Computed disjoining pressure isotherms are compared with experimentally measured isotherms obtained using ellipsometry. A detailed charge regulation model for amphoteric surfaces has been used to describe the glass-brine interface. The results of this model together with an electrochemical description of the mercury-brine interface have been used to numerically compute disjoining pressure isotherms for aqueous films between glass and mercury. These isotherms allow us to predict the stability of aqueous films in various systems of interest. A comparison between measured and computed disjoining pressure isotherms indicates a good agreement when a decay length of 35 Å is chosen for the hydration forces. The effects of brine pH, electrolyte concentration, and the potential on the mercury surface on the disjoining pressure isotherms and on the stability of thin aqueous films are discussed