Abstract
Emulsion stability was studied by measurements of coalescence rates of small single drops of water or decane from either side of a plane n-decane/water interface, following Cockbain's multi-drop method. The mechanisms of viscous drainage and strength of interfacial film are discussed based on the distribution of lifetime of drops at the interface. The distribution curve expressing the relation between number of drops N and drop life t generally consists of a flat induction part with lifetime below τ and a successive decaying part where lnN decreases linearly with increase with lifetime above τ. The coalescence rate (k) is obtained from the slope of the plot of the decaying part. k and τ were found to have essentially the same values for both decane and water drops in the absence of a surfactant, whereas they differed considerably from each other. The activation energies for coalescence as determined from the temperature dependence of τ and k are compared and the mechanism of coalescence is discussed.
