A new radiometric titration method based on separation by means of ion exchange

Abstract

A mathematical expression is derived for the radiocomplexometric determinatic,n of a mixture of two metals with one ligand, using an anion exchanger in the solutic,n as a phase separating system. An expression is also given for the complexometric titration of a metal, when formation of acidic or basic complexes is taken into account. In the experimental part titration procedures are proposed for determinations of nickel, copper and iron, using 65Zn as indicator. The formation of the acidic complex. ZnHY, does affect the radiometric titration curve of zinc with EDTA. ln~oducfion In a previous paper a a radiometric titration of zinc with EDTA in the absence of other metals, based on phase separation by means of ion exchange in the solution, has been described. A formula was derived for this type of titration, showing that under certain conditions the titration curve consists of two straiglht lines. In the present paper a formula is derived for the titration curve of the determination of zinc with EDTA in the presence of other metals. Experimental results are given for a few examples. Radiocomplexometric titrations of zinc in the presence of other metals have so far been carried out only by means of solvent extraction as a phase separating system. DUNCAN and THOMAS, 2 KORENMAN et al. 3 and SPITZY 4 succeeded in titrating mixtures of cobalt and zinc, mercury and zinc, and silver and zinc, using dithizone as the titrant. The titration of copper and zinc, however, was only possible by carrying out two titrations at different pH values, a Very few methods have so far been proposed for the titration of three components in the presence of each other. SPITZY 4 titrated mercury, silver and zinc, and KORENMAN et al. 5 titrated mercury, copper and zinc, both using dithizone as the titrant and 2~ and 65Zn as indicators.