A popular hypothesis that explains the anomalies of supercooled water is theexistence of a metastable liquid-liquid transition hidden below the line ofhomogeneous nucleation. If this transition exists and if it is terminated by acritical point, the addition of a solute should generate a line ofliquid-liquid critical points emanating from the critical point of puremetastable water. We have analyzed thermodynamic consequences of this scenario.In particular, we consider the behavior of two systems, H2O-NaCl andH2O-glycerol. We find the behavior of the heat capacity in supercooled aqueoussolutions of NaCl, as reported by Archer and Carter, to be consistent with thepresence of the metastable liquid-liquid transition. We suggest aninterpretation of the liquid-liquid transition in aqueous solutions ofglycerol, recently observed by Murata and Tanaka, elucidating the non-conservednature of the order parameter, its coupling with density and concentration, andthe peculiarity of "spinodal decomposition without phase separation". We alsoshow how the shape of the critical line in a solution controls the differencein concentration of the coexisting liquid phases.
展开▼
