The degree of dissociation of ionic surfactant shells within a W/O microdroplet is investigated on the basis of the Poisson-Boltzmann equation and locally ideal mixing assumption. The degree of dissociation is the result of the competition between the entropy associated with counterions in the aqueous core and mixing of surfactant ions with associated surfactants on the shell, and the electrostatic energy. The degree of dissociation is found to depend on the geometry and is in the order: Two planar surfaces > cylinder > sphere of the same size. Moreover, for the same geometry, the degree of dissociation increases with the size of the droplet. The free energy change associated with a droplet due to dissociation is obtained. The effect of the solubilization of a neutral particle on the degree of dissociation is also studied. The solubilization is found to hinder the dissociation.