间二苯酚-KBrO3-H2SO4体系化学振荡的研究

用电位法研究了间苯二酚-KBrO_3-H_2SO_4(体系A)及间苯二酚-KBrO_3-H_2SO_4-MnSO_4(体系B)的化学振荡现象. 得出了两振荡体系的诱导期及振荡周期与反应物起始浓度及温度关系的经验方程.间苯二酚在诱导期结束时全被氧化, 它不是参与振荡的物质. 体系B在低Mn~(2+)浓度下可呈现双振荡现象, 即第一类振荡结束后, 经一段非振荡时间再产生第二类振荡. 两类振荡的特征不同. 第一类振荡与体系A的振荡行为基本相似. 第二类振荡的各个周期随c_M 减小而缩短,最后趋于相同; 随c_K、c_H增大而减小, 最后各自趋于一致. 但周期与c_R基本无关. 第二类振荡出现周期双单调变化现象, 它补充与支持了文献[1]中的提法. 当Mn~(2+)浓度增高到一定程度后, 双振荡现象消失, 仅产生一种振荡. 体系B是产生双振荡现象的典型事例之一.     

中药板蓝根的化学振荡指纹图谱研究

采用振荡技术,研究了中草药及中成药板蓝根-丙酮-溴酸钾-硫酸锰-硫酸的振荡反应新体系的振荡指纹图谱.测定了不同浓度,不同温度下板蓝根的振荡反应图谱,得到了不同温度、浓度下的反应诱导期、振荡周期及振荡寿命,得出诱导期表观活化能Ein=135.054kJ/mol,振荡周期平均活化能Ep=71.802kJ/mol;初步研究此...     

氨基酸化学振荡反应活性中心的研究

我们已经报导了一系列氨基酸参与的化学振荡反应，获得了各振荡体系中反应物的浓度范围和典型振荡波形．初步拟定了反应机理，得到了振荡反应诱导期和周期的表观活化能以及各反应物初始浓度与诱导期或周期之间的定量关系［l，2］．然而，综观各振荡体系，不同结构的氨基酸一Bfoi－Mn‘＋－H。SO。一丙团（Act）体系中的BrOS、Mn‘＋、Act起振浓度变化很小，而各种氨基酸的最低起振浓度却存在着相当大的差异，且与酸度密切相关．为此，本文固定你对5］。二0．04mol·din－’；卜n‘＋o二0．016mol·din－‘；［Actfo二0．054mol·din－…     

探究碘钟振荡实验的最佳条件及反应机理

利用SPSS25.0统计软件对碘钟振荡实验进行正交实验设计，通过统计学分析得出最佳实验条件为：温度30℃，硫酸浓度2 mol/L，加入反应物后搅拌8 s。利用氧化还原传感器（ORP）对碘钟振荡体系的电极电势变化曲线进行分析，结合文献及曲线从热力学和动力学视角阐述其反应机理。基于宏观、微观、符号和曲线进行四重表征分析，以期帮助学生深刻理解趣味实验现象背后的微观反应本质是碘元素不同价态之间的相互转化。     

四物汤及其单味药振荡反应的微量量热法研究

采用微量量热法对四物汤及其单味药振荡体系进行了研究, 测定了四物汤及其单味药在不同浓度、不同温度下的振荡体系的热功率-时间曲线, 得到了它们的诱导期、振荡周期, 根据非平衡态理论计算了它们的反应级数和表观活化能, 并建立了诱导期、振荡周期与浓度和表观活化能之间的非线性关系式.     

酪氨酸-溴酸钾-硫酸-丙酮在三邻菲啰啉合铁(Ⅱ)催化下的B-Z振荡反应

研究了酪氨酸-溴酸钾-硫酸-丙酮在三邻菲啰啉合铁(Ⅱ)催化下的化学振荡反应,对振荡的影响因素进行了研究和讨论.运用正交实验法确立了振荡反应进行的浓度范围,得到一个40多次振荡寿命为60 min的振荡波.获得振荡的诱导期和周期与反应物浓度之间的变化趋势曲线,以及振荡反应在诱导期和振荡期的表观活化能分别为Ein=49.0 kJ/mol和E=57.0 kJ/mol.根据反应过程中的现象和实验数据,建立了振荡反应的模型和反应机理,确定[Br-]是振荡反应自发进行的关键因素.     

亚氯酸盐氧化硫脲非缓冲体系的复杂动力学行为

研究了ClO2--SC(NH2)2的非缓冲体系中的动力学行为,发现在开放体系中,体系的铂电极电位和pH呈现反相位连续的大幅度振荡,随着流速的降低,体系行为更加丰富,在高流速的混合模式之后出现了低流速的混合模式;在外部条件变化时,观察到了准周期振荡和倍周期振荡现象;考察了温度、流速、酸度以及反应物的初始浓度比等主要的影响因素,发现分叉参数的变化与体系的行为紧密相关。     

伯胺萃取醋酸振荡体系的微量热法研究

用注入/滴定微量热计测定了伯胺N1923氯仿液萃取醋酸的萃取振荡反应体系的热功率—时间曲线,得到了萃取振荡反应体系的诱导期,第一振荡周期和第二振荡周期.计算了表观活化参数,建立了诱导期与振荡周期和起始醋酸浓度、温度间的关系式.     

氟离子-乳酸-丙酮-Mn2+-BrO－3-H2SO4振荡反应及其在分析中的应用

氟离子对乳酸-丙酮-Mn2+-BrO-3-H2SO4化学振荡反应的周期和振幅有显著的影响,F-的浓度在8.00×10-5～1.00×10-3 mol·L-1范围内与振荡反应周期的改变值△tp和振幅的改变值△H均有良好的线性关系,是一线性范围宽、灵敏度高的动力学分析测试体系.获得振荡反应诱导期、周期的表观活化参数Ein、Ep分别为55.71 kJ·mol-1、67.41 kJ·mol-1,探索了该振荡体系可能的反应机理.     

以衣康酸-BrO-3-Mn2+为体系的化学振荡研究

本文研究了BrO_3~--Br~--H~+-Mn~(2+)-衣康酸体系的振荡行为, 利用电位法及分光光度计对体系做了一系列测定, 根据FKN机理, 提出了本体系可能的反应进程, 同时测定了各种反应条件对振荡的诱导期及周期影响, 并根据机理分析把诱导期分成两个部分, 得到1/τ_(i1), 1/τ_(i2), 1/τ_p对各种反应物起始浓度的关系式。还发观葡萄糖能促进振荡进行。     

维生素C稀溶液光化分解导致的振荡行为

光化学振荡是近十多年才发现和研究的一种新的时空振荡行为目前的文献屈指可数,机制的解释各说不一。维生素C的化学振荡1982年以来仅有个别的报导。我们发现在一定浓度,温度条件下,局部光照维生素C稀溶液,若不搅拌,经过一段前置期可以获得规整性和重现性相当好的衰减式周期性振荡波。本文还研究了它的特征,形成条件及其可能的偶合机制,对维生素C稀溶液光化学反应动力学和机理也进行了探讨。     

New Oscillatory Process in Aqueous Solutions of Compounds Containing Carbonyl and Amino Groups1

Frequency-correlated oscillations of chemiluminescence and the redox potential are observed during the amino-carbonyl reaction, which occurs in aqueous solutions of methylglyoxal and various amino-containing compounds (ethanolamine, glycine, and -alanine) at room temperature. The duration and amplitude of oscillations depend on the composition and concentration of the starting reactants, pH, stirring, and surface area through which oxygen diffuses into the system.     

Correlative studies on the fabrication of poly(styrene-methyl-methacrylate-acrylic acid) colloidal crystal films

This research describes a one-step procedure for monodispersed poly(styrene-methyl-methacrylate-acrylic acid colloidal spheres [P(St-MMA-AA)] via soap-seeded emulsion polymerization. The effects ofreaction conditions such as temperature, stirring speed, initiation concentration, e.t.c. were examined. The results obtained showed that the spheres average particle diameter decreased with increase in initiator concentration, the reaction temperature and stirring speed and increased with an increase in monomer concentrations. The particles show stable mechanical properties within the transition and heating temperatures of 111.9?°C and 388?°C respectively. Zeta-potential values ranging from ?31.8?mV to ?36.5?mV which is indicative of stable dispersion of colloidal particles were obtained for all the prepared latexes. The assembled colloidal latex had periodic structures with mainly hexagonal three-dimensional structures with multi-facet arrangements. The latex also shows spherical shape of monodispersed core-shell particles.     

搅拌对Belousov-Zhabotinskii振荡反应的影响及反应机理研究

研究了非流动条件下搅拌对B-Z振荡反应的影响。实验发现即使在氮气保护下, 搅拌仍对振荡行为(振幅和周期等)有明显影响。为解释搅拌的影响作用, 对B-Z反应的Oregonator模型作了修正和补充并依据非平衡态热力学的一般原理将搅拌影响唯象地归结为反应速率常数的相对变化。修正后的模型不仅较好地克服了原模型存在的一些问题, 而且在引入搅拌作用以后得到了与实验现象定性一致的数值模拟结果。     

NiL(ClO4)2催化NaBrO3-MA-H3PO4体系振荡反应的研究

报道了一种反式Curtis环的镍(Ⅱ) 的配合物NiL(ClO4)2(L为2,4,4,9,11,11-六甲基-1,5,8,12-四氮杂环十四-1,5,8,12-四烯)催化NaBrO3-CH2（COOH）2（MA）-H3PO4体系的化学振荡反应。测得该体系的振荡范围,研究、分析了各物种浓度、自由基抑制剂和还原剂、Ag+、Hg2+以及温度对振荡反应的影响。结果表明Br-起重要动力学控制作用,在反应过程中有自由基、Br2产生并参与了反应。同时发现搅拌速度对反应有很大影响。该反应的振荡轨迹与经典BZ反应及其它四氮杂大环配合物催化的体系有所不同。     

Stirring-controlled bifurcations in the 1,4-cyclohexanedione-bromate reaction

We report the experimental observation that stirring in a closed 1,4-cyclohexanedione-bromate reaction can induce transitions not only between oscillatory and nonoscillatory states but also between simple and period-doubled oscillations. Notably, the transition from simple to complex oscillations occurs as a result of increasing stirring rate. When illumination was employed to characterize the importance of microfluctuations of concentrations, the threshold stirring rate for inducing a bifurcation was found to increase proportionally to the intensity of the applied light. Numerical simulations with an existing model illustrate that the experimental phenomena could be qualitatively reproduced by considering effects of mixing on diffusion-limited radical reactions, namely, the disproportion reaction of hydroquinone radicals.     

Inhibitory Effects by Ascorbic Acid on the Oscillations of the Briggs?Rauscher Reaction

The Briggs? Rauscher oscillating reaction (in batch mode) has been shown to be sensitive to various antioxidants, some of which cause cessation of oscillations for a period of time, before a restart occurs. The length of time before oscillations restart is related to the type of antioxidant and its concentration. Procedures have been devised to apply this method as a tool for measuring antioxidant activities of pure compounds and of extracts of natural sources. The antioxidant activity in the Briggs? Rauscher system has been generally related to the reaction of an antioxidants with hydroperoxy radicals (HOO^.) present in the oscillating system. Thereby, at low concentration (<2×10^?4 M ), ascorbic acid is known to have a little effect on the reaction. However, there is a concentration range, where a nearly linear relation is observed between ascorbic acid concentration and inhibition time. We were able to model this type of inhibition by the reducing power of ascorbic acid without invoking a reaction with HOO^..     

Elektrochemische oszillationen bei der inhibierten kupferabscheidung an der quecksilberelektrode

In the polarographic deposition of Cu²⁺ and Bi³⁺ in the presence of tribenzylamine in acid solution there is a potential region with a negative characteristic. With suitable external circuitry, electrochemical oscillations can be produced in this potential region. The influence of applied potential, working resistance, stirring of the electrolyte, temperature as well as reactant and inhibitor concentration, were tested. The oscillations occur with periodic adsorption and desorption of the inhibitor coupled with periodic concentration changes of the reactant in the neighbourhood of the electrode during the polarographic reduction.     

Collective behavior of a population of chemically coupled oscillators

Experiments are performed in which a large number (approximately 10(4)) of relaxation oscillators are globally coupled through the concentration of chemicals in the surrounding solution. Each oscillator consists of a microscopic catalyst-loaded particle that displays oscillations in the concentrations of chemical species when suspended in catalyst-free Belousov-Zhabotinsky (BZ) reaction solution. In the absence of stirring, the uncoupled particles display a range of oscillatory frequencies. In the well-stirred system, oscillations appear in the surrounding solution for greater than a critical number density of particles (n(crit)). There is a growth in the amplitude of oscillations with increasing n, accompanied by a slight increase or no change in frequency. A model is proposed to account for the behavior, in which the transfer of activator and inhibitor to and from the bulk medium is considered for each particle. We demonstrate that the appearance and subsequent growth in the amplitude of oscillations may be associated with partial synchronization of the oscillators.     

The leaching kinetics of brannerite ore in sulfate solutions with iron(III)

A kinetic study of the leaching of powdered brannerite ore by sulfuric acid has been investigated. The effects of stirring speed ranging from 100 to 1,000?min^?1, particle size ranging from 20 to 120???m, concentration of Fe(III) ranging from 0.0025 to 0.20?M, acid concentration ranging from 0.1 to 2.0?M and temperature ranging from 15 to 90?°C on uranium dissolution are reported. The dissolution rate was founded to be significantly influenced by the temperature and concentration of the acid in solution. The experimental data for the dissolution rates of uranium have been analyzed with the shrinking-core model for reaction control. The apparent activation energy for the dissolution of uranium has been evaluated using the Arrhenius expression.