Hydrocarbon/fluorocarbon mixed micelle diagram from surface tensiometry

The demixing diagram of the 6 Phi C12/NF system has been determined by surface tensiometry. It is possible to fit approximately both the first cmc from the regular solution theory with a pair interaction coefficient equal to 2.2 and the second cme from a mass balance of the surfactants between the solution and the mixed micelles. But the regular solution theory accounts neither for the coordinates of the ''eutectic'' point on the first cmc curve nor for the compositions in the demixing zone.