Design criteria for electrostatic de-emulsifiers. Electrostatic de-emulsifiers have been successfully used over many years for desalting of crude oil. The emulsions used for this application are rather unstable and break down easily. Different equipment and conditions are required for highly stable emulsions, such as are used for liquid membrane permeation. To permit use of higher field strengths without danger of short circuiting this new equipment must be fitted with insulated electrodes, with preference being given to glass-insulated liquid electrodes. An important feature is also a defined distance between the electrodes which are arranged in concentric manner to increase the de-emulsification rate. The rate of deemulsification can also be increased by using high frequency (10 kHz) instead of the usual low frequency (50 Hz) alternating voltage.