Foreign Electrolytes Research Articles

Influences of Growth Species and Inclusions on the Current–Voltage Behavior of Plasma Electrolytic Oxidation: A Review

Plasma electrolytic oxidation (PEO) has attracted increasing attention since the transportation industry adopts more lightweight metal components and requires an improved version of anodizing for surface protection. In response to the demand, researchers enrich the technical connotation of PEO through diversifying the growth paths and adopting new precursors. Foreign electrolyte additives, involving ceramic and polymeric particles, organic dye emulsions, are incorporated to accomplish various goals. On the other hand, significant progress has been made on comprehension of softening sparks; denoting the adverse trend of growing discharge intensity can be re-routed by involving cathodic current. I–V response shows the cathodic pulse current not only cools down the ensuing anodic pulse, but also twists the coating conductivity, and the residuals of twists accumulate over a long time frame, plausibly through oxide protonation. Thus, the cathodic current provides a tool to control the discharge intensity via integration of the coating conductivity deviations. So far, these cathodic current studies have been performed in the electrolytes of KOH and Na2SiO3. When exotic additives are included, for example Cr2O3, the cathodic current effect is also shifted, as manifested in remarkable changes in its current–voltage (I–V) behavior. We anticipate the future study on cathodic current influences of inclusion shall lead to a precise control of micro arc.

Solid Phase Extraction of Copper , Cadmium and Lead Using Amberlite XAD-4 Resin Functionalized with 2-Hydroxybenzaldehyde Thiosemicarbazone and its Application on Green Tea Leaves

A new chelating resin, 2-hydroxybenzaldehyde thiosemicarbazone loaded XAD-4, was synthesized and characterized by FT-IR and elemental analyses. The synthesized resin was used for solid phase extraction (SPE) and preconcentration of Cu 2+ , Cd 2+ , and Pb 2+ from aqueous solution, where the metal ions were subsequently determined by graphite furnace atomic absorption spectrometry (GF-AAS). The optimum pH for preconcentration and separation of these metal ions was found to be 6.00. Optimum flow rate for quantitative sorption of the metal ions on functionalized resin was found to be 1 mL/min whereas 2 M nitric acid was selected as the eluent for quantitative release of the three metal ions from the resin column. The maximum adsorption capacity of the functionalized resin was found to be 3.5, 6.1, and 11.26 mg/g for Cu 2+ , Cd 2+ , and Pb 2+ , respectively. The detection limits for these metal ions are 0.87, 0.95, and 1.09 µg/L, respectively and limits of quantification are 1.12, 1.29, and 1.16 µg/L, respectively. The sorption half time (t1/2) was found to be 6 min for Cu 2+ and Cd 2+ and 8 min for Pb 2+ . Tolerance limits for various foreign electrolytes have also been investigated. A high preconcentration factor (~100) and low relative standard deviation ≤ 5% (n=3) values were obtained. Under optimum conditions, recovery of all metal ions was found to be nearly quantitative. The validation of the procedure was carried out by analysis of certified reference materials. The functionalized resin is highly stable and can be reused more than 100 times. The newly developed method was applied to the separation, preconcentration and determination of Cu 2+ , Cd 2+ , and Pb 2+ in tea leaves

Specific features of electrification of weakly conducting media flowing through a plane channel with walls of different electrochemical properties

A flow of a multicomponent weakly conducting medium in a plane channel is studied. The medium consists of a carrier dielectric liquid and a small admixture of ions. The channel walls have different electrochemical properties. It is shown that, in the case of a weak foreign electrolyte, the volume and surface electrochemical processes are nonequilibrium along the entire length of the channel. It is also shown that in the saturation state there exists a finite negative charge flow through one of the walls and a positive charge flow of the same magnitude through the other wall.

Formation of an electric charge in a dielectric fluid above a rotating disk

A plane metal disk rotating at a constant angular velocity is considered. Above the disk, there is a dielectric fluid containing a small amount of a foreign electrolyte. The electrolyte contains positive and negative ions and is assumed to be strong. The charging of the fluid is determined by the electrochemical reactions that take place at the disk surface. The effect of an electric field on the charging process is taken into account.

New Baw Sensors for Dissolved Gases

Novel BPES (Bulk Acoustic Wave Piezoelectric Crystal with Electrodes in Series) sensors for dissolved gases are proposed. They are based on the non-mass effect response of the sensor to the change in conductivity of the internal electrolyte solution of the sensing device, caused by the dissolved gas. Several kinds of such sensors are described for dissolved sulphur dioxide, nitrogen dioxide, carbon dioxide, and ammonia. Factors affecting the sensor performance are discussed, including buffer composition, unreacted foreign electrolyte in the internal solution, osmotic effect, and cell constant of the probe. This type of gas sensing device is advantageous over conventional potentiometric sensors for dissolved gases based on ion-selective electrodeS in their high sensitivity, fast response, not requiring either a reference electrode or a fragile glass pH electrode, and simple construction. Their applications in medicine, environmental science, food technology, and enzymology are provided.

Limiting Currents for Steady-State Electrolysis of an Equilibrium Mixture, with and without Supporting Inert Electrolyte

An exact treatment derives the steady-state limiting current of a one-electron reduction for the N ⇌ O(+) + A(-) mixture at a hemispherical microelectrode. Either or both of the neutral N and cationic O(+) species may be electroactive. A supporting salt is present at any concentration, including zero or excess; its ions are electropassive and do not interact with the other solutes or each other. The various species are treated as having distinct diffusivities, linked to their mobilities through the Nernst-Einstein relationship. Universal electroneutrality is assumed. The predictions of the model are compared with published experimental data on the reduction of aqueous weak acids; agreement is excellent at intermediate, but poor at low, support ratios. Analysis of the unsupported case shows that the neutral N species dissociates in a narrow zone close to the electrode, and the injection of ions there serves to increase the electric field in the outer region of the transport zone. This enhances cationic migration enormously, leading to an unsupported limiting current that is much more than double the supported value. However, the limiting current is drastically diminished by traces of foreign electrolyte. Curiously, the limiting current with full support adopts the same value when equilibration is fast as when it is very slow, although the mechanisms are totally different.

Theory of the surface acoustic wave/impedance sensor system and its application to the end-point determination in titrimetry

Theory and characteristics of the surface acoustic wave (SAW)/impedance sensor system in electrolyte solution are reported. This kind of sensor was constructed by a 62-MHz SAW resonator and a pair of conductive electrodes in series. By using the circuit network analysis theory, two oscillation equations were derived and used to explain the frequency-shift response to solution conductance. Results showed that the sensor possesses high sensitivity to the solution conductivity and can be applied to conductivity measurements in solution. Its sensitivity and accuracy could be improved in the presence of a large amount of unreacting foreign electrolytes. The sensor was successfully applied to four types of titration (acid-base, precipitation, oxidation-reduction and compleximetric titration) by monitoring the frequency-shift response. Factors influencing the frequencimetric titration curve were also investigated. Analytes at levels down to 1 × 10 −5 M could be determined by the proposed titration technique. The total acidity in several food samples was determined and the results were consistent with those obtained by conventional methods.

Circuit network analysis method applied to surface acoustic wave impedance system in liquids

The circuit network theory was applied to analyse a surface acoustic wave (SAW) impedance system constructed from a 61-MHz SAW resonator and a pair of conductive electrodes in series. Two oscillation equations were derived and used to explain the effects of solution capacitance and cell constant on the frequency characteristics. The effects of the solution density and the viscosity on the frequency response of the SAW impedance system were also investigated. The SAW impedance system can be applied to conductivity measurements in solution with a high concentration background of foreign electrolytes.

Behaviour of series piezoelectric sensor in electrolyte solution: Part II. Applications in titrimetry

The applications of a series piezoelectric sensor for end-point determination in frequencimetric titrations, including neutralization, precipitation, complexation and redox titrations, are reported. The method is based on the fact that a series piezoelectric sensor shows a sensitive and selective frequency response to changes in conductivity of solution and can be applied to sample solutions containing large amounts of unreacted foreign electrolytes.

Behaviour of a series piezoelectric sensor in electrolyte solution: Part I. Theory

The theory, methodology and behaviour of a piezoelectric and conductivity sensor in electrolyte solution are reported. The sensor was constructed by connecting an AT-cut piezoelectric quartz crystal and a conductivity electrode in series. It has a sensitive and selective frequency response to the change in solution conductivity and permittivity. The relationship between frequency and solution conductivity was derived according to the oscillating theory and supported by the experiments. The effects of the solution conductivity, permittivity, temperature, density and viscosity, cell constant of the conductivity electrode, foreign electrolytes and the operating voltage of the integrated circuit-TTL oscillator on the behaviour of the series piezoelectric sensor were investigated. The sensor possesses high sensitivity to the solution conductivity and a low frequency-temperature coefficient, and its frequency depends very little on the operating voltage and density and viscosity of the solution. Its sensitivity and accuracy were improved in the presence of foreign electrolytes.

Investigation of the Polyborate Equilibria in Aqueous solutions by 11B-NMR and Raman spectroscopy

The aim of this work was to extend our knowledge of the ions which are involved in equilibria in concentrated aqueous solutions of borates [1, 2]. The 11B nuclear magnetic resonance spectra of sodium, potassium and ammonium polyborates in D 2O solutions, - as a function of concentration and pH value -, provide information of the hydrolysis equilibria. Two NMR signals are observed in the aqueous solutions of the pentaborates Na[Ba 5O 6(OH) 4], K[B 5O 6(OH) 4] and NH 4[B 5O 6(OH) 4], while only one NMR line is recorded in the solutions of the tetrabirates Na 2[B 4O 5(OH) 4] and (NH 4) 2[B 4O 5(OH) 4]. A solution of (NH 4) 2[B 4O 5(OH) 4] at pH 7 shows two lines again [3]. The next step was to study the Raman spectra of solid H 3BO 3, Na 2[B 4O 5(OH) 4]·8H 2O, K[B 5O 6(OH) 4]·2H 2O and of Na[B(OH) 4] as well as of borax in aqueous solutions as a function of concentration and pH, recorded between 300 and 1500 cm −1. For comparisons the Raman spectra of solid (NH 4) 2[B 4O 5(OH) 4]·2H 2O, β-NH 4[B 5O 6(OH) 4]·2H 2O, NH 4[B 5O 6(OH) 4]·0.67H 2O and NH 4[B 5O 6(OH) 4] were considered. In solution, all lines in the Raman spectra could be assigned and the degree of depolarization measured. The assigned Raman frequencies can be used for the identification of unknown BO lines and therefore of unknown borate structures [4]. In the last step the influence of some series of foreign electrolytes in various concentrations of the equilibria of the borate species in a 0.5 M solution was investigated by Raman spectroscopy. On the one hand, addition of the foreign electrolyte solutions has a dilution effects, so that in many of these systems there exists only the [B(OH) 4] −/other hand, the effect is sometimes a forcing of the equilibrium in favour of the polyborate formation with the triborate ions [B 3O 3(OH) 4] − and [B 3O 3ion [B 4O 4(OH) 5] 2− is present only to a minute extent, while the formation of the pentaborate ion [B 5O 6(OH) 4] − is presented the most [5].

DYEING OF CELLULOSE BY DIRECT DYE IN AQUEOUS SODIUM ALGINATE SOLUTION

Dyeing of Cotton by Chrysophenine G (C. I. Direct Yellow 12) in aqueous sodium alginate solution has been studied. The results show the increasing dye absorption with increasing sodium alginate as described before. In this report, the results have been interpreted by reference to the parameters affecting the free energy of the dyeing and the relevant model available for explaining this dyeing system. The effect of sodium alginate (polyelectrolyte) on the absorption equilibrium of dye by cotton has been compared with that of sodium chloride (inorganic salt) in terms of the Donnan membrane equilibrium theory, assuming that sodium alginate is present only in the “bulk solution” defined in the unimolecular absorption model of cellulose. We have considered that dyeing of cotton by direct dye in aqueous sodium alginate solution is similar to the dyeing in the absence of foreign electrolyte and that by the membrane equilibrium the dye has been concentrated into the internal solution of cotton for the presence of sodium alginate in the bulk solution.

Thermodynamics of binding of methyl orange and its homologs by poly(vinylpyrrolidone): The effect of inorganic electrolytes

AbstractThe extent of binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been measured in aqueous solutions of inorganic electrolytes such as NaCl, LiCl, NaSCN, and NaClO4 by an equilibrium dialysis method. The effect of the salts on the first binding constants and the thermodynamic functions which are accompanied by the dye—polymer association process was investigated relative to the corresponding values in the absence of such salts. It was found that in aqueous solutions of NaCl and LiCl the enthalpy change accompanying the binding is small and the largest contribution to the free energy of binding is from the positive entropy gain. For NaSCN and NaClO4, the values of ΔF° and ΔH° were both large and negative and the value of ΔS° was small and negative. Thus, the favorable free energy for the complex formation was due entirely to the negative enthalpy term. These characteristics of the thermodynamic quantities are discussed in terms of changes in structural properties of water in the vicinity of the binding entities and conformational changes of the polymer to which the dye is bound due to the added foreign electrolytes.

Fluorimetric investigations of interactions with macromolecules in solution

AbstractBlancophor dyes show a considerable increase in fluorescence yield upon adsorption onto poly(vinyl pyrrolidone). A fluorometric method was used for the quantitative determination of adsorption in polymer‐dye solutions. The adsorption isotherms differ from Langmuir adsorption behavior, and an adsorption isotherm is derived by taking into account the electrostatic repulsion potential of the adsorbed Blancophor ions. Adding foreign electrolytes causes a decrease in the electrostatic potential, which is independent of the species of salt, and is characterized by the Debye‐Hückel shielding parameter. The macromolecule with adsorbed ions represents a good model for a polyelectrolyte having the capability of altering or readjusting its charge density. Macromolecular sizes measured by various methods are related to the effective potential on the surface of the macromolecule. The expansion of the poly(vinyl pyrrolidone) molecule caused by the electrostatic repulsion of the adsorbed Blancophor ions was investigated by viscosity and light‐scattering measurements. Relationships among charge on the macromolecule and screening by added salt ions, on the one hand, and the molecular weight, the end‐to‐end distance, and the second virial coefficient, on the other hand were found and interpreted.

The Electron Spin Resonance of the Mn2+ Ion in Aqueous Surfactant Solutions

Abstract The ESR spectrum of the Mn2+ ion in an aqueous solution of a surfactant is affected by its concentration. Sodium dodecyl sulfate and sodium decyl sulfate were employed as surfactants in this study. The linewidth of the Mn2+ ion is independent of the concentration of the surfactant in the low-concentration range, but it increases over a certain concentration range and then becomes constant. Two values of CMC were observed by measurements of the conductivity corresponding to the concentrations, where the linewidth of Mn2+ changed abruptly with the concentration of the surfactant. The linewidth broadening above the first CMC was interpreted as being due to the formation of an outer-sphere complex of the Mn2+ ion with a surfactant micelle. The interaction between the counterion and micelle was also investigated on the basis of the ESR spectra of the Mn2+ ion with regard to the effects of the kind of surfactant, the temperature, foreign electrolytes, etc.

Studies on the Mixed Gels of Silica, Alumina and Ferric Oxide

AbstractSol‐gel transformation of mixed gels of silica, alumina and ferric oxide has been studied by determining the variations in pH with time of dialysis. For silica‐alumina mixtures a pH of 2.9 is invariably reached irrespective of the alumina content of the mixtures. The amount of alumina present in the mixture influences the time of setting of the gel to a very great extent and it decreases with increase of the alumina content of the mixtures. These results have been explained in light of chemical interaction between the two gels to give aluminosilicates as well as in terms of controlled coagulation phenomenon with alumina behaving as a foreign electrolyte for bringing about the gelation of silicic acid.The results of silicic acid, ferric oxide gel forming mixtures are altogether different. In this case the time of gelation increases with the increase in the amount of ferric oxide in the gelation mixture, while a pH of 4.2 is reached irrespective of the amount of ferric oxide present. No evidence for the formation of ferric‐silicate is obtained nor the gelation of these mixed sols can be explained in terms of controlled coagulation.The colloidal silica appears to act as protective colloid for the highly acedic ferric oxide sol. Viscometric and pH metric studies on the addition of alumina sol to mixtures of ferric oxide and silica sols indicate that alumina competes with ferric oxide in the formation of mixed gels. Here, too a pH of 2.9 is invariably reached irrespective of the alumina content in the mixed gels.

Influence of foreign electrolyte concentration in square wave polarography

In addition to the established effects of the nature of the foreign electrolyte on the current voltage curves in d.c. polarography, a pronounced dependence of the peak currents on the concentration of the foreign electrolyte is determined in square wave polarography. A marked effect is due to the structure of the double layer. This concentration effect is shown by examples for polarographically reversible and irreversible reductions. Results are of particular importance for applications of this method in microchemical and trace analysis work, since they show that a considerable increase in the sensitivity of indication of irreversible reactions is obtained without the indication of reversible reactions being impaired if, contrary to earlier recommendations, solutions of low foreign-electrolyte content are used. The charging current waves occurring at a high resistance of the cell circuit are described.

The reaction between alkali molybdates and mineral acids

In spite of extensive study, the precise nature of the reaction between alkali molybdates and mineral acids has been a controversial subject for several decades. A precise electrometric and spectrophotometric study has now shown that there is definite evidence for only one of the many proposed aggregation processes, namely that of molybdate to tetramolybdate. By following the effects of foreign electrolytes on the process, it has been found that activity and hydrolysis effects complicate the main reaction. The nature of “molybdate reagent” solutions is discussed with respect to these findings.

Kinetics of Activation Controlled Consecutive Electrochemical Reactions: Anodic Evolution of Oxygen

The kinetics of activation controlled electrode reactions differ from those of chemical kinetics by the potential dependence of the rate constant of a step involving charge transfer and the constancy of concentration of reactants in the initial state. A method is proposed whereby an expression for the kinetics of an electrode reaction containing any number of intermediate steps may be obtained. The method is applied to five paths for the electrolytic evolution of oxygen at anodes and yields limiting expressions for the dependence of the current density (or rate) of the reaction upon electrode potential which are diagnostic of the various rate controlling steps assumed. If discharge of OH′ or H2O molecules is rate determining, the Tafel slope is 2RT/F at overpotentials > 50 mv. If some other reaction involving charge transfer is rate determining, two possible Tafel slopes, each independent of potential in its range of applicability, occur, depending upon degree of coverage of the electrode with intermediate products. If a reaction involving no charge transfer is rate determining, a number of Tafel slopes is indicated, each characteristic of the rate controlling reaction, and an activation controlled limiting current density is possible. Quantitative conditions for change of mechanism with current density are evaluated. For the initial reaction of a consecutive series to be rate determining it suffices that the rate constant for the backward partial reaction of this step be limitingly small compared with other rate constants in the series; for the last reaction to be rate controlling, the rate constant of its forward partial reaction must be limitingly small; for any other reaction in the series, both backward and forward rate constants of the rate determining reaction must be limitingly small. The rate of the anodic oxygen evolution reaction as a function of pH is evaluated, taking into account concentration and foreign electrolyte effects on the electrokinetic potential at the electrode-solution interface. The results enable the discharging entity in solution to be distinguished. Former data are reinterpreted from the criteria of mechanism deduced.

Influence of Foreign Electrolytes and Temperature in Electrochemical Kinetics. An Application of Polarography and Voltammetry at Constant Current

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfluence of Foreign Electrolytes and Temperature in Electrochemical Kinetics. An Application of Polarography and Voltammetry at Constant CurrentPaul Delahay and Calvin C. MattaxCite this: J. Am. Chem. Soc. 1954, 76, 21, 5314–5318Publication Date (Print):November 1, 1954Publication History Published online1 May 2002Published inissue 1 November 1954https://doi.org/10.1021/ja01650a016RIGHTS & PERMISSIONSArticle Views86Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (563 KB) Get e-Alerts Get e-Alerts