In the next example, the particles are larger than those in true solutions are, but smaller than those in coarse suspensions. This gives these mixtures properties of both categories. Colloids are mixtures in which the particle size is usually between 10 angstroms and 1000 angstroms . These suspended particles do not settle at 1 G, but can be forced to settle under accelerated G forces, as in centrifugation. These mixtures are not optically empty as solutions are, and many times have a foggy or milky appearance.
Fog is a classic example as it consists of very small water droplets dispersed in air.
Mayonnaise and human blood are also good examples of colloids. Colloids, like solutions, are dispersions of particles of one substance throughout another substance. Unlike solutions, the particles are large enough to scatter light. This scattering of light by colloidal - sized particles is known as the Tyndall Effect . We have all seen this effect although we might not have recognized it for what it was.