双液系气液平衡相图实验的研究

二组分完全互溶的双液系的气液平衡相图实验是物理化学实验的基本内容之一,通常是用沸点仪在常压条件下测定双液系在不同组成时的沸点和气、液两相呈平衡时的组成,从而作出沸点-组成相图。外界压力不同时,同一双液系的相图也不尽相同,所以恒沸点和恒沸混合物组成与外压有关。因此,通常情况下,用标准数据去衡量学生实验所得的恒沸点和恒沸混合物的数据就不够精确。本文是用自制的简易恒压沸点仪,在不同的压力下,对丙酮-氯仿和异丙醇-环己烷体系的恒沸点,恒沸混合物组成进行了研     

气相色谱-质谱联用法研究蛇油中腥味物质成分

采用真空-挥发-平衡的方法将蛇油挥发组分进行有效的收集,然后利用气相色谱-质谱联用(GC-MS)的手段对蛇油中的异味或腥味物质进行了分离腚和鉴定,并对除异味处理前后的蛇油挥发组分进行了对比.实验结果发现,蛇油中的腥味物质主要是中碳链的饱和与不饱和的低沸点的醛类、烯醛和烯醇类.质谱检索的结果为己醛、庚醛、2-辛烯醇、2-壬烯醇、2-壬烯醛、2-癸烯醛等,此分析方法的建立对蛇油的深度开发利用很有意义.     

甲醇—乙醇—水—盐体系的等压气液平衡

木文采用CPⅡ型沸点仪测定了在93.33kPa下甲醇-乙醇-水-盐(NaCl,NaBr,Nal,LiCl,CaCl_2)体系的气液平衡数据。实验证明,当三元混合溶剂的相对组成固定时,体系的沸点与加入的盐量呈线性关系,用热力学理论导出了该线性方程,用Gibbs相律探讨了该线性关系的起因。     

药对白术-茅苍术及其单味药中挥发油成分的比较分析

采用水蒸气蒸馏法提取单味药白术、茅苍术及其药对中挥发油成分,通过气-质联用技术(GC-MS)对其分离检测,利用直观推导式演进特征投影法(HELP)分辨解析重叠色谱峰,并结合程序升温保留指数辅助定性.从白术、茅苍术及其药对中依次鉴定出29,50,62个组分,分别占各自挥发油总量的95.93%, 97 44%, 97.47%;其中20种挥发油成分共存于单味药与药对中,主要是2-(2-甲氧基)苯甲氧基苯酚、γ-芹子烯、雅槛蓝树油烯、大根香叶烯B等.组成药对后,白术减少8种组分,茅苍术减少12种组分,而药对新增22种组分,主要是单萜烯类的低沸点化合物,新增组分在药对中的作用不容忽视.     

乙二醇形成何种氢键

高中化学课本(必修)第二册第134页在叙.述乙二醇的物理性质时指出:“乙二醇是没有颜色、粘稠、有甜味的液体,沸点是198℃,熔点是-11. 50℃,密度是1.1088 g/cm3,易溶于水和乙醇。”这里的“粘稠、沸点高……”等性质很自然想到乙二醇有氢键之形成。     

Simplex优化色谱条件分离芳香族的醇、醛、酸

本实验对象是挥发性极低的苯甲醛、苯申醇、苯甲酸三组分体系。其中苯甲酸为固体,沸点250℃。文献中分析这三组分一般采用将其转变为易发挥的衍生物进行分析。 迄今只见到Kazimik在(聚丁烯醇己二酸酯 阿匹松L 磷酸)混合固定液上于     

含盐乙腈水溶液的T-P-X关系

本文采用CPⅡ型沸点仪测定了富水端乙腈-水-(KCl,CaCl₂,KI)体系在26.66～93.33kPa压力下及盐质量摩尔浓度从0.1～0.7mol·kg^-1范围内的T-P-X关系.由热力学基本原理导出含盐二元系Clausius-Clapeyron方程类型的具体形式.该方程在特定条件下可退化为各种类型的现有方程,实验结果验证了理论推导的正确性.     

气相色谱-质谱联用法结合保留指数对高良姜挥发油成分的分析

采用气相色谱-质谱联用(GC-MS)法结合保留指数(RI)对高良姜水蒸气蒸馏法(SD)、超声波辅助溶剂提取法(UAE)和亚临界流体萃取法(SFE)所制备的挥发油进行分析,分别鉴定出51,46和60个挥发性组分,并通过峰面积归一化法确定各组分的相对含量。结果表明,高良姜挥发油的指标性成分1,8-桉叶素含量的大小顺序为SD法≈SFE法UAE法,UAE法虽耗时少、能耗低,但由于所用有机溶剂难去除,所得挥发油品质较差。SFE法可得到部分SD法无法得到的化合物,如2-羟基-1,8-桉叶素、二苯基庚烷类等。另外β-石竹烯、α-石竹烯、α-法尼烯、γ-杜松烯等高沸点组分比例,SFE法所得高于另两种方法;α-蒎烯、莰烯、β-蒎烯、柠檬烯、樟脑和α-松油醇等低沸点组分比例,SD法所得最高。同一批药材不同提取方法所得的挥发油成分大部分相似,但部分成分与组分比例因不同提取方法的原理存在差异,实际生产中可根据功效需求选择不同提取方法加以开发利用。     

训练字典及其稀疏表示在近红外光谱法检测柴油中的应用

为提高柴油组分近红外法检测的精度, 提出了一种基于训练字典稀疏表示下的建模方法并用于柴油十六烷值、沸点和芳烃总量的检测. 该法先用柴油光谱结合K 均值奇异值分解(K-SVD)算法完成对冗余字典的训练, 再用正交匹配追踪算法(OMP)寻找柴油光谱在该训练字典下的稀疏表示系数, 用该系数建立了柴油十六烷值、沸点和芳烃总量偏最小二乘预测模型. 实验比对了训练字典、傅里叶字典和小波字典稀疏表示下的柴油组分预测模型性能, 其中训练字典的表示系数建模性能最优且比其他两种字典的预测性能有较大幅度改进, 验证了该法在近红外光谱检测建模领域推广能改善预测的准确度和稳健性.     

醇/水混合溶剂中碱性聚合物电解质独特的溶解行为（英文）

自聚集型季铵化聚砜(aQAPS)是一种高性能的碱性聚合物电解质(APE),已被应用于碱性聚合物电解质燃料电池(APEFCs)中。长期以来,N,N-二甲基甲酰胺(DMF)一直被作为溶解aQAPS的最佳溶剂,但DMF的高沸点使其难以彻底除尽并可能会毒化电催化剂。在我们最近的实验中发现,虽然aQAPS不能溶解于乙醇、正丙醇或水中,但它可以溶解在这些醇和水的混合物中。这种尚未被理解的独特溶解行为能够极大地促进APEFCs中膜电极组件(MEA)的制备。本工作使用分子动力学(MD)模拟的方法研究了aQAPS在不同溶剂中的溶解行为,包括水、甲醇、乙醇、正丙醇、DMF以及这些非水溶剂与水的混合物。aQAPS链在单一溶剂中的构象与其在实验中观察到的溶解行为一致,但在含有水的混合溶剂中,aQAPS链往往处于更加蜷缩的状态。模拟结果进一步揭示了混合溶剂中的水扮演着双重角色。一方面,由于疏水作用,aQAPS链在加水时被压缩至收缩状态;另一方面,水可以驱动反离子(Cl~-)的离解,从而导致溶质-溶剂相互作用能的增强,促进aQAPS的溶解。在大多数混合溶剂中,这两种相互作用的总效果是增大了总的溶质-溶剂相互作用能,在能量上有利于aQAPS的溶解。本研究不仅能够加深我们对聚电解质溶解行为的基本认识,而且对于开发性能更优的APEFCs也具有技术指导作用。     

Effect of nonvolatile solute on vapor–liquid equilibrium at fixed liquid composition

The influence of some nonvolatile solutes on boiling points of two azeotropic mixtures (1-propanol–water and methanol–tetrahydrofuran systems) was determined by means of isobaric vapor–liquid equilibrium experiments. A basic thermodynamic equation of nonvolatile solute effect on vapor–liquid equilibrium at fixed liquid composition was derived. Based on the theoretical analysis about the equation, two criterions of universal significance were obtained: (1) when a little nonvolatile solute dissolves in a binary liquid mixture with constant composition, if the vapor composition of less volatile component is increased the boiling point must be elevated at given pressure or the vapor pressure must be depressed at given temperature; (2) when a little nonvolatile solute dissolves in an azeotropic mixture, any kind of nonvolatile solute always causes the elevation of boiling point at given pressure or the depression of vapor pressure at given temperature irrespective of the variation of vapor composition. Verifying through the experiments of this paper and lot of the relevant experimental data in the literature, all of the experimental results were in agreement with both criterions without exception.     

非挥发性溶质对共沸物沸点的影响

测定了10种非挥发性溶质对甲醇-四氢呋喃共沸物沸点的影响.发现与共沸物平衡的气相组成因非挥发性溶质不同发生了不同的变化,但所有非挥发性溶质都引起共沸物沸点升高.运用热力学原理对实验结果进行了讨论.理论分析及对分析结果的实验检验表明,少量非挥发性溶质总引起共沸物沸点升高是一个具有普遍意义的结论.     

Correlation Equations for Predicting the Temperature Depression in Boiling of Aqueous Solutions of Nonvolatile Substances

Three-constant correlation equations describing the boiling point of aqueous solutions of non-volatile substances and temperature depression in boiling of the solutions under normal and arbitrary pressures are considered. The three constants appearing in the correlation equations are tabulated for aqueous solutions of 19 nonvolatile substances, and formulas for determining these constants for other aqueous solutions of nonvolatile substances from experimental data are presented.     

Liquid-vapor phase equilibrium in a tin-selenium system

Based on the pressure of the saturated vapor and components over liquid alloys in a tin-selenium system, determined using the boiling points approach (isothermal variant), its boiling point and corresponding vapor phase composition are calculated in the region of liquid solutions. The phase diagram is supple-mented with the liquid-vapor phase transition under atmospheric pressure and in vacuums of 100 and 10 Pa with the boundaries of the region in which the regions of liquid and vapor coexist being determined.     

Molecular interpretation of Trouton’s and Hildebrand’s rules for the entropy of vaporization of a liquid

The entropy of vaporization at a liquid’s boiling point is well approximated by Trouton’s rule and even more accurately by Hildebrand’s rule. A cell method is used here to calculate the entropy of vaporization for a range of liquids by subtracting the entropy of the gas from that of the liquid. The liquid’s entropy is calculated from the force magnitudes measured in a molecular dynamics simulation based on the harmonic approximation. The change in rotational entropy is not accounted for except in the case of liquid water. The predicted entropies of vaporization agree well with experiment and Trouton’s and Hildebrand’s rules for most liquids and for water except other liquids with hydrogen bonds. This supports the idea that molecular rotation is close to ideal at a liquid’s boiling point if hydrogen bonds are absent; if they are present, then the rotational entropy gain must be included. The method provides a molecular interpretation of those rules by providing an equation in terms of a molecule’s free volume in a liquid which depends on the force magnitudes. Free volumes at each liquid’s boiling point are calculated to be ～1 Å³ for liquids lacking hydrogen bonds, lower at ～0.3 Å³ for those with hydrogen bonds, and they decrease weakly with increasing molecular size.     

Sample evaporation in conventional split/splitless GC injectors. Part 3: Retaining the liquid in the vaporizing chamber

As most sample liquids tend to pass through an empty injector insert at a speed which is too high to enable complete evaporation, movement of the liquid must be arrested before it reaches the column entrance. Stopping the liquid means deposition on to a surface; this, however, is possible only after the temperature of the surface has been cooled to (or below) the boiling point of the liquid (solvent). The performance of different means of stopping the liquid has been tested visually (by the method described in Part 2). Baffles on the wall of the injector insert had hardly any effect on evaporation: the band of liquid leaving the syringe needle performed a perfect slalorn around them. The inverted cup proved more efficient, but the best performance was obtained from a light plug of glass wool: owing to its low thermal mass, the first fibers to be met by the liquid are immediately cooled to the solvent boiling point, allowing the liquid to wet it. The sample liquid is sucked up by the glass wool, from where the sample evaporates relatively slowly, often over a period of several seconds.     

On-line liquid backflush—a new technique for GC analysis of samples containing nonvolatile material

Deteriorated performance in capillary GC is often caused by the deposition of nonvolatile components in capillary GC inlets. In many cases this is a limiting factor in trace analysis of complex samples. Volatile solutes of the sample interact with the high boiling material, which leads to broadened and unsymmetrical peaks. This paper describes a novel technique which utilizes independent temperature programs of a retention gap and the column as well as a liquid backflush of the retention gap. Samples that normally contaminate the retention gap after a few injections can be repeatedly injected over extended periods of time, while the chromatographic resolution is retained.     

在不同覆盖度下二组分气体在硅胶上的吸附规律

The composition adsorption isotherms (ya~xg curve) for acetone-n-hexane, benzene-n-hexane, toluene-n-hexane and n-pentance-n-hexane vapor mixtures on silica gel with different surface coverage (θ) at 25℃ were measured. The experimental results indicated that the ya ~ xg curves approached gradually down to corresponding binary liquid-vapor equllibrium curves with increasing of surface coverage. Therefore, the binary adsorbed phases are similarly with the binary liquid phase. Except for acetone-n-hexane system, which had a minimum boiling point, the composition adsorption isotherms of the other three binary systems could be simulated by equation of relative volatility.     

Vapor–liquid equilibria of the binary mixtures formed by nitromethane with five alkyl alkanoates at 101.3 kPa

Vapor–liquid equilibria were measured at 101.3 kPa, in a range of temperatures from 350.28 to 374.69 K, for five binary mixtures formed by nitromethane with ethyl acetate, propyl acetate, isopropyl acetate, methyl propionate, and ethyl propionate. Calculations of nonideality of the vapor phase were made with Soave–Redlich–Kwong equation of state. Thermodynamic consistency of data was tested via Herington analysis. Two systems show minimum boiling azeotropes. The experimental VLE data were reduced and binary parameters for four liquid models, such as van Laar, Wilson, NRTL and UNIQUAC, were fitted. A comparison of model performances was made by using the criterion of average absolute deviations in boiling point and in vapor-phase composition.