Figure 4.

The relationship between the Gibbs–Donnan factor for the reference permeating monovalent (left panel) or bivalent (right panel) cation (for example Na⁺ or Ca²⁺ in a solution with Cl⁻) and the ratio ${\mathrm{\gamma }}_{\text{np,2}}/{\mathrm{\gamma }}_{\text{np,1}}=Z_{\text{np,2}}{\text{C}}_{\text{np,2}}/{\text{Z}}_{\text{np,1}}{\text{C}}_{\text{np,1}}$ of equivalents of non-permeating species on the two sides of a permselective membrane, calculated according to Eq. (15) for different values of γ_np,1 (the case with known ion concentrations in compartment 1).