ABSTRACT
It is clear from the figure that the part of the foam from E to F has an excess (compared to equilibrium) of continuous phase given by V1=Area (AEF), whereas the part of the foam from F to G has a deficiency of continuous phase given by V2=Area (BFG). Thus:
ε0L0−Vc=V1−V2 (110)
Now if V1=V2 (i.e., if Vc=ε0L0), the amount of continuous phase that the upper part (EF) loses as it attains equilibrium is just equal to the amount the lower part needs. Thus, at equilibrium, the ε profile is given by curve (AFB) and the length of the column remains unchanged. On the other hand, if V1>V2 (i.e., if ε0L0>Vc) (see Fig. 11b), the upper part must lose a greater amount of liquid than the lower part requires (i.e., the lower part will gain more continuous-phase liquid than it can hold). As a result, the excess separates out and the column length decreases. The final profile is now given by
