I. Diffusion problems associated with the growth of crystals from dilute solution

Summary Crystals growing from solutions with plane faces must have considerable supersaturation at some parts of the surface. A supersaturation number σ is introduced to give a measure of the maximum supersaturation. For two-dimensional growth in very dilute solutions a general method for evaluating σ is given; it is applied to the growth of regular polygons, to the growth of a step on a surface, and to growth on the edge of a plate. For three-dimensional growth only a rough estimate for the supersaturation occurring with regular polyhedra can be given; it is estimated that the maximum supersaturation on the surface of a cube or regular octahedron is between 0·25 and 0·4 of the concentration difference between the vertices and infinity.