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71.
The solubility of argon in pure liquid water was measured at ca. 100 kPa and from 2 to 40°C using an analytical method characterized by an imprecision of about ±0.05%. From the experimental results, Henry fugacities H
2,1
(T,P
s,1
) (also known as Henry's Law constants or Henry coefficients) at the vapor pressure P
s,1
of water as well as Ostwald coefficients L
2,1
at infinite dilution were obtained. Measurements were made at roughly 0.5°C and/or 1° intervals between 2 and 8°C (region I), and at 5°C intervals above 10°C (region II). A difference plot lnH
2,1
/T suggests an unusual temperature dependence in region I, i.e., between 2 and 8°C. Because of this, the data were treated separately in two parts corresponding to these two regions. Our results are compared with the recent high-precision data of Krause and Benson (Henry fugacities), and with calorimetrically determined quantities (enthalpies and heat capacities of solution). Finally, experimental results are compared with values calculated via scaled particle theory.Communicated in part at the 2nd International Symposium on Solubility Phenomena in Newark, New Jersey, August 12–15, 1986, and at the 4th ISSP in Troy, New York, July 20–August 3, 1990. 相似文献
72.
Yu Yang Maya Belghazi Arnaud Lagadec David J. Miller Steven B. Hawthorne 《Journal of chromatography. A》1998,810(1-2):149-159
The intermolecular interactions between organic solutes and sorbent matrices under subcritical water conditions have been investigated at a pressure of 50 bar and temperatures ranging from 50 to 250°C. Both polar and nonpolar organics (chlorophenols, amines, n-alkanes, and polycyclic aromatic hydrocarbons) and five different sorbent matrices (glass beads, alumina, Florisil, silica-bonded C18, and polymeric XAD-4 resins) were used. From the same matrix, the polar solutes always eluted at lower temperatures, while the moderately polar and nonpolar solutes only eluted at higher temperatures. Similar to matrix effects previously observed using supercritical carbon dioxide, the sorbent type greatly influenced the elution efficiency under subcritical water conditions. Lower temperatures are sufficient to elute a particular solute from glass beads, alumina, and Florisil, but higher temperatures (less polar water) are needed to elute the same solute from silica-bonded C18. The highest temperatures were required to elute aromatic organics from XAD-4. These matrix effects demonstrate that, while low temperature water can break inert or dipole interactions between solutes and glass beads, alumina, and Florisil, higher temperature water is required to interrupt the van der Waals attractions between solutes and silica-bonded C18, and even higher temperatures needed to overcome the π-electron interactions between aromatic solutes and XAD-4. 相似文献
73.
On the Chemical Transport of Cr2O3 with CrI3/I2 – Experiments and Model-Calculations for Participation of CrOI2,g Gaseous chromium oxyiodides that were unknown up to now cause the migration of Cr2O3 in the temperature gradient 1 000°C→900°C when iodine (e. g. 0.1 mmol/ml) and CrI3 is added (eq. (1)). Transport agent for Cr2O3 is gaseous CrI4. With a smaller concentration of iodine (D(I2) ? 0.016 mmol/ml) and lower temperatures (e.g. T? = 850°C) the influence of H2O (from the wall of the silica ampoule) becomes more important. Under these conditions the transport of Cr2O3 is a result from the endothermic reactions (2), (3) and (4). H2,g has on the basis of the decomposition of HIg a positive difference of the solubility and H2,g should not to be considered as a transport agent. Because of the range of equilibrium-values the reaction 4 has to be taken into consideration. Estimated value of the enthalpie for CrOI2,g is fixed more precisely by thermodynamic model calculation to ΔfH°298(CrOI2,g) = ?51.4 kcal/mol. The estimated limit of error for the enthalpie of formation is smaller than ± 5 kcal/mol. Without an addition of CrI3 is in the system Cr2O3/I2 a migration of Cr2O3 not observable. 相似文献
74.
The dissociation of water adsorbed on the surface of NiO was investigated by using the semi-empirical SCF MO method MSINDO.
Simulations were based on embedded cluster models representing the (100) surface, with and without a monatomic step. The angle
formed between the metal adsorption site and the O–H bond associated with water has been found to be critical to the energetics
of the dissociation process. Based on this criterion, it was shown that water dissociation is favorable on the stepped surface,
but highly unlikely on the planar surface. In addition, the activation energy required for water dissociation in a monatomic
NiO step was considerably lower than for dissociation at the planar surface. The high activation energy associated with water
dissociation on the planar surface is attributed to the rigidity of the NiO lattice.
Dedicated to Prof. K. Jug in honor of his 65th birthday 相似文献
75.
Mikhail Vorob''ev 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):133-140
The role of aqueous media in the stabilization of globular proteins and formation of gels was studied by absorption millimeter spectroscopy. This method allowed to measure bound water, the fraction of water which had decreased rotational mobility owing to the presence of solute. Hydration data for globular proteins were compared with data obtained previously for low-weight molecules and groups. It was found that rotational mobility of water molecules in the hydration shells of various kinds of solutes (groups) decreased in the following order: water structure breaking compounds>polar groups>unfolded proteins>globular proteins>non-polar groups. Time courses of the storage modulus were determined for the chemical acidification by glucono-δ-lactone (GDL) of milk samples prepared from skimmed milk powder (SMP). Gelation of unheated milk was a monotonous process that started at pH 4.9. Heat-treated milk from SMP (16 and 14 g per 100 ml) acidified by GDL (3 g per 100 ml) at 43 °C gave non-monotonous kinetics of gelation with two phases corresponding to the mechanisms induced by denatured whey proteins at pH>5 and by casein–casein interactions at pH 4.8–4.9. For heat-treated milk, measurement of bound water gave two stages of decrease in water mobility. Additional hydration of SMP during acidification gave 0.15–0.2 g and 0.8 g bound H2O per gram of SMP for unheated and heat-treated milk, respectively. 相似文献
76.
Chemical reactions occurring at the mineral–water interface are controlled by an interfacial layer, nanometers thick, whose properties may deviate from those of the respective bulk mineral and water phases. The molecular-scale structure of this interfacial layer, however, is poorly constrained, and correlations between macroscopic phenomena and molecular-scale processes remain speculative. The application of high-resolution X-ray scattering techniques has begun to provide substantial new insights into the molecular-scale structure of the mineral–water interface. In this review, we describe the characteristics of synchrotron-based X-ray scattering techniques that make them uniquely powerful probes of mineral–water interfacial structures and discuss the new insights that have been derived from their application. In particular, we focus on efforts to understand the structure and distribution of interfacial water as well as their dependence on substrate properties for major mineral classes including oxides, carbonates, sulfates, phosphates, silicates, halides and chromates. We compare these X-ray scattering results with those from other structural and spectroscopic techniques and integrate these to provide a conceptual framework upon which to base an understanding of the systematic variation of mineral–water interfacial structures. 相似文献
77.
通过比较纯水、NaX(X=F, Cl, Br, I)、Na2S、NaOH、NaNO3、Na2CO3、Na2SO4溶液的羟基伸缩振动拉曼光谱, 发现所研究的阴离子对水的结构都有破坏作用. 通过比较阴离子对水的羟基伸缩振动拉曼光谱的影响, 可将所研究的阴离子分为两类, 一类阴离子有F−、OH−、S2−、CO32−, 另一类阴离子有Cl−、Br−、I−、NO3−和SO42−. 它们的主要区别在于对羟基伸缩振动拉曼光谱3600 cm−1、2900−3100 cm−1处影响不同, 产生这些区别的原因在于阴离子与水分子之间氢键的强弱. 阴离子对水的羟基伸缩振动拉曼光谱的影响因素有离子半径、离子电荷和离子结构, 它们的影响程度为离子结构>离子电荷>离子半径. 相似文献
78.
A. V. Tvardovskii A. A. Fomkin Yu. I. Tarasevich I. G. Polyakova V. V. Serpinskii I. M. Guseva 《Russian Chemical Bulletin》1992,41(1):23-28
Deformations of Na, Ca, and Ba vermiculites upon sorption of water vapor have been determined by a dilatometric method. Sequential stages in the hydration of interlayer exchange cations have been identified. The experimental results have been compared with data obtained in studies using adsorptive, calorimetric, and x-ray methods.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Institute of Colloid Chemistry and the Chemistry of Water, Academy of Sciences of the Ukraine, Kiev. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 34–39, January, 1992. 相似文献
79.
80.
Electrospraying/electrospinning of poly(γ-stearyl-L-glutamate) (PSLG) was investigated on a series solutions with different concentrations in chloroform. Field emission scanning electron microscopy (FESEM) and attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) were used to characterize the morphology and structure of the electrosprayed/electrospun polypeptide mats. It was found that electrospraying of PSLG with concentrations lower than 16 wt% afforded beads, while microfibers could be electrospun at the concentration of 22 wt%. The hydrophobicity of the electrosprayed/electrospun PSLG mats was investigated with static water contact angle (WCA) and tilt angle measurements. It was demonstrated that the superhydrophobic surfaces of PSLG with WCAs and tilt angles in the ranges of 150°-170° and 16.5°-4.2°, respectively, were obtained through electrospraying/electrospinning process. 相似文献