A criterion for selecting leach test specimen sizes

When leaching is controlled by a diffusion process, leach test results are particularly simple to interpret when test specimens approximate semi-infinite media. For spherical and cylindrical leach test samples, a criterion relating the test duration T, the specimen radius R, and the effective bulk diffusion coefficient D, to the desired degree of concurrence to the semi-infinite geometry behavior P, is shown to be given by: 1 - P = ùDT/R. From the proposed criterion, it is concluded that, for glass waste forms, the semi-infinite geometry approximation is met by most test samples except possibly for finely crushed material