Study of Metal-1,10-Phenanthroline Complex Equilibria by Potentiometric Measurements

Table 1

The Acid Dissociation Constants of 1,10-phenanthroline (Phen) and the Stability Constants of the Sc(III), Y(III) and La(III)-Phen Complexes (25 ± 0.1°C, I = 0.1 M KNO₃).

Row	Equilibrium	Constant	Phen	Sc(III)	Y(III)	La(III)
1	H2L^+2⇌HL^+ + H^+	log KH2L	1.50 ± 0.08 (1.95) [30]
	HL^+⇌L + H^+	log KHL	4.92 ± 0.08 (4.77) [30]
2	M^3++ L⇌ML^+3	log β 1		10.83 ± 0.02	9.47 ± 0.04	8.47 ± 0.03
	M^3++ 2L⇌ML2^+3	log β 2		20.70 ± 0.02	—	—