Ultraviolet Spectroscopic Study of Ferric Hydroxide Complexation

Robert H. Byrne, Dana R. Kester

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Abstract

<p> Ultraviolet absorbance spectra of ferric ions in 0.68 <em> m </em> NaClO <sub> 4 </sub> were studied as a function of pH at 4.0, 14.9, and 25.0&deg;C. The results provided an evaluation of the stability constant for the formation of FeOH <sup> 2+ </sup> which is *&beta; <sub> 1 </sub> =[ <em> FeOH </em> <sup> + </sup> ][ <em> H </em> <sup> + </sup> ]/[ <em> Fe </em> <sup> 3+ </sup> ]. The enthalpy change for the reaction Fe <sup> 3+ </sup> +H <sub> 2 </sub> O&rlhar; FeOH <sup> 2+ </sup> +H <sup> + </sup> was calculated as 10.0&plusmn;0.3 kcal-mole <sup> &minus;1 </sup> . Increasing temperature was also found to promote the reaction Fe <sup> 3+ </sup> +2H <sub> 2 </sub> O&rlhar; Fe(OH) <sup> + </sup> <sub> 2 </sub> +2H <sup> + </sup> . Our results were combined with the results of other to produce an expression describing the first hydrolysis equilibrium at ionic strengths between 0 and 3 <em> m </em> and temperatures between 4.0 and 45.0&deg;C at 1 atm total pressure. At 25&deg;C and 0.68 <em> m </em> the ionic strength *&beta; <sub> 1 </sub> =1.90&times;10 <sup> -3 </sup></p>
Original languageAmerican English
JournalJournal of Solution Chemistry
Volume7
DOIs
StatePublished - Jan 1 1978

Keywords

  • Ferric
  • hydrolysis
  • ionic strength
  • temperature
  • enthalpy
  • ferric hydroxide
  • ultraviolet
  • spectroscopic

Disciplines

  • Life Sciences

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