A Scatchard quasiparticle model was developed previously by the authors to account for protonation side reactions in trace metal complexation by organic ligands in an aqueous leaf litter extract. This model is inconsistent with the typical acid‐base behavior of organic acid mixtures expected at low pH. A detailed investigation of a mixture of monoprotic quasiparticles led to a new expression for the protonation side‐reaction coefficient that yields correct acid‐base chemistry at any pH. The new expression also requires quantitative revision of the reaction stoichiometries and pH‐independent conditional stability constants reported previously by the authors based on a Scatchard quasiparticle model of metal‐ organic complexes involving Cu or Al. Besides these quantitative effects, the revised results also emphasize the important conceptual point that quasiparticle models of protonation and metal complexation reactions are formulated and tested independently of one another.