A series of experiments was run to test the feasibility of determining diffusion rates in a porous medium using a nonsteady state method. The experimental procedure is based on a mathematical model of Crank (1970) and involves diffusion from a porous sheet of finite thickness into a finite homogeneous volume. By measuring the composition of the homogeneous volume as a function of time it is possible to calculate integral diffusion coefficients of salts in the porous medium.