A semi-Empirical equation for activity coefficients of ions with one parameter

Jai Yeop Lee, Ihnsup Han

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Based on the Debye-Húckel equation, a semi-empirical equation for activity coefficients was derived through empirical and theoretical trial and error efforts. The obtained equation included two parameters: the proportional factor and the effective radius of an ionic sphere. These parameters were used in the empirical and regression parameter fitting of the calculated values to the experimental results. The activity coefficients calculated from the equation agreed with the data. Transforming to a semi-empirical form, the equation was expressed with one parameter, the ion radius. The ion radius, α, was divided into three parameters, αcation, αanion and δcation, representing parameters for the cation, anion and combination, respectively. The advantage of this equation is the ability to propose a semi-empirical equation that can easily determine the activity coefficient with just one parameter, so the equation is expected to be used more widely in actual industry applications.

Original languageEnglish
Pages (from-to)3709-3714
Number of pages6
JournalBulletin of the Korean Chemical Society
Issue number12
StatePublished - 20 Dec 2013


  • Activity coefficient
  • Debye-Húckel equation
  • Semi-empirical equation


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