化学实验法教学

实验和观察是化学知识的主要源泉,概念和定律、理论是在实验中试验、研究、发现的。所以,按照逻辑规律的同一律,进行化学“实验——启发——抽象”教学,是获得化学概念、定律、理论最常见的程序。例如,“质量守恒定律”的教学,是通过实验、观察,应用推理判断、归纳演绎等逻辑方法得到的:参加反应的各物质的质量总和。

现代物理化学实验方法在混合乳干酪品质分析上的应用

对部分豆乳替代牛乳的混合乳干酪进行了微观显微结构和宏观质构分析，并由此分析了影响混合乳干酪品质的因素。扫描电子显微镜显示的两种干酪的照片表明，纯牛乳干酪具有纤细、致密的网状结构，而混合乳干酪的显微结构较为疏松，包含大小不一的空穴，加热变性后的大豆球蛋白粘附于纤维状酪蛋白分子束结构上。此外，差热扫描分析仪对皱胃酶的热分析表明，粗制皱胃酶的热变性温度约在９５℃左右。酶的热变性－失活实验表明，皱胃酶含耐热和不耐热两部分，在８１℃时，其失活速度分别是６．３３×１０（－２）ｓ（－１）和１．６６７５ｓ（－１）。

化学教学法实验课的改革

“化学是一门实验科学”。化学学科本身的发展和化学人才的培养都与实验紧密相关。“化学实验课是实施全面化学教育的一种最有效的教学形式”。因此,加强实验教学环节,是带根本性的教育改革。“以实验为基础是中学化学教学的最根本特征。”结合我校的培养目标,采用“

高中化学科学方法教育的内容、现状及实施建议

我国著名化学教育家陈耀亭先生提出在化学教学领域使用以自然科学为基础的科学方法教育,尽管我国在化学教育教学中应用科学方法教育的尝试已经有一段时间了,但是在实际的化学教育教学中成果并不是很明显,且尚未真正全面落实,原因是多方面的:首先,科学方法教育的内容体系和目标具有不确定性,在实施过程中缺乏计划性、系统性,导致实施过程中的盲目性很大,所以实效性很小,收效甚微。其次,我国对这种化学教育方法的专门研究机构很少。

掺伪食品中罂粟壳的纸层色谱测定法

在火锅、肉汤等食品中违法添加罂粟壳的事件时有发生,为了探索适于基层的快速简易的测定方法,我们筛选了仪器分析法、化学实验法、色谱法、显微细胞鉴别法,认为纸层色谱法简便易行,兹介绍如下。 1 测定方法 1.1 样品处理: 取样品20～30g,加50～60ml 1％HCl在沸水浴上浸渍1h,浸渍过程中摇动5次,冷却,过滤,将滤液置分液漏斗中加石油醚25ml提取一次,弃去石油醚。用碱液将样品的pH值调至9.0,用适量氯仿提取样品,合并提取液,通过无水硫酸钠柱脱水。

改变药典规定波长实现吡嗪酰胺片溶出度的在线过程分析

目的研究一种实时、在位监测药物固体制剂体外溶出度的测定方法———光纤化学药物溶出度过程实验法,考察本方法与《中国药典》2000版溶出度测定方法的差异。方法将双分支光纤分别连接光源和检测器,光纤公共端部直接插入溶出杯中,检测药物溶出度,通过改变药典规定吡嗪酰胺的测试波长,实现溶出度过程分析。结果方法学考察吡嗪酰胺在310nm处,浓度在60.00～280.00mg·L-1范围内吸收度与浓度成线性,r=0.9999,日内日间精密度为0.8%和1.1%(n=6),平均回收率97.8%,实现检测吡嗪酰胺溶出度,可直接从溶出曲线上提取相关参数,与《中国药典》2000版溶出度测定方法比较,两种测定方法无统计学意义(P>0.05)。结论光纤化学药物溶出度过程实验法通过改变吡嗪酰胺测试波长,不经过滤稀释,获得药物在体外的溶出曲线,数据信息完整。

ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ON ATTAPULGITE

Batch adsorption experiments were carried out for the removal of methylene blue (MB) from aqueous solution using attapulgite as adsorbent. The effects of various parameters such as temperature, contact time, the pH value, and attapulgite dosage on the adsorption performance were investigated. The standard curve and regression equation were established by spectrophotometry. The adsorption experimental results showed that the adsorption equilibrium data were well in accord with Langmuir adsorptive model. The optimal result was acquired under the experimental condition of attapulgite dosage 0.18g, MB concentration 50.0mg/L, pH 10, and adsorption time 20min at room temperature.

Reaction mechanism of molten Na OH decomposing Zn_2SiO_4 in willemite

Based on the existing form of Zn2 Si O4 in willemite, the chemical precipitation method was used to synthesize Zn2 Si O4.Through the orthogonal experimentation, the reaction conditions of melten Na OH decomposing Zn2 Si O4 were optimized, and the optimal experimental conditions include reaction temperature of 400 °C, reaction time of 4 h, and alkaline-to-ore molar ratio of 20:1.Based on the optimized experiment, on-line detection for the alkali leaching was made by using Raman spectroscopy; XRD was used to analyze the structure of water leaching residue, to explore the reaction mechanism of Na OH decomposing Zn2 Si O4. The results show that during the reaction process, the Si — O bond in Si O4 is destroyed, and the Na OH inserts itself into the silicate lattice,producing an immediate Na2 Zn Si O4 product. After the alkali leaching process, Zn2+ can be separated from the Si O4 array, which can be released out of the silicate in the form of ZnO.

高中化学课堂有效性教学的实践与思考

传统的高中化学教学模式存在一定的弊端,不适应新课标教学要求。为了突破传统教学模式的束缚,激发学生的学习热情,增强学生的自主探究能力,增添课堂活力,提高教学质量和效益,化学教育者需要做坚持不懈的努力,采取各种办法提高课堂教学的有效性。

盐类水解的生活化实验引入

盐类水解是化学反应原理中非常重要的一节内容,是学生在学习了强弱电解质和水的电离基础上学习的内容。从初中开始学化学的时候,我们总说酸碱中和反应生成盐和水,给学生造成一个错误印象,既然酸碱中和生成盐和水,水是中性,所以盐也应该是中性的。但生活中我们蒸馒头用的碱面,我们叫做"碱",主要化学成分是Na2CO3,从化学组成来看属于盐,学生在此就很困惑,为什么明明属于盐,生活中我们却要称其"碱"呢?

不同检验方法对慢性肝病的检验结果分析

目的研究慢性肝病应用不同检验方法对检验结果所产生的影响,供临床借鉴。方法以本院接诊的慢性肝病患者90例为研究对象,将之利用奇偶数字分组的方式分成3组,对每组都实行血清检验,当中,A组(n=30)采用PCR检测法,B组(n=30)采用胶体金层析法,C组(n=30)采用免疫化学发光实验法。综合分析3组的检验结果,并对各组的肝病阳性检出率和患者满意度作出比较。结果A组的阳性检出率为96.67%,比B组的73.33%以及C组的80.0%高(P <0.05)。A组的患者满意度为96.67%,优于B组的80.0%以及C组的83.33%(P<0.05)。B、C两组的阳性检出率和患者满意度比较无显著差异,P>0.05。结论选择PCR检测法,并将之积极用于慢性肝病中,可显著提高阳性检出率,且能为早期诊断慢性肝病提供重要指导,建议推广和使用。

Synthesis and characterization of an environmentally friendly PHBV/PEG copolymer network as a phase change material

Novel environmentally friendly poly（hydroxybutyrate-co-hydroxyvalerate） and poly（ethylene glycol） （PHBV/PEG） copolymer networks were synthesized through free-radical solution polymerization with PHBV diacrylate （PHBVDA） and polyethylene glycol diacrylate （PEGDA） as macromers. The molecular structure of PHBV/PEG copolymer network was characterized by Fourier transform infrared （FT-IR） and 1H nuclear magnetic resonance （1H NMR）. The morphology of the PHBV/PEG co- polymer network was characterized by polarization optical microscopy. Thermal energy storage properties, thermal reliability and thermal stability were investigated by differential scanning calorimetry （DSC） and thermogravimetric analysis. The results indicated that the PHBV/PEG copolymer network hindered the growth of PEG crystalline segments or PHBV segments. PHBV/PEG copolymer network had a higher latent heat enthalpy, which didn＇t reduce with the components of PHBV in- creased. Moreover, PHBV/PEG copolymer network still had good thermal stability even at 300 ~C. These results suggested that such environmentally friendly copolymer network would have wide applications in phase change energy storage materials.

Synthesis of aminoalkylsilanes with oligo(ethylene oxide) unit as multifunctional electrolyte additives for lithium-ion batteries

Aminoalkylsilanes with oligo(ethylene oxide) units were designed and synthesized as multifunctional electrolyte additives for lithium-ion batteries. The chemical structures were fully characterized by nuclear magnetic resonance (NMR) spectroscopy and their thermal properties, viscosities, electrochemical windows, and ionic conductivities were systematically measured. With adding one of these compounds (1 vol. %, DSC3N1) in the baseline electrolyte 1.0 M LiPF 6 in EC: DEC (1:1, in volume), Li/LiCoO 2 half cell tests showed an improved cyclability after 100 cycles and improved rate capability at 5C rate condition. Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopic (EDS) analysis confirmed the acid scavenging function and film forming capability of DSC3N1. These results demonstrated that the multifunctional organosilicon compounds have considerable potential as additives for use in lithium-ion batteries.

A further understanding of the cation exchange mechanism for the extraction of Sr^(2+) and Cs^+ by ionic liquid

The cation exchange mechanism was further investigated during the extraction of Sr 2+ and Cs+ using the extractant dicyclo- hexano-18-crown-6 (DCH18C6) in an ionic liquid (IL)1-ethyl-3-methyimidazolium bis[(trifluoromethyl)sulfonyl]imide (C2 mimNTf2 ). The concentrations of both the cation C2 mim + and the anion NTf2 in aqueous phase were detected. The con-centration of NTf2 in the aqueous phase decreased as Sr2+ or Cs+ exchanged into the IL phase. Addition of C2 mim + or NTf2 as well as the variation of the solubility of C2 mimNTf2 influenced the extraction efficiency of Sr2+ or Cs+ .

Electrooxidation of hydroquinone on simply prepared Au-Pt bimetallic nanoparticles

A facile method was used to prepare gold-platinum （Au-Pt） catalysts by direct electrodeposition via cyclic voltammetry in an acidic medium. Various parameters that affect the properties of electrodeposited catalysts were investigated such as initial ap- plied potential, scan rate and deposition time. Initial applied potential plays a more important role in the preparation of bime- tallic nanoparticles （AuPtNPs） since the kinetics of electrodeposition is in competition with the rate of hydrogen evolution. The AuPtNPs electrodeposited on pencil graphite （PG） were used to study the electrooxidation of hydroquinone. Various parame- ters such as pH, scan rate, concentration of hydroquinone and temperature were studied in the electrooxidation process. Ap- parent activation energy （Ea） for the electrooxidation of hydroquinone, calculated from the Arrhenius plot, shows that AuPtNPs catalysts （electrodeposited on the PG） offer less activation energy （ca. 9.500 kJ mo1-1） than the bare PG （ca. 10.345 kJ mol-1）. The AuPtNPs/PG shows better catalytic performance than the PG electrode due to the greater surface area it provides, thus re- sulting in more active sites available for adsorption of hydroquinone molecules on the surface of the catalyst.

Approach to lattice-related/content-specific spectral ranges of near-infrared diffuse reflectance spectroscopy of cefazolin sodium and the construction of a quantitative model for the determination of cefazolin sodium content in different crystal forms

Cefazolin sodium can form both α- and β-form crystals. It also can form dehydrated crystalline and amorphous products through different production processes. Because different polymorphic medicines usually have different physical and chemical properties, it is critical to emphasize the crystallization control of polymorphic medicines. Near-infrared （NIR） analysis, which incorporates a combination of NIR spectroscopic techniques and multivariate chemometric methods, is considered a powerful tool for the determination of the crystallinity of polymorphic drugs. The selection of optimal spectral ranges that correlate with the lattice specificity and content specificity is crucial to obtaining a specific NIR model. In the present work, near-infrared （NIR） spectra of cefazolin sodium with different crystal forms created through different processes were studied. The results suggest that wavelengths within the range of 9102.7-8597.5 cm-1 is related to the specificity of the cefazolin sodium crystal lattice and that the range of 6001.6-5496.4 cm i is associated with the quantitative content of cefazolin sodium. The two ab- sorptions are caused by the second overtone of the C-H stretching band （3nC-H） and the first overtone of C-H stretching band （2uC-H）, respectively. Using these results, we established a suitable method of constructing a universal quantitative model by using mixed samples in different crystal forms as a calibration set, selecting a content-specific range （6001.6-5496.4 cm-l）, and adding lattice-related spectral ranges where appropriate. This may provide a framework for the construction of prediction models for polymorphic medicines.

Photoelectrochemical performance of a sub-micron structured film with poly(3-methylthiophene) (P3MT)-modified CdTe/ZnO shell-core sub-micron tube arrays

A sub-micron structured film with a poly(3-methylthiophene) (P3MT)-modified CdTe/ZnO shell-core sub-micron tube array has been prepared by a series of electrodeposition processes, and a semiconductor-sensitized solar cell based on this structure was also fabricated. Vertically oriented ZnO sub-micron tubes were obtained on an indium tin oxide (ITO) substrate, and then CdTe nanocrystals and a thin P3MT layer were electrodeposited sequentially onto the walls of the ZnO sub-micron tubes. A suitable thickness of CdTe and P3MT could improve the photovoltaic properties of the solar cell, which was attributed to the enhancement in the light absorption and the decrease in the recombination of photogenerated carriers. In addition, a p–n heterojunction formed between the interface of CdTe and P3MT played an important part in the efficient separation and fast transport of photogenerated carriers in the sub-micron structure. A power conversion efficiency of 1.20% was obtained with this type of solar cell.

Properties of a water layer on hydrophilic and hydrophobic self-assembled monolayer surfaces: A molecular dynamics study

The microscopic behaviors of a water layer on different monolayers （SAMs） are studied by molecular dynamics hydrophilic and hydrophobic surfaces of well ordered self-assembled simulations. The SAMs consist of 18-carbon alkyl chains bound to a silicon（111） substrate, and the characteristic of its surface is tuned from hydrophobic to hydrophilic by using different terminal functional groups （-CH3, -COOH）. In the simulation, the properties of water membranes adjacent to the surfaces of SAMs were reported by comparing pure water in mobility, structure, and orientational ordering of water molecules. The results sug- gest that the mobility of water molecules adjacent to hydrophilic surface becomes weaker and the molecules have a better or- dering. The distribution of hydrogen bonds indicates that the number of water-water hydrogen bonds per water molecule tends to be lower. However, the mobility of water molecules and distribution of hydrogen bonds of a water membrane in hydropho- bic system are nearly the same as those in pure water system. In addition, hydrogen bonds are mainly formed between the hy- droxyl of the COOH group and water molecules in a hydrophilic system, which is helpful in understanding the structure of in- terfacial water.

Coulometric sizing of nanoparticles： Cathodic and anodic impact experiments open two independent routes to electrochemical sizing of Fez04 nanoparticles

Anodic particle coulometry （APC） is a recently established method of sizing individual metal nanoparticles by oxidising them during their impact on a micro electrode. Here it is demonstrated that the application of APC can be extended to sizing of metal oxide nanoparticles, such as Fe304 magnetite nanoparticles. Additionally, a new route to electrochemical nanoparticle sizing is introduced-- cathodic particle coulometry （CPC）. This method uses the reduction of impacting nanoparticles, e.g., metal oxide nanoparticles, and is demonstrated to yield correct size information for Fe304 nanoparticles. The combination of these two independent electrochemical methods of nanoparticle sizing, allows for purely electrochemical sizing of single nanoparticles and simultaneous verification of the obtained results.

Mercuric ions induced aggregation of gold nanoparticles as investigated by localized surface plasmon resonance light scattering and dynamic light scattering techniques

With the development of nanosciences, both localized surface plasmon resonance light scattering （LSPR-LS） and dynamic light scattering （DLS） techniques have been widely used for quantitative purposes with high sensitivity. In this contribution, we make a comparison of the two light scattering techniques by employing gold nanoparticles （AuNPs） aggregation induced by mercuric ions. It was found that citrate-stabilized AuNPs got aggregated in aqueous medium in the presence of mercuric ions through a chelation process, resulting in greatly enhanced LSPR-LS signals and increased hydrodynamic diameter. The enhanced LSPR-LS intensity （A/） is proportional to the concentration of mercuric ions in the range of 0.4-2.5 laM following the linear regression equation of A/= -84.7＋516.4c, with the correlation coefficient of 0.983 （n = 6） and the limit of determi- nation （3o-） about 0.10 gM. On the other hand, the increased hydrodynamic diameter can be identified by the DLS signals only with a concentration of Hg2＋ in the range of 1.0-2.5 gM, and a linear relationship between the average hydrodynamic diame- ters of the resulted aggregates and the concentration of Hg2＋ can be expressed as d = -6.16 ＋ 45.9c with the correlation coeffi- cient of 0.994. In such case, LSPR-LS signals were further applied to the selective determination of mercuric ions in lake water samples with high sensitivity and simple operation.