In Figure ), we plot a phase diagram, where we used the pressure-composition protocol from Figure to relate the composition of the supernatant and the co-existing interpolyelectrolyte complexes. The phase diagram manifests some typical features of polyelectrolyte complexation. First, the polymer volume fraction determined from our simulations is between ∼ 10% and ∼ 15% which is within the rather broad range reported by various experiments and simulations. Next, the interpolyelectrolyte complex density decreases with increasing c NaCl , as expected due to stronger electrostatic screening. This works well far enough from the critical point, when it is reasonable to assume that there is no polymer in the supernatant. However, our model cannot accurately predict that the interpolyelectrolyte complex eventually dissolves when the critical c NaCl reached. Nevertheless, our predictions of the phase coexistence remained self-consistent up to c NaCl ≈ 532mM. Accordingly, the critical salt concentration would be greater than 532mM, which is consistent with critical point reported in various studies, anywhere between 500mM and 3000mM, depending on specific parameters of the systems. Finally, in Figure ) we show that partition coefficients of NaCl between the two phases, obtained by dividing the salt concentrations at the end-points of the tielines in Figure , are commensurate with partition coefficients in interpolyelectrolyte complexes formed by poly(L-lysine)/poly(D,L-glutamic acid) polypeptides of length 50, measured in Ref. In the limit of low c NaCl , the partition ratio is slightly above unity, but it becomes smaller than one if c NaCl is increased, pointing to the preferential partitioning of monovalent ions into the supernatant phase. This behavior is in agreement not only with experiments but also with recent liquid state theories, which attribute it to steric repulsion and correlations due to the chain connectivity, both of which are explicitly included in our simulation model. The above studies also observe that at high c NaCl the partition ratio starts to increase and approaches unity close to the critical point. We do not observe this regime, as our model loses validity close to the critical point. Nevertheless, in Figure ) we see that the experimental critical c NaCl ≈ 850mM for the system reported in Ref., hence our simulations are likely to be self-consistent up to the roughly 532/850 ≈ 60% of the salt resistance.