On the influence of carbonate in mineral dissolution: II. The solubility of FeCO sub 3 (s) at 25C and 1 atm total pressure
- Swiss Federal Inst. of Tech., Duebendorf (Switzerland)
The solubility of siderite in acid, neutral, and alkaline medium was investigated. The experiments were performed as potentiometric titrations under two constant partial pressures of CO{sub 2} (g). This yielded the following equilibrium constants at 25C in a 1.0 M NaClO{sub 4} medium (quoted errors through this work are given at 2{sigma} confidence level). (1) The solubility constant of FeCO{sub 3} (s): FeCO{sub 3} (s) + 2H{sup +} = Fe{sup 2+} + CO{sub 2} (g) + H{sub 2}O, with log K{sub s{sup 0}}{sup *} = 7.59 {plus minus} 0.08. (2) The formation constants for the two determined Fe(II) carbonate complexes: Fe{sub 2+} + CO{sub 2} (g) + H{sub 2}O = FeCO{sub 3} (aq) + 2H{sup +}, with log {beta}{sub 11} = {minus}12.9 {plus minus} 0.12; Fe{sup 2+} + 2CO{sub 2} (g) + 2H{sub 2}O = Fe(CO{sub 3}){sub 2}{sup 2{minus}} + 4H{sup +}, with log {beta}{sub 12} = {minus}28.4 {plus minus} 0.10. By extrapolation to infinite dilution, the following reaction equilibria are estimated for the infinite dilution standard state: FeCO{sub 3} (s) = Fe{sup 2+} + CO{sub 3}{sup 2{minus}}, with log K{sub sp} = {minus}10.8 {plus minus} 0.2; Fe{sup 2+} + CO{sub 3}{sup 2{minus}} = FeCO{sub 3} (aq), with log {beta}{sub 1} = 5.5 {plus minus} 0.2; Fe{sup 2+} + 2CO{sub 3}{sup 2{minus}} = Fe(CO{sub 3}){sub 2}{sup 2{minus}}, with log {beta}{sub 2} = 7.1 {plus minus} 0.2. The determined solubility constant is in fair agreement with previously derived solubility data. The identified complexes and their formation constants emphasize their importance in various anoxic water. However, carbonate complex formation does not account for the supersaturation conditions with regard to siderite equilibrium observed in many other present-day environments.
- OSTI ID:
- 5087933
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:3; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
Similar Records
Experimental determination of the hydrolysis constants of Pt sup 2+ and Pd sup 2+ at 25C from the solubility of Pt and PD in aqueous hydroxide solutions
On the influence of carbonate on mineral dissolution: III. The solubility of microcrystalline ThO[sub 2] in CO[sub 2]-H[sub 2]O media
Related Subjects
152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
58 GEOSCIENCES
580000 -- Geosciences
AQUEOUS SOLUTIONS
ATMOSPHERIC PRESSURE
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
CHEMISTRY
DATA
DISPERSIONS
DISSOLUTION
ECOSYSTEMS
EQUILIBRIUM
EXPERIMENTAL DATA
INFORMATION
IRON CARBONATES
IRON COMPOUNDS
IRON ORES
MINERALS
MIXTURES
NUMERICAL DATA
ORES
OXIDES
OXYGEN COMPOUNDS
PARTIAL PRESSURE
POTENTIOMETRY
SIDERITE
SOLUBILITY
SOLUTIONS
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TITRATION
TRANSITION ELEMENT COMPOUNDS
WATER CHEMISTRY