Temperature dependence of the density of an ionic micellar system near the critical point Original Research Article

The density of the system dodecylammonium chloride + water + KCl has been studied as a function of temperature and surfactant composition for two different concentrations of KCl. The data of the critical samples can be described using scaling laws and the 3D Ising value for the critical exponent α. The range of validity of simple scaling for the density is found to be larger than for the order parameter. When combined with previously reported data, the present results confirm the validity of the two-scale factor universality hypothesis in this ionic micellar system. The results obtained for off-critical compositions have been found to be compatible with predictions of the so-called linear model.