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1.
Yonit Sembira-Nahum Alexander Apelblat Emanuel Manzurola 《Journal of solution chemistry》2008,37(3):391-401
Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes,
V
2,φ
(m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂
C
p
/∂
p)
T,m
. They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate
are present. 相似文献
2.
Simultaneous measurements with magnesium ion-selective and pH glass electrodes have been used for determination of the stability
constants of magnesium ions with various biologically relevant ligands by alkalimetric titration under physiological conditions
(37 ○C, I=0.15 mol⋅dm−3). New systems were investigated: magnesium with pyroglutamate, pyridoxine and HEPES, along with citrate, lactate, glycinate,
aspartate and glutamate. For comparison, calcium stability constants with the same ligands were determined similarly, using
calcium ion-selective and pH glass electrodes. Ligand protonation constants, necessary for the calculation of the metal complex
formation constants, were also determined. 相似文献
3.
Raphael da C. Cruz Rosana J. Martins Márcio J. E. de M. Cardoso Oswaldo E. Barcia 《Journal of solution chemistry》2009,38(8):957-981
Density measurements were made for binary aqueous solutions of polyethylene glycol at seven temperatures: 283.15, 288.15,
293.15, 298.15, 303.15, 308.15, and 313.15 K. Polyethylene glycol samples with nominal average molar masses of 3000 g⋅mol−1 (PEG 3000), 6000 g⋅mol−1 (PEG 6000), 10000 g⋅mol−1 (PEG 10000) and 20000 g⋅mol−1 (PEG 20000) were used. These results were used to determine the specific volumes of solutions with solute-to-solvent mass
ratios (mass of the solute/mass of the solvent) in the range 0.0546 to 1.4932 for PEG 3000, from 0.0553 to 1.4986 for PEG
6000, from 0.0552 to 1.2241 for PEG 10000, and from 0.0530 to 1.2264 for PEG 20000. The differences between the specific volume
of a solution and the specific volume of the pure solvent, at a given temperature, were represented by a virial-type equation
in terms of solute concentration. The first-order coefficient of the expansion is the partial specific volume of the solute
at infinite dilution. The higher-order coefficients are related to the contribution of pairs, triplets, and higher-order solute
aggregates, according to the Constant-Pressure Solution Theory. The functional dependence of the virial coefficients upon
temperature is discussed in terms of solute-solute and solute-solvent interactions. The effect of the PEG molar mass on the
partial specific volume of solute at infinite dilution, as well as the contributions of pairs of solute molecules to the solution
volume, are also investigated. The apparent specific volume, apparent specific expansibility, apparent specific expansibility
at infinite dilution and virial coefficients of the apparent specific expansibility are also presented. 相似文献
4.
5.
Density, speed of sound and refractive index of the imidazolium-based ionic liquids (ILs), 1-methyl-3-octylimidazolium chloride
[C8mim][Cl], 1-butyl-3-methylimidazolium methyl sulfate [C4mim][C1OSO3], and 1-butyl-3-methylimidazolium octyl sulfate [C4mim][C8OSO3], have been measured in the temperature range from 283.15 to 343.15 K. Experimental density and speed of sound have been
used to calculate the internal pressure p
i of the ILs. The p
i values were found to be higher than those of water and molecular organic liquids, but lower than those of classical molten
salts. We also calculated molar refraction R
M from the measured refractive index n
D in the temperature range from 288.15 to 343.15 K. Refractive indices of ILs were also higher than those of normal organic
liquids, but comparable to long-chain hydrocarbon organic solvents. The structure-property correlation of the ILs has been
discussed and the results have been compared to our earlier studies (Kumar in J. Solution Chem. 37:203–214, 2008). 相似文献
6.
The disaccharide isomaltose is produced via an enzymatic reaction and is adsorbed to BEA zeolite. This reaction integrated
adsorption can be achieved as fluidized bed as well as fixed bed. We investigated isotherms, adsorption enthalpies and sorption
kinetics of BEA zeolite and extrudates with a novel aluminum phosphate sintermatrix. These extrudates contain 50% (w/w) of
BEA 150 zeolites (Si/Al = 75) as primary crystals. BET-surface for extrudates is 245 m2⋅g−1 and 487 m2⋅g−1 for zeolite. Extrudates show a monomodal macropore structure with a maximum at 90 nm. All isotherms show a type I shape.
For lower equilibrium concentrations, which occur during the enzymatic reaction, Henry’s law is applied and compared to a
Langmuir model. Adsorption equilibrium constant K
i,L
calculated from Langmuir for extrudates at 4 °C is 64.7 mL⋅g−1 and more than twice as high as obtained from Henry’s law with K
i
is 26.8 mL⋅g−1. Adsorption on extrudates at 4 °C is much stronger than on zeolite crystals where the Henry coefficient K
i
is 17.1 mL⋅g−1. Adsorption enthalpy Δh
Ad calculated from van’t Hoff plot with the Henry equation is −44.3 kJ⋅mol−1 for extrudates and −29.6 kJ⋅mol−1 for zeolite crystals. Finally, the kinetics for ad- and desorption were calculated from the initial slope. The diffusion
rate for ad- and desorption on extrudates were in the same range while adsorption on zeolites is three orders of magnitudes
faster than desorption. 相似文献
7.
A homopolymer of methyl methacrylate (MMA) and its copolymer with styrene at different compositions were synthesized and characterized.
Viscosity measurements of the synthesized homopolymer and the copolymers in toluene solutions were performed at 313 K. Different
equations were used to calculate the intrinsic viscosity, viscometric constants values, and molecular weight of the synthesized
polymers. The values of intrinsic viscosity and viscosity average molecular weight obtained by the two methods (single point
determination and graphical extrapolation) were compared in order to verify the validity of the single point determination
for the polymers. Viscometric properties derived included the specific viscosity (it determines the contribution of the solute
to the viscosity of the solution), the reduced viscosity (that provides a measure of the polymer capacity for increasing the
solution viscosity), and the intrinsic viscosity. 相似文献
8.
The paper discusses the ground state properties and dynamics of monolayer films formed by atomic adsorbates on a square lattice,
being the (100) plane of a face centered cubic crystal. The vibrations of films ordered into the commensurate c(2×2) as well as into the recently discovered ordered phase exhibiting a distorted Archimedean tiling of the type (32.4.3.4) are considered. The dispersion relations and the densities of states are determined and discussed. 相似文献
9.
Apparent molar volumes V
φ,B of n-propylamine, n-butylamine, di-n-propylamine, di-n-butylamine, triethylamine, tri-n-propylamine, and tri-n-butylamine in 1,4-dioxane and in oxolane (tetrahydrofuran) have been determined at 303.15 K using a high-precision Anton
Paar vibrating-tube densimeter (model DMA 60/602). The limiting partial molar volumes
and limiting excess partial molar volumes
are analyzed and interpreted in terms of solute-solvent interactions and structural effects of the molecules.
Analyses were made of the contributions of specific interactions to the partial molar volumes of these primary, secondary
and tertiary amines in 1,4-dioxane and oxolane using the Terasawa model, scaled particle theory (SPT) and hard-sphere theory
(HST). The ERAS model has also been applied to estimate the apparent molar volumes and excess apparent molar volumes of alkylamine
solutions in 1,4-dioxane and oxolane. 相似文献
10.
Heats of solution, Δsol
H
m
, of L-cysteine, L-serine and L-asparagine amino acids have been measured at different concentrations of aqueous ethanol,
propanol and 2-propanol at 298.15 K using solvation calorimetry. These data are compared with the results reported earlier
for L-alanine in ethanol. The enthalpic coefficients, h
xy
, of the solute-organic cosolvent pair interaction in water have been obtained from the McMillan-Mayer approach and the data
have been interpreted in terms of various interactions and changes in solvent structure. 相似文献
11.
Zhongyong Zha Dingna Wang Wei Hong Li Liu Sai Zhou Xiaojie Feng Bing Qin Jianmei Wang Yi Yang Liang Du Dong Zhang Zhendong Fang Chuanqin Xia 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):257-262
This study aimed at influence of europium speciation on its accumulation in Brassica napus (CK) and over-expressing BnTR1 lines (OE), and the kinetics of Eu uptake were investigated. These results indicated that the uptake in the roots of OE was higher than that of CK at high concentrations of europium and even the enrichment in the roots of OE was as high as 20,000 mg/kg at 328.9 μΜ Eu, this suggested that OE might have better resistance to uranium than CK. The time kinetics in plants showed that there had the similar trend between CK and OE. The formation of Eu3+at pH 5 in deionized water was beneficial to plants enrichment Eu and carbonate could reduce the adsorption of Eu in two group and phosphate almost completely impress the adsorption of Eu in two group, but citric acid could enhance europium root-to-shoot translocation in two group. These results would help understanding the mechanism of Eu uptake in Brassica napus (CK) and over-expressing BnTR1 lines (OE), therefore properly developing efficient europium/americium phytoremediation. 相似文献
12.
Ertha Janine Lacerda de Medeiros Rita de Cássia Ramos do Egypto Queiroga Antônio Gouveia de Souza Angela Maria Tribuzy de M. Cordeiro Ariosvaldo Nunes de Medeiros Darklê Luiza de Souza Marta Suely Madruga 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1515-1521
Dairies add fat supplements to the diets of small ruminants to increase energy production and consequently the production and quality nutritional and sensorial of the milk. This study investigated the thermal and oxidative stability of babassu, castor, faveleira, and sesame oils by TG/DTA and PDSC. The profile of the fatty oils studied was determined by GC–MS as well as physicochemical characteristics. The thermogravimetric profile of the oils indicated that mass loss was caused by the decomposition or volatility of the triacylglycerides. Faveleira and sesame oils showed a high percentage of polyunsaturated fatty acids, especially C18:2. From a nutritional standpoint, unsaturated oils are more suitable supplements for animals because they promote biochemical changes beneficial to human health. 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.
To understand the thermodynamic characteristics of cationic surfactants in binary mixtures, the aggregation behavior of hexadecyltrimethylammonium
chloride (CTAC) has been investigated in ethylene glycol (EG) + water solvent mixtures at different temperatures and EG to
water ratios. The critical micelle concentration (CMC) and degree of counter ion bonding (β) were calculated from electrical conductivity measurements. An equilibrium model for micelle formation was applied to obtain
the thermodynamic parameters for micellization, including the standard Gibbs energies of micellization (DGmico)\Delta G_{\mathrm{mic}}^{\mathrm{o}}), standard enthalpies of micelle formation (DHmico)\Delta H_{\mathrm{mic}}^{\mathrm{o}}) and standard entropies of micellization (DSmico)\Delta S_{\mathrm{mic}}^{\mathrm{o}}). Our results show that DGmico\Delta G_{\mathrm{mic}}^{\mathrm{o}} is always negative and slightly dependent on temperature. The process of micellization is entropy driven in pure water, whereas
in EG + water mixtures the micellization is enthalpy driven. 相似文献
15.
Júlia Ričanyová Renata Gadzała-Kopciuch Katarina Reiffova Yaroslav Bazel Bogusław Buszewski 《Adsorption》2010,16(4-5):473-483
The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples. 相似文献
16.
Fluorescence emission spectroscopy have been used to investigate the effects of electrolytes on the excited state intramolecular
charge transfer (ICT) reaction in 4-(1-azetidinyl)benzonitrile (P4C) in very dilute to concentrated electrolyte solutions
of ethyl acetate (EA), acetonitrile (AN) and ethanol (EtOH). In the limit of very low electrolyte concentrations, the reaction
rate (=1/τ
rxn, τ
rxn being the reaction time) is found to decrease with increasing electrolyte concentration, the extent of decrease being the maximum in EA and the minimum in AN. At moderate
to higher electrolyte concentrations, however, the rate increases upon further addition of electrolyte. The observed non-monotonic
electrolyte concentration dependence of rate is believed to occur due to a novel interplay between friction and solvation
experienced by the photo-excited reactant in solution. Moreover, the long time decay constant and amplitude of the bi-exponential
decay of the time resolved fluorescence emission intensity also show a significant electrolyte concentration dependence which
corroborates the relevant steady-state results.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
17.
The apparent molar volumes, V
φ
, of two series of homologous aliphatic carboxylic acids, H(CH2)
n
COOH [n=0–5] and (CH2)
n
(COOH)2 [n=0–5], were determined in dilute aqueous solutions by density measurements at T=298.15 K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T=298.15 K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050≤m/(mol⋅kg−1)≤0.3000. Values of the apparent molar volumes of undissociated acids Vf(u)0V_{\phi (u)}^{0} were also calculated. The variation of Vf(u)0V_{\phi (u)}^{0} was determined as a function of the aliphatic chain length of the studied carboxylic acids. 相似文献
18.
K. P. Singh Harshit Agarwal Vivek Kumar Shukla Isht Vibhu Manisha Gupta J. P. Shuka 《Journal of solution chemistry》2010,39(11):1749-1762
Measurements of the ultrasonic velocity (u), density (ρ) and refractive index (n) for binary mixtures of polyethylene glycol 250 dimethyl ether with 1-propanol and 1-butanol have been made at three temperatures
(T=293, 303 and 31 K) over the entire composition range in order to investigate the nature of intermolecular interactions between
the components of these liquid mixtures. Various excess thermodynamic properties such as the excess ultrasonic velocity (Δu), deviation in isentropic compressibility (Δk
S
), excess intermolecular free length (LfE)(L_{\mathrm{f}}^{\mathrm{E}}), excess acoustic impedance (Z
E), excess pseudo-Grüneisen parameter (Γ
E), and molar refraction deviation (ΔR
m) were calculated using experimental values of the ultrasonic velocity, density and refractive index and were then represented
with the Redlich-Kister polynomial equation. The observed excess deviation parameter values were explained on the basis of
the strength of intermolecular interactions between the components of the mixtures. Estimations of the refractive index and
ultrasonic velocity have also been made using various empirical relations and are discussed in terms of the average percentage
deviations (APD). 相似文献
19.
G. H. Zimmerman Philip W. Scott Wendy Greynolds Dmitriy Mayorov 《Journal of solution chemistry》2009,38(4):499-512
Electrical conductance measurements were made on dilute solutions of hydrochloric acid to 458 K and 1.4 MPa with a flow instrument.
These measurements agree well with those of previous authors. The conductance theory of Fuoss and Hsia as given by Fernandez-Prini
(FHFP), was fit to these measurements. It was found that this theory adequately described the present results with a single
parameter, the limiting conductance at infinite dilution Λ°(HCl). Within their estimated accuracy, reported literature results of Λ°(HCl) between 264.15 and 579 K and high pressures were found to be represented by a five-parameter equation that was a function
of the solvent viscosity, temperature and pressure. This equation along with the FHFP theory permits accurate calculation
of the conductance of dilute hydrochloric acid solutions at high temperatures and pressures.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
20.
Evgeniy V. Ivanov 《Journal of solution chemistry》2010,39(3):343-354
Densities of aqueous solutions of tetramethyl-bis-urea (TMbU) with solute mole fractions ranging up to 7.0×10−2 have been measured with an uncertainty of 1.5×10−5 g⋅cm−3, at 278.15, 298.15, 318.15, and 338.15 K using a vibrating-tube densimeter. The partial molar volumes and expansibilities
of TMbU (down to the infinite dilution) and water have been computed. The effects of solute concentration and temperature on the
volume packing changes, caused by dissolution (and hydration) of TMbU in an aqueous medium, have been considered. 相似文献