Mathematical description of solute velocities during dissolution from a horizontal surface.

A mathematical analysis of solute flow in a descending column following dissolution is presented. The acceleration of a solute particle from zero velocity, when it is in the solid phase, to its final equilibrium descending velocity was analyzed. The maximum velocity for N-(3-methylphenyl) acetamide developed essentially at the solid-liquid interface, contradicting the postulate of a microsize diffusional layer. The possibility of a diffusional layer existing for solids of lower solubility than N-(3-methylphenyl)acetamide is discussed.