Forces Leading to Gel Formation

Several types of interaction may lead to gel formation. These may be electrostatic, van der Waals interactions, or chemical bonding. 

In the case of charge-stabilised dispersions above a certain concentration, addition of electrolyte often leads to gelation rather than the formation of distinct floes. Thus gelation may be regarded as the formation of an extended, continuous floe filling 

Processes in which by various procedures a sol is converted into a gel are sol-gel processes and have found important industrial applications (see Chapter 14). 

Many gels can be dried, leaving a porous solid that has a network structure. These are called xerogels. Silica gel is a typical example. 

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