On the complex formation equilibria between iron (III) and sulfate ions.
The equilibria have been investigated at 25 degrees C in 3 M NaClO4 using potentiometry, glass and redox Fe3+/Fe2+ half-cells, and UV optical absorptiometry. The concentration of the reagents was chosen in the intervals: 10(-4) < or = [Fe(III)] < or = 5.10(-3) M, 0.01 < or = [SO4(2-)]tot < or = 0.65 M. The value of [H+] was kept at 0.1 M or more to reduce the hydrolysis of the Fe3+ ion to less than 1%. Auxiliary constants, corresponding to the formation of Fe(II)-sulfate complexes and to the association of H+ with SO4(2-) ions, were taken from previous determinations. The experimental data could be explained with the equilibria [formula: see text] Equilibrium constants at infinite dilution, log beta 101 degrees = 3.82 +/- 0.17, log beta 102 degrees = 5.75 +/- 0.17 and log beta 111 degrees = 3.68 +/- 0.35, have been evaluated by applying the specific interaction theory.
Dipartimento di Chimica dell'Università Federico II, Via Cinthia 45, 80126-Napoli. ciavatta@chemistry.unina.it
Liberato
L
Ciavatta
Gaetano
G
De Tommaso
Mauro
M
Iuliano
D005290:Ferric Compounds / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*
D005290:Ferric Compounds; D007477:Ions; D013431:Sulfates