**6. Conclusion**

Mass transfers occurring within different kinds of emulsions, simple, mixed and multiple, have been described in this chapter. Almost of the examples given are dealing with mass transfer occurring at ambient temperature between phases of different composition. Focus has been made about the results obtained by submitting time to time an emulsion sample to a cooling and heating cycle during which freezing and melting of the phases concerned by the mass transfer are registered through the energies involved in the liquid – solid transition thanks to a differential scanning calorimeter. The amount of the transferred mass is deduced either from the freezing or melting of the pure material droplets A or from the calibration curve that gives the freezing temperature of the droplets made of A+B, versus the composition. This DSC technique appears to be suitable to study this kind of phenomenon as far it permits to follow the transfer and furthermore to get the kinetic of the transfer. Doing so a model of the transfer can be set up and the mechanisms involved can be described. It appears that the mechanism to be considered is a solution – diffusion transfer facilated by micelles that entrapped the compound to be transferred. Therefore a control release can be set up through the formulation of the emulsion. Another type of mass transfer has been described that induces solid ripening as the result of the mass transfer. The case of hydrate formation has been given as an example. The mass transfer due to the diffusion of a material in the oil phase of a W/O emulsion, induces the formation of a solid compound, namely an hydrate, when this compound chemically reacts with water of the dispersed water. Here as well, the DSC technique appears to be suitable but due to overlapping of transitions dealing with water and hydrate a complementary technique is needed. That shows the limit of the DSC technique that needs net liquid-solid transitions and a reduced overlapping of the transitions. To conclude these studies show the great advantage to use emulsions for having mass transfer in a rather short time due to the total high surface area of exchange and the presence of micelles. Therefore, these systems can be considered to set up separation processes, the emulsions being seen as liquid membranes systems or as mini reactors for getting chemical reactions between compounds. Nevertheless a control of the formulation of the emulsions in order to get kinetically stable emulsions at least during the process involved is needed.
