Investigation of the extraction equilibrium of ternary ionassociation complex of thallium(III) with iodo-nitro-tetrazolium chlorid

The extraction equilibrium of the ternary ion-association complex of iodo-nitro-tetrazolium [3-(4-iodophenyl)2-(4-nitrophenyl)-5-phenyltetrazolium chloride] with the chlorocomplex of thallium(III) is investigated radiochemically. The molar ratio of the ion-associate is found to be 1:1, the association constant has a value of 3.2x103 in aqueous solution and the distribution constant is 8.9. The extraction constant which gives a quantitative characterization of the equilibrium is 2.3x104. From the investigation performed it can be concluded that a quite satisfactory extraction of thallium(III) by means of iodo-nitro-tetrazole in benzene can be carried out. The extraction constant has a relatively high value which allows to use this system conveniently for the extraction-photometric determination of thallium(III). (T.C.)