Various methods of emulsions to test the type of emulsion are as follows:
a) Microscopic methods:
To a small amount of the given emulsion, a few drops of water are added. The water will mix completely if the emulsion is oil-in-water type. Similarly for the water-in-oil emulsions, the miscibility with a few drops of oil can be tested. The miscibility can be seen under a microscope.
b) Conductive method:
This method is based upon adding a small amount of an electrolyte to the emulsion. Of the conductance increases, the emulsion is oil-water type and if there is no significant change; it is water-in-oil type.
c) Dye method:
A small amount of an oil soluble dye is added to the emulsion. If it is water-in-oil type, it becomes deeply colored, otherwise it remains colorless.
Properties of emulsions:
1) Emulsions exhibit all the properties like Tyndall effect, Brownian movement, Electrophoresis, Coagulation on addition of electrolytes.
2) The size of the dispersed particles in emulsion is larger than those in the sols. It ranges from 1000 Å to 10,000 Å.
3) Emulsions can be broken to yield the constituent liquids by heating, centrifuging by adding larger amounts of the electrolytes to precipitate out the dispersed phase or by chemical destruction of the emulsifying agent. The separation of cream from milk is a well known example of centrifuging.