The effect of pressure on the ionization of boric acid in sodium chloride and seawater from molal volume data at 0 and 25°C     

Gary K Ward  Frank J Millero 《Geochimica et cosmochimica acta》1975,39(12):1595-1604

The apparent molal volume, φ_V of boric acid, B(OH)₃ and sodium borate, NaB(OH)₄, have been determined in 35%. salinity seawater and 0·725 molal NaCl solutions at 0 and 25°C from precise density measurements. Similar to the behavior of nonelectrolytes and electrolytes in pure water, the φ_V of B(OH)₃ is a linear function of added molality and the φ_V of NaB(OH)₄ is a linear function of the square root of added molarity in seawater and NaCl solutions. The partial molal volumes, $\text{V}\text{?}\text{1}$, of B(OH)₃ and NaB(OH)₄ in seawater and NaCl were determined from the φ_V's by extrapolating to infinite dilution in the medium. The $\text{V}\text{?}\text{1}$ of B(OH)₃ is larger in NaCl and seawater than pure water apparently due to the ability of electrolytes to dehydrate the nonelectrolyte B(OH)₃. The $\text{V}\text{?}\text{1}$ of NaB(OH)₄ in itself, NaCl and seawater is larger than the expected value at 0·725 molal ionic strength due to ion pair formation [Na⁺ + B(OH)₄^? → NaB(OH)₄⁰]. The volume change for the formation of NaB(OH)₄⁰ in itself and NaCl was found to be equal to 29·4 ml mol^?1 at 25°C and 0·725 molal ionic strength. These large $\text{Δ}\text{V}\text{?}\text{1}$'s indicate that at least one water molecule is released when the ion pair is formed [Na⁺ + B(OH)₄^? → H₂O + NaOB(OH)₂⁰]. The observed $\text{V}\text{?}\text{1}$ in seawater and the $\text{Δ}\text{V}\text{?}\text{1}$ (NaB⁰) in water and NaCl were used to estimate $\text{Δ}\text{V}\text{?}\text{1 (MgB}{}^{\mathrm{+}}\text{) = Δ}\text{V}\text{?}\text{1 (CaB}{}^{\mathrm{+}}\text{) = 38·4 ml mol}{}^{\mathrm{?1}}$ for the formation of MgB⁺ and CaB⁺. The volume change for the ionization of B(OH)₃ in NaCl and seawater was determined from the molal volume data. Values of $\text{Δ}\text{V}\text{?}\text{1 = ?29·2 and ?25·9 ml mol}{}^{\mathrm{?1}}$ were found in seawater and $\text{Δ}\text{V}\text{?}\text{1 = ?21·6 and ?26·4}$ in NaCl, respectively, at 0 and 25°C. The effect of pressure on the ionization of B(OH)₃ in NaCl and seawater at 0 and 25°C determined from the volume change is in excellent agreement with direct measurements in artificial seawater (culberson and Pytkowicz, 1968; Disteche and Disteche, 1967) and natural seawater (Culberson and Pytkowicz, 1968).  相似文献   

Pressure dependence ot SrSO₄ solubility     

Neil A. North 《Geochimica et cosmochimica acta》1974,38(7):1075-1081

The solubilities of SrSO₄ in seawater, 0.65 M NaCl and and distilled water were measured as a function of pressure at 2°C. The thermodynamic solubility product was determined from the distilled water measurements and stoichiometric solubility products were determined from the seawater and Nad measurements. The equilibrium quotient for SrSO₄ dissolution at ionic strength of 0.65 was calculated from the NaCl measurements, using the known NaSO₄^? ionpairing association constant. For each of the solubility products values of $\text{Θ V}$ were determined. These experimental values were all $\text{11.0 ± 0.3}\text{ml}$ mole_? lower than the theoretical values based on anhydrous SrSO₄. This difference may be due to the equilibrating solid phase being a hydrated form of SrSO₄.  相似文献   

The effect of ionic interactions on the oxidation of metals in natural waters     

Frank J Millero 《Geochimica et cosmochimica acta》1985,49(2):547-553

The effect of ionic interactions of the major components of natural waters on the oxidation of Cu(I) and Fe(II) has been examined. The various ion pairs of these metals have been shown to have different rates of oxidation. For Fe(II), the chloride and sulfate ion pairs are not easily oxidized. The measured decrease in the rate constant at a fixed pH in chloride and sulfate solutions agrees very well with the values predicted. The effect of pH (6 to 8) on the oxidation of Fe(II) in water and seawater have been shown to follow the rate equation where k₁ and k₂ are the pseudo first order rate constants, β₁ and β₂ are the hydrolysis constants for Fe(OH)⁺ and Fe(OH)⁰. The value of α_FE is the fraction of free Fe²⁺. The value of k₁ (2.0 ±0.5 min^?1) in water and seawater are similar within experimental error. The value of k₂ (1.2 × 10⁵ min^?1) in seawater is 28% of its value in water in reasonable agreement with predictions using an ion pairing model.For the oxidation of Cu(I) a rate equation of the form was found where k₀ (14.1 sec^?1) and k₁ (3.9 sec^?1) are the pseudo first order rate constants for the oxidation of Cu⁺ and CuCl⁰, β₁ is the formation constant for CuCl⁰ and α_Cu is the fraction of free Cu⁺. Thus, unlike the results for Fe(II), Cu(I) chloride complexes have measurable rates of oxidation.  相似文献   

Copper(II) carbonate complexation in seawater     

Robert H. Byrne  William L. Miller 《Geochimica et cosmochimica acta》1985,49(8):1837-1844

Cupric carbonate and cupric bicarbonate complexation constants were determined in natural seawater and in a variety of synthetic media. The formation constants of CuHCO₃⁺, CuCO₃⁰ and Cu(CO₃)₂^2? at 25°C and zero ionic strength are: log β_H⁰ = 1.8, log β₁⁰ = 6.82 and log β⁰₂ = 10.6. Formation constants of these species appropriate to 0.7 molar ionic strength and 25°C are log β_H ～- 1, log β₁ = 5.73, log β₂ = 9.3. Our results indicate that the inorganic speciation scheme of Cu(II) in seawater is dominated by CuCO₃⁰ and that the ternary species, CuCO₃OH^?, is of substantial importance.  相似文献   

On the chemistry of the keggin Al13 polymer: kinetics of proton-promoted decomposition     

《Geochimica et cosmochimica acta》1999,63(19-20):3069-3076

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The stability of palladium(II) hydroxide and hydroxy–chloride complexes: an experimental solubility study at 25–85°C and 1 bar     

《Geochimica et cosmochimica acta》1999,63(11-12):1751-1765

Solubility methods were employed to determine conditional equilibrium constants for the formation of hydroxide and mixed hydroxy–chloride complexes of Pd(II). Measurements were made over a temperature range of 25–85°C, a pH range from 0 to 12, and ionic strengths of 0.1, 0.2, 0.5 and 1.0 molal in both KCl and NaClO₄ media. Several speciation models were fit to the data using nonlinear regression, and the model yielding the best fit with the fewest number of species was accepted for each temperature and ionic strength. The conditional equilibrium constants were then fit to a function of ionic strength and temperature (including a Debye–Hückel term) to facilitate interpolation and extrapolation to infinite dilution. The following species were found to be important in KCl solutions: PdCl₄²⁻, PdCl₃(OH)²⁻, and Pd(OH)₂⁰. The relative proportions of the species are dependent on pH and ionic strength (chloride concentration). In perchlorate media the predominant species were Pd(OH)₃⁻, Pd(OH)₂⁰, PdOH⁺ and Pd²⁺, depending on pH. Conditional stability constants determined in this study agree well with those reported in previous work for the simple chloride and hydroxide complexes, but our results suggest that mixed complexes may be more important than previously thought, and that PdCl₃(OH)²⁻ may be the dominant species in seawater, followed by Pd(OH)₂⁰.  相似文献   

Sedimentary iron monosulfides: Kinetics and mechanism of formation     

Albert J Pyzik  Sheldon E Sommer 《Geochimica et cosmochimica acta》1981,45(5):687-698

The reaction between hydrous iron oxides and aqueous sulfide species was studied at estuarine conditions of pH, total sulfide, and ionic strength to determine the kinetics and formation mechanism of the initial iron sulfide. Total, dissolved and acid extractable sulfide, thiosulfate, sulfate, and elemental sulfur were determined by spectrophotometric methods. Polysulfides, S₄^2? and S₅^2?, were determined from ultraviolet absorbance measurements and equilibrium calculations, while product hydroxyl ion was determined from pH measurements and solution buffer capacity.Elemental sulfur, as free and polysulfide sulfur, was 86% of the sulfide oxidation products; the remainder was thiosulfate. Rate expressions for the reduction and precipitation reactions were determined from analysis of electron balance and acid extractable iron monosulfide vs time, respectively, by the initial rate method. The rate of iron reduction in moles/liter/minute was given by $\text{d(}\text{reduction}\text{Fe)}\text{dt}\text{= kS}{}_{\mathrm{t}}{}^{0.5}\text{(J}{}^{\mathrm{+}}\text{)}{}^{0.5}\text{A}{}_{\mathrm{FeOOH}}{}^1$ where S_t was the total dissolved sulfide concentration, (H⁺) the hydrogen ion activity, both in moles/ liter; and A_FeOOH the goethite specific surface area in square meters/liter. The rate constant, k, was 0.017 ± 0.002m^?2 min^?1. The rate of reduction was apparently determined by the rate of dissolution of the surface layer of ferrous hydroxide. The rate expression for the precipitation reaction was $\text{d(FeS)}\text{dt}\text{= kS}{}_{\mathrm{t}}{}^1\text{(H}{}^{\mathrm{+}}\text{)}{}^1\text{A}{}_{\mathrm{FeOOH}}{}^1$ where $\text{d(FeS)}\text{dt}$ was the rate of precipitation of acid extractable iron monosulfide in moles/liter/minute, and k = 82 ± 18 mol^?1l²m^?2 min^?1.A model is proposed with the following steps: protonation of goethite surface layer; exchange of bisulfide for hydroxide in the mobile layer; reduction of surface ferric ions of goethite by dissolved bisulfide species which produces ferrous hydroxide surface layer elemental sulfur and thiosulfate; dissolution of surface layer of ferrous hydroxide; and precipitation of dissolved ferrous specie and aqueous bisulfide ion.  相似文献   

Kinetic and thermodynamic factors controlling the distribution of SO₃²⁻ and Na⁺ in calcites and selected aragonites     

Eurybiades Busenberg  L. Niel Plummer 《Geochimica et cosmochimica acta》1985,49(3):713-725

Significant amounts of SO₄^2?, Na⁺, and OH^? are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO₄^2?. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na⁺, but very low concentrations of SO₄^2?. The SO₄^2? content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na⁺ and SO₄^2? increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO₄^2? beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO₄^2? is the same as that of aragonite. Na⁺ appears to have very little effect on the solubility product of calcites. The amounts of Na⁺ and SO₄^2? incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient ($\text{D}$) of SO₄^2? in calcite at 25.0°C and 0.50 molal NaCl is described by the equation $\text{D = k}{}_0\text{+ k}{}_1\text{R}$ where $\text{k}{}_0$ and $\text{k}{}_1$ are constants equal to $\text{6.16 × 10}{}^{\mathrm{?6}}$ and $\text{3.941 × 10}{}^{\mathrm{?6}}$, respectively, and $\text{R}$ is the rate of crystal growth of calcite in mg·min^?1·g^?1 of seed. The data on Na⁺ are consistent with the hypothesis that a significant amount of Na⁺ occupies interstitial positions in the calcite structure. The distribution of Na⁺ follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na⁺ distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na⁺ contents of calcites are not very accurate indicators of environmental salinities.  相似文献   

Dissociation constants for alkali earth and sodium borate ion pairs from 10 to 50°C     

E.J. Reardon 《Chemical Geology》1976,18(4):309-325

Potentiometric measurements in dilute sodium borate solutions with added alkali earth chlordie salts yield the following expressions for the dissociation constants of alkali earth borate ion pairs from 10 to 50°C:where T is in °K. Enthalpies for the dissociation reactions at 25°C are less than 1 kcal./mole for all the alkali earth borate ion pairs.Values for pK(NaH₂BO₃°) from 5 to 55°C computed from the experimental data of Owen and King are in good agreement with those determined potentiometrically. The average value from both methods is 0.22 ± 0.1 at 25°C.Application to seawater of computed pK's for MgH₂BO₃⁺, CaH₂BO₃⁺ and NaH₂BO₃⁰ yields an apparent dissociation constant for boric acid of 8.73 vs. 8.70 measured by Lyman, 8.68 by Buch and 8.73 by Byrne and Kester.  相似文献   

Use of Pitzer's equations to determine the media effect on the formation of lead chloro complexes     

Frank.J. Millero  Robert H. Byrne 《Geochimica et cosmochimica acta》1984,48(5):1145-1150

The spectrophotometric measurements of chloro complexes of lead in aqueous HCl, NaCl, MgCl₂ and CaCl₂ solutions at 25°C have been analyzed using Pitzer's specific interaction equations. Parameters for activity coefficients of the complexes PbCl⁺, PbCl₂⁰ and PbCl₃^? have been determined for the various media. Values of $\text{K}{}_1\text{= 30.0 ± 0.6}$, $\text{K}{}_2\text{= 106.7 ± 2.1}$ and $\text{K}{}_3\text{= 73.0 ± 1.5}$ were obtained for the cumulative formation constants. [$\text{Pb}{}^{\mathrm{2+}}\text{+ nCl}{}^{\mathrm{?}}\text{→ PbCl}{}_{\mathrm{n}}{}^{\mathrm{2?n}}\text{)}$]. These values are in reasonable agreement with literature data. The Pitzer parameters for the PbCl ion pairs in various media were used to calculate the speciation of Pb²⁺ in an artificial seawater solution.  相似文献   

Internal consistency of a water analysis and uncertainty of the calculated distribution of aqueous species at 25°C     

Enrique Merino 《Geochimica et cosmochimica acta》1979,43(9):1533-1542

Many water analyses contain more than the minimum number of analytical determinations needed to calculate the distribution of species at ~ 25°C. The speciation of a water that contains $\text{n}$ cations and ligands other than H⁺ and OH^? can be calculated if just $\text{n}$ analytical determinations are available. In the frequent case where $\text{n + 1}$ (or more) determinations are available, one can calculate from the speciation a value for the ($\text{n + 1}$)th variable. The comparison between this computed value and its analytical counterpart (not used in calculating the speciation) constitutes a test for internal consistency among the $\text{n + 1}$ determinations that make up the whole analysis.Application of this test requires knowing the uncertainties of the calculated speciation and of the value computed for the ($\text{n + 1}$)th variable from the speciation. Such uncertainties have been ignored in previous algorithms, but have been determined herein by a Monte Carlo method of error propagation which is very well suited to systems of nonlinear algebraic equations.By comparing the titration alkalinity against the alkalinity calculated from the speciation, several published analyses for which the cation/anion balance is < 3% can be shown to be internally inconsistent. Such analyses may be unsuitable for geochemical calculations (water/rock interaction, estimation of reservoir temperatures, etc.).Several existing speciation algorithms disregard the possibility that the analytical data used as input are internally inconsistent.  相似文献   

Exchange of marine sodium for calcium during chemical weathering in the Isle aux Morts River basin,Newfoundland     

Mary E. Thompson 《Geochimica et cosmochimica acta》1982,46(3):361-365

Seasalt corrections applied to major-ion data for the Isle aux Morts River, Newfoundland, using Cl^? as the seawater indicator species, produce numerous negative values of Na⁺ that occur chiefly in the winter, when the seasalt concentrations are high. The negative values of Na⁺ are accompanied by slightly higher than usual concentrations of Ca⁺⁺, suggesting an exchange reaction of the form: $\text{Ca}\text{silicate}\text{+ 2 Na}{}^{\mathrm{+}}\text{= Na}{}_2\text{silicate}\text{+ Ca}{}^{\mathrm{++}}$, that is driven by seasalt.That the river receives seasalt inputs of normal major-ion seawater composition is indicated by analysis of precipitation chemistry data for nearby coastal stations.  相似文献   

The effect of pressure on the solubility of minerals in water and seawater     

Frank J Millero 《Geochimica et cosmochimica acta》1982,46(1):11-22

The effect of presure on the solubility of minerals in water and seawater can be estimated from In where the volume (ΔV) and compressibility (ΔK) changes at atmospheric pressure (P = 0) are given by Values of the partial molal volume ($\text{V}\text{?}$) and compressibilty ($\text{K}\text{?}$) in water and seawater have been tabulated for some ions from 0 to 50°C. The compressibility change is quite large (~10 × 10^?3 cm³ bar^?1 mol^?1) for the solubility of most minerals. This large compressibility change accounts for the large differences observed between values of ΔV obtained from linear plots of In K_sp versus P and molal volume data (Macdonald and North, 1974; North, 1974). Calculated values of $\text{K}{}^{\mathrm{P}}{}_{\mathrm{sp}}\text{K}{}^{\mathrm{o}}{}_{\mathrm{sp}}$ for the solubility of CaCO₃, SrSO₄ and CaF₂ in water were found to be in good agreement with direct measurements (Macdonald and North, 1974). Similar calculations for the solubility of minerals in seawater are also in good agreement with direct measurements (Ingle, 1975) providing that the surface of the solid phase is not appreciably altered.  相似文献   

Estimate of the life time of superoxide in seawater     

《Geochimica et cosmochimica acta》1987,51(2):351-353

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Gibbsite solubility and thermodynamic properties of hydroxy-aluminum ions in aqueous solution at 25°C     

Howard M. May  Philip A. Helmke  Marion L. Jackson 《Geochimica et cosmochimica acta》1979,43(6):861-868

Solubility curves were determined for a synthetic gibbsite and a natural gibbsite (Minas Gerais, Brazil) from pH 4 to 9, in 0.2% gibbsite suspensions in 0.01 M NaNO₃ that were buffered by low concentrations of non-complexing buffer agents. Equilibrium solubility was approached from oversaturation (in suspensions spiked with Al(NO₃)₃ solution), and also from undersaturation in some synthetic gibbsite suspensions. Mononuclear Al ion concentrations and pH values were periodically determined. Within 1 month or less, data from over-and undersaturated suspensions of synthetic gibbsite converged to describe an equilibrium solubility curve. A downward shift of the solubility curve, beginning at pH 6.7, indicates that a phase more stable than gibbsite controls Al solubility in alkaline systems. Extrapolation of the initial portion of the high-pH side of the synthetic gibbsite solubility curve provides the first unified equilibrium experimental model of Al ion speciation in waters from pH 4 to 9.The significant mononuclear ion species at equilibrium with gibbsite are Al³⁺, AlOH²⁺, Al(OH)⁺₂ and Al(OH)^?₄, and their ion activity products are $\text{1K}{}_{50}\text{= 1.29 × 10}{}^8$, $\text{1K}{}_{\mathrm{s1}}\text{= 1.33 × 10}{}^3$, $\text{1K}{}_{\mathrm{s2}}\text{= 9.49 × 10}{}^{\mathrm{?3}}$ and $\text{1K}{}_{\mathrm{s4}}\text{= 8.94 × 10}{}^{\mathrm{?15}}$. The calculated standard Gibbs free energies of formation (ΔG°_f) for the synthetic gibbsite and the A1OH²⁺, Al(OH)⁺₂ and Al(OH)^?₄ ions are ?276.0, ?166.9, ?216.5 and ?313.5 kcal mol^?1, respectively. These ΔG°_f values are based on the recently revised ΔG°_f value for Al³⁺ (?117.0 ± 0.3 kcal mol_?1) and carry the same uncertainty. The ΔG°_f of the natural gibbsite is ?275.1 ± 0.4 kcal mol^?, which suggests that a range of ΔG°_f values can exist even for relatively simple natural minerals.  相似文献   

Complex formation in the ternary system Mg(II)-CO₂-H₂O     

Walter Riesen  Heinz Gamsjäger  Paul W. Schindler 《Geochimica et cosmochimica acta》1977,41(9):1193-1200

The carbonato and hydrogencarbonato complexes of Mg²⁺ were investigated at 25 and 50° in solutions of the constant ClO₄^? molality (3 M) consisting preponderantly of NaClO₄. The experimental data could be explained assuming the following equilibria: Mg²⁺ + CO_2B + H₂O ag MgHCO⁺₃ + H⁺, $\text{log}{}^1\text{β}{}_1\text{= ?7.64}{}_4\text{± 0.01}{}_7\text{(25°), ?7.46}{}_2\text{± 0.01}{}_1\text{(50°)}$, Mg²⁺ + 2 CO_2g + 2 H₂Oag Mg(HCO₃)⁰₂ ± 2 H⁺, $\text{log}{}^1\text{β}{}_2\text{= ?15.00 ± 0.14 (25°)}$, ?15.37 ± 0.39 (50°), Mg²⁺ + CO_2g + H₂Oag MgCO⁰₃ + 2 H⁺, $\text{log}{}^1\text{k}{}_1\text{= ?15.64 ± 0.06 (25°)}$,?15.23 ± 0.02 (50°), with the assumption γ_MgCO3⁰ = γ_Mg(HCO3)⁰2, ΔG⁰(I = 0) for the reaction MgCO⁰₃ + CO_2g + H₂O = Mg(HCO₃)⁰₂ was estimated to be ?3.9₁ ± 0.8₆ and 0.6 ± 2.4 kJ/mol at 25 and 50°C, respectively. The abundance of carbonate linked Mg(II) species in fresh water systems is discussed.  相似文献   

Revised values for the Gibbs free energy of formation of [Al(OH)_{4 aq}⁻], diaspore,boehmite and bayerite at 298.15 K and 1 bar,the thermodynamic properties of kaolinite to 800 K and 1 bar,and the heats of solution of several gibbsite samples     

Bruce S. Hemingway  Richard A. Robie  James A. Kittrick 《Geochimica et cosmochimica acta》1978,42(10):1533-1543

Solution calorimetric measurements compared with solubility determinations from the literature for the same samples of gibbsite have provided a direct thermochemical cycle through which the Gibbs free energy of formation of [Al(OH)_{4 aq}^?] can be determined. The Gibbs free energy of formation of [Al(OH)_{4 aq}^?] at 298.15 K is ?1305 ± 1 kJ/mol. These heat-of-solution results show no significant difference in the thermodynamic properties of gibbsite particles in the range from 50 to 0.05 μm.The Gibbs free energies of formation at 298.15 K and 1 bar pressure of diaspore, boehmite and bayerite are ?9210 ± 5.0, ?918.4 ± 2.1 and ?1153 ± 2 kJ/mol based upon the Gibbs free energy of [A1(OH)_{4 aq}^?] calculated in this paper and the acceptance of ?1582.2 ± 1.3 and ?1154.9 ± 1.2 kJ/mol for the Gibbs free energy of formation of corundum and gibbsite, respectively.Values for the Gibbs free energy formation of [Al(OH)_{2 aq}⁺] and [AlO_{2 aq}^?] were also calculated as ?914.2 ± 2.1 and ?830.9 ± 2.1 kJ/mol, respectively. The use of [AlC_{2 aq}^?] as a chemical species is discouraged.A revised Gibbs free energy of formation for [H₄SiO_4aq⁰] was recalculated from calorimetric data yielding a value of ?1307.5 ± 1.7 kJ/mol which is in good agreement with the results obtained from several solubility studies.Smoothed values for the thermodynamic functions C_P⁰, ($\text{H}{}_{\mathrm{T}}{}^0\text{- H}{}_{298}{}^0\text{)}\text{T}$, $\text{(}\text{G}{}_{\mathrm{T}}{}^0\text{- H}{}_{298}{}^0\text{)}\text{T}$, S_T⁰ - S₀⁰, $\text{ΔH}{}_{\mathrm{?,298}}{}^0$ kaolinite are listed at integral temperatures between 298.15 and 800 K. The heat capacity of kaolinite at temperatures between 250 and 800 K may be calculated from the following equation: C_P⁰ = 1430.26 ? 0.78850 T + 3.0340 × 10^?4T² ?1.85158 × 10^?4T²$\text{1}\text{2}\text{+ 8.3341 × 10}{}^6\text{T}{}^{\mathrm{?2}}$.The thermodynamic properties of most of the geologically important Al-bearing phases have been referenced to the same reference state for Al, namely gibbsite.  相似文献   

Hyperfiltration-induced fractionation of carbon isotopes     

《Geochimica et cosmochimica acta》1987,51(5):1121-1134

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Salting-out of methane in single-salt solutions at 25°C and below 800 psia     

Ronald K. Stoessell  Patricia A. Byrne 《Geochimica et cosmochimica acta》1982,46(8):1327-1332

Aqueous solubilities of methane at 25°C have been determined in single-salt solutions equilibrated with a CH₄ gas phase at 350, 550, and 750 psia. Measurements were made over a range of ionic strengths in NaCl, KCl, CaCl₂, MgCl₂, Na₂SO₄, K₂SO₄, MgSO₄, Na₂CO₃, K₂CO₃, NaHCO₃, and KHCO₃ aqueous solutions.At 25°C and constant pressure and methane fugacity, methane solubilities were largely controlled by the stoichiometric ionic strength, I, and the cation of the salt. Except for an increased salting-out due to HCO₃^?, the anion effect was relatively insignificant. Different but consistent solubility trends were followed in monovalent and divalent cation salt solutions as a function of I. Solubilities increased in salt solutions having a common anion in the following cation sequence: Na⁺ < K⁺ ? Ca²⁺ < Mg²⁺.The molal salting coefficient, k_m, for each salt was constant under the experimental conditions of the study, k_m is defined by $\text{log}\text{γ}\text{ch}{}_4\text{I}$ where $\text{γ}\text{ch}{}_4$, the molal activity coefficient, is the methane solubility ratio () measured at constant temperature, pressure, and CH₄ fugacity. Single-salt k_m values are as follows: 0.121, NaCl (4m); 0.121, Na₂SO₄ (1m); 0.118, Na₂CO₃ (1.5m); 0.146, NaHCO₃ (0.5m); 0.101, KCl (4m); 0.108, K₂SO₄ (0.5m); 0.111, K₂CO₃ (2m); 0.145, KHCO₃ (0.5m); 0.071, CaCl₂ (2m); 0.063, MgCl₂ (2m); and 0.066, MgSO₄ (1.5m) where the molalities in parentheses refer to the maximum salt concentrations used in this study.  相似文献   

Isotopic and geochemical evidence of regional-scale anisotropy and interconnectivity of an alluvial fan system,Cochabamba Valley,Bolivia     

《Applied Geochemistry》2001,16(9-10):1097-1114

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