Tellurium(IV) can be easily extracted into nitrobenzene from acid solution containing halide ion and 1, 10-phenanthroline (Phen). It seems to be due to the formation of the ternary complex between Te( IV)-halide complex and protonated 1, 10-phenanthroline. The ternary complexes are quantitatively extractable when the acid concentration is more than 0. 5 M for the iodocomplex and 2 M for the bromocomplex. The procedure for the extraction was as follows. The sample solution containing Te(IV) was introduced into a 100 ml separatory funnel to which potassium iodide or hydrogen bromide were added and the acid concentration was adjusted with sulfuric acid. After 1, 10-phenanthroline solution was added, the volume was made up to 20 ml with water. The mixture was shaken with 4 ml of nitrobenzene. The amount of Te(IV) in the organic phase was measured by AAS. The calibration curves obtained by the above procedure were linear up to 4× 10
-5 M for Te(IV) as the iodocomplex and 2 × 10
-5 M as the bromocomplex, respectively. The detection limit was 5 × 10
-7 M. The influence of coexisting metal ions on the determination of Te(IV) was investigated. By the addition of reducing agent such as sodium hypophosphite and the pre-extraction of metal ions at pH 3. 0 as ternary complex with phenanthroline in the form of [M (Phen)
m-X
n], the interferences by many metal ions could be excluded. The composition of the extracted species was investigated by the equilibrium method and elementary analysis. The results showed it to be Te(IV) : halide ion : Phen = 1 : 6 : 2. It could be assumed that Phen would take part in the formation of ion-pairing as the cation (PhenH
+).
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