THE EFFECT OF SURFACE AND HYDRODYNAMIC-FORCES ON THE SHAPE OF A FLUIDDROP APPROACHING A SOLID-SURFACE

This paper describes an experiment designed to measure surface and hyd rodynamic forces between a mercury drop and a flat mica surface immers ed in an aqueous medium. An optical interference technique allows meas urement of the shape of the mercury drop as well as its distance from the mica, for various conditions of applied potential, applied pressur e, and solution conditions. This enables a detailed exploration of the surface forces, particularly double-layer forces, between mercury and mica. A theoretical analysis of drop shape under the influence of sur face forces shows that deformation of the drop is a sensitive indicato r of the forces, as well as being a very important factor in establish ing the overall interaction between the solid and the fluid.