Titrations of Fulvic Acid Fractions I: Interactions Influencing the Dissociation/Reprotonation Equilibria

Summary Potentiometric titrations were performed on solutions of a polysaccharide fraction and a polycarboxylic acid fraction of fulvic acid. Accurate titration end points were determined by the application of Gran's equivalence point techniques. Reverse titrations did not follow identical paths to the forward ones because hydroxyl ions were consumed after the end points of the titrations against alkali had been reached. Analyses of the dissociation and reprotonation data demonstrate that electrostatic interactions alone cannot account for the calculated equilibria. The anomalous dissociation/reprotonation equilibria can be explained by the existence of inter‐ and intramolecular hydrogen bonds among functional groups on the fractions.