共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Jaka Horvat Marija Bešter-Rogač Cveto Klofutar Darja Rudan-Tasic 《Journal of solution chemistry》2008,37(9):1329-1342
The viscosities of aqueous solutions of lithium, sodium, potassium, rubidium and caesium cyclohexylsulfamates were measured
at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity data were analyzed and interpreted in terms of the
Kaminsky equation, η
r=1+Ac
1/2+Bc+Dc
2. The viscosity A-coefficient was calculated from the Falkenhagen-Dole theory. The viscosity B-coefficients are positive and relatively large. Their temperature coefficient ∂
B/∂
T is negative or near zero for lithium and sodium salts whereas for potassium, rubidium and caesium salts it is positive. The
viscosity D-coefficient is positive. This was explained by the size of the ions, structural solute–solute interactions, hydrodynamic
effect, and by higher terms of the long-range Debye-Hückel type of forces. From the viscosity B-coefficients the thermodynamic functions of activation of viscous flow were calculated. The limiting partial molar Gibbs
energy of activation of viscous flow of the solute was divided into contributions due to solvent molecules and the solute
in the transition state. The activation energy of the solvent molecules was calculated using the limiting Gibbs energy of
activation for the conductance of the solute ions. The activation energy of the solvent molecules was then discussed in terms
of the nature of the alkali-metal ions and their influence on the structure of water. The limiting activation entropy and
enthalpy of the solute for activation of viscous flow were interpreted by ion-solvent bond formation or breaking in the transition
state of the solvent. The hydration numbers of the investigated electrolytes were calculated from the specific viscosity of
the solutions. 相似文献
3.
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
4.
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
5.
A. F. Fucaloro K. Dewey G. Fan K. Imuta D. Jensen M. Muranaka 《Journal of solution chemistry》2008,37(9):1289-1304
The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine,
at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil
and thymine are less than in pure water. 相似文献
6.
In this work, we examined the role of a non-ionic surfactant, Tween 20, on enzymatic hydrolysis of lignocelluloses. Delignified
lignocelluloses (pine wood chip) were used as model substrates. Effects of Tween 20 on adsorption/desorption onto/from lignocelluloses
with and without hydrolysis were evaluated respectively. Tween 20 lowered the non-biospecific adsorption of β-glucosidase and enhanced the bio-specific adsorption of cellulase. Tween 20 did not affect the liquid phase reaction (cellobiose
hydrolysis). However, for the solid surface reaction (cellulose hydrolysis), cellulose conversion for 72 hrs was increased
9–21% and 1–8.5% for samples with high lignin contents (PI) and low lignin contents (PIII) by injection of Tween 20 (0.024–0.24 mM),
respectively. Moreover, Tween 20 increased the cellulose conversion rate substantially. It is suggested that the increase
of cellulase amount adsorbed due to the increase of effective cellulose surface by Tween 20 contribute to the enhancement
of cellulose conversion. 相似文献
7.
David Reinhoudt 《Supramolecular chemistry》2016,28(5-6):342-350
AbstractDuring the Calix2015 conference that took place in Giardini Naxos in July of this year, the first C. David Gutsche Award for Calixarene Chemistry was awarded to one of the founders of the field, Professor Rocco Ungaro of the University of Parma. In this paper, Rocco Ungaro’s seminal contributions to the field are described. His collaborations with many other groups, his role in the European supramolecular chemistry community and his most important scientific results are briefly summarised. 相似文献
8.
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
9.
Complexes of copper(II) with a number of polyphosphate and polymetaphosphate anions have been studied in aqueous solutions
by potentiometric, spectroscopic and theoretical methods. Stability constants of the complexes have been determined as well
as their coordination modes. Results of the equilibrium studies provided evidence for the formation of ML, MHL and ML(OH)
x
type complexes with the ligands studied. The length of the polyphosphate chain was found to affect the oxygen atom charge
that is reflected in the stability constants of the ML type complexes. Moreover, the stability of the complex is also influenced
by the spatial arrangement of the phosphate groups in phosphates and metaphosphates. The spectral parameters observed for
certain complexes have permitted us to deduce the inner coordination sphere of the studied complexes. 相似文献
10.
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
11.
12.
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
13.
Nikos G. Tsierkezos 《Journal of solution chemistry》2008,37(10):1437-1448
The cyclic voltametric technique utilizing a platinum working electrode was applied for the investigation of the electrochemical
oxidation of bis(benzene)chromium(0), (C6H6)2Cr to bis(benzene)chromium(I), (C6H6)2Cr+ in diethyl ketone (DEK), N,N-dimethylformamide (DMF), and DEK/DMF binary mixtures containing n-tetrabutylammonium hexafluorophosphate (TBAPF6) as the supporting electrolyte at T=298.15 K. The half-wave potentials (E
1/2) of the (C6H6)2Cr+/0 redox couple in DEK, DMF and DEK/DMF binary mixtures, were determined. The variation of E
1/2 with the solvent composition was found to be almost linear. The E
1/2 results were analyzed in terms of the electron-donating power of the solvent medium. The diffusion coefficients, D, were calculated using the Randles-Sevcik equation. The kinetics of the electrode reaction were investigated through the
determination of the heterogeneous electron-transfer rate constants, k
s, according to the electrochemical rate equation proposed by Nicholson. Furthermore, the activation Gibbs energies for the
electron-transfer process (ΔG
≠) were also calculated. The results indicate that the redox couple (C6H6)2Cr+/0 exhibits an electrochemically reversible and diffusion-controlled process in all the investigated solvent media. 相似文献
14.
Enthalpies of dilution of N,N′-hexamethylenebisacetamide in water and aqueous alkali halide solutions at the concentration
of 0.150 mol⋅kg−1 (approximately the concentration of physiological saline) have been determined by isothermal titration microcalorimetry at
298.15 K. The enthalpic interaction coefficients in the solutions have been calculated according to the excess enthalpy concept
based on the calorimetric data. The values of enthalpic pair-wise interaction coefficients (h
2) of the solute in aqueous solutions of different salts were discussed in terms of the different alkali salt ions and weak
interactions of the diluted component with coexistent species as well as the change in solvent structure caused by ions. 相似文献
15.
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
16.
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
17.
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
18.
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
19.
20.
Lakshmi N. Roy Rabindra N. Roy Sean R. LeNoue Cole E. Denton Michael S. Fuge Craig D. Dunseth Chandra N. Roy Shawn M. Hayden Joshua T. Wollen Kripa Sreepada 《Journal of solution chemistry》2009,38(4):459-469
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already
been reported over the temperature range 5 to 55 °C including 37 °C. This paper reports the pH values of four NaCl-free buffer
solutions and four buffer composition containing NaCl salt at I=0.16 mol⋅kg−1. Conventional pa
H values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions
recommended as pH standards, at 25 and 37 °C after correcting the liquid junction potentials with the flowing junction cell. 相似文献