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201.
A simplified approach was developed to estimate the vapor pressure of pure compounds from experimental data obtained by isothermal
thermogravimetric (TG) analysis. A numerical procedure was developed to estimate the Antoine parameters of the substance by
the analysis of isothermal TG data. The results of the experimental validations carried out evidenced that at least a preliminary
estimation of vapour pressures of pure substances by the analysis of TG data is possible. The limited time and the reduced
amounts of sample required for the experimental runs make the technique attractive with respect to the conventional and more
accurate techniques for vapor pressure assessment. 相似文献
202.
Ichimin Shirotani Yousuke Shimaya Chihiro Sekine 《Journal of solid state chemistry》2003,174(1):32-34
New filled skutterudites with heavy lanthanide, LnFe4P12 (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have systematically been prepared for the first time by the high-pressure technique. The relationship between lattice constants and atomic numbers of lanthanide (including Y) is established for LnFe4P12. Electrical and magnetic properties of several new filled skutterudites with heavy lanthanide have been studied at low temperatures; YFe4P12 shows a superconducting transition at around 7 K, and DyFe4P12 behaves as a ferromagnet below 10 K. Electrical and magnetic anomalies in DyFe4P12 and YFe4P12 are mainly discussed. 相似文献
203.
Antony Chrétien 《Tetrahedron》2005,61(33):7907-7915
Activation by Lewis acid catalysis and high pressure allows pyrrole derivatives to react with electron-rich dienes in normal electron demand [4+2] cycloadditions, provided that the aromatic ring is substituted by at least two electron-withdrawing groups. The dienophilic behavior of the heterocycle is expressed through the involvement of either the aromatic carbon-carbon double bond in an all-carbon process or the carbonyl moiety of the substituent in a heterocycloaddition reaction. In this regard, the nature of the heterocyclic substituents is shown to have a dramatic influence and to direct both the reactivity and the chemoselectivity of the cycloaddition. 相似文献
204.
The interfacial tension of aqueous dodecyltrimethylammonium chloride (DTAC) solution/hexane interface has been measured as a function of pressure at concentrations around the critical micelle concentration (CMC). The derivative of the interfacial tension with respect to pressure has been observed to change abruptly at the CMC as in the case of aqueous dodecylammonium chloride (DAC) solution-hexane system studied already. The volume changes associated with the adsorption of DTAC from its monomeric and micellar states have been calculated. The results have indicated that the micelle formation of surfactant is treated like the appearance of a new macroscopic phase in the system. It has also been concluded that the micelle solubilizing hexane bears resemblance to the adsorbed film in terms of the volume. The difference in the pressure dependence of the volume of micelle formation
MW between DTAC and DAC has been attributed to a larger polar group of DTAC. The fact that the value of
MW is larger than that estimated from the conductivity data has been explained by the solubilization of hexane into the micelle. 相似文献
205.
The reaction of fluorobenzene with urotropine in trifluoroacetic acid (TFAA) at high pressures and temperatures affords predominantly fluorobenzaldehydes andN-(fluorophenylmethyl)trifluoroacetamides. The yields of these products depend considerably on the reaction conditions. The rates of their formation have the maximum values at the momemt of the phase transition (PT) of TFAA. A new efficient cyclic (dynamic) regime is proposed for the synthesis at high pressures. The regime involves periodically occurring PT of the solvent. The change in the relative rate of product formation with the degree of fluorobenzene conversion is wave-like.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 319–323, February, 1995. 相似文献
206.
Helga Mikler 《Monatshefte für Chemie / Chemical Monthly》1989,120(1):7-10
Summary Using a high pressure X-ray camera Cu2HgI4 was subjected at room temperature to pressures up to about 8 GPa. A hexagonal high pressure phase (a=8.28 (2) Å,c=3.40 (0) Å, space group P
lm,Z=1) could be detected. This phase shows a reversible transformation with pressure hysteresis. The transition occurs at 7 GPa when the pressure is increased but at 6 GPa when the pressure is decreased.
Hexagonale Hochdruckphase von Kupfer(I)tetraiodomercurat (Cu2HgI4)
Zusammenfassung Cu2HgI4 wurde in einer Hochdruckkamera bei Raumtemperatur mit einem Druck bis zu 8 GPa belastet. Dabei bildete sich eine hexagonale Hochdruckmodifikation (a=8.28 (2) Å,c=3.40 (0) Å, Raumgruppe P lm,Z=1). Für diese Phase wurde eine reversible Umwandlung mit Druckhysterese festgestellt. Mit steigendem Druck findet die Umwandlung bei 7 GPa mit sinkendem Druck jedoch bei 6 GPa statt.相似文献
207.
Yu. A. Dyadin F. V. Zhurko T. V. Mikina R. K. Udachin 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(1):37-49
P,T,X phase diagrams of the CH2Cl2-H2O, the CHCl3-H2O and the CCl4-H2) systems have been studied by DTA in the pressure range 10–3 to 5.0 kbar. Under pressure the cubic structure II (CS-II) hydrates forming in all the systems are replaced by hydrates with the composition M·7.3 H2O whose stoichiometry and positive dT/dP values of melting lead us to believe that they are CS-I hydrates.In the CH2Cl2 and CHCl3 systems the nonvariant point coordinates of the hydrate transformationQ
2
h
(l1h17h7l2, where l1 and l2 are liquid phases abundant in water and hydrate former, respectively, h17 and h7 are hydrates with hydrate numbers 17 and 7, respectively) areP = 0.6 kbar, T = –1.5°C andP =2.65 kbar,T = –10.5°C, respectively. In the CCl4 system the 4-phaseQ
3
h
point (l1h17h7s, where s is crystalline CCl4) has coordinatesP = 0.75 kbar and T = 0.4°C.The main obstacle of the present study, the very slow achievement of equilibrium, has been eliminated by adding small amounts (0.25% by mass) of surfactants followed by ultrasonic mixing. We have shown that this accelerates the achievement of equilibrium without changing its position. 相似文献
208.
Harald Greger Otmar Hofer Andreas Werner 《Monatshefte für Chemie / Chemical Monthly》1985,116(2):273-277
In addition to the well known affinin [=spilanthol, (2E,6Z,8E)-deca-2,6,8-trienoic acid isobutylamide (1)], the corresponding 2-methyl-butylamide (2), and two new acetylenic alkamides were isolated fromSpilanthes oleracea L. by reversed phase medium pressure chromatography: (Z)-non-2-en-6,8-diynoic acid isobutylamide (3) and (Z)-dec-2-en-6,8-diynoic acid isobutylamide (4). The structures and their stereochemistries were elucidated by1H-NMR,13C-NMR (2 and3), MS, UV, IR, and CD (2). The chemotaxonomic significance of the distribution of alkamides within theCompositae tribeHeliantheae is briefly discussed.
Neue Amide ausSpilanthes oleracea (Kurze Mitteilung)
Zusammenfassung AusSpilanthes oleracea wurden neben dem seit langem bekannten Affinin [=Spilanthol, (2E,6Z,8E)-Deca-2,6,8-triensäureisobutylamid (1)] durch Umkehrphasen-Mitteldruckchromatographie das entsprechende 2-Methylbutylamid (2) und zwei neue acetylenische Alkamide isoliert: (Z)-Non-2-en-6,8-diinsäure-isobutylamid (3) und (Z)-Dec-2-en-6,8-diinsäure-isobutylamid (4). Die Strukturen und deren Stereochemie wurden mittels1H-NMR,13C-NMR (2 und3), MS, UV, IR und CD (2) aufgeklärt. Die chemotaxonomische Bedeutung der Verbreitung von Alkamiden innerhalb der Compositen-TribusHeliantheae wird kurz diskutiert.相似文献
209.
298.15K下Li2B4O7-H2O体系水蒸汽分压及渗透系数的等压测定和离子相互作用模型 总被引:2,自引:0,他引:2
在已有研究含硼体系的文献中仅考虑了硼酸根B4O7^-2或B(OH)4^-和H3BO3的存在,而对Li2B4O7-H2O体系具有多种硼物种聚合平衡体系的热力学性质的研究尚未见报道.本文用等压法研究了Li2B4O7-H2O体系于298.15K下浓度由稀到过饱和溶液的平衡气相蒸汽压及渗透系数.考虑了水溶液中多种硼物种的存在,以Pitzer方程为基础,建立了可描述该含硼体系的离子相互作用模型。 相似文献
210.
A. Kovacs A. Moussa I. Othman C. Del Valle Odar A. Seminario M. Linares P. Huamanlazo J. Aymar R. Chu 《Radiation Physics and Chemistry》1998,52(1-6):447-451
Two industrial scale, “ROBO” type 60Co gamma irradiation facilities have recently been put into operation in Syria and Peru, and the dosimetry commissioning of both plants have been carried out to determine dose distribution within products and to calculate plant parameters such as efficiency, dose uniformity ratio and throughput. There are some design modifications between the two plants in connection with the location of the carriers with respect to the source plaque and also to each other. The effect of these construction modifications on the plant parameters is discussed in the analysis of the dose distribution data measured in the carriers with depth and height among the four irradiation rows on both sides of the source plaque. The plant parameters were also calculated for different product densities using the technical data of the facilities, and the calculated and measured results were compared to each other. 相似文献