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What is an emulsion?

 Emulsion

Instead of a long definition, let's get to know this term in small divided forms.

  • Emulsion is a thermodynamically unstable system.
  • It consists of two immiscible liquids (one is generally water and another is oil)
  •  It consists of one phase dispersed into another in the form of globules/ droplets.
  • Either oil is dispersed in water (o/w) or water is dispersed into oil (w/o)
  • This system is stabilized by adding suitable emulsifying agent(s).
  • The liquid which is dispersed in the form of small globules is known as dispersed phase.
  • The liquid in which globules are dispersed is known as continuous phase.
  • For example- if paraffin oil is dispersed in the form of globules into water, paraffin oil is a dispersed phase and water is a continuous phase. This system is o/w i.e. oil in water emulsion.

The dispersed phase is also known as discontinuous phase or internal phase.

The continuous phase is also known as dispersion media or external phase.

1. While formulating an emulsion, a ratio of dispersed phase to the total volume of emulsion is determined. This ratio is known as phase volume ratio.

2. Emulsions intended for oral/internal administration are liquid emulsions.

3. Emulsions intended for external applications are referred as creams, lotions and liniments.

4. Globule size (diameter) in emulsions-
  • Coarse emulsions : 0.1 to 100 micrometers
  • Micro emulsions : less than 0.1 micrometer
  • Nano emulsions : less than 100 nanometers 
5. Internal phase/globule size of micro and nano emulsions is much smaller that it doesn't refract light and are transparent. (This transparency phenomenon depend of concentration of internal phase and dispersion of globules per unit volume).


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