In the hydrobromic acid solution,tellurium(Ⅳ) forms a yellow bromide complex which can be extracted by tributyl phosphate(TBP).The addition of ascorbic acid to the aqueous solution serves to remove some interferences.Experiments show that the maximum absorption of the yellow complex is at 450 m,u.Its solution is stable and obeys Beer's law.TBP may be diluted by toluene.Extinction reaches maximum,when extraction is made with 20% TBP in toluene.The extractability of tellurium complex by TBP depends on the concentration of the bromide ions in the aqueous solution.In the absence of sodium bromide,extinction will not reach maximum,when the hydrobromic acid concentration is below 4.2 N.