A pendant drop tensiometry apparatus aided by video-image digitization technology was established

by which static interface or surface tension of some liquids was measured with satisfactory results.In order to study the effect of emulsifier concentration on emulsion stability

dynamic interfacial tension was measured between toluene and water against concentration of Tween 60(Polyoxyethylene(20) stearyl-sorbitanate). As expected

higher concentration is the Tween 60 solution in toluene injected into the toluene phase

faster falls the interface tension between toluene and water.Furthermore

it reveals interestingly that two steps of diffusion occur in the system

i.e .

at low and high concentration

after the surfactant solution is injected.The characteristic process of dynamic interface tension can be ascribed to diffusion control because of linearity between interface tension and the minus second root of aging time.The discovery is correlated to the fact that much higher concentration of surfactant above its critical micelle concentration is often required when a stable emulsion is planned to prepare.