Método de Aproximación de Puntos de Inflexión Experimentales. Aplicación al Cálculo de Disociación de Ácidos Débiles

Abstract

For the solution of a chemical problem such as the caracterization of ac id-base propert ies of weak ac ids. it's neccesary the effective determinat'ion of their succesive dissociat ion constants (Kaj), trying to obtain those ones that better express the available potentiometric data.
To this aim, programs that have been thought for the determination and fit of metal complexes are usually employed. without taking into account the importance of the calculation of acid dissociation constants itself, because this values will be usefull to describe the different systems under discussion.
In this work, we make an overall study of the titration function, obtaining initial values of Kai from the middle point between two inflection points, and then we fit them to calculate the concentration of equilibrium species.
The development of this work show a really reliable and robust method, that analize the first derivative in small intervals, approaching it by the central differences method. In this way, an interval containig an inflection point is looked for and once this interval is found, the approach is refined.
As an application of this method, we have developed a software with fully satisfactory results.