This Volume, the last of the series, is devoted to water in its
metastable forms, especially at sub-zero temperatures. The past few
years have wit- nessed an increasing interest in supercooled water and
amorphous ice. If the properties of liquid water in the normal
temperature range are already eccentric, then they become exceedingly so
below the normal freezing point, in the metastable temperature range.
Water can be supercooled to -39°C without too much effort, and most of
its physical properties show a re- markable temperature dependence under
these conditions. Although ade- quate explanations are still lacking,
the time has come to review available knowledge. The study of amorphous
ice, that is, the solid formed when water vapor is condensed on a very
cold surface, is of longer standing. It has achieved renewed interest
because it may serve as a model for the liquid state. There is currently
a debate whether or not a close structural relation- ship exists between
amorphous ice and supercooled water. The nucleation and growth of ice in
supercooled water and aqueous solutions is also still one of those grey
areas of research, although these topics have received considerable
attention from chemists and physicists over the past two decades. Even
now, the relationships between degree of supercooling, nucleation
kinetics, crystal growth kinetics, cooling rate and solute concentration
are somewhat obscure. Nevertheless, at the empirical level much progress
has been made, because these topics are of considerable importance to
biologists, technologists, atmospheric physicists and gla- ciologists.
