A Colorful Catalysis Demonstration

A simple, yet colorful, homogeneous catalysis demonstration is reported. When concentrated H₂O₂ is added to a yellow-orange aqueous solution of Fe³⁺, the solution turns black in color. After a brief induction period, exothermic decomposition of H₂O₂ ensues with the evolution of oxygen gas. As the reaction subsides, the solution returns to the original yellow-orange color. These color changes demonstrate one of the most important (and often most misunderstood by first-year students) concepts of catalysis—although a catalyst may be altered as it participates in a reaction, it is not consumed.     

演示丁达尔现象的好方法

教学中通常要观察丁达尔现象必须在暗室或有暗箱,因此一般条件下不能安排演示实验。自1982年以来,我在胶体教学中一直应用氦氖激光器作为光源,利用激光束的高亮度和不易发散的特点,在明亮的教室里成功演示了胶体的丁达尔现象,实验效果非常好,即使在有阳光的屋子里,坐在教室后排的学生也能清楚地看到实验现象:在胶体溶液里有一条“光路”出现,而蒸馏水或真溶液没有光路。我将此法用于学生实验课更显得十分方便。     

自制能兼做Tyndall效应和溶液导电性实验的多用灯光屏

当前化学课堂演示实验中亟待解决的突出问题之一,是后排学生看不清实验现象。使用投影仪是解决该问题的一个较好的途径,但辅助装置不易配套,价格也较贵,一般中学不易普及。     

液态分散系中丁达尔效应的研究和实验改进

针对以高单色、高亮度红色激光作光源,一般分散系都有光散射现象,难以区分胶体和溶液这一问题,用普通白色聚光小手电筒进行了对照实验,不仅很好地区分了胶体和溶液,而且排除了蓝色溶液吸收红光所产生的干扰,通过分析一般分散系产生光散射现象的条件,得出了利用丁达尔效应区分胶体和溶液应注意的问题。并把丁达尔效应实验从气溶胶、液溶胶、固溶胶3个角度进行改进,最终得到3个改进实验：巧做气溶胶丁达尔效应实验、利用固溶胶做丁达尔效应实验、建立实验盒模式做液溶胶丁达尔效应实验。改进后的实验具有装置简单、操作简便,现象明显、节能环保等优点。     

The Raman Effect: A Large-Scale Lecture Demonstration

This article describes a lecture demonstration of the Raman effect. It presents a method for using a simple arrangement of optical components to project Raman lines from liquid samples. The Raman lines are visible as different colors of light projected on a screen several meters away. The demonstration is appropriate for physical, analytical or instrumental analysis courses.     

探究如何更清楚地观察到豆浆的丁达尔效应

豆浆中含有丰富的蛋白质,用红色激光灯在装有新制豆浆的烧杯一侧进行照射,在垂直入射光的方向观察,发现新制豆浆观察不到丁达尔效应。由于分散体系中粒子浓度较大时,粒子产生的散射光会相互干涉而抵消,依次对新制豆浆进行8、20、50、100、200、500、1 000、1 200、1 500、2 000倍的稀释后,重新观察,结果发现:在对豆浆进行2 000倍的稀释后,溶液几乎为无色时,即可以清楚地观察到丁达尔效应。     

胶原及明胶基天然高分子复合材料研究进展

胶原及其降解物—明胶是自然界中存在的一类丰富的绿色资源,来源广泛,具有可再生、可降解的"绿色"特性。将它们与其它物质复合形成新的复合材料,有着良好的性能和新的特性从而使其具有广阔的应用前景。日益严峻的环境问题,石油资源濒临匮乏,废旧材料的回收等问题使得人们更加寻求新的绿色的环境友好材料。本文根据天然资源各自的结构和性质,从复合方法和机理出发,综述了胶原及明胶与其它天然高分子(壳聚糖、淀粉、丝素蛋白、海藻酸钠)进行共混和复合以制备新的生物复合材料方面的研究进展。     

A Colorful Investigation of a Diprotic Acid: A General Chemistry Laboratory Exercise

A general chemistry laboratory experiment that can be completed in a single laboratory period is described that familiarizes students with the acid—base chemistry of a diprotic acid and with the use of visible spectroscopy to determine species concentrations. This experiment is a modified version of a previously described laboratory exercise developed for an upper-division quantitative analysis course. Students work in teams and as a class to generate different ionization states of various highly absorbing dyes. Both spectroscopic and potentiometric (pH) data is collected using LabWorks II stations, but other inexpensive pH meters and visible spectrometers (e.g., Spec 20s) are suitable. A spreadsheet template is used to determine the percent composition of various ionization states of a diprotic acid and to determine the pK_a values. Besides introducing students to fundamental tools and key chemical concepts, this laboratory is also inexpensive to operate and utilizes nontoxic, colorful solutions.     

The Effect of Gelatin on the Preparation of Silica Coated Iron Particles

A method is described for coating fine iron particles(～1μm) with a uniform silica layer,produced by the hydrolysis of tetraethyl orthosilicate.The presence of a small amount of gelatin on the surface of the iron particles facilitates this process.The X-ray photoelectron measurements indicated that the gelatin interacted with the surface of the iron particles by means of both nitrogen(in -NH2 groups) and oxygen(in -COOH groups) and then bound to the silica.The silica coating increases the resistance of the iron particles to oxidation on heating in air,which makes the temperature at which an observable oxidization occurs from 330 ℃ to 400 ℃ raised.     

The Effect of Aqueous Salt Solutions on the Melting of Collagen and the Viscosity of Gelatin

Measurements of shrinkage temperatures (T_S) for fibrous collagen, of equilibrium degree of swelling (v^?1) for the same in the amorphous state, and of intrinsic viscosity ([η]) for randomly coiled gelatin are reported. The data were obtained for a large variety of salts which are typical representatives of lyotropic series. The order of anions and cations for decreasing T_S and increasing both v^?1 and [η] (generally, for increasing salting in) is F^? < SO^2- ₄ < acetate < Cl^? < Br^? < NO^? ₃ < I^? < SCN^? and K⁺ < Mg²⁺ < Na⁺ < Cs⁺ < Li⁺ < Ca²⁺. For salts of ions at the extreme left of the series (salting-out agents) the shrinkage temperature in solutions of different salt concentration (C_S) is controlled by the amount of diluent in equilibrium swelling with the molten network, and the shape of T_S vs. C_S curves can be represented by conventional theories valid for binary polymer diluent systems based on a lattice model with a single interaction parameter. In such cases the salt-water solution behaves as a single component diluent and its effect on the measured properties is described as a diluent effect.     

用于测定络合物组成的摩尔比法原理的论证

本文将Ｂｅｅｒ定律，化学平衡原理和数学方法结合起来，较为严格地论证了摩尔比法的原理。同时证明了若以试剂空白为参化液，则无论试剂在所选定的波长λ处是否有显著的吸收，从理论上讲用该法都可得到准确的结果。     

粘度法研究明胶在聚氨酯弹性体表面的吸附

根据文献以异佛尔酮二异氰酸酯（IPDI）为原料制备了具有较好机械性能的聚氨酯弹性体胶条（PU）,并在胶条表面接枝肝素,得到肝素化聚氨酯胶条（PU-Hep）。将聚氨酯胶条浸泡在明胶稀溶液中,测量溶液粘度随时间、溶液浓度和温度的变化,并采用具有界面校正的粘度方程从实验相对粘度数据计算明胶在聚氨酯表面的吸附量。研究发现明胶分...     

Effect of Coconut Protein and Xanthan Gum,Soybean Polysaccharide and Gelatin Interactions in Oil-Water Interface

We report on our study of the interactions between coconut protein extracted from coconut meat and three hydrocolloids (gelatin, xanthan gum, and soybean polysaccharide) and their interfacial adsorption and emulsification properties. We used Zeta potential, fluorescence spectroscopy scanning and ITC to investigate the interactions between a fixed concentration (1%) of coconut protein and varying concentrations of hydrocolloid. Through the interfacial tension and interfacial viscoelasticity, the interfacial properties of the hydrocolloid and coconut protein composite solution were explored. The physical stability of the corresponding emulsion is predicted through microstructure and stability analysis. Xanthan gum forms a flocculent complex with coconut protein under acidic conditions. Soy polysaccharides specifically bind to coconut protein. Under acidic conditions, this complex is stabilized through the steric hindrance of soy polysaccharides. Due to gelatin-coconut protein interactions, the isoelectric point of this complex changes. The interfacial tension results show that as time increases, the interfacial tensions of the three composite solutions decrease. The increase in the concentration of xanthan gum makes the interfacial tension decrease first and then increase. The addition of soybean polysaccharides reduces the interfacial tension of coconut protein. The addition of xanthan gum forms a stronger elastic interface film. Emulsion characterization showed that the gelatin-added system showed better stability. However, the addition of xanthan gum caused stratification quickly, and the addition of soybean polysaccharides also led to instability because the addition of polysaccharides led to a decrease in thermodynamic compatibility. This research lays the foundation for future research into coconut milk production technology.     

明胶/卤化银乳剂体系正电子湮没研究

长期以来,显影过程特别是银丝的生成机理一直是感光工作者关注和研究的焦点.但迄今为止,众说纷坛的各种假说尚未达到共识,本文用正电子湮没技术 (PAT)测定了乳剂的正电子湮没寿命谱,探讨了银丝在自由体积空穴中的生长机理,并采用透射电子显微镜观察除去明胶后的银丝形貌,验证了PAT实验中银丝生长的结论.同时本文根据明胶中蛋氨酸及其氧化产物的大致含量,首次采用正电子湮没技术 (PAT)研究将蛋氨酸及其氧化产物加到照相乳剂中,观察蛋氨酸及其氧化产物的还原性以及在水洗前加入蛋氨酸和在水洗后加入蛋氨酸的差别.     

核外电子运动的象征性演示

原理：人的视觉暂留现象。器材：电风扇一台、镊子一把、剪子一把、红纸、浆糊。操作：剪取1cm2左右的一小方块红纸,在背面涂上一薄层浆糊,用镊子夹着,将它贴在擦去灰尘的电风扇一扇叶的边缘,开启电风并让它“摇头”。     

过氧化钠生成的演示实验

高中化学课本中关于钠在空气里燃烧生成过氧化钠的实验,只有“把小块钠放在石棉网上加热,观察发生的变化。”一句,给人的印象是,这个实验非常简单,然而事实上远非如此轻而易举。     

酸预处理对酶法骨明胶功能性质和分子质量分布的影响

本文以牛骨粉为原料,采用酶解法制备明胶,考察了骨粉预处理试剂——盐酸的浓度对明胶产品的冻力、粘度、分子量分布和等电点的影响.研究表明,随着骨粉预处理用的盐酸浓度的增大,明胶产率降低.骨粉经过盐酸预处理后,明胶产品的冻力大于300 bloom g,高于原料未经盐酸处理得到的明胶产品.与传统的碱法工艺明胶相比,酶法明胶具有高冻力、高等电点和相对较低的粘度等特点.采用聚丙烯酰胺凝胶电泳表征明胶的分子质量分布,酶法明胶不但具有传统碱法明胶具有的96 KDa、97 KDa、193 KDa和289 KDa组分,而且具有165 KDa和120 KDa组分.酶法明胶的等电点在碱性范围内,随着预处理用盐酸浓度的增大,明胶产品的等电点升高.骨料的预处理工艺对明胶的产率、冻力、粘度、等电点和分子质量分布有重要的影响,在明胶制备过程中,通过调控骨料预处理酸浓度可以调控明胶的技术指标.     

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

Antiaromatic species are substantially less thermodynamically stable than aromatic moieties. Herein, we report the stabilization of two classical antiaromatic frameworks, cyclobutadiene and pentalene, by introducing one metal fragment through the first [2+2] cycloaddition reaction of a late‐transition‐metal carbyne with alkynes. Experimental observations and theoretical calculations reveal that the metal fragment decreases the antiaromaticity in cyclobutadiene and pentalene simultaneously, leading to air‐ and moisture‐stable products. These molecules show broad absorption from the UV to the near‐IR region, resulting in photoacoustic and photothermal effects for metalla‐aromatic compounds for the first time. These results will encourage further efforts into the exploration of organometallic compounds for photoacoustic‐imaging‐guided photothermal therapy.