An absorptiometric determination of perchlorate by means of a novel coloured liquid anion exchanger

Abstract

A novel liquid anion exchanger can be prepared from tetra-n-hexylammonium iodide and Erdmann's salt, (NH 4)[Co(NH 3) 2(NO 2) 4]. When a solution of this quaternary erdmannate in a suitable organic solvent (e max = 15,700 at 355 mμ) is equilibrated with an aqueous solution of a salt, the coloured ermannate ion is displaced to a greater or less extent; the effect decreases in the order ClO 4 - > ClO 3 - > NO 3 - > Cl - > SO 4 2- etc. The effects of changes in the organic solvent composition, of ionic strength, and of other variables on the position of equilibrium have been studied with a view to defining the optimum conditions for the absorptiometric determination of perchlorate ion (≧25 μ) in the presence of chlorate and other ions. Methods are proposed for eliminating those ions that form insoluble silver salts and to allow for the presence of substantial proportions of chlorate or nitrate ions.