Problem 2.162

A vessel filled with air under pressure $p_{0}$ contains a soap bubble of diameter $d$ . The air pressure having been reduced isothermally $n$ -fold, the bubble diameter increased $\eta$ -fold. Find the surface tension of the soap water solution.

\alpha=1 / 8 p_{0} d\left(1-\eta^{3} / n\right) /\left(\eta^{2}-1\right)

Liquids. Capillary effects