The tension of composite fluid surfaces and the mechanical stability of films of fluid

Abstract

The tension of a composite surface composed of a fully separated layer of one fluid (say oil) spread over a mass of another fluid (say water) is given by the equation T = T A +T AB , where A and B denote respectively the oil layer (exterior layer) and the water (interior mass). If z be the depth of the exterior layer, then, for a given temperature θ , the quantity T A will reach a constant value when z is either > twice the range of action of the oil molecules on each other, or > the sum of two values, namely, the range of action of oil molecules on each other, and of the oil molecules on the water molecules. Let Z be the lowest value of Z for which T θ is constant: ½Z is equal to the greater of two quantities, the range of action of the molecules of oil, or the mean of this value plus the range of action of these molecules upon the molecules of water.