Interpretation of the Anomalous Critical Behaviour in a Quaternary Microemulsion

The new experiments presented in this paper show that the anomalous critical behaviour previously reported in a quaternary microemulsion is due as a matter of fact to a crossover of two critical phenomena. The temperature evolution of the phase diagram and the light diffusion data agree with this interpretation. The system investigated exhibits a phase separation at low and high temperatures. The high-temperature critical point is a consolute critical point characterized by Ising exponents. The critical behaviour found at low temperature is related to a transition from micellar to flow birefringent phases. This interpretation is in agreement with recent models.