The Concentration of Reactants in Each Phase is Affected by Diffusion

1 The Concentration of Reactants in Each Phase is Affected by Diffusion 

In a homogeneous system, the rate of diffusion (J) across any given distance (x) is proportional to the concentration gradient of the reagent (d[A]/dx) and 

For diffusion in a biphasic system, there is the additional complication of the phase boundary. Therefore, diffusion in each phase will be described by Equation 2.11, but in the region of the phase boundary different rules apply to take into account the mass transfer of the reactant from one phase to the other. Where the solubility of the solute is the same in both phases, the rate of diffusion across the phase boundary J for a solute moving from the higher concentration [A]i to the lower concentration [A]2 through a film of thickness l is given by Equation 2.12, which also describes an exponential decrease in concentration, but 

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