The hydrolysis and fluoride complexation behavior of Fe(III) at 25 degrees C and 0.68 molal ionic strength

Fe(III) hydrolysis and fluoride complexation behavior was examined in 0.68 molal sodium perchlorate at 25 degrees C. Our assessment of the complexation of Fe(III) by fluoride ions produced the following results: log (F) beta(1) = 5.15(5), log (F) beta(2) = 9.10(7), log (F) beta(3) = 11.96, log (F) beta(4) = 13.7 where (F) beta(n) = [FeFn(3-n+)][Fe3+](-1)[F-](-n). The stepwise fluoride complexation constants, K-F(n+1), obtained in our work (where K-F(n+1) = (F) beta(n+1)/(F) beta(n)) indicate that K-n+1/K-n = 0.072 +/- 0.01. Formation constants for equilibria, Fe3+ + nH(2)O reversible arrow Fe(OH)(n)((3-n)+) + nH(+), expressed in the form beta(n)* = [Fe(OH)(n)((3-n)+)][H+](n)[Fe3+](-1), were estimated as log beta(1)* = -2.754, and log beta(2)* less than or equal to -7. Our study indicates that the results of previous hydrolysis investigations include very large overestimates of Fe(OH)(2)(+) formation constants.