Metallic-nonmetallic phase coexistence above the consolute point of sodium-ammonia solution

The heat capacity under saturated vapors, C, of three different concentrations of NaNH3 solution (X=0.045, 0.046, 0.063 molar part of Na) has been measured in the temperature range 200-300 K. All three C(T) curves show anomalies consistent with the existence of a new two-phase region above the well-known liquid-liquid critical point (Xc=0.0415, Tc=232 K). Its location is compatible with the metal-nonmetal transition line; so it is believed that in equilibrium these are metallic and insulating phases with different concentrations of electrons.