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1.
Clemente Bretti Francesco Crea Ottavia Giuffrè Silvio Sammartano 《Journal of solution chemistry》2008,37(2):183-201
Acid-base properties of some open-chain polyamines (ethylenediamine, diethylenetriamine, triethylenetetramine, spermine, tetraethylenepentamine
and pentaethylenehexamine) were studied at different ionic strengths in different aqueous ionic media at 25 °C. Measured were:
(i) the protonation constants of triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine from potentiometric
measurements [0 ≤I≤2.5 mol⋅L−1 in NaCl and (CH3)4NCl)]; and (ii) protonation enthalpies of ethylenediamine, diethylenetriamine, and spermine from calorimetric measurements
[NaCl: 0≤I≤1 mol⋅kg−1 for ethylenediamine, diethylenetriamine, 0 ≤I≤2 mol⋅kg−1 for spermine; (C2H5)4NI: 0≤I≤1 mol⋅kg−1; (CH3)4NCl: 0 ≤I≤2.5 mol⋅kg−1 only for diethylenetriamine]. Previously published protonation data for these polyamines in aqueous NaCl, (CH3)4NCl and (C2H5)4NI, were also examined. The general trends for the Gibbs energy and entropic contributions are, for ΔG: NaCl>(CH3)4NCl>(C2H5)4NI, and for TΔS: (C2H5)4NI>(CH3)4NCl>NaCl. This trend is more pronounced for the first protonation step. The dependences of these quantities on ionic strength
were modeled with the SIT (Specific ion Interaction Theory) equations, and differences found among the different media were
interpreted in terms of weak complex formation. 相似文献
2.
Clemente Bretti Concetta De Stefano Claudia Foti Ottavia Giuffrè Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1225-1245
Protonation constants of one thiocarboxylate (thioacetate) and four sulfur-containing carboxylates (2-methylthioacetate, thiolactate,
thiomalate, 3-mercaptopropionate) were determined by potentiometric measurements in a wide ionic strength range [0≤I≤5 mol⋅L−1 in NaCl and 0 ≤I≤3 mol⋅L−1 in (CH3)4NCl] at t=25 °C. For two of these ligands (2-methylthioacetate and thiolactate), the protonation enthalpies were also determined by
calorimetric measurements in NaCl ionic medium [0 ≤I≤5 mol⋅L−1] at t=25 °C. Individual UV spectra of the protonated and unprotonated 3-mercaptopropionate species, together with values of the
protonation constants, were obtained by spectrophotometric titrations. Results were analyzed in terms of their dependence
on the ionic medium by using different thermodynamic models [Debye-Hückel type, SIT (Specific ion Interaction Theory) and
Pitzer’s equations]. Differences among protonation constants obtained in different media were also interpreted in terms of
weak complex formation. 相似文献
3.
Clemente Bretti Concetta De Stefano Frank J. Millero Silvio Sammartano 《Journal of solution chemistry》2008,37(6):763-784
The protonation constants of ethylenedithiodiacetic, dithiodipropionic and dithiodibutyric acids were obtained from potentiometric
measurements in NaCl(aq) (I≤5 mol⋅L−1) and (CH3)4NCl(aq) (I≤3 mol⋅L−1) at t=25 °C. Their dependences on ionic strength were modeled by the SIT and Pitzer approaches. The activity coefficients of the
neutral species were obtained by solubility measurements. The literature values of the protonation constants of (HOOC)-(CH2)
n
-S-(CH2)
n
-(COOH) (n=1 to 3) and (HOOC)-(CH2)-S-(CH2)
n
-S-(CH2)-(COOH) (n=0 to 5) in NaCl(aq) and KCl(aq) (I≤3 mol⋅L−1) at 18 °C were also analyzed using the above approaches. Both the log 10
K
i
H and interaction parameter values follow simple linear trends as a function of certain structural characteristics of the ligands.
Examples of modeling these trends are reported.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
4.
The complexation of As(V) in aqueous solutions in the presence of iron(III) was investigated spectrophotometrically with both
variable and constant ionic strengths. The determined thermodynamic and stoichiometric formation constants of the FeHAsO4+ species are log10∘β = 9.21± 0.01 and log10Iβ (1.0mol⋅dm−3 NaClO4) = 7.78 ± 0.01, respectively. The numerical treatment of the obtained spectral data was performed with the SPECA program. The analysis required the consideration
of the hydrolysis of Fe(III) and the protonation of As(V) in the pH range studied. No significant hydrolysis was observed
because of the low pH values (pH < 2.5) involved. The stabilities of the solid Fe(III) arsenates was established by solubility
experiments. All of the solubility experiments were performed in aqueous NaClO4 solutions at constant ionic strength (1.0mol⋅dm−3) and at 25∘C. The experimental data were consistent with FeAsO4⋅2H2O being the solid phase (log10 ∘ Kso = −24.30± 0.08). The corresponding thermodynamic constants were computed by means of the Modified Bromley's Methodology (MBM)
that describes the variation of the activity coefficients of all of the ions involved in the complexation and precipitation
equilibria with the medium and ionic strength. Finally, the solid phase obtained in this work was also characterized by FT-IR
and FT-Raman spectroscopies, and the hydration of the solid iron arsenate was confirmed by X-ray diffraction data. 相似文献
5.
Lakshmi N. Roy Rabindra N. Roy Cole E. Denton Sean R. LeNoue Curtis A. Himes Sarah J. Richards Ashley N. Simon Chandra N. Roy Vikram S. Somal 《Journal of solution chemistry》2006,35(4):551-566
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of N-[tris(hydroxymethyl)methyl-3-amino]propanesulfonic acid (TAPS) have already been reported at 12 temperatures over the temperature range 5–55 ∘C, including 37 ∘C. This paper reports the results for the pH of five equimolal buffer solutions with compositions: (a) TAPS (0.03 mol⋅kg−1) + NaTAPS (0.03 mol⋅kg−1); (b) TAPS (0.04 mol⋅ kg−1) + NaTAPS (0.04 mol⋅kg−1); (c) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.05 mol⋅kg−1); (d) TAPS (0.06 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1); and (d) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.08 mol⋅kg−1). The remaining eight buffer solutions consist of saline media of the ionic strength I = 0.16 mol⋅kg−1, matching closely to that of the physiological sample. The compositions are: (f) TAPS (0.04 mol-kg−1) + NaTAPS (0.02 mol-kg−1) + NaCl (0.14 mol⋅kg−1); (g) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (h) TAPS (0.6 mol⋅kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (i) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); (j) TAPS (0.04 mol⋅ kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (k) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.05 mol⋅kg−1) + NaCl (0.11 mol⋅kg−1); (l) TAPS (0.06 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); and (m) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.08 mol⋅kg−1) + NaCl (0.08 mol⋅kg−1). These buffers are recommended as a pH standard for clinical measurements in the range of physiological application. Conventional pH values, designated as pH(s), for all 13 buffer solutions from 5 to 55 ∘C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 ∘C for buffer solutions, designated above as (b), (c), (d), (e), (j), (l), and (m); have been determined based on the difference in the values of the liquid junction potentials between the accepted phosphate standard and the buffer solutions under investigation. 相似文献
6.
Zhicheng Zhang Paul Gibson Sue B. Clark Guoxin Tian Pier Luigi Zanonato Linfeng Rao 《Journal of solution chemistry》2007,36(10):1187-1200
In acidic aqueous solutions, the protonation of gluconate is coupled with the lactonization of gluconic acid. With a decrease
of pC
H, two lactones (δ- and γ-) are sequentially formed. The δ-lactone forms more readily than the γ-lactone. In 0.1 mol⋅L−1 gluconate solutions, if pC
H>2.5 then only the δ-lactone is generated. When the pC
H is decreased below 2.0, formation of the γ-lactone is observed although the δ-lactone still predominates. In solutions with I=0.1 mol⋅L−1 NaClO4 and room temperature, the deprotonation constant of the carboxylic group was determined to be log 10
K
a=3.30±0.02 using the NMR technique, and the δ-lactonization constant obtained by batch potentiometric titrations was log 10
K
L=−(0.54±0.04). Using ESI-MS, the rate constants for the δ-lactonization and the reverse hydrolysis reaction at pC
H≈5.0 were estimated to be k
1=3.2×10−5 s−1 and k
−1=1.1×10−4 s−1, respectively. 相似文献
7.
Rabindra N. Roy Lakshmi N. Roy Shahaf Ashkenazi Joshua T. Wollen Craig D. Dunseth Michael S. Fuge Jared L. Durden Chandra N. Roy Hannah M. Hughes Brett T. Morris Kevin L. Cline 《Journal of solution chemistry》2009,38(4):449-458
The values of the second dissociation constant, pK
2, of N-(2-hydroxyethyl) piperazine-N′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including
37 °C. This paper reports the results for the pa
H of eight isotonic saline buffer solutions with an I=0.16 mol⋅kg−1 including compositions: (a) HEPES (0.01 mol⋅kg−1) + NaHEPES (0.01 mol⋅kg−1) + NaCl (0.15 mol⋅kg−1); (b) HEPES (0.02 mol⋅kg−1) + NaHEPES (0.02 mol⋅kg−1) + NaCl (0.14 mol⋅kg−1); (c) HEPES (0.03 mol⋅kg−1) + NaHEPES (0.03 mol⋅kg−1) + NaCl (0.13 mol⋅kg−1); (d) HEPES (0.04 mol⋅kg−1) + NaHEPES (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (e) HEPES (0.05 mol⋅kg−1) + NaHEPES (0.05 mol⋅kg−1) + NaCl (0.11 mol⋅kg−1); (f) HEPES (0.06 mol⋅kg−1) + NaHEPES (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); (g) HEPES (0.07 mol⋅kg−1) + NaHEPES (0.07 mol⋅kg−1) + NaCl (0.09 mol⋅kg−1); and (h) HEPES (0.08 mol⋅kg−1) + NaHEPES (0.08 mol⋅kg−1) + NaCl (0.08 mol⋅kg−1). Conventional pa
H values, for all eight buffer solutions from 5 to 55 °C, have been calculated. The operational pH values with liquid junction
corrections, at 25 and 37 °C have been determined based on the NBS/NIST standard between the physiological phosphate standard
and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH = 7.3 to 7.5
at I=0.16 mol⋅kg−1. 相似文献
8.
In this study, stoichiometric protonation constants of L-tyrosine, L-cysteine, L-tryptophane, L-lysine, and L-histidine, and
their methyl and ethyl esters in water and ethanol–water mixtures of 30, 50, and 70% ethanol (v/v), were determined potentiometrically
using a combined pH electrode system calibrated as the concentration of hydrogen ion. Titrations were performed at 25∘C and the ionic strength of the medium was maintained at 0.10 mol⋅L−1 using sodium chloride. Protonation constants were calculated by using the BEST computer program. The effect of solvent composition
on the protonation constants is discussed. The log10 K2 values of esters generally decreased with increasing ethanol content. However, the log10 K1 values of the esters of L-tyrosine, L-cysteine, and L-tryptophane were found to increase with increasing ethanol content
in contrast those of L-lysine and L-histidine esters. 相似文献
9.
Protonation constants of carbonate were determined in tetramethylammonium chloride (Me4NClaq 0.1 ≤ I/mol kg−1 ≤ 4) and tetraethylammonium iodide (Et4NIaq 0.1 ≤ I/mol kg−1 ≤ 1) by potentiometric ([H+]-glass electrode) measurements. Dependence of protonation constants on ionic strength was taken into account by modified specific ion interaction theory (SIT) and by Pitzer models. Literature data on the protonation of carbonate in NaClaq (0.1 ≤ I/mol kg−1 ≤ 6) were also critically analysed. Both protonation constants of carbonate follow the trend Et4NI > Me4NCl > NaCl. An ion pair formation model designed to take into account the different protonation behaviours of carbonate in different supporting electrolytes was also evaluated. 相似文献
10.
M. Jiménez-Reyes M. Solache-Ríos A. Rojas-Hernández 《Journal of solution chemistry》2006,35(2):201-214
The specific ion interaction theory (SIT) was applied to the first hydrolysis constants of Eu(III) and solubility product
of Eu(OH)3 in aqueous 2, 3 and 4 mol⋅dm−3 NaClO4 at 303.0 K, under CO2-free conditions. Diagrams of pEuaq versus pCH were constructed from solubilities obtained by a radiometric method, the solubility product log10 Ksp, Eu(OH)3I {Eu(OH)3(s)
Euaq3++ 3OHaq− } values were calculated from these diagrams and the results obtained are log10 Ksp,Eu(OH)3I = − 22.65 ± 0.29, −23.32 ± 0.33 and −23.70 ± 0.35 for ionic strengths of 2, 3 and 4 mol⋅dm−3 NaClO4, respectively. First hydrolysis constants {Euaq3++H2O
Eu(OH)(aq)2++H+ } were also determined in these media by pH titration and the values found are log10βEu,HI = − 8.19 ± 0.15, −7.90 ± 0.7 and −7.61 ± 0.01 for ionic strengths of 2, 3, and 4 mol⋅dm−3 NaClO4, respectively. Total solubilities were estimated taking into account the formation of both Eu3+ and Eu(OH)2+ (7.7 < pCH < 9) and the values found are: 1.4 × 10−6 mol⋅dm−3, 1.2 × 10−6 mol⋅dm−3 and 1.3 × 10−6 mol⋅dm−3, for ionic strengths of 2, 3 and 4 mol⋅dm−3 NaClO4, respectively. The limiting values at zero ionic strength were extrapolated by means of the SIT from the experimental results
of the present research together with some other published values. The results obtained are log10 Ksp, Eu(OH)3o = − 23.94 ± 0.51 (1.96 SD) and log10βEu,H0 = − 7.49 ± 0.15 (1.96 SD). 相似文献
11.
Kavosh Majlesi Mohammadreza Gholamhosseinzadeh Saghar Rezaienejad 《Journal of solution chemistry》2010,39(5):665-679
The main aim of this research is to study the complexation of molybdenum(VI) with methyliminodiacetic acid in NaClO4 aqueous solutions at pH = 6.00 and ionic strengths (0.1<I/mol⋅dm−3<1.0) at 25 °C by using potentiometric and UV spectrophotometric measurements in order to obtain thermodynamic stability constants
at I=0 mol⋅dm−3. A comparison with previous literature data was made for the stability constants, though few data were available. The stability
constants data have been analyzed and interpreted by using extended Debye-Hückel theory, specific ion interaction theory and
parabolic model. Finally it might be concluded that parabolic model applies better for this complexation reaction. 相似文献
12.
Jelena Miladinović Rozalija Ninković Milica Todorović Joseph A. Rard 《Journal of solution chemistry》2008,37(3):307-329
Isopiestic vapor-pressure measurements were made for {yMgCl2+(1−y)MgSO4}(aq) solutions with MgCl2 ionic strength fractions of y=(0,0.1997,0.3989,0.5992,0.8008, and 1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements
for the mixtures cover the ionic strength range I=0.9794 to 9.4318 mol⋅kg−1. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {xNa2SO4+(1−x)MgSO4}(aq) with the molality fraction x=0.5000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na2Mg(SO4)2⋅4H2O(cr). The total molalities, m
T=m(Na2SO4)+m(MgSO4), range from m
T=1.4479 to 4.4312 mol⋅kg−1 (I=5.0677 to 15.509 mol⋅kg−1), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation
of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {yMgCl2+(1−y)MgSO4}(aq) mixture results, were evaluated up to I=12.075 mol⋅kg−1 from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients
of {yMgCl2+(1−y)MgSO4}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate
the mixing parameters of the extended ion-interaction model. 相似文献
13.
Pasquale Crea Concetta De Stefano Mutsa Kambarami Frank J. Millero Virender K. Sharma 《Journal of solution chemistry》2008,37(9):1245-1259
The protonation constants for oxidized glutathione, H
i−1L(4−i+1)−, K
i
H=[H
i
L(4−i)−]/[H
i−1L(4−i+1)−][H+] i=1,2,…,6 have been measured at 5, 25 and 45 °C as a function of the ionic strength (0.1 to 5.4 mol⋅[kg(H2O)]−1) in NaCl solutions. The effect of ionic strength on the measured protonation constants has been used to determine the thermodynamic
values (K
i
H0) and the enthalpy (ΔH
i
) for the dissociation reaction using the SIT model and Pitzer equations. The SIT (ε) and Pitzer parameters (β
(0), β
(1) and C) for the dissociation products (L4−, HL3−, H2L2−, H3L−, H4L, H5L+, H6L2+) have been determined as a function of temperature. These results can be used to examine the effect of ionic strength and
temperature on glutathione in aqueous solutions with NaCl as the major component (body fluids, seawater and brines). 相似文献
14.
Halina Podsiadły 《Journal of solution chemistry》2008,37(9):1207-1215
Speciation in the aqueous V(III)–carnosine system has been determined from potentiometric and spectroscopic (UV-Vis absorption
and CD) data. Application of the Hyperquad program to the experimental potentiometric data indicates that under our experimental
conditions (I=0.5 mol⋅L−1 NaClO4, pH=2 to 6.5, and L/M>5) only ML2H4, ML2H3, ML2H2 and ML2H form. These potentiometric results prove that stable complexes form and, with use of the spectroscopic methods, the binding
sites are identified. 相似文献
15.
Melchor González-Dávila J. Magdalena Santana-Casiano Frank J. Millero 《Journal of solution chemistry》2006,35(1):95-111
The oxidation rates of nanomolar levels of Fe(II) in seawater (salinity S = 36.2) by mixtures of O2 and H2O2 has been measured as a function of pH (5.8–8.4) and temperature (3–35∘C). A competition exists for the oxidation of Fe(II)
in the presence of both O2 (μ mol⋅L−1 levels) and H2O2 (nmol⋅L−1 levels). A kinetic model has been applied to explain the experimental results that considers the interactions of Fe(II) with
the major ions in seawater. In the presence of both oxidants, the hydrolyzed Fe(II) species dominate the Fe(II) oxidation
process between pH 6 and 8.5. Over pH range 6.2–7.9, the FeOH+ species are the most active, whereas above pH 7.9, the Fe(OH)02 species are the most active at the levels of CO2−3 concentration present in seawater. The predicted Fe(II) oxidation rate at [Fe(II)]0 = 30nmol⋅L−1 and pH = 8.17 in the oxygen-saturated seawater with [H2O2]0 = 50nmol⋅L−1 (log 10 k = −2.24s−1) is in excellent agreement with the experimental value of log 10 k = −2.29s−1 ([H2O2]0 = 55nmol⋅L−1, pH = 8). 相似文献
16.
De Stefano C Milea D Pettignano A Sammartano S 《Analytical and bioanalytical chemistry》2003,376(7):1030-1040
The acid–base properties of phytic acid [myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H12Phy; Phy12–=phytate anion) were studied in aqueous solution by potentiometric measurements ([H+]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0<I mol L–13) and at t=25 °C. The protonation of phytate proved strongly dependent on both ionic medium and ionic strength. The protonation constants obtained in alkali metal chlorides are considerably lower than the corresponding ones obtained in a previous paper in tetraethylammonium iodide (Et4NI; e.g., at I=0.5 mol L–1, logK3H=11.7, 8.0, 9.1, and 9.1 in Et4NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et4NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton–metal–ligand complexes, MjHiPhy(12–i–j)–, (M+=Li+, Na+, K+), with j7 and i6, in the range 2.5pH10 (some measurements, at low ionic strength, were extended to pH=11). In particular, all the species formed are negatively charged: i+j–12=–5, –6. Very high formation percentages of M+–phytate species are observed in all the pH ranges investigated. The stability of alkali metal complexes follows the trend Li+Na+K+. Some measurements were also performed at constant ionic strength (I=0.5 mol L–1), using different mixtures of Et4NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal–proton–ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.Presented at SIMEC–02, Santiago de Compostela, 2–6 June 2002 相似文献
17.
The dynamical behavior of ethylene and ethane confined inside single-walled carbon nanotubes has been studied using Molecular
Dynamics and a fully atomistic force field. Simulations were conducted at 300 K in a broad range of molecular densities, 0.026 mol⋅L−1<ρ<15.751 mol⋅L−1(C2H4) and 0.011 mol⋅L−1<ρ<14.055 mol⋅L−1(C2H6), and were oriented towards the determination of bulk and confined phase self-diffusion coefficients. In the infinite time
limit, Fickian self-diffusion is the dominant mode of transport for the bulk fluids. Upon confinement, there is a density
threshold (ρ=5.5 mol⋅L−1) below which we observe a mixed mode of transport, with contributions from Fickian and ballistic diffusion. Nanotube topology
seems to have only a small influence on the confined fluids’ dynamical properties; instead density (loading capacity) assumes
the dominant role. In all cases studied and at a given density, the diffusivities of ethylene are larger than those of ethane,
although the difference is relatively minor. We note the collapse of self-diffusivities obtained from the bulk fluids and
confined phases into a unique single trend. These results suggest that it might be possible to infer dynamical properties
of confined fluids from the knowledge of their bulk phase densities.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
18.
Jaakko I. Partanen 《Journal of solution chemistry》2012,41(2):271-293
The Hückel equation used to correlate the experimental activities of dilute alkali metal chlorate, perchlorate or bromate
solutions up to a molality of about 1.5 mol⋅kg−1 contains two electrolyte-dependent parameters: B {that is related closely to the ion-size parameter (a
∗) in the Debye–Hückel equation} and b
1 (this parameter is the coefficient of the linear term with respect to the molality, which is related to hydration numbers
of the ions of the electrolyte). In more concentrated solutions up to 7 mol⋅kg−1, an extended Hückel equation was used, it contains additionally a quadratic term with respect to the molality, and the coefficient
of this term is the parameter b
2. Parameters for the Hückel equations were evaluated from isopiestic data for LiClO3, LiBrO3, LiClO4, NaClO3, NaBrO3, NaClO4, KClO3, and KBrO3. In these estimations, the Hückel parameters determined recently for NaCl solutions were used. The resulting parameter values
were tested with the vapor pressure and isopiestic data available in the literature for solutions of these salts. Most of
these data were reproduced within experimental error by means of the Hückel or extended Hückel equations, at least up to a
molality of 3.0 mol⋅kg−1, for all salts considered. Reliable activity and osmotic coefficients for solutions of these salts can, therefore, be calculated
by using the new Hückel equations, and they are tabulated here at rounded molalities. The activity and osmotic coefficients
obtained from these equations were compared to the values reported in several previous tabulations. 相似文献
19.
Dhanpat Rai Mikazu Yui Dean A. Moore Gregg J. Lumetta Kevin M. Rosso Yuanxian Xia Andrew R. Felmy Frances N. Skomurski 《Journal of solution chemistry》2008,37(12):1725-1746
No thermodynamic data for Th complexes with aqueous Si are available. To obtain such data, extensive studies on ThO2(am) solubility were carried out as functions of: (1) a wide range of aqueous silica concentrations (0.0004 to 0.14 mol⋅L−1) at fixed pH values of about 10, 11, 12, and 13; and (2) and variable pH (ranging from 10 to 13.3) at fixed aqueous Si concentrations
of about 0.006 mol⋅L−1 or 0.018 mol⋅L−1. The samples were equilibrated over long periods (ranging up to 487 days), and the data showed that steady-state concentrations
were reached in < 29 days. X-ray diffraction, FTIR, and Raman analyses of the equilibrated solid phases showed that the Th
solids were amorphous ThO2(am) containing some adsorbed Si. The solubility of ThO2(am) at pH values ranging from 10 to 13.3 at fixed 0.018 mol⋅L−1 aqueous Si concentrations decreases rapidly with an increase in pH, and increases dramatically with an increase in Si concentrations
beyond about 0.003 mol⋅L−1 at fixed pH values > 10. The data were interpreted using both the Pitzer and SIT models, and required only the inclusion
of one mixed-hydroxy-silica complex of Th [Th(OH)3(H3SiO4)32−]. Both models provided similar complexation constant values for the formation of this species. Density functional theory
calculations predict complexes of this stoichiometry, having six-fold coordination of the Th cation, to be structurally stable.
Predictions based on the fitted value of log 10
K
0=−18.5±0.7 for the ThO2(am) solubility reaction involving Th(OH)3(H3SiO4)32−[ThO2(am)+3H4SiO4+H2O↔Th(OH)3(H3SiO4)32−+2H+], along with the thermodynamic data for aqueous Si species reported in the literature, agreed closely with the extensive
experimental data and showed that under alkaline conditions aqueous Si makes very strong complexes with Th. 相似文献
20.
Dhanpat Rai Dean A. Moore Andrew R. Felmy Kevin M. Rosso Harvey BoltonJr. 《Journal of solution chemistry》2010,39(6):778-807
To determine the solubility product of PuPO4(cr, hyd.) and the complexation constants of Pu(III) with phosphate and EDTA, the solubility of PuPO4(cr, hyd.) was investigated as a function of: (1) time and pH (varied from 1.0 to 12.0), and at a fixed 0.00032 mol⋅L−1 phosphate concentration; (2) NaH2PO4 concentrations varying from 0.0001 mol⋅L−1 to 1.0 mol⋅L−1 and at a fixed pH of 2.5; (3) time and pH (varied from 1.3 to 13.0) at fixed concentrations of 0.00032 mol⋅L−1 phosphate and 0.0004 mol⋅L−1 or 0.002 mol⋅L−1 Na2H2EDTA; and (4) Na2H2EDTA concentrations varying from 0.00005 mol⋅L−1 to 0.0256 mol⋅L−1 at a fixed 0.00032 mol⋅L−1 phosphate concentration and at pH values of approximately 3.5, 10.6, and 12.6. A combination of solvent extraction and spectrophotometric
techniques confirmed that the use of hydroquinone and Na2S2O4 helped maintain the Pu as Pu(III). The solubility data were interpreted using the Pitzer and SIT models, and both provided
similar values for the solubility product of PuPO4(cr, hyd.) and for the formation constant of PuEDTA−. The log 10 of the solubility product of PuPO4(cr, hyd.) [PuPO4(cr, hyd.)
\rightleftarrows\rightleftarrows
Pu3++PO43-\mathrm{Pu}^{3+}+\mathrm{PO}_{4}^{3-}] was determined to be −(24.42±0.38). Pitzer modeling showed that phosphate interactions with Pu3+ were extremely weak and did not require any phosphate complexes [e.g., PuPO4(aq), PuH2PO42+\mathrm{PuH}_{2}\mathrm{PO}_{4}^{2+}, Pu(H2PO4)2+\mathrm{Pu(H}_{2}\mathrm{PO}_{4})_{2}^{+}, Pu(H2PO4)3(aq), and Pu(H2PO4)4-\mathrm{Pu(H}_{2}\mathrm{PO}_{4})_{4}^{-}] as proposed in existing literature, to explain the experimental solubility data. SIT modeling, however, required the inclusion
of PuH2PO42+\mathrm{PuH}_{2}\mathrm{PO}_{4}^{2+} to explain the data in high NaH2PO4 concentrations; this illustrates the differences one can expect when using these two different chemical models to interpret
the data. Of the Pu(III)-EDTA species, only PuEDTA− was needed to interpret the experimental data over a large range of pH values (1.3–12.9) and EDTA concentrations (0.00005–0.256 mol⋅L−1). Calculations based on density functional theory support the existence of PuEDTA− (with prospective stoichiometry as Pu(OH2)3EDTA−) as the chemically and structurally stable species. The log 10 value of the complexation constant for the formation of PuEDTA− [
Pu3++EDTA4-\rightleftarrows PuEDTA-\mathrm{Pu}^{3+}+\mathrm{EDTA}^{4-}\rightleftarrows \mathrm{PuEDTA}^{-}] determined in this study is −20.15±0.59. The data also showed that PuHEDTA(aq), Pu(EDTA)45-\mathrm{Pu(EDTA)}_{4}^{5-}, Pu(EDTA)(HEDTA)4−, Pu(EDTA)(H2EDTA)3−, and Pu(EDTA)(H3EDTA)2−, although reported in the literature, have no region of dominance in the experimental range of variables investigated in
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