THE "HCI EFFECT" in ANION-RESIN EXCHANGE

An explanation is offered for the interesting feature that distribution ratios of anions with strong-base exchange resins are generally lower from concentrated HCI solutions than from comparable LiCl solutions. It is suggested that this behavior is due to the invasion of the resin by non-exchange electrolyte at the high external-solution concentrations and to the partial association of the acid species in the resin phase. That is, because of the nature of the latter phase, normally strong acids are differentiated, the weaker ones partially associating. This does not occur as readily with the lithium salts, and so the preferential association of non-exchange H+ with the weaker- acid anion (Cl- in most of the cases studied) represses the absorption of the other anion as a non-exchange electrolyte. If the anion of interest were the anion of a weaker acid than that of the macroelectrolyte, the reverse of the usual behavior should occur, namely, exchange from acid solution should yield larger distribution ratios than exchange from lithium salt solutions. This is shown to be the case for CI- tracer exchanging with concentrated HBr and LiBr solutions. (auth)