Mixtures of gases, 2pm Thursday

Discussion of single gas behaviour rules which are established and agreed. Single bubble 
d shrinks and in dry foam average bubble d increases. All Laplace pressure driven? Soap 
film bubble of gas mixture is only Laplace driven.

Critical size of bubbles dependent on dissolved gases in surrounding liquids. For gas 
mixtures, either side of side bubble either grows or shrinks. What is the role of entropy 
of mixing of gases? Is the role of this significant in comparison to partial pressures?

Webster & Cates, Langmuir 1998: compares the difference of pressure and chemical 
potential balances inside bubble and in the liquid.

Empiricism is relied on for real cases away from dilute perfect sphere case.  Simulations 
suggest only a small amount of insoluble gas is needed to stabilise foams, but in 
practice much more is used. How much gas do you need to equalise partial pressures (if 
all that is required). 

How to use coarsening? - eg for bread doughs to eliminate bubbles in preparing dough for 
proofing, also to lead to more unstable foam which collapses more quickly. Could 
coarsening be used to engineer surface history?

How does foam topology change over coarsening time for mixed systems containing insoluble 
gas? Interesting area is that of very low concentrations.