The Eh-pH diagram for N-H2O system at 623 K calculated by the revised HKF equation

Satoshi Uchida, Miho Uchida, Akitsugu Okuwaki, Yoshiaki Umetsu

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The Eh-pH diagram (Pourbaix diagram) for N-H2O system was constructed at 623 K based on the revised HKF (H. C. Helgeson, D. H. Kirkham and G. C. Flowers) equation. The fundamental thermodynamic data such as Cp° and ΔG° were derived from the HKF equation directly for ionic species, and from the combination of HKF equation and the Electrostatic Non-Electrostatic Model (H. C. Helgeson) for neutral species. Comparing the Eh-pH diagram at 623 K with that at 298 K, all boundaries between gaseous species were found to slant to the lower E with increasing pH. The stable regions of neutral species, i.e. NH4OH (aq) and HNO3(aq), expanded toward the neutral pH at 623 K, possibly because of the formation of ion pairs.

Original languageEnglish
Pages (from-to)739-741
Number of pages3
JournalNippon Kagaku Kaishi / Chemical Society of Japan - Chemistry and Industrial Chemistry Journal
Issue number8
Publication statusPublished - 1996 Dec 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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