REACTION IN ION-EXCHANGERS - CHARACTERIZATION OF THE ETHYLENEDIAMINE PROTONATION EQUILIBRIUM IN A SULFONIC MEMBRANE .2. EQUILIBRIUM IN ACIDIFIED SOLUTIONS OF ETHYLENEDIAMINE

The protonation equilibria of ethylenediamine (EDA) in cation-exchange membranes are considered in the case of acidified solutions of EDA. T wo methods are compared to calculate the apparent equilibrium constant s. The first method involves the conversion of the sorbed EDAH(2)(2+) into EDA by sodium hydroxide followed by an acidic titration. In the s econd method, the membrane is dipped in a solution of carbamic acid (E DACO(2)(+/-)) and the H+ counterions are quantitatively substituted fo r EDAH(2)(2+). The titration of the remaining EDACO(2)(+/-) by an HCl solution permits to determine the amount of H+ in the membrane at equi librium. The second method allows to calculate accurately the apparent equilibrium constant K-1 and the apparent acidity constants K-a1* an d K-a2. The apparent and real constants are compared.