Determination of Diffusion Coefficients

Diffusion equations derived from Fick's law are discussed and applied to experimental data in the literature on the diffusion of oxygen in copper and on reaction rates for chemical reactions in the solid phase. Previous limitations on the applicability of the formulae are removed by the use of a simple graphical method so that the theory can be applied to data to which it was previously inapplicable. It is pointed out that the exact solution to Fick's law obtained is equivalent to the parabolic law in the early stages of the diffusion process. The activation energy for the diffusion of oxygen in copper is found to be 50.5 kcal. per g-atom.