文档介绍：1 Disperse Systems, Colloidal Systems
and their Classification
Feature of Dispersions
We use the words, disperse systems and colloidal systems, without giving a clear
distiction between them. Depending on the type of emphasis on the properties,
the same system can be called either a disperse or colloidal system. For instance,
if the physical properties of a system are to be specifically discussed, it may be
called a disperse system, but when chemical properties, industrial applications, or
the historical backgrounds are emphasized they may be called colloids. At any
rate, the disperse nature is indispensable also to colloids.
It is well known that an important feature of disperse and colloidal systems
commonly appear to be the large ratio of surface area to volume of the dispersed
or colloidal particles. The large ratio naturally appears for small particles, fibers,
and thin films, as a physical state. In order to plish this state, a chemical
agent called a surfactant may be needed. The large area is usually associated with
large positive surface energy, but a surfactant, if present at the surface, can reduce
the surface energy. In particular, in order to make a disperse system out of two
immiscible liquids, a surfactant is required unless the mixture is violently shaken.
This requirement has promoted research on surfaces in colloid chemistry. It is un