Encyclopedia of Geochemistry

2018 Edition
| Editors: William M. White

Clapeyron’s Equation

  • Masaki AkaogiEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-39312-4_301


We consider here that a substance changes from a reactant phase to a product phase and that both the phases are in equilibrium at pressure (P) and temperature (T). Clapeyron’s equation expresses the stability relation between the reactant and product phases and gives a dP/dT slope of equilibrium phase boundary between the reactant and the product as a function of P and T. This equation is one of the most important equations for understanding thermodynamic stability relations in geochemical, petrological, and mineralogical processes. For example, when α-quartz SiO2 is in equilibrium with coesite at certain P, T conditions, Clapeyron’s equation gives the slope of the equilibrium quartz-coesite transition boundary in a P-T space where quartz is stable at relatively lower P and higher T and coesite at relatively higher P and lower T.

Clapeyron’s Equation

When reactant and product phases are in equilibrium at P and T, and changes of entropy (ΔS) and volume (ΔV) accompany with the...
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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of ChemistryGakushuin UniversityTokyoJapan