FERRIC BORATE FORMATION IN AQUEOUS-SOLUTION

Potentiometric analyses indicate that previous investigations have ove restimated the stability of ferric berate complexes. The FeB(OH)(4)(2) formation constant result obtained in the present work is (B) beta(1 ) = [FeB(OH)(4)(2+)][H+][Fe3+](-1)[B(OH)(3)](-1) = (5.4+/-0.3)x10(-3) at 25.0 degrees C and 0.7 molal ionic strength. Our result indicates that solution concentrations of FeOH2+ and FeB(OH)(4)(2+) are approxim ately equal in aqueous solution for boric acid concentrations on the o rder of 0.3 molal. Fe(B(OH)(4))(2)(+) is a minor species in solution c ompared to FeB(OH)(4)(2+) for conditions such that [B(OH)(3)][H+](-1) less than or equal to 350, and ferric berate complexation is insignifi cant in solutions such as seawater where [B(OH)(3)] less than or equal to 4x10(-4) molal.