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Unformatted text preview: gel
a) Elastic gels (e.g. jellies, jams, and corn starch puddings)
b) Nonelastic gels (e.g. silicic acid, commonly known as silica gel)
• Partial dehydration of an elastic gel leads to the formation of an elastic
solid from which the original sol can be regenerated by the addition of
water. Dehydration of a nonelastic gel, on the other hand, leads to a glass
or powder, which has little elasticity. • If an elastic gel such as gelatin is placed in water, it swells, water
having been imbibed b y the gel; the proc ess is know n as imbibition. • Nonelastic gels, may take up solvent but they do not swell-the liquid
enters t he pores of the gel but, si nce the walls a re rigi d, the volume of
the gel does not change. • Gel formation occurs in particular with molecules that can exist as
extended chains. As the sol turns into a gel, the chains become
interlocked so that the viscosity i ncrea ses and e ventually a se mi -solid
ma terial is produced. E MULSIONS
An e mulsion consists of droplets of one liquid dispersed in another liquid. Silicone oil in water em...
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