The model assuming that the elastic force of interfacial tension counteracts introduction of ions into adjacent electrolyte solution is discussed. The main electrochemical properties of ITIES are analyzed on the basis of this model. It is shown that many of experimental results of study of double-layer capacitance, potential drop across the inner layer, kinetics of simple and facilitated ion transfer as well as resolvation energy of hydrophobic ions are in good agreement with predictions drawn from the model. It is concluded that ITIES acquire the property of polarizability although heterogeneous step of simple ion transfer is reversible. The performed theoretical analysis of transfer of ions of supporting electrolytes has offered a simple equation to describe experimental voltammetric curves and to obtain a quantitative criterion of the polarizability.