POTENTIOMETRIC STUDY OF THE PROTONATION EQUILIBRIA OF TARTARIC ACID IN AQUEOUS SODIUM-PERCHLORATE SOLUTIONS AT 25-DEGREES-C - CONSTRUCTION OF A THERMODYNAMIC MODEL

The protonation equilibria of the tartrate ion have been studied using an automated potentiometric system. The temperature was kept constant at 25 degrees C and the ionic strength was 0.5, 1.0, 2.0 and 3.0 mol dm(-3) in NaClO4. The experimental constants, obtained at different ionic strengths. were correlated by means of the modified Bromley theory and the thermodynamic protonation constants found to be log degrees beta(1) = 4.36 +/- 0.02 and log degrees beta(2) = 7.36 +/- 0.02. The possibility of the formation of mixed sodium species is also discussed.