The electrical susceptibility of the Silicon-electrolyte interface has been studied when the electrical irradiation field is parallel to the junction. In the High Frequency (H.F.) range, the absorption exhibits one maximum depending on the voltage applied between the semi-conductor and the electrolyte. This drastic variation, specially the maximum, is at our opinion, due to the minority carriers. It is modified by irradiation. In the microwave range, the maximum of absorption is rather difficult to observe probably because electrochemical reactions occur. The variation of dispersion is negative, we explain that by considering the high frequency local field.