以“准确”为中心思想的滴定分析体系

将滴定分析的准确分为实验设计的准确和实验测定的准确两部分.进而将滴定分析工具分为硬性工具和软性工具,前者为实物性测量工具,后者为滴定分析所涉及的化学反应.最后指出滴定终点误差实质上是相对误差在滴定分析中的具体体现,其值的大小由测定对象的数量、测量工具的优劣以及软性工具的读数误差等3个因素决定,并统一于从形式上类似的林邦公式.     

“中和滴定”知识的产生与发展及其教学价值

“中和滴定”知识有其自身的产生和发展顺序,结合滴定分析法的产生和发展、指示剂的发现、滴定管的发明及改进等史实,能够引导学生认识知识的建构过程,也有助于培养学生的科学态度和创新意识,发展学生的化学学科核心素养。     

“亲水”材料未必“疏油”

材料的亲液性 (亲水或亲油 )是许多领域对材料特性考察的一个重要方面。如纤维的亲水性与纤维制品的服用性能有密切关系 ,亲水性纤维制成的内衣能增加穿着舒适感[1] ;又如 ,在膜分离的核心技术———反渗透 (ＲＯ)、超滤 (ＵＦ)和微滤 (ＭＦ)中 ,采用具有亲水性表面的膜能显著减少膜污染 ,延长膜的使用寿命[2 ] ;此外 ,填料床中的填料以及浮选过程中的矿粒等的亲液性都对相关过程影响重大。　　对于材料的亲液性 ,不少人有这样一种认识 ,即亲水的材料必定是疏油的 ,反之亦然。但仔细考察材料亲水亲油现象发生的本质 ,就会发现并非任何材料都…     

“教学研究与改革”栏目指导我们求“新”求“精”

《大学化学》促我成长十年来，我和周围的同仁们一样，是《大学化学》的忠实读者。在我的有机化学教研生涯中，《大学化学》是我的良师益友。《大学化学》的十年，正是我成长的十年。十年来，我从中受益匪浅，使我不断地充实、提高、成长。我几乎对《大学化学》中发表的每...     

近年物理化学滴定进展

评述了近五年国内外物理化学滴定（用作图确定终点）的新进展，内容包括：（１）光学滴定（含光度、荧光、磷光、化学发光滴定）；（２）电滴定（含电位、电导、电流、库仑滴定）；（３）量热滴定。每类滴定均再按滴定用介质分为水介质和非水介质滴定，按滴定反应分为酸－碱、氧化－还原、络合、沉淀滴定，按滴定方式分为直接滴定、代滴、回滴。引用文献１０６篇。     

线上线下混合模式在药学专业分析化学教学中的应用*——以“酸碱滴定分析法”为例

以“酸碱滴定分析法”为例,依托自建药学专业SPOC课程资源,构建和实践了包含前端分析、教学过程和考核评价的线上线下混合教学模式。通过全面分析教学内容、教学目标、学情和学习环境等,设计了线上课前预习、线下课堂教学、线上课后拓展等3个步骤相衔接的教学过程,建立了线上线下相结合、突出过程性评价的综合考核方式。通过反思整个教学过程,对线上线下混合教学模式的主要优势和问题进行了讨论。     

关于滴定方式的讨论

指出某些教材中滴定方式分类的不当之处;讨论了置换滴定和间接滴定的区别以及置换滴定和置换反应的联系与区别。     

广义氧化还原滴定

根据广义氧化还原新概念 ,提出了广义氧化还原滴定。广义氧化还原滴定包括酸碱滴定、沉淀滴定、配位滴定和氧化还原滴定。它们的滴定曲线可以由相同的原理绘出     

多元弱酸的准确滴定

用二元弱酸滴定的林邦滴定曲线方程推导第一和第二滴定突跃绝对值,用第一和第二滴定突跃绝对值推导二元弱酸第一和第二级解离的H+准确滴定的条件,并将其应用于多元弱酸的准确滴定.     

沉淀滴定终点误差的计算公式

滴定分析中的终点误差计算,学者们在配位滴定、酸碱滴定中多采用林邦误差公式,陶德祥等在氧化还原滴定中也推导出类似公式。本文就林邦误差公式在沉淀滴定中的应用进行了探讨,推导出了林邦误差公式形式表示的沉淀滴定终点误差计算公式,现介     

Isolation and identification of the anti-isohumulones and the anti-acetylhumulinic acids

The anti-isohumulones [5-(3-methylbutanoyl)-2-(3-methylbut-2-enyl)-4-hydroxy-4-(4-methylpent-3-enoyl)-cyclopentane-1,3-diones] and the anti-acetylhumulinic acids [5-(3-methylbutanoyl)-2-(3-methylbut-2-enyl)-4-ethanoyl-4-hydroxy-cyclopentane 1,3-diones] have been isolated from an isomerisation reaction mixture of humulone [2-(3-methylbutanoyl)-4,6-di(3-methylbut-2-enyl)-6-hydroxy-cyclohexane-l,3,5-trione] by counter-current distribution and identified by spectroscopic techniques. The formation mechanism is presented and the stereochemical consequences are discussed. The anti-isohumulones are the most bitter hop compounds presently known.     

The energy pump and the origin of the non-equilibrium flux of the dynamical systems and the networks

The global stability of dynamical systems and networks is still challenging to study. We developed a landscape and flux framework to explore the global stability. The potential landscape is directly linked to the steady state probability distribution of the non-equilibrium dynamical systems which can be used to study the global stability. The steady state probability flux together with the landscape gradient determines the dynamics of the system. The non-zero probability flux implies the breaking down of the detailed balance which is a quantitative signature of the systems being in non-equilibrium states. We investigated the dynamics of several systems from monostability to limit cycle and explored the microscopic origin of the probability flux. We discovered that the origin of the probability flux is due to the non-equilibrium conditions on the concentrations resulting energy input acting like non-equilibrium pump or battery to the system. Another interesting behavior we uncovered is that the probabilistic flux is closely related to the steady state deterministic chemical flux. For the monostable model of the kinetic cycle, the analytical expression of the probabilistic flux is directly related to the deterministic flux, and the later is directly generated by the chemical potential difference from the adenosine triphosphate (ATP) hydrolysis. For the limit cycle of the reversible Schnakenberg model, we also show that the probabilistic flux is correlated to the chemical driving force, as well as the deterministic effective flux. Furthermore, we study the phase coherence of the stochastic oscillation against the energy pump, and argue that larger non-equilibrium pump results faster flux and higher coherence. This leads to higher robustness of the biological oscillations. We also uncovered how fluctuations influence the coherence of the oscillations in two steps: (1) The mild fluctuations influence the coherence of the system mainly through the probability flux while maintaining the regular landscape topography. (2) The larger fluctuations lead to flat landscape and the complete loss of the stability of the whole system.     

On the transport and trajectories of the chernobyl debris across Canada and the arctic

A scenario is presented for the transport of the Chernobyl radioactive debris across Canada and the Arctic. It is based on the analysis of the¹⁰³Ru/¹³⁷Cs ratios in terms of the Chernobyl release pattern. The ratios which ranged from 0.2 to more than 4.0 were associated with four different phases of the Chernobyl emissions which lasted 10 days, from April 26 to May 6, 1986. Debris from the initial phase /ratios of 0.2 to 0.5/ and the last phase /ratios above 2.5/ would have entered Canada on a very broad front extending from northern Quebec to the North West Territories by way of Greenland and the Arctic; debris from the second phase /ratios of 0.5 to 2.0/ and the third phase /ratios of 2.0 to 2.5/ would have entered Canada from the west after travelling by way of northern Siberia and the Bering Sea.Paper presented at the IVth International Symposium of Radioecology of Cadarache, France, March 1988.     

Analysis and assessment of the occurrence, the fate and the behavior of nanomaterials in the environment

Nanomaterials have one dimension <100 nm and possess physico-chemical properties dictated by their unusually small size, large surface area, shape and chemical composition. New properties of nanomaterials have boosted their production and industrial applications in many fields (e.g., microelectronics, catalysis, fuel cells, materials science, textiles, biotechnology and medicine). In biomedical fields, nanomaterials are of the appropriate dimensions to interact with biological matter. However, they may also have negative effects on biological systems. Nanotechnology is a major, innovative, scientific and economic growth area, but the increasing production and use of nanomaterials have led to calls for more information regarding the potential impacts that their release may have on human health and the environment.This review addresses analytical approaches for characterization and quantification of nanomaterials in the environment and recent studies on their occurrence, fate and behavior.     

麻黄-甘草药对配伍前后主要药效成分及抗炎活性的变化

利用高效液相色谱串联质谱联用法(HPLC-MS/MS)和气相色谱质谱联用法(GC-MS)分析了麻黄与甘草药对配伍前后水煎液中主要药效成分的变化,并通过小鼠的耳廓肿胀试验考察了甘草、麻黄单煎液及药对共煎液的抗炎活性变化.分别通过HPLC法和GC-MS法对甘草与麻黄中主要化学成分,甘草酸、甘草苷、麻黄碱和甲基麻黄碱进行了定量分析,通过单煎液和药对共煎液的对比,发现麻黄与甘草配伍共煎液中麻黄碱(含伪麻黄碱)的含量增加了14.52%;甲基麻黄碱(含甲基伪麻黄碱)的含量增加了64.0%;甘草酸含量增加了13.50%;而甘草苷含量降低了19.38%.药效实验证明,甘草与麻黄配伍后抗炎作用较甘草麻黄单煎液明显增强.从而在主要成分的变化程度上揭示了甘草与麻黄配伍过程中的增效机理.     

Decorating step-by-step and independently the surface and the core of dendrons

Dendrons possessing one activated vinyl group at the core and several chlorine atoms at the end of the branches are used as starting materials to study the possibility to react independently the surface functions and the core function. In particular, the most powerful sequence of reactions for decorating them by organometallic complexes as end groups and amine or alcohol at the core has been determined. In the first step, phenol phosphines are grafted as end groups of the dendrons, and they can be used for the complexation of metals. However, these phosphines must be kept free when amines are used to react with the vinyl core in the next step. Depending on the type of phosphine end groups and on the type of function of the core (amine or alcohol), the complexation of ruthenium ([RuCl₂(p-cymene)]₂) and rhodium ([RhCl(COD)]₂) derivatives by the phosphine end groups can occur without side reaction at the core.     

Age of the earth and the moon

We have examined the isotopic compositions of lead reported for 55 terrestrial and 65 lunar samples. The lead ages indicate that the 4.55 billion years generally accepted as the age of the solar system refers instead to the time of the breakup of the meteorite parent body.