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This article discusses the effect of solvent on the Gibbs energies of transferring succinic acid from water to ethanol solution. The Gibbs energies of transferring succinic acid in H2O – EtOH are determined according to solubility. The content of ethanol in mixed solvent was 0.0; 0.1; 0.3; 0.5 and 0.7 mole fraction. The results show that the ΔtrG0 value of succinic acid take negative value and increase with increasing ethanol concentration in mixed solvent. The first and second dissociation constants of succinic acid have been determined by potentiometric titration at ionic strength of 0,1M NaClO4 at 298.15K. Universal interpretation of the changes acid –base properties of succinic acid in mixed solvent is the application of solvation approach. It is shown that, the main contribution to the shift of the acid – base equilibria of succinic acid in water –ethanol mixed solvent comes from weakening of the solvation of deprotonated form succinic acid.