Interbubble Gas Diffusion and the Stability of Foams

✍ Scribed by François G. Gandolfo; Henri L. Rosano

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 160 KB
• Volume: 194
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.5067

✦ Synopsis

the surface tensions of the two bubbles are equal. Thus the Foam decay may arise from liquid drainage, whether gravitalarger bubble will grow at the expense of the smaller one, tional, due to interbubble gas diffusion, or from rupture of the and the smaller bubble will eventually disappear. The conseinterbubble liquid lamellae. In our study of factors affecting foam quence is a coarsening of the foam, leading eventually to its stability, we focus on interbubble gas diffusion, which works collapse.

against stability even given a stable lamella. We show that liquid Lemlich (1, 2) presented a theory for the change in the drainage from the foam due to such diffusion (as distinct from distribution of bubble sizes that results from the diffusion that due to gravitation) can often be greatly reduced by adding a of gas between bubbles of liquid foam. The theory begins water-insoluble vapor to the foam-generating gas: the presence of such a vapor counterbalances the Ostwald ripening, thus stabiliz-with the application of the classical Law of Laplace and ing the system. ᭧ 1997 Academic Press Young to the pressure difference between a bubble and its Key Words: foam stability; disproportionation; liquid drainage. surrounding liquid and involves a concept of gas transfer to and from an effective fictitious intermediate bubble. Lemlich et al. ignored any contribution to the processes kas (6) used field flow fractionation to study Ostwald ripen-1 To whom correspondence should be addressed. ing in fluorocarbon emulsions containing two dispersed 31