Critical behaviour of ionic fluids

Abstract The past 25 years have seen detailed experimental confirmation, in many fluids, of concepts from the theory of critical phenomena. It has been demonstrated that fluids belong to the universality class of the 3D Ising model, with critical exponents as given by renormalization group calculations. Nevertheless, there is an important class of fluid systems, those with ionic components, for which it is not clear that the notions of critical behaviour developed for uncharged systems apply. We will review the available experimental evidence, and assess the state of theoretical knowledge.