Viscosities of Binary and Ternary Mixtures of Water,Alcohol, Acetone,and Hexane

This articles studied and determined the viscosities of the binary mixtures of water–methanol, water–ethanol, water–propanol, water–acetone, acetone–ethanol, methanol–ethanol, and acetone–hexane and the ternary mixtures of water–methanol–ethanol and water–ethanol–acetone at 20°C. It is shown that the mixing of water with the alcohols and acetone resulted in a positive deviation of viscosity, which reached the maximum value at the water mole fraction x ₁ ～ 0.7 for water–methanol, x ₁ ～ 0.72 for water–ethanol, x ₁ ～ 0.74 for water–propanol, and x ₁ ～ 0.83 for water–acetone binary mixture. This viscosity deviation can be mainly attributed to the formation of micelles of alcohol or acetone molecules in water because of the hydrophobic attraction between the hydrocarbon chains. The micelle surfaces are surrounded by hydration layers, leading to the positive viscosity deviation in the liquid mixtures because the water in hydration layers has a much higher viscosity than bulk water. Also, the contrary observation was found in the binary mixtures of acetone–ethanol and acetone–hexane, having a negative viscosity deviation.     

Fast polarisation-insensitive optical shutter supported by backflow in dichroic dye-doped dual-frequency liquid crystal

This paper describes a novel implementation of a dual-frequency liquid crystal optical shutter of the guest–host type. The transmissive state of the filter is obtained by applying a low-frequency electric field that brings the dichroic dye in a homeotropic orientation. The light-absorbing state is realised by a twisted planar configuration for which the absorption is quasi-independent of the polarisation. Switching between the two states occurs in about 1 ms and the devices show no scattering for wavelengths inside or outside the absorption band of the dichroic dye. Simulations and experiments reveal how a twisted state is obtained through the backflow phenomenon.     

Synthesis,mesogenic and dielectric properties of fluorosubstituted isothiocyanatoterphenyls

The synthesis, mesomorphic and physical properties of 14 homologous series of laterally fluorinated 4?-alkyl-4-isothiocyanatoterphenyls were described. Influence of the number of fluorine atoms and their position in the terphenyl core on the phase transition temperatures, nematic range, dielectric and optic anisotropy as well as bulk viscosity were discussed. The compounds with the most optimal properties for formulation of nematic mixtures were selected, and mixture examples with low viscosity and medium or high birefringence were presented.     

氢气对正丁烷/空气混合物催化着火的热作用和化学作用

通过对正丁烷/氢气/空气混合物在Pt 催化表面的详细反应机理分析, 研究了氢气添加对正丁烷/空气混合物催化着火过程的影响. 研究发现, 在正丁烷/空气混合中添加氢气有助于正丁烷在更低的温度下实现催化着火, 而且不同的氢气添加量对混合物的着火温度和着火过程呈现不同的影响: 当氢气添加量较小时, 氢气的作用主要呈现为热影响; 而当氢气添加量较大时, 氢气的作用主要呈现为化学影响. 这些结果与实验结果是一致的. 本文进一步确定了发挥不同作用的氢气添加量的范围, 并分别对热作用和化学作用情况下的着火启动反应进行了动力学分析.     

初中化学“酸和碱的性质”创意教学*——探析食品发热包

以食品发热包为主题情境,通过探析发热包成分、解密发热原理、计算原料配比、配制发热包等环节梳理酸和碱的性质、用途。从元素观、转化观的视角认识物质转化规律,体现物质研究的一般思路,凸显科学探究的基本过程。通过设计方案测定发热包中碳酸钠的含量,总结混合物成分鉴定及定量测定的方法;归纳气体定量测定的影响因素。呈现一堂学科观念、学科方法教学具体课例,凸显物质研究、定性检验、定量测定的基本方法。     

Sorptive elimination of fluoride from contaminated groundwater in a fixed bed column: A kinetic model validation based study

The current investigation involves a continuous adsorption experiment in a packed bed column for the sorptive elucidation of fluoride from contaminated groundwater using an activated soil-clay mixture. Through the combination of naturally accessible laterite soil with silica enriched clay (3:1 ratio), a low-cost Al–Si heterogeneous material has been developed. Following detailed characterization, the developed materials were employed in a long-time column process to achieve a high degree of fluoride separation from real-world groundwater. In a packed bed column investigation, the effect of bed height, initial fluoride concentration, and flow rate on the breakthrough properties of the adsorption system were investigated. By using a non-linear regression equation, three model kinetics, such as the Thomas Model, Adams-Bohart Model, and Yoon-Nelson Model, were fitted to validate the column-based experimental data, by analysing the breakthrough curves profiles, and distinct kinetic parameters. The Bed Depth Service Time Analysis (BDST) model was tested to express the effect of bed height on breakthrough curves, as well as to predict the time for breakthrough, and material depletion under optimal conditions. The Thomas and Yoon-Nelson models were identified to be the most appropriate ones for describing the entire breakthrough curve, whereas the Adams-Bohart model was only utilised to predict the first half of the dynamic process. With correlation coefficients (R²) 0.96, the experimental results were well suited to Thomas, Yoon-Nelson, and Adams-Bohart models. Finally, regeneration assessment was carried out where even after four cycles of operation, regenerated adsorbent showed a rejection efficacy of 78% to fluoride that proves the viability of the material and methodology.     

Functionalized Graphene as a Gatekeeper for Chiral Molecules: An Alternative Concept for Chiral Separation

We propose a new method of chiral separation using functionalized nanoporous graphene as an example. Computational simulations based on density functional theory show that the attachment of a suitable chiral “bouncer” molecule to the pore rim prevents the passage of the undesired enantiomer while letting its mirror image through.     

Polydimethylsiloxane: A General Matrix for High‐Performance Chromatographic NMR Spectroscopy

The detection and structural characterization of the components of a mixture is a challenging task. Therefore, the development of a facile and general method that enables both the separation and the structural characterization of the components is desired. Diffusion‐ordered NMR spectroscopy (DOSY) with the aid of a matrix is a promising tool for this purpose. However, because the currently existing matrices only separate limited components, the application of the DOSY technique is restricted. Herein we introduce a new versatile matrix, poly(dimethylsiloxane), which can fully separate many mixtures of different structural types by liquid‐state NMR spectroscopy. With poly(dimethylsiloxane), liquid‐state chromatographic NMR spectroscopy could become a general approach for the structural elucidation of mixtures of compounds.     

Some novel photosensitive diacetylene diurethanes and their mixtures in common polymers

Some new octa-3,5-diynylene diurethanes were prepared using 3-butyn-1-ol, and all were found to be highly light-sensitive and to undergo topochemical polymerization on exposure to irradiation. The di-n-octyldiurethane was mixed with vinyl polymers such as poly(vinyl acetate) and poly(N,N-dimethylamino-ethyl methacrylate) and the mixtures were made into thin films by spin coating. The films were then irradiated by an electron beam to polymerize the diacetylene. The purple films thus obtained showed third-order nonlinear susceptibility, χ⁽³⁾, of the order of 10⁻¹⁰–10⁻¹¹ e.s.u.     

混合工质HFC134a/HCs替代R502的性能分析

针对目前R502主流替代工质R507和R404A存在的温室效应指数高、与矿物油互溶性差等缺点,提出了环保性能更好的三组近共沸混合工质R134a/R290、R134a/R1270和R134a/R290/R1270作为R502新型替代工质;并对其热物性、循环性能、安全性能和溶油性进行了计算分析。结果表明：除了压缩机排气温度偏高,这三组R134a/HCs混合工质的其它主要循环性能参数如压缩机压力比、容积制冷量和系统性能系数COP都优于R507和R404A,并且从理论上讲不存在可燃可爆的危险,同时可以与矿物油互溶,在替代R502方面更具有优势,其中R134a/R290/R1270在高热负荷下的综合性能最优良。