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1.
Viscosities and densities of sucrose in aqueous alkali metal halide solutions of different concentrations in the temperature
range 293.5 to 313.15 K have been measured. Partial molar volumes at infinite dilution (V
2
0
) of sucrose determined from apparent molar volume (φ
v
) have been utilized to estimate partial molar volumes of transfer (V
2,tr
0
) for sucrose from water to alkali metal halide solutions. The viscosity data of alkali metal halides in purely aqueous solutions
and in the presence of sucrose at different temperatures (293.15, 303.15 and 313.5 K) have been analysed by the Jones-Dole
equation. The nature and magnitude of solute-solvent and solute-solute interactions have been discussed in terms of the values
of limiting apparent molar volume (φ
v
0
), slope (S
v
) and coefficients of the Jones-Dole equation. The structure-making and structure-breaking capacities of alkali metal halides
in pure aqueous solutions and in the presence of sucrose have been ascertained from temperature dependence ofφ
v
0
. 相似文献
2.
The adsorption of dibenzothiophene (DBT) in hexadecane onto NaY zeolite has been studied by performing equilibrium and kinetic
adsorption experiments. The influence of several variables such as contact time, initial concentration of DBT and temperature
on the adsorption has been investigated. The results show that the isothermal equilibrium can be represented by the Langmuir
equation. The maximum adsorption capacity at different temperatures and the corresponding Langmuir constant (K
L
) have been deduced. The thermodynamic parameters (ΔG
0,ΔH
0,ΔS
0) for the adsorption of DBT have also been calculated from the temperature dependence of K
L
using the van’t Hoff equation. The value of ΔH
0,ΔS
0 are found to be −30.3 kJ mol−1 and −33.2 J mol−1 K−1 respectively. The adsorption is spontaneous and exothermic. The kinetics for the adsorption process can be described by either
the Langmuir model or a pseudo-second-order model. It is found that the adsorption capacity and the initial rate of adsorption
are dependent on contact time, temperature and the initial DBT concentration. The low apparent activation energy (12.4 kJ mol−1) indicates that adsorption has a low potential barrier suggesting a mass transfer controlled process. In addition, the competitive
adsorption between DBT, naphthalene and quinoline on NaY was also investigated. 相似文献
3.
Boris N. Afanasyev Yulia P. Akulova Maria M. Kotlyar 《Journal of Solid State Electrochemistry》1997,1(1):68-76
The function Δ(ΔG
A
0), which is the difference of Gibbs energies characterizing surface-active substance (surfactant, SAS) adsorption at metal/solution
and air/solution surfaces, has been introduced. The equation connecting the function Δ(ΔG
A
0) with SAS ionization potential has been obtained using the elementary theory of donor-acceptor interactions. Published experimental
data on SAS adsorption at mercury, bismuth and gold have been used for Δ(ΔG
A
0) calculation. The dependence of Δ(ΔG
A
0) on ionization potentials can be described by an equation derived in this work. It has been demonstrated that the value of
the hydrophilicity of gold is much higher than the values for mercury and bismuth. The lifetime of SAS molecules at a metal
surface has been estimated. The question of the possibility of theoretica
l estimation of standard energies ΔG
A
0 characterizing SAS adsorption at a metal/solution surface has been discussed.
Received: 9 December 1996 / Accepted: 13 January 1997 相似文献
4.
The determination of arsenic and selenium in standard reference materials using sector field ICP-MS in high resolution mode 总被引:2,自引:0,他引:2
Ashley T. Townsend 《Fresenius' Journal of Analytical Chemistry》1999,364(6):521-526
Sector field ICP-MS was used to analyse As and Se in a range of standard reference materials (NIST 1643d Water, NIST 1573a
Tomato Leaves, NIST 1566a Oyster Tissue, NIST 2704 Buffalo River Sediment and Bio-Rad Reference Urine Level 2). A spectral
resolution of m/Δm = 7500 enabled 75As and 77Se to be separated from problematic ArCl interferences. Following microwave acid digestion, solid samples were typically diluted
1 + 99 prior to analysis, while the urine sample was diluted 1 + 9. The water sample was analysed undiluted and diluted 1
+ 9. Despite near baseline spectral separation, 75As and 77Se were still found to be influenced by ArCl at high Cl concentrations, the effect being most pronounced for 77Se. When necessary 82Se was also monitored to determine the accuracy of the 77Se results. Detection limits (LOD, based on 3σ of 10 replicates) for 75As, 77Se and 82Se in ultra-pure water, 1% (w/w) HNO3 and 1% (w/w) HCl were ∼ 0.1, ∼ 0.2 and ∼ 0.5 ng g–1, respectively. Although signal intensities when using high resolution were ∼ 1% of that found when using low resolution mode
(m/Δm = 300), measured As concentrations and certified values were found to agree to within ± 11% for all samples analysed.
The concentration of Se in NIST 1566a Oyster Tissue, NIST 2704 Buffalo River Sediment and Bio-Rad Reference Urine were found
to be in agreement with certified values to within ± 15– 20%, as measured by 77Se. However, closer agreement (± 5%) was found when these samples were analysed using 82Se. The Se concentration in NIST 1643d Water was found to agree to within ± 5% of the certified value (depending on dilution
factor). Due to the low concentration of Se in NIST 1573a Tomato Leaves, quantitation was not possible (below LOQ, 10σ). As
a consequence of the lower ion transmission when using resolution 7500, analytical precisions were found to be elevated over
that normally observed using low resolution mode, typically ± 5–20% (depending on analyte concentration and isotopic abundance).
Received: 28 December 1998 / Accepted: 9 February 1999 相似文献
5.
The molar conductivities (Λ) of solutions of n-tetrabutylammonium tetraphenylborate (NBu4BPh4) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed
using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum’s pairing distance, and the limiting molar conductivities (Λo) and the association equilibrium constants (K
A) have been derived. The limiting ion conductivities (λ_±o) have been evaluated according to the method of Krumgalz. The λ+
o values have been compared with λ+
o values calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (Δ G
A
o), enthalpy (Δ H
A
o) and entropy (Δ S
A
o) for the process of ion-pair formation as well as the activation energy of the ionic movement (ΔH
∗) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions. 相似文献
6.
M. A. V. Ribeiro da Silva C. P. F. Santos M. J. S. Monte C. A. D. Sousa 《Journal of Thermal Analysis and Calorimetry》2006,83(3):533-539
The
standard (p0=0.1
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.0±1.7), – (350.1±2.7) and – (377.3±2.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.9±1.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.3±1.3), (91.0±1.2) and (98.2±1.4)
kJ mol–1.
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure. 相似文献
7.
G. Rhoderick Pamela Chu Eric Dolin Jerry Marks Touche Howard Mark Lytle L. McKenzie Don Altman 《Analytical and bioanalytical chemistry》2001,370(7):828-833
An EPA Voluntary Aluminum Industrial Partnership (VAIP) program has been formed to help US primary producers focus on reducing
the emissions of two perfluorocarbons (PFCs), tetrafluoromethane (CF4) and hexafluoroethane (C2F6), during the production of aluminum. To ensure comparability of measurements over space and time, traceability to national
sources was desirable. Hence, the EPA approached the NIST to develop a suite of primary standards to cover a mole fraction
(concentration) range of 0.1 to 1400 μmol mol–1 for CF4 and 0.01 to 150 μmol mol–1 of C2F6. A total of eight gravimetric PFC gas standards were prepared with relative expanded uncertainties of ≤ 0.52% (≈95% confidence
level). These primary standards were ultimately used to assign values to a series of secondary gas standards at three mole-fraction
levels with relative expanded uncertainties ranging from ± 0.7% to 5.3% (≈95% confidence level). This series of secondary
standards was used within the aluminum industry to calibrate instruments used to make emission measurements. Assignment of
values to the secondary standards was performed by use of gas chromatography with flame-ionization detection (GC–FID) and
Fourier transform infrared spectrometry (FTIR). Real time pot-line and stack samples from a local aluminum plant were also
obtained and sub-samples sent to each participating facility for analysis. The data generated from each facility were sent
to NIST for analysis. The maximum difference between the NIST and individual facilities’ values for the same sub-sample was
± 26%.
Received: 19 January 2001 / Revised: 27 March 2001 / Accepted: 6 April 2001 相似文献
8.
The densities and speeds of sound for binary mixtures containing the solute ionic liquid (IL) methyltrioctylammonium bis(trifluoromethylsulfonyl)imide
([MOA]+[Tf2N]−), solute/solvent methanol, and solvent methyl acetate have been measured at 298.15, 303.15, 308.15 and 313.15 K at atmospheric
pressure. The binary mixtures studied are ([MOA]+[Tf2N]− + methyl acetate or methanol), and (methanol + methyl acetate). The apparent molar volume, V
φ
and the apparent molar isentropic compressibility, k
φ
, have been evaluated from the experimental density and speed of sound data, respectively. The parameters of a Redlich–Mayer
type equation were fitted to the apparent molar volume and apparent molar isentropic compressibility data. The apparent molar
volume and apparent molar isentropic compressibility at infinite dilution, Vf0V_{\phi}^{0} and kf0k_{\phi}^{0}, respectively, of the binary solutions have also been calculated at each temperature. The infinite dilution apparent molar
volume indicates that intermolecular interactions for (IL + methyl acetate) mixtures are stronger than for (IL + methanol)
mixtures at all temperatures except at 298.15 K, and that Vf0V_{\phi}^{0} for the (IL + methyl acetate or methanol) binary systems increases with an increase in temperature. For the (methanol + methyl
acetate) system the intermolecular interaction are weaker and Vf0V_{\phi}^{0} also increases with an increase in temperature. Values of the infinite dilution apparent molar expansibility, Ef0E_{\phi}^{0}, indicate that the interaction between (IL + methyl acetate) is greater than for (IL + methanol) and (methanol + methyl acetate). 相似文献
9.
Cezar A. Bizzi Joaquim A. Nóbrega Juliano S. Barin Jussiane S.S. Oliveira Lucas Schmidt Paola A. Mello Erico M.M. Flores 《Analytica chimica acta》2014
The present work evaluates the influence of vessel cooling simultaneously to microwave-assisted digestion performed in a closed system with diluted HNO3 under O2 pressure. The effect of outside air flow-rates (60–190 m3 h−1) used for cooling of digestion vessels was evaluated. An improvement in digestion efficiency caused by the reduction of HNO3 partial pressure was observed when using higher air flow-rate (190 m3 h−1), decreasing the residual carbon content for whole milk powder from 21.7 to 9.3% (lowest and highest air flow-rate, respectively). The use of high air flow-rate outside the digestion vessel resulted in a higher temperature gradient between liquid and gas phases inside the digestion vessel and improved the efficiency of sample digestion. Since a more pronounced temperature gradient was obtained, it contributed for increasing the condensation rate and thus allowed a reduction in the HNO3 partial pressure of the digestion vessel, which improved the regeneration of HNO3. An air flow-rate of 190 m3 h−1 was selected for digestion of animal fat, bovine liver, ground soybean, non fat milk powder, oregano leaves, potato starch and whole milk powder samples, and a standard reference material of apple leaves (NIST 1515), bovine liver (NIST 1577) and whole milk powder (NIST 8435) for further metals determination by inductively coupled plasma atomic emission spectroscopy (ICP-OES). Results were in agreement with certified values and no interferences caused by matrix effects during the determination step were observed. 相似文献
10.
The effect of cosolvent on micellization of hexadecyltrimethyl ammonium bromide (CTAB) in aqueous solutions was studied. The
conductivity of a mixture (cosolvent + water) as function of CTAB concentration was measured at different temperatures. Ethylene
glycol and ethanol were used as a cosolvent. The conductivity data were used to determine the critical micelle concentration
(CMC) and the effective degree of counterion dissociation of micelle in the temperature range 303.2 to 313.2 K. In all the
cases studied, a linear relationship between log([CMC]mix/mol dm−3) and the mass fraction of cosolvent in solvent mixture has been observed. The free energy (ΔG
mic
0
), enthalpy (ΔH
mic
0
), and entropy (ΔS
mic
0
) of micellization were determined using the temperature dependence of CMC. The dependence of these thermodynamic parameters
on solvent composition was determined. The standard free energy of micellization was found to be negative in all cases and
becomes less negative as the cosolvent content increases. The enthalpy and entropy of micellization are independent of temperature
in pure water, while ΔH
mic
0
and ΔS
mic
0
decrease dramatically with temperature in mixed cosolvents. Furthermore, the entropic contribution is larger than the enthalpic
one in pure water, while in the mixed solvents, the enthalpic contribution predominates.
The text was submitted by the authors in English. 相似文献
11.
The viscosity of five (0.1240, 0.2378, 0.4645, 0.9440, and 2.2310 mol⋅kg−1) binary aqueous KBr solutions have been measured with a capillary flow technique. Measurements were made at pressures up
to 30 MPa for the temperature range 298 to 577 K. The total uncertainties of the viscosity, pressure, temperature, and composition
measurements were estimated to be less than 1.6%, 0.05%, 15 mK, and 0.02%, respectively. The temperature and pressure coefficients
of the viscosity of KBr(aq) were studied as a function of molality and temperature. The measured viscosities were compared
with data, predictions and correlations previously reported in the literature. The viscosity data were used to accurately
calculate the physical-meaningful parameters (viscosity A- and B-coefficients) of the extended Jones-Dole equation for the relative viscosity (η/η
0). Various theoretical models {absolute rate theory, Tammann-Tait-Gibson (TTG) model, and extended Einstein model} were used
to accurately represent the measured viscosities. Values of hydrodynamic molar volume V
k
(effective rigid molar volume of the salt) were calculated using the present experimental data. The high-pressure viscosity
measurements were used to test the predictive capability of the TTG model. 相似文献
12.
James Chung Wah Lam Yiu Chung Yip Wai Fong Tong 《Accreditation and quality assurance》2008,13(6):311-319
A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) has been used for determination of lead in plant materials
using isotope-dilution inductively coupled plasma mass spectrometry. The accuracy of the method was demonstrated by analysis
of a matrix certified reference material, NIST SRM 1547 Peach Leaves. Specific instrumental parameters of Q-ICP-MS, including
isotope analysis mode, integration time per point, number of points per mass, and number of measurements, were optimized to
obtain the best measurement precision. The precision (expressed as relative standard deviation) associated with replicate
measurement of the 208Pb/206Pb isotope ratio and its mass-bias correction factor was <0.2%. Following “Example A7” of the Eurachem/CITAC Guide, the relative
expanded uncertainty, U
rel, (coverage factor k = 2) was found to be ±1.1%, which fulfilled the target value of ±2% maximum and was lower than the uncertainty of ±3.4% reported
by NIST based on isotope-dilution thermal ionization mass spectrometry. Sample recovery of 99% was obtained. 相似文献
13.
The Hg-, Cd- and UO2-targets bombarded by protons have been treated using the sublimation and evaporation techniques. The Hg and Cd nuclei have
been separated from non-isotopic products by distillation in the hydrogen stream. The separation of the groups of Re, Os,
Ir, Mo, Tc and Ru oxides has been carried out in the air stream. No monotonic temperature dependence of the Tl, Ru, Mo, Tc,
Te, Pb and Po release has been observed in the oxidation of the UO2-ceramics in the air stream. The values of (−ΔH
a
0
) of volatile products adsorbed on quartz have been determined from the chromatographic data. The relation between the adsorption
heat (−ΔH
a
0
) and the standard sublimation heat (ΔH
298
0
subl.) has been found to be linear, i.e. −ΔH
a
0
=(4.04±1.97)+(0.69±0.04)ΔH
298
0
(subl.). As an example of the thermochromatographic generator of isotopes, the separation of99Mo to99mTc has been investigated.
相似文献
14.
Kelei Zhuo Qiufen Zhang Xiaopeng Xuan Hucheng Zhang Jianji Wang 《Frontiers of Chemistry in China》2007,2(2):193-198
Densities have been measured for Glucose + HCl +Water at 10-degree intervals from 278.15 to 318.15 K. The apparent molar volumes
(V
Φ,G) and standard partial molar volumes (V
Φ,G
0
) for Glucose in aqueous solution of 0.2, 0.4, 0.7, 1.1, 1.6, 2.1 mol·kg−1 HCl have been calculated as well as volumetric interaction parameters (V
EG) for Glucose — HCl in water and standard partial molar expansion coefficients (∂V
Φ,G
0
/ ∂T)p. Results show that (1) the apparent molar volume for Glucose in aqueous HCl solutions increases lineally with increasing
molality of Glucose and HCl; (2) V
Φ,G/0 for Glucose in aqueous HCl solutions increases lineally with increasing molality of HCl; (3) the volumetric interaction parameters
for Glucose — HCl pair in water are small positive and vary slightly with temperature; (4) the relation between V
Φ,G
0
and temperature exists as V
Φ,G
0
= a
0 + a
1(T − 273.15 K)2/3; (5) values of (∂V
Φ,G
0
/ ∂T)p are positive and increase as temperatures rise, and at given temperatures decrease slightly with increasing molalities of
HCl, indicating that the hydration of glucose decreases with increasing temperature and molality of HCl. These phenomena are
interpreted successfully by the structure interaction model.
Translated from Acta Chimica Sinica, 2006, 64(16): 1635–1641 (in Chinese) 相似文献
15.
Juan Mou Guoju Wang Wenxian Shi Shouwei Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(1):293-303
A novel γ-MnO2 hollow structure has been synthesized using a simple chemical reaction between MnSO4 and KMnO4 in aqueous solution without using any templates, surfactants, catalysts, calcination and hydrothermal processes. As an example
of potential applications, γ-MnO2 hollow structure was used as adsorbent in radionuclide 60Co(II) treatment, and showed an excellent ability. The effect of pH, contact time, ionic strength, humic acid (HA)/fulvic
acid (FA), and temperature was investigated using batch techniques. The results indicated that the sorption of 60Co(II) on γ-MnO2 was obviously dependent on pH values but independent of ionic strength. The presence of HA/FA enhanced the sorption of 60Co(II) on γ-MnO2 at low pH, whereas reduced 60Co(II) sorption on γ-MnO2 at high pH. The kinetic sorption of 60Co(II) on γ-MnO2 can be well fitted by the pseudo-second-order rate equation. The thermodynamic parameters (ΔH
0, ΔS
0, ΔG
0) were also calculated from the temperature dependent sorption isotherms, and the results suggested that the sorption of 60Co(II) on γ-MnO2 was a spontaneous and endothermic process. The sorption of 60Co(II) on γ-MnO2 was attributed to surface complexation rather than ion exchange. 相似文献
16.
N. K. Chaudhuri R. M. Sawant D. D. Sood 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):993-1011
Literature data on the stability constants of the fluoride complexes of the actinides in different oxidation states have been
compiled. In order to have a reasonable inter-comparison, the stability constant (β1) values obtained in diverse ionic strength media are converted to so called thermodynamic stability constants, β
1
0
using the DAVIES equation (a modification of Debye-Huckel equation). A correlation of the β
1
0
values with the fundamental properties of the actinide ions using various models available in the literature has been attempted.
Using the values of inonic radii and best available values of the stability constants of a large number of metal ions from
recent compilations a comparative study of the various models or relations available in the literature has been tried. For
metal ions in general, the semi-empirical relation recently developed by BROWN, SYLVA and ELLIS (BSE equation)_gives the best
correlation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification
in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally
determined values for actinides in different oxidation states is obtained in most of the cases. Further improvements in theoretical
relation as well as experimental data are required for better correlation. 相似文献
17.
N. B. Morozova P. P. Semyannikov S. V. Sysoev V. M. Grankin I. K. Igumenov 《Journal of Thermal Analysis and Calorimetry》2000,60(2):489-495
The temperature dependency of the saturated vapor pressure of Ir(acac)3 has been measured by the method of calibrated volume (MCV), the Knudsen method, the flow transpiration method, and the membrane
method. The thermodynamic parameters of phase transition of a crystal to gas were calculated using each of these methods,
and the following values of ΔH
T
0 (kJ mol−1) and ΔS
T
0 (J mol−1K−1), respectively, were obtained: MCV: 101.59, 156.70; Knudsen: 130.54, 224.40; Flow transpiration: 129.34, 212.23; Membrane:
95.45, 149.44
Coprocessing of obtaining data (MCV, flow transportation method and Knudsen method) at temperature ranges 110−200°C as also
conducted:ΔH
T
0 =127.9±2.1 (kJ mol−1 ); ΔS
T
0 =215.2±5.0 (J mol−1 K−1 ).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
J. Cabicar A. Gosman J. Plicka K. Štamberg 《Journal of Radioanalytical and Nuclear Chemistry》1983,80(1-2):71-80
The kinetics of isotope exchange in the238U(VI)-233U(VI)-strongly acidic cation exchanger Ostion KS system was studied in the temperature range 275–307K and for total uranium
concentration 2.94·10−4–1.75·10−2 mol·l−1 in UO2(NO3)2 solution. The experimental results were evaluated by means of the “two-film mass-transfer model” and by the use of Fick's
diffusion equations which have been proved more suitable for the system studied than McKay's equation. The influence of the
temperature was evaluated using the Arrhenius equation. The diffusion character of the process follows also from the value
of the activation energy (15.12 kJ·mol−1). In comparison with the UO
2
2+
↔H+ ion exchange6 the isotope exchange studied is faster and less dependent on temperature (the activation energy is substantially lower). 相似文献
19.
M. Fujiwara T. Okano T. -H. Nakashima A. A. Nakamura G. Sugihara 《Colloid and polymer science》1997,275(5):474-479
For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization
concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements
at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed
from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around
0 °C. The changes in the Gibbs energy, ΔG
0
m, enthalpy, ΔH
0
m, and entropy, ΔS
0
m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation.
Received: 28 August 1996 Accepted: 5 November 1996 相似文献
20.
Densities (ρ) and viscosities (η) of different strengths of magnesium sulphate (MgSO4) in varying proportions of formamide (FA) + ethylene glycol as mixed solvents were measured at room temperature. The experimental
values of ρ and η were used to calculate the values of the apparent molar volume, (φ1,), partial molar volume, (φ1,ℴ) at infinite dilution,A- andB-coefficients of the Jones-Dole equation and free energies of activation of viscous flow, (Δμ
1
0*
) and (Δμ
2
0*
), per mole of solvent and solute respectively. The behaviour of these parameters suggests strong ion-solvent interactions
in these systems and also that MgSO4 acts as structure-maker in FA + ethylene glycol mixed solvents. 相似文献