The strong preference of ionized states in the polyelectrolyte complex affects not only their populations within this phase but also the overall partitioning of the diprotic acid between the two phases. In Figure ) we show that the partition coefficient of the diprotic acid, K SuA,tot , strongly increases as a function of the pH. At low pH values, when the uncharged state dominates, the partitioning is governed by the steric repulsion, resulting in K SuA,tot < 1. As soon as the monovalent state starts to dominate, we observe K SuA,tot > 1 as a consequence of electrostatic interactions. As the pH is further increased, K SuA,tot continues to increase until it saturates at a value of K SuA,tot ≈ 5, which is slightly lower than the partition coefficients of divalent ions observed in Sec. 3.2. This difference can be explained by the concentration of the diprotic acid being about six times higher than the concentration of divalent salt in Sec. 3.2. This higher concentration was required to ensure good statistics on partitioning of individual ionization states. As a side effect, it caused that the fully ionized diprotic acid significantly affects the ionic strength in the supernatant, and thereby also the activity coefficients of all other ions.