An experimental determination of ferrous chloride and acetate complexation in aqueous solutions to 300[degrees]C

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90001-D· OSTI ID:6483737

Palmer, D A ^[1]; Hyde, K E ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. State Univ. of New York, Oswego (United States)

Reliable thermodynamic information on the stability of ferrous chloride complexes at high temperatures is important to evaluations of iron transport in hydrothermal fluids, and to the power industry for iron corrosion and transport in the water/steam cycle. The formation of the monochloroiron(II) complex, FeCl[sup +], was studied potentiometrically from 125 to 295[degrees]C at 25 degree intervals at one molal ionic strength in aqueous solutions containing acetic acid, sodium acetate, and sodium trifluoromethanesulfonate. In this method, competition between chloride and acetate ions for the ferrous cation resulted in a change in solution pH, which in turn was monitored in situ in a hydrogen-electrode, concentration cell. A simple empirical approach was used to extrapolate these formation quotients to infinite dilution. The resulting constants proved to be in excellent agreement with previous spectrophotometric results obtained from 25 to 200[degrees]C. Thus, the present study confirms the validity of the conclusions made based on these earlier data concerning the solubility of Fe-containing minerals in hydrothermal brines. Formation constants at infinite dilution for FeCl[sup +] are compared with the stability of ferrous acetate and hydroxide complexes. The original potentiometric titration data for ferrous acetate complex formation were combined in a new fit with values determined from the present study at unit ionic strength. Two empirical treatments (namely the isocoulombic method and the temperature/water density function) were considered for fitting and extrapolating the infinite dilution formation constants to 350[degrees]C. 40 refs., 12 figs., 5 tabs.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6483737
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 57:7; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
HYDROTHERMAL SYSTEMS
SOLUBILITY
IRON
ENVIRONMENTAL TRANSPORT
IRON COMPLEXES
POTENTIOMETRY
AQUEOUS SOLUTIONS
BRINES
IRON CHLORIDES
POWER GENERATION
TEMPERATURE RANGE 0400-1000 K
CHLORIDES
CHLORINE COMPOUNDS
COMPLEXES
DISPERSIONS
ELEMENTS
GEOTHERMAL SYSTEMS
HALIDES
HALOGEN COMPOUNDS
IRON COMPOUNDS
MASS TRANSFER
METALS
MIXTURES
SOLUTIONS
TEMPERATURE RANGE
TITRATION
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400102* - Chemical & Spectral Procedures
540220 - Environment
Terrestrial- Chemicals Monitoring & Transport- (1990-)
540320 - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)