Estudos sobre linealização de curvas de titulações potenciometricas

AUTOR(ES)

Willian Ferreira da Costa

DATA DE PUBLICAÇÃO

1989

RESUMO

Two linear graphic methods were studied and the limits of their application were determined. The first linear method studied was applied to the titration of weak bases, and it is possible to determine the equivalence volume of titration and the dissociation constants of the titrated species simultaneously. The method was applied to titration of two weak bases, the acetate ion and the azide ion with dissociation constants nearly 10 The minimum concentration where it is possible applies this method was determined. The second linear method studied was applied to mixtures of strong acids with weak acids. It was possible to determine with this method the equivalence volume of each acid as well as their dissociation constants simultaneously. The method was applied to titrations of mixtures of strong acids and weakacids and the following parameters were determined where the method can be applied. a) minimum limit of concentration of the acids presentin the mixture, b) minimum difference of pka between the two weak acids, c) least value of pka of a weak acid to be determined in the presence of strong acid. It was possible to determine the best conditions where the linear method can be applied due to knowledge of the parametrs mentioned before. The second linear method studied was applied to the potentiometric titrations of humic substances(humic acid, fulvic acid and the mixture of both) where it was possible to determine the concentration and the dissociation constant of the acid groups present in these substances and also identify those groups.

ASSUNTO(S)

potenciometria

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