Abstract: The maximum solubilization of water (S_max) at various total amounts of alcohol(V_n) in P507(K)/alcohol (n-propanol,isopropanol,n-butanol,2-butanol,n-pentanol,2-pentanol,n-hexanol,3-hexanol,sec-octyl alcohol)/n-heptane/water microemulsions was investigated.Different trends of the change of S_max against Va were found.In the n-pentanol,2-hutanol,2-pentanol,3-hexanol and sec-octyl alcohol containing systems, S_max firstly increases and then becomes very low rapidly.This phenomenon was interpreted in terms of the formation of molecular solutions.It was also found that S_max firstly increases with V_a and then remains unchanged in the n-propanol-containing system, while S_max increases rapidly at first and then increases gradually in the isopropanol-containing system.It was suggested that R_w, radius of water pool, is unchanged when S_max remains the same value in the former syxtem.In the latter system,R_w was also supposed to be unchnged when S_max begins to increase gradually,however,the detergentless microemulsion forms at the same time.In the n-hexanol-containing system,there exists a peak in the S_max vs.V_a curve.It shows that there is a maximum value of I,molar ratio of alcohol to surfactant on the interface,in the system.

Key words: Microemulsion, Potassium 2-ethyl hexyl₂-ethyl hexyl phosphonic acid, Maximum solubilization of water