Cu2+ – fulvic acid chelation equilibrium in 0.1 m KCl at 25.0 °C

Cu2+ reacts with fulvic acid to form a site-bound chelate on the fulvic acid polymer molecules. It is deduced from literature evidence that this chelate is the same type that Cu2+ forms with salicylic acid. This is supported by a Job's continuous variations plot. The mass action quotient for the chelate formation in 0.1 m KCl at 25.0 °C has been measured as a function of the degree of ionization of the chelating carboxyl groups. The strength of the Cu2+ – fulvic acid chelate is comparable to that of other bidentate Cu2+ chelates.