TITLE:
Gibbs Density Surface of Water and Steam: 2nd Debate on the Absence of Van Der Waals’ “Critical Point”
AUTHORS:
Leslie V. Woodcock
KEYWORDS:
Water, Steam, Phase Diagram, Critical Line, Percolation Loci
JOURNAL NAME:
Natural Science,
Vol.6 No.6,
April
16,
2014
ABSTRACT: A revised phase diagram for
water shows three distinct fluid phases. There is no continuity of liquid and
gas, and no “critical point” on Gibbs’ density surface as hypothesized by van
der Waals. A supercritical colloidal mesophase bounded by percolation
transition loci separates supercritical liquid water and gas-phase steam. The
water phase is bounded by a percolation transition (PA) of available volume,
whereas steam is bounded by the loci of a percolation transition (PB) at a density
whereupon a bonded molecular cluster suddenly percolates large distances. At
the respective percolation densities, there is no barrier to nucleation of
water to steam (PA) or steam to water (PB). Below the critical temperature, the
percolation loci become the metastable spinodals in the two-phase coexistence
region. A critical divide is defined by the interception of PA and PB the p-T
plane. Critical parameters are obtainable from slopes and intercepts of
pressure-density supercritical isotherms within the mesophase. The
supercritical mesophase is a fourth equilibrium state besides ice, water and
steam. A thermodynamic state function rigidity (dp/dρ)T defines a distinction between liquid and gas, and
shows a remarkable symmetry due to an equivalence in number density
fluctuations, arising from available volume and molecular clusters, in liquid
and gas respectively. Following an earlier debate in these pages [“Fluid phases of argon: A debate on the
absence of van der Waals’ critical point” Natural Science 5 (2)
194-206 (2013)], we here report further debate on a science of criticality
applied to water and steam (APPENDIX 1).