Preface

The author’s interest in gas diffusion in porous media was triggered by Dr. John Farr when, as an advisee, he questioned how Fick’s first law of diffusion and Graham’s law of diffusion could be reconciled. A significant relevant literature was found to exist in physics, chemical physics and chemical engineering, but few of the findings in these fields have so far widely penetrated the earth sciences. A goal of this book is to improve the awareness on the part of earth scientists and engineers of the depth of knowledge that exists on this subject and to foster a better understanding of one of the fundamental transport processes that operates beneath the Earth’s surface.