A comparison of ion-solvent interactions evaluated from both emf and conductance data for HCl in aqueous solvent mixtures

Available emf data for HCl in water-dioxane, water-tetrahydrofuran, and water-dimethoxyethane at 25°C have been analyzed using models based on similar levels of approximation as was used previously for conductance data. The emf data were evaluated in terms of standard cell potentials, apparent distances of closest approach, association constants and a Gibbs energy term attributed to non-coulombic ion-solvent interaction. Although emf and conductance data give essentially the same results it is clear that the conductance method, with its much greater precision, is superior for this type of analysis.     

混合溶剂中氨基酸热力学性质的研究 IV: 278.15-318.15K下甘氨酸-乙醇-水体系

在混合溶剂中恒定乙醇的质量百分数χ=10%, 应用电动势法测定了无液接电池(A)和电池(B)的电动势。根据电池(A)和电池(B)的电动势, 用传统的Debye-Huckel外推法和我们在前文提出的多项式逼近程序, 确定了甘氨酸有278.15-318.15k范围内5个温度下的第一、第二热力学解离常数, 两种方法所得的结果在实验误差范围内一致。并相应计算了该体系的热力学量。     

尿素-水混合溶剂中硫酸热力学性质的研究

本文应用电动势法测定下面无液接电池在278．15-318．15K温度范围内的电动势。     

Design of a microfabricated magnetic cell separator.

A new magnetic separation idea utilizing several ideas from microfabrication and nanomagnetics is presented. The basic idea comes from our earlier work using asymmetry in obstacles and Brownian motion to effect separation of objetcs [10] by moving them in streams whose angle to the hydrodynamic average velocity is a function of the diffusion coefficient of the object. The device we propose here is not technically a Brownian ratchet device but uses the idea of force which acts at angle to the hydrodynamic flow. In our case, the force is generated by a magnetic field gradient which comes from an array of magnetized wires which lie at an angle 0 to a hydrodynamic field flow. The sum of the hydrodynamic force and the magnetic force create a new vector which as in the case of the Brownian ratchet moves the cell out of the main stream direction.     

混合溶剂中多组分电解质溶液热力学性质的研究Ⅱ. HCl+NaCl+2-propanol+H2O体系15～45 ℃

本文在恒定异丙醇摩尔分数x=0.05的条件下, 应用电动势法测定无液体接界电池(A)和电池(B)的电动势:Pt, H_2(latm)|HCl(m), 2-propanol(x), H_2O(1-x)|Agcl-Ag (A)和Pt, H_2(latm)|HCl(m_A), NaCl(m_B), 2-propanol(x), H_2O(1-x)|AgCl-Ag (B)根据电池(A)电动势确定混合溶剂中的Ag-AgCl电极的标准电极电势, 讨论了HCl的迁移性质; 利用电池(B)电动势确定HCl在该体系中的活度系数γ_A, 在恒定总离子强度下, HCl的活度系数遵守Harned规则。在溶液组成恒定时, logγ_A是温度倒数1/T的线性函数, 讨论了混合物中HCl的相对偏摩尔焓, 计算了HCl的一级、二级和总介质效应。     

Thermodynamic properties of liquid bismuth—Lead alloys

On liquid Bi—Pb alloys emf measurements were carried out. From the emf data the thermodynamic properties were calculated. In the temperature range between 643 to 923 K no anomalies in the thermodynamic properties were found. The emf varies linearly with temperature and the activity of Pb shows a slight negative deviation fromRaoult's law. However, when H ^M /x is plotted against (1–x) the results are two staight lines which intersect at approximately 35 at% Bi. This could be interpreted that Bi—Pb melts change from one regular behaviour to another.Herrn Prof. Dr.K. L. Komarek mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Standard pH values for standardization of potentiometric sensors in 10% (w/w) acetonitrile-water mixtures

Reference value standards, pH(s) in 10% (w/w) acetonitrile-water solvent mixtures for 11 reference buffer solutions have been determined from reversible emf measurements of the cell Pt/Ag/AgCl/standard buffer + KCl, in acetonitrile-water/glass electrode, at 298.15 K. Values of ionization constants, required for above calculations, have been determined from reversible emf measurements of the cell Pt/Ag/AgCl/HA + A + KCl, in acetonitrile-water/glass electrode, in the same solvent composition and temperature.     

Modeling of electrochemical processes in solid oxide fuel cells

A mathematical model of electrochemical processes in a solid oxide fuel cell is presented. A procedure for the calculation of the current—voltage characteristic (CVC) taking into account the influence of the reagent concentration, pressure, and temperature is considered. The problem of calculation of the electromotive force (emf) and thermodynamic efficiency was studied in detail. The influence of the presence of carbon dioxide and water vapor in the anode gas on the emf and thermodynamic efficiency is analyzed. The method of measuring the CVC in an experiment at a constant fuel rate is briefly considered. The results of application of the calculation model are compared with the experimental data.     

Practical and theoretical aspects concerning the use of salt bridges in electrochemistry

The emf of electrochemical cells containing various sorts of salt bridges between various concentrations has been measured. The net diffusion potential over a salt bridge has been treated theoretically. An expression to calculate the net diffusion potential has been derived and tested on values estimated from the emf measurements. A merit factor has been calculated for a saturated KCl bridge separating two HCl solutions and compared with the merit factor estimated from emf measurements on the cell:Pt|Ag|AgCl, HCl(c₁)|KCl(sat)|HCl(c₂), AgCl|Ag|Pt The practical performance of two commonly used reference electrodes with salt bridges has been tested on emf measurements on KBr solutions.     

高精密饱和硫酸镉标准电池的研制

本文提出从工业品原料提纯制备高精密标准电池的方法。有40个酸性电池(硫酸浓度0.0490N),在1973～1979年间,于规定时间测定电动势值,每年平均上升0.33μV.初步分析了影响电池电动势值稳定性的各种因素,提出了实验数据。     

旋转磁场对质子交换膜燃料电池工作性能的影响

外加磁场可以提高PEM（Proton Exchange Membrane,质子交换膜）燃料电池的工作性能,本文通过在PEM燃料电池表面分别附加正方形梯度磁场、同极性组合圆柱形磁场以及异极性组合圆柱形磁场,分析旋转磁场、静态磁场以及未加磁场3种磁场环境下燃料电池的输出功率密度变化. 研究发现,外部磁场的分布规律不同,磁场的变动对燃料电池的影响也不相同,尤其是异极性组合磁场,旋转的磁场使燃料电池的最大功率密度提高了21.27%,明显高于加载静态磁场时提高的11.70%. 旋转磁场产生的效果与磁场旋转速度有关,提高转速有利于增强磁场对燃料电池工作性能的影响,当转速为30 r·min^-1时影响最大,随着转速进一步提高,影响效果逐渐变差。     

锂在[Mn~2O~4]中的电化学嵌入反应I.热力学性质

锂嵌入[Mn~2O~4]晶格形成嵌合物Li~xMn~2O~4。通过对不同温度(20~45℃)下的Li/Li~xMn~2O~4电池的库仑滴定曲线[EmF(x)]的测定, 可以求得该嵌入过程的嵌入熵、焓和自由能等热力学函数。在x<1.5时, 表现为很高的偏摩尔自由能, 在x=1/2和x=1时, 嵌入熵和焓表现为不连续性。热力学函数值与Li~xMn~2O~4的晶体结构关联。     

Magnetic field controlled optical phase retardation in a hybrid nematic cell

We have studied the phase retardation of linearly polarized light in a hybrid nematic liquid crystal cell. For a certain range of directions of the applied magnetic field the phase retardation is found to change non-monotonically with the magnetic induction. The observed behaviour is described rather well by the standard Frank elastic theory. The corrections resulting from subsurface deformations, which are characteristic both for second order elasticity approach and for surface field theory, are also considered. The analysis of the experimental data suggests that the presence of distortions in the zero-field director configuration is the necessary condition for the non-monotonic phase retardation, which implies that such an experiment could be used for the detection of misalignment of the effective pretilts in a nematic cell.     

Phase equilibria in the Tl-TlBr-Te system and thermodynamic properties of the compound Tl5Te2Br

The Tl-TlBr-Te composition region of the Tl-Te-Br phase diagram has been explored by DTA, X-ray diffraction, microhardness measurements, and electromotive force (emf) measurements relative to a thallium electrode in concentrations cells. The phase diagrams along a number of joins, the isothermal section at 400 K of the phase diagram, and a projection of the liquidus surface have been constructed. Extensive phase-separation areas, including a three-liquid-phase field in the Tl-TlBr-Tl₂Te subsystem, have been revealed. The homogeneity ranges and primary crystallization fields of phases have been mapped, and the coordinates of nonvariant and univariant equilibria in the T-x-y diagram have been determined. The standard thermodynamic functions of formation of the Tl₅Te₂Br compound and its standard entropy have been derived from emf data.     

Thermodynamics of the hydrogen-silver chloride cell in ethanol-water mixtures from −10 to +40°C

From emf E measurements of the reversible cell $$Pt|H_2 (g,1 atm)|HCl(m)|AgCl|Pt$$ at 0.01?1 in 70% (w/w) ethanol-water solvent mixtures over the temperature range from ?10 to +40°C, the standard emf E° of the cell with the related thermodynamic functions of the cell reaction and the mean molal activity coefficients of hydrochloric acid have been determined. The present E data at 70% (w/w) ethanol have been combined with earlier data at ≤50% (w/w) ethanol to be analyzed critically by a one-stage multilinear regression method leading to an optimized set of E° values for the range 0–70% (w/w) ethanol which are essential for the assessment of pH standards in these solvent media.     

Thermodynamics of Cadmium Chloride in 2-Butanone + Water Mixtures (5, 10, and 15 Mass%) from Electromotive Force Measurements

The emf (electromotive force) of the cell: CdHg_x (two phase) | CdCl₂ (m) | AgCl | Ag in 2-butanone + water mixtures (containing 5, 10, and 15 mass% 2-butanone) was measured at varying temperature (293.15, 298.15, 303.15, 308.15, and 313.15 K) and in the CdCl₂ molality range from 0.002 to 0.02 mol-kg^–1. At each temperature the standard emf of the cell (E_m^o) was determined using potentiometric data and literature values for the stability constants of chlorocadmium complexes. The E_m^o values were used to calculate the standard thermodynamic quantities for the cell reaction, the stoichiometric mean molal activity coefficients of CdCl₂, and the thermodynamic functions for CdCl₂ transfer from water to 2-butanone + water mixtures. The transfer process is a forced one and results in an entropy decrease. The transfer functions were compared to those obtained for the same electrolyte in acetone + water mixtures, as well as to those for HBr in ketone + water mixtures. Medium effects upon CdCl₂ were calculated and discussed for the examined mixtures (2-butanone + water).     

Dynamically Harmonized FT-ICR Cell with Specially Shaped Electrodes for Compensation of Inhomogeneity of the Magnetic Field. Computer Simulations of the Electric Field and Ion Motion Dynamics

The recently introduced ion trap for FT-ICR mass spectrometers with dynamic harmonization showed the highest resolving power ever achieved both for ions with moderate masses 500?C1000?Da (peptides) as well as ions with very high masses of up to 200?kDa (proteins). Such results were obtained for superconducting magnets of very high homogeneity of the magnetic field. For magnets with lower homogeneity, the time of transient duration would be smaller. In superconducting magnets used in FT-ICR mass spectrometry the inhomogeneity of the magnetic field in its axial direction prevails over the inhomogeneity in other directions and should be considered as the main factor influencing the synchronic motion of the ion cloud. The inhomogeneity leads to a dependence of the cyclotron frequency from the amplitude of axial oscillation in the potential well of the ion trap. As a consequence, ions in an ion cloud become dephased, which leads to signal attenuation and decrease in the resolving power. Ion cyclotron frequency is also affected by the radial component of the electric field. Hence, by appropriately adjusting the electric field one can compensate the inhomogeneity of the magnetic field and align the cyclotron frequency in the whole range of amplitudes of z-oscillations. A method of magnetic field inhomogeneity compensation in a dynamically harmonized FT-ICR cell is presented, based on adding of extra electrodes into the cell shaped in such a way that the averaged electric field created by these electrodes produces a counter force to the forces caused by the inhomogeneous magnetic field.     

On the mitochondrial aspect of reactive oxygen species action in external magnetic fields

Some retinoids or porphyrins can form radical pairs, alter transfer of electrons, and increase synthesis of reactive oxygen species in the mitochondrial respiratory chain. This leads to cell damage and apoptosis. We propose that co-application of an external static magnetic field of several to several hundreds miliTesla (mT) can enhance those effects by further alteration of electron flow in the mitochondrial respiratory chain, facilitation of forbidden transitions from the triplet to the singlet state of retinoid or porphyrin radicals, and modification of radical pair amount. Since electron flow in the mitochondrial respiratory chain seems to possess fractal dynamics, the magnetic field can initiate self- organization of the flow into more regular patterns, and create optimal conditions for damage of cancer cells without any detriment for the normal counterparts. External low magnetic field should improve effectiveness and selectivity of retinoid chemoprevention or porphyrin photodynamic therapy.     

Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed.