Capillary Phenomena Part 5.—Equilibrium and Stability of Solid Cones in Fluid/Fluid Interfaces

Abstract

Conditions are given for the equilibrium paths followed by cones (axis vertical) in interfaces between two fluids, when raised and lowered by an applied force: using a tensiometer or a rigid (damped) device. Circumstances are described under which these conditions are stable. The instability and detachment of cones with contact angle θ < χ+ 90°, where χ is the half-angle at the apex of the cone generating triangle, at a maximum in the displacement of the cone apex gives a method of determining the fluid/fluid interfacial tension. Conditions under which cones can float unaided are also given. Comparison is made with the behaviour of other capillary systems.