Foam - the disperse systems consisting of gas bubbles, separated liquid or solid (solid foam) films. Foam arise from liquids when they are stirring, shaking, blowing gases or formation of these gases in chemical reactions or boiling). Solid P. formed from liquid when their films are polymerized. The ability to have foaming suspensions and solutions only certain substances called foam. Film of liquid P. consist of two monomolecular layers from the molecules of foaming agent), between them is a solution layer, the thickness of which in the beginning of the same order as that of the colloidal particles (see Colloids), and then continuously decreased (due to leakage). Foaming agents are surface-active substances, able to create a film that has a sufficiently high structural-mechanical properties. Foam is used to remove particles of dirt, in the manufacture of some products in the food and pharmaceutical industries, to fight fires, in flotation (mineral processing), solid foam - in construction (foam glass, foam concrete) and for other purposes. By foaming can enrich the solutions and share proteins and other biologically important substances. To avoid P., you should avoid vigorous stirring, boiling, contact with porous materials. Foam can be destroyed by the introduction of special substances - antispyware, as well as by mechanical or thermal impact on them.
Cm. also Dispersed systems.