Fig. 10.2: Methods of charging of a surface immersed in an electrolyte [4]

The total energy of interaction per unit area between the two plates is given by:

In the original theory provided by Deryaguin et al, the acid-base interactions are not considered while writing the expression for . In fact, they were not even known at that time to have been affected the interactions between two particles. So, continuing with that we will, in our current discussion, neglect Acid-Base term.