This Demonstration considers the mass transfer of a substance A between two immiscible solvents I and II. The concentration in both phases is plotted versus position for various values of the diffusion coefficients (in , and , time (in seconds), and Henry law constant (a dimensionless constant). When the concentration of A is continuous at the interface, which is not typical. The concentration profiles are solutions of the following diffusion equations and boundary conditions:

,

,

for ,

for , ,

at ,

at ,

at .

Using Laplace transforms, one can easily derive analytical expressions of the concentrations in phases I and II: