A Simplified Double Layer Model Constant Capacitance

A Simplified Double Layer Model (Constant Capacitance) 

The simplest structure of the double layer is the surface charge in one plane and the counter charge in a similar parallel plane. Then, to a first approximation, the double layer may be visualized as a parallel plate condenser of distance d between the two plates and with its capacitance, C 

This model is valid when the total surface charge is small in absolute magnitude or when the concentration of the inert electrolyte is large (compressed double layer). 

4 Surface Charge on Carbonates, Silicates,Sulfides and Phosphates 

Although we have used for exemplification largely the surfaces of hydrous oxides, the concepts given apply to all surfaces. As has been pointed out, most hydrous surfaces are characterized by functional groups that acquire charge by chemical interaction with H+, OH, metal ions and by ligands. (For the moment we ignore redox reactions.) 

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