SCE saturated calomel electrode

The saturated calomel electrode (SCE), which is constructed using an aqueous solution saturated with KCl, has a potential at 25 °C of -hO.2444 V. A typical SCE is shown in Eigure 11.8 and consists of an inner tube, packed with a paste of Hg, HgiCli, and saturated KCl, situated within a second tube filled with a saturated solution of KCl. A small hole connects the two tubes, and an asbestos fiber serves as a salt bridge to the solution in which the SCE is immersed. The stopper in the outer tube may be removed when additional saturated KCl is needed. The shorthand notation for this cell is... 

The potentiostat has a three-electrode system a reference electrode, generally a saturated calomel electrode (SCE) a platinum counter, or amdliary, electrode through which current flows to complete the circuit and a working electrode that is a sample of interest (Fig. 25-10). The potentiostat is an instrument that allows control of the potential, either holding constant at a given potential, stepping from potential to potential, or changing the potential anodically or cathodically at some linear rate. 

V vs. SHE. Sometimes electrode potentials are referred to other reference electrodes, such as the saturated calomel electrode (SCE), etc. 

The electrolyte volume of the STM cells is usually very small (ofthe order of a 100 pi in the above-described case) and evaporation of the solution can create problems in long-term experiments. Miniature reference electrodes, mostly saturated calomel electrodes (SCE), have been described in the literature [25], although they are hardly used anymore in our laboratory for practical reasons Cleaning the glassware in caroic acid becomes cumbersome. For most studies, a simple Pt wire, immersed directly into solution, is a convenient, low-noise quasireference electrode. The Pt wire is readily cleaned by holding it into a Bunsen flame, and it provides a fairly constant reference potential of fcj>i — + 0.55 0.05 V versus SCE for 0.1 M sulfuric or perchloric acid solutions (+ 0.67 0.05 V for 0.1 M nitric acid), which has to be checked from time to time and for different solutions. 

Various carbon-based catalysts for the electrochemical oxygen reduction have been tested in the air gas-diffusion electrodes [7]. The polarization curves of the air electrodes were measured when operating against an inert electrode in 2 N NaCl-solution. The potential of the air electrodes was measured versus saturated calomel electrode (SCE). 

A schematic diagram of a typical pH electrode system is shown in Fig. 10.1. The cell potential, i.e. the electromotive force, is measured between a pH electrode and a reference electrode in a test solution. The pH electrode responds to the activity or concentration of hydrogen ions in the solution. The reference electrode has a very stable half-cell potential. The most commonly used reference electrodes for potentiometry are the silver/silver chloride electrodes (Ag/AgCl) and the saturated calomel electrodes (SCE). 

This method in some ways resembles the technique for ASV [321,322]. The analytical device is based on a three-electrode system (1) a glassy carbon electrode, which serves as a cathode (2) a saturated calomel electrode (SCE), which is the reference electrode and (3) a platinum counter-electrode during electrolysis. 

A different view of the OMT process is that the molecule, M, is fully reduced, M , or oxidized, M+, during the tunneling process [25, 26, 92-95]. In this picture a fully relaxed ion is formed in the junction. The absorption of a phonon (the creation of a vibrational excitation) then induces the ion to decay back to the neutral molecule with emission (or absorption) of an electron - which then completes tunneling through the barrier. For simplicity, the reduction case will be discussed in detail however, the oxidation arguments are similar. A transition of the type M + e —> M is conventionally described as formation of an electron affinity level. The most commonly used measure of condensed-phase electron affinity is the halfwave reduction potential measured in non-aqueous solvents, Ey2. Often these values are tabulated relative to the saturated calomel electrode (SCE). In order to correlate OMTS data with electrochemical potentials, we need them referenced to an electron in the vacuum state. That is, we need the potential for the half reaction ... 

The electrochemical experiments were conducted in an apparatus consisting of an electrochemical cell attached directly to a UHV system and has been described in detail elsewhere (16). The transfer between UHV and the EC was accomplished via a stainless steel air lock vented with ultra-pure Ar. Differentially pumped sliding teflon seals provided the isolation between UHV and atmospheric pressure. The sample was mounted on a polished stainless steel rod around which the teflon seals were compressed. All valves in the air lock were stainless steel gate valves with viton seals. Details of the electrochemical cell and conditions are contained in reference 16. Electrochemical potentials are referred to a saturated calomel electrode (SCE). 

The present conference paper provides a discussion of some representative findings from our recent studies on these topics, with the aim of comparing and contrasting some of the distinctive properties of SERS and IRRAS as applied to fundamental interfacial electrochemistry. We limit the presentation here to a brief overview further details can be found in the references cited. All electrode potentials quoted here are with respect to the saturated calomel electrode (SCE). 

The electrode potential was controlled with an EG G Princeton Applied Research (PAR) model 173 potentiostat/galvanostat and is referenced to a saturated calomel electrode (SCE). A PAR model 276 current-to-voltage converter allowed monitoring of current during the ORC and SERS experiments and it also provided for positive feedback iR compensation for accurate potential control. 

The SHE is experimentally inconvenient, so potentials are often measured and quoted with respect to reference electrodes other than the SHE. By far the most common reference is the saturated calomel electrode (SCE). We will usually make our choice of reference on the basis of experimental convenience. 

Additionally, other reference electrodes are used which are easier to maintain at standard conditions. These include the silver/silver chloride electrode and the saturated calomel electrode (SCE). The voltage difference between the working electrode and the reference electrode is proportional to the electrochemical potential difference between them. This is written... 

Most recently, Jenekhe and coworkers [174] synthesized PPV copolymers with quinoxa-line as pendants 144 and 145, as well as a part of the chain (not shown here). These polymers showed reductions with onsets of —1.70 and —1.75 V vs. saturated calomel electrode (SCE),... 

Saturable dye absorber, 14 677 Saturated aqueous salt solution, 9 34 Saturated calomel electrode (SCE), 9 571 Saturated fatty acids, 10 829, 830 Saturated hydrocarbons adsorbent affinity, 1 674 adsorption by zeolites, 1 624 fluorine reactivity with, 11 831 isomerization of, 12 172—173 Saturated polyester resins, based on trimethylpentanediol, 12 673 Saturated polyesters, 10 7 Saturated synthetic rubber, 10 705 Saturation and coating processes, 10 12-13 Saturation bonding, 17 509-510 Saturation color, 19 262 Saturation concentration, 15 677 Saturation index... 

Saturated calomel electrode (SCE) is another type of reference system of widespread use. The redox process for this electrode is... 

The counter-electrode (CE) was a 40 at.% RuC>2 (the remainder being Ti oxide) electrode, having more than 100 times the apparent surface area of the WE. It was positioned inside a Teflon tube to minimise the amount of hydrogen gas that could be released into the cell solution. An Ag/AgCl electrode was employed as the reference electrode (RE) at high temperatures, while a saturated calomel electrode (SCE) generally served as the RE at room temperature. 

In electroanalytical chemistry, the unchanging reference is a half-cell that, at a given temperature, has an unchanging potential. There are two designs for this half-cell that are popular—the saturated calomel electrode (SCE) and the silver-silver chloride electrode. These are described below. 

A counter electrode of constant potential is obtained making use of a half-cell system in which the components are present in concentrations so high as to be appreciably unaffected by a flow of current through it. The saturated calomel electrode (SCE) is the most common example of such an electrode. As shown in Figure 7, it is comprised of a mercury pool in contact with solid mercury(I) chloride and potassium chloride that lie at the bottom of the KC1 saturated solution. The aqueous solution is thus saturated with Hgl+, K+ and Cl- ions, the concentrations of which are governed by the solubility of the respective salts. 

Figure 7 Schematic representation of the Saturated Calomel Electrode (SCE)...

This type of counter electrode is defined as a reference electrode. As we will see in Chapter 3, Section 1.2, at 25° C the saturated calomel electrode (SCE) has a potential of +0.2415 V with respect to the standard hydrogen electrode (NHE), which, although difficult to use, is the internationally accepted standard for the potential scale, having conventionally E° — 0.000 V. 

Compounds 52, 53, 57, 58, and 69-72 were measured in 10% aqueous acetonitrile with 0.2 M BU4NBF4 as supporting electrolyte. All other compounds were measured in dichloromethane with 0.2 M BU4NBF4 as supporting electrolyte. A platinum electrode or a platinum gauze basket were the working electrode and all potentials are reported against the saturated calomel electrode (SCE) with a reference potential of 0.0 V. Values of for 57, 58, 70, 72, and 78 are actually values of E the reversible peak potential. All other values of are irreversible peak potentials. 

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