静态法和动态法测量乙醇饱和蒸气压的比较

物质的蒸气压是化学、化工、冶金、医药等领域的重要基础数据。测量饱和蒸气压是大学物理化学实验教学中的一个基础实验,测量方法主要有静态法和动态法,但两种方法的比较尚未见报道。本文通过比较,得出了两种方法的优缺点以及注意事项。     

基于团簇结构模型的Na2O-Al2O3-SiO2三元体系熔体吉布斯混合摩尔自由能计算

以三元硅酸盐熔体团簇结构模型为基础,选取了Na₂O-Al₂O₃-SiO₂体系不同成分的团簇结构,采用半经验量子化学方法MNDO/d分别计算该三元体系熔体中不同结构的团簇基元在1473、1873、2000 K温度下的熵、焓、热容和自由能等热力学数据,计算得出不同团簇结构基元的混合自由能,并根据统计热力学波尔兹曼分布定律,推导计算得出Na₂O-Al₂O₃-SiO₂三元体系各成分下的混合摩尔自由能。三元硅酸盐熔体的热力学性质与该熔体的微观结构密切相关。     

铁改性的Mo/ZSM-5催化剂上NO的选择性催化还原反应

采用浸渍法制备了Mo/ZSM-5, Fe/ZSM-5和不同Fe和Mo摩尔比的Fe-Mo/ZSM-5样品, 并以氨为还原剂对其NO选择性催化还原活性以及反应条件对催化性能的影响进行了研究. 结果表明, Fe-Mo/ZSM-5样品的NOx转化率明显比单独的Mo/ZSM-5和Fe/ZSM-5的高. 当n(Fe):n(Mo)为1.5时, Fe-Mo/ZSM-5样品具有最佳催化性能, 其NOx转化率在430 ℃时达到了96%, 并且能在高空速和不同O2气浓度的条件下保持高的催化活性. 同时采用XRD和XPS技术分别对催化剂的体相结构和表面性质进行了研究, 结果表明, 当n(Fe):n(Mo)=1.5时, Fe和Mo元素之间以及与载体HZSM-5之间存在较强的相互作用, 并且其表面的Mo3d的含量最高. 这可能与其高的催化活性有关. 另外还发现, 在反应过程中Fe-Mo/ZSM-5催化剂表面的氮氧物种主要是吸附态NO, 因此可以推测NO的催化还原反应机理是, 在催化剂表面上, 吸附态NO与吸附NH3物种直接反应生成氮气, 而非经过氧化为NO2的途径.     

NaCl(或KCl)-CH3OH-H2O体系的摩尔电导

CHaOH－HzO体系具有非常特殊的性质,同时在工业生产及临床治疗方面有着十分广泛的应用,文献中有大量地从不同角度就这类体系进行研究的报道．然而,就N3CI及KCI－CH30H－H20体系的电导研究而言,文献中仅有关干KCI－CH30H－H20（间隔20％CH30H）的部分研究工作．作为全面、系     

生物可降解高吸水性非织造布的研制

用聚丙烯酸接枝淀粉浆液,在ＰＶＡ非织造布上形成吸水树脂,从而得到高吸水性非织造布。对接枝单体的比例、交联条件、浸轧量及非织造布规格等因素对高吸水非织造布吸水性能的影响进行了讨论了并测定了其生物降解性能。     

Beyond green with synthetic chlorophylls – Connecting structural features with spectral properties

The distinct features of chlorophylls in photosynthesis have led to the formation of numerous derivatives for applications encompassing solar energy conversion, molecular photonics, photodynamic therapy, and molecular imaging. Synthetic chlorins created de novo and bearing a geminal dimethyl group in the reduced ring have proved invaluable for fundamental studies. Four decades of research have led to accumulation of tabulated spectra for > 400 such synthetic chlorins with distinct structural frameworks (17-oxochlorins, 13¹-oxophorbines, chlorinimides) and substituents (alkyl, aryl, ethynyl, phenylethynyl, acetyl, formyl) located at specific (meso, β) positions. In this review, spectral traces (324 absorption, 247 fluorescence) are assembled along with photophysical data including the molar absorption coefficient (ε), fluorescence quantum yield (Φ_f) and singlet excited-state lifetime (τ_s). The review uses the accumulated spectral data derived from chlorins all containing a uniform molecular scaffold to (1) highlight the effects of molecular structure on spectral features, and (2) identify trends including how ε, Φ_f and τ_s vary with wavelength and other features. Use of a common geminal-dimethyl-substituted chlorin scaffold – beginning with no substituents, to one substituent at designated sites, and to 2 or more substituents – provides a systematic Aufbau approach for understanding the absorption spectra of chlorins on a path to and beyond the native chlorophylls. The review provides insights concerning the rational design of potent analogues of Nature’s preeminent red-region absorbers for potential utilization in diverse applications and is aimed at multiple audiences: those interested in spectral properties, tetrapyrrole photophysics, and the molecular design of new chromophores.     

Refractive index of standard oils as a function of wavelength and temperature

The refractive indices (n) of eight standard oils from Physikalisch Technische Bundesanstalt, Germany were determined with an accuracy of ±1×10⁻⁴ by using Abbe Refractometer. The measurements were performed at temperature 20°C in the spectral range 0.4–0.7 μm. The experimental data were fitted to the simple Cauchy dispersion formula and the results were found to be consistent within the limits of experimental error. In all cases, the refractive index decreased monotonically with increasing wavelength. The refractive indices (n) of these oils have been measured as a function of the temperature t (20°C up to 50°C) at λ=0.589 μm and were found to have linear temperature dependencies. The refractive indices of the studied oils and the uncertainty in their values are calculated at λ=0.589. The Lorentz–Lorenz (L–L) formula has been tested and it was found to be valid with a maximum deviation of 0.4% and was used to calculate the molecular polarizability θ.     

A computer controlled continuous dilution dilatometer for the determination of solute molar volumes and direct measurement of reaction volumes in solution

The design and operation of a computer controlled continuous dilution dilatometer utilizing a diode array detection system is presented. To test the accuracy and reproducibility of the technique, apparent molar volumes of dilute aqueous solutions of potassium ferricyanide and potassium ferrocyanide have been measured. To provide supporting data for high pressure studies of reaction volumes and molar volume change in solutions of high ionic strength, study of these electrolytes was extended by dilution into 0.1M and 1.0M potassium nitrate solutions rather than extrapolation to zero ionic strength as is normal. In addition, the system has been used to determine reaction volumes of some acid-base reactions by direct measurement, using the equipment as an automatic titration dilatometer.     

Studies on pre-hump and main fractions of cellulose-2,5-acetate in acetone

Technical cellulose-2.5-acetates (CA 2.5) were characterized regarding their carbohydrate composition in comparison to the raw material. The association of the CA 2.5 samples in acetone was studied by size exclusion chromatography (SEC) using various acetone grades and styrene divinylbenzene copolymer columns. In HPLC grade acetone with and without addition of 1% water up to three different pre-humps eluted in front of the main fraction of the polymer. The evaluation of the main peak by light scattering measurements resulted in high molar masses indicating that for these technical CA 2.5 samples even the main fraction is not dissolved without association. No pre-humps or association phenomena were observed after addition of 1 ppm LiBr to HPLC grade acetone or with p.a. grade acetone. In addition pre-hump enriched and pre-hump free fractions were isolated by fractionated precipitation. The carbohydrate composition of these fractions was determined and correlated with their association pattern in SEC investigations.     

Refractive Indices, Densities and Excess Molar Volumes of Monoalcohols + Water

The refractive index, n _D , and density, ρ, of binary mixtures of monoalcohols + water, have been measured at a temperature of 298.15,K and atmospheric pressure. The variation of the refractive indices of these solutions has also been determined with temperature in the range T = (278.15 to 338.15) K and atmospheric pressure. A comparative study has been made of the refractive indices obtained experimentally and those calculated by means of the Lorentz-Lorenz [Theory of Electrons, Dover Phoenix (1952)] and Gladstone-Dale relations [Trans. R. Soc. London 148:887–902 (1858)]; in all cases, the Gladstone–Dale equation was seen to afford values similar to those obtained experimentally. Calculations have been made of the excess molar volumes, V ^E, and the molar refraction deviations, ΔR, of these mixtures and the differences between the experimental values for refractive index and those obtained by means of the Gladstone–Dale equation. Values of V ^E were compared with others in the literature. In all cases the V ^E values were negative, and in all cases, except in the methanol + water, ΔR showed a maximum for x = 0.8.