Experimental evidences:

Addition of a modifier helps to overcome third phase and emulsion formation tendencies in a solvent system. As is with diluents and extractants, the modifier should be very soluble in the organic phase, insoluble in the aqueous phase, be readily available and cheap. Usually, the amount of a modifier used is 2-5 volume percent. In some cases, where the extractant concentration is high, the requirement may be as high as 20% or more.

Experimental evidences suggest that a modifier like a diluent cannot be selected arbitrarily. The selection for a particular system is to be made on the basis of experimental data. The amount of a modifier required is also to be determined experimentally. One point which should be borne in mind is that the effect of a modifier and a diluent in the extraction stage differs greatly from their effects in scrubbing and stripping stages, both on mass transfer and kinetics, and also on phase disengagement and solvent entertainment.