The Pourbaix diagrams (potential-pH diagrams) for chromium at 25-300 d
egrees C have been revised. The diagrams were calculated for two conce
ntrations: 10(-6) and 10(-8) molal. Extrapolation of thermochemical da
ta to elevated temperatures has been performed with the revised model
of Helgeson-Kirkham-Flowers, which also allows uncharged aqueous compl
exes, such as Cr(OH)(3)(aq), to be handled. The calculations show that
the hydroxides Cr(OH)(2), Cr(OH)(3), and the oxides CrO2 and CrO3 are
not stable at the investigated temperature and concentration interval
. Cr2O3 is the only stable solid chromium compound in aqueous solution
in the environment studied, with the exception of very diluted soluti
ons such as 10(-8) molal at T > 150 degrees C, where no solid chromium
compound is stable. The dichromate ion does not predominate anywhere
within the calculated concentration range. Copyright (C) 1996 Elsevier
Science Ltd