Relation between potentials of Li,K/Li+,K+ dynamic reference electrode and HF/H2 gas electrode in a molten LiF-KF system

Potential of Li, K/Li⁺, K⁺ dynamic reference electrode has been measured against HF/H₂ gas electrode of several partial pressures in a LiF-KF eutectic melt. Experimental results show that this dynamic reference electrode can be used as a conventional reference electrode, since the thermodynamic significance of the potential of HF/H₂ gas electrode is clear.     

Concentration dependence of thermoelectric powder in a molten salt system

This paper first presents thermodynamic considerations for the concentration dependence of the thermoelectric power in a molten salt system, and then presents experimental data for the Cu/Cu⁺ and Ag/Ag⁺ couples in a LiCl—KCl eutectic melt. The experimental data show good agreement with the derived thermodynamic equation.For the thermodynamic treatment, the approach of Førland and Ratkje was chosen, since it is thermodynamically rigorous.     

A solid silver iodide electrode as silver ion indicator in molten nitrates

Qualitative reasoning suggested the possibility of using silver iodide as indicator electrode for silver ions in molten media. The idea has been confirmed by employing a rotating disk electrode, in which the electroactive part was a AgI-tablet, for the determination of the diffusion coefficient of silver ions in molten potassium and sodium nitrates.     

Stability of a boron-doped diamond electrode in molten chloride systems

Stability of a boron-doped diamond as an oxygen evolution electrode material was evaluated at 773 K in molten LiCl–KCl (58.5:41.5 mol%), LiCl–KCl (75:25 mol%), LiCl–CaCl₂ (64:36 mol%), LiCl–NaCl–CaCl₂ (52.3:13.5:34.2 mol%). In molten LiCl–KCl systems, the BDD is stable at 773 K regardless of the concentration of oxide ion and the composition of the melt. In molten LiCl–CaCl₂ and LiCl–NaCl–CaCl₂, the BDD electrode is less stable than in molten LiCl–KCl systems.     

Validation of an ion selective electrode system for the analysis of serum fluoride ion

A high impedance unit was developed for use with a fluoride/pH electrode system for the measurement of serum fluoride. The linearity, accuracy, precision and detection limit of the system is reported. At a pH of 1.55, the system was linear over a range of serum fluoride concentrations up to 100 μmol l^-1, with a lower limit of detection of 0.3 μmol l^-1. Recoveries at this pH were 94-105% in the range 2.6-100 μmol l^-1. Within-run CVs ranged from 4.2% at a level of 2.3 μmol l^-1 to 1.2% at a level of 55.7 μmol l^-1, while day-to-day CVs ranged from 12.8% at a level of 2.2 μmol l^-1 to 4.6% at a level of 51.7 μmol l^-1. The system demonstrated a rapid response time and has the potential for a smaller sample size requirement with alternative electrode shape. Continued development of this unit into an automated fluoride ion selective electrode system is recommended, since the measurement of serial serum fluoride samples is of greatest importance in assessing the impact of new anaesthetic agents on renal function.     

Measuring mercury ion concentration with a carbon nano tube paste electrode using the cyclic voltammetry method

A simply prepared carbon nano tube paste electrode (CNTPE) was utilized for monitoring mercury ion concentration using the cyclic voltammetry (CV) method and the square wave anodic stripping voltammetric (SWASV) method. The CNTPE was compared with various conventional electrodes. The CNTPE method was applied to determine the concentration of trace levels of Hg(II) in several water samples, which yielded a relative error of 0.6% with a concentration of 0.20 mg L^–1 Hg(II). It was deposited at –0.5 V (vs Ag/AgCl), which was subsequently reduced to +0.20 V to strip it on the CNTPE. The optimal experimental conditions for the analysis were found to be as follows: pH value of 4 for the medium; deposition potential of –0.5 V; deposition time of 210 s; SW frequency of 40 Hz; SW amplitude of 100 mV, and step potential of 25 mV. Given these optimum conditions, a linear range was observed within the concentrations of 1.0–25.0 g L^–1 and 40.0–200.0 g L^–1. The detection limit was found to be 0.42 g L^–1.     

Water and oxide ions concentration dependence of the specific mass and conductance of the molten NaOH-KOH eutectic mixture

The conductivity of the molten NaOH-KOH eutectic mixture was measured as a function of the oxoacidobasicity of the melt at concentrations ranging from a mole fraction of sodium oxide of 0.16 to a mole fraction of water of 0.09.The conductivity of the melt is enhanced when the water concentration increases while it decreases when oxide ions are dissolved into the liquid.Relationships between the conductivity and the concentrations of water or oxide ions are proposed which are in perfect agreement with the experimental results. A proton transfer conduction mechanism is suggested.The water concentration dependence of the specific mass of the melts has been measured in the concentration range extending from the dry mixture to a mole fraction of water of 0.09.     

Performance of fluidized bed electrode in a molten carbonate fuel cell anode

A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated in a molten carbonate fuel cell anode with an O₂/CO₂/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow rates of H₂, O₂ and CO₂, choosing suitable nickel particle content together with appropriate O₂/CO₂ ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56 mA·cm⁻² is achieved under optimum performance as follows: a cylindrically curved nickel plate current collector, nickel particle content of 7.89%, the reaction temperature of 923 K, H₂ flow rate of 275 mL·min⁻¹, O₂/CO₂ flow rate of 10/20 mL·min⁻¹ and O₂/CO₂ ratio of 1 : 2.     

On the potential of mean force of a sterically stabilized dispersion

The potential of mean force (PMF) is the total free energy of a many-body colloidal system, and consequently it includes all the interactions the colloids experience due to collisions with themselves and with the solvent. Here, the PMF of a colloidal dispersion under various circumstances of current interest, such as varying solvent quality, polymer coating thickness, and addition of electrostatic interaction, is obtained from radial distribution functions available from the literature. They are based on implicit-solvent, computer simulation studies of a model TiO₂ dispersion that takes into account three major components to the interaction between colloidal particles, namely van der Waals attraction, repulsion between polymer coating layers, and a hard-core particle repulsion. In addition, a screened form of the electrostatic interaction was included. It is argued that optimal conditions for dispersion stability can be derived from a comparative analysis of the PMF under the different situations studied. This thermodynamics-based analysis is believed to be more accessible to specialists working on the development of improved colloidal formulations than that based on the more abstract, radial distribution functions.     

Adsorption of 1,1,3,3-tetramethyl-2-thiourea on the mercury electrode: dependence on the concentration of the base electrolyte

Adsorption of 1,1,3,3-tetramethyl-2-thiourea (TMTU) on a mercury electrode from 1, 0.5, and 0.1 M NaClO₄ is described by means of the adsorption isotherms constants calculated from the surface pressure as a function of electrode charge density and adsorbate bulk concentration. The adsorption parameters for the double-layer were calculated based on the data from the differential capacity-potential curves. The values of the relative surface excess increase with an increase in the concentration of NaClO₄. In each system studied, significantly smaller values of Γ_S for σ_M<0 were obtained, compared with the corresponding values for σ_M≥0. At positive values of σ_M, the values of ΔG° obtained from either the Frumkin or the Flory-Huggins isotherm are similar. However, the values of the parameter A obtained from the Flory-Huggins isotherm are lower.The dependence of Φ^M−2 on the relative surface excess at a constant charge density is nonlinear. The rectilinear segments of these dependences obtained for smaller values of Γ′ were analyzed in order to calculate the electrostatic parameters of the inner layer.     

Dependence of ion concentration on growth of crystallites formed during discharge of an idealized electrode

Calculations are made showing the time dependence of the ion concentration of an electrolytic solution in which a model electrode is immersed. The model electrode consists of two parts: firstly of the ion source function which can be thought to be calculated as an average of an amount of ion sources statistically distributed over a volume, secondly of the ion sink function which is calculated from size and quantity of crystallites formed by the discharge product. The crystallites are assumed to be spherical and of uniform size. The special case of diffusional controlled growth is considered explicitly. The problem is reduced to the discussion of two differential equations and the initial conditions by which the time dependence of concentration and volume of the discharge product is controlled. After having reached a maximum in certain cases the concentration decreases slowly. When time proceeds the volume of the discharge product becomes asymptotically linear with time.The range of applications to real electrodes is discussed. It is shown that a great amount of crystallites of the discharge product is desirable in order to keep the ion concentration and thus the concentration overvoltage low.     

Metal ion concentration,time, and pH dependence of metal ion binding to a transferrin metalloprotein affinity chromatography (MAMC) matrix

The adsorption of transition metal, lanthanide, and actinide ions to avotransferrin (conalbumin) immobilized to sepharose (via the cyanogen bromide method) has been examined. Adsorption of ions as a function of time and adsorption isotherms at pH 8 have been determined and analyzed using the Freundlich model, distribution coefficients between the pH vales 2 and 9 have been measured. The results indicate that immobilization of the protein has little effect on its interactions with metal ions compared with the protein in solution, and important prerequisite for use of this matrix in metalprotein affinity metal homatography (MAMC).     

Kinetics and mechanism of the magnesium electrode reaction in molten magnesium chloride

Using electrochemical impedance spectroscopy (EIS) and relaxation method with galvanostatic perturbation (RM) the kinetics and mechanism of the magnesium electrode reaction in pure molten M9Cl₂ have been determined at several temperatures. A three-step electrode process has been found, the high frequency process being pure charge transfer with the low frequency process showing mixed charge transfer-diffusion character. The low frequency step has also been treated as a preceding chemical reaction followed by charge transfer. On the basis of the corresponding exchange current densities and Warburg diffusion impedance, a mechanism of the overall electrode reaction in this melt is proposed.     

The application of pulsed potential and pulsed current to a rotating disc electrode system

This paper is concerned with mass transfer to a rotating disc electrode (RDE) under pulsed potential and pulsed current conditions. For the case of pulsed potential, a numerical solution is presented to calculate the instantaneous current density for intermediate and large cycle times and an asymptotic solution for short cycle times. The special case of applying a step potential is then presented. The magnitude of the step current for a given transition time is calculated from the numerical solution by Viswanathanet al. for the pulsed current case. Comparison is made between the present results and various approximate solutions from the literature.Nomenclature c concentration of reacting ion - c _i,c interfacial concentration and bulk concentration, respectively - C dimensionless concentration defined in Equation 11 - C _n,C _{n 1},C _{n 2} coefficients of an infinite series - D diffusion coefficient of reacting ion - F Faraday's constant - i current density - i _ave average current density over the entire cycle - (i _dc)_l d.c. limiting current density - i _step step current density - K dimensionless velocity defined in Equation 11 - K _n defined in Equation A5 - n number of electrons transferred - R _n dimensionless concentration as a function of - t time - t _n defined in Fig. 1 - t _tr transition time - v _z axial velocity - z axial co-ordinate - a dummy variable - _n defined in Equation 20 - thickness of the Nernst diffusion layer - dimensionless axial co-ordinate defined in Equation 12 - _{n 1}, _{n 2} eigenvalues - _n defined in Equation 29 - dimensionless time defined in Equation 12 - ₁, _c, _tr dimensionless on-period, cycle period and transition time respectively - a function of axial co-ordinate defined in Equation A4     

A study of the effect of surfactants on electrode processes in molten salts

The effect of various organic substances on cathodic processes in the K,Na∣SCN, K,Li∣NO₃, 2Al,Na∣Cl and K,Na,Li,Cs∣Cl melts has been studied by ac polarography, spectroscopic and potentiometric methods as well as by surface tension and differential capacity measurements. It has been shown that adsorption of organic substances on Pt electrodes takes place in the melts at temperatures up to 300°C and that the substances studied should be regarded as surfactants. Some surfactants were used for obtaining aluminium electrodeposits with given properties from the 2Al,Na∣Cl melt.     

氯离子选择性电极测定钻井废水中的氯离子含量

利用氯离子选择性电极测定钻井废水中的氯离含量，分别用两种方法对钻井废水进行了预处理．氯离子在0～250mg／L的范围内线性关系良好，相关系数为0．9968，并且重现性和选择性良好，精密度与准确度较理想。     

The mechanism of the nitrate (platinum) electrode in molten alkali nitrates

The mechanism for the nitrate electrode, (Pt)NO₂, O₂/NO^?₃, is shown to be: NO^?₂ = NO₂ + e; NO₂ = NO + $\text{1}\text{2}$O₂; NO^?₃ + NO = NO^?₂ + NO₂; with the overall reaction: NO^?₃ = NO₂ + $\text{1}\text{2}$O₂ + e.     

On the frequency- and temperature- dependence of the conductivity of molten salts

The frequency dependence of the specific electrical conductivity, caused by the electrode polarization, was determined with a platinum cell. The polarization-free conductivity values of some individual molten salts, measured at 200 kHz, were compared with the literature data.     

Electrochemical detection of copper ion using a modified copolythiophene electrode

This paper studies the detection of copper ions by using an iminodiacetatic acid (IDA) modified conducting copolymer electrode. The copolymer film comprising 3-methyl thiophene (3MT) and 3-thiophene acetic acid (3TA) was chosen as the selective metal cation sensing electrode. The carboxylic group of the copolymer was modified to produce IDA group for metal ion capture. The modified electrode was used for the electrochemical analysis of trace copper ions by square wave voltammetry (SWV) technique. The electrode was found to be highly selective to Cu²⁺ in the range of 0.1-10 μM. The modified electrode offered an excellent way, with a high stability and reusability, for selective determination of Cu²⁺ in a solution of mixed metal ions.