subject: MAss transfer in fluid system. In $1765,$ Benjamin Franklin made a variety of experiments on the spreading of oils on

the pond in Clapham Common, London. Franklin estimated the thickness of the oil

layers to be about $25.$ Many more recent scientists have tried to use similar layers of

fatty acids and alcohols to retard evaporation from ponds and reservoirs in arid

regions. The monolayers used today usually are characterized by a resistance around

$2s\frac{ec}{cm}.$ Assuming that they are the thickness of Franklin's layer and that they can

dissolve up to $1\mathrm{.}8\%$ water, estimate the diffusion coefficient across the monolayers.

Answer: $7*{10}^{-6}c\frac{m^2}{sec}.$