Activity coefficients of (hydrogen chloride + europium chloride) (aq) using Harned's rule and the Pitzer formalism

Rabindra N. Roy, Lakshmi N. Roy, Darin Gregory, Andria VanLanduyt, Denis Pierrot, Frank J. Millero

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Activity coefficients of HCl in (hydrogen chloride + europium chloride) have been determined at temperatures ranging from 278.15 K to 328.15 K at 5 K intervals and at eight constant total ionic strengths of (0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 1.5, and 2.0) mol kg-1. Experimental cell potentials were obtained using a cell without liquid junction of the type Pt|H2(g, p = 101.325 kPa)|HCl (mA), EuCl3 (mB)|AgCl(s)|Ag(s). The treatment of Harned has been used to describe the mean molal activity coefficient of hydrochloric acid as a function of ionic strength in acid salt mixtures. Results indicate that the quadratic form is sufficient for the full range of YB (the ionic strength fraction of the salt) to 0.9 at all the experimental ionic strengths. The ion-interaction model of Pitzer has also been used to calculate Pitzer's mixing parameters ΘH,Eu and ψH,Cl,Eu for the system H+ + Eu3+ + Cl- + H2O. The values found, ΘH,Eu = 0.2 ± 0.03 and ψH,Cl,Eu = 0, were similar to those for other trivalent ions studied previously. The parameters used in this study reproduce the activity coefficients of HCl in the mixtures to within 0.016 over the entire range of ionic strengths and within 0.009 for I > 0.05 mol kg-1 over the entire temperature range.

Original languageEnglish (US)
Pages (from-to)551-556
Number of pages6
JournalJournal of Chemical and Engineering Data
Issue number3
StatePublished - May 1 2001

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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