The four types of ionic equilibria--acid-base, redox, precipitation, and complexation--have certain similarities, which has led some authors to develop a unified treatment of them. These authors have highlighted the common aspects and tried to find a systemization of the equilibria that would facilitate learning them. In this unified treatment, ionic reactions are interpreted as particle exchanges--involving protons, electrons, or ligands--between a donor and an acceptor of two conjugate pairs. The unified treatment proposes a graphic solution to the equilibria problems, using diagrams that employ the logarithm of the concentration of the exchanged particle as the variable. This paper presents the application of the precipitation-solubility equilibrium and describes the usefulness of such diagrams for solving solubility problems. (Contains 2 tables, 1 figure, and 2 notes.)