Abstract: Since the end of 70's, the formation of reversed micellar and microemulsion in extracted organic phase has been studied in our laboratory.We have known that the acidic extractants saponified by alkaline solutions or alkali metals have the similar structure and properties to surfactants, and can form reversed micellar or water-in-oil microemulsion in organic phases during the extraction.Herein we report the changes of the physico-chemical properties conductivity, density, index of refraction and viscosity, of a saponified extractant system in different volume fractions of water added with P507 as the extractant, Na and Kas the saponifier, sec-octyl alcohol as the cosurfactant, and n-heptane as the oil.The density and index of refraction as the function of Φ_w are shown in Fig.1.The variations of conductivity and viscosity of organic phase during the adding water to P507K-ROH-heptane system are shown in Fig.2-Fig.6.It can be seen that the density, conductivity and viscosity increase and the index of refraction decreases with the water content in the microemulsion.It can be seen that the results are helpful to understanding the nature of the extraction mechanism and kinetics.

Key words: Extractant, Microemulsion, Physico-chemical property