Kinetics of the surface tension of micellar solutions: Comparison of different experimental techniques

The kinetics of the surface tension of micellar solutions of nonionic surfactant Triton X-100 is measured experimentally by means of three different techniques: oscillating jet, maximum bubble pressure and inclined plate. They allow to study the micellization kinetics at various time scales (from a few milliseconds to a few seconds) in fairly large concentration region up to 50 times CMC. The experimental data are satisfactorily explained by a theoretical model accounting for the kinetics of micellization, diffusion of surfactant species and expansion of the bubble interface. By this model are computed the characteristic times of diffusion and micellization, which are of comparable magnitude (about 5 to 200 ms), and the Gibbs' elasticity. The micellization time constant corresponds to the slow relaxation process known to coincide with the disintegration of micelles. Comparing our data with other data from literature one can conclude that more realistic information for the micellization kinetics is obtained by the maximum bubble pressure and the oscillating jet method. The inclined plate seems too slow to measure the relaxation processes in micellar solutions of this surfactant.     

吡洛昔康的极谱测定

在0.06mol/LHAc NaAc(pH4.5±0.1)缓冲溶液中,吡洛昔康于-1.23V(vs.SCE)处产生一灵敏的极谱催化氢波,其二阶导数峰电流与吡洛昔康浓度在2.0×10-8～5.6×10-6mol/L范围内呈线性关系(r=0.9990,n=8),检出限为1.0×10-8mol/L。该方法可用于药剂中吡洛昔康的测定。     

钪 钇茜素红S异多核络合物极谱吸附波的研究

报道了钪钇茜素红Ｓ异多核络合物的形成及该异多核络合物极谱吸附波测定钪的最佳实验条件。用此方法测定了纯氧化钇中的微量钪, 并探讨了该极谱波的性质和电极反应机制。在单扫描示波极谱上用单纯形法和改良的平衡移动法测得该异多核络合物组成的摩尔比为： ｘＳｃ３＋ ∶ｘＹ３＋ ∶ｘＡＲＳ＝１∶２∶５ 。     

锡(Ⅳ)-邻苯三酚红-钒(Ⅳ)-十二烷基磺酸钠体系极谱吸附催化波研究

在0.1mol/L氯乙酸盐缓冲溶液(pH2.4)中,锡(Ⅳ)-邻苯三酚红(PR)-钒(Ⅳ)-十二烷基磷酸钠(SDS)体系产生一灵敏的吸附平行催化波,峰电位为-0.53V(vs.SCE),一次导数峰高与锡浓度在6.7×10~(-10)～10×10~(-6)mol/L范围内呈良好的线性关系,检测限为4×10~(-10)mol/L.方法已成功地应用于罐装食品中微量锡的测定,结果满意.     

络合吸附波极谱法测定稀土钢中微量稀土

研究了在ｐＨ９．２－ｐＨ９．５的ＮＨ３０Ｎａ２Ｂ４Ｏ７介质中,稀土与百里香酚酞的络合物极谱波,波高与镧量在４．０×１０＾－７－３．６×１０＾－６ｍｏｌ／Ｌ范围内成线性关系。方法已用于稀土钢中微量稀土的测定。     

冲击波处理的结晶MgO的化学分析正电子谱研究

冲击波处理的结晶ＭｇＯ的化学分析正电子谱研究＊张菊郑小明（杭州大学催化研究所，杭州３１００２８）常志向（抚顺石油化工研究院，抚顺１１３００１）关键词冲击波，化学分析正电子谱，结晶氧化镁，丁烯，脱氢冲击波是在介质中以超音速传播的压力脉冲．气体中的冲击波...     

电磁波对化学反应非致热作用的实验研究

微波加快化学反应速度除微波对反应物的加热以外还有非致热的作用，本文用实验证实了电磁波对离子和极性分子的洛仑兹力的作用导致了指前因子和活化能的变化，并提出用电磁作用因子描术电磁波对化学反应作用的大小。     

铜（Ⅱ）锌（Ⅱ）－氟哌酸体系电化学行为及示波极谱法研究

铜（Ⅱ）和锌（Ⅱ）分别在０．１ｍｏｌ／ＬＫＨ＿２ＰＯ＿４－Ｎａ＿２ＨＰＯ＿４缓冲溶液（ｐＨ６．５）和０．２５ｍｏｌ／ＬＮＨ＿４Ｃｌ溶液中，与氟哌酸形成良好的络合吸附波，峰电位分别为－０．２６Ｖ和－１．２８Ｖ（ｖｓ；ＳＣＥ）；络合比分别为１：３和１：２；峰电流与铜（Ⅱ）和锌（Ⅱ）的浓度均在４．０×１０￣（－７）～５．０×１０￣（－６）ｍｏｌ／Ｌ范围内呈线性关系，检测限分别为７．０×１０￣（－８）和５．０×１０￣（－８）ｍｏｌ／Ｌ。用线性扫描和循环伏安法等手段研究体系的行为，表明均具吸附性，而铜（Ⅱ）－氟哌酸体系属络合物中铜（Ⅱ）的两电子还原的可逆过程。     

Measurement of attachment force of microbial cells

A parallel-plate flow chamber consisting of two transparent electro-conductive glass plates was constructed. The two glass plates were set parallel to each other and connected to a potentiostat apparatus to regulate the strength of the electric field between the plates. A microbial cell suspension was flowed through the chamber. This system enabled the application of an electrostatic force to suspend charged particles, e.g. microbial cells, existing between the two plates. The time course of the cell attachment of Pseudomonas syringae pv. atropurpurea NIAES 1309 suspended in 10 mM phosphate buffer solution (pH 7.0) to the glass plate was investigated at various electric field strengths ranging from −4.2 to +4.1 V cm⁻¹. The attachment rate and the maximum number of attached cells increased linearly with the increase in the strength of the positive electric field. In contrast, the rate and the number of cells decreased linearly with the decrease in the strength of the negative electric field. These linear relations gave a specific value for the strength of the electric field (−5.9 ± 0.7 V cm⁻¹) where the electrostatic repulsion and the microbial attachment force were thought to be equal, resulting in no cell attachment. From this value, the electrostatic repulsion, i.e. the microbial attachment force, was calculated to be 5.0 × 10⁻¹¹ N cell⁻¹ for cells of average size.     

Quantitative surface analysis by Auger and x-ray photoelectron spectroscopy

Recent developments in quantitative surface analysis by Auger (AES) and x-ray photoelectron (XPS) spectroscopies are reviewed and problems relating to a more accurate quantitative interpretation of AES/XPS experimental data are discussed. Special attention is paid to consideration of elementary physical processes involved and influence of multiple scattering effects on signal line intensities. In particular, the major features of core-shell ionization by electron impact, Auger transitions and photoionization are considered qualitatively and rigorous approaches used to calculate the respective transition probabilities are analysed. It is shown that, in amorphous and polycrystalline targets, incoherent scattering of primary and signal Auger and photoelectrons can be described by solving analytically a kinetic equation with appropriate boundary conditions. The analytical results for the angular and energy distribution, the mean escape depth, and the escape probability as a function of depth of origin of signal electrons as well as that for the backscattering factor in AES are in good agreement with the corresponding Mote Carlo simulation data. Methods for inelastic background subtraction, surface composition determination and depth-profile reconstructions by angle-resolved AES/XPS are discussed. Examples of novel techniques based on x-ray induced photoemission are considered.