The coalescence of closely spaced drops when they are at different electric potentials

Abstract

To discuss the coalescence of two neighbouring drops at different electric potentials as a problem of stability it is necessary to assume that they are held on fixed supports, for other­wise there is no equilibrium state to become unstable. In this work these supports are two equal rings. Experiments at first using soap films instead of drops, are in agreement with the analysis when the geometry of the rings conforms to the requirements of the theory. When the distance between the drops is small compared with that between the supporting rings the critical potential difference does not depend on the size or position of the rings but only on the radius of the two drops and the distance between them. Under these circum­stances a simple expression derived from computer solutions of the relevant equation has been found. This limiting formula is in agreement with some unpublished experiments with water drops carried out by J. Latham, and also with experiments in which instability was observed when neighbouring glycerine drops were subjected to potential differences as low as 9·8 V.