The limits of the applicability of an approximate method for describing the structure of a dilute solution of an electrolyte in neutral and charged flat slots, which was developed in the framework of the self-consistent-field approximation, have been investigated. It has been shown that a modified Onsager-Samaras approximation, in whose framework the shielding length in a pore is assumed to be constant but different from the shielding length in the bulk, can be employed as the zeroth approximation. The corrections to this approximation are of appreciable magnitude in the region of variation of the parameters where the interaction of the ions located in the central part of a pore with the polarized interfaces may be neglected.
