Water from water-in-crude oil emulsions is separated by chemical demul-sification. Coalescence rates of water droplets have been studied in the presence of a demulsifier. Droplet size measurement was carried out by photomicrography. Fastest coalescence rate was observed during first one minute. Binary coalescence time during this period was 5·4 seconds when 50 mg/1 of demulsifier was added and 4·2 seconds in the presence of 100 mg/1 of demulsifier.