Identification test for emulsion

Identification test for emulsion: The Following tests are used to distinguish between o/w and who emulsions.

1. Dilusion Test

The emulsion is diluted with water. In case the emulsion remains stable after its dilution it is o/w emulsion. The w/o emulsion breakdown on the addition of water, but is stable on the addition of oil.

2. Dye Test

  • The Scarlet red dye is mixed with the emulsion.
  • Place a drop of the emulsion on a microscopic slide. cover it with a cover slip and examine it under a microscope.
  • If the disperse globules appear red and the “ground” colorless the emulsion is o/w type.
  • The reverse condition occurs in w/o type emulsion i.e. the dispersed globules appear, colorless in the red ground.

3. Conductivity Test

  • Water a good conductor of electricity, whereas oil is a non-conductor of electricity.
  • It can be performed by dipping a pair of electrodes, connected through a low-voltage bulb in the emulsion.
  • If the bulb glows on passing the electric current.
  • The emulsion is o/w type because the water is in the continuous phase.
  • In case of the bulb does not glow, the emulsion is w/o type because oil is in the continuous phase.

4. Fluorescence Test

  • Certain fixed oils possess the physical properties of fluorescing in the presence of ultraviolet radiation. On microscopic observation of emulsion under u.v. radiation the fluorescence indicates.
  • Oil is present in the continuous phase [w/o type emulsions] and droplet fluorescence indicates that oil is present in the dispense phase [o/w type emulsion].

Also, read: Classification of Emulsifying agents

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