Journal of Physical Chemistry, Vol.99, No.14, 5161-5165, 1995
Glass-)Liquid Transition and Devitrification of LiCl-Center-Dot-11H(2)O Solution and of Hyperquenched and Vapor-Deposited Water
Because of Angell’s (J. Phys. Chem. 1993, 97, 6339) report of remarkably enhanced kinetic stability of amorphous water on heating above its glass transition temperature in comparison with that of 8.33 mol % LiCl solution and of the conclusions drawn, we have reinvestigated the thermal behavior of glassy 8.33 mol % aqueous LiCl solution and compare it with those of hyperquenched glassy water (HGW) and vapor-deposited amorphous solid water(ASW). For a heating rate of 30 K min(-1), the thermal effects observed for 8.33 mol % LiCl solution (for HGW) give 138 K (136 K) for the onset temperature of glass --> liquid transition and approximate to 140.5 K (approximate to 142 K) for the midpoint temperature, approximate to 5 deg (approximate to 12 deg) for the width, 0.97 (0.089) J K-1 g(-1) for the increase in the heat capacity, and approximate to 149 K for the beginning of crystallization for both. The temperature span from the onset of glass --> liquid transition to the beginning of crystallization is approximate to 11 deg (approximate to 13 deg) for 8.33 mol % LiCl solution (for HGW), but from the midpoint temperature it is approximate to 8.5 deg (approximate to 7 deg). A comparison between the temperature spans from the midpoint temperature is more appropriate because of the large differences in widths of the glass --> liquid transition. These analyses show that HGW on heating above its glass --> liquid transition is less stable toward crystallization than 8.33 mol % aqueous LiCl solution, and it removes the claimed evidence for HGW being a "strong" liquid, or a new phase. Any meaningful deduction on the characteristics and structure of ASW must include also the spurious effects of gas inclusion on its thermal behavior.
Keywords:AMORPHOUS SOLID WATER;DILUTE AQUEOUS-SOLUTIONS;DIFFERENTIAL SCANNING CALORIMETRY;UNEXPECTEDLY STABLE NITROGEN;ASTROPHYSICAL IMPLICATIONS;CUBIC ICE;OXYGEN;CRYSTALLIZATION;ADSORPTION;SURFACES