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1.
The concentrations of dissolved silica species in electrolyte solutions were derived from the relative intensities of silica
species, obtained from FAB-MS measurements (fast atom bombardment mass spectrometry), and the total concentration of dissolved
silica. Generally, silica species in aqueous solutions form various complexes with cations such as sodium (Na+) or calcium (Ca2+), and it has been difficult to determine the concentration of each species. From the observed results from FAB-MS, the chemical
species of silica dissolved in lithium chloride (LiCl) and magnesium chloride (MgCl2) solutions do not include complexes with these cations, and thus Li+ and Mg2+ do not replace protons of the silanol groups in silica. Therefore, in LiCl and MgCl2 solutions, all of the simple structures of silicate species can be identified. The concentration of each silica species was
estimated on the basis of its mass spectra peak intensities and the total concentration of silica as determined by colorimetry.
This study yields the concentration of each silica species within small errors, whereas conventional methods (such as 29Si-NMR) have not yielded the concentrations of individual silica species. From these results, dimers and cyclic tetramers
are concluded to be the main species in silica solutions with concentrations of at most 0.1 to 0.2 μmol⋅dm−3. This tendency should also occur in NaCl and CaCl2 solutions, which are major electrolytes in natural waters. 相似文献
2.
When the sodium ion (Na+) concentration is increased above 0.5 mol-dm−3 (M), the concentrations of dissolved silica in aqueous sodium chloride (NaCl) and sodium nitrate (NaNO3) solutions decrease because of the salting out effect. On the other hand, the concentration of the dissolved silica in aqueous sodium sulfate (Na2SO4) solutions increases monotonously as the concentration of Na+ is increased above 0.5 M. The purpose of this study is to determine the reasons why the salting-out effect is not observed in Na2SO4 solutions. FAB-MS (Fast Atom Bombardment Mass Spectrometry) was used to sample directly the silica species dissolved in aqueous Na2SO4, NaCl, and NaNO3 solutions. In the FAB-MS spectra of these solutions, the peak intensity ratios of the linear tetramer to the cyclic tetramer largely increased for Na+ concentrations between (0.1 and 1) M. This shows that some characteristics of the Na2SO4 solutions are similar to those of the NaCl and NaNO3 solutions. In Na2SO4 solutions, however, when the concentration of Na+ is higher than 1 M, the peak intensity of the dimer is much higher than those of the other silicate complexes. In Na2SO4 solutions, the SO42− ion undergoes partial hydrolysis to form HSO−4 and OH− is produced. In particular, in the range where the concentration of SO42− is high, the pH of the solution increases slightly. This higher pH yields more dimers from the hydrolysis of silicate complexes. This increase in dimer production agrees with the observation that silica dissolves in sodium hydroxide (NaOH) solutions mainly as a dimer when the concentration of NaOH is less than 0.1 M. In Na2SO4 solutions at high concentrations, a salting-out effect is not observed for silica. This is due to the increase in the concentration of OH−, which accelerates the hydrolysis of silica and results in dimer formation. 相似文献
3.
The concentration dependent self-aggregation of 1,1′-diethyl-2,2′-carbocyanine chloride (pinacyanol chloride dye) in 7.5%
(v/v) ethanol + 92.5% water solution in the range of 10−6–10−3 mol⋅dm−3 has been investigated by quantitative UV/vis and derivative spectroscopy. Bands with maxima at 601, 546, 522, and 507 nm
could be attributed, respectively, to the monomer, a sandwich-type dimer, a vibronic overtone of the dimer, and a higher aggregate,
most probably a stacked trimeric form of the dye. Using the PeakFit program, the overlapping bands were separated and analyzed
for all concentrations studied. From the spectral fitting routine, extinction coefficients of 192,000, 156,000, and 282,000 cm−1⋅mol−1⋅dm3 were determined for the monomer, dimer and trimer respectively. 相似文献
4.
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
5.
Yizhak Marcus 《Journal of solution chemistry》2009,38(5):513-516
In concentrated salt solutions the average distances between the ions, d
av=1.1844⋅(∑ν
i
c
i
)−1/3 nm, are commensurate with the sizes of the solvated ions, so that no ‘bulk solvent’ remains. This is illustrated with two
saturated aqueous solutions, where 16.67 mol⋅dm−3 CsF at 75 °C has d
av(Cs–F)=0.368 nm and 14.54 mol⋅dm−3 LiI at 80 °C has d
av(Li–I)=0.385 nm. The minimal distance required for the bare ions (sum of their radii) are 0.303 nm for CsF and 0.289 nm for
LiI. Hence no water molecule, diameter 0.276 nm, can be fitted between the ions to form linear or slightly bent hydrogen bonds.
Some recent work ignoring such constraints, even in 3–6 mol⋅dm−3 solutions, is criticized on this account. 相似文献
6.
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
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.
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
9.
From vapor pressure osmometry data, the activity of water, osmotic coefficients and mean ionic activity coefficients of glycine
(m=0.006−3.2 mol⋅kg−1), L-histidine (m=0.005−0.23 mol⋅kg−1), L-histidine monohydrochloride (m=0.008−0.63 mol⋅kg−1), glutamic acid (m=0.004−0.05 mol⋅kg−1), sodium L-glutamate (m=0.007−0.6 mol⋅kg−1), and calcium L-glutamate (m=0.008−0.6 mol⋅kg−1) have been obtained in aqueous solutions at 298.15 and 310.15 K. The Pitzer equations and the mean spherical approximation
(MSA) are used for theoretical modeling. The results are supplied as reference thermodynamic material for the characterization
of more complex molecules such as proteins. 相似文献
10.
Highly concentrated alkaline gallate solutions with 0.23≤[Ga(III)]T≤2.32 mol⋅dm−3 and 1≤[NaOH]T≤15 mol⋅dm−3 have been prepared and investigated by Raman and 71Ga-NMR spectroscopy. Both the Raman and 71Ga-NMR spectra are consistent with the presence of only one Ga-bearing species in these solutions, the tetrahedral hydroxocomplex,
Ga(OH)4−. Contact ion pairs were found to cause variations in the Raman and 71Ga-NMR parameters that are at the edge of detectability. Other species that have been claimed to exist in the literature,
like higher hydroxo complexes (i.e., Ga(OH)63−) or the μ-oxo-bridged dimer (i.e., (OH)3Ga-O-(OH)32−), were not detected by these spectroscopic techniques. If such solution species exist at all, their concentrations are below
the detection limit of Raman and 71Ga-NMR spectroscopy. The behavior of gallium appears to be very similar to that of aluminium under identical conditions, except
that the dimeric species detected in aluminate solutions is undetectable in analogous gallates. 相似文献
11.
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
12.
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
this study. 相似文献
13.
Equilibrium constants for formation of a cobalt(II) complex with the bidentate ligand dopamine have been studied with spectrophotometric
methods in water + ethanol cosolvent systems at 15, 25, and 35 (±0.1) °C and an ionic strength of 0.2 mol⋅dm−3. The ionic strength was maintained using sodium chloride and a phosphate buffer. The stability constants of the complex and
the resulting Gibbs energy changes are obtained. The results are discussed in terms of the effect of solvent on protonation
and complexation. 相似文献
14.
Jadwiga Opydo 《Mikrochimica acta》2001,137(3-4):157-162
Necessary conditions were established for simultaneous nickel and cobalt determination in environmental samples, such as
oak wood and soil, based on cathodic adsorptive stripping voltammetry. Ni(II) and Co(II), complexed with dimethylglyoxime,
were determined using a hanging mercury drop electrode. Optimum conditions were found to be: accumulation time 90 s, accumulation
potential −0.80 V vs. SCE, supporting electrolyte 0.2 mol dm−3 ammonia-ammonium chloride buffer (pH = 9.4) + 0.05 mol dm−3 NaNO2 and dimethylglyoxime 2 × 10−4 mol dm−3. A linear current-concentration relationship was observed up to 7.51×10 −7 mol dm−3 for Ni(II) and 7.0 × 10−7 mol dm−3 for Co(II). Excess amounts of zinc(II) interfering with cobalt peaks were masked by complexation with EDTA. Wood and soils
were mineralized by applying a microwave digestion system, using the mixtures H2O2 + HNO3 or HNO3 + HF, respectively. The developed procedure was tested by analysing international reference materials (BCR 62 Olive Leaves
and GBW 08302 Tibet Soil). The developed procedure was used to determine pollution of oak stand with nickel and cobalt in
different regions of Poland.
Received August 10, 2000. Revision May 22, 2001. 相似文献
15.
Brahim Hacht 《Journal of solution chemistry》2008,37(2):155-163
Potentiometric titrations of aqueous acetic acid alone and in the presence of Ca(II) or Mg(II) ions have been carried out
under physiological conditions at the temperature 37 °C and ionic strength 0.15 mol⋅dm−3 (NaCl) at different ligand-to-metal ratios. Changes in pH were monitored with a glass electrode calibrated daily in terms
of the hydrogen ion concentrations. Titration data within the pH range 2.5 to 6.6 were analyzed to determine stability constants
using the SUPERQUAD program. Different combinations of complexes were considered during the calculation procedure for both
systems, but evidence was found only for mononuclear ML and ML2 species. Speciation calculations based on the corresponding constants were then used to simulate the species’ distributions. 相似文献
16.
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
17.
V. L. Lobachev G. P. Zimtseva E. S. Rudakov 《Theoretical and Experimental Chemistry》2005,41(5):302-309
It was found that nitrite anions are effective activators of hydrogen peroxide in the reaction with diethyl sulfide. The observed
kinetics are consistent with the proposed intermediate formation of peroxynitrous acid (ONOOH). The rate constants for the
reaction of diethyl sulfide Et2S with the acid ONOOH (k0 = 1.8⋅103 L/mol⋅s) and with the anion ONOO− (k− = 6⋅10−2 L/mol⋅s) are respectively 105 and three times higher than with hydrogen peroxide.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 290–295, September–October, 2005. 相似文献
18.
Abstract
The effect of sodium benzoate (SB) and sodium 4-(phenylamino)benzenesulfonate (SPABS) on the corrosion behavior of low carbon steel has been investigated using gravimetric method in the temperature range of 30–80 °C, velocity range of 1.44–2.02 m s−1 and concentration range of 6.94 × 10−4 to 4.16 × 10−3 mol dm−3 SB and 3.69 × 10−4 to 2.06 × 10−3 mol dm−3 SPABS. Optimization of temperature, fluid velocity, and inhibitors concentration has been made. The obtained results indicate that the inhibition efficiency (w IE %) at 1.56 m s−1 is not in excess of 81.5% at 4.16 × 10−3 mol dm−3 SB and 84.4% at 2.06 × 10−3 mol dm−3 SPABS. The inhibitive performance of these compounds showed an improvement with increasing concentration up to critical values of SB and SPABS; beyond these concentrations no further effectiveness is observed. These inhibitors retard the anodic dissolution of low carbon steel by protective layer bonding on the metal surface. The adsorption of SB and SPABS on the low carbon steel surface was found to obey the Freundlich isotherm model. The FT-IR spectroscopy was used to analyze the surface adsorbed film. 相似文献19.
Clemente Bretti Concetta De Stefano Claudia Foti Silvio Sammartano 《Journal of solution chemistry》2006,35(9):1227-1244
The protonation constants of phthalate were determined in aqueous NaCl (0.1 ≤ I ≤ 5,mol⋅L−1) and in aqueous Me4NCl (0.1 mol⋅L−1 ≤ I ≤ 3,mol⋅L−1) at t = 25,∘C. Experimental data were employed in conjunction with literature data from studies in different ionic media (Et4NI: 0 ≤ I ≤ 1,mol⋅L−1; NaClO4: 0.05 mol⋅L−1 ≤ I ≤ 2,mol⋅L−1)to study the dependence on ionic strength using different models, such as the SIT and Pitzer equations, and an Extended Debye-Hückel type equation. Experimental calorimetric data in NaCl and protonation constants at different temperatures in Et4NI (5 ≤ t ≤ 45∘C) and in NaClO4 (15 ≤ t ≤ 35 ∘C) were also used to study their dependence on temperature. Recommended equilibrium data are reported together with a short discussion of a prospective protocol for drawing these data. 相似文献
20.
Nancy J. Hess Odeta Qafoku Yuanxian Xia Dean A. Moore Andrew R. Felmy 《Journal of solution chemistry》2008,37(11):1471-1487
The room temperature solubility of amorphous, hydrous technetium(IV) oxide (TcO2⋅xH2O) was studied across a broad range of pH values extending from 1.5 to 12 and in oxalate concentrations from dilute (10−6 mol⋅kg−1) to complete saturation with respect to sodium bioxalate at lower pH values, and to saturation with respect to sodium oxalate
at higher pH values. The solubility was measured to very long equilibration times (i.e., as long a 1000 days or longer). The
thermodynamic modeling results show that the dominant species in solution must have at least one more hydroxyl moiety present
in the complex than proposed by previous investigators (e.g., TcO(OH)Ox− rather than TcO(Ox)(aq)). Inclusion of the single previously unidentified species TcO(OH)Ox− in our aqueous thermodynamic model explains a wider range of observed solubility data for TcO2⋅xH2O(am) in the presence of oxalate and over a broad range of pH values. Inclusion of this species is also supported by the recently
proposed thermodynamic data for the TcO(OH)+ hydrolysis species that indicates that this species is stable at pH values as low as one. 相似文献