The precrystallization state of aqueous salt solutions

The parameters characterizing the fluctuations in the concentration have been calculated for a great number of aqueous solutions of various salts both in the range of the cluster formation and in the critical range. The existence of an inflection point on the isotherms of concentration susceptibility preceding the transition of the solution to the supersaturated state has been established. It is found that (1) the inflection point indicates the complete hydration of the solution and the beginning of the active cluster formation in solution and (2) that, in fact, the cluster formation in the solution is a diffuse second-order phase transition. It is concluded that the clusters have the liquid-like structure and the diffuse boundaries. At a deviation of the solution concentration from its critical value, the critical index equals unity, in full accordance with the Landau theory of the mean field.