Dependence of interelectrode impedance on the metal type, electrode area of processing its working surface and current frequency was investigated. A series of 15 materials according to their impedance characteristics were obtained and a relationship between a sequence of preparations of heavy metals according to the density of albuminates they produced was established. It was demonstrated, that electrode difference in impedance of extreme members of the series was considerable in the zone of low frequency and was insignificant in the zone above 10-50 Khz.