Computer Science
Scientific paper
Jun 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982gecoa..46.1011n&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 46, Issue 6, pp.1011-1040
Computer Science
66
Scientific paper
Calculations based on approximately 350 new measurements (Ca T -PCO 2 ) of the solubilities of calcite, aragonite and vaterite in CO 2 -H 2 O solutions between 0 and 90°C indicate the following values for the log of the equilibrium constants K C , K A , and K V respectively, for the reaction CaCO 3 (s) = Ca 2+ + CO 2- 3 : Log K C = -171.9065 - 0.077993 T + 2839.319/ T + 71.595 log T Log K A = -171.9773 - 0.077993 T + 2903.293/ T +71.595 log T Log K V = -172.1295 - 0.077993 T + 3074.688/ T + 71.595 log T where T is in o K. At 25°C the logarithms of the equilibrium constants are -8.480 ± 0.020, -8.336 ± 0.020 and -7.913 ± 0.020 for calcite, aragonite and vaterite, respectively. The equilibrium constants are internally consistent with an aqueous model that includes the CaHCO + 3 and CaCO 0 3 ion pairs, revised analytical expressions for CO 2 -H 2 O equilibria, and extended Debye-Hückel individual ion activity coefficients. Using this aqueous model, the equilibrium constant of aragonite shows no PCO 2 -dependence if the CaHCO + 3 association constant is Log K Cahco + 3 = 1209.120 + 0.31294 T -- 34765.05/ T - 478.782 log T between 0 and 90°C, corresponding to the value log K Cahco + 3 = 1.11 ± 0.07 at 25°C. The CaCO 0 3 association constant was measured potentiometrically to be log K CaCO 0 3 = -1228.732 - 0.299444 T + 35512.75/ T + 485.818 log T between 5 and 80°C, yielding log K CaCO 0 3 = 3.22 ± 0.14 at 25°C. The CO 2 -H 2 O equilibria have been critically evaluated and new empirical expressions for the temperature dependence of K H , K 1 and K 2 are log K H = 108.3865 + 0.01985076 T - 6919.53/ T - 40.45154 log T + 669365./ T 2 , log K 1 = -356.3094 - 0.06091964 T + 21834.37/ T + 126.8339 log T -- 1684915./ T 2 and log K 2 = -107.8871 - 0.03252849 T + 5151.79/ T + 38.92561 log T - 563713.9/ T 2 which may be used to at least 250°C. These expressions hold for 1 atm. total pressure between 0 and 100°C and follow the vapor pressure curve of water at higher temperatures. Extensive measurements of the pH of Ca-HCO 3 solutions at 25°C and 0.956 atm PCO 2 using different compositions of the reference electrode filling solution show that measured differences in pH are closely approximated by differences in liquid-junction potential as calculated by the Henderson equation. Liquid-junction corrected pH measurements agree with the calculated pH within 0.003-0.011 pH. Earlier arguments suggesting that the CaHCO + 3 ion pair should not be included in the CaCO 3 -CO 2 -H 2 O aqueous model were based on less accurate calcite solubility data. The CaHCO + 3 ion pair must be included in the aqueous model to account for the observed PCO 2 -dependence of aragonite solubility between 317 ppm CO 2 and 100% CO 2 . Previous literature on the solubility of CaCO 3 polymorphs have been critically evaluated using the aqueous model and the results are compared.
Busenberg Eurybiades
Niel Plummer L.
No associations
LandOfFree
The solubilities of calcite, aragonite and vaterite in CO 2 -H 2 O solutions between 0 and 90°C, and an evaluation of the aqueous model for the system CaCO 3 -CO 2 -H 2 O does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The solubilities of calcite, aragonite and vaterite in CO 2 -H 2 O solutions between 0 and 90°C, and an evaluation of the aqueous model for the system CaCO 3 -CO 2 -H 2 O, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The solubilities of calcite, aragonite and vaterite in CO 2 -H 2 O solutions between 0 and 90°C, and an evaluation of the aqueous model for the system CaCO 3 -CO 2 -H 2 O will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1353932