Salt effects on the protonation of diethylenetriamine: a complex formation model

Abstract

Protonation constants of diethylenetriamine (dien) have been determined potentiometrically, using (H +/glass electrode in different aqueous media (NaCl, KCl, NaClO 4, NaI, NaNO 3, MgCl 2, CaCl 2 and tetraethylammonium iodide) at 25°C and 0 < I ⩽ = 1 mol 1 −1. Measurements at very low ionic strength and in KCl (0 < I ⩽ mol −1) were also carried out at different temperatures (10 ⩽ T ⩽ 40°C). The differences in 1g K j H values are explained using a complex formation model by taking into account the formation of (dien)H q X p and M(dien)H q , weak species (X = Cl −, ClO 4 −, I −, NO 3 −; M = Ca 2+, Mg 2+, tetraethylammonium cation). Formation thermodynamic parameters are given. The speciation of diethylenetriamine in mixed electrolytes is discussed in relation to the real composition of natural fluids.