Tellurium Oxyfluorides

The distant resemblance of tellurium to the metalloid antimony, its neighbour in Group V_B, extends to the formation of oxyhalides or basic halides. The system TeO₂—HF—H₂O has been investigated at 10° C. and a number of crystalline hydrated oxyfluorides obtained either by slow evaporation of solutions of tellurium dioxide or tellurous acid in nearly 100 per cent, hydrofluoric acid, or by evaporation in a vacuum over concentrated sulphuric acid of solutions in 40 to 55 per cent, hydrofluoric acid. The monohydrate, TeF₄.TeO₂.H₂O, was generally obtained in the form of rosettes of transparent needles; the dihydrate, TeF₄.TeO₂.2H₂O, sometimes separated in this form and sometimes as hard milk-white nodules of radiating crystals. An oxyfluoride of composition 2TeF₄.3TeO₂ was also isolated both in the anhydrous condition and as a hydrate containing 6H₂O.

The exact nature of the oxyfluorides described has not yet been determined, but for the monohydrate there is evidence in favour of the formula 2TeOF₂.H₂O.