Compressibilities of aqueous tert-butanol in the water-rich region at 25°C: Partial molar fluctuations and mixing schemes

1999 ◽  
Vol 1 (1) ◽  
pp. 121-126 ◽  
Author(s):  
Katsutoshi Tamura ◽  
Atsushi Osaki ◽  
Yoshikata Koga
Keyword(s):  
Rich Region ◽  
Tert Butanol ◽  
Mixing Schemes

Ionic conductivity in the water-rich region of aqueous 2-butoxyethanol

1995 ◽  
Vol 73 (8) ◽  
pp. 1294-1297 ◽  
Author(s):  
Yoshikata Koga ◽  
Virginia J. Loo ◽  
Kataryna T. Puhacz
Keyword(s):  
Hydrogen Bond ◽  
Ionic Conductivity ◽  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Ionic Conductivities ◽  
Molar Conductivity ◽  
Hydrogen Bond Network ◽  
Rich Region ◽  
Mixing Schemes ◽  
Bond Network

Ionic conductivities of HCl, KOH, and KCl were measured in aqueous solutions of 2-butoxyethanol (BE) at 25 °C. The quantity, Λj′ = σ/xj, which is almost proportional to the molar conductivity, was extrapolated to the infinite dilution xj → 0. σ is the conductivity and xj is the mole fraction of j(= HCl, KOH, or KCl). The plots of 0Λj′, the value of Λj′ extrapolated to infinite dilution, against xBE showed a change in slope at xBE = 0.0175. The previous work from this laboratory indicated that the mixing scheme changes qualitatively at the same locus, xBE = 0.0175. By mixing scheme we simply mean the way in which BE and H2O molecules mix with each other. Assuming additivity in 0Λj′ in terms of constituent ions, those values for H+OH− were calculated. Plots of [Formula: see text] thus calculated as a function of xBE in the water-rich region, 0 < xBE < 0.0175, suggest that the hydrogen bond probability decreases in the bulk of solution, as xBE increases. Keywords: aqueous 2-butoxyethanol, ionic conductivities, mixing schemes, hydrogen bond network.

Dielectric relaxation in water‐tert‐butanol mixtures. The water rich region

1993 ◽  
Vol 99 (10) ◽  
pp. 8115-8119 ◽  
Author(s):  
D. Fioretto ◽  
A. Marini ◽  
M. Massarotti ◽  
G. Onori ◽  
L. Palmieri ◽  
...  
Keyword(s):  
Dielectric Relaxation ◽  
Rich Region ◽  
Tert Butanol

Solvent effects on the reactivity of solvated electrons with ions in tert-butanol/water mixtures

1995 ◽  
Vol 73 (3) ◽  
pp. 392-400 ◽  
Author(s):  
Yixing Zhao ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Pure Water ◽  
Solvated Electrons ◽  
Rich Region ◽  
Tert Butanol ◽  
Einstein Model ◽  
Activation Energy For Diffusion ◽  
Minimum Number ◽  
Solvent Molecules ◽  
Effective Reaction

Reactions of [Formula: see text] with the ions [Formula: see text] showed different variations of rate with solvent composition in tert-butanol/water mixtures from 0 to 100 mol% water. In pure tert-butanol solvent at 298 K the respective values of k2 (106 m3 mol−1 s−1) are 3.2, 13, and 42. The estimated value of reaction radius Rr depends on the minimum number of solvent molecules needed between [Formula: see text] and the reactant ion to attain the static values of ε of the bulk solvent used in the calculation of the Debye factor f; Rr is assumed to be larger in the alcohol-rich region than in the water-rich region, because the solvent molecules are larger. The Smoluchowski–Debye–Nernst–Einstein model is used to evaluate the effective reaction radius κRr, where κ is the probability of reaction per encounter; κRr decreases from pure tert-butanol to pure water. In the water-rich region the activation energies E2 of the efficient reactions, 11–24 kJ mol−1, are similar to EΛ0 of the reactant electrolyes, 12–23 kJ mol−1. For the inefficient reactant [Formula: see text] E2 = 30 kJ mol−1. The high values of E2 = 43–53 kJ mol−1 in pure tert-butanol solvent are attributed to a high activation energy for diffusion of [Formula: see text] in this solvent. Keywords:tert-butanol/water solvents, solvated electron, ions, reactivity, solvent effects.

Mixing Schemes and Liquid–Solid Phase Diagram in the Water-Rich Region of Aqueous 2-Butoxyethanol

1994 ◽  
Vol 67 (9) ◽  
pp. 2393-2397 ◽  
Author(s):  
Yoshikata Koga ◽  
Toshiaki Tanaka ◽  
Tooru Atake ◽  
Peter Westh ◽  
Aase Hvidt
Keyword(s):  
Phase Diagram ◽  
Solid Phase ◽  
Rich Region ◽  
Mixing Schemes

Excess partial molar enthalpies in the water-rich region of the isobutyric acid – water system

1991 ◽  
Vol 69 (7) ◽  
pp. 1065-1069 ◽  
Author(s):  
William W. Y. Siu ◽  
Terrance Y. H. Wong ◽  
Lisa C. F. Chao ◽  
Yoshikata Koga
Keyword(s):  
Phase Separation ◽  
Water System ◽  
Isobutyric Acid ◽  
Acid Water ◽  
Rich Region ◽  
Two Phase ◽  
Fourth Derivative ◽  
Mixing Schemes ◽  
Partial Molar Enthalpies ◽  
Structure Enhancement

The excess partial molar enthalpies of isobutyric acid (IBA), HmE(IBA), and those of H2O, HmE(H2O), were measured in aqueous solutions of IBA. The temperature dependence of HmE(IBA) at the infinite dilution suggested that the structure enhancement of the solvent H2O by IBA is weaker than those by tert-butanol (TBA) or 2-butoxyethanol (BE). The concentration dependence of HmE(IBA), and that of the enthalpic IBA–IBA interaction, N{∂HmE(IBA)/∂nB}, shows that there are two distinct mixing schemes bounded at about xB = 0.03, before reaching the two phase separation. Namely, the IBA–IBA interaction is repulsive below this boundary, while above this boundary it becomes attractive leading eventually to phase separation at a higher concentration. The transition between the two schemes is associated with a peak(negative) anomally in the fourth derivative of the free energy, N2 {∂2HmE(IBA)/∂nB2}.Key words: excess partial molar enthalpies, isobutyric acid – water, transition in mixing scheme.

scholarly journals Thermal expansivities of aqueous solutions of 2-butoxyethanol in the water-rich region: transition of mixing scheme

1992 ◽  
Vol 70 (10) ◽  
pp. 2659-2663 ◽  
Author(s):  
James V. Davies ◽  
Frankie W. Lau ◽  
Loanne T. N. Le ◽  
John T. W. Lai ◽  
Yoshikata Koga
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Gibbs Free Energy ◽  
Rich Region ◽  
Hydrophobic Solute ◽  
Thermal Expansivities ◽  
Mixing Schemes ◽  
Structure Enhancement ◽  
Derivatives Of ◽  
Transition Of Mixing Scheme

Thermal expansivities of aqueous solutions of 2-butoxyethanol (BE) were measured at concentrations of xBE < 0.04, where xBE is the mole fraction of BE. Thermal expansivity is a second derivative of the Gibbs free energy. The composition derivatives of thermal expansivities, the third derivatives, show peak anomalies at the same loci as the other third derivatives of the Gibbs free energy reported earlier from this laboratory (Can. J. Chem. 67, 671 (1989); J. Phys. Chem. 94, 3879 (1990); J. Phys. Chem. 95, 4119 (1991)). The loci of such anomalies form a boundary that separates two regions of totally different mixing schemes. The mixing scheme in the water-rich region seems to be consistent with the "iceberg formation," the "structure enhancement of H2O by hydrophobic solute," and the "hydrophobic attraction." In the intermediate composition region, the hydrogen bond network of H2O collapses due to the presence of too many molecules of BE, and H2O and BE molecules interact with each other as normal liquid molecules.

Excess partial molar enthalpies of water in water–tert-butanol mixtures

1988 ◽  
Vol 66 (12) ◽  
pp. 3171-3175 ◽  
Author(s):  
Yoshikata Koga
Keyword(s):  
Excess Free Energy ◽  
Liquid Structure ◽  
Pure Liquid ◽  
Thermodynamic Quantities ◽  
Hydrogen Bond Network ◽  
Rich Region ◽  
Tert Butanol ◽  
Chemical Potentials ◽  
Bond Network ◽  
Partial Molar Enthalpies

The excess partial molar enthalpies of H2O, HmE(H2O) in water–tert-butanol mixtures were measured at 30.00, 36.75, and 40.45°. Using the values of HmE(TBA) of the previous work (Y. Koga, Can. J. Chem. 66, 1187 (1988)), the excess (integral) molar enthalpies of the solution, HmE, were calculated at 30.00 °C, and compared with the literature values. The comparison was satisfactory. From the literature values of the excess free energy, the chemical potentials of each component were evaluated for the range, xTBA > 0.1. With the measured values of the excess partial molar enthalpies, the excess partial molar entropies were also calculated. These partial molar thermodynamic quantities and their dependence on temperature and composition clearly support the following views: (1) in the intermediate region, 0.1 < xTBA < 0.5, the system is very close to a critical demixing, and (2) in the TBA-rich region, xTBA > 0.6, TBA molecules in the solution are in almost the same environment as in the pure liquid, while H2O molecules lose the hydrogen bond network completely and are dispersed in the TBA liquid structure.

Vapour pressure of aqueous tert.-butanol in the water-rich region: transition in the mixing scheme

1990 ◽  
Vol 169 ◽  
pp. 27-38 ◽  
Author(s):  
Yoshikata Koga ◽  
Terrance Y.H. Wong ◽  
William W.Y. Siu
Keyword(s):  
Vapour Pressure ◽  
Rich Region ◽  
Tert Butanol

Observation of pseudo 10-fold symmetry in the ordered iron-zinc delta phase

1992 ◽  
Vol 50 (1) ◽  
pp. 36-37
Author(s):  
L. A. Giannuzzi ◽  
A. S. Ramani ◽  
P. R. Howell ◽  
H. W. Pickering ◽  
W. R. Bitler
Keyword(s):  
Single Phase ◽  
X Ray Diffraction ◽  
Rich Region ◽  
Average Cell ◽  
X Ray ◽  
Delta Phase ◽  
Cell Dimensions ◽  
Δ Phase ◽  
Morphological Differences ◽  
Concentration Discontinuity

The δ phase is a Zn-rich intermetallic, having a composition range of ∼ 86.5 - 92.0 atomic percent Zn, and is stable up to 665°C. The stoichiometry of the δ phase has been reported as FeZn7 and FeZn10 The deviation in stoichiometry can be attributed to variations in alloy composition used by each investigator. The structure of the δ phase, as determined by powder x-ray diffraction, is hexagonal (P63mc or P63/mmc) with cell dimensions a = 1.28 nm, c = 5.76 nm, and 555±8 atoms per unit cell. Later work suggested that the layer produced by hot-dip galvanizing should be considered as two distinct phases which are characterized by their morphological differences, namely: the iron-rich region with a compact appearance (δk) and the zinc-rich region with a columnar or palisade microstructure (δp). The sub-division of the δ phase was also based on differences in diffusion behavior, and a concentration discontinuity across the δp/δk boundary. However, work utilizing Weisenberg photographs on δ single crystals reported that the variation in lattice parameters with composition was small and hence, structurally, the δk phase and the δp phase were the same and should be thought of as a single phase, δ. Bastin et al. determined the average cell dimensions to be a = 1.28 nm and c = 5.71 nm, and suggested that perhaps some kind of ordering process, which would not be observed by x-ray diffraction, may be responsible for the morphological differences within the δ phase.

Silicification of wood-cell walls

1994 ◽  
Vol 52 ◽  
pp. 428-429
Author(s):  
S. E. Keckler ◽  
D. M. Dabbs ◽  
N. Yao ◽  
I. A. Aksay
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Cell Walls ◽  
Lignin Content ◽  
Resin Composite ◽  
Middle Lamella ◽  
Cellulose Fibers ◽  
Complex Structures ◽  
Rich Region ◽  
Inorganic Precursors

Cellular organic structures such as wood can be used as scaffolds for the synthesis of complex structures of organic/ceramic nanocomposites. The wood cell is a fiber-reinforced resin composite of cellulose fibers in a lignin matrix. A single cell wall, containing several layers of different fiber orientations and lignin content, is separated from its neighboring wall by the middle lamella, a lignin-rich region. In order to achieve total mineralization, deposition on and in the cell wall must be achieved. Geological fossilization of wood occurs as permineralization (filling the void spaces with mineral) and petrifaction (mineralizing the cell wall as the organic component decays) through infiltration of wood with inorganics after growth. Conversely, living plants can incorporate inorganics into their cells and in some cases into the cell walls during growth. In a recent study, we mimicked geological fossilization by infiltrating inorganic precursors into wood cells in order to enhance the properties of wood. In the current work, we use electron microscopy to examine the structure of silica formed in the cell walls after infiltration of tetraethoxysilane (TEOS).

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