where pCl = -log 10 (a Cl ). Note that the Donnan and Bethe potentials cancel out in the pair moves. This algorithm allows us to calculate the protonation state of polyions as a function of pH and salt concentration inside the reservoir. For systems of large volume fractions and low ionic strength such titration curves will differ significantly from the titration curves of isolated systems of the same polyelectrolyte concentration and salt content. However, if the reservoir contains large concentration of salt, the Donnan potential will be very small and the difference between pH of canonical and grand-canonical systems will vanish, see Eq.