Abstract
A simple diffusion apparatus has been described in which a layer of solution is allowed to diffuse upward into a layer of solvent. Accurate sampling is performed at various heights and the concentration of the samples is determined. The method has been illustrated with a determination of the diffusion constant of crystalline catalase, which was found to be 3.1 x 10(-7) cm.(2)/sec. at 4 degrees C. The method should be especially suited to the study of biological substances endowed with specific activity and which cannot be obtained in pure solution.