Dissolution kinetics of soluble nondisintegrating disks.

An equation describing the isotropical dissolution of soluble nondisintegrating disks was developed. It was equivalent to the cube root law only if the height and diameter of the disk were equal. The dissolution kinetics of sodium chloride disks were examined, using a beaker equipped with a centrifugal stirrer as the dissolution chamber. The fit of the experimental data to the cube root law had a coefficient of variation of about 4-5%. It was demonstrated statistically that a fit to a square root of mass versus time relation was significantly better. With increasing porosity, the dissolution process proceeded faster than predicted on the basis of the diffusion-convection model. An explanation is proposed by assuming an increased effective dissolution surface.