Hg2Cl2/ platinum electrode

The redox potential is determined with a probe consisting of a platinum electrode and a Hg/Hg2Cl2 Cl or Ag/Ag Cl—Cl reference electrode. If Ep is the potential of the platinum probe, Ej the potential of the reference electrode and tne redox potential of the soil (in mV on the hydrogen scale) then... 

It is noteworthy that Scholz and coworkers [42] have studied electrochemical reduction of submicrometer size Hg2Cl2 and Flg2Br2 crystals immobilized on the surface of gold and platinum electrodes. The... 

The first in situ Raman spectroscopic study on electrochemical systems was reported on thin metal oxide and metal hahde film electrodes by Fleischmann etal. in 1973 [1]. The Raman spectroelectrochemi-cal measurements were made on thin films of Hg2Cl2, Hg2Br2, and HgO formed on droplets of mercury electrodeposited onto platinum electrodes. These mercury compounds have exceptionally high Raman scattering cross sections (very good Raman scatterers) so that the spectra of species as little as a few monolayers could be recorded on these high-surface-area electrodes. These experiments proved the viability of Raman spectroscopic measurements of... 

The first in-situ Raman spectroscopic study of an electrochemical system was reported in 1973 by Eleischmann, Hendra and McQuillan, who described Raman spectra for thin films of Hg2Cl2, Hg2Br2 and HgO, formed on mercury droplets that had been electrodeposited onto platinum electrodes [20]. As these compounds have exceptionally large Raman scattering cross-sections (i.e., they are very good Raman scatterers), a signal from a species composed of only a few monolayers could be detected. These experiments proved, for the first time, the viability of in-situ Raman spectroscopic measurements in electrochemical environments. 

In carrying out redox titrations, standard Ag/AgCl or Hg/Hg2Cl2 electrodes are used as a reference in conjunction with an inert redox electrode, e.g platinum, which takes its potential from the particular redox pair in the solution in which it is immersed. 

Reference electrode — Figure 2. Calomel reference electrode (1) platinum wire, (2) paste of mercury and Hg2Cl2, (3) liquid mercury, (4) KCl or NaCl solution... 

A reference electrode is needed to provide a potential scale for E° valnes as all voltages are relative. Any electrochemical reaction with a stable, well known potential can be nsed as a reference electrode. The NHE or standard hydrogen electrode (SHE) (Pt/H2,1.0 M H+) was the first well known reference electrode and is used as a reference in most tables of redox potentials. An NHE is difficult to construct and operate and therefore, is not typically used experimentally. Since the NHE is widely accepted, potentials are still often referenced to the NHE, converted from other reference electrodes. For aqueous solvents the SCE (Hg/Hg2Cl2 (KCl)) and the silver/silver chloride (Ag/AgCl) electrode are now commonly used as reference electrodes. To convert from the SCE to the NHE, E (vs. NHE) = E (vs. SCE) + 0.24 V. For nonaqueous solvents the silver/silver nitrate (Ag/AgNOs) reference electrode is often used. A pseudo-reference electrode can also serve as a reference point for aqueous or nonaqueous solutions. A silver or platinum wire can be used as a... 

Calomel Electrode. The normal hydrogen electrode [a platinum wire in 1.288 N HCl solution ( H+ = 1) with H2pressure bubbling through it] was used to define the standard electrode potential scale (see Section 7.3.2). This electrode is not convenient to use on an everyday basis, so a series of secondary reference electrodes has been developed for this purpose. One of the most commonly used laboratory reference electrodes is the saturated calomel electrode. The electrode (Fig. 7-36) consists of a platinum wire set in a paste that is a mixture of mercury (Hg(fj), mercurous chloride (calomel, HgaClajsj), and potassium chloride (KCl). The paste is in contact with a solution that is saturated with KCl and Hg2Cl2(s), The electrode can be represented as... 

Saturated calomel electrode An electrode that consists of a platinum wire in contact with a paste of liquid mercury and solid mercury(I) chloride, Hg2Cl2(s), all immersed in a saturated solution of potassium chloride, KCl often used as the reference electrode in a pH meter. 

The reference electrode, usually a saturated calomel electrode, consists of a platinum wire immersed in calomel (Hg2Cl2) paste, liquid Hg, and saturated KCl solution. 

In the three-electrode system, used in the current study, the examined metal takes the role of the active electrode. A calomel electrode, Hg/Hg2Cl2/KCl characterized by the potential +244 mV, was used as the reference electrode. Auxiliary electrode was made of platinum (Pt). The tests were carried out in the corrosive environment of 0.5M NaCl solution at pH = 7 and a temperature of 293K (Trzaska Trzaska, 2010). 

Figure 8.3 depicts a cell that has a hydrogen electrode on the left side and a calomel electrode on the right side. The calomel electrode contains liquid mercury in contact with solid calomel (Hg2Cl2). A platinum wire extends from the pool of mercury and acts as a terminal. The solution in this cell is an aqueous solution of HCl, just as in the cell of Figure 8.2. The reduction half-reaction at the calomel electrode is...

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