A novel technique to semi-quantitatively study the stability of emulsions and the kinetics of the coalescence under different dynamic conditions

The kinetics of coalescence is studied experimentally using a new technique for tracking the process in the bulk phase. For this aim, aqueous solutions of KSCN (colorless) and FeCl3 (light yellow) are used to make individual W/O emulsions. Any coalescence occurred between drops containing KSCN solution and those containing FeCl3 solution would combine these solutions. This leads to a reddish brown solution due to the formation of iron(III)thiocyanate. The intensity change of this red color with time represents the dynamics of coalescence occurring between drops of different emulsified aqueous droplets. The detector response to any changes in the system is recorded as a function of time. In this study, the effects of different parameters such as the concentration of Span 80 used as emulsifier in individual emulsions, the mixing rate of the emulsion, and the kinetics of coalescence are investigated semi-quantitatively.