“…A second cause of their diversity is that most of the models were constructed by equating their predictions of the specific net proton charge (σ H ) with experimental data on the relative specific net proton charge (δσ H,titr ), which is the change in σ H from its initial value as observed during an acid-base titration experiment [29,30]. If σ H,init is the net proton surface charge at the beginning of a titration experiment, σ H and δσ H,titr are related through…”