... = density of the disperse phase ?c = density of the continuous phase ? = viscosity of the continuous phase Rate of sedimentation can be decreased by reducing particle size, reducing the density difference or by increasing the viscosity of the dispersed phase. Reducing the size of the suspended particles results in a slower settling rate. One big problem with fine particles, however, is the fact that when they settle, the form a more closely packed sediment, which may be more difficult to re-disperse. The slow rate of settling prevents the entrapment of liquid within the settlement, which thus becomes more compacted. This phenomenon is called caking and is the most serious physical stability problem encountered in suspension formulations. One way to prevent caking is by the addition of flocculating agents such as electrolytes, surfactants, polymeric flocculating agents, e.g. starch, alginates. Flocculating agents work by causing the solid particles to aggregate and ...

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