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Potentiometric And Thermodynamic Studies Of The Protonation Equilibria And Metal Ions Complexation Of Some Zwittrerionic Buffers In NaNO3 Solutions In Water And In Mixtures Of Water And Dioxane

Mohamed Taha, Alaa T.Ahmed, Shad A.Saqr, Sawsan A.Mohamed

The protonation equilibria for some selected zwitterionic buffers in solutions have been studied pH-potentiometrically. The second stage dissociation constants(pKa2) of zwitterionic buffers and the thermodynamic quantities(ΔG, ΔH, and ΔS) have been derived at different temperatures in water at ionic strength I=0.1 mol·dm-3 NaNO3 and in the presence of 10%, 30%, and 50%(w/w) dioxine. Titrations were also carried out in water ionic strengths of(0.15, 0.20, and 0.25) mol· dm-3NaNO3. The interactions between the zwitterionic buffers with some metal ions were also studied at different temperatures and in the presence of 10%, 30%, and 50%(w/w) dioxane by using potentiometry. The thermodynamic stability constants were calculated as well as the thermodynamic quantities for the 1:1 binary complexation.