Abstract: The apparatus and method of the present invention relate to a novel procedure for measuring the interfacial thinning that occurs during a droplet-liquid phase coalescence event. As an example, an aqueous drop is grown at the tip of a capillary submerged into an oil phase which is layered on top of a second aqueous phase. A capillary, which is made of stainless steel, serves as one electrode while a second electrode is immersed into the second aqueous phase beneath the capillary. The oil-aqueous interface is raised to the level of the droplet until the droplet is deformed. This deformation serves as a driving force to produce thinning of the protecting interfacial film who's drainage properties govern the eventual coalescence of the water droplet into the aqueous phase.

Abstract: A method is disclosed for providing data useful in evaluating the dynamics of surfactants used to reduce interfacial tension in a system having two immiscible liquids and one or more surfactants. The method involves rapidly growing a drop of a first liquid in the second liquid, but stopping the flow of the first liquid at some point before the drop detaches. The time it takes for the drop to form and detach is then measured. This process is repeated for different volume drops. The drop lifetimes can then be plotted against drop volumes, resulting in a curve which is related to the diffusional coefficient and concentration for the surfactant in the particular liquid/liquid system.

Abstract: Apparatus and methods for determining the liquid/liquid interfacial tension between immiscible liquids wherein a first liquid is introduced into a second liquid at a constant rate of flow sufficient to produce successive, uniform size drops which ascend or descend depending upon whether the first liquid has a lower or higher density than that of the second liquid. The apparatus and methods are particularly useful in evaluating the effectiveness of a surfactant and the dynamics of interfacial reduction. In practice, the first liquid is discharged into the second liquid through a nozzle having an outlet of very low surface area. The time required to produce a selected number of drops is inversely proportional to the ability of the surfactant to reduce interfacial tension between the two liquids.