Use of Pitzer equations to examine the formation of mercury(II) hydroxide and chloride complexes in NaClO4 media

Melchor González-Dávila, J. Magdalena Santana-Casiano, Frank J. Millero

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3 Scopus citations


The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg2+) chloride complexes Hg2+ + nH2O = Hg(OH)n(2-n)+ + nH+ βn Hg2+ + nCl- = HgCln(2-n)+ βi have been used to calculate the activity coefficients for Hg(OH)n(2-n)+ and HgCln(2-n)+ complexes using the Pitzer specific interaction model. These values have been used to determine the Pitzer parameters for the hydroxide and chloro complexes βML(0), βML (1) and CML). The values of λij and ζijk have been determined for the neutral complexes (Hg(OH)2 and HgCl2). The resultant parameters yield calculated values for the measured values of log β* to ±0.01 from I = 0.1 to 3 m at 25°C. Since the activity coefficients of Hg(OH)n(2-n)+ and HgCln(2-n)+ are in reasonable agreement with the values for Pb(II), we have estimated the effect of temperature on the chloride constants for Hg(II) from 0 to 300°C and I = 0-6 m using the Pitzer parameters for PbCln(2-n)+ complexes. The resulting parameters can be used to examine the speciation of Hg(II) with Cl- in natural waters over a wide range of conditions.

Original languageEnglish (US)
Pages (from-to)339-355
Number of pages17
JournalAquatic Geochemistry
Issue number4
StatePublished - Dec 1 2007



  • Activity coefficients
  • Chloride complexes
  • Mercury(II) hydroxide
  • NaClO
  • Pitzer equations
  • Speciation

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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