It is the purpose of surfactants to cause materials that do not dissolve in water (like oil, grease and dichloromethane) to form an emulsion with water. We want to be able to separate the aqueous phase from the dichloromethane phase, so the last thing we want is an emulsion of the two. Consequently, as you extract the caffeine from the water into the dichloromethane do not shake the separatory funnel vigorously. The flow diagram below summarizes the extraction portion of the experiment.