Experimentally proven liquid-liquid critical point of dilute glycerol-water solution at 150 K.

The experimental and theoretical studies of supercooled liquid water strongly suggest that the two liquid waters and their liquid-liquid critical point (LLCP) exist at low temperature. However, the decisive experimental evidence of the LLCP has not been obtained because of the rapid crystallization of liquid water in the "no-man's land." Here, we observed experimentally the pressure-induced polyamorphic transition in the dilute glycerol-water solution which relates to the water polyamorphism. We examined the effect of the glycerol concentration on the liquid-liquid transition, and found its LLCP around 0.12-0.15 mole fraction, 0.03-0.05 GPa, and ~150 K. A 150 K was above, or around, the recently recognized glass transition temperatures of amorphous ices, and the crystallization did not occur, indicating that the direct observation of LLCP is feasible. The low-temperature LLCP has implication to the argument of the relation between the interaction potential of water molecule and the polyamorphic phase diagram.