Evaluation of the formation function [Formula: see text] for a system of monomeric and polymeric (condensed) acids in mutual equilibrium can account for the appearance of a network of formation curves with a crossover point at a fixed value of the coordinates [Formula: see text], pH. The value of [Formula: see text] at this isohydric point is equal to 1 − z/n, where n is the degree of condensation and z the basicity of the condensed acid. A third formation curve is unlikely to pass through the same isohydric coordinates, so that the system is very probably restricted to two predominant species in equilibrium. These conclusions confirm the work of Carpéni and collaborators, but appear to have been derived in a different way.