Titration curves of fulvic acid: the analytical chemistry of a weak acid polyelectrolyte

Abstract

The fulvic acid molecular weight fraction studied has two general types of carboxyl groups, one of which is ortho to phenolic -OH groups. The number of each type per gram of fulvic acid has been measured. The acid ionization equilibrium of each type has been calculated as a function of its degree of ionization in 0.1 m KC1 at 25.0 "C. In both cases the acid strength decreases with increasing degree of ionization. The sample used shows the potentiometric titration behavior expected of a low molecular weight polyelectrolyte.

Conductometric analysis of polyelectrolytes in solution

“…[29,37,56,57,58,59,60,61,62], polyvinyl ether/maleic anhydride copolymers [51], fulvic acids (FA) [63], kaolinitic clays and clay-humic acid complexes [64], carboxymethylcellulose (H-CMC) [32,38], poly(acry1ic acid) (H-PAA), poly(methacry1ic acid) (H-PMA) [37], chondroitin sulfuric acid, heparin [65], polystyrene latices [55,66], and pectins [26].…”

“…FA have also been interpreted as reflecting different types of functional groups [70]. Gamble [63] attributed the descending part of the curve to strongly acidic carboxylic groups (on aromatic rings, ortho to phenolic-OH groups) and the rising part to more weakly acidic carboxylic groups. Arai and Kumada [29,60] categorized very weak (VW), weak (W) and strong ( S ) acidic functional groups, based on distinguishable stages in the titration curve.…”

Competition from Cu(II), Zn(II) and Cd(II) in Pb(II) Binding to Suwannee River Fulvic Acid

“…DEF is the cumulative site density as a function of the equilibrium constant. It is based on the differential intensity parameter, K*, which is a weighted average mean of the equilibrium constants K i , for all sites present in the humic substance (Gamble 1970;Altmann and Buffle 1988;Buffle and Filella 1995). The DEF is calculated as the first derivative of the product of the weighted average equilibrium function and a weighting factor.…”

Nature, properties and function of aluminum–humus complexes in volcanic soils

“…Two main types of chelate linkages have been suggested: one involving a COOH and an adjacent phenolic OH group to form a salicylate-like ring and the other involving two COOH groups in close proximity to form a phthalate-like ring (Schnitzer and Skinner, 1965;Gamble, 1970). The maximum binding capacity of humic substances is approximated by the content of acidic functional groups, primarily COOH moieties.…”