With eqns. 28 and 29 it is now possible to calculate the integral double-layer capacitance as a function of ψ0 and the electrolyte concentration. The ability of the double layer to store charge in response to a small change in the potential ∂σ0/∂ψ0 is defined as the differential double-layer capacitance, Cdif, and can be calculated using eqns. 28 and 29: