13
Changes in Dispersity
In Section 9.1 it is stated that all lyophobic dispersions are thermodyna-
mically unstable. They tend to change in such a way that the interfacial free
energy will be minimized, causing an increase in particle size. Moreover,
some lyophilic dispersions can become unstable if conditions like pH, ionic
strength, or solvent quality change. In Chapter 12, the interaction forces
involved are discussed, and additional basic information is given in Chapter
- The instability can lead to a variety of changes, which are the subject of
this chapter. The rate at which they will occur and the factors affecting them
will be discussed. The particle size distribution, discussed in Section 9.3, is
often an important variable.
The changes can also be caused or affected by external forces,
especially gravitational and hydrodynamic forces. The latter are briefly
discussed in Section 5.1.
13.1 OVERVIEW
Figure 13.1 gives an overview of the various types of change in the state of
dispersity. We will briefly discuss them here.