Détermination de la stabilité du complexonate peu soluble à partir des données pH-métriques

A new method has been developed for the determination of the solubility product of complexonate of known composition; because of the initial composition of the heterogeneous mixture (lot a), it uses only the equilibrium values of the pH. For the determination of the stability constant in solution, these data have been completed with information on the solubility of the precipitate. We have shown that, on the basis of lot a and in the absence of reactions of formation of complexes in solution, it is possible to evaluate the equilibrium constants, since they are residuals of the compositions of the precipitate. We conclude on the possibility of applying this method to the test and standardization of ion-selective electrodes. The qualities and defect of the method are discussed. Otherwise, the values for the equilibrium constants and the equilibrium as well as the residual concentrations that we have calculated for a series of real systems from known experimental data are in good accord with those reported in tables under the same conditions.Key words: potentiometric method, heterogeneous system, slightly soluble complexonate, complexone, equilibrium concentration, solubility product, stability constant, hydrolysis reaction.[Journal Translation]