The solubility of boric acid in electrolyte solutions

Mareva Chanson, Frank J. Millero

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The solubility of boric acid [B] in LiCl, NaCl, KCl, RbCl, and CsCl was determined as a function of ionic strength (0-6 mol·kg-1) at 25°C. The results were examined using the Pitzer equation ln{[B] 0/[B]} = lnγB = (2νcλ Bc + 2νaλBa)m + νcν aζB-a-cm2 where [B]0 is the concentration of boric acid in water and [B] in solution, γB is the activity coefficient, νi is the number of ions (i), λBc, λBa are parameters related to the interaction of boric acid with cation c and anion a, ζB-a-c is related to the interaction of boric acid with both cation and anion and m is the salt molality. The literature values for the solubility of boric acid in a number of other electrolytes were also examined using the same equation. The results for the 2νcλBc+2νaλ Ba term (equal to the salting coefficient k S) were examined in terms of the ionic interactions in the solutions. The solubility of boric acid in LiCl, NaCl, and KCl solutions is not a strong function of temperature and the results can be used over a limited temperature range (5-35°C). Boric acid is soluble in the order SO4 > NO 3 and F > Cl > Br > I in common cation solutions. In common anion salt solutions, the order is Cs > Rb > K > Na > Li > H and Ba > Sr > Ca > Mg. The results were examined using correlations of k S with the volume properties of the ions. When direct measurements were not available, k S and ζB-c-a were estimated from known values of λBc and λBa. The values of λBc, λBa, and ζB-a-c can be used to estimate the boric acid activity coefficients γB and solubility [B] in natural mixed electrolyte solutions (seawater and brines) using the more general Pitzer equation ln{[B]0/[B]} = lnλB = (2Σcνcλ Bc + 2ΣaνaλBac)m + ΣcΣaνcνaζ B-a-cm2.

Original languageEnglish (US)
Pages (from-to)689-703
Number of pages15
JournalJournal of Solution Chemistry
Volume35
Issue number5
DOIs
StatePublished - May 1 2006

Keywords

  • Activity coefficients
  • Boric acid
  • Electrolyte
  • Pitzer coefficients
  • Solubility

ASJC Scopus subject areas

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

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