A criterion of the stability of electrified liquid I liquid interfaces, which requires the second derivative of interfacial tension), with respect to the phase-boundary potential Delta(O)(W)phi be negative, that is, (partial derivative(2)gamma/Delta(O)(W)phi(2))(T. P. uj) < 0, has been shown to be violated to give an instability window in the range of Delta(O)(W)phi values. The interplay of adsorption and partition of ionic surfactant can lead to the adsorption of the surfactant only in a limited range of Delta(O)(W)phi; the adsorption reaches a maximum at a value of Delta(O)(W)phi around the standard ion-transfer potential of the surfactant. In this range, the electrocapillary curve may have a positive curvature. This means that (partial derivative(2)gamma/partial derivativeDelta(O)(W)phi(2))(T. P. muj) > 0, which implies that the double-layer capacitance is negative. Instead of taking this physically unrealistic state, the interface escapes from the unstable state by dissipating energy through spontaneous emulsification or other Marangonitype movements of the interface. Unlike the well-known condition for electroemulsification in which gamma is close to zero, the criterion of the electrochemical instability, (partial derivative(2)gamma/partial derivativeDelta(O)(W)phi(2))(T. P. muj) > 0, Wo can explain the spontaneous emulsification in liquid-liquid two-phase systems at a positive finite value of gamma and the regular irregularity commonly seen in the transfer of surface-active ions across the electrified liquid \ liquid interface.