Ionization of carbonic acid in sodium chloride solutions at 25°C

Valerie Thurmond, Frank J. Millero

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


The stoichiometric pK1* and pK2* for the ionization of carbonic acid has been determined from emf measurements in NaCl soluions to 6.0m at 25°C. Our results at low concentrations are in good agreement with the results of Harned and Bonner, of Dyrssen and Hansson and of Roy et al. The calculated values of pK1* using Pitzer's equations agree with the measured values to ±0.01 pK units provided higher order terms are used. It was necessary to use a triplet interaction parameter (ψ) and higher order electrostatic terms (Eθ) to calculate reliable values of pK2* (±0.03 pK units) over the entire concentration range. These results demonstrate the reliability of the Pitzer equations to estimate activity coefficients in concentrated salt solutions.

Original languageEnglish (US)
Pages (from-to)447-456
Number of pages10
JournalJournal of Solution Chemistry
Issue number7
StatePublished - Jul 1 1982


  • Carbonic acid
  • Pitzer's equations
  • activity coefficients
  • concentrated aqueous solutions
  • ionization constants

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry


Dive into the research topics of 'Ionization of carbonic acid in sodium chloride solutions at 25°C'. Together they form a unique fingerprint.

Cite this