Spectroscopic determination of the critical temperatures and pressures of H2O, CO2, and C2H5OH

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The transmittance of 500-800 nm light was shown to change significantly at the critical points of three pure fluids. Spectroscopic measurements of H2O, CO2, and C2H5OH were made in a visible-type autoclave at high temperature and pressure. Each fluid showed significantly decreased transmittance as its critical point was approached; transmittance reached a local minimum at the critical temperature and pressure. The experimentally determined critical temperature and pressure of H2O are 374 °C and 22.07-22.09 MPa, respectively, similar to reference values of 374.15 °C and 22.12 MPa; C2H5OH showed values of 243 °C and 6.30-6.31 MPa (versus reference values of 241 ± 7 and 243.4 °C and 6.3 ± 0.4 and 6.14 MPa); and CO2 showed values of 32 °C and 7.36-7.43 MPa (versus reference values of 31.04 ± 0.2 °C and 7.37 ± 0.04 MPa). The good agreement between the experimental results and the reference values indicates that the spectroscopic method used here could be applied to other fluids, including mixed geofluids.

Original languageEnglish
Pages (from-to)356-361
Number of pages6
JournalJournal of Mineralogical and Petrological Sciences
Issue number6
Publication statusPublished - 2013 Dec 28


  • Critical point
  • Geofluids
  • Hydrothermal experiment
  • Spectroscopic measurement
  • Supercritical fluid

ASJC Scopus subject areas

  • Geophysics
  • Geology


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