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Electroanalytical Methods
Published in Thomas J. Bruno, Paris D.N. Svoronos, CRC Handbook of Basic Tables for Chemical Analysis, 2020
Thomas J. Bruno, Paris D.N. Svoronos
The following table lists the standard electrode potentials (in V) of some electrodes of the second kind [1–3]. These consist of three phases. The metal is covered by a layer of its sparingly soluble salt and is immersed in a solution of a soluble salt of the anion. Equilibrium is established between the metal atoms and the solution anions through two partial equilibria: one between the metal and its cation in the sparingly soluble salt and the other between the anion in the solid phase of the sparingly soluble salt and the anion in solution. The silver chloride electrode is preferred for precise measurements.
Voltage, Capacitors, and Batteries
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
where Eredox0=−qVredox0 is the energy of the redox couple at cox = cred, with respect to the RE. Redox potentials obtained from electrochemical measurement are listed in standard tables with respect to SHE, but in practice the electrode potential is often reported with respect to the reference electrode that was actually used as the reference. A silver-silver chloride electrode (Ag/AgCl), for example, has a potential V = +0.222 V positive with respect to SHE. For the saturated calomel electrode (SCE) V = +0.244 V versus SHE. A few REs are shown in Figure 2.7.
Electrochemical Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
Each ion selective electrode requires a reference electrode which provides a constant known voltage against which to measure the changes in voltage of the indicating electrode. There are different configurations of reference electrodes available, since the reference electrode filling solutions may interfere with some analyses. Each reference electrode has a porous plug which serves as a contact between the solution and the internal electrode filling solution. While a very small quantity of solution diffuses through this plug, it can be enough to change the measured concentration in the sample. In addition, a precipitate of insoluble salt, formed when the sample and the filling solution come into contact, can plug the channel between them, so that the electrode does not function properly. A silver/silver chloride electrode is often used as a reference electrode. This electrode may contain a filling solution of potassium chloride saturated with silver chloride, which can cause a problem if the sample is being analyzed for chloride. Enough chloride ion may pass into the solution to interfere with an accurate measurement. A double junction reference electrode has a second filling solution in an outer electrode chamber, which contacts the inner silver/silver chloride electrode through a porous plug, and the sample through a second plug. The outer chamber filling solution provides a non-reacting solution in contact with the sample. For instance, in the measurement of chloride, a filling solution of potassium nitrate can be used in the outer electrode jacket.
The bifunctional role played by thiocyanate anions on the active dissolution and the passive film of titanium in hydrochloric acid
Published in Corrosion Engineering, Science and Technology, 2022
Ibrahim H. Elshamy, Sayed S. Abd El Rehim, Magdy A. M. Ibrahim, Nobl F. El Boraei
A cell of three electrodes was used for electrochemical studies. A Ti electrode was the working electrode (the Ti specimens were provided by Japan Coating Center Co. Ltd., Kanagawa, Japan). The working electrodes were built of 10 × 8 mm strips axially inserted in Araldite holders, resulting in a 1.6 cm2 exposed surface area. Before each experiment, the Ti electrode is mechanically varnished with different grades of emery sheets, such as 500, 800, and eventually 1200, before being washed with distilled H2O and acetone. Ultimately, in 1.0 M HF, the Ti electrode is activated for one minute before being carefully rinsed with double-distilled water [6]. An auxiliary electrode was a platinum electrode. A silver/silver chloride electrode was used as a reference electrode for all potential measurements. At 25°C, measurements were done with various HCl concentrations (2.0, 5.0, 8.0, 12.0, 18.0, and 20.0 wt-%) made from reagent grade HCl 37 wt-%. The electrochemical experiments were performed on a 1000 Gamry Instrument Potentiostat/Galvanstat/ZRA. The polarisation curves were investigated, in the voltage extent from −1.2 to +3.0 V with a 5 mVs−1 sweep rate.