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Fig. 1. Schematic view of IP in ion-conductive rocks (according to Fridrikhsberg and Sidorova, 1961; Dukhin and Derjaguin, 1974; Dukhin and Shilov, 1974). (a) Scheme of electrical double layer at a negatively charged particle surface; 
, ß, and 
denote solid phase, Helmholtz layer, and diffuse layer, respectively. (b) Schematic distribution of cation (Cc) and anion (Ca) concentrations in the EDL; C0 is the equilibrium ion concentration outside the EDL. (c) Excess and deficiency in ion concentration around a polarized charged spherical particle; dotted arrows indicate the local diffusion flows represented by both cations and anions, dashed arrows show the local diffusion flows near the solid surface mostly represented by cations, solid arrow shows the electric field direction. (d) Excess and deficiency in ion concentration along a polarized throat; diffusion flows and electric field same as in Part c. (e) Schematic distribution of the ion concentration around a polarized spherical particle or along a polarized pore throat; C* denotes the excess concentration produced by the polarizing electric field.
