When two small bubbles approach each other

a dimpled thin film is formed between them. A model is developed for the dynamics of the thinning film with tangential mobile interfaces

in which the London -van der Waals forces are recognized. The model predicts the coalescence time

which is the time required for the thinning and rupture of the liquid film

given only the radii of the two bubbles and the required physical properties of the bulk fluid and interface. A more general expression for coalescence time is derived. It indicates that the surface viscosities play an important role in determining the surface mobility. The predicted result is in good agreement with previous experimental results.