A Videomicroscopic Investigation of Coupled Reversible Flocculation and Coalescence at Singlet-Doublet Equilibrium in an O/W Emulsion of Low Density Contrast

Video enhanced microscopy (VEM) enables direct investigation of dilute emulsions. A practical and effective preparative technique utilizes microslides, which are flat, rectangular microcapillaries made from borosilicate glass. Experimental difficulties due to droplet sedimentation and droplet-microslide wall interaction can be drastically reduced, even eliminated, by the use of low density contrast emulsions, i.e. emulsions where the densities of the dispersed and continuous phases are not very different. The dichlorodecane (DCD)-in-water emulsion is an example of such a system. This system.can as such be used for measurement of the time of the elementary act of coalescence, calculated from the evolution in the droplet size distribution. The developing distributions can be determined through automated VEM.

In this paper we discuss the perspective for elaboration of a standard method for the determination of an averaged time for the elementary act of coalescence. The experimental basis is automated measurement of the time dependence of the droplet size distribution, as applied to dilute DCD/w emulsions at singlet-doublet equilibrium.