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A spectrophotometric study of aqueous iron (II) chloride complexing from 25 to 200 degree C

Journal Article · · Geochimica et Cosmochimica Acta; (USA)
 [1];  [2]
  1. Bureau of Mineral Resources, Canberra (Australia)
  2. Department of Scientific and Industrial Research, Petone (New Zealand)
Ultraviolet absorption spectra of solutions in the system FeCl{sub 2}-HCl-H{sub 2}O with chloride concentrations ranging from 0.01 to 3.4 m and Fe(II) concentrations ranging from 0.005 to 0.025 m have been measured at 25, 50, 100, 150, and 200{degree}C and the equilibrium saturation vapor pressure of the system. Non-linear least squares regression was used to estimate cumulative thermodynamic association constants and molar absorptivities. At 25, 50, and 100{degree}C, only Fe{sup 2+} and FeCl{sup +} are detectable, whereas at higher temperatures a minor concentration of a third species, interpreted to be FeCl{sup 0}{sub 2}, starts to contribute substantially to total absorbance. Recommended values of the association constants, {beta}{sub 1} and {beta}{sub 2}, for the equilibria Fe{sup 2+} + Cl{sup {minus}} = FeCl{sup +} and Fe{sup 2+} + 2Cl{sup {minus}} = FeCl{sup 0}{sub 2} are given. In combination with published thermodynamic data for the Fe-S-O-H system, the equilibrium formation constants are used to calculate solubilities of selected Fe mineral assemblages in NaCl-rich hydrothermal solutions. The results are in satisfactory agreement with published analytical data from basinal brines and geothermal fluids.
OSTI ID:
6265223
Journal Information:
Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:8; ISSN GCACA; ISSN 0016-7037
Country of Publication:
United States
Language:
English

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