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物理化学实验装置改进点滴 总被引:1,自引:0,他引:1
几年来,我室对物理化学实验装置进行了一些改进;这些改进虽小,但在教学实践中收到了良好的效果。现就液体饱和蒸汽压的测定、表面张力测定两实验改进前后的情况对比加以说明。 相似文献
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应用Excel对数据进行作图、线性拟合、非线性曲线拟合等处理,以测定液体表面张力实验数据的处理为例,介绍Excel软件在物理化学实验数据处理中的具体操作方法. 相似文献
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在298.15~338.15 K 0.1 MPa工况下测定了离子液体1-乙基-3-甲基咪唑双三氟甲磺酰亚胺盐([emim][Tf_2N])的表面张力、密度、黏度及电导率;采用最小二乘法拟合了实验数据,得到了表面张力和密度随温度的回归方程;在相同工况下,同其他实验数据以及采用基团贡献法得到的数据进行了对比;同时,研究了相关物性参数同离子液体结构和温度的关系。研究结果表明:离子液体的表面张力随阳离子取代基碳链长度的增大而减小,随阴离子尺寸的增加而减小;其表面张力和密度随温度的升高均呈线性减小变化;黏度随着温度的升高逐渐降低;电导率随着温度的升高而增大。以上物性的测定和研究,填补了离子液体[emim][Tf_2N]相关物性参数的空白,同时也为该种离子液体的应用,尤其是在吸收式制冷系统中的应用,提供了参考。 相似文献
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新型功能性离子液体[emim]Ac吸收CO_2性能良好,但物性研究匮乏。在298.15—338.15 K温度范围内测定了离子液体[emim]Ac的黏度和表面张力及308.15—428.15 K温度范围内的比热容。结果表明:当压力一定时,离子液体[emim]Ac的黏度和表面张力均随温度的升高逐渐减小;比热容随温度的升高先减小后逐渐增大;分别采用Litovitz方程和Eotvos方程进行黏度、表面张力数据的关联,比热容与温度的关联式符合温度的N次函数,得出平均相对偏差分别为:0.04%,1.11%,3.53%,理论关联与实验测定结果一致。通过研究补充了离子液体[emim]Ac的相关物性,验证了模型关联对离子液体基础物性关联的可行性。 相似文献
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<正> 表面张力是液体的最基本性质,涉及广泛的表面现象。表面张力测定的方法极多,但测得数值的准确度除了决定于实验误差外,很大程度决定于从实验观察到的数据来计算表面张力的数学分析是否成功。本文推荐了Bashforth-Adams 方法。该方法所用的基本公式是Lapalace 方程,这是因为我们实际所要解决的对象多是液体曲面,而且这些曲面都是轴对称的。Lapalace 方程的具体形式为: 相似文献
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使用高速相机研究了表面张力变化对含气泡液体射流破裂过程的影响。通过改变表面活性剂浓度获得了不同表面张力的液体射流。实验发现当液体射流速度保持不变时,减小液体表面张力会增加射流破裂长度。表面活性剂一方面降低了液体动态表面张力,减小了射流表面不稳定波的增长率,增大了射流破裂长度;另一方面表面活性剂在射流表面的非均匀分布会产生Marangoni应力,促使液体向射流变形区运动,从而推迟了射流破裂的发生,增大了射流破裂长度。通过理论分析得到了液体射流破裂长度表达式。发现射流内部气泡会显著缩短含表面活性剂射流的破裂长度。通过气泡扰动射流速度和吸附表面活性剂的分析,揭示了内部气泡对含表面活性剂射流破裂的影响规律。 相似文献
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The question of the reliability of the electrocapillary technique for measurement of relative changes of surface tension is investigated for the case of aqueous. 0·03N NaClO4 and for solutions containing the rigid symmetrical molecule pyrazine. Surface tension and adsorption measurements have been made by drop-time and electrocapillary techniques. Only very small differences of surface tension changes, due to adsorption of pyrazine at various electrode charges, can be detected between the two methods. The surface excess/chemical potential relations derived from the results of the two methods are almost identical. It is concluded that systematic errors in the study of electrochemical adsorption by the electrocapillary method do not normally arise. 相似文献
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Cecil A. W. Allen K. Chris Watts Robert G. Ackman 《Journal of the American Oil Chemists' Society》1999,76(3):317-323
The emergence of biodiesel fuels as diesel fuel substitutes has led to several studies on their properties. Surface tension,
which plays a role in atomization, has lacked attention compared to other properties. This paper presents a method to predict
the surface tension of biodiesel fuels based on the fatty acid composition. Several binary, ternary, and quaternary mixtures
of fatty acid ethyl ester gas chromatographic (GC) standards were prepared, and we found that a mass-average equation predicted
the surface tension of these mixtures within ±3.5% of their measured values. Six complex mixtures of fatty acid methyl ester
GC standards that simulated typical oils used as biodiesel fuels were also prepared. For these complex mixtures the predicted
surface tensions of the mixtures, calculated from a mass-average equation, were 2–6% higher than the measured values. A mass-average
equation was developed in which we used a weighted surface tension for the individual components, and we found that this method
predicted the surface tension of the simulated oils within ±4.5% of their measured values. Five natural vegetable oils were
used to produce biodiesel fuels by the transesterification process. The predicted surface tensions of these fuels were all
within ±3.5% of their measured values. The surface tensions of 15 biodiesel types were then predicted, based on their fatty
acid composition as published in the literature. These results show that the differences in surface tension between biodiesel
types are not the main cause of the reported differences in engine tests. 相似文献
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Surface tension is a parameter of decisive importance for characterizing painted and unpainted surfaces related to wetting and adhesion phenomena. Measurements of the surface tension of solids by means of an automatic contact angle measurement device are presented. The theoretical evaluations provide for a separation of the surface tension into polar and disperse components. In addition, this paper briefly touches on other more far-reaching approaches (acid/base) and discusses a method for the determination of the dynamic surface tension of liquids. 相似文献
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《Diamond and Related Materials》2001,10(3-7):781-785
Wettability of HF-CVD diamond films grown in different conditions has been investigated. Wettability depends on surface tension: solids with high surface tension, as diamond, should be hydrophilic, while solids with low surface tension should be hydrophobic. In spite of these arguments, natural diamond exhibits a moderate hydrophobicity [J. Coll. Inter. Sci. 130 (1999) 35], depending on surface termination (hydrogen or oxygen terminated). In this work we find that CVD diamond films show wettability behaviours ranging from a small, up to clear hydrophobicity, probably according to surface carbon termination functionalities. Wettability does not seem to be influenced by characteristics as film structural morphology or growth orientation direction, which were analysed by SEM, while it seems dependent on surface reconstruction, as detected by Raman and XPS analysis. Moreover, in contrast with natural diamond [J. Coll. Inter. Sci. 130 (1999) 35] we found an enhancement to water wettability when CVD diamond films were treated in a hot filament activated hydrogen atmosphere. We argue that this effect may be due to the hydrogen etching of reconstructed surface layers with lower surface tension. 相似文献
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On the measurement of critical micelle concentrations of pure and technical-grade nonionic surfactants 总被引:1,自引:0,他引:1
A. Patist S. S. Bhagwat K. W. Penfield P. Aikens D. O. Shah 《Journal of surfactants and detergents》2000,3(1):53-58
The critical micelle concentrations (CMC) of nine commercial nonionic surfactants (Tween 20, 22, 40, 60, and 80; Triton X-100;
Brij 35, 58, and 78) and two pure nonionics [C12(EO)5 and C12(EO)8] were determined by surface tension and dye micellization methods. Commercially available nonionic surfactants (technical
grade) usually contain impurities and have a broad molecular weight distribution owing to the degree of ethoxylation. It was
shown that the surface tension method (Wilhelmy plate) is very sensitive to the presence of impurities. Much lower CMC values
were obtained with the surface tension method than with the dye micellization method (up to 6.5 times for Tween 22). In the
presence of highly surfaceactive impurities, the air/liquid interface is already saturated at concentrations well below the
true CMC, leading to a wrong interpretation of the break in the curve of surface tension (γ) vs. concentration of nonionic
surfactant (log C). The actual onset of micellization happens at higher concentrations, as measured by the dye micellization
method. Furthermore, it was shown that when a commercial surfactant sample (Tween 20) is subjected to foam fractionation,
thereby removing species with higher surface activity, the sample yields almost the same CMC values as measured by surface
tension and dye micellization methods. It was found that for monodisperse pure nonionic surfactants, both CMC determination
methods yield the same results. Therefore, this study indicates that precaution should be taken when determining the CMC of
commercial nonionic surfactants by the surface tension method, as it indicates the surface concentration of all surface-active
species at the surface only, whereas the dye method indicates the presence of micelles in the bulk solution. 相似文献
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The present work proposed a modified technique of the forming bubble method for measuring surface tension, and compared surface
tension data by this method with other reported data. This method shows an applicability to the study of surface aging effect
in a surfactant system. 相似文献
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Successive foam fractionation has been used to divide a processed calcium lignosulphonate into tractions differing appreciably in surface activity. Static surface tension has been measured by the de Nouy tensiometer and surface tension aging by the sessile bubble (photographic) method. The effect of concentration on surface tension has been determined. The effect of pH at 1% concentration on dynamic surface tension has been determined on freshly prepared solutions. 相似文献