The maximum value for a repulsion force considered in this theory is related to the surface  potential and zeta potential of the system this theory models.
Under this system, the C.C.C occurs when the tangent of the primary maximum of the potential energy diagram is zero.  The predictions of Schulze-Hardy rules are very similar to those made by this theory, which is only applicable to systems  in which the advancing contact angles lie between 15 and 64 degrees. This theory can be modified by considering the  impact of oscillatory forces or hydration forces in its (*) "extended" form. It fails when describing systems with highly  hydrophilic or hydrophobic particles.  The maximum value for a repulsion force considered in this theory is related to the surface  potential and zeta potential of the system this theory models. For 10 points, name this theory that uses electrostatic repulsions and  Van der Waals attractions to explain differential stability of colloids and is named for its four developers.
Under this system, the C.C.C occurs when the tangent of the primary maximum of the potential energy diagram is zero.  
DLVO theory [or Derjaguin Landau Verwey Overbee Theory]