Polarography of Uranium Chelate with 2,3-Cresotic Acid

The polarography of uranyl ion in 2,3-cresotic acid solution has been studied at 25°C under varying conditions of ligand concentration and pH. The ligands species were proved to be a 2,3-cresotate anion. The half-wave potential vs. pH value interpreted on the basis of pK value for the acid ionization, and resulted in agreement with the deduction. The mole ratio of metal to ligand was found to be 1:1 and 1:2 by conductometric titration. At pH < pK₁, the complex species of UO₂(H₂A)²⁺ and UO₂(HA)⁺ was identified. At pK₁ < pH < pK₂, the co-existence of UO₂(HA)⁺, UO₂(OH)(HA)₂^? and UO₂(A)₂^2– was confirmed. At pH > pK₂, the complex species of UO₂(OH) (A)₂^3– was formed.     

Linear Relations of Activation Energy in Non-isothermal Kinetics

Temperature-modulated DSC (TMDSC) measurements at reasonably high frequencies allow for the determination of base-line heat capacity. In this particular case vitrification and devitrification of the rigid amorphous fraction (RAF) can be directly observed. 0.01 Hz seems to be a reasonably high frequency for bisphenol-A polycarbonate (PC). The RAF of PC is established during isothermal crystallization. Devitrification of the RAF seems to be related to the lowest endotherm. For PC the melting of small crystals between the lamellae is expected to yield the lowest endotherm. This revised version was published online in July 2006 with corrections to the Cover Date.     

动力学、热力学和活化能在花生壳吸附铅离子实验中的应用

以花生壳为吸附剂、Pb2+为模拟污染物研究了物理化学中固体表面的吸附过程,考察了Pb2+的初始浓度、吸附温度的影响,研究了固体表面吸附反应动力学、热力学和活化能。结果表明:在不同Pb2+初始浓度下,Pb2+在花生壳表面的吸附动力学符合准二级动力学模型,表明该吸附过程是化学吸附为控制步骤的吸附过程。热力学结果表明Pb2+在花生壳表面的吸附是一个自发的放热过程,因为Pb2+由三维运动转变为二维运动导致系统熵减小。活化能Ea=31.35 kJ·mol-1再次证明Pb2+在花生壳表面的吸附是化学吸附过程,这些结果较好地验证了物理化学教学中固体表面的吸附行为。通过该拓展实验加深了学生对固体表面吸附过程的理解,同时,培养了学生的科技创新能力。     

Second-order Impedance in Electrode Kinetics

The kinetics of electrode reactions with a rather severe influence of the EDL structure is studied by nonlinear second-order impedance spectroscopy. Polarization impedance spectra and potential dependences of a nonlinear impedance are obtained for the reaction of electroreduction of the ferricyanide anion on the cadmium and bismuth electrodes in surface-inactive supporting NaF and Na₂SO₄ electrolytes. The results of measurements for the reaction Eu³⁺ + e Eu²⁺ on the bismuth and mercury electrodes are presented. It is shown that such important parameters of EDL as the potential of zero charge and the second derivative of potential with respect to the charge of the electrode surface can be determined directly from experimental curves even under conditions of occurrence of a faradaic process.     

2,2′-二氨基苯氧基二硫化物的电极过程动力学研究

利用循环伏安法、线性伏安法及旋转圆盘电极技术,研究了2,2′-二氨基苯氧基二硫化物(DAPOD)在含有0.1 mol·L-1LiClO4电解质的乙腈/四氢呋喃有机溶液中,铂、金、玻碳及石墨电极上的电化学行为.伏安结果表明DAPOD中的二硫键与硫巯基之间的氧化还原反应属动力学不可逆过程,这种在室温下表现出的电化学反应不可逆性是有机二硫化物普遍存在的不足,必须通过分子内或分子间的电催化来改善其可逆性能.旋转圆盘电极测试结果显示,DAPOD的阴极还原反应级数为0.5,阳极氧化反应级数为1.由此推知DAPOD电还原属两电子转移反应,分两步完成:第一步为平衡的化学反应步骤;第二步为电子转移步骤,属决速步.同时还测定了DAPOD的阴极与阳极传递系数、交换电流、平衡电势及标准速率常数等相关的动力学常数.通过比较铂、金、玻碳及石墨四种不同材料电极对DAPOD的电极过程的影响,发现石墨对DAPOD的还原过程具有电催化作用.     

2,2’-二氨基苯氧基二硫化物的电极过程动力学研究

利用循环伏安法、线性伏安法及旋转圆盘电极技术，研究了2,2’-二氨基苯氧基二硫化物(DAPOD)在含有0.1 mol•L－1 LiClO4电解质的乙腈/四氢呋喃有机溶液中，铂、金、玻碳及石墨电极上的电化学行为.伏安结果表明DAPOD中的二硫键与硫巯基之间的氧化还原反应属动力学不可逆过程，这种在室温下表现出的电化学反应不可逆性是有机二硫化物普遍存在的不足，必须通过分子内或分子间的电催化来改善其可逆性能.旋转圆盘电极测试结果显示， DAPOD的阴极还原反应级数为0.5，阳极氧化反应级数为1.由此推知DAPOD电还原属两电子转移反应，分两步完成：第一步为平衡的化学反应步骤；第二步为电子转移步骤，属决速步.同时还测定了DAPOD的阴极与阳极传递系数、交换电流、平衡电势及标准速率常数等相关的动力学常数.通过比较铂、金、玻碳及石墨四种不同材料电极对DAPOD的电极过程的影响,发现石墨对DAPOD的还原过程具有电催化作用.     

壳聚糖亚铁螯合物的合成及吸附动力学

亚铁离子;配合物;螯合物;壳聚糖亚铁螯合物的合成及吸附动力学     

SiO的电化学性能及其电极过程动力学研究

本文采用恒流充放电考察SiO的电化学性能，并在0.5 MHz至0.001 Hz的频率范围内，通过交流阻抗技术研究SiO电极在首次嵌锂反应中的电极过程。对不同电压区间下测得的交流阻抗图谱，提出不同的等效电路模型并对结果进行了拟合。通过拟合结果，探讨了SiO电极过程动力学以及嵌锂过程中电极界面的变化特性。     

Kinetics of Metal Extraction by Chelate Formation Part II. Extraction of Cu(II) by Hydroxyoximes

The rate of extraction of copper from aqueous solutions by chelate-forming extractants was examined. Two extractants based on hydroxyoximes (salicylaldoxime dissolved in chloroform, and the commercial extraction agent LIX-64N dissolved in kerosene) were used. Experiments were carried out in a mass transfer cell with vibrational mixing of the phases. The conclusions arrived at are as follows: the model of mass transfer accompanied by a fast reversible reaction describes well the integral data obtained. The reaction rate is influenced significantly by the rate of diffusion of the extractat in the organic phase, as well as by the rate of formation of the extractable complex, and possibly also by the rate of copper diffusion towards the interface in the aqueous phase.     

Temperature Oscillations Characterized by An Overall Activation Energy

Temperature oscillations obtained during the heterogeneous catalytic oxidation of ethanol on Pd-Al₂ O₃ in a dynamic calorimeter were characterized by an overall activation energy. This parameter was determined by a non-isothermal kinetic method using the minimum and maximum values of the oscillations temperature. Using the bifurcation diagram with the oxygen as a bifurcation parameter an E value between 27.6 and 28.2 kJ mol^-1 was obtained. With ethanol as bifurcation parameter the E values lies between 28.1 and 31.1 kJ mol^-1 for 3.5 to 4.0 vol% ethanol and between 25.8 and 27.6 kJ mol^-1 for 4.0 to 4.7 vol% ethanol. These results have been discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of Barium by Classical and Alternating-Current Polarography

The behavior of barium(II) in 0.1–5.0 M CaCl₂ solutions was studied by classical and alternating-current polarography. The kinetic parameters of barium(II) reduction and the diffusion coefficients were determined. A procedure for the determination of barium in calcium salts was proposed.     

哌仑西平的单扫描示波极谱法测定

本报道一种测定哌仑西平的单扫描示波极谱法，在０．１ｍｏｌ／ＬＮＨ４Ｃｌ－ＮＨ３．Ｈ２Ｏ（ｐＨ８．０±０．１）缓冲液中，哌仑西平有一极谱还原波，其峰电位为－１．５１Ｖ（ｖｓ．ＳＣＥ），其一阶导数峰高与哌仑西闰浓度在６．６×１０＾－７－４．６×１０＾－６ｍｏｌ／Ｌ（ｒ＝０．９９８１）和６．６×１０＾－６－１．６×１０＾－５ｍｏｌ／Ｌ（ｒ＝０．９９９１）范围内有线性关系，检测限为３．４×１０－７ｍｏｌ     

葡萄糖氧化酶修饰聚苯胺电极的动力学

虽然固定酶有吸附、交联、共价结合和捕集等多种方法,但寻找其新的固定方法仍是感兴趣的研究课题。利用导电高聚物的导电性和掺杂作用,将酶直接固定在导电高聚物上,这种方法简单,固定后的酶仍保持原有的活性。用聚苯胺固定葡萄糖氧化酶已有报道。但电极的活性有效期较短。考虑到固定酶的性质不仅取决于酶本身的性质,而且还受载体性质和固定方法的影响,我们曾用还原后的聚苯胺在酶溶液中氧化而固定酶,本文在文献的基础上,研究了葡萄糖氧化酶修饰聚苯胺电极的动力学特性、pH效应及其使用稳定性。     

Solar Energy Conversion Using a Semiconductor Electrode Photosensitized by Tetraphenylporphyrin

The synthesis of meso-tetraphenylporphyrin (TPP) and its application in a solar- energy conversion device are described as an undergraduate laboratory experiment. In the first part of the exercise, a convenient procedure for the synthesis of TPP is presented. In the second section of the experiment, the construction of a high-efficiency photoelectrode that utilizes the light harvesting capacity of the porphyrin is presented. The spectral sensitization of a wide-band-gap semiconductor is achieved using TPP as an efficient photoreceptor, This mimics the role of the tetrapyrrolic macrocycle in natural photosynthesis.     

胆红素的间接极谱测定

在Hg~(2+)(或Hg~+)-EDTA-磷酸钠缓冲溶液中,胆红素可被迅速氧化成浅绿色产物。该产物可在-0.83V(vs.SCE)左右产生一灵敏的极谱波,其导数波高与胆红素浓度在4×10~(-7)～6×10~(-6)mol/L范围内呈线性关系,因此该波可用于胆红素的间接测试。本文对胆红素的氧化机制和极谱波的性质进行了研究。发现胆红素被氧化成了胆绿素,而所产生的极谱波为一催化波。     

胡椒碱的极谱分析研究

在ｐＨ２．２的Ｂｒｉｔｔｏｎ－Ｒｏｂｉｎｓｏｎ缓冲溶液中，胡椒碱在－１．１０Ｖ（ｕｓ．ＳＣＥ）左右产生一灵敏的极谱波，导数峰电流与胡椒碱浓度在０．０５－８μｇ／ｍｌ范围内呈良好的线性关系。本法操作简便，快速，灵敏，选择性较好。用于天然胡椒果实中胡椒碱的测定，得到了满意结果。本文对极谱波性质及电极反应机理进行了研究。     

Determination of Nitrite by Single-Sweep Polarography

Abstract

A new method for determining nitrite is proposed. the mechanism for the polarographic waves and the condition for determining nitrite are discussed in this paper. In cathodic sweeps, the peak height is directly proportional to the concentration of nitrite over the range 5×10^?9?6×10^?7 g/ml, the detection limit is 4×10^?9g/ml. the experiments showed that this polarographic wave is an adsorption wave, and useful in determination of nitrite in water sample.     

次亚磷酸根在镍电极上的电氧化机理与动力学

用电化学质谱(EMS)和动力学模型分析等方法研究了次亚磷酸根在镍电极上的电化学氧化机理和动力学.研究表明，次亚磷酸根的电化学氧化是通过从P－H键脱离一个原子H，形成磷中心自由基(PHO2－•)，而磷中心自由基(PHO2－•)进一步进行电化学反应形成最终产物亚磷酸。利用该模型，推导出相关动力学方程并通过与实验数据拟合获得动力学参数.结果表明，该模型能很好地模拟次亚磷酸根在镍电极上的电化学氧化过程.     

峰宽法快速测定程序升温脱附活化能

TPD技术^[1]已成为研究固体表面性质的重要手段,本文在总结前人工作的基础上考察了TPD谱峰峰宽和相应参数与脱附活化能(E_d)之间的变化规律,证明用任意峰宽法或半峰宽法测定E_d值有很好的实用性,该法直接运用TPD谱图参数,无需另外作图,故十分快速、简便,与其它方法比较,结果吻合。