How can the two emulsions can be distinguished :
(a) oil in water type (O/W) and
(b) water in oil type (W/O)
In oil in water emulsion (O/W), the dispersion medium is water and oil is the dispersed phase.
In water in oil emulsion (W/O), the dispersion medium is oil and water is the dispersed phase.
Two emulsions could be distinguished by some test:
- Dilution Test
- Conductivity Test
- Dye solubility Test
- Cobalt Chloride Test
- Fluorescence Test
Dilution test: In dilution test, oil (or) water is used for the dilution of emulsion.
When the emulsion is O/W type, water is used for dilution for this emulsion, it would remain stable because dispersion medium is water. Whereas if oil is used for dilution, the emulsion would break because water and oil are immiscible with each other.
Aqueous solvent is used for dilution for oil in water emulsion whereas oily liquid is used for dilution of water in oil emulsion.
Conductivity test: An example of good conductor of electricity is water where is oil is poor conductor of electricity. A pair of electrodes are linked to bulb and pair of electrodes are dipped in emulsion. The bulb glows if the emulsion is oil in water type and if the emulsion is water in oil type, no glowing of bulb happens.
Cobalt chloride test: A solution of cobalt chloride is used for distinguishing the two emulsions. A filter paper is soaked in solution of cobalt chloride and later dipped into emulsion, when there is a change in color from blue to pink, the emulsion is identified as oil in water emulsion.
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