Phase separation during freezing upon warming of aqueous solutions.
Using differential scanning calorimetry, we show that the addition of solute(s) to emulsified water lowers the freezing temperature to <231 K, the homogeneous nucleation temperature of pure bulk water, or even completely suppresses freezing. In the latter case, freezing upon warming occurs above T(X) ≈ 150 K and leads to a phase separation into pure ice and a freeze-concentrated solution (FCS) which crystallizes upon further warming. We also show that emulsified 20-21.5 wt. % HCl solutions and the FCS of HCl/H2O solutions transform to glass at T(g) ≈ 127-128 K, i.e., lower than T(g) ≈ 136 K of water. We suggest that water nanodrops adsorbed on fumed silica resemble bulk water more than water confined in nanoscaled confinement and also more than nanoscaled water domains in aqueous solution.
Institute of Physical Chemistry, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria.
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Bogdan
Institute of Physical Chemistry, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria.
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Loerting