DETERMINATION OF EMULSION TYPES

There are many methods available for the determination of emulsion type but the most commonly used are:

Drop dilution method.

Dye solubility method.

Fluorescent test.

Electrical conductivity test.

Direction of creaming test.

Filter paper test.

These methods determine whether the emulsion is oil in water (o/w) type or water in oil (w/o) type.

DROP DILUTION METHOD:

This method is based on the principle that emulsion is always miscible with the external phase. If water is added to water in oil w/o type emulsion, it will not be mixed. On the other hand, oil mixes well.

Same is the case with o/w type emulsion. If oil is added to oil in water o/w type emulsion, it will not be mixed. On the other hand, water mixes well.

DYE SOLUBILITY METHOD:

It is based on the solubility of any dye in the external phase. Amaranth, a water soluble dye gives color to oil in water o/w type emulsion, but not to water in oil w/o type emulsion. Same is the case with oil soluble dyes.

FLUORESCENT TEST:

Based on the fluorescence of oils under ultraviolet light, the emulsion is examined under the light in the microscope. If the whole fluid is fluorescent, it is water in oil w/o but in case of oil in water o/w spotty fluorescence will appear.

ELECTRICAL CONDUCTIVITY TEST:

Based on the electrical conductivity of aqueous solutions, the electric current is supplied and electrodes are placed in the emulsion. If the current is passed, it is oil in water o/w and if is not passed, it is water in oil w/o.

DIRECTION OF CREAMING TEST:

Creaming is the sedimentation of the dispersed phase which is either upwards or downwards, upon which this test is based. The density of oil is mostly less than water. Thus if creaming is at the upper side, it is oil in water o/w and if it is downwards, it is water in oil w/o type of emulsion.

FILTER PAPER TEST:

Take a filter paper, put a drop of emulsion on the filter paper. Evaporate it; if there is a spot on the filter paper, the emulsion will be water in oil w/o. On the other hand, if there is no spot, the emulsion will be of oil in water o/w type.