Interaction of Dissimilar Plane Parallel Double Layers at Arbitrary Potential

The elliptic integrals related to the interaction between two dissimilar parallel plates (the potentials on two plates have the opposite sign) are expanded in the series for the smaller surface potential y₀ (or ¦y _d ¦) and the smaller integration constant C as well as the larger surface potential and the larger integration constant, respectively. The number of series terms required to obtain the interaction with six significant digits is not more than 5 when the surface potential is less than or equal to 20 if the series being fit for smaller y₀ and C is combined with the series being fit for larger y₀ and C. The approximate expressions with different precision can be obtained by retaining different number of series terms. The results of Devereux O. F. and de Bruyn P. L. are discovered to be incorrect when absolute value of the surface potential is very large or the integration constant is very large or very small.