DEPROTONATION ENERGETICS OF PURINE AND URIC-ACID IN WATER FROM EMF-MEASUREMENTS AT DIFFERENT TEMPERATURES

The first step and second step deprotonation constants of purine and u ric acid in water have been determined from emf measurements of cells comprising H-2 and Ag-AgI electrodes at five equidistant temperatures ranging from 15-degrees-35-degrees-C. The pK values are fitted in the temperature equation pK = AT-1 + B + CT by least squares method and th e related standard free energies (DELTA G-degree), entropies (DELTA S- degree) and enthalphies (DELTA H-degree) of the deprotonation processe s in water have also been evaluated using the values of the coefficien ts A, B and C of the respective acids.