Abstract
A method is described for the calculation of the dependence of the diffusion coefficient on the concentration of diffusing material from data obtained by studying the rates of sorption of vapors by films. The principle of the method is to approximate the actual concentration dependence by a step function. For such a function the differential equations involved can be solved analytically, and the heights of the individual steps can be computed; the step function is then smoothed out by an averaging process. The method has been tried out for the sorption of isobutane by polyisobutylene at 35°C and found to be quite satisfactory.