STUDIES ON THERMAL BEHAVIOUR OF TETRAALKOXYSILANES

Tetraalkoxysilanes (Compounds A to O) were prepared by reacting SiCI4 with corresponding alcohols in the liquid phase in the presence of pyridine as acid acceptor in benzene solvent. Based on the experimental evidences and theoretical calculations tentative structures had been proposed. Properties such as density, refractive index, viscosity, surface tension, molecular weight, thermal expansion, specific heat, thermal conductivity, decomposition temperature and oxidation stability were determined. Prandtl number, Reynold's number and heat transfer coefficient for tetraalkoxysilanes were calculated and were compared with those of coolanols of Monsanto Chemicals, USA. Thermal stability of the compounds was studied by heating them at 200°C for 100 hours in the presence and in the absence of phenyl-a-naphthylamine and diphenylamine as stabilizers and redetermining some of the properties like density, refractive index, surface tension, viscosity and molecular weight

The variation of the properties due to heat treatment is less significant when they are heated in the presence of a stabilizer. The low variation of physical constants by heat treatment particularly in the presence of a stabilizer suggests that these compounds are thermally stable and can be used in heat transfer and other thermal applications with stabilizers     

Measurement and correlation of physical properties of aqueous solutions of tetrabutylammonium hydroxide,piperazine and their aqueous blends

The density, viscosity and refractive index of aqueous solutions of tetrabutylammonium hydroxide (TBAOH), pi-perazine (PZ) and their aqueous blends are determined at several temperatures (303.15 to 333.15 K). All these measured physicochemical properties decreases with an increase in temperature. The density data is used to cal-culate the coefficient of thermal expansion and excess molar volume of al aqueous binary and ternary solutions. The coefficient of thermal expansion increases with increase in temperatures and concentrations. The negativity of excess molar volume for al the aqueous solution decreased with increase in temperature. Each physical prop-erty is correlated with temperature by least square method and the corresponding coefficients for each property are presented. The prediction values from correlations for the physical properties are in good agreement with the experimental values.     

溴化锂及离子液体水溶液密度、黏度和表面张力测定与计算

常压条件下,实验测定了不同温度（283.15~343.15 K）下吸收制冷/热泵工质对——溴化锂（LiBr）、1-乙基-3-甲基咪唑醋酸盐（[EMIM][OAC]）和1-丁基-3-甲基咪唑硫氰酸盐（[BMIM][SCN]）水溶液的密度、黏度和表面张力,借助线性方程和Vogel-Tammann-Fulcher（VTF）模型,分别成功关联了密度和黏度实验值。研究结果表明：在相同条件下,溴化锂水溶液的密度大于离子液体水溶液的密度,而前者的黏度小于后者;对表面张力,随着溴化锂含量增加,其水溶液的表面张力值增加,而少量离子液体可使水的表面张力快速下降。根据实验黏度和表面张力分别获得了能量势垒和表面熵/焓,表明各水溶液中分子或离子迁移难易程度遵循[EMIM][OAC] > [BMIM][SCN] > LiBr,表面有序性遵循[BMIM][SCN] > [EMIM][OAC] > LiBr。研究结果可为吸收制冷/热泵工质对及低温余热回收系统的设计和计算提供可靠的数据支撑。     

Physicochemical properties of water-alcohol mixtures of a homological series of lower aliphatic alcohols

The results of a study of physicochemical properties (density, viscosity, refractive index, contraction, and surface tension) of water-alcohol (water-ethanol, water-propanol, and water-isopropanol) and alcohol-alcohol (propanol-butanol) mixtures are presented. The ratios of water and alcohol corresponding to the maxima of the viscosity and contraction of the mixtures are determined. A nonlinear character of dependences of the density and refractive index for water-alcohol mixtures versus their composition is demonstrated.     

50味常用中药挥发油的理化性质研究

通过考察50味常用中药挥发油的物理化学性质,建立其表征技术体系,探索中药挥发油物理化学性质的规律性。以水蒸气蒸馏法提取50味常用中药中的挥发油,测定其20、40、60~C时的浊度、粘度、电导率、盐度、pH值、密度、表面张力、折光率等指标。结果表明,中药挥发油一般均较澄清、粘度在0—10mPa·S之间,无盐度和电导率,pH值在3．353—6．654之间,为弱酸性,相对密度在0．8557～1．1516之间,表面张力在27．85—50．46N·cm。之间,折光率在1．4475—1．5987之间,这些物理化学参数随温度的变化存在一定的规律性。     

Physicochemical properties of aqueous solutions of sodium glycinate in the non-precipitation regime from 298.15 to 343.15 K

The physicochemical properties, including the density, viscosity, and refractive index of aqueous solutions of sodium glycinate as a solvent for CO2 absorption in the non-precipitation regime were measured under the wide temperature range of 298.15 to 343.15 K. The concentration of the sodium glycinate in an aqueous form in the non-precipitation regime was identified up to 2.0 mol·L?1. The coefficients of thermal expansion values were estimated from measured density data. It was found that, the densities, viscosities and refractive indices of the aqueous sodium glycinate decrease with an increase in temperature, whereas with increasing sodium glycinate concentration in the solution, all three properties increase. Thermal expansion coefficients slightly increase with rising temperature and concentration. The measured values of density, viscosity and refractive index were correlated as a function of temperature by using the least squares method. The predicted data obtained from correlation equations for all measured properties were in fairly good agreement with the experimental data.     

Effect of Temperature on the Physico-Chemical Properties of a Room Temperature Ionic Liquid (1-Methyl-3-pentylimidazolium Hexafluorophosphate) with Polyethylene Glycol Oligomer

A systematic study of the effect of composition on the thermo-physical properties of the binary mixtures of 1-methyl-3-pentyl imidazolium hexafluorophosphate [MPI][PF(6)] with poly(ethylene glycol) (PEG) [M(w) = 400] is presented. The excess molar volume, refractive index deviation, viscosity deviation, and surface tension deviation values were calculated from these experimental density, ρ, refractive index, n, viscosity, η, and surface tension, γ, over the whole concentration range, respectively. The excess molar volumes are negative and continue to become increasingly negative with increasing temperature; whereas the viscosity and surface tension deviation are negative and become less negative with increasing temperature. The surface thermodynamic functions, such as surface entropy, enthalpy, as well as standard molar entropy, Parachor, and molar enthalpy of vaporization for pure ionic liquid, have been derived from the temperature dependence of the surface tension values.     

Reaction of uric acid with excess of propylene carbonate

New method of synthesis of polyetherols with purine ring by reaction of propylene carbonate with uric acid is presented. The influence of kind of catalyst, and molar ratio of substrates on structure, and physical properties of polyetherols; density, viscosity, surface tension, and refractive index were determined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2482–2487, 2006     

Determination of physical properties for the mixtures of [BMIM]Cl with different organic solvents

Physical properties including refractive index, density, viscosity and conductivity for binary mixtures of 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) and different organic solvents at 298.15 K have been investigated. Ex-cess molar volumes have been calculated and obtained data has been fitted by the Redlich–Kister equation. The density and refractive index were found to increase with increasing concentration of [BMIM]Cl, however, excep-tions do exist as in the case of dimethyl sulfoxide (DMSO)/[BMIM]Cl. For DMSO/[BMIM]Cl, the density decreases with increasing concentration. The addition of different organic solvents was able to disrupt the interactions within mixtures, leading to free mobility of ions. The free mobility of ions has been found to enhance conductivity and decrease viscosity to varying extents in al mixtures studied. It has been observed that solubility parameters, dielectric constants and composition of the solvents used play a vital role in determining the resultant properties. The data obtained wil play an important role in understanding the effect of the addition of organic solvents in ILs to enhance their applicability.     

Surface tension and viscosity of 1-butyl-3-methylimidazolium iodide and 1-butyl-3-methylimidazolium tetrafluoroborate, and solubility of lithium bromide+1-butyl-3-methylimidazolium bromide in water

The surface tension and viscosity of 1-butyl-3-methylimidazolium iodide ([bmim][I]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured over a temperature range of 298. 15 to 323.15 K. It was found that both the viscosity and surface tension decrease with increasing temperature and that the surface tension and viscosity values of [bmim][I] were higher than those of [bmim][BF₄]. Additionally, the solubility of lithium bromide (2)+1-butyl-3-methylimidazolium bromide ([bmim][Br]) (3) in water (1) was measured at three different mass ratios (w₂/w₃=4 and 7, w₃=0) by using a visual polythermal method. The solubility of the suggested systems was better than that of lithium bromide in water.     

Influence of Small Quantities of Water on the Physical Properties of Alkylammonium Nitrate Ionic Liquids

This paper presents a comprehensive study of two alkylammonium nitrate ionic liquids. As part of this family of materials, mainly ethylammonium nitrate (EAN) and also propylammonium nitrate (PAN) have attracted a great deal of attention during the last decades due to their potential applications in many fields. Although there have been numerous publications focused on the measurement of their physical properties, a great dispersion can be observed in the results obtained for the same magnitude. One of the critical points to be taken into account in their physical characterization is their water content. Thus, the main objective of this work was to determine the degree of influence of the presence of small quantities of water in EAN and PAN on the measurement of density, viscosity, electrical conductivity, refractive index and surface tension. For this purpose, the first three properties were determined in samples of EAN and PAN with water contents below 30,000 ppm in a wide range of temperatures, between 5 and 95 °C, while the last two were obtained at 25 °C. As a result of this study, it has been concluded that the presence of water is critical in those physical properties that involve mass or charge transport processes, resulting in the finding that the absolute value of the average percentage change in both viscosity and electrical conductivity is above 40%. Meanwhile, refractive index (≤0.3%), density (≤0.5%) and surface tension (≤2%) present much less significant changes.     

Physical and electrochemical properties of 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide,and 1-butyl-3-methylimidazolium tetrafluoroborate

The density, viscosity, refractive index, heat capacity, heat of dilution, ionic conductivity, and electrochemical stability of 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium iodide ([bmim][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured at room temperature or over a temperature range of 293.2 to 323.2 K. The density and refractive index values of [bmim][I] appeared to be the highest among three ionic liquids (ILs). However, the experimental viscosity values of [bmim][Br] were higher than those of [bmim][BF₄], while the heat capacities and heats of dilution of [bmim][BF₄] were higher than those of [bmim][Br]. The cyclic voltammogram of [bmim][br] and [bmim][BF₄] indicated electrochemical windows in the stability range from 2.7 V of [bmim][[Br] to 4.7 V of [bmim][BF₄].     

Thermodynamic properties of 1‐ETHYL‐3‐methylimidazolium methanesulphonate with aromatic sulphur,nitrogen compounds at T = 298.15–323.15 K and P = 1 bar

This work investigates the ability of 1‐ethyl‐3‐methylimidazolium methanesulphate ([EMIM][MeSO₃]) as a green and tuneable solvent for denitrification and desulphurisation studies. Experimental density, surface tension and refractive index data have been measured for the following systems: [EMIM][MeSO₃] (1) + pyridine (2), [EMIM][MeSO₃] (1) + pyrrole (2), [EMIM][MeSO₃] (1) + quinoline (2), [EMIM][MeSO₃] (1) + indoline (2), [EMIM][MeSO₃] (1) + thiophene (2) and [EMIM][MeSO₃] (1) + water (2) over the entire mole fraction of [EMIM][MeSO₃] at T = 298.15–323.15 K and P = 1 bar. Further from experimental density, surface tension and refractive index, coefficient of thermal expansivity, excess molar volume, deviation of surface tension and refractive index deviation were also calculated. It was found that the heteroaromatic nitrogen/sulphur compounds are completely miscible in [EMIM][MeSO₃]. The surface tension values were found to increase while the refractive index decreases with increasing mole fraction of [EMIM][MeSO₃]. The experimental values for surface tension increased in the order: pyridine > thiophene > pyrrole > indoline > quinoline > water and for refractive index: pyridine > pyrrole > indoline > quinoline > thiophene > water. It was found that the composition of [EMIM][MeSO₃] has a greater influence than temperature in deciding the surface, optical and thermodynamic properties for similar molecular interaction such as IL–thiophene and IL–pyrrole than dissimilar molecules such as IL–water. Further quantum chemical‐based COSMO‐RS tool was used to estimate the activity coefficient at different composition. © 2012 Canadian Society for Chemical Engineering     

Thermal history and its implications: A case study for ion exchange

Glasses containing monovalent species can be chemically strengthened by the replacement of smaller ions in the glass with larger external ions in the near glass surface. This type of ion exchange puts glass surface under high compressive stress (CS). Glass mainly fails from tension with the presence of surface flaws. Chemical strengthening can change the stress at the flaw tip from tension to compression and further stop the flaw from propagating. Glass damage resistance is therefore significantly improved. For the same glass composition, glass thermal histories can affect the magnitude and depth of the CS generated during ion exchange. In this study, the impact of thermal history on glass physical properties and ion exchange attributes in one alkali-containing glass formed by fusion draw process was investigated. Multiple thermal treatments were done to rewrite the glass thermal histories. Glass density, refractive index, and ion-exchange properties as a function of the thermal treatment were studied. It is concluded that ion exchange-related properties change dramatically with the glass thermal history.     

Studies on the Extraction of Actinides by Substituted Butyl Phosphonates

The extraction of actinides by homologs of dibutylalkyl phosphonates has been studied in detail. This study was taken up in order to understand the influence of the phosphorus-carbon bond in phosphonates on the extraction of actinides. In this context, dibutylhexyl phosphonate (DBHeP) and dibutyloctyl phosphonate (DBOP) were synthesized and characterized by various techniques. The physical properties of the two solvents and the extraction of nitric acid and actinides by these phosphonates were compared with those by dibutylbutyl phosphonate (DBBP). The physical properties such as density, viscosity, surface tension, refractive index, and solubility are reported here for the first time. Dispersion number, a dimensionless quantity that characterizes the ability of the solvent to separate from two-phase dispersion, is reported for all the three phosphonates. The extraction characteristics of actinides by these series of compounds are compared with those by tributyl phosphate (TBP).     

Effect of Water Concentration on the Properties of Commercial Soda-Lime-Silica Glasses

The effect of water concentration on the properties of three commercial soda-lime-silica glasses has been measured. Water (H₂O) concentration varied from 50 to 550 ppm-wt. Properties measured include glass transformation temperature, transformation range viscosity, thermal expansion coefficient, electrical conductivity, and refractive index. The viscosity, T _g, and electrical conductivity decreased with increasing water content, while the thermal expansion coefficient and refractive index were unaffected by changes in water concentration.     

改良人工神经网络方法预测烷烃物理性质

引言近年来,图论不变量用于定量构效关系（QSAR)和定量构性关系（QSPR）研究已引起许多化学家和其他相关科学家的极大兴趣,发表了许多有关图论指数的优秀论文．Randic指出一个新的图论指数至少应具有对各种异构体的良好分辨能力和与物质物理性质的高相关性．然而,已有的指数较难同时满足这两个基本条件．为此,前文基于分子结构的两个最基本特征即原子间距离和相互连接边数,提出了一种称之为分子距边矢量(简称MDE矢量）的新图论参数,并已证明该矢量对于150个烷烃具有良好的分辨能力和性质相关性,并以多元线性回归方法对烷烃沸点…     

Composition–structure–property relationships of transparent Ca–Al–Si–O–N oxynitride glasses: The roles of nitrogen and aluminum

We explore the formation and composition–structure–property correlations of transparent Ca–Al–Si–O–N glasses, which were prepared by a standard melt-quenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness—along with the Young, shear, and bulk elastic moduli—depended roughly linearly on the N content. These effects are attributed primarily to the improved glass-network cross-linking from N compared to O, rather than the formation of higher-coordination AlO₅ and AlO₆ groups, where ²⁷Al magic-angle-spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO₄ units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical–property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass-composition domains that are likely to offer optimal mechanical properties.     

离子液体[C4mim][PF6]与N, N-二甲基甲酰胺二元混合物在298.15 K～318.15 K的密度和粘度

Viscosities and densities for 1-butyl-3-methylimidazolium hexafluorophosphate （[C4mim][PF6]） and N, N-dimethylformamide （DMF） binary mixtures have been measured at the temperature range from 293.15 K to 318.15 K. It is shown that the viscosities and densities decrease monotonously with temperature and the content of DMF. Various correlation methods including Arrhenius-like equation, Sedclon et al.＇s equation, Redlich-Kister equation with four parameters, and other empirical equations were applied to evaluate these experimental data. A model based on an equation of state Ior estimating the viscosity of mixtures containing ionic liquids were proposed by coupling with the excess Gibbs free energy model of viscosity, which can synchronously calculate the viscosity and the molar volume. The results show that the model gives a deviation of 8.29% for the viscosity, and a deviation of 1.05% for the molar volume when only one temperature-independent adjustable parameter is adopted. The correlation accuracy is further improved when two parameters or one temperature-dependent parameter is used.     

Effect of firing temperature on the properties of sol-gel films of the CuO-TiO2 system

The viscosity, surface tension, and refractive index of 2-day-old film-forming solutions of the CuO-TiO₂ system of different composition were compared with the structure and properties of coatings on float glass made from them. Regardless of the composition and firing conditions, the film thickness remained constant. The refractive index and mirror reflection coefficient of the coatings are correlated by a directly proportional dependence. Increasing the firing temperature does not change or increases the values of the refractive index and mirror-reflection coefficient of the films. The chemical resistance of the coatings to water or hydrochloric acid solution is not a function of or improves with an increase in the firing temperature.