THERMODYNAMICS OF COMPLEX-FORMATION OF AG(I) .10. INVESTIGATIONS ON COMPLEX EQUILIBRIA BETWEEN AG(I) AND THIOUREAS IN ETHANOL

The complex equilibria between Ag(I) and thiourea or N-alkyl-substitut ed thioureas have been investigated in ethanol by potentiometry at dif ferent temperatures in the range 0-45 degrees C. The free energy, enth alpy and entropy changes at 25 degrees C and ionic strength mu=0 for t he formation of mono-, bi- and tri-coordinate compounds are given. The investigated alcohols favour the complex formation, but specific fact ors operate on the transfer of each reaction from water to methanol to ethanol. Interaction between tetramethylthiourea and Ag(I) involves a different mechanism compared with the other thioureas owing to the di fferent electronic structure of the ligand. The ranked affinity sequen ces of the ligands follow different orders according to the coordinati on level of the substratum.