Stabilizing effects of surface‐active agents on a film flow

The effects of surface-active agents on the stability of a liquid film is reinvestigated. The present analysis differs from the previous works in the treatment of the surface boundary conditions. The well-known damping and stabilizing effects of surface-active agents are shown to be due to the redistribution of surface material caused by wave motions and diffusion. The equations of neutral stability for both cases of soluble and insoluble surface-active agents are obtained.