ABSTRACT
A foam is a dispersion of a gas in a liquid. In most cases, such dispersions are considered to be a nuisance rather than a desired product. Thus, foams can generate much trouble when they are formed during distillation and when they originate on using detergent solutions. The existence of a surface tension gradient in the liquid film separating two gas bubbles is also required for kinetically stabilizing a liquid film against collapse. Formation of a local hole in a film is preceded by the generation of a thinner spot. In foam generation, this adjustment of the surface tension occurs during the drainage of the thick liquid films formed between the gas bubbles in the initial stages. During this drainage, the original surfaces of the liquid expand, and therefore by a certain volume element of the liquid new surfaces are generated continuously. Drainage rate is inversely proportional to the viscosity of the liquid involved.
