This technique was introduced by Mc Bain in 1937. It is the dissolution of poorly soluble solute molecules in water in presence of surfactants and forms thermodynamically stable solution.
The process of dissolution in presence of surfactants have been described as the formation of micelles (colloidal aggregate of surfactant), which enhances the solubility of poorly soluble solute, when surfactant of proper HLB is added in low concentration to liquid, it tends to orient at air-liquid interface. surfactant is continued to be added in higher concentrations, air-liquid interface is fully occupied . At still higher concentrations, the surfactant molecules or ions are forced to go into the bulk of the liquid, when the particular concentration of surfactant molecule is maintained in the system, aggregates of surfactants are formed called micelles.
The concentration of surfactant at which micelles formation takes place is called critical micelle concentration (CMC). Micelles may be of various shapes like; spherical, sausage, rod or lamellar. Micelle formation increases the solubility of a solute by virtue of its dissolving in or being absorbed onto the micelle. This function of surfactant starts only at CMC and increases with the concentration of the micelles.
Solubility enhancement of cresol solution with soap solution is a very good example of this technique. As such cresol has only 2% v /v solubility in water but with soap solution we can dissolve up to 50% v /v cresol in water (Lysol solution). The technique is useful to solubilize many water insoluble vitamins like A, D and K; and to prepare solutions of chloroxylenol and Hexachlorophene.
it is a complex phenomenon where surfactants are used for the removal of foreign matter from the solid surface. It may be a removal of dirt from the clothes or removal of dirt from the body surfaces. This process needs surfactants which act according to their characteristics and removal of the foreign matter from the surfaces takes place. The various characteristics of surfactants like; solubillizing, emulsifying, and wetting are utilized in the process of detergency.
The surfactants must have the characteristics to remove the dirt intact with the surfaces, into the bulk of the liquid. This can be achieved by reducing the interfacial tensions between dirt/water and solid/water and thus the force of adhesion (adhesive forces) between the dirt and the solid is reduced and the dirt particles may easily be detached. Unce the particles are detached from the sold surface, immediately surfactants are adsorbed at the particle surface, turning them in to charged particles that prevent their further deposition. In case the foreign matter is oil or fat, it may be removed either by getting emulsified or solubilized.