## 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]} = lnγ_{B} = (2ν_{c}λ _{Bc} + 2ν_{a}λ_{Ba})m + ν_{c}ν _{a}ζ_{B-a-c}m^{2} where [B]^{0} is the concentration of boric acid in water and [B] in solution, γ_{B} is the activity coefficient, ν_{i} is the number of ions (i), λ_{Bc}, λ_{Ba} are parameters related to the interaction of boric acid with cation c and anion a, ζ_{B-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 2ν_{c}λ_{Bc}+2ν_{a}λ _{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 SO_{4} > 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 ζ_{B-c-a} were estimated from known values of λ_{Bc} and λ_{Ba}. The values of λ_{Bc}, λ_{Ba}, and ζ_{B-a-c} can be used to estimate the boric acid activity coefficients γ_{B} and solubility [B] in natural mixed electrolyte solutions (seawater and brines) using the more general Pitzer equation ln{[B]^{0}/[B]} = lnλ_{B} = (2Σ_{c}ν_{c}λ _{Bc} + 2Σ_{a}ν_{a}λ_{Bac})m + Σ_{c}Σ_{a}ν_{c}ν_{a}ζ _{B-a-c}m^{2}.

Original language | English (US) |
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Pages (from-to) | 689-703 |

Number of pages | 15 |

Journal | Journal of Solution Chemistry |

Volume | 35 |

Issue number | 5 |

DOIs | |

State | Published - May 1 2006 |

## Keywords

- Activity coefficients
- Boric acid
- Electrolyte
- Pitzer coefficients
- Solubility

## ASJC Scopus subject areas

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