Ionic strength dependence of formation constants-XVIII. The hydrolysis of iron(III) in aqueous KNO3 solutions

Abstract

The hydrolysis of iron(III) was studied potentiometrically at different ionic strengths in KNO3 aqueous solutions, at 25°C, to determine the dependence of hydrolysis constants on ionic strength (nitrate media), to check the existence of nitrate-ferric ion interactions, and to confirm the formation of high polymeric species. Under the experimental conditions 0.03 ≤ I (KNO3) ≤ 1M, 0.3 ≤ C ≤ 12 mM, the species Fe(OH)2+, Fe2(OH)4+2, Fe(OH)+2 and Fe12(OH)2+34 were found, and the hydrolysis constants log β11 = 2.20, log β12 = -2.91, log β22 = -5.7, log β12,34 = -48.9 (I = 0M) were calculated. The ionic strength dependence of hydrolysis constants is quite close to that found for several protonation and metal complex formation constants reported elsewhere. © 1994.