Influence of dielectric constant on sedimentation rate of concentrated suspensions of aluminum and magnesium hydroxides.

Sedimentation of dilute pharmaceutical suspensions obeys Stokes's law, which assumes that there is no interaction between particles. The behavior of concentrated pharmaceutical suspensions is generally interpreted by use of modifications of Stokes's law that do not consider chemical interaction between particles. Properties of the medium itself, such as dielectric constant and surface tension, have not been included in the established equations. The present work shows that the dielectric constant of the medium has a distinct effect on the rate of sedimentation of the systems investigated.