Colloid

A mixture in which fine particles of fats or insoluble solids are dispersed in liquid and remain suspended indefinitely or for at least a long time. There are two types: In one, fat particles are dispersed in liquid (such as a sauce finished with a little butter); in the other, water particles are dispersed in fat (hollandaise). Particles in liquids may also be gasses such as air, carbon dioxide, or nitrous oxide; these colloids are usually called foams. Don’t confuse colloids with solutions, which are stable and never separate. Milk is a colloid, Coca-Cola is a solution. See also Hydrocolloids.