Regarding the difficulty of determining the inflection points in the potentiometric titration curve of humic acids by means of traditional methodologies, a Delphi program a Delphi program was developed for the multiparametric data adjustment in potentiometric titration. For this purpose, an iterative process was used, based on the Newton-Raphson method to estimate the roots of a polynomial. The humic acid potentiometric titration data, used in regressions, were obtained in an automated system of potentiometric titration. The program developed in Delphi language features greater versatility, ease of operation and better interaction with the user. The adjusted potentiometric titration curves overlap the experimental curves almost entirely. The pKa values and percentages of titrable groups of humic acids extracted from soil, adjustable parameters in the multiparametric regression, were comparable with those reported in the literature.
nonlinear regression; polyprotic acids; potentiometry; Delphi language
