F,,O, and the material of higher molecular weight, possibly Te6F,,0,, are described.AT the outset of this investigation (1951) the hexafluoride was the only fluoride of sexavalent tellurium known with certainty.separated about 1 C.C. of liquid, m. p. -13*6", b. p. 61.2", from products of the reaction between tellurium and fluorine, and suggested that it might be ditellurium decafluoride. The evidence was inconclusive and, while working with one of us, Peacock was unable to obtain this liquid in the way prescribed, but from the action of fluorine on tellurium dioxide isolated small quantities of liquid with a range of melting points from -46" to -45" and molecular weights from 351 to 475. The quantities were too small for effective fractionation, but the liquids differed from Yost and Claussen's material in being resistant to water at 100" whereas theirs was decomposed at 85" by heat alone.Starting from this point the present fluorination of tellurium and its oxides soon showed that, under certain conditions, products containing appreciable quantities of unequivocal decafluoride could be obtained. When notice of a Note on ditellurium decafluoride by English and Dale appeared4 our work had proceeded so far, and had also disclosed other new compounds, that it was continued.The broad features of our many preparative experiments are shown in Table 1. Tellurium trioxide yielded only hexafluoride, and the dioxide, which reacts with fluorine at a In -1933 Yost and Claussen
