
71Mechanisms of Foam Instability
at40%, the foam grew as gas was sparged to it until an equilibrium height
of somewhat less than 20 cm was established. However, when the same
experiment was repeated while maintaining the relative humidity at the
top of the column at 96%, the foam kept growing until it reached the top
of the column. Further, Shaw etal. (2010) demonstrated that the liquid
overow rate into a launder, such as that found in some foam fractionation
device designs, is dependent on the environmental humidity at the free
surface.
Li etal. (2012) have speculated, with some preliminary supporting exper-
imental data, that the cause of ...