DEFORMATION OF FLUID INTERFACES UNDER DOUBLE-LAYER FORCES STABILIZES BUBBLE DISPERSIONS

A theoretical study of the colloidal interaction between two identical fluid drops (i.e., gas bubbles) forms the basis for the proposal of a possible mechanism by which salt inhibition of bubble coalescence occ urs. Recent speculations attempting to describe this phenomenon were f ounded on the assumption that electrostatic double-layer forces are no t relevant. In complete contradiction to this claim, the present resul ts indicate that double-layer forces between the deformable bubble int erfaces infer precisely the same behavior observed with salt addition: bubble coalescence is predicted to occur in water or in low electroly te solutions, but is hindered once the electrolyte concentration is in creased sufficiently. In other words, low-salt solutions favor large b ubbles, high-salt solutions favor small bubbles. In this symmetric sys tem, assuming fixed but physically appropriate conditions, a given bub ble size determines a critical electrolyte concentration above which c oalescence is not possible.