Solvent effects on the dissociation reactions of tartaric, maleic and phthalic acids; comparative study and analysis of thermodynamic functions

The first and second dissociation constants of tartaric, maleic and phthalic acids have been determined using EMF method in water-ethanol mixed solvents, over a wide range of solvent composition (0-60 wt% ethanol) at six different temperatures (ranging from 30 to 55 degrees C at intervals of 5 degrees C). The thermodynamic parameters (DeltaG degrees , DeltaH degrees and DeltaS degrees ) for the first and the second ionization reactions were calculated from the well known equations. The results have been discussed in terms of the solute-solvent interactions and were compared with those of malic, malonic and succinic acids in the same mixed solvents.