Theory
Emulsion: Emulsion is a colloidal system consisting of immiscible liquids. e.g. milk is an emulsion in which particles of liquid fat are dispersed in water. It is a heterogeneous system consisting of more than one immiscible liquids dispersed in one another inform of droplets whose diameter, in general, exceeds 0.1 μm. Such systems possess an extremely small stability which is made by the addition of surface active agents, finely divided solids, etc.
Type of Emulsions :
(i) Oil in water (o/w) type : In these emulsions oil forms the dispersed phase and water, the dispersion medium. For example, milk, vanishing cream, etc. These are also called aqueous emulsions.
(ii) Water in oil (w/o) type : In these emulsions water is in the dispersed phase and oil in the dispersion medium. For example, butter, cold cream etc. are also called oil emulsions.
Emulsifiers: In order to prepare stable emulsions, it is important to add a third component known as emulsifier or emulsifying agent in suitable amounts.
Micelles: The diphilic nature of surfactant molecules, i.e. the presence in them of a polar (hydrophillic) and non-polar (hydrophobic) parts has been a feature of their structure imparting special properties to these molecules. Micelles may be defined to be aggregates of long- chain diphilic surfactant molecules or ions formed spontaneously in their solutions at a definite concentration.
Micelles form by the cooperative binding of monomers to one another at concentrations exceeding a rather narrow region called the critical micellization concentration (CMC). The latter is the concentration of a surfactant at which a large number of micelles form in its solution that have been in thermodynamic equilibrium with the molecules (ions), and a number of properties of the solution sharply change.
