Measurement of pH at elevated temperatures using the optical indicator acridine

Youngsook Huh, Jae Gook Lee, D. C. McPhail, Keon Kim

Research output: Contribution to journalArticle

16 Citations (Scopus)


A new method of measuring the pH of high-temperature aqueous solutions using optical indicators was developed. The absorbance spectrum of acridine changes as a function of pH, allowing its use as an optical indicator for pH. The pKa of acridine were experimentally determined in KOH-AcOH pH-buffer solutions at temperatures from 5 to 250°C at vaporsaturated pressures: {Mathematical expression} where T is in Kelvin. The technique is demonstrated by experimentally determining the pKa of benzoic acid at temperatures up to 250°C where the result was {Mathematical expression}

Original languageEnglish
Pages (from-to)651-661
Number of pages11
JournalJournal of Solution Chemistry
Issue number7
Publication statusPublished - 1993 Jul 1


  • acid dissociation constant
  • acridine
  • benzoic acid
  • Optical indicator
  • pH

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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