Theoretical isotropic dissolution of nonspherical particles.

Equations are derived for the isotropic dissolution of single particles, considering simple forms of the six crystal systems. These can be summarized by three basic equations which are approximated well, and in some cases exactly, by the dissolution equation for a hypothetical spherical particle of specified diameter. Formulas are given to enable calculation of this diameter and to minimize the weighted errors in the approximations. Spherical approximations provide a simple basis for calculating the dissolution profile of real multiparticulate systems which are difficult to describe otherwise. Spherical approximations based on equal surface area or volume result in large errors.