Hydrolysis of (CH3)Hg+ in different ionic media:: Salt effects and complex formation

The hydrolysis of monomethylmercury(II) was studied potentiometrically, in NaNO(3), Na(2)SO(4), and NaCl aqueous solution, in a wide range of ionic strengths (NaNO(3), 0 less than or equal to I less than or equal to 3.25; Na(2)SO(4), 0 less than or equal to I less than or equal to 1; NaCl, 0 less than or equal to I less than or equal to 3 mol dm(-3)) and at t = 25 degrees C. For the reaction (CH(3))Hg(+) = (CH(3))Hg(OH)(o) + H(+), we found log K(1) = -4.528 (I = 0 mol dm(-3)). The species [(CH(3))Hg](2)(OH)(+) was also found, with log beta(2) = -2.15. Monomethylmercury(II) forms quite strong complexes with Cl(-) (log K = 5.45, I = 0 mol dm(-3)) and SO(4)(2-)(log K = 2.64, I = 0 mol dm(-3)). The dependence on ionic strength of formation constants was considered by using a Debye-Huckel type equation. Hydrolysis and complex formation constants (at different ionic strengths) obtained were used to calculate the interaction parameters of Fitter equations.