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Lizhi Xiao - One of the best experts on this subject based on the ideXlab platform.

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Frank J Millero - One of the best experts on this subject based on the ideXlab platform.

  • the dissociation of Carbonic Acid in nacl solutions as a function of concentration and temperature
    Geochimica et Cosmochimica Acta, 2007
    Co-Authors: Frank J Millero, Fe Huang, Taylo Graham, Denis Pierro
    Abstract:

    Abstract Potentiometric measurements of the stoichiometric constants for the dissociation of Carbonic Acid in NaCl solutions ( K 1 ∗ = [ H + ] [ HCO 3 - ] / [ CO 2 ] and K 1 ∗ = [ H + ] [ CO 3 2 - ] / [ HCO 3 - ] ) have been made as a function of molality (0–6 m) and temperature (0–50 °C). The results have been fitted to the equations p K i ∗ - p K i = A i + B i / T + C i ln T The values of pKi in pure water are taken from the literature and the adjustable parameters Ai, Bi and Ci are a function of molality A 1 = 35.2911 m 0.5 + 0.8491 m - 0.32 m 1.5 + 0.055 m 2 B 1 = - 1583.09 m 0.5 C 1 = - 5.4366 m 0.5 A 2 = 38.2746 m 0.5 + 1.6057 m - 0.647 m 1.5 + 0.113 m 2 B 2 = - 1738.16 m 0.5 C 2 = - 6.0346 m 0.5 (σ = 0.013 for p K 1 ∗ and σ = 0.020 for p K 2 ∗ , N = 603). The values determined in this study are in good agreement with the 25 °C literature values. Our results have been combined with previous measurements to derive equations that are valid from 0 to 250 °C and 0 to 5 m. This large data set has been used to determine the Pitzer parameters (β(0), β(1) and Cϕ) for the interactions of Na+ with HCO3− and CO32− from 0 to 250 °C. These results extend the carbonate system Pitzer model to hydrothermal brines containing high concentrations of NaCl.

  • dissociation constants of Carbonic Acid in seawater as a function of salinity and temperature
    Marine Chemistry, 2006
    Co-Authors: Frank J Millero, Fe Huang, Taylo Graham, Hecto Ustosserrano, Denis Pierro
    Abstract:

    Potentiometric measurements of the stoichiometric constants on the seawater pH scale for the dissociation of Carbonic Acid in seawater (K1⁎ = [H+][HCO3−]/[CO2] and K2⁎ = [H+][CO32−]/[HCO3−]) have been made as a function of salinity (1 to 50) and temperature (0 to 50 °C). The results have been fitted to the equations (T/K) pKi−pKi0=Ai+Bi/T+Ciln⁢T. The values of pKi0 in pure water are taken from the early work of Harned and Davis (1943) and Harned and Scholes (1941) pK10=−126.34048+6320.813/T+19.568224⁢ln⁢T pK20=−90.18333+5143.692/T+14.613358⁢ln⁢T. The value of the adjustable parameters Ai, Bi and Ci for pK1⁎ are given by (σ = 0.0054 and N = 466) A1=13.4191S0.5+0.0331⁢S−5.33⁢E−05S2A1=13.4191S0.5+0.0331⁢S−5.33⁢E−05S2 B1=−530.123S0.5−6.103⁢SB1=−530.123S0.5−6.103⁢S C1=−2.06950S0.5.C1=−2.06950S0.5. For pK2⁎ the parameters are given by (σ = 0.011 and N = 458) A2=21.0894S0.5+0.1248⁢S−3.687⁢E−04S2A2=21.0894S0.5+0.1248⁢S−3.687⁢E−04S2 B2=−772.483S0.5−20.051⁢SB2=−772.483S0.5−20.051⁢S C2=−3.3336S0.5.C2=−3.3336S0.5. The values of pK1⁎ and pK2⁎ determined in this study are in good agreement with the seawater (SW) measurements of Mehrbach et al. (1973) and Mojica-Prieto and Millero (2002) from S = 15 to 45 and 0 to 40 °C. The values of pK1⁎ near S = 35 are also in reasonable agreement with the measurements in artificial seawater (ASW) of Goyet and Poisson (1989) and Roy et al. (1993) from 0 to 35 °C. The values of pK2⁎ in real seawater, however, do not agree with the measurement made in artificial seawater at temperatures above 5 °C. Calculations of pK1⁎ and pK2⁎ near 25 °C using an ionic interaction model (Millero and Roy, 1997) suggest that the pK2⁎ results in SW are more reliable than in ASW. The equations from this study should be valid from S = 0 to 50 and t = 0 to 50 °C for most estuarine and marine waters (check values at S = 35 and t = 25 °C are pK1⁎ = 5.8401 and pK2⁎ = 8.9636).

  • dissociation constants of Carbonic Acid in seawater as a function of salinity and temperature
    Marine Chemistry, 2006
    Co-Authors: Frank J Millero, Taylor B Graham, Fen Huang, Hector Bustosserrano, Denis Pierrot
    Abstract:

    Abstract Potentiometric measurements of the stoichiometric constants on the seawater pH scale for the dissociation of Carbonic Acid in seawater (K1⁎ = [H+][HCO3−]/[CO2] and K2⁎ = [H+][CO32−]/[HCO3−]) have been made as a function of salinity (1 to 50) and temperature (0 to 50 °C). The results have been fitted to the equations (T/K) p K i − p K i 0 = A i + B i / T + C i ln ⁢ T . The values of pKi0 in pure water are taken from the early work of Harned and Davis (1943) and Harned and Scholes (1941) p K 1 0 = − 126.34048 + 6320.813 / T + 19.568224 ⁢ ln ⁢ T p K 2 0 = − 90.18333 + 5143.692 / T + 14.613358 ⁢ ln ⁢ T . The value of the adjustable parameters Ai, Bi and Ci for pK1⁎ are given by (σ = 0.0054 and N = 466) A 1 = 13.4191 S 0.5 + 0.0331 ⁢ S − 5.33 ⁢ E − 05 S 2 B 1 = − 530.123 S 0.5 − 6.103 ⁢ S C 1 = − 2.06950 S 0.5 . For pK2⁎ the parameters are given by (σ = 0.011 and N = 458) A 2 = 21.0894 S 0.5 + 0.1248 ⁢ S − 3.687 ⁢ E − 04 S 2 B 2 = − 772.483 S 0.5 − 20.051 ⁢ S C 2 = − 3.3336 S 0.5 . The values of pK1⁎ and pK2⁎ determined in this study are in good agreement with the seawater (SW) measurements of Mehrbach et al. (1973) and Mojica-Prieto and Millero (2002) from S = 15 to 45 and 0 to 40 °C. The values of pK1⁎ near S = 35 are also in reasonable agreement with the measurements in artificial seawater (ASW) of Goyet and Poisson (1989) and Roy et al. (1993) from 0 to 35 °C. The values of pK2⁎ in real seawater, however, do not agree with the measurement made in artificial seawater at temperatures above 5 °C. Calculations of pK1⁎ and pK2⁎ near 25 °C using an ionic interaction model (Millero and Roy, 1997) suggest that the pK2⁎ results in SW are more reliable than in ASW. The equations from this study should be valid from S = 0 to 50 and t = 0 to 50 °C for most estuarine and marine waters (check values at S = 35 and t = 25 °C are pK1⁎ = 5.8401 and pK2⁎ = 8.9636).

  • dissociation constants for Carbonic Acid determined from field measurements
    Deep Sea Research Part I: Oceanographic Research Papers, 2002
    Co-Authors: Frank J Millero, Denis Pierro, Kitack Lee, Rik Wanninkhof, Richard A Feely, Christophe L Sabine, Robe M Key, Taro Takahashi
    Abstract:

    A number of workers have recently shown that the thermodynamic constants for the dissociation of Carbonic Acid in seawater of Mehrbach et al. are more reliable than measurements made on artificial seawater. These studies have largely been confined to looking at the internal consistency of measurements of total alkalinity (TA), total inorganic carbon dioxide (TCO2) and the fugacity of carbon dioxide (fCO2). In this paper, we have examined the field measurements of pH, fCO2, TCO2 and TA on surface and deep waters from the Atlantic, Indian, Southern and Pacific oceans to determine the pK1, pK2 and pK2−pK1. These calculations are possible due to the high precision and accuracy of the field measurements. The values of pK2 and pK2−pK1 over a wide range of temperatures (−1.6–38°C) are in good agreement (within ±0.005) with the results of Mehrbach et al. The measured values of pK1 at 4°C and 20°C are in reasonable agreement (within ±0.01) with all the constants determined in laboratory studies. These results indicate, as suggested by internal consistency tests, that the directly measured values of pK1+pK2 of Mehrbach et al. on real seawater are more reliable than the values determined for artificial seawater. It also indicates that the large differences of pK2−pK1 (0.05 at 20°C) in real and artificial seawater determined by different investigators are mainly due to differences in pK2. These differences may be related to the interactions of boric Acid with the carbonate ion. The values of pK2−pK1 determined from the laboratory measurements of Lee et al. and Lueker et al. at low fCO2 agree with the field-derived data to ±0.016 from 5°C to 25°C. The values of pK2−pK1 decrease as the fCO2 or TCO2 increases. This effect is largely related to changes in the pK2 as a function of fCO2 or TCO2. The values of fCO2 calculated from an input of TA and TCO2, which require reliable values of pK2−pK1, also vary with fCO2. The field data at 20°C has been used to determine the effect of changes of TCO2 on pK2 giving an empirical relationship: which is valid at TCO2>2050 μmol kg−1. This assumes that the other dissociation constants such as KB for boric Acid are not affected by changes in TCO2. The slope is in reasonable agreement with the laboratory studies of Lee et al. and Lueker et al. (−1.2×10−4 to −1.9×10−4). This equation eliminates the dependence of the calculated fCO2 on the level of fCO2 or TCO2 in ocean waters (σ=29.7 μatm in fCO2). An input of pH and TCO2 yields values of fCO2 and TA that are in good agreement with the measured values (±22.3 μatm in fCO2 and ±4.3 μmol kg−1 in TA). The cause of the decrease in pK2 at high fCO2 is presently unknown. The observed inconsistencies between the measured and computed fCO2 values may be accounted for by adding the effect of organic Acid (∼8 μmol kg−1) to the interpretation of the TA. Further studies are needed to elucidate the chemical reactions responsible for this effect.

  • the values of pk1 pk2 for the dissociation of Carbonic Acid in seawater
    Geochimica et Cosmochimica Acta, 2002
    Co-Authors: Francisco Javier Mojica Prieto, Frank J Millero
    Abstract:

    The values of pK1 + pK2 for the dissociation of Carbonic Acid have been determined in seawater as a function of temperature (0 to 45°C) and salinity (5 to 42). They were determined by the addition of NaHCO3 to seawater stripped of CO2 until the pH0 = 1/2(pK1 + pK2) was constant. The pH0 was measured using potentiometric and spectrophotometric techniques. The values of pH0 determined by the two methods are in good agreement (± 0.002). Our values of 1/2(pK1 + pK2) are in good agreement (0.005) with the results of Mehrbach et al. (1973) and the combined data have been fitted to the equation with a σ = 0.0052. Both studies indicate that the measurements of pK2 in artificial seawater are lower than the values in real seawater. Values of the pK1 in seawater were also determined from potentiometric titrations of seawater at a few temperatures (15 to 45°C). The results are in better agreement (0.01) with the results of Mehrbach et al. between 20 to 30°C than other workers. Our results and those of Mehrbach et al. have been combined to yield (σ = 0.0056) and (σ = 0.010) These studies indicate that the values of K1 (SW) > K1 (ASW) by ∼0.01 and K2 (SW) < K2 (ASW) by ∼0.04 near 25°C. Measurements of pK1 + pK2 and pK1 in artificial seawater with and without boric Acid show the same trends, indicating that the effect is due to interactions of boric Acid with HCO3− and CO32−. Further studies are needed to elucidate these interactions.

Evamaria Kock - One of the best experts on this subject based on the ideXlab platform.

  • alpha Carbonic Acid revisited Carbonic Acid monomethyl ester as a solid and its conformational isomerism in the gas phase
    Chemistry: A European Journal, 2020
    Co-Authors: Klaus R Liedl, Evamaria Kock, Jurgen Bernard, Maren Podewitz, Dennis F Dinu, Roland G Huber, Hinrich Grothe, E Bertel
    Abstract:

    In this work, earlier studies reporting alpha-H2 CO3 are revised. The cryo-technique pioneered by Hage, Hallbrucker, and Mayer (HHM) is adapted to supposedly prepare Carbonic Acid from KHCO3 . In methanolic solution, methylation of the salt is found, which upon Acidification transforms to the monomethyl ester of Carbonic Acid (CAME, HO-CO-OCH3 ). Infrared spectroscopy data both of the solid at 210 K and of the evaporated molecules trapped and isolated in argon matrix at 10 K are presented. The interpretation of the observed bands on the basis of Carbonic Acid [as suggested originally by HHM in their publications from 1993-1997 and taken over by Winkel et al., J. Am. Chem. Soc. 2007 and Bernard et al., Angew. Chem. Int. Ed. 2011] is inferior compared with the interpretation on the basis of CAME. The assignment relies on isotope substitution experiments, including deuteration of the OH- and CH3 - groups as well as (12) C and (13) C isotope exchange and on variation of the solvents in both preparation steps. The interpretation of the single molecule spectroscopy experiments is aided by a comprehensive calculation of high-level ab initio frequencies for gas-phase molecules and clusters in the harmonic approximation. This analysis provides evidence for the existence of not only single CAME molecules but also CAME dimers and water complexes in the argon matrix. Furthermore, different conformational CAME isomers are identified, where conformational isomerism is triggered in experiments through UV irradiation. In contrast to earlier studies, this analysis allows explanation of almost every single band of the complex spectra in the range between 4000 and 600 cm(-1) .

  • alpha Carbonic Acid revisited Carbonic Acid monomethyl ester as a solid and its conformational isomerism in the gas phase
    Chemistry: A European Journal, 2020
    Co-Authors: Klaus R Liedl, Evamaria Kock, Maren Podewitz, Dennis F Dinu, Hinrich Grothe, Jurge Ernard, Roland G Hube, E Ertel
    Abstract:

    In this work, earlier studies reporting α-H2 CO3 are revised. The cryo-technique pioneered by Hage, Hallbrucker, and Mayer (HHM) is adapted to supposedly prepare Carbonic Acid from KHCO3 . In methanolic solution, methylation of the salt is found, which upon Acidification transforms to the monomethyl ester of Carbonic Acid (CAME, HO-CO-OCH3 ). Infrared spectroscopy data both of the solid at 210 K and of the evaporated molecules trapped and isolated in argon matrix at 10 K are presented. The interpretation of the observed bands on the basis of Carbonic Acid [as suggested originally by HHM in their publications from 1993-1997 and taken over by Winkel et al., J. Am. Chem. Soc. 2007 and Bernard et al., Angew. Chem. Int. Ed. 2011] is inferior compared with the interpretation on the basis of CAME. The assignment relies on isotope substitution experiments, including deuteration of the OH- and CH3 - groups as well as 12 C and 13 C isotope exchange and on variation of the solvents in both preparation steps. The interpretation of the single molecule spectroscopy experiments is aided by a comprehensive calculation of high-level ab initio frequencies for gas-phase molecules and clusters in the harmonic approximation. This analysis provides evidence for the existence of not only single CAME molecules but also CAME dimers and water complexes in the argon matrix. Furthermore, different conformational CAME isomers are identified, where conformational isomerism is triggered in experiments through UV irradiation. In contrast to earlier studies, this analysis allows explanation of almost every single band of the complex spectra in the range between 4000 and 600 cm-1 .

  • Carbonic Acid monoethyl ester as a pure solid and its conformational isomerism in the gas phase
    RSC Advances, 2017
    Co-Authors: Klaus R Liedl, Evamaria Kock, Hinrich Grothe, Jurge Ernard, Roland G Hube, Ludwig Call, Robe Schlogl, Thomas Loerting
    Abstract:

    The monoesters of Carbonic Acid are deemed to be unstable and decompose to alcohol and carbon dioxide. In spite of this, we here report the isolation of the elusive Carbonic Acid monoethyl ester (CAEE) as a pure solid from ethanolic solutions of potassium bicarbonate. The hemiester is surprisingly stable in Acidic solution and does not experience hydrolysis to Carbonic Acid. Furthermore, it is also stable in the gas phase, which we demonstrate by subliming the hemiester without decomposition. This could not be achieved in the past for any hemiester of Carbonic Acid. In the gas phase the hemiester experiences conformational isomerism at 210 K. Interestingly, the thermodynamically favored conformation is only reached for the torsional movement of the terminal ethyl group, but not the terminal hydrogen atom on the millisecond time scale. Accordingly, IR spectra of the gas phase trapped in an argon matrix are best explained on the basis of a 5 : 1 mixture of monomeric conformers. Our findings necessitate reevaluation of claims of the formation of a Carbonic Acid polymorph in methanolic solution, which is the subject of a forthcoming publication.