A novel technique for studying the stability of emulsions has been developed. Owing to the fact that emulsion turbidity is a function of particle concentration and size, the stability of emulsions can be determined by measuring the change in turbidity with time. The relationship between turbidity and particle size and concentration is derived for a polydispersed emulsion. The stability of acoustically prepared emulsions determined by measuring the initial mean particle size and changes in emulsion turbidity is compared with the stability determined from scanning electron microscope measurements of the particle growth rate. The agreement between the two methods is excellent.

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A general dynamic equation is derived describing the behavior of a polydispersed emulsion in which Brownian flocculation, sedimentation-flocculation, and creaming are taking place simultaneously. The resulting equation consists of a set of coupled partial differential equations, which are solved numerically to predict changes in particle concentration and size distribution as a function of time and position. Predictions are also made for various limiting cases, such as negligible creaming, negligible flocculation, and for various degrees of electrostatic stabilization. A cyclic change in particle size distribution is observed when flocculation and creaming occur simultaneously.

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