The choice of demulgators for separating crude oil emulsions is still done empirically. The knowledge of the charge of crude oil compounds is essential for the amount of needed demulsifiers. By using the Particle Charge Detector of the Mutek Company the surface charges of these compounds could be determined. The suspension will be titrated with demulsifier. Surface active compounds are enriched within the colloids of crude oil, i.e. the resins and the asphaltenes. The asphaltenes could be divided into the easy, medium and difficult soluble asphaltenes. The streaming potential of the colloids and their corresponding total charge could be determined successfully. With increasing quantity of asphaltenes the charge consumption increase almost linearily. The heavy soluble asphaltenes are needing the highest share of demulsifiers followed by the middle and the light soluble asphaltenes. The resins only show very small charge consumption.