Hydrolysis and chemical speciation of (C2H5)(2)Sn2+, (C2H5)(3)Sn+ and(C3H7)(3)Sn+ in aqueous media simulating the major composition of natural waters

The hydrolysis of (C2H5)2Sn2+, (C2H5)3Sn+ and (n-C3H7)3Sn+ has been studied, by potentiometric measurements ([H+]-glass electrode), in NaNO3, NaCl, NaCl/Na2SO4 mixtures and in a synthetic seawater (SSWE), as an ionic medium simulating the major composition of natural seawater, at different ionic strengths (0 ≤ I ≤ 5 mol dm−3) and salinities (15 ≤ S ≤ 45), and at t = 25 °C. Five hydrolytic species for (C2H5)2Sn2+, three for (C2H5)3Sn+ and two for (C3H7)3Sn+ are found. Interactions with the anion components of SSWE, considered as single-salt seawater, are determined by means of a complex formation model. A predictive equation for the calculation of unknown hydrolysis constants of trialkyltin(IV) cations, such as tributyltin(IV), in NaNO3, NaCl, and SSWE media at different ionic strengths is proposed. Equilibrium constants obtained are also used to determine the interaction parameters of Pitzer equations.