ABSTRACT
Sedimentation is the settling of particles under the influence of gravitational or centrifugal forces. The sedimentation characteristics of dispersions are of great interest for practical applications and for theoretical studies and the analytical characterization of dispersion. The sedimentation in both homogeneous systems and line-start systems is measured by incremental methods or cumulative methods. Pipet methods measure concentration changes within the dispersion by withdrawing samples of the dispersion at a specified depth and time. The particle size distribution obtained by the Andreasen pipet was slightly broader than that obtained with the optical microscope. In the fractional decantation method the particle size in a homogeneous suspension is measured by repeated decantations of the supernatant liquid. Gravitational sedimentation is usually too slow for the characterization of dispersion and the particle size distribution. The parallelism between dispersion stability and the sedimentation volume allows one to tailor dispersions of high stability or easy redispersibility, according to the intended application of the dispersion.
