Characteristics of electrical demulsification of water in oil emulsions Were studied experimentally. by using a flow-type column separator equipped with perforate plate electrodes at the top and the bottom of the column. The system of kerosene-span 80 surfactant and NaCl aqueous solution was used as W/O emulsion. The effects of pulsed DC and AC voltages applied on the demulsification rate of the emulsions were investigated, and the changes in droplet size distribution and dispersed phase holdup in the emulsion phase demulsifying under applied electric fields were examined by, in situ ()observation as a basis for understanding the demulsification behavior. Also the effect of the applied voltage on residual,water content in the demulsified oil phase was examined, The results are expected to be practically useful as design and operational principles. for the separator.