Encyclopedia of Geochemistry

2018 Edition
| Editors: William M. White

Critical Points

  • William H. CaseyEmail author
  • Peter A. Rock
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-39312-4_10

Definition

The point in phase space where the distinction between liquid and vapor disappears.

Elaboration

If you heat water in a closed volume, the temperature and pressure are initially fixed by equilibrium between a liquid and vapor. Beyond a certain temperature and pressure, however, the meniscus that separates the two phases disappears, and they become indistinguishable. If one draws a curve in P-V space that identifies the region where both a liquid and vapor coexist, the critical point lies at the maximum where the slope is zero:
$$ {\left(\frac{\partial P}{\partial V}\right)}_{T={T}_c}=0 \mathrm{and} {\left(\frac{\partial^2P}{\partial {V}^2}\right)}_{T={T}_c}=0 $$
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References

  1. Sverjensky DA, Harrison B, Azzolini D (2014) Water in the deep earth: the dielectric constant and the solubilities of quartz and corundum to 60 kb and 1200 °C. Geochim Cosmochim Acta 129:125–145CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Chemistry and Department of Earth and Planetary SciencesUniversity of CaliforniaDavisUSA
  2. 2.College of Math and Physical Sciences, Department of ChemistryUniversity of CaliforniaDavisUSA