Subcritical water (SubCW) is a term commonly used for water
heated under pressure from its atmospheric boiling temperature
(100 C) to its supercritical point (374 C). At these conditions the
thermal motion of water molecules increases, markedly changing
its properties. Unlike ambient water, the highly hydrogen-bonded
structure at subcritical conditions slowly starts to dissipate, resulting
in a decrease of permittivity (polarity), increase of diffusion
rate and a decrease in viscosity and surface tension (Smith, 2002).