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 remarkab ly enhanced kinetic stability of amorphous water on heating above its glass transition temperature in comparison with that of 8.33 mol % LiC l solution and of the conclusions drawn, we have reinvestigated the th ermal 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 th ermal effects observed for 8.33 mol % LiCl solution (for HGW) give 138 K (136 K) for the onset temperature of glass --> liquid transition an d approximate to 140.5 K (approximate to 142 K) for the midpoint tempe rature, 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 appr oximate to 149 K for the beginning of crystallization for both. The te mperature span from the onset of glass --> liquid transition to the be ginning of crystallization is approximate to 11 deg (approximate to 13 deg) for 8.33 mol % LiCl solution (for HGW), but from the midpoint te mperature it is approximate to 8.5 deg (approximate to 7 deg). A compa rison between the temperature spans from the midpoint temperature is m ore appropriate because of the large differences in widths of the glas s --> 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 evi dence for HGW being a ''strong'' liquid, or a new phase. Any meaningfu l deduction on the characteristics and structure of ASW must include a lso the spurious effects of gas inclusion on its thermal behavior.