Enthalpy and entropy changes associated with the ionization of hydroxyethylenediaminetriacetic acid

Abstract

Enthalpy ck anges associated with the three ionizations of hydroxyethylenediarninetriacetic acid have been measured calorimetrically. The values reported for 25°C and p = 0.1 (KCI) are AH1 = -1.12&0.12, AH2 = +3.09&0.05 and AH3 = +6.65 h0.08 kcal.mole-l, respectively. From these data and from the acid dissociation constants, entropy changes are calculated. The results are compared with literature data obtained by the determination as a function of temperature of the acid dissociation constants.