Colloid
Colloid, suspension of tiny particles of one substance, called the dispersed phase, in another phase, called the dispersion medium. The particles are so small that they remain in suspension indefinitely, unaffected by gravity. Both the suspended, or dispersed, phase and the dispersion medium may be solid, liquid, or gaseous, although the dispersal of one gas in another is not known as colloidal dispersion. An aerosol is a colloidal dispersion of either a solid colloid (such as cigarette smoke) or a liquid (such as insecticide spray) in a gas, the air. An emulsion is a colloidal dispersion of liquid particles in another liquid; mayonnaise, for example, is a suspension of tiny globules of oil in water. A sol is a colloidal suspension of solid particles in a liquid; paints, for example, are a suspension of minute solid pigment particles in an oily vehicle. A gel is a sol in which the suspended particles are organized in a loose, but definite three-dimensional arrangement, giving some rigi...