A dielectric fallacy in inferring Tg of water.
In a recent analysis, Angell [Annu. Rev. Phys. Chem. 55, 559 (2004)] concluded that if water's Tg is assumed to be 160 K, the plot of dielectric loss tangent tan delta against T/Tg for unsintered amorphous solid water overlaps the corresponding plots for glycerol and propylene carbonate. We point out that such an analysis falsifies both dielectrics and molecular kinetics, and is not useful for ascertaining Tg.
Johari
G P
GP
Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada. joharig@mcmaster.ca