Ds

At the earliest stage of an intrinsic dissolution study, C << Cs, so:

It can therefore be concluded that if the surface area of the dissolving solid is kept constant, the intrinsic dissolution rate will be directly proportional to the equilibrium solubility.

Levich (1962) deduced a mathematic equation for the intrinsic dissolution rate:

where v is the kinematic viscosity of the dissolution medium, m is the angular velocity of the disk in radian per second. Using this equation, one can calculate the diffusion coefficient of a dissolving solute.

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