Dispersion
A dispersion consists of at least two physical materials, in which one is discrete (or disconnected from itself) and the other continuous, with the external surface of the discrete phase connecting to the continuous at all points.
If the discrete phases consists of particles between 1 and 1000 nanometers, then the dispersion is colloidal.
Colloidal dispersions are of major significance in many fields, including the food, pharmaceutical and cosmetic sciences.
Types
Binary dispersions consist of combinations of liquid ($L$), solid ($S$) and gas ($G$).
This gives $3^2 = 9$ possible combinations:
| $L$ | $S$ | $G$ | |
|---|---|---|---|
| L | $L_1/L_2$ | $L/S$ | $L/G$ |
| S | $S/L$ | $S_1/S_2$ | $S/G$ |
| G | $G/L$ | $G/S$ | $G_1/G_2$ |
The / expresses the relation is dispersed in. So $x/y$ means x is dispersed in y.
Examples
Emulsion
A liquid dispersed in another liquid.
Whole milk is an emulsion, as it consists of oil droplets dispersed in water.
Solid foam
A gas dispersed in a solid matrix.
Bread is a solid foam, as it consists of air dispersed in baked dough.
Liquid suspension
A solid dispersed in a liquid.
Orange juice “with bits” is a liquid suspension… you get the idea.