Ionic strength dependence of protonation constants of N-alkyl substituted open chain diamines in NaClaq

The protonation of nine N-alkyl substitited diamines was studied in NaCl(aq) in the ionic strength range 0.1 < I/mol.L(-1) < 5, at t = 25 degreesC. The dependence on ionic strength of protonation constants was taken into account by using two different models, namely a Debye-Huckel type equation and a simplified version of Pitzer equations. The dependence on N-alkyl substitution of both protonation constants and their parameters for the medium effects is discussed, and empirical relationships are reported.